COVER PHOTOGRAPHS: Left: Yaak River near Troy, Montana (site 216). Photograph by Laverne G. Sultz,

 U.S. Geological Survey, taken September 20, 2001.

Top middle: Missouri River at Virgelle, Montana (site 88). Photograph by 

 Don A. Bischoff, U.S. Geological Survey, taken July 28, 1999.

Right: Tongue River at State line, near Decker, Montana (site 186). Photograph by 

 Timothy J. Morgan, U.S. Geological Survey, taken October 15, 2003.
Statistical Summaries of Streamflow in 

Montana and Adjacent Areas, 

Water Years 1900 through 2002

By Peter M. McCarthy

U.S. Department of the Interior

U.S. Geological Survey

In cooperation with the

Montana Department of Environmental Quality, 

Confederated Salish and Kootenai Tribes, and

Bureau of Land Management

Scientific Investigations Report 2004-5266
U.S. Department of the Interior

Gale A. Norton, Secretary

U.S. Geological Survey

Charles G. Groat, Director

U.S. Geological Survey, Reston, Virginia: 2005

For sale by U.S. Geological Survey, Information Services

Box 25286, Denver Federal Center

Denver, CO 80225

For additional information write to:

District Chief

U.S. Geological Survey

3162 Bozeman Avenue

Helena, Montana 59601

For more information about the USGS and its products:

Telephone: 1-888-ASK-USGS

World Wide Web: http://www.usgs.gov/

Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply 

endorsement by the U.S. Government.

Although this report is in the public domain, permission must be secured from the individual copyright owners to 

reproduce any copyrighted materials contained within this report.

Suggested citation:

McCarthy, P.M., 2005, Statistical summaries of streamflow in Montana and adjacent areas, water years 1900 through 

2002: U.S. Geological Survey Scientific Investigations Report 2004-5266, 317 p.
 iii

Contents

Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1

Purpose and Scope. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Site Selection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Methods of Creating the Statistical Summaries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2

Annual and Seasonal Low-Flow Frequencies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Annual High-Flow Frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Flow Duration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Monthly and Annual Mean Discharges. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Statistical Summaries of Streamflow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13

Selected References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .315

Figure

1. Map showing location of selected streamflow-gaging stations. . . . . . . . . . . . . . . . . . . . . . 3

Table

1. Selected streamflow-gaging stations in Montana and adjacent areas and

period of record used in study . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Conversion Factors, Datum, Symbols, Acronyms, 

and Abbreviations

Multiply By To obtain

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

acre 4,047 square meter (m2)

acre 0.4047 hectare (ha)

acre 0.004047 square kilometer (km2)

acre-foot (acre-ft) 1,233 cubic meter (m3)

square mile (mi2) 259.0 hectare (ha)

cubic foot per second (ft3/s) 0.02832 cubic meter per second (m3/s)

acre-foot per month (acre-ft/mon) 102.75 cubic meter per month (m3/mon)
iv 

Vertical coordinate information (this report) in the United States is referenced to the National 

Geodetic Vertical Datum of 1929 (NGVD 29). Horizontal coordinate information (this report) in the 

United States is referenced to the North American Datum of 1927 (NAD 27).

Water year: The 12-month period October 1 through September 30. It is designated by the 

calendar year in which it ends.

River mile: The distance along the meandering path of the stream channel. River mile is 

typically used to denote location along a river, in miles upstream from the mouth of the river 

(U.S. Geological Survey, 2002c, p. 57).

Symbols used in this report:

% percent

-- value not determined

Acronyms and abbreviations used in this report:

ADAPS Automated Data Processing System

FAS Federal-Aid Secondary Highway System, which is composed of the principal

secondary and feeder routes including farm-to-market roads, rural-mail and 

public-school bus routes, local-rural roads, county and township roads, and 

county roads. 

IOWDM Input and Output for Watershed Data Management

Lat latitude

Long longitude

(M) Abbreviation for revised instantaneous maximum discharge.

(P) Abbreviation for revised supplementary peak discharge (maximum for the year 

might or might not have been revised, but at least one lesser peak discharge was 

revised).

SWSTAT Surface-Water Statistics computer program

USGS U.S. Geological Survey

WDR-MT Water-Data Report, in REVISED RECORDS paragraphs refers to the U.S. 

Geological Survey Montana State annual data report. The next two numbers are 

the water year of the report. The last number is the volume number. “WRD” was 

used as an abbreviation in reports published before 1976.

WSP Water-Supply Paper, which is a series of U.S. Geological Survey publications. 

The next 3 to 4 numbers are the Water-Supply Paper number, which occasionally 

contains a chapter letter (for example, WSP 1320-B).
Statistical Summaries of Streamflow in Montana and 

Adjacent Areas, Water Years 1900 through 2002

By Peter M. McCarthy

Abstract

 In response to the need to have more current information 

about streamflow characteristics in Montana, the U.S. Geological Survey, in cooperation with the Montana Department of 

Environmental Quality, Confederated Salish and Kootenai 

Tribes, and Bureau of Land Management, conducted a study to 

analyze streamflow data. Updated statistical summaries of 

streamflow characteristics are presented for 286 streamflowgaging sites in Montana and adjacent areas having 10 or more 

years of record for water years 1900 through 2002. Data 

include the magnitude and probability of annual low and high 

flow, the magnitude and probability of low flow for three seasons (March-June, July-October, and November-February), 

flow duration of the daily mean discharge, and the monthly and 

annual mean discharges. For streamflow-gaging stations where 

20 percent or more of the contributing drainage basin is affected 

by dams or other large-scale human modification, streamflow is 

considered regulated. Separate streamflow characteristics are 

presented for the unregulated and regulated periods of record 

for sites with sufficient data.

Introduction

Information about streamflow characteristics is essential 

for development and management of surface-water resources. 

Water and land-use managers, planners, administrators, 

builders, engineers, recreationists, and the general public use 

information on all aspects of streamflow to evaluate various 

water conditions and land-use alternatives.

Annual low-flow and seasonal streamflow characteristics 

and annual high-flow streamflow characteristics are particularly important for characterizing streamflow variability. Lowflow frequency data for annual and seasonal periods indicate 

how frequently small values of discharge might occur and are 

used for assessing the capability of streams to receive and 

assimilate treated wastewater, developing wastewater permits, 

determining total maximum daily loads of streams, and assessing aquatic habitat. Annual high-flow frequency data, in conjunction with flood-frequency data (Parrett and Johnson, 2004), 

indicate how frequently large values of discharge might occur 

and are useful for effective flood planning and for safe and 

economical design of highway bridges, culverts, dams, levees, 

and other structures on or near streams.

The U.S. Geological Survey (USGS) has previously published reports that describe and document streamflow characteristics at streamflow-gaging stations in Montana (Shields and 

White, 1981; Waltemeyer and Shields, 1982; and Omang, 

1984). Two of these reports were based on data through 1979, 

and one used data through 1982. Since the completion of these 

reports, nearly 20 years of additional data have become available, and many new gages have been installed which now have 

10 or more years of streamflow records. In response to the need 

to have more current information about streamflow characteristics in Montana, the USGS, in cooperation with the Montana 

Department of Environmental Quality, Confederated Salish and 

Kootenai Tribes, and Bureau of Land Management, conducted 

a study to analyze streamflow data from 286 sites having at least 

10 years of streamflow record.

Purpose and Scope

The purpose of this report is to provide statistical summaries of streamflow characteristics at selected sites in Montana 

and adjacent areas for water years 1900 through 2002. Data 

include the magnitude and probability of annual low and high 

flow, the magnitude and probability of low flow for three seasons (March-June, July-October, and November-February), 

flow duration of the daily mean discharge, and the monthly and 

annual mean discharges. For streamflow-gaging stations where 

20 percent or more of the contributing drainage basin is affected 

by dams or other large-scale human modification, streamflow is 

considered regulated. Separate streamflow-characteristics data 

are presented for the unregulated and regulated periods of 

record for sites with sufficient data.

Site Selection

The sites selected for analysis are shown in figure 1 and 

described in table 1. A total of 286 streamflow-gaging stations 

were selected—269 of these stations are in Montana, 3 are at or 

near the international boundary between the United States and 

Canada, 2 are in Alberta, 2 are in British Columbia, 1 is in 

Idaho, and 9 are in Yellowstone National Park, Wyoming. Of 

the 286 sites, data for 224 stations were analyzed for periods of 
2 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

unregulated flow only, data for 47 stations were analyzed for 

periods of regulated flow only, and data for 15 stations were 

analyzed for separate periods of unregulated and regulated flow 

(fig. 1). For clarity in table 1 and figure 1, stations were 

assigned site numbers 1 through 286. The period of record by 

type of streamflow condition is listed in table 1. Of the 224 sites 

where data were analyzed for periods of unregulated flow only, 

8 stations were analyzed for periods before regulation only, and 

the remaining 216 stations were analyzed for the entire period 

of record for unregulated flows.

The statistical summaries provided for periods of unregulated flow might differ from summaries provided for periods of 

regulated flow. Typically these differences are the result of 

changes in regulation. However, differences in statistical summaries also might be the result of different climatic conditions 

rather than difference in regulation.

Methods of Creating the Statistical 

Summaries

The tables of statistical summaries of streamflow are preceded by a station description which typically includes station 

location, drainage area, period of record (by water years or by 

month and year), revised records, gage information, and 

remarks. The period of record included in the station descriptions might not include all years in which data were recorded at 

the station, and thus, might not coincide with the period of 

record used for analysis (table 1). Information about the number of years, seasons, or months used for analysis are included 

in the table headings. Remarks include information on the history of regulating structures, if any, and comments on the other 

factors that may affect flow. Remarks are based on information 

available at the time the stations were in operation, and thus, 

might not represent streamflow conditions in 2002. However, 

the latitude and longitude for stations that were discontinued 

before about 1960 have been updated (2004).

Daily mean streamflow values for each station were 

retrieved using the computer program Automated Data Processing System (ADAPS) (U. S. Geological Survey, 2003) and processed using the computer program Input and Output for Watershed Data Management (IOWDM) (U.S. Geological Survey, 

2002a). High- and low-flow frequency data, monthly and 

annual-flow characteristics, and flow-duration data were then 

computed using the computer program Surface-Water Statistics 

(SWSTAT) (U.S. Geological Survey, 2000b). 

Annual and Seasonal Low-Flow Frequencies

 Annual low-flow frequency data are developed from 

annual series of the lowest mean discharges for specified consecutive n-day periods within a climatic year. For example, an 

annual series of 7-day low flows consists of the lowest mean 

discharge that occurred over any 7-day consecutive period 

during each year of record. Seasonal low-flow frequency data 

are developed from annual series of the lowest mean discharges 

for each of the spring (March through June), summer (July 

through September), and winter (October through February) 

seasons for specified consecutive n-day periods within a climatic year. The periods selected for spring, summer, and winter 

were based on consultations with the Montana Department of 

Environmental Quality (Tom Reid, Montana Department of 

Environmental Quality, oral commun., 2002) and reflect typical 

runoff and irrigation patterns in Montana. 

The Pearson Type III probability distribution was used to 

estimate annual and seasonal low-flow frequency data (U.S. 

Geological Survey, 2002b). The Pearson Type III distribution 

is a three-parameter distribution, commonly applied to the base 

10 logarithms of streamflow data, that requires estimates of the 

logarithms of the population mean, the standard deviation, and 

the skew coefficient to determine streamflow magnitude for 

various non-exceedance or exceedance probabilities. For lowflow frequency, the population values are assumed to be equal 

to the values computed from the station record, and streamflow 

magnitudes are determined for non-exceedance probabilities.

The annual low-flow frequency data indicate the lowest 

mean discharges for consecutive periods of 1, 3, 7, 14, 30, 60, 

90, 120, and 183 days and for non-exceedance probabilities of 

50, 20, 10, 5, 2, and 1 percent. The non-exceedance probability 

(in decimal form before conversion to percent) associated with 

a low flow is the reciprocal of the recurrence interval, in years. 

The seasonal low-flow frequency data indicate lowest mean 

discharges for consecutive periods of 1, 3, 7, 14, and 30 days for 

non-exceedance probabilities of 50, 20, 10, 5, 2, and 1 percent.

Each value of discharge in the annual and seasonal lowflow tables is a mean low flow within the year or season for a 

consecutive n-day period that can be expected to be lower, on 

average, once in any specified recurrence interval (every y

years). Similarly, each value of discharge in the low-flow 

tables has a specified (x-percent) non-exceedance probability 

that, in any given year, a smaller value n-day mean low-flow 

value will occur. For example, the low-flow value for a consecutive 7-day period and the 2-year recurrence interval can be 

expected to be lower, on average, once every 2 years. Similarly, 

a low flow for a consecutive 7-day period and 50-percent nonexceedance probability has a 50-percent chance of being lower 

in any given year.

For any n-day period, discharges decrease with increasing 

recurrence interval and decreasing non-exceedance probability. 

Conversely, for any given recurrence interval or non-exceedance probability, discharge increases with increasing n-day 

periods. Seasonal and annual low-flow frequency data are only 

reported in the tables for recurrence intervals of twice the period 

of record or less (Parrett, 1997). For example, if the period of 

record is 10 years, only low-flow data for recurrence intervals 

of 20 years or less were presented. The symbol “--” is shown 

in the tables for recurrence intervals more than twice the period 

of record. Seasonal low-flow data commonly include more 

years of record than the annual low-flow data; thus, because of 

partial-record years the seasonal low-flow frequency data might 

be shown for longer recurrence intervals than the annual lowflow frequency data. 
Base modified from U.S. Geological Survey

State base map, 1968. North American Datum

of 1927 (NAD 27)

Cr

Fork

Two

Redwater

River

South Fork

River

Yaak

River

Kootenai

River

Clark

Fork Flathead Lake

Flathead

River

Middle

Cut Bank

Creek

Medicine

River Marias

River

Birch

Milk

River

Lodge

Creek

Battle Creek

Frenchman River

Milk

River

Poplar

River

Missouri

River

Medicine Lake

River

Fort PeckReservoir

Big

Dry

Creek

Boxelder

Creek

River

Judith

Missouri

River

Sun River

Smith River

River

Teton

River

Swan

Flathead

R

oot Bitterr River

Blackfoot

River

Creek

Rock

Clark

Fork

Musselshell

River

Yellowstone

Powder

River

River

Tongue

Bighorn

River

Bighorn Lake

Little Bighorn River

Yellowstone

Boulder River

Clarks k For

Gallatin

River

Madison

River

Ruby

River

River

Jefferson

R

Beaverhead

Big

Hole

River

Yellowstone Lake

Glendive

Sidney

Havre

Shelby

Great

 Falls

Lewistown

Miles City

Billings

Butte

Dillon

Malta

CANADA

UNITED STATES

Wyoming

YELLOWSTONE

NATIONAL

PARK

DIVIDE

CONTINENTAL

DIVIDE

Dearborn

River

Glasgow

 LakeKoocanusa

Troy

Libby

Hamilton

Ashland

Broadus

Hardin

Livingston

Big Timber

Mosby

Jordan

Pryor

Harlowton

0 10 20 30 40 50 MILES

0 10 20 30 50 KILOMETERS 40

116o

115o

113

49o

48o

47o

46o

45o

o

EXPLANATION

STATISTICAL SUMMARIES PROVIDED FOR INDICATED STREAMFLOW-GAGINGSTATION AND SITE NUMBER--Corresponds  to list of surface-water sites, table 1

114 o

Kalispell

Helena

Missoula

CONTINENTAL

Bozeman

7

6

93

88

72

40

13

10

274

267

213

202

194

179

169

115

Separate periods of regulated and unregulated 

 streamflow record

169

9

5

84

82

69 62

59

48

36

35

32 31

27

21

17

16

15 12

247

209

193

191

189

187

182

136

128 126

125

123

121

116

110

109

266

Regulated streamflow period of record only 31

33

281

279

130

8

98 97 96 95

94

92 91

90

89

87 86

85

83

81

80

79

78

77

76 75

74 73

71

70

68

67

66

65

64

63

61 60

58

57 56

55

54 53

52

51

50 49

47

46

45 44

43

42

41

39

38

37

34

30

29

28

26 25

24

23

22

20

19

18

14

11

286

285 284

283

282

280 278

277

276

275

273

272

271

270 265

264

263

262

261

258

255

254

253

252

251

250

249

248

246

245

244

242

241 240

239

238

237

236

235

234

233

232

231

230

229

228

227

226

225

224 223 222

221

220 219

218

216

215

214

212

210

205

204

203

201

200

199 198

197

196

195

192

190

188

186

185

184

183

181 180

178

177

176

175

172

171

170

168

167

166

165

164

163

162

161

160

159

158

157

156

155

154

153

152

150

151

149

148 147

146

145

144

143142 141 140 139 138

137

135

134

133

132

131

129

127

124

122

120

119

118

117

114

113

112

111

108

107

106 105

104

103

102

101

100

99

4

3

2

1

269

268

259 257

256

217

211

208 207

206

260

243

174

173

112o 111o 110o 109o 108o 107o 106o 105o

Idaho

South Dakota

th Dakota r No

Unregulated streamflow period of record only 158

Creek

Armells

Saskatchewan Alberta

British

Columbia

Montana

Methods of Creating the Statistical Summaries 3

Figure 1. Location of selected streamflow-gaging stations.
4 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

Annual low flows are calculated based on a climatic year 

(March 1 to February 28); thus, the period of record for a 

climatic year generally is identified as one year less than for a 

water year. This climatic year—chosen to coincide with the 

spring, summer, and winter periods previously determined for 

Montana—is slightly different from the April 1-March 31 

climatic year typically used for low-flow frequency analysis 

(Riggs, 1972). Differences in annual low-flow frequency 

resulting from the use of the two different climatic years were 

generally considered negligible because low flows in Montana 

commonly occur from late summer through winter. The program determines non-exceedance probability using only nonzero values of discharges and then uses a conditional adjustment probability to adjust the non-exceedance probability for 

zero flows in the record. 

Data for given n-day periods were computed independently for the annual and seasonal low-flow frequency tables. 

The presence of days with zero flow in the independent analyses 

resulted in some discharge values that did not consistently 

decrease with increasing recurrence interval or some discharge 

values for a given recurrence interval that did not consistently 

increase with increasing n-day period. These computed values 

were manually adjusted to produce consistent tabular results. In 

some instances, the computed seasonal low-flow values for a 

given n-day period and recurrence interval were less than the 

computed annual low-flow values. In these instances, seasonal 

low-flow values were manually increased to match the annual 

low-flow values.

Annual High-Flow Frequency

Annual high-flow frequency data are developed from 

annual series of the highest mean discharges for specified consecutive n-day consecutive periods within a water year. For 

example, an annual series of 3-day high flows consists of the 

highest mean discharge that occurs over any 3-day consecutive 

period during each year of record.

The Pearson Type III probability distribution was used to 

estimate high-flow frequency data (U.S. Geological Survey, 

2002b). The Pearson Type III distribution is a three-parameter 

distribution, commonly applied to the base 10 logarithms of 

streamflow data, that requires estimates of the logarithms of the 

population mean, the standard deviation, and the skew coefficient. For high-flow frequency, the population values are 

assumed to be equal to the values computed from the station 

record, and streamflow magnitudes are determined for exceedance probabilities. 

The annual high-flow frequency data indicate the highest 

mean discharges for consecutive periods of 1, 3, 7, 15, 30, 60, 

and 90 days. Results from the log Pearson Type III analyses are 

shown in the annual high-flow frequency table for recurrence 

intervals of 2, 5, 10, 25, 50, and 100 years. The table also 

presents exceedance probabilities of 50, 20, 10, 4, 2, and 

1 percent, respectively. Exceedance probability (in decimal 

form, before conversion to percent) is the reciprocal of the 

recurrence interval, in years.

Each value of discharge in the annual high-flow table is the 

mean high flow within the year for a consecutive n-day period 

that can be expected to be exceeded, on average, once in any 

specified recurrence interval (every y years). Similarly, each 

value of discharge in the high-flow table has a specified 

x-percent probability of exceedance in any given year. For 

example, the high-flow value corresponding to the 3-day 

consecutive period and 100-year recurrence interval can be 

expected to be exceeded, on average, once every 100 years. 

Similarly, a high flow for a consecutive 3-day period and 

1-percent exceedance probability has a 1-percent chance of 

being exceeded in any given year. 

For any n-day period, discharges increase with increasing 

recurrence interval and decreasing exceedance probability. 

Conversely, for any given recurrence interval or exceedance 

probability, discharge decreases with increasing n-day periods. 

High-flow frequency data only were reported for recurrence 

intervals of twice the period of record or less (Parrett, 1997). 

For example, if the period of record is 25 years, the table shows 

high-flow data for recurrence intervals of 50 years or less. The 

symbol “--” is shown in the tables for recurrence intervals more 

than twice the period of record. 

Flow Duration

Flow-duration data are developed from daily mean discharge values over the entire period of record, and the flowduration tables are developed from these data (Searcy, 1959). 

The flow-duration data are not related to the sequence of flow 

events, but do include the full range of daily mean discharges at 

the station. For example, the discharge value on a flow-duration 

table that corresponds to a 10-percent exceedance is the value 

that was exceeded by 10 percent of the flow record without 

regard to when those days of exceedance occurred. The days of 

exceedance might not have been consecutive and might have 

occurred either in a single year or during several years (Ludwig, 

1992).

Monthly and Annual Mean Discharges

The monthly and annual mean discharge tables show, for 

the period of record, the maximum and minimum mean values, 

the mean, the standard deviation from the mean, and the number 

of years of record. Data from this table are an indicator of the 

flow distribution throughout the year. The annual mean discharge tabulations for the period of record are based on a water 

year. 
Table 1. Selected streamflow-gaging stations in Montana and adjacent areas and period of record used in study.

[All stations are in Montana, except as indicated. Eight-digit station-identification numbers for routine surface-water sites represent the standard U.S. Geological 

Survey numbering systems for streamflow-gaging stations, wherein the first two digits indicate the major river basin and the remaining 6 digits indicate a downstream station order. Period of record is abbreviated to show only the first and last water years of data used. Abbreviations: U, unregulated or less than 20 percent 

of drainage area is regulated; R, regulated]

Site 

number

(fig. 1)

Station 

number Station name Streamflow condition

Period of 

record for 

analysis

(water year)1

05011000 Belly River near Mountain View, Alberta U 1912-78

05013700 St. Mary River above Swiftcurrent Creek, near Babb U 1902-15

05014000 Grinnell Creek near Many Glacier U 1949-78

05014500 Swiftcurrent Creek at Many Glacier U 1912-2002

05017500 St. Mary River near Babb R 1919-2002

05020500 St. Mary River at international boundary U 1902-16

R 1917-2002

06012500 Red Rock River below Lima Reservoir, near Monida R 1940-2002

06013500 Big Sheep Creek below Muddy Creek, near Dell U 1936-80

06015400 Beaverhead River near Grant R 1963-84

06016000 Beaverhead River at Barretts U 1908-63

R 1964-2002

06017500 Blacktail Deer Creek near Dillon U 1946-66

06018000 Beaverhead River near Dillon R 1964-84

06018500 Beaverhead River near Twin Bridges U 1935-63

R 1964-2002

06019500 Ruby River above reservoir, near Alder U 1938-2002

06020600 Ruby River below reservoir, near Alder R 1963-2002

06021500 Ruby River at Laurin R 1946-61

06023000 Ruby River near Twin Bridges R 1940-81

06024590 Wise River near Wise River U 1972-85

06025500 Big Hole River near Melrose U 1924-2002

06026000 Birch Creek near Glen U 1946-77

06026500 Jefferson River near Twin Bridges R 1964-2002

06027000 Jefferson River near Silver Star U 1910-39

06033000 Boulder River near Boulder U 1929-2002

06034500 Jefferson River at Sappington U 1900-63

06035000 Willow Creek near Harrison U 1938-2002

06036500 Willow Creek near Willow Creek U 1919-33

06036650 Jefferson River near Three Forks R 1979-2002

06036905 Firehole River near West Yellowstone U 1984-2002

06037000 Gibbon River near West Yellowstone U 1913-96

Table 1 5

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29
6 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

Table 1. Selected streamflow-gaging stations in Montana and adjacent areas and period of record used in study.—Continued

Site 

number

(fig. 1)

Station 

number Station name Streamflow condition

Period of 

record for 

analysis

(water year)1

30 06037500 Madison River near West Yellowstone U 1913-2002

31 06038500 Madison River below Hebgen Lake, near Grayling R 1939-2002

32 06038800 Madison River at Kirby Ranch, near Cameron R 1959-2002

33 06040000 Madison River near Cameron R 1952-71

34 06040300 Jack Creek near Ennis U 1973-92

35 06041000 Madison River below Ennis Lake, near McAllister R 1939-2002

36 06042500 Madison River near Three Forks R 1929-50

37 06043500 Gallatin River near Gallatin Gateway U 1930-2002

38 06048000 East Gallatin River at Bozeman U 1939-61

39 06048500 Bridger Creek near Bozeman U 1946-87

40 06050000 Hyalite Creek at Hyalite Ranger Station, near Bozeman U 1900-51

R 1952-95

41 06052500 Gallatin River at Logan U 1900-2002

42 06054500 Missouri River at Toston U2 1911-2002

43 06055500 Crow Creek near Radersburg U 1901-90

44 06061500 Prickly Pear Creek near Clancy U 1908-2002

45 06062500 Tenmile Creek near Rimini U 1915-2002

46 06063000 Tenmile Creek near Helena U 1908-54

47 06065500 Missouri River below Hauser Dam, near Helena U2 1924-42

48 06066500 Missouri River below Holter Dam, near Wolf Creek R 1953-2002

49 06068500 Little Prickly Pear Creek near Marysville U 1913-33

50 06071000 Little Prickly Pear Creek near Canyon Creek U 1909-25

51 06071300 Little Prickly Pear Creek at Wolf Creek U 1962-2002

52 06073000 Dearborn River near Clemons U 1921-53

53 06073500 Dearborn River near Craig U 1946-2002

54 06074000 Missouri River at Cascade U2 1902-15

55 06074500 Smith River near White Sulphur Springs U 1923-36

56 06076690 Smith River near Fort Logan U 1978-96

57 06077000 Sheep Creek near White Sulphur Springs U 1941-73

58 06077500 Smith River near Eden U 1951-70

59 06078200 Missouri River near Ulm R 1957-2002

60 06078500 North Fork Sun River near Augusta U 1911-93

61 06080000 Sun River near Augusta U 1904-29

62 06080900 Sun River below diversion dam, near Augusta R 1968-81

63 06081500 Willow Creek near Augusta U 1905-25
Table 1 7

64 06084500 Elk Creek at Augusta U 1905-25

65 06085800 Sun River at Simms R 1966-2002

66 06086000 Sun River at Fort Shaw U 1912-28

67 06088300 Muddy Creek near Vaughn U 1968-2002

68 06088500 Muddy Creek at Vaughn U 1925-2002

69 06089000 Sun River near Vaughn R 1934-2002

70 06090300 Missouri River near Great Falls R 1953-2002

71 06090500 Belt Creek near Monarch U 1951-83

72 06090800 Missouri River at Fort Benton U 1900-52

R 1953-2002

73 06091700 Two Medicine River below South Fork, near Browning R 1977-2002

74 06092000 Two Medicine River near Browning U 1907-77

75 06092500 Badger Creek near Browning U 1951-80

76 06093200 Badger Creek below Four Horns Canal, near Browning U 1974-2002

77 06093500 Badger Creek near Family U 1907-25

78 06098000 Dupuyer Creek near Valier U 1912-37

79 06098500 Cut Bank Creek near Browning U 1918-2002

80 06099000 Cut Bank Creek at Cut Bank U 1905-2002

81 06099500 Marias River near Shelby U 1902-2002

82 06101500 Marias River near Chester R 1956-2002

83 06102000 Marias River near Brinkman U 1922-55

84 06102050 Marias River near Loma R 1960-2002

85 06106000 Deep Creek near Choteau U 1911-25

86 06108000 Teton River near Dutton U 1954-2002

87 06109000 Missouri River at Loma U 1935-50

88 06109500 Missouri River at Virgelle U 1935-52

R 1953-2002

89 06109800 South Fork Judith River near Utica U 1958-79

90 06110000 Judith River near Utica U 1920-76

91 06111000 Ross Fork Creek near Hobson U 1946-62

92 06111500 Big Spring Creek near Lewistown U 1932-57

93 06115200 Missouri River near Landusky U 1934-52

R 1953-2002

94 06115500 North Fork Musselshell River near Delpine U 1940-80

95 06118500 South Fork Musselshell River above Martinsdale U 1942-80

Table 1. Selected streamflow-gaging stations in Montana and adjacent areas and period of record used in study.—Continued

Site 

number

(fig. 1)

Station 

number Station name Streamflow condition

Period of 

record for 

analysis

(water year)1
8 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

96 06120500 Musselshell River at Harlowton U 1907-2002

97 06122000 American Fork below Lebo Creek, near Harlowton U 1946-67

98 06123500 Musselshell River near Ryegate U 1946-80

99 06125700 Big Coulee Creek near Lavina U 1957-72

100 06126470 Halfbreed Creek near Klein U 1978-91

101 06126500 Musselshell River near Roundup U 1946-2002

102 06127500 Musselshell River at Musselshell U 1928-2002

103 06127900 Flatwillow Creek near Flatwillow U 1911-56

104 06128200 Flatwillow Creek near Winnett U 1921-51

105 06129000 Box Elder Creek near Winnett U 1930-72

106 06129500 McDonald Creek at Winnett U 1930-56

107 06130500 Musselshell River at Mosby U 1929-2002

108 06131000 Big Dry Creek near Van Norman U 1940-2002

109 06132000 Missouri River below Fort Peck Dam, at Fort Peck R 1945-2002

110 06134500 Milk River at Milk River, Alberta R 1917-2002

111 06137400 Big Sandy Creek at reservation boundary, near Rocky Boy U 1982-2002

112 06137570 Boxelder Creek near Rocky Boy U 1976-97

113 06137580 Sage Creek near Whitlash U 1977-90

114 06138500 Big Sandy Creek near Box Elder U 1927-39

115 06140500 Milk River at Havre U 1900-16

R 1917-2002

116 06154100 Milk River near Harlem R 1960-2002

117 06154400 Peoples Creek near Hays U 1967-2002

118 06154410 Little Peoples Creek near Hays U 1972-2002

119 06154430 Lodge Pole Creek at Lodge Pole U 1987-2001

120 06154550 Peoples Creek below Kuhr Coulee, near Dodson U 1918-2002

121 06155030 Milk River near Dodson R 1982-2002

122 06155500 Milk River at Malta U 1902-16

123 06164510 Milk River at Juneberg Bridge, near Saco R 1978-2002

124 06169500 Rock Creek below Horse Creek, near international boundary U 1916-2002

125 06172000 Milk River near Vandalia R 1917-87

126 06174500 Milk River at Nashua R 1940-2002

127 06176500 Wolf Creek near Wolf Point U 1908-92

128 06177000 Missouri River near Wolf Point R 1945-2002

129 06177500 Redwater River at Circle U 1929-2002

Table 1. Selected streamflow-gaging stations in Montana and adjacent areas and period of record used in study.—Continued

Site 

number

(fig. 1)

Station 

number Station name Streamflow condition

Period of 

record for 

analysis

(water year)1
Table 1 9

130 06178500 East Poplar River at international boundary R 1976-2002

131 06181000 Poplar River near Poplar U 1908-2002

132 06182500 Big Muddy Creek at Daleview U 1947-72

133 06183450 Big Muddy Creek near Antelope U 1979-2002

134 06185000 Big Muddy Creek near Culbertson U 1908-22

135 06185110 Big Muddy Creek near mouth, near Culbertson R 1982-92

136 06185500 Missouri River near Culbertson R 1941-2002

137 06186500 Yellowstone River at Yellowstone Lake outlet, Yellowstone National Park, Wyo. U 1927-2002

138 06187500 Tower Creek at Tower Falls, Yellowstone National Park, Wyo. U 1922-43

139 06187950 Soda Butte Creek near Lamar Ranger Station, Yellowstone National Park, Wyo. U 1989-2002

140 06188000 Lamar River near Tower Falls Ranger Station, Yellowstone National Park, Wyo. U 1923-2002

141 06189000 Blacktail Deer Creek near Mammoth, Yellowstone National Park, Wyo. U 1938-93

142 06190500 Gardner River at Mammoth, Yellowstone National Park, Wyo. U 1922-39

143 06191000 Gardner River near Mammoth, Yellowstone National Park, Wyo. U 1939-2002

144 06191500 Yellowstone River at Corwin Springs U 1910-2002

145 06192500 Yellowstone River near Livingston U 1900-2002

146 06193000 Shields River near Wilsall U 1935-57

147 06193500 Shields River at Clyde Park U 1921-67

148 06194000 Brackett Creek near Clyde Park U 1921-57

149 06195600 Shields River near Livingston U 1979-2002

150 06197000 Big Timber Creek near Big Timber U 1912-24

151 06197500 Boulder River near Contact U 1910-84

152 06200000 Boulder River at Big Timber U 1947-2002

153 06200500 Sweet Grass Creek above Melville U 1913-69

154 06201000 Sweet Grass Creek below Melville U 1907-52

155 06202510 Stillwater River above Nye Creek, near Nye U 1980-91

156 06204050 West Rosebud Creek near Roscoe R 1965-2002

157 06204500 Rosebud Creek near Absarokee U 1935-70

158 06205000 Stillwater River near Absarokee U 1910-2002

159 06207500 Clarks Fork Yellowstone River near Belfry U 1921-2002

160 06208500 Clarks Fork Yellowstone River at Edgar U 1921-2002

161 06208800 Clarks Fork Yellowstone River near Silesia U 1970-87

162 06209500 Rock Creek near Red Lodge U 1932-2002

163 06212500 Red Lodge Creek below Cooney Reservoir, near Boyd R 1938-2002

164 06214500 Yellowstone River at Billings U 1904-2002

Table 1. Selected streamflow-gaging stations in Montana and adjacent areas and period of record used in study.—Continued

Site 

number

(fig. 1)

Station 

number Station name Streamflow condition

Period of 

record for 

analysis

(water year)1
10 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

165 06216000 Pryor Creek at Pryor U 1921-2002

166 06216500 Pryor Creek near Billings U 1911-54

167 06216900 Pryor Creek near Huntley U 1979-2001

168 06217750 Fly Creek at Pompeys Pillar U 1969-81

169 06287000 Bighorn River near St. Xavier U 1935-64

R 1965-2002

170 06287500 Soap Creek near St. Xavier U 1911-73

171 06288500 Bighorn River near Hardin U 1904-33

172 06289000 Little Bighorn River at State line, near Wyola U 1939-2002

173 06290000 Pass Creek near Wyola U 1935-2002

174 06290500 Little Bighorn River below Pass Creek, near Wyola U 1939-2002

175 06291000 Owl Creek near Lodge Grass U 1939-92

176 06291500 Lodge Grass Creek above Willow Creek Diversion, near Wyola U 1939-2002

177 06293500 Little Bighorn River near Crow Agency U 1912-60

178 06294000 Little Bighorn River near Hardin U 1953-2002

179 06294500 Bighorn River above Tullock Creek, near Bighorn U 1945-64

R 1965-2002

180 06294940 Sarpy Creek near Hysham U 1973-84

181 06294995 Armells Creek near Forsyth U 1974-95

182 06295000 Yellowstone River at Forsyth R 1977-2002

183 06295113 Rosebud Creek at reservation boundary, near Kirby U 1980-2002

184 06295250 Rosebud Creek near Colstrip U 1975-2002

185 06296003 Rosebud Creek at mouth, near Rosebud U 1975-2002

186 06306300 Tongue River at State line, near Decker U 1960-2002

187 06307500 Tongue River at Tongue River Dam, near Decker R 1939-2002

188 06307600 Hanging Woman Creek near Birney U 1973-95

189 06307616 Tongue River at Birney Day School Bridge, near Birney R 1980-2002

190 06307740 Otter Creek at Ashland U 1973-95

191 06307830 Tongue River below Brandenberg Bridge, near Ashland R 1974-2002

192 06308400 Pumpkin Creek near Miles City U 1973-86

193 06308500 Tongue River at Miles City R 1938-2002

194 06309000 Yellowstone River at Miles City U 1922-65

R 1966-2002

195 06324500 Powder River at Moorhead U 1929-2002

196 06325500 Little Powder River near Broadus U 1947-72

Table 1. Selected streamflow-gaging stations in Montana and adjacent areas and period of record used in study.—Continued

Site 

number

(fig. 1)

Station 

number Station name Streamflow condition

Period of 

record for 

analysis

(water year)1
Table 1 11

197 06326300 Mizpah Creek near Mizpah U 1975-86

198 06326500 Powder River near Locate U 1938-2002

199 06326600 O'Fallon Creek near Ismay U 1977-92

200 06327500 Yellowstone River at Glendive U 1900-34

201 06329200 Burns Creek near Savage U 1958-86

202 06329500 Yellowstone River near Sidney U 1911-65

R 1966-2002

203 06334000 Little Missouri River near Alzada U 1911-69

204 06334630 Box Elder Creek at Webster U 1961-73

205 06336500 Beaver Creek at Wibaux U 1938-84

206 12300000 Kootenay River at Newgate, British Columbia U 1931-72

207 12301300 Tobacco River near Eureka U 1959-2002

208 12301500 Kootenai River near Rexford U 1929-71

209 12301933 Kootenai River below Libby Dam, near Libby R 1973-2002

210 12302000 Fisher River near Jennings U 1951-70

211 12302055 Fisher River near Libby U 1968-2002

212 12302500 Granite Creek near Libby U 1933-70

213 12303000 Kootenai River at Libby U 1911-72

R 1973-91

214 12303100 Flower Creek near Libby U 1960-93

215 12303500 Lake Creek at Troy U 1945-96

216 12304500 Yaak River near Troy U 1956-2002

217 12305000 Kootenai River at Leonia, Idaho U 1929-71

218 12323240 Blacktail Creek at Butte U 1989-2002

219 12323250 Silver Bow Creek below Blacktail Creek, at Butte U 1984-2002

220 12323500 German Gulch Creek near Ramsay U 1955-69

221 12323600 Silver Bow Creek at Opportunity U 1988-2002

222 12323750 Silver Bow Creek at Warm Springs R 1972-2002

223 12323770 Warm Springs Creek at Warm Springs U 1984-2002

224 12323800 Clark Fork near Galen U 1988-2002

225 12324100 Racetrack Creek below Granite Creek, near Anaconda U 1957-73

226 12324200 Clark Fork at Deer Lodge U 1979-2002

227 12324590 Little Blackfoot River near Garrison U 1972-2002

228 12324680 Clark Fork at Goldcreek U 1977-2002

229 12325500 Flint Creek near Southern Cross R 1941-2002

Table 1. Selected streamflow-gaging stations in Montana and adjacent areas and period of record used in study.—Continued

Site 

number

(fig. 1)

Station 

number Station name Streamflow condition

Period of 

record for 

analysis

(water year)1
12 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

230 12329500 Flint Creek at Maxville U 1941-2002

231 12330000 Boulder Creek at Maxville U 1939-2002

232 12331500 Flint Creek near Drummond U 1948-2002

233 12331600 Clark Fork at Drummond U 1973-83

234 12331900 Clark Fork near Clinton U 1979-94

235 12332000 Middle Fork Rock Creek near Philipsburg U 1938-2002

236 12334510 Rock Creek near Clinton U 1973-2002

237 12334550 Clark Fork at Turah Bridge, near Bonner U 1985-2002

238 12335000 Blackfoot River near Helmville U 1941-54

239 12335500 Nevada Creek above reservoir, near Helmville U 1939-2002

240 12338500 Blackfoot River near Ovando U 1940-63

241 12339450 Clearwater River near Clearwater U 1975-92

242 12340000 Blackfoot River near Bonner U 1900-2002

243 12340500 Clark Fork above Missoula U 1929-2002

244 12342500 West Fork Bitterroot River near Conner R 1941-2002

245 12343400 East Fork Bitterroot River near Conner U 1956-2002

246 12343500 East Fork Bitterroot River at Conner U 1910-57

247 12344000 Bitterroot River near Darby R 1941-2002

248 12346500 Skalkaho Creek near Hamilton U 1949-2002

249 12347500 Blodgett Creek near Corvallis U 1947-69

250 12350000 Bear Creek near Victor U 1938-59

251 12351000 Burnt Fork Bitterroot River near Stevensville U 1920-62

252 12352500 Bitterroot River near Missoula U 1900-2002

253 12353000 Clark Fork below Missoula U 1930-2002

254 12354000 St. Regis River near St. Regis U 1910-2002

255 12354500 Clark Fork at St. Regis U 1911-2002

256 12355000 Flathead River at Flathead, British Columbia U 1929-2002

257 12355500 North Fork Flathead River near Columbia Falls U 1911-2002

258 12357000 Middle Fork Flathead River at Essex U 1940-64

259 12357500 Middle Fork Flathead River at West Glacier U 1911-48

260 12358500 Middle Fork Flathead River near West Glacier U 1940-2002

261 12359000 South Fork Flathead River at Spotted Bear Ranger Station, near Hungry Horse U 1948-67

262 12359800 South Fork Flathead River above Twin Creek, near Hungry Horse U 1965-2002

263 12360000 Twin Creek near Hungry Horse U 1948-67

264 12361000 Sullivan Creek near Hungry Horse U 1949-77

Table 1. Selected streamflow-gaging stations in Montana and adjacent areas and period of record used in study.—Continued

Site 

number

(fig. 1)

Station 

number Station name Streamflow condition

Period of 

record for 

analysis

(water year)1
Statistical Summaries of Streamflow 13

265 12361500 Graves Creek near Hungry Horse U 1948-67

266 12362500 South Fork Flathead River near Columbia Falls R 1952-99

267 12363000 Flathead River at Columbia Falls U 1922-51

R 1952-2002

268 12365000 Stillwater River near Whitefish U 1931-2002

269 12366000 Whitefish River near Kalispell U 1928-2002

270 12367500 Ashley Creek near Kalispell U 1931-74

271 12369200 Swan River near Condon U 1973-92

272 12370000 Swan River near Bigfork U 1922-2002

273 12371100 Hell Roaring Creek near Polson U 1917-37

274 12372000 Flathead River near Polson U 1907-51

R 1952-2002

275 12374250 Mill Creek above Bassoo Creek, near Niarada U 1982-2002

276 12375900 South Crow Creek near Ronan U 1982-2002

277 12377150 Mission Creek above reservoir, near St. Ignatius U 1982-2002

278 12381400 South Fork Jocko River near Arlee U 1982-2002

279 12383500 Big Knife Creek near Arlee U 1910-2002

280 12388200 Jocko River at Dixon U 1990-2002

281 12388400 Revais Creek below West Fork, near Dixon U 1983-2002

282 12388700 Flathead River at Perma U 1984-2002

283 12389000 Clark Fork near Plains U 1911-2002

284 12389500 Thompson River near Thompson Falls U 1911-2002

285 12390700 Prospect Creek at Thompson Falls U 1956-2002

286 12391400 Clark Fork below Noxon Rapids Dam, near Noxon U 1960-2002 1

1Number of years used for analysis are occasionally more than the total number of years in the period of record. See section “Statistical Summaries of 

Streamflow” of this report. 

2Dam or powerplant upstream from station considered to have minimal effect on streamflow.

Table 1. Selected streamflow-gaging stations in Montana and adjacent areas and period of record used in study.—Continued

Site 

number

(fig. 1)

Station 

number Station name Streamflow condition

Period of 

record for 

analysis

(water year)1

Statistical Summaries of Streamflow

Station descriptions provided in the following tables are 

based on data available at the time each station was in operation 

and may not accurately reflect streamflow conditions in 2002 or 

reporting standards. The period of record included in the station 

descriptions might not include all years in which data were 

recorded at the station, and thus, might not coincide with the 

period of record used for analysis (table 1). For example, the 

station description for Big Sheep Creek below Muddy Creek, 

near Dell (station 06013500, site number 8) indicates that the 

last year of record was 1979. However, daily flow record was 

collected at this site for several days in water year 1980, and that 

record was used for determination of the duration of the daily 

mean flows at this site. Accordingly, the period of record for 

analysis presented in table 1 shows the last year of record 

collection at this station to be 1980. 
14 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

05011000 Belly River near Mountain View, Alberta

(International gaging station)

Site Number 1

LOCATION.--Lat 49°06'00", long 113°41'48" (NAD 27), in NE1⁄4 sec.5, T.2, R.28 W., fourth meridian, in Alberta, Hydrologic Unit 10010001, on right bank 2 mi 

downstream from intake of Mountain View Irrigation District Canal, 5 mi southwest of Mountain View, and 7 mi north of international boundary.

DRAINAGE AREA.--121 mi2.

PERIOD OF RECORD.--November 1911 to September 1978 (discontinued). Monthly discharge only for some periods, published in WSP 1308.

GAGE.--Water-stage recorder. Altitude of gage is 4,342.88 ft (datum unknown; Greg MacCulloch, Environment Canada, written commun., 2004). November 

1911, to Apr. 6, 1949, nonrecording gage at site 20 ft upstream at same datum. Apr. 7, 1949, to June 19, 1975, water-stage recorder at present site at datum 

2.02 ft higher.

REMARKS.--Natural flow of stream affected by diversion to Mountain View Irrigation District Canal 2 mi upstream from station.

Magnitude and probability of annual low flow

based on 66 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 31 21 17 14 11 9.0

3 33 23 19 16 13 11

7 35 26 22 19 16 14

14 40 31 27 24 20 18

30 47 38 33 29 25 22

60 60 47 41 36 31 27

90 69 52 45 40 34 31

120 81 61 53 47 41 37

183 110 82 72 64 56 52

Magnitude and probability of seasonal low flow from

March-June based on 67 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 43 31 25 21 17 14

3 45 33 27 23 19 16

7 47 35 29 25 21 18

14 50 38 33 29 26 24

30 59 45 39 36 33 31

Magnitude and probability of seasonal low flow from

November-February based on 66 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 36 24 19 15 12 9.7

3 38 27 21 17 14 12

7 41 30 25 21 17 15

14 45 34 29 26 22 20

30 52 40 35 31 27 24

Duration of daily mean flows based on 66 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

26 32 41 50 64 83 107 141

40% 30% 20% 15% 10% 5% 2% 1%

196 303 497 664 892 1,230 1,620 1,970

Magnitude and probability of annual high flow

based on 66 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 1,720 2,710 3,630 5,200 6,730 8,650

3 1,670 2,490 3,180 4,220 5,140 6,200

7 1,540 2,160 2,580 3,110 3,520 3,930

15 1,400 1,870 2,140 2,430 2,610 2,780

30 1,240 1,600 1,780 1,960 2,070 2,160

60 1,050 1,300 1,420 1,530 1,600 1,640

90 868 1,070 1,160 1,240 1,290 1,330

Magnitude and probability of seasonal low flow from

July-October based on 66 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 85 50 37 28 20 16

3 88 54 41 33 25 20

7 93 59 47 38 30 25

14 100 67 55 46 38 34

30 115 81 69 61 53 49

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 488 46 178 103 66

November 437 41 128 62 67

December 288 27 86 36 67

January 192 25 68 27 67

February 203 26 68 35 67

March 213 29 69 32 67

April 715 61 207 116 67

May 1,300 334 786 194 67

June 2,450 340 1,120 417 67

July 1,280 141 603 241 67

August 521 117 260 91 67

September 514 77 177 92 67

Annual 504 146 314 72 66
Statistical Summaries of Streamflow 15

05013700 St. Mary River above Swiftcurrent Creek, near Babb, Mont.

Site Number 2

LOCATION.--Lat 48°51'00", long 113°24'50" (NAD 27), in NE1⁄4 sec.27, T.36 N, R.14 W., Glacier County, 0.5 mi downstream from Lower St. Mary Lake, 1 mi 

southeast of Babb, and 2 mi upstream from Swiftcurrent Creek.

DRAINAGE AREA.--173 mi2. 

PERIOD OF RECORD.--13 years (1902-15). Published as "near St. Mary" 1902-04, and as "near Babb" 1905-15.

GAGE.--Chain gage. Altitude of gage is 4,460 ft (NGVD 29, from topographic map).

REMARKS.--No regulation or diversion.

Magnitude and probability of annual low flow

based on 13 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 47 27 15 8.4 -- --

3 51 36 30 27 -- --

7 53 38 33 29 -- --

14 59 44 38 34 -- --

30 65 50 44 40 -- --

60 77 61 54 48 -- --

90 102 74 61 52 -- --

120 135 92 75 62 -- --

183 214 169 150 137 -- --

Magnitude and probability of seasonal low flow from

March-June based on 14 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 72 45 34 28 -- --

3 73 45 36 29 -- --

7 75 47 37 30 -- --

14 78 52 42 36 -- --

30 91 65 55 48 -- --

Magnitude and probability of seasonal low flow from

November-February based on 13 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 58 33 18 9.4 -- --

3 60 43 36 31 -- --

7 62 46 39 34 -- --

14 66 49 42 36 -- --

30 70 54 47 41 -- --

Duration of daily mean flows based on 13 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

38 45 56 71 95 131 193 281

40% 30% 20% 15% 10% 5% 2% 1%

418 618 910 1,130 1,450 2,000 2,790 3,430

Magnitude and probability of annual high flow

based on 13 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 2,290 3,600 4,810 6,840 -- --

3 2,250 3,530 4,710 6,670 -- --

7 2,180 3,310 4,280 5,810 -- --

15 2,070 3,010 3,740 4,800 -- --

30 1,910 2,630 3,130 3,800 -- --

60 1,620 2,090 2,400 2,780 -- --

90 1,370 1,730 1,960 2,250 -- --

Magnitude and probability of seasonal low flow from

July-October based on 13 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 199 154 138 127 -- --

3 203 157 140 128 -- --

7 213 163 143 129 -- --

14 222 180 165 156 -- --

30 254 208 192 183 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 646 174 345 148 13

November 666 81 269 161 13

December 305 54 148 78 13

January 120 45 82 23 14

February 140 40 86 27 14

March 190 50 104 44 14

April 519 129 230 119 14

May 1,730 479 1,000 311 14

June 3,400 1,060 1,980 742 14

July 2,160 793 1,300 447 14

August 894 364 633 154 14

September 694 255 406 140 14

Annual 754 388 540 117 13
16 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

05014000 Grinnell Creek near Many Glacier, Mont.

Site Number 3

LOCATION.--Lat 48°46'14", long 113°41'53" (NAD 27), in SE1⁄4 sec.21, T.35 N., R.16 W., (unsurveyed), Glacier National Park, Hydrologic Unit 10010002, on 

right bank 600 ft upstream from trail crossing, 900 ft downstream from Grinnell Lake, 0.3 mi upstream from mouth, 2.6 mi southwest of Many Glacier, and 

13.5 mi southwest of Babb.

DRAINAGE AREA.--3.32 mi2. 

PERIOD OF RECORD.--30 years. August 1949 to September 1978 (discontinued). No winter record since 1976.

GAGE.--Water-stage recorder. Altitude of gage is 4,920 ft ( NGVD 29, from topographic map). Prior to Oct. 12, 1949, nonrecording gages at various sites and 

datums.

REMARKS.--No regulation or diversion. After 1964, some inflow from Cataract Creek has entered upstream from gage during highwater periods in 

some years.

Magnitude and probability of annual low flow

based on 26 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.44 0.29 0.24 0.20 0.17 --

3 .47 .30 .24 .21 .17 --

7 .54 .34 .28 .23 .20 --

14 .68 .45 .37 .31 .27 --

30 .99 .68 .57 .50 .43 --

60 1.6 1.1 .88 .75 .63 --

90 2.5 1.6 1.3 1.1 .87 --

120 3.8 2.6 2.2 1.9 1.6 --

183 9.1 7.2 6.4 5.8 5.1 --

Magnitude and probability of seasonal low flow from

March-June based on 27 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.74 0.42 0.32 0.26 0.21 --

3 .79 .44 .33 .27 .21 --

7 .93 .49 .36 .28 .22 --

14 1.1 .61 .45 .35 .27 --

30 1.7 1.0 .78 .65 .53 --

Magnitude and probability of seasonal low flow from

November-February based on 27 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.60 0.33 0.25 0.20 0.18 --

3 .65 .35 .26 .21 .18 --

7 .72 .41 .32 .26 .21 --

14 .85 .52 .41 .35 .30 --

30 1.2 .74 .60 .51 .44 --

Duration of daily mean flows based on 27 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

0.15 0.31 0.77 1.3 2.5 4.0 6.4 12

40% 30% 20% 15% 10% 5% 2% 1%

21 34 50 61 76 97 125 151

Magnitude and probability of annual high flow

based on 27 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 159 214 259 326 385 --

3 140 185 221 275 322 --

7 121 155 179 213 239 --

15 109 134 150 171 186 --

30 96 116 129 146 158 --

60 83 97 105 115 121 --

90 72 81 87 93 98 --

Magnitude and probability of seasonal low flow from

July-October based on 28 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 5.4 3.8 3.1 2.6 2.1 --

3 5.8 4.1 3.4 2.8 2.2 --

7 6.7 4.7 3.9 3.2 2.6 --

14 8.4 5.8 4.7 3.8 3.0 --

30 12 8.3 6.7 5.6 4.6 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 41 5.0 15 8.5 29

November 19 .96 8.0 4.0 28

December 9.2 .87 3.8 2.1 28

January 13 .62 2.9 2.7 27

February 5.3 .63 2.2 1.5 27

March 7.9 .65 2.3 1.8 27

April 19 2.0 8.9 4.7 27

May 74 21 47 13 29

June 135 52 90 22 29

July 114 40 68 17 29

August 52 28 39 6.4 30

September 49 16 23 7.2 30

Annual 33 22 26 2.9 27
Statistical Summaries of Streamflow 17

05014500 Swiftcurrent Creek at Many Glacier, Mont.

(Hydrologic bench-mark station)

Site Number 4

LOCATION.--Lat 48°47'57", long 113°39'21" (NAD 27), in SE1⁄4 sec.11, T.35 N., R.16 W., Glacier County, Hydrologic Unit 10010002, Glacier National Park, 

on right bank 100 ft upstream from outlet of Swiftcurrent Lake at Many Glacier, and 11 mi southwest of Babb.

DRAINAGE AREA.--30.9 mi2.

PERIOD OF RECORD.--June 1912 to current year (2002; records incomplete most years prior to 1959). Published as "at McDermott Lake," 1912-14. Monthly 

discharge only for some periods, published in WSP 1308.

REVISED RECORDS.--WSP 1508: 1918(M), 1943. WDR MT-75-1: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 4,876.78 ft (NGVD 29). Prior to May 23, 1916, nonrecording gage on left bank of lake opposite present gage 

and at present datum, and May 23, 1916, to June 15, 1918, nonrecording gage at present site and datum.

REMARKS.--No regulation or diversion upstream from station. Bureau of Reclamation satellite telemeter at station. 

Magnitude and probability of annual low flow

based on 46 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 12 8.3 6.8 5.5 0.00 --

3 12 8.8 7.2 5.9 .00 --

7 13 9.4 7.7 6.5 5.3 --

14 14 11 9.1 7.9 6.8 --

30 17 12 11 9.4 8.0 --

60 22 16 13 11 9.8 --

90 27 19 16 14 12 --

120 34 24 20 17 15 --

183 50 37 32 28 24 --

Magnitude and probability of seasonal low flow from

March-June based on 58 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 15 11 8.9 7.7 6.7 6.1

3 16 11 9.2 8.1 7.0 6.4

7 17 12 9.9 8.7 7.6 7.0

14 19 13 11 9.6 8.4 7.7

30 24 16 13 12 10 9.1

Magnitude and probability of seasonal low flow from

November-February based on 47 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 13 9.2 7.6 6.4 0.00 --

3 14 9.8 8.1 6.8 .00 --

7 15 10 8.5 7.1 5.8 --

14 16 12 9.9 8.6 7.3 --

30 19 14 12 9.9 8.4 --

Duration of daily mean flows based on 46 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

11 12 16 21 31 46 64 88

40% 30% 20% 15% 10% 5% 2% 1%

124 182 284 357 459 618 753 933

Magnitude and probability of annual high flow

based on 46 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 909 1,280 1,640 2,240 2,820 --

3 830 1,090 1,310 1,620 1,900 --

7 723 906 1,030 1,180 1,300 --

15 632 770 853 949 1,020 --

30 556 658 711 765 800 --

60 459 536 577 622 651 --

90 383 439 467 495 513 --

Magnitude and probability of seasonal low flow from

July-October based on 88 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 36 25 20 17 14 12

3 38 26 21 18 15 13

7 41 28 23 19 16 14

14 45 31 25 21 17 15

30 54 37 31 26 22 20

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 243 20 84 53 88

November 237 13 72 50 53

December 100 14 37 21 49

January 177 10 33 28 48

February 68 6.9 27 14 47

March 96 9.7 30 18 59

April 340 17 104 53 67

May 656 205 377 85 88

June 822 193 490 140 91

July 519 114 261 93 90

August 207 57 117 33 90

September 236 32 86 44 90

Annual 184 86 141 23 46
18 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

05017500 St. Mary River near Babb, Mont.

Site Number 5

LOCATION.--Lat 48°50'00", long 113°25'08" (NAD 27), in NW1⁄4NW1⁄4SE1⁄4 sec.34, T.36 N., R.14 W., Glacier County, Hydrologic Unit 10010002, Blackfeet 

Indian Reservation, on right bank 0.7 mi upstream from outlet of Lower St. Mary Lake and 2.0 mi southeast of Babb.

DRAINAGE AREA.--276 mi2.

PERIOD OF RECORD.--July 1901 to October 1902, May 1910 to September 1925, October 1950 to current year (2002). Monthly discharge only for some periods, 

published in WSP 1308. Published as "at Main" in 1901-02, and as "below Swiftcurrent Creek, at Babb" 1910-15. Records published as "near Babb" for April 

1902 to September 1915, May 1929 to September 1950 at sites about 1.5 mi downstream not equivalent because flow of Swiftcurrent Creek not included 

1902-15 and because diversion by St. Mary Canal not included 1929-50.

REVISED RECORDS.--WSP 1308: 1913-14, 1920, 1922-24. WSP 1508: 1902.

GAGE.--Water-stage recorder. Altitude of gage is 4,468.13 ft (NGVD 29). Prior to Oct. 1, 1915, water-stage recorder or nonrecording gages at several sites about 

3.8 mi downstream at different datums. Oct. 1, 1915, to Sept. 30, 1925, water-stage recorder or nonrecording gages at several sites within 1.5 mi downstream 

at different datums.

REMARKS.--Entire flow of Swiftcurrent Creek below Lake Sherburne is diverted into Lower St. Mary Lake upstream from station. Flow of Swiftcurrent 

Creek regulated by Lake Sherburne (station number 05015500) since 1919. October 1950 to September 1976, monthly discharge and runoff figures 

adjusted for change in contents in Lake Sherburne. Bureau of Reclamation satellite telemeter at station. 

Magnitude and probability of annual low flow

based on 57 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 58 43 37 33 28 25

3 59 44 38 33 28 26

7 61 46 39 34 29 27

14 64 48 41 36 31 28

30 73 54 46 40 35 31

60 90 66 55 48 40 36

90 108 75 61 52 43 38

120 130 88 72 61 52 46

183 262 186 156 134 114 102

Magnitude and probability of seasonal low flow from

March-June based on 59 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 82 59 50 45 39 36

3 83 60 51 45 40 37

7 87 61 52 46 40 37

14 93 64 54 48 42 39

30 117 75 61 52 45 41

Magnitude and probability of seasonal low flow from

November-February based on 58 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 66 47 39 34 28 26

3 67 48 40 34 29 26

7 69 49 41 35 30 27

14 74 52 43 37 31 28

30 82 59 49 42 35 31

Duration of daily mean flows based on 59 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

42 49 63 77 106 144 212 351

40% 30% 20% 15% 10% 5% 2% 1%

691 996 1,340 1,560 1,980 2,680 3,570 4,120

Magnitude and probability of annual high flow

based on 59 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 3,480 5,090 6,470 8,650 10,600 13,000

3 3,450 4,910 6,070 7,750 9,200 10,800

7 3,270 4,490 5,360 6,520 7,440 8,400

15 2,960 3,930 4,570 5,370 5,970 6,570

30 2,630 3,360 3,810 4,360 4,740 5,120

60 2,230 2,740 3,050 3,410 3,670 3,910

90 1,930 2,310 2,520 2,770 2,940 3,100

Magnitude and probability of seasonal low flow from

July-October based on 59 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 165 101 78 63 50 43

3 169 103 80 64 51 44

7 178 107 82 66 52 45

14 195 114 87 70 56 48

30 270 155 116 91 70 58

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 1,320 67 377 258 60

November 1,280 45 257 223 60

December 722 34 152 110 59

January 302 37 113 52 59

February 249 34 109 48 59

March 457 39 155 103 59

April 977 85 460 236 59

May 2,570 670 1,660 435 60

June 4,810 1,290 2,500 757 60

July 2,700 687 1,590 442 60

August 1,410 320 994 213 60

September 1,290 119 694 304 60

Annual 1,070 442 758 138 59
Statistical Summaries of Streamflow 19

05020500 St. Mary River at international boundary

(International gaging station)

Site Number 6

LOCATION.--Lat 49°00'43", long 113°17'57" (NAD 27), in NE1⁄4 sec.5, T.1, R.25 W., fourth meridian, in Alberta, Hydrologic Unit 10010002, on left bank 1.0 mi 

north of international boundary, 3.6 mi downstream from Boundary Creek, 6.5 mi southwest of Kimball, Alberta, and 13 mi northeast of Babb, Mont.

DRAINAGE AREA.--465 mi2.

PERIOD OF RECORD.--September 1902 to current year (2002). Monthly discharge only for some periods, published in WSP 1308. Published as "near Cardston, 

Alberta," and "at Cook's Ranch, Alberta," 1902-12 and as "near Kimball, Alberta," 1913-55.

REVISED RECORDS.--WSP 1308: 1902, 1908-12. WSP 1508: 1902, 1908-09. WDR-MT-83-1: Drainage area.

GAGE.--Water-stage recorder. Datum of gage is 4,087.40 ft (NGVD 29) based upon levels from datum established at previous site 1.1 mi upstream by Prairie 

Farm Rehabilitation Administration. Prior to Jan. 1, 1913, nonrecording gages at two sites within 0.3 mi of previous site at different datums. Jan. 1, 1913, to 

Oct. 25, 1955, water-stage recorder at several sites about 7 mi downstream from present site at various datums. Oct. 26, 1955, to Mar. 23, 1965, water-stage 

recorder at site 200 ft upstream from previous site at datum 2 ft higher. Mar. 24, 1965, to Sept. 8, 1975, water-stage recorder at site 100 ft upstream from 

previous site at same datum. Water-stage recorder at site 1.1 mi upstream June 22, 1975, to Oct. 31, 1999.

REMARKS.--Since 1917, St. Mary Canal has diverted water from the river near Babb, Mont., to North Fork Milk River. Some regulation by Lake Sherburne on 

Swiftcurrent Creek. Bureau of Reclamation satellite telemeter at station.

Unregulated streamflow period

Magnitude and probability of annual low flow

based on 13 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 106 87 78 72 -- --

3 108 89 80 72 -- --

7 114 92 82 74 -- --

14 117 94 84 76 -- --

30 123 99 88 79 -- --

60 150 117 101 89 -- --

90 180 145 130 118 -- --

120 252 183 153 131 -- --

183 408 307 257 218 -- --

Magnitude and probability of seasonal low flow from

March-June based on 14 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 161 122 108 98 -- --

3 165 124 110 99 -- --

7 178 134 117 106 -- --

14 188 137 119 108 -- --

30 194 143 126 115 -- --

Magnitude and probability of seasonal low flow from

November-February based on 14 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 116 90 79 72 -- --

3 118 92 81 74 -- --

7 125 97 83 75 -- --

14 128 99 85 76 -- --

30 132 103 90 80 -- --

Duration of daily mean flows based on 14 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

83 96 117 147 202 259 393 537

40% 30% 20% 15% 10% 5% 2% 1%

749 1,100 1,580 2,020 2,570 3,420 4,910 5,740

Magnitude and probability of annual high flow

based on 14 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 4,000 7,140 10,900 19,000 -- --

3 3,910 6,840 10,200 17,300 -- --

7 3,840 6,360 8,940 13,700 -- --

15 3,710 5,660 7,340 10,000 -- --

30 3,470 4,930 6,030 7,580 -- --

60 2,940 3,870 4,500 5,320 -- --

90 2,500 3,200 3,680 4,310 -- --

Magnitude and probability of seasonal low flow from

July-October based on 13 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 380 282 233 196 -- --

3 394 290 238 199 -- --

7 410 299 243 201 -- --

14 429 314 259 218 -- --

30 502 367 306 261 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 1,040 221 630 225 14

November 1,100 130 476 246 14

December 438 157 242 78 14

January 224 90 153 38 14

February 377 75 164 74 14

March 516 120 229 114 14

April 1,190 304 617 221 14

May 2,480 1,220 1,910 331 14

June 7,500 2,240 3,680 1,590 14

July 3,460 1,180 2,140 719 14

August 1,460 580 1,030 261 14

September 1,380 371 724 306 15

Annual 1,350 646 1,000 226 14
20 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

05020500 St. Mary River at international boundary—Continued

(International gaging station)

Site Number 6

Regulated streamflow period

Magnitude and probability of annual low flow

based on 85 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 71 48 38 30 24 20

3 74 52 42 35 28 24

7 79 57 48 41 34 29

14 87 64 54 47 40 36

30 100 75 64 56 48 43

60 123 92 79 70 61 56

90 143 103 88 78 69 63

120 173 120 101 88 76 70

183 253 181 154 136 119 110

Magnitude and probability of seasonal low flow from

March-June based on 86 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 100 66 53 45 37 32

3 104 70 58 49 42 37

7 111 78 66 58 51 47

14 122 85 73 64 57 52

30 149 103 87 77 67 62

Magnitude and probability of seasonal low flow from

November-February based on 85 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 82 53 42 34 27 23

3 85 57 46 39 32 27

7 90 62 51 44 37 33

14 97 69 58 51 43 39

30 110 79 67 59 51 46

Duration of daily mean flows based on 85 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

55 67 84 105 143 185 254 344

40% 30% 20% 15% 10% 5% 2% 1%

465 654 1,000 1,300 1,770 2,630 3,790 4,510

Magnitude and probability of annual high flow

based on 85 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 3,610 5,710 7,320 9,610 11,500 13,600

3 3,520 5,490 6,930 8,900 10,500 12,100

7 3,270 4,950 6,090 7,560 8,660 9,770

15 2,900 4,280 5,160 6,250 7,030 7,780

30 2,510 3,600 4,280 5,100 5,680 6,230

60 2,040 2,850 3,360 3,970 4,400 4,810

90 1,680 2,300 2,690 3,160 3,500 3,830

Magnitude and probability of seasonal low flow from

July-October based on 85 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 198 127 100 81 64 54

3 205 135 108 90 74 64

7 219 148 121 103 86 76

14 242 164 134 113 94 83

30 288 198 163 139 117 104

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 1,590 88 423 267 86

November 1,420 80 319 241 86

December 844 64 197 120 86

January 729 56 155 98 86

February 411 42 149 71 86

March 512 55 182 102 86

April 1,330 136 447 244 86

May 3,560 678 1,640 622 86

June 5,940 694 2,430 1,180 86

July 3,030 496 1,200 573 86

August 1,060 246 531 161 86

September 1,510 153 449 255 85

Annual 1,280 316 675 212 85
Statistical Summaries of Streamflow 21

06012500 Red Rock River below Lima Reservoir, near Monida, Mont.

Site Number 7

LOCATION.--Lat 44°39'22", long 112°22'14" (NAD 27), in NE1⁄4SE1⁄4SE1⁄4 sec.31, T.13 S., R.6 W., Beaverhead County, Hydrologic Unit 10020001, on right bank 

just downstream from Lima Reservoir, 7 mi northwest of Monida, and at river mile 2,542.1.

DRAINAGE AREA.--570 mi2.

PERIOD OF RECORD.--January 1911 to December 1918, April 1919, May 1925 to October 1933, April 1934 to September 1935, May 1936 to October 1938, 

May 1939 to September 1969, seasonal records only June 1974 to September 1982 and April 1985 to current year (2002). Monthly discharge only for some 

periods, published in WSP 1309. Prior to October 1950, published as "below Red Rock Reservoir."

REVISED RECORDS.--WSP 1309: 1935. WSP 1389: 1912, 1934. WSP 1559: Drainage area.

GAGE.--Water-stage recorder and sharp-crested weir. Altitude of gage is 6,530 ft (NGVD 29), estimated from spillway elevation based on Montana Department 

of Natural Resources and Conservation datum. Prior to Oct. 1, 1978, at datum 1.00 ft higher. See WSP 1709 for history of nonrecording gage changes prior 

to May 8, 1939.

REMARKS.--Flow regulated by Lima Reservoir (station number 06012000). No storage during 1934. Diversions for irrigation of about 10,000 acres upstream 

from reservoir. Bureau of Reclamation satellite telemeter at station. 

Magnitude and probability of annual low flow

based on 27 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 11 3.9 0.00 0.00 0.00 --

3 12 5.6 .00 .00 .00 --

7 13 6.3 .00 .00 .00 --

14 13 7.3 1.6 .00 .00 --

30 14 8.1 4.1 .00 .00 --

60 18 12 9.8 8.0 6.2 --

90 21 14 12 9.8 8.1 --

120 22 15 13 11 9.1 --

183 50 28 20 14 9.8 --

Magnitude and probability of seasonal low flow from

March-June based on 28 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 17 6.0 0.00 0.00 0.00 --

3 18 6.4 .00 .00 .00 --

7 18 8.8 2.1 .00 .00 --

14 18 9.4 2.9 .00 .00 --

30 19 9.6 4.4 .00 .00 --

Magnitude and probability of seasonal low flow from

November-February based on 29 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 15 7.6 0.00 0.00 0.00 --

3 15 8.7 3.8 .00 .00 --

7 16 9.1 4.6 .00 .00 --

14 16 9.6 5.4 .00 .00 --

30 17 11 6.5 .00 .00 --

Duration of daily mean flows based on 31 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

0.26 0.51 5.7 12 19 25 33 67

40% 30% 20% 15% 10% 5% 2% 1%

183 269 354 410 483 595 704 740

Magnitude and probability of annual high flow

based on 31 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 541 646 702 763 803 --

3 536 640 697 760 800 --

7 527 631 688 751 791 --

15 504 606 661 722 762 --

30 469 564 615 671 708 --

60 415 502 552 611 651 --

90 370 446 489 537 569 --

Magnitude and probability of seasonal low flow from

July-October based on 51 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 16 4.3 0.00 0.00 0.00 0.00

3 20 6.6 .00 .00 .00 .00

7 30 7.8 .00 .00 .00 .00

14 33 8.7 1.8 .00 .00 .00

30 42 11 4.3 1.0 .00 .00

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 263 0.93 67 62 53

November 96 6.7 32 23 31

December 66 10 26 14 29

January 57 9.0 23 9.1 29

February 53 8.0 22 9.1 29

March 48 7.1 21 9.0 28

April 416 1.2 64 76 55

May 676 66 313 135 56

June 707 206 491 104 57

July 652 14 329 118 57

August 513 3.3 227 110 57

September 384 .57 156 104 56

Annual 262 67 147 44 31
22 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06013500 Big Sheep Creek below Muddy Creek, near Dell, Mont.

Site Number 8

LOCATION.--Lat 44°39'19", long 112°46'41" (NAD 27), in SW1⁄4NW1⁄4SE1⁄4 sec.35, T.13 S., R.10 W., Beaverhead County, Hydrologic Unit 10020001, on left 

bank 2.2 mi downstream from Muddy Creek, 6.5 mi southwest of Dell and 8.5 mi upstream from mouth. 

DRAINAGE AREA.--278 mi2. 

PERIOD OF RECORD.--Apri1 to September 1936, May 1946 to September 1953. Annual maximums and daily flows for water years 1961-76 on file in USGS 

Montana District Office. October 1976 to September 1979 (discontinued). Published as "Sheep Creek near Dell," 1936, and "Sheep Creek below Muddy Creek, 

near Dell," 1946-53, 1960-65. 

REVISED RECORDS.--WDR MT-75-1: Drainage area. 

GAGE.--Water-stage recorder. Altitude of gage is 6,390 ft (NGVD 29, from topographic map). Apr. 21 to Sept. 30, 1936, nonrecording gage at site about 3 mi 

downstream at different datum. 

REMARKS.--Diversions for irrigation of about 6,600 acres upstream from station.

Magnitude and probability of annual low flow

based on 25 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 35 31 28 27 25 --

3 36 31 29 28 26 --

7 36 32 30 29 27 --

14 37 33 31 29 28 --

30 38 34 32 30 29 --

60 41 36 33 32 30 --

90 44 38 35 33 30 --

120 48 41 37 34 30 --

183 52 44 39 36 32 --

Magnitude and probability of seasonal low flow from

March-June based on 26 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 37 33 32 31 30 --

3 38 33 32 31 30 --

7 39 34 32 31 30 --

14 40 34 33 31 30 --

30 43 36 33 32 30 --

Magnitude and probability of seasonal low flow from

November-February based on 26 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 37 33 30 29 27 --

3 38 33 31 30 28 --

7 38 34 32 31 29 --

14 39 35 33 31 30 --

30 40 35 34 32 31 --

Duration of daily mean flows based on 26 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

25 28 33 36 40 45 50 56

40% 30% 20% 15% 10% 5% 2% 1%

62 70 84 91 109 142 184 229

Magnitude and probability of annual high flow

based on 26 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 262 348 387 422 440 --

3 225 298 332 363 380 --

7 191 250 276 300 312 --

15 163 203 218 231 237 --

30 136 169 183 194 200 --

60 109 141 157 174 184 --

90 99 127 141 156 166 --

Magnitude and probability of seasonal low flow from

July-October based on 26 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 46 37 32 28 24 --

3 47 38 33 29 25 --

7 48 39 34 30 26 --

14 50 40 35 32 28 --

30 54 43 37 33 28 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 89 35 62 13 26

November 77 39 57 9.3 26

December 63 36 48 7.2 26

January 59 32 43 6.5 26

February 60 32 42 7.2 26

March 106 33 50 18 26

April 178 38 89 35 26

May 180 29 86 40 27

June 181 30 102 44 28

July 153 30 71 30 28

August 98 28 67 19 28

September 82 30 55 14 28

Annual 89 35 65 13 26
Statistical Summaries of Streamflow 23

06015400 Beaverhead River near Grant, Mont.

Site Number 9

LOCATION.--Lat 45°00'12", long 112°51'10" (NAD 27), in NW1⁄4SW1⁄4SE1⁄4 sec.32, T.9 S., R.10 W., Beaverhead County, Hydrologic Unit 10020002, on right 

bank 0.4 mi downstream from Clark Canyon Dam, 1.3 mi upstream from Clark Canyon Creek, 10.3 mi east of Grant, and at river mile 2,483.6. 

DRAINAGE AREA.--2,322 mi2. 

PERIOD OF RECORD.--September 1962 to September 1983 (discontinued). Prior to October 1968, published as "near Armstead." 

GAGE.--Water-stage recorder. Altitude of gage is 5,442.78 ft (NGVD 29, levels by U.S. Army Corps of Engineers). 

REMARKS.--Diversions for irrigation of about 76,500 acres upstream from station. Flow completely regulated by Clark Canyon Reservoir (station 

number 06015300). 

Magnitude and probability of annual low flow

based on 20 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 90 56 42 32 -- --

3 102 64 48 37 -- --

7 113 71 53 41 -- --

14 119 74 56 44 -- --

30 125 80 63 52 -- --

60 132 85 67 55 -- --

90 158 98 75 60 -- --

120 195 115 84 63 -- --

183 248 156 120 95 -- --

Magnitude and probability of seasonal low flow from

March-June based on 21 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 134 95 78 65 -- --

3 148 101 81 66 -- --

7 163 106 83 67 -- --

14 173 111 86 68 -- --

30 184 116 89 71 -- --

Magnitude and probability of seasonal low flow from

November-February based on 20 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 153 97 74 59 -- --

3 156 98 75 59 -- --

7 162 101 77 61 -- --

14 169 105 79 62 -- --

30 181 111 83 63 -- --

Duration of daily mean flows based on 21 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

56 67 80 102 158 214 255 315

40% 30% 20% 15% 10% 5% 2% 1%

389 501 650 731 847 984 1,070 1,090

Magnitude and probability of annual high flow

based on 21 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 1,000 1,130 1,190 1,250 -- --

3 980 1,110 1,170 1,230 -- --

7 958 1,090 1,160 1,230 -- --

15 916 1,060 1,130 1,210 -- --

30 856 994 1,070 1,150 -- --

60 754 895 975 1,060 -- --

90 712 850 923 1,000 -- --

Magnitude and probability of seasonal low flow from

July-October based on 20 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 116 61 43 33 -- --

3 140 74 51 37 -- --

7 174 89 60 42 -- --

14 191 98 66 46 -- --

30 229 132 99 77 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 616 79 286 168 21

November 529 53 284 160 21

December 497 54 255 127 21

January 446 49 213 96 21

February 373 76 224 91 21

March 441 75 213 102 21

April 803 73 280 201 21

May 946 99 492 245 21

June 980 114 686 200 21

July 938 345 672 160 21

August 1,220 268 669 226 21

September 1,000 98 417 227 21

Annual 579 173 392 107 21
24 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06016000 Beaverhead River at Barretts, Mont.

Site Number 10

LOCATION.--Lat 45°06'59", long 112°44'59" (NAD 27), in SE1⁄4SW1⁄4SE1⁄4 sec.19, T.8 S., R.9 W., Beaverhead County, Hydrologic Unit 10020002, on left bank 

1.4 mi upstream from Barretts, 2.2 mi downstream from Grasshopper Creek, 8.9 mi southwest of Dillon, and at river mile 2,469.2.

DRAINAGE AREA.--2,737 mi2.

PERIOD OF RECORD.--August 1907 to September 1986, October 1986 to current year (2002; seasonal records only). Monthly discharge only for some periods, 

published in WSP 1309. Prior to October 1963, published as "at Barratts."

REVISED RECORDS.--WSP 1729: 1908(M), 1910-12(M), 1929(M), 1935-36. WSP 1559: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 5,268.17 ft (NGVD 29). Prior to Oct. 19, 1934, nonrecording gages at same site and datum.

REMARKS.--Some regulation by Lima Reservoir (station number 06012000) and nearly complete regulation by Clark Canyon Reservoir (station number 

06015300) after August 1964. Diversions for irrigation of about 90,000 acres upstream from station. Bureau of Reclamation satellite telemeter at station. 

Unregulated streamflow period

Magnitude and probability of annual low flow

based on 55 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 186 134 111 93 77 67

3 188 137 114 97 80 70

7 194 142 118 101 83 73

14 204 149 124 105 86 75

30 222 160 132 111 90 78

60 244 174 142 118 95 81

90 262 186 151 125 99 84

120 290 204 164 135 106 89

183 313 225 183 152 122 104

Magnitude and probability of seasonal low flow from

March-June based on 56 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 217 158 131 112 93 82

3 221 161 135 115 96 84

7 231 170 143 122 101 89

14 245 182 153 132 111 99

30 281 208 175 151 126 111

Magnitude and probability of seasonal low flow from

November-February based on 55 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 241 177 143 117 91 75

3 243 181 149 124 98 83

7 248 189 159 135 111 96

14 256 199 170 147 123 109

30 270 214 184 161 136 121

Duration of daily mean flows based on 56 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

103 117 143 175 223 265 300 334

40% 30% 20% 15% 10% 5% 2% 1%

368 429 504 572 708 990 1,370 1,680

Magnitude and probability of annual high flow

based on 56 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 1,280 1,920 2,310 2,780 3,100 3,400

3 1,190 1,790 2,160 2,600 2,910 3,200

7 1,050 1,590 1,940 2,380 2,690 3,000

15 917 1,410 1,750 2,180 2,500 2,820

30 778 1,220 1,540 1,980 2,330 2,690

60 646 1,000 1,270 1,630 1,930 2,240

90 582 878 1,090 1,380 1,600 1,840

Magnitude and probability of seasonal low flow from

July-October based on 55 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 206 145 120 102 84 73

3 208 147 121 102 84 73

7 213 150 123 104 85 74

14 221 154 126 106 87 76

30 240 165 133 111 91 78

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 717 116 359 156 56

November 889 153 409 138 56

December 539 140 340 88 56

January 442 120 285 69 56

February 396 150 280 61 56

March 934 169 351 124 56

April 1,350 123 495 243 56

May 1,910 131 593 386 56

June 2,610 146 735 497 56

July 959 96 374 169 56

August 603 96 297 123 56

September 591 88 288 121 56

Annual 738 168 401 135 56
Statistical Summaries of Streamflow 25

06016000 Beaverhead River at Barretts, Mont.—Continued

Site Number 10

Regulated streamflow period

Magnitude and probability of annual low flow

based on 22 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 190 137 108 89 -- --

3 201 140 109 89 -- --

7 210 145 112 90 -- --

14 216 150 114 91 -- --

30 226 167 125 99 -- --

60 240 177 152 135 -- --

90 276 195 163 140 -- --

120 320 215 172 142 -- --

183 357 240 195 165 -- --

Magnitude and probability of seasonal low flow from

March-June based on 39 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 223 155 128 108 90 --

3 235 161 131 110 90 --

7 242 164 133 111 91 --

14 248 167 135 113 92 --

30 262 177 144 122 101 --

Magnitude and probability of seasonal low flow from

November-February based on 22 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 247 175 144 122 -- --

3 251 181 151 129 -- --

7 259 187 157 134 -- --

14 268 193 161 138 -- --

30 278 199 166 141 -- --

Duration of daily mean flows based on 23 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

97 108 136 167 233 298 359 439

40% 30% 20% 15% 10% 5% 2% 1%

530 661 811 915 1,020 1,190 1,440 1,690

Magnitude and probability of annual high flow

based on 23 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 1,220 1,560 1,820 2,190 -- --

3 1,200 1,530 1,790 2,170 -- --

7 1,160 1,480 1,730 2,090 -- --

15 1,100 1,410 1,640 1,970 -- --

30 1,030 1,310 1,530 1,840 -- --

60 926 1,180 1,380 1,660 -- --

90 873 1,110 1,300 1,570 -- --

Magnitude and probability of seasonal low flow from

July-October based on 37 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 215 137 108 90 72 --

3 228 141 110 90 72 --

7 246 146 112 90 73 --

14 257 151 114 91 74 --

30 288 167 126 99 76 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 1,090 82 357 229 38

November 806 138 408 202 23

December 685 133 360 156 23

January 547 127 312 115 23

February 514 132 314 104 23

March 654 111 293 139 39

April 1,100 126 371 219 39

May 1,220 224 648 241 39

June 2,180 482 906 308 39

July 2,150 463 845 298 39

August 1,930 341 702 311 39

September 1,640 76 433 313 39

Annual 1,100 293 538 162 23
26 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06017500 Blacktail Deer Creek near Dillon, Mont.

Site Number 11

LOCATION.--Lat 45°02'47", long 111°32'53" (NAD 27), in NE1⁄4SE1⁄4SW1⁄4 sec.14, T.9 S., R.8 W., Beaverhead County, on left bank 12.5 mi southeast of Dillon 

and 14 mi upstream from mouth.

DRAINAGE AREA.--312 mi2.

PERIOD OF RECORD.--18 years. April 1946 to December 1953, April 1955 to September 1966 (discontinued). Monthly discharge only for April 1946, published 

in WSP 1309. Prior to October 1960, published as "Blacktail Creek near Dillon."

GAGE.--Water-stage recorder. Altitude of gage is 5,667.59 ft (NGVD 29, levels by Bureau of Reclamation).

REMARKS.--Diversions for irrigation of about 4,000 acres upstream from station.

Magnitude and probability of annual low flow

based on 16 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 15 11 9.8 8.7 -- --

3 16 12 11 9.7 -- --

7 19 15 14 12 -- --

14 22 18 15 14 -- --

30 25 20 18 16 -- --

60 29 24 21 19 -- --

90 32 26 24 21 -- --

120 35 29 26 24 -- --

183 38 32 29 27 -- --

Magnitude and probability of seasonal low flow from

March-June based on 18 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 29 21 18 15 -- --

3 30 23 19 16 -- --

7 33 25 21 18 -- --

14 35 27 23 20 -- --

30 42 33 28 25 -- --

Magnitude and probability of seasonal low flow from

November-February based on 18 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 15 11 9.8 8.8 -- --

3 16 13 11 9.8 -- --

7 19 15 14 12 -- --

14 22 18 16 14 -- --

30 25 20 18 16 -- --

Duration of daily mean flows based on 18 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

14 17 22 26 32 37 41 46

40% 30% 20% 15% 10% 5% 2% 1%

53 60 69 81 95 127 178 217

Magnitude and probability of annual high flow

based on 18 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 175 264 328 413 -- --

3 163 243 301 377 -- --

7 151 221 270 334 -- --

15 139 200 242 297 -- --

30 125 177 213 259 -- --

60 104 141 163 191 -- --

90 91 119 136 155 -- --

Magnitude and probability of seasonal low flow from

July-October based on 19 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 35 27 23 20 -- --

3 36 27 23 20 -- --

7 37 29 25 22 -- --

14 38 30 26 23 -- --

30 41 32 29 26 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 68 26 46 11 19

November 52 26 42 8.1 19

December 52 22 33 7.4 19

January 43 16 30 5.7 18

February 51 16 33 10 18

March 63 24 43 11 18

April 78 37 56 13 20

May 132 39 80 27 20

June 237 50 128 52 20

July 109 34 70 23 20

August 72 25 47 13 20

September 62 28 45 10 20

Annual 76 35 54 11 18
Statistical Summaries of Streamflow 27

06018000 Beaverhead River near Dillon, Mont.

Site Number 12

LOCATION.--Lat 45°18'18", long 112°33'45" (NAD 27), in NW1⁄4NE1⁄4NE1⁄4 sec.22, T.6 S., R.8 W., Beaverhead County, Hydrologic Unit 10020002, on right 

bank just upstream from county road bridge on Anderson Lane, 7.0 mi northeast of Dillon and at river mile 2,444.1. 

DRAINAGE AREA.--3,484 mi2. 

PERIOD OF RECORD.--October 1950 to September 1952, August 1963 to Sept. 30, 1983 (discontinued). 

GAGE.--Water-stage recorder. Altitude of gage is 4,960 ft (NGVD 29, by barometer). Prior to August 1963, nonrecording gage on upstream side of bridge at 

same datum. 

REMARKS.--Flow partly regulated by Lima Reservoir (station number 06012000) and Clark Canyon Reservoir (station number 06015300) since August 1964. 

Diversions upstream from station for irrigation of about 133,400 acres of which about 5,000 acres are irrigated by imported water from Birch and Willow Creeks 

and of which about 17,100 acres lies downstream from station including about 600 acres in Ruby River drainage. 

Magnitude and probability of annual low flow

based on 19 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 72 37 26 19 -- --

3 76 41 29 22 -- --

7 85 50 38 30 -- --

14 101 62 49 40 -- --

30 125 81 66 56 -- --

60 166 107 84 69 -- --

90 184 120 96 80 -- --

120 204 132 105 87 -- --

183 250 165 132 109 -- --

Magnitude and probability of seasonal low flow from

March-June based on 20 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 90 48 32 23 -- --

3 96 53 38 28 -- --

7 111 66 49 39 -- --

14 134 84 65 53 -- --

30 163 105 85 72 -- --

Magnitude and probability of seasonal low flow from

November-February based on 19 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 325 213 161 124 -- --

3 331 222 172 135 -- --

7 340 240 193 159 -- --

14 354 263 221 189 -- --

30 368 280 239 208 -- --

Duration of daily mean flows based on 20 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

53 66 90 125 191 243 297 353

40% 30% 20% 15% 10% 5% 2% 1%

414 480 563 629 696 773 993 1,070

Magnitude and probability of annual high flow

based on 20 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 853 1,070 1,180 1,290 -- --

3 847 1,060 1,160 1,240 -- --

7 803 1,020 1,120 1,210 -- --

15 752 970 1,080 1,190 -- --

30 695 887 981 1,070 -- --

60 600 760 843 927 -- --

90 546 693 771 854 -- --

Magnitude and probability of seasonal low flow from

July-October based on 19 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 96 53 38 28 -- --

3 100 55 40 30 -- --

7 109 61 46 36 -- --

14 119 70 55 45 -- --

30 138 86 70 60 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 754 141 397 207 20

November 808 246 502 184 20

December 770 236 449 150 20

January 629 196 394 119 20

February 601 230 402 112 20

March 730 233 424 130 20

April 1,090 194 455 225 20

May 804 105 330 203 20

June 999 94 318 220 20

July 742 80 242 168 20

August 820 72 261 186 20

September 836 79 390 247 20

Annual 612 173 380 110 20
28 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06018500 Beaverhead River near Twin Bridges, Mont.

Site Number 13

LOCATION.--Lat 45°23'01", long 112°27'07" (NAD 27), in SW1⁄4NW1⁄4SE1⁄4 sec.22, T.5 S., R.7 W., Madison County, Hydrologic Unit 10020002, on left bank at 

downstream side of bridge on State Highway 41, 11.5 mi upstream from Ruby River, 12.7 mi southwest of Twin Bridges, 14.5 mi northeast of Dillon, and at 

river mile 2,430.4.

DRAINAGE AREA.--3,619 mi2.

PERIOD OF RECORD.--August 1935 to current year (2002). Prior to October 1968, published as "at Blaine."

REVISED RECORDS.--WSP 1309: 1938(M), 1945(M). WSP 1559: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 4,809.15 ft (NGVD 29). Prior to Feb. 17, 1949, nonrecording gage at bridge 0.5 mi upstream at different datum. 

Feb. 17, 1949, to June 28, 1951, nonrecording gage at present site and datum.

REMARKS.--Flow partly regulated by Lima Reservoir (station number 06012000) and Clark Canyon Reservoir (station number 06015300) since August 1964. 

Diversions upstream from station for irrigation of about 135,400 acres of which about 5,000 acres are irrigated by imported water from Birch and Willow Creeks 

and of which about 9,200 acres lies downstream from station including 600 acres in Ruby River drainage. Bureau of Reclamation satellite telemeter at station.

Unregulated streamflow period

Magnitude and probability of annual low flow

based on 27 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 23 12 9.3 7.7 6.3 --

3 25 14 11 8.7 7.2 --

7 31 17 13 11 9.3 --

14 45 24 18 15 12 --

30 70 37 27 21 15 --

60 116 56 37 26 17 --

90 168 79 50 32 19 --

120 197 94 59 38 22 --

183 259 134 87 58 35 --

Magnitude and probability of seasonal low flow from

March-June based on 28 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 27 12 10 8.2 6.7 --

3 30 14 12 9.2 7.7 --

7 38 18 14 12 10 --

14 55 26 20 15 12 --

30 113 47 30 21 16 --

Magnitude and probability of seasonal low flow from

November-February based on 28 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 272 165 119 88 60 --

3 288 176 127 93 62 --

7 316 197 142 104 70 --

14 344 222 163 121 83 --

30 384 285 231 188 144 --

Duration of daily mean flows based on 28 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

18 23 35 60 134 252 344 407

40% 30% 20% 15% 10% 5% 2% 1%

452 498 567 629 691 753 1,030 1,250

Magnitude and probability of annual high flow

based on 28 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 1,050 1,500 1,830 2,290 2,660 --

3 1,000 1,430 1,720 2,100 2,390 --

7 885 1,250 1,510 1,850 2,120 --

15 767 1,050 1,250 1,530 1,750 --

30 661 886 1,060 1,300 1,500 --

60 572 739 860 1,030 1,160 --

90 544 690 785 904 993 --

Magnitude and probability of seasonal low flow from

July-October based on 27 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 40 21 16 12 9.9 --

3 44 24 18 14 11 --

7 51 28 21 17 14 --

14 63 34 26 21 17 --

30 87 46 34 26 20 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 743 32 406 189 28

November 687 247 556 109 28

December 609 330 500 70 28

January 507 173 397 88 28

February 538 200 419 76 28

March 776 299 490 98 28

April 902 96 472 202 28

May 859 41 256 224 28

June 1,400 24 424 394 28

July 870 28 233 201 28

August 431 26 168 102 28

September 630 28 344 171 29

Annual 642 170 389 117 28
Statistical Summaries of Streamflow 29

06018500 Beaverhead River near Twin Bridges, Mont.—Continued

Site Number 13

Regulated streamflow period

Magnitude and probability of annual low flow

based on 38 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 78 44 34 28 22 --

3 86 49 37 30 24 --

7 102 59 45 36 29 --

14 125 75 59 48 39 --

30 155 96 75 62 51 --

60 191 114 87 70 54 --

90 210 127 97 78 61 --

120 229 137 106 85 67 --

183 278 171 134 109 88 --

Magnitude and probability of seasonal low flow from

March-June based on 39 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 85 46 34 28 23 --

3 94 51 38 30 25 --

7 113 64 48 38 30 --

14 142 85 66 54 44 --

30 187 112 88 72 59 --

Magnitude and probability of seasonal low flow from

November-February based on 38 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 284 173 132 104 79 --

3 298 188 146 118 92 --

7 326 219 176 146 117 --

14 348 244 201 171 141 --

30 375 271 226 194 163 --

Duration of daily mean flows based on 39 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

53 66 94 128 193 250 311 374

40% 30% 20% 15% 10% 5% 2% 1%

444 516 640 709 807 994 1,140 1,440

Magnitude and probability of annual high flow

based on 39 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 804 1,190 1,440 1,760 1,990 --

3 775 1,170 1,430 1,760 1,980 --

7 739 1,120 1,380 1,710 1,960 --

15 708 1,070 1,310 1,620 1,850 --

30 666 999 1,220 1,510 1,720 --

60 601 890 1,080 1,330 1,510 --

90 557 824 1,000 1,230 1,410 --

Magnitude and probability of seasonal low flow from

July-October based on 38 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 101 55 43 35 29 --

3 110 61 47 39 32 --

7 122 69 54 45 38 --

14 142 80 63 52 43 --

30 171 98 77 64 53 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 1,330 148 479 259 39

November 1,060 242 553 238 39

December 852 208 479 199 39

January 724 197 422 150 39

February 707 199 430 137 39

March 799 207 467 152 39

April 1,250 136 486 252 39

May 1,120 77 358 255 39

June 1,620 63 364 326 39

July 1,590 55 320 311 39

August 1,580 63 308 290 39

September 1,690 106 418 326 39

Annual 1,100 165 423 187 39
30 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06019500 Ruby River above reservoir, near Alder, Mont.

Site Number 14

LOCATION.--Lat 45°11'33", long 112°08'30" (NAD 27), in NW1⁄4SE1⁄4SW1⁄4 sec.30, T.7 S., R.4 W., Madison County, Hydrologic Unit 10020003, on right bank 

at county road bridge, 0.7 mi downstream from Mormon Creek, 4.2 mi upstream from Ruby Dam, 9.3 mi south of Alder, and at river mile 52.1.

DRAINAGE AREA.--534 mi2.

PERIOD OF RECORD.--May 1938 to current year (2002). Monthly discharge only for May 1938, published in WSP 1309.

REVISED RECORDS.--WSP 1309: 1938(M). WSP 1559: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 5,400 ft (NGVD 29). Prior to Oct. 1, 1938, nonrecording gage at bridge 2.0 mi upstream at different datum. 

Oct. 1, 1938, to Aug. 5, 1955, water-stage recorder at site 2.2 mi upstream at different datum. Aug. 6, 1955, to Sept. 30, 1997, water-stage recorder 2.3 mi 

upstream at different datum.

REMARKS.--Diversion for irrigation of about 3,000 acres upstream from station. U.S. Geological Survey satellite telemeter at station.

Magnitude and probability of annual low flow

based on 63 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 79 63 54 47 39 35

3 81 65 57 50 42 37

7 84 69 60 53 46 41

14 89 74 65 59 51 46

30 93 79 72 66 59 55

60 98 86 80 75 70 66

90 103 91 86 81 76 73

120 107 96 90 86 81 78

183 111 98 92 88 83 80

Magnitude and probability of seasonal low flow from

March-June based on 64 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 93 82 76 71 65 61

3 95 84 78 73 68 65

7 97 86 81 77 73 71

14 100 90 85 82 78 76

30 106 95 90 88 85 83

Magnitude and probability of seasonal low flow from

November-February based on 64 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 89 75 65 57 48 42

3 91 77 68 60 51 45

7 94 80 72 65 56 51

14 97 84 77 71 64 59

30 99 88 82 78 72 69

Duration of daily mean flows based on 64 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

67 69 75 86 99 107 115 123

40% 30% 20% 15% 10% 5% 2% 1%

133 163 201 261 361 548 802 987

Magnitude and probability of annual high flow

based on 64 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 834 1,180 1,420 1,750 2,020 2,300

3 776 1,080 1,280 1,550 1,750 1,960

7 704 974 1,150 1,380 1,560 1,730

15 624 866 1,030 1,230 1,380 1,530

30 543 753 893 1,070 1,210 1,340

60 431 596 709 855 966 1,080

90 352 479 566 677 762 849

Magnitude and probability of seasonal low flow from

July-October based on 64 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 89 68 58 50 43 38

3 90 69 60 52 45 40

7 93 72 62 55 47 43

14 96 76 66 59 52 47

30 100 81 72 66 60 55

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 185 83 122 22 64

November 177 88 123 16 64

December 170 80 111 15 64

January 158 70 103 15 64

February 135 79 103 12 64

March 181 84 110 18 64

April 288 95 165 45 64

May 1,010 187 419 153 65

June 1,120 136 473 235 65

July 482 75 195 96 65

August 235 59 121 39 65

September 171 73 115 25 65

Annual 336 119 180 46 64
Statistical Summaries of Streamflow 31

06020600 Ruby River below reservoir, near Alder, Mont.

Site Number 15

LOCATION.--Lat 45°14'32", long 112°06'36" (NAD 27), in SE1⁄4SE1⁄4NE1⁄4 sec.8, T.7 S., R.4 W., Madison County, Hydrologic Unit 10020003, on right bank 

0.2 mi downstream from Ruby Dam, 5.7 mi south of Alder, and at river mile 47.8.

DRAINAGE AREA.--596 mi2.

PERIOD OF RECORD.--December 1962 to current year (2002).

REVISED RECORDS.--1985(M).

GAGE.--Water-stage recorder. Altitude of gage is 5,286.63 ft (NGVD 29, levels by U.S. Army Corps of Engineers).

REMARKS.--Flow regulated by Ruby River Reservoir (station number 06020500). Diversions for irrigation of about 3,500 acres upstream from station. U.S. 

Geological Survey satellite telemeter at station.

Magnitude and probability of annual low flow

based on 39 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 29 21 18 16 14 --

3 30 23 19 17 15 --

7 31 23 20 17 15 --

14 32 24 21 18 16 --

30 33 25 22 20 18 --

60 37 28 25 23 21 --

90 44 31 27 24 21 --

120 51 36 31 27 23 --

183 100 74 62 54 45 --

Magnitude and probability of seasonal low flow from

March-June based on 40 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 38 27 23 20 17 --

3 40 28 24 21 18 --

7 41 29 24 21 18 --

14 42 29 25 21 19 --

30 47 31 25 22 19 --

Magnitude and probability of seasonal low flow from

November-February based on 39 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 34 24 20 17 14 --

3 35 25 21 18 15 --

7 36 25 21 18 15 --

14 37 26 22 19 16 --

30 38 28 24 21 18 --

Duration of daily mean flows based on 39 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

21 24 27 32 42 55 74 116

40% 30% 20% 15% 10% 5% 2% 1%

198 283 357 408 482 640 918 1,060

Magnitude and probability of annual high flow

based on 39 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 942 1,320 1,570 1,880 2,110 --

3 895 1,240 1,460 1,740 1,940 --

7 814 1,120 1,320 1,560 1,740 --

15 736 994 1,160 1,360 1,500 --

30 647 864 1,000 1,180 1,300 --

60 523 685 795 937 1,050 --

90 468 587 663 758 828 --

Magnitude and probability of seasonal low flow from

July-October based on 39 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 64 43 35 30 25 --

3 68 47 39 33 28 --

7 73 50 41 35 29 --

14 83 55 44 37 31 --

30 111 70 54 43 33 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 244 38 123 57 39

November 222 34 74 41 39

December 142 24 55 30 40

January 139 21 51 29 40

February 92 21 46 19 40

March 174 19 58 35 40

April 192 30 92 48 40

May 1,040 189 421 159 40

June 1,210 281 594 231 40

July 558 197 352 79 40

August 474 222 355 60 40

September 399 59 251 71 40

Annual 352 128 208 48 39
32 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06021500 Ruby River at Laurin, Mont.

Site Number 16

LOCATION.--Lat 45°21'09", long 112°07'21" (NAD 27), in SW1⁄4SE1⁄4 sec.32, T.5 S., R.4 W., Madison County, on right bank 200 ft downstream from highway 

bridge in Laurin and 0.75 mi upstream from Alder Creek.

DRAINAGE AREA.--650 mi2.

PERIOD OF RECORD.--14 years (1946-60).

GAGE.--Water-stage recorder. Altitude of gage is 5,045 ft (NGVD 29, from topographic map).

REMARKS.--Flow regulated by Ruby River Reservoir. Diversions upstream from station for irrigation of about 13,000 acres, of which about 2,000 acres lie below 

station. The flow of Clear Creek (secondary channel of Ruby River), which begins approximately 3 mi upstream and returns to the river approximately 3 mi 

downstream, is not included in discharge.

Magnitude and probability of annual low flow

based on 14 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 18 11 9.4 8.1 -- --

3 18 12 9.5 8.2 -- --

7 20 13 11 9.0 -- --

14 22 14 12 10 -- --

30 23 15 13 11 -- --

60 26 17 14 12 -- --

90 32 20 17 14 -- --

120 40 26 21 18 -- --

183 46 30 25 21 -- --

Magnitude and probability of seasonal low flow from

March-June based on 14 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 25 16 13 11 -- --

3 26 17 13 11 -- --

7 28 17 14 12 -- --

14 32 19 14 12 -- --

30 37 20 15 12 -- --

Magnitude and probability of seasonal low flow from

November-February based on 15 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 20 12 9.4 8.2 -- --

3 21 12 9.6 8.3 -- --

7 23 14 11 9.1 -- --

14 25 15 12 10 -- --

30 27 17 13 11 -- --

Duration of daily mean flows based on 14 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

12 14 17 20 27 35 46 57

40% 30% 20% 15% 10% 5% 2% 1%

69 86 110 124 153 200 323 412

Magnitude and probability of annual high flow

based on 14 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 341 565 728 945 -- --

3 316 518 669 874 -- --

7 273 451 591 793 -- --

15 218 360 475 644 -- --

30 176 283 372 509 -- --

60 141 219 284 384 -- --

90 122 190 246 331 -- --

Magnitude and probability of seasonal low flow from

July-October based on 14 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 31 22 18 16 -- --

3 32 23 19 17 -- --

7 35 24 20 18 -- --

14 37 26 22 19 -- --

30 42 30 25 22 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 174 22 62 38 15

November 160 21 66 37 15

December 132 18 58 38 15

January 117 16 43 30 15

February 96 13 39 28 15

March 186 14 56 50 15

April 248 16 81 71 14

May 362 28 112 86 14

June 499 44 169 137 14

July 184 42 95 44 14

August 114 29 73 27 15

September 134 28 64 31 15

Annual 172 36 78 38 14
Statistical Summaries of Streamflow 33

06023000 Ruby River near Twin Bridges, Mont.

Site Number 17

LOCATION.--Lat 45°30'28", long 112°19'48" (NAD 27), in SE1⁄4NE1⁄4NW1⁄4 sec.10, T.4 S., R.6 W., Madison County, Hydrologic Unit 10020003, on right bank 

300 ft upstream from county bridge, 1.2 mi upstream from mouth, and 2.6 mi south of Twin Bridges.

DRAINAGE AREA.--935 mi2. 

PERIOD OF RECORD.--August to October 1940, July 1941 to June 1943, July 1946 to September 1965, and July 1, 1979, to Sept. 30, 1981 (discontinued). 

GAGE.--Water-stage recorder. Altitude of gage is 4,660 ft (NGVD 29, from topographic map). 

REMARKS.--Diversions for irrigation of about 28,500 acres, of which about 500 acres lies downstream from station. Some regulation by Ruby River 

Reservoir (station number 06020500) 24 mi upstream from station. 

Magnitude and probability of annual low flow

based on 20 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 41 14 7.3 4.0 -- --

3 44 15 7.8 4.2 -- --

7 57 21 11 5.6 -- --

14 75 31 16 8.0 -- --

30 85 48 32 22 -- --

60 106 69 53 41 -- --

90 117 82 67 56 -- --

120 146 101 80 64 -- --

183 166 121 99 83 -- --

Magnitude and probability of seasonal low flow from

March-June based on 23 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 48 16 8.4 4.5 -- --

3 52 18 9.2 4.9 -- --

7 68 25 13 6.7 -- --

14 91 37 19 9.4 -- --

30 107 56 36 24 -- --

Magnitude and probability of seasonal low flow from

November-February based on 23 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 109 85 73 64 -- --

3 111 87 76 67 -- --

7 114 94 85 79 -- --

14 120 101 92 86 -- --

30 128 109 101 95 -- --

Duration of daily mean flows based on 22 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

22 38 70 95 115 134 152 171

40% 30% 20% 15% 10% 5% 2% 1%

189 223 257 283 334 404 692 925

Magnitude and probability of annual high flow

based on 22 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 664 1,010 1,240 1,520 -- --

3 625 963 1,190 1,490 -- --

7 559 880 1,120 1,440 -- --

15 477 765 998 1,340 -- --

30 408 643 837 1,130 -- --

60 330 487 613 798 -- --

90 287 406 498 632 -- --

Magnitude and probability of seasonal low flow from

July-October based on 22 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 86 51 34 22 -- --

3 92 55 36 24 -- --

7 99 60 40 26 -- --

14 106 66 46 31 -- --

30 119 77 56 41 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 327 88 212 54 24

November 307 136 219 46 23

December 308 124 183 47 23

January 266 96 144 37 23

February 212 98 143 32 23

March 325 103 159 56 23

April 409 82 189 90 23

May 691 23 193 144 23

June 1,020 41 382 299 23

July 456 80 227 103 24

August 211 43 138 46 25

September 334 122 203 56 26

Annual 370 108 199 60 22
34 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06024590 Wise River near Wise River, Mont.

Site Number 18

LOCATION.--Lat 45°42'17", long 113°01'50" (NAD 27), in SE1⁄4NE1⁄4SW1⁄4 sec.36, T.1 S., R.12 W., Beaverhead County, Hydrologic Unit 10020004, Beaverhead 

National Forest, on left bank 6 ft downstream from abandoned bridge on old county road, 6.5 mi southwest of Wise River, and at river mile 9.1. 

DRAINAGE AREA.--214 mi2. 

PERIOD OF RECORD.--October 1972 to September 1985 (discontinued). 

GAGE.--Water-stage recorder and crest-stage gage. Altitude of gage is 6,112.52 ft (NGVD 29, from U.S. Forest Service bench mark). 

Magnitude and probability of annual low flow

based on 12 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 27 22 19 16 -- --

3 29 24 21 18 -- --

7 31 26 23 21 -- --

14 33 28 26 24 -- --

30 34 31 30 30 -- --

60 37 34 32 31 -- --

90 41 36 34 33 -- --

120 44 38 35 34 -- --

183 53 43 39 36 -- --

Magnitude and probability of seasonal low flow from

March-June based on 13 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 34 31 30 29 -- --

3 35 32 31 30 -- --

7 36 33 31 30 -- --

14 37 33 32 30 -- --

30 38 34 32 31 -- --

Magnitude and probability of seasonal low flow from

November-February based on 13 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 27 22 19 16 -- --

3 29 24 21 18 -- --

7 32 26 23 21 -- --

14 34 29 26 24 -- --

30 36 32 31 31 -- --

Duration of daily mean flows based on 13 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

25 27 33 35 40 44 51 62

40% 30% 20% 15% 10% 5% 2% 1%

80 111 190 307 549 935 1,340 1,510

Magnitude and probability of annual high flow

based on 13 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 1,530 1,990 2,210 2,400 -- --

3 1,400 1,870 2,090 2,310 -- --

7 1,280 1,730 1,960 2,200 -- --

15 1,150 1,540 1,720 1,900 -- --

30 985 1,330 1,500 1,660 -- --

60 748 995 1,110 1,210 -- --

90 569 749 831 903 -- --

Magnitude and probability of seasonal low flow from

July-October based on 12 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 52 41 36 33 -- --

3 54 43 38 34 -- --

7 56 44 39 35 -- --

14 59 46 40 36 -- --

30 62 48 42 38 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 111 42 68 22 13

November 88 36 54 14 13

December 73 36 46 11 13

January 61 33 42 8.1 13

February 54 32 39 6.9 13

March 52 30 39 6.3 13

April 143 33 88 36 13

May 1,180 135 508 264 13

June 1,330 282 858 344 13

July 777 68 279 184 13

August 192 44 99 39 13

September 132 43 79 28 13

Annual 287 84 183 53 13
Statistical Summaries of Streamflow 35

06025500 Big Hole River near Melrose, Mont.

Site Number 19

LOCATION.--Lat 45°31'36", long 112°42'03" (NAD 27), in SE1⁄4SE1⁄4SW1⁄4 sec.34, T.3 S., R.9 W., Madison County, Hydrologic Unit 10020004, on left bank 50 ft 

downstream from bridge, on frontage road east of Interstate 15, 0.1 mi downstream from Rock Creek, 7 mi south of Melrose, and at river mile 31.1.

DRAINAGE AREA.--2,476 mi2.

PERIOD OF RECORD.--October 1923 to current year (2002). Monthly discharge only for some periods, published in WSP 1309.

GAGE.--Water-stage recorder. Altitude of gage is 5,032.87 ft (NGVD 29). Prior to June 14, 1927, water-stage recorder, and July 17, 1927, to Sept. 30, 1931, 

nonrecording gage, at site 1.7 mi upstream at different datum.

REMARKS.--Diversions for irrigation of about 136,000 acres upstream from station. Bureau of Reclamation satellite telemeter at station.

Magnitude and probability of annual low flow

based on 78 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 195 136 109 89 70 58

3 206 146 118 97 77 65

7 221 156 126 104 82 69

14 237 167 134 109 85 71

30 264 186 148 121 93 77

60 296 215 178 150 123 106

90 327 247 210 183 156 139

120 362 281 245 218 191 174

183 382 296 260 233 206 190

Magnitude and probability of seasonal low flow from

March-June based on 79 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 323 262 235 214 192 178

3 333 274 247 227 206 193

7 348 291 265 246 227 214

14 367 306 281 263 246 235

30 430 341 307 283 261 248

Magnitude and probability of seasonal low flow from

November-February based on 78 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 215 165 143 127 111 102

3 232 180 157 140 124 114

7 255 200 176 157 139 128

14 276 219 193 174 155 143

30 304 243 216 195 174 160

Duration of daily mean flows based on 79 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

139 165 209 256 312 361 422 491

40% 30% 20% 15% 10% 5% 2% 1%

609 838 1,440 2,090 3,010 4,670 6,810 8,240

Magnitude and probability of annual high flow

based on 79 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 6,690 9,800 11,600 13,700 15,000 16,300

3 6,440 9,400 11,100 13,000 14,300 15,400

7 5,870 8,600 10,200 12,000 13,100 14,200

15 5,170 7,650 9,160 10,900 12,100 13,100

30 4,500 6,610 7,860 9,280 10,200 11,100

60 3,610 5,160 6,070 7,090 7,770 8,380

90 2,950 4,170 4,890 5,710 6,260 6,770

Magnitude and probability of seasonal low flow from

July-October based on 78 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 252 160 122 96 72 59

3 254 164 127 102 79 66

7 260 168 131 106 82 69

14 272 175 137 110 86 72

30 299 193 150 121 94 79

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 1,110 184 494 195 79

November 1,040 255 493 146 79

December 763 223 392 118 79

January 716 143 348 95 79

February 800 143 361 102 79

March 958 248 473 162 79

April 3,520 490 1,490 627 79

May 8,290 1,110 3,280 1,560 79

June 8,380 814 3,950 2,040 79

July 4,120 254 1,310 787 79

August 1,460 88 466 243 79

September 870 114 373 183 79

Annual 2,020 486 1,120 377 79
36 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06026000 Birch Creek near Glen, Mont.

Site Number 20

LOCATION.--Lat 45°22'46", long 112°47'48" (NAD 27), in SE1⁄4 SE1⁄4 sec.23, T.5 S., R.10 W., Beaverhead County, Hydrologic Unit 10020004, Beaverhead 

National Forest, on left bank 2.3 mi downstream from Sheep Creek and 8.5 mi southwest of Glen.

DRAINAGE AREA.--36.0 mi2 . 

PERIOD OF RECORD.--28 years. May 1946 to September 1953, April 1955 to September 1976 (discontinued). Monthly discharge only for May 1946, published 

in WSP 1309. Prior to October 1950, published as "near Reichle."

GAGE.--Water-stage recorder. Concrete control since May 19, 1966. Altitude of gage is 5,862 ft (NGVD 29) from plane-table survey. Prior to Nov. 16, 1949, 

at site 1.5 mi upstream at different datum.

REMARKS.--Some regulation at lakes in headwaters. Minor diversions for irrigation upstream from station. Recorded diversions from Willow Creek 

basin into Birch Creek upstream from station.

Magnitude and probability of annual low flow

based on 26 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 3.0 2.0 1.7 1.5 1.3 --

3 3.3 2.3 1.9 1.6 1.4 --

7 3.8 2.8 2.4 2.1 1.8 --

14 4.4 3.3 2.9 2.6 2.3 --

30 5.6 4.5 4.1 3.8 3.5 --

60 6.6 5.6 5.2 4.9 4.6 --

90 7.3 6.1 5.5 5.1 4.7 --

120 8.3 6.9 6.3 5.8 5.3 --

183 10 8.5 7.7 7.1 6.5 --

Magnitude and probability of seasonal low flow from

March-June based on 28 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 5.9 4.4 3.8 3.3 2.8 --

3 6.1 4.7 4.0 3.5 3.0 --

7 6.4 4.9 4.3 3.8 3.3 --

14 6.7 5.3 4.6 4.1 3.6 --

30 7.5 5.9 5.1 4.6 4.0 --

Magnitude and probability of seasonal low flow from

November-February based on 28 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 3.0 2.1 1.7 1.5 1.3 --

3 3.4 2.3 1.9 1.7 1.4 --

7 4.1 2.9 2.4 2.1 1.8 --

14 4.8 3.5 3.0 2.6 2.3 --

30 6.2 4.9 4.4 3.9 3.5 --

Duration of daily mean flows based on 28 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

3.2 4.0 4.8 5.9 7.2 8.7 11 13

40% 30% 20% 15% 10% 5% 2% 1%

17 25 46 62 84 120 168 188

Magnitude and probability of annual high flow

based on 28 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 184 247 286 332 364 --

3 173 227 258 292 315 --

7 164 213 239 266 282 --

15 148 188 207 225 234 --

30 130 165 181 196 204 --

60 103 127 138 147 152 --

90 85 103 109 115 118 --

Magnitude and probability of seasonal low flow from

July-October based on 28 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 9.1 6.5 5.3 4.4 3.5 --

3 9.4 6.8 5.6 4.6 3.7 --

7 9.9 7.3 6.0 5.0 4.0 --

14 10 7.6 6.3 5.4 4.4 --

30 11 8.6 7.4 6.5 5.5 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 31 9.1 17 5.4 28

November 21 5.8 11 3.6 28

December 13 3.8 8.0 2.3 28

January 12 5.2 8.0 1.8 28

February 12 4.3 7.3 1.9 28

March 15 4.2 8.0 2.3 28

April 21 5.7 12 4.5 29

May 130 19 53 26 30

June 190 38 115 36 30

July 164 23 67 27 30

August 58 8.3 29 11 30

September 22 6.6 13 3.9 30

Annual 39 16 29 5.9 28
Statistical Summaries of Streamflow 37

06026500 Jefferson River near Twin Bridges, Mont.

Site Number 21

LOCATION.--Lat 45°36'45", long 112°19'47" (NAD 27), in SE1⁄4SE1⁄4SW1⁄4 sec.34, T.2 S., R.6 W., Madison County, Hydrologic Unit 10020005, on left bank 

0.4 mi upstream from Hells Canyon Creek, 4.8 mi north of Twin Bridges, and at river mile 2,399.7.

DRAINAGE AREA.--7,632 mi2.

PERIOD OF RECORD.--August 1940 to September 1943, October 1957 to September 1972, May 1994 to current year (2002).

GAGE.--Water-stage recorder. Altitude of gage is 4,560 ft (NGVD 29). August 1940 to September 1943, nonrecording gage at site 500 ft downstream at different 

datum. October 1957 to June 3, 1972, water-stage recorder at site 250 ft downstream and June 4 to September 30, 1972, nonrecording gage 6.5 mi downstream 

at different datums.

REMARKS.--Some regulation by Clark Canyon (station number 06015300), Lima, and Ruby River Reservoirs. Diversion for irrigation of about 

310,000 acres upstream from station. U.S. Geological Survey satellite telemeter at station. 

Magnitude and probability of annual low flow

based on 15 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 721 473 348 257 -- --

3 745 491 363 270 -- --

7 791 515 381 285 -- --

14 842 548 407 306 -- --

30 957 635 468 346 -- --

60 1,090 747 561 421 -- --

90 1,210 867 679 532 -- --

120 1,320 986 796 644 -- --

183 1,350 1,050 894 766 -- --

Magnitude and probability of seasonal low flow from

March-June based on 17 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1,090 919 833 765 -- --

3 1,120 942 857 789 -- --

7 1,160 995 909 840 -- --

14 1,220 1,030 937 865 -- --

30 1,310 1,060 957 880 -- --

Magnitude and probability of seasonal low flow from

November-February based on 16 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 940 726 591 478 -- --

3 982 761 620 503 -- --

7 1,050 831 685 560 -- --

14 1,110 907 779 669 -- --

30 1,160 965 848 747 -- --

Duration of daily mean flows based on 17 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

286 342 567 796 988 1,160 1,300 1,450

40% 30% 20% 15% 10% 5% 2% 1%

1,690 1,990 2,570 3,410 4,920 7,230 9,630 11,300

Magnitude and probability of annual high flow

based on 17 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 10,600 13,900 15,000 15,900 -- --

3 10,200 13,400 14,500 15,200 -- --

7 9,620 12,500 13,500 14,100 -- --

15 8,840 11,500 12,400 13,000 -- --

30 7,750 10,000 10,700 11,200 -- --

60 6,130 7,720 8,250 8,600 -- --

90 5,080 6,300 6,720 7,000 -- --

Magnitude and probability of seasonal low flow from

July-October based on 16 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 726 476 352 262 -- --

3 750 498 368 275 -- --

7 798 522 387 291 -- --

14 845 556 412 312 -- --

30 960 642 473 354 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 2,050 730 1,350 410 17

November 2,020 873 1,480 379 17

December 1,860 708 1,250 328 17

January 1,420 641 1,130 253 17

February 1,690 627 1,160 259 17

March 2,090 622 1,300 394 17

April 4,450 1,100 2,220 930 17

May 7,020 1,500 3,970 1,800 18

June 9,820 1,300 5,970 3,000 18

July 4,480 527 2,170 1,230 18

August 1,700 302 921 480 18

September 2,110 288 1,050 518 18

Annual 2,820 955 2,050 602 17
38 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06027000 Jefferson River near Silver Star, Mont.

Site Number 22

LOCATION.--Lat 45°38'37", long 112°18'41" (NAD 27), in SW1⁄4 sec.23, T.2 S., R.6 W., Madison County, on highway bridge 0.5 mi west of Ironrod, 4 mi 

southwest of Silverstar, and 7 mi downstream from the confluence of the Beaverhead and Big Hole Rivers.

DRAINAGE AREA.--7,683 mi2 (revised).

PERIOD OF RECORD.--25 years (1910-16, 1920-39).

GAGE.--Wire-weight gage. Altitude of gage is 4,550 ft (NGVD 29, by barometer). Aug. 11, 1910, to Sept. 30, 1916, and July 22 to Aug. 26, 1920, staff gage.

REMARKS.--Diversions for irrigation of about 300,000 acres upstream from station.

Magnitude and probability of annual low flow

based on 23 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 284 122 76 51 -- --

3 297 128 80 54 -- --

7 317 137 85 57 -- --

14 348 152 94 62 -- --

30 412 183 112 72 -- --

60 506 233 144 93 -- --

90 612 305 198 134 -- --

120 735 405 281 203 -- --

183 870 568 443 356 -- --

Magnitude and probability of seasonal low flow from

March-June based on 25 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 842 607 509 438 369 --

3 859 632 536 468 400 --

7 898 680 588 522 456 --

14 952 765 688 634 581 --

30 1,060 882 812 763 716 --

Magnitude and probability of seasonal low flow from

November-February based on 25 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 763 527 421 344 269 --

3 772 532 424 346 271 --

7 785 540 432 354 278 --

14 804 567 461 384 307 --

30 846 621 519 442 366 --

Duration of daily mean flows based on 25 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

86 120 258 435 677 851 1,000 1,170

40% 30% 20% 15% 10% 5% 2% 1%

1,360 1,620 2,140 2,700 3,640 5,630 8,510 10,700

Magnitude and probability of annual high flow

based on 25 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 8,210 12,300 14,800 17,500 19,200 --

3 7,770 11,700 14,000 16,600 18,300 --

7 7,100 10,700 12,900 15,500 17,200 --

15 6,260 9,570 11,600 14,100 15,800 --

30 5,490 8,280 10,000 12,100 13,600 --

60 4,410 6,400 7,620 9,030 10,000 --

90 3,640 5,190 6,150 7,280 8,070 --

Magnitude and probability of seasonal low flow from

July-October based on 23 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 288 125 78 52 -- --

3 302 133 83 57 -- --

7 326 144 90 60 -- --

14 360 157 99 66 -- --

30 429 188 116 76 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 1,970 240 1,040 514 25

November 2,080 562 1,290 400 25

December 2,250 527 1,100 389 25

January 1,550 394 958 265 25

February 1,600 357 939 275 25

March 2,180 781 1,170 326 25

April 3,720 1,020 2,240 705 25

May 7,830 1,330 3,900 1,720 25

June 10,500 1,050 4,840 3,000 25

July 5,120 177 1,630 1,230 25

August 2,030 78 652 494 27

September 1,890 92 800 526 27

Annual 2,950 698 1,720 613 25
Statistical Summaries of Streamflow 39

06033000 Boulder River near Boulder, Mont.

Site Number 23

LOCATION.--Lat 46°12'40", long 112°05'27" (NAD 27), in SE1⁄4NE1⁄4SW1⁄4 sec.3, T.5 N., R.4 W., Jefferson County, Hydrologic Unit 10020006, on left bank 40 ft 

downstream from county bridge, 1.1 mile downstream from Muskrat Creek, 2.0 mi southeast of Boulder, and at river mile 44.1.

DRAINAGE AREA.--381 mi2.

PERIOD OF RECORD.--May 1929 to December 1932, March 1934 to September 1972, October 1984 to current year (2002). Monthly discharge only for some 

periods, published in WSP 1309.

REVISED RECORDS.--WSP 1729: 1931.

GAGE.--Water-stage recorder. Altitude of gage is 4,810 ft (NGVD 29). Prior to Aug. 29, 1946, nonrecording gage at present site and datum.

REMARKS.--Diversions for irrigation of about 3,500 acres upstream from station. U.S. Geological Survey satellite telemeter at station.

Magnitude and probability of annual low flow

based on 58 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 12 7.3 5.2 3.7 1.4 0.00

3 13 7.7 5.6 4.1 1.7 .00

7 13 8.2 6.2 4.7 3.5 2.8

14 14 9.0 6.9 5.5 4.2 3.4

30 16 10 7.9 6.3 4.9 4.1

60 19 12 9.6 7.6 5.9 4.9

90 23 15 12 9.5 7.3 6.0

120 26 18 14 11 8.7 7.3

183 28 19 16 13 11 9.4

Magnitude and probability of seasonal low flow from

March-June based on 60 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 27 20 17 14 12 10

3 28 21 18 15 12 11

7 30 23 20 17 15 13

14 32 25 22 20 18 17

30 42 31 27 24 21 19

Magnitude and probability of seasonal low flow from

November-February based on 59 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 18 11 7.2 4.7 2.7 1.7

3 20 12 7.9 5.1 2.8 2.0

7 22 13 8.8 5.6 3.7 3.0

14 22 14 11 8.3 5.9 4.6

30 24 17 13 11 8.4 7.0

Duration of daily mean flows based on 59 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

6.1 7.3 11 16 22 27 31 38

40% 30% 20% 15% 10% 5% 2% 1%

45 69 148 228 344 547 865 1,060

Magnitude and probability of annual high flow

based on 59 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 961 1,430 1,740 2,130 2,410 2,690

3 879 1,290 1,560 1,890 2,130 2,360

7 793 1,150 1,380 1,640 1,820 1,990

15 685 998 1,190 1,420 1,580 1,730

30 575 837 1,000 1,190 1,330 1,460

60 443 616 716 830 906 975

90 344 478 557 649 710 768

Magnitude and probability of seasonal low flow from

July-October based on 60 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 13 7.5 5.4 3.9 1.5 0.00

3 14 7.9 5.8 4.2 1.9 .00

7 14 8.5 6.4 4.9 3.6 2.9

14 15 9.2 7.1 5.7 4.5 3.6

30 17 10 8.1 6.5 5.1 4.3

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 113 5.8 37 21 60

November 71 9.1 35 12 60

December 53 7.4 29 9.2 60

January 42 10 26 8.3 59

February 68 7.7 31 12 59

March 121 21 48 22 60

April 511 46 166 96 60

May 961 126 461 182 61

June 1,030 70 407 252 61

July 374 11 96 82 61

August 194 7.1 31 28 61

September 156 5.7 29 26 61

Annual 211 48 117 42 59
40 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06034500 Jefferson River at Sappington, Mont.

Site Number 24

LOCATION.--Lat 45°48'15", long 111°45'05" (NAD 27), in SE1⁄4 sec.29, T.1 N., R.1 W., Gallatin County, on right bank upstream side of bridge on State Highway 

287, 1 mi northeast of Sappington, 5.5 mi upstream from Willow Creek, and at river mi 18.0.

DRAINAGE AREA.--9,277 mi2.

PERIOD OF RECORD.--36 years (1896-1905, 1938-65).

REVISED RECORDS.--WSP 1389: 1899, 1900, 1902(M), 1904(M). WSP 1559: Drainage area.

GAGE.--Digital water-stage recorder. Altitude of gage is 4,170 ft (NGVD 29, from topographic map). Prior to Sept. 17, 1896, staff gage and Sept. 17, 1896, to 

Dec. 31, 1905, chain gage at railroad bridge 1.5 mi upstream at different datum. Aug. 16, 1938, to Sept. 30, 1964, graphic water-stage recorder at present site 

and datum.

REMARKS.--Diversions for irrigation of about 355,000 acres upstream from station. Some regulation by Clark Canyon Reservoir (station number 06015300) at 

Lima, and Ruby River Reservoir.

Magnitude and probability of annual low flow

based on 28 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 431 285 223 178 136 --

3 446 293 227 180 136 --

7 475 307 234 184 136 --

14 518 328 248 192 140 --

30 595 376 282 217 156 --

60 743 495 377 291 209 --

90 882 611 483 387 294 --

120 1,010 767 656 573 488 --

183 1,130 930 839 769 698 --

Magnitude and probability of seasonal low flow from

March-June based on 31 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1,080 784 638 526 413 --

3 1,120 841 698 586 472 --

7 1,180 927 796 692 581 --

14 1,210 1,020 928 861 792 --

30 1,400 1,190 1,090 1,010 932 --

Magnitude and probability of seasonal low flow from

November-February based on 29 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 709 513 434 378 323 --

3 746 555 476 419 363 --

7 799 614 537 482 428 --

14 907 709 620 552 483 --

30 1,020 838 753 687 619 --

Duration of daily mean flows based on 30 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

247 351 521 671 902 1,110 1,250 1,400

40% 30% 20% 15% 10% 5% 2% 1%

1,610 1,970 2,630 3,320 4,360 6,110 8,350 10,200

Magnitude and probability of annual high flow

based on 30 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 8,400 11,300 13,300 15,700 17,600 --

3 8,210 11,000 12,800 15,200 16,900 --

7 7,680 10,400 12,200 14,400 16,100 --

15 6,870 9,380 11,000 13,100 14,700 --

30 6,140 8,230 9,570 11,200 12,500 --

60 4,970 6,550 7,500 8,600 9,370 --

90 4,200 5,480 6,250 7,140 7,750 --

Magnitude and probability of seasonal low flow from

July-October based on 28 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 447 291 225 180 136 --

3 458 297 229 181 137 --

7 481 309 236 185 137 --

14 521 332 249 194 141 --

30 598 377 283 221 157 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 2,340 776 1,360 465 30

November 3,200 1,060 1,650 409 30

December 2,710 999 1,420 344 30

January 1,890 545 1,130 275 31

February 2,850 829 1,280 402 31

March 2,060 924 1,460 256 31

April 5,030 1,080 2,580 947 31

May 8,060 1,210 4,520 1,930 31

June 12,200 1,880 5,360 2,230 31

July 3,760 215 1,870 903 31

August 1,610 166 709 349 32

September 1,880 497 921 341 32

Annual 3,350 1,170 2,020 499 30
Statistical Summaries of Streamflow 41

06035000 Willow Creek near Harrison, Mont.

Site Number 25

LOCATION.--Lat 46°43'23", long 111°44'25" (NAD 27), in SE1⁄4SW1⁄4NW1⁄4 sec.28, T.1 S., R.1 W., Madison County, Hydrologic Unit 10020005, on right bank 

2.2 mi upstream from Willow Creek Dam, 2.5 mi northeast of Harrison, and at river mile 13.6. 

DRAINAGE AREA.--83.8 mi2. 

PERIOD OF RECORD.--April 1938 to September 1982, October 1982 to October 2002 (seasonal records only, discontinued). Monthly discharge only for some 

periods, published in WSP 1309. 

REVISED RECORDS.-- WSP 1559: Drainage area. 

GAGE.--Water-stage recorder and concrete control. Altitude of gage is 4,750 ft (NGVD 29). Prior to Oct. 8, 1946, water-stage recorder at datum 0.22 ft higher, 

with different concrete control. 

REMARKS.--Diversions for irrigation of about 12,500 acres of which 3,500 acres are in Norwegian Creek drainage.

Magnitude and probability of annual low flow

based on 43 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 4.7 2.9 2.3 2.0 1.6 --

3 4.9 3.0 2.4 2.0 1.7 --

7 5.2 3.2 2.5 2.1 1.7 --

14 5.7 3.5 2.7 2.2 1.8 --

30 6.7 3.9 3.0 2.4 1.9 --

60 9.1 4.9 3.6 2.8 2.1 --

90 13 6.5 4.5 3.3 2.3 --

120 17 9.6 6.8 5.1 3.6 --

183 22 15 12 9.4 7.3 --

Magnitude and probability of seasonal low flow from

March-June based on 44 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 14 8.4 6.1 4.5 3.1 --

3 16 9.3 6.6 4.8 3.2 --

7 18 11 7.7 5.6 3.7 --

14 21 13 9.0 6.5 4.3 --

30 27 18 13 9.8 6.8 --

Magnitude and probability of seasonal low flow from

November-February based on 44 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 14 9.6 7.4 5.8 4.3 --

3 15 10 8.0 6.4 4.8 --

7 16 11 9.3 7.7 6.1 --

14 18 13 11 8.8 7.0 --

30 21 16 14 12 10 --

Duration of daily mean flows based on 44 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

2.2 2.8 3.9 5.8 12 19 25 30

40% 30% 20% 15% 10% 5% 2% 1%

36 43 57 65 90 142 215 265

Magnitude and probability of annual high flow

based on 44 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 200 304 379 478 555 --

3 185 279 343 427 490 --

7 166 251 308 381 435 --

15 144 221 274 340 390 --

30 121 190 239 305 357 --

60 91 141 178 228 268 --

90 76 116 144 181 210 --

Magnitude and probability of seasonal low flow from

July-October based on 64 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 4.8 3.0 2.4 2.0 1.7 0.85

3 5.0 3.2 2.4 2.1 1.7 .86

7 5.3 3.3 2.6 2.1 1.8 .94

14 5.8 3.6 2.8 2.3 1.8 1.0

30 6.8 4.0 3.1 2.5 2.0 1.1

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 80 2.0 29 19 64

November 56 9.4 34 12 44

December 47 12 30 8.0 44

January 44 10 25 6.3 44

February 61 12 27 9.0 44

March 45 18 32 5.8 44

April 72 11 42 13 64

May 167 11 62 36 65

June 300 10 111 71 65

July 278 1.5 61 54 65

August 61 1.1 12 13 65

September 62 2.0 19 16 65

Annual 76 19 41 15 44
42 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06036500 Willow Creek near Willow Creek, Mont.

Site Number 26

LOCATION.--Lat 45°45'00", long 111°39'30" (NAD 27), in SW1⁄4 sec.18, T.1 S., R.1 E., Gallatin County, 3 mi downstream from Willow Creek Reservoir, 5.5 mi 

south of town of Willow Creek, and 6 mi upstream from mouth.

DRAINAGE AREA.--165 mi2 (revised).

PERIOD OF RECORD.--16 years (1919-32, 1947-50).

GAGE.--Water-stage recorder. Altitude of gage is 4,340 ft (NGVD 29, from topographic map). Prior to June 14, 1920, staff gage at site 0.5 mi downstream at 

different datum. June 14, 1920, to Dec. 9, 1932, chain gage at present site at different datum. May 9 to June 30, 1946, staff gage at site 500 ft downstream at 

datum 1.5 ft higher. July 1, 1946, to Sept. 30, 1947, wire-weight gage at present site and datum. Oct. 1, 1947, to Nov. 28, 1949, staff gage at site 0.5 mi 

downstream at different datum.

REMARKS.--Regulation by Willow Creek Reservoir since 1937. Diversions for irrigation of about 12,800 acres upstream from station.

Magnitude and probability of annual low flow

based on 11 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 12 6.6 4.7 3.5 -- --

3 13 8.3 6.7 5.6 -- --

7 14 9.7 8.1 7.0 -- --

14 15 11 9.0 7.8 -- --

30 18 14 12 11 -- --

60 21 17 15 13 -- --

90 26 21 18 16 -- --

120 29 23 20 18 -- --

183 33 25 21 18 -- --

Magnitude and probability of seasonal low flow from

March-June based on 12 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 28 15 10 7.2 -- --

3 30 17 12 8.6 -- --

7 31 20 15 11 -- --

14 34 23 18 14 -- --

30 40 29 23 18 -- --

Magnitude and probability of seasonal low flow from

November-February based on 13 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 17 9.3 6.1 4.1 -- --

3 18 12 9.2 7.2 -- --

7 19 14 11 9.1 -- --

14 20 15 12 10 -- --

30 22 18 16 15 -- --

Duration of daily mean flows based on 12 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

7.6 9.1 12 16 23 28 32 37

40% 30% 20% 15% 10% 5% 2% 1%

43 52 65 79 94 136 208 249

Magnitude and probability of annual high flow

based on 12 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 208 299 357 -- -- --

3 194 278 335 -- -- --

7 177 254 305 -- -- --

15 151 213 256 -- -- --

30 122 174 212 -- -- --

60 98 141 173 -- -- --

90 85 118 139 -- -- --

Magnitude and probability of seasonal low flow from

July-October based on 13 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 12 7.7 6.2 5.2 -- --

3 13 8.5 6.9 5.9 -- --

7 14 9.7 8.2 7.2 -- --

14 17 12 9.1 8.0 -- --

30 20 14 12 11 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 88 10 38 20 14

November 60 21 41 13 14

December 51 15 34 12 14

January 40 15 26 6.7 13

February 40 15 28 9.6 13

March 60 26 44 8.0 13

April 110 17 58 23 13

May 146 15 92 40 13

June 242 42 112 71 12

July 140 28 57 30 13

August 49 11 26 12 13

September 83 7.0 28 18 14

Annual 64 23 48 11 12
Statistical Summaries of Streamflow 43

06036650 Jefferson River near Three Forks, Mont.

Site Number 27

LOCATION.--Lat 45°53'52", long 111°35'45" (NAD 27), in SW1⁄4SW1⁄4NW1⁄4 sec.27, T.2 N., R.1 E., Broadwater County, Hydrologic Unit 10020005, on left bank 

50 ft downstream from bridge on U.S. Highway 10, 2.5 mi northwest of Three Forks, and at river mile 2,329.3.

DRAINAGE AREA.--9,532 mi2.

PERIOD OF RECORD.--October 1978 to current year (2002).

GAGE.--Water-stage recorder. Altitude of gage is 4,076.76 ft (NGVD 29).

REMARKS.--Some regulation by Ruby River Reservoir (station number 06020500) and Clark Canyon Reservoir (station number 06015300). Diversions for 

irrigation of about 390,000 acres upstream from station. U.S. Army Corps of Engineers satellite telemeter at station.

Magnitude and probability of annual low flow

based on 23 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 402 187 118 77 -- --

3 422 193 120 79 -- --

7 454 204 126 82 -- --

14 495 218 133 86 -- --

30 584 257 155 99 -- --

60 749 358 225 147 -- --

90 867 490 353 266 -- --

120 1,030 647 502 403 -- --

183 1,160 811 672 576 -- --

Magnitude and probability of seasonal low flow from

March-June based on 24 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1,030 661 510 405 -- --

3 1,080 705 549 440 -- --

7 1,160 782 620 505 -- --

14 1,290 949 799 689 -- --

30 1,490 1,150 994 872 -- --

Magnitude and probability of seasonal low flow from

November-February based on 23 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 649 450 367 309 -- --

3 711 512 430 373 -- --

7 822 624 540 479 -- --

14 947 724 624 550 -- --

30 1,080 849 747 670 -- --

Duration of daily mean flows based on 24 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

145 211 380 614 885 1,110 1,310 1,500

40% 30% 20% 15% 10% 5% 2% 1%

1,780 2,050 2,580 2,990 3,990 6,020 9,060 10,900

Magnitude and probability of annual high flow

based on 24 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 7,300 12,000 15,300 19,600 -- --

3 7,080 11,600 14,800 19,000 -- --

7 6,570 10,800 13,700 17,500 -- --

15 5,790 9,660 12,400 16,100 -- --

30 4,980 8,360 10,800 14,100 -- --

60 4,150 6,760 8,640 11,100 -- --

90 3,590 5,700 7,190 9,150 -- --

Magnitude and probability of seasonal low flow from

July-October based on 23 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 450 192 120 79 -- --

3 458 199 125 80 -- --

7 479 208 130 85 -- --

14 516 224 136 88 -- --

30 600 267 158 104 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 3,160 803 1,610 647 24

November 2,800 1,040 1,650 523 24

December 1,990 805 1,360 409 24

January 1,930 727 1,240 345 24

February 1,960 805 1,310 354 24

March 2,300 824 1,550 386 24

April 4,440 1,370 2,390 742 24

May 7,680 990 3,790 2,000 24

June 11,400 988 5,110 3,270 24

July 5,500 352 2,090 1,690 24

August 3,030 59 920 768 24

September 3,300 262 1,160 774 24

Annual 3,650 996 2,020 812 24
44 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06036905 Firehole River near West Yellowstone, Mont.

Site Number 28

LOCATION.--Lat 44°37'13", long 110°51'44" (NAD 27), Yellowstone National Park, Hydrologic Unit 10020007, on right bank 1.6 mi south of Madison Junction, 

12 mi east of West Yellowstone, and at river mile 1.8.

DRAINAGE AREA.--282 mi2.

PERIOD OF RECORD.--October 1983 to March 1996, September 2002 (reactivated).

GAGE.--Water-stage recorder. Altitude of gage is 7,050 ft (NGVD 29). 

REMARKS.--No regulation or diversions upstream from station. U.S. Geological Survey satellite telemeter at station. 

Magnitude and probability of annual low flow

based on 12 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 228 209 201 195 -- --

3 233 213 205 199 -- --

7 236 216 208 201 -- --

14 241 220 210 203 -- --

30 248 225 214 206 -- --

60 253 229 217 209 -- --

90 256 232 220 211 -- --

120 260 235 223 214 -- --

183 264 239 227 218 -- --

Magnitude and probability of seasonal low flow from

March-June based on 12 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 245 227 219 213 -- --

3 247 230 222 217 -- --

7 250 233 226 220 -- --

14 257 239 232 226 -- --

30 265 248 242 237 -- --

Magnitude and probability of seasonal low flow from

November-February based on 12 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 242 220 209 200 -- --

3 247 226 215 206 -- --

7 251 230 219 211 -- --

14 254 233 222 214 -- --

30 257 236 225 217 -- --

Duration of daily mean flows based on 12 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

192 194 199 209 228 246 265 289

40% 30% 20% 15% 10% 5% 2% 1%

314 339 364 376 439 522 691 755

Magnitude and probability of annual high flow

based on 12 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 733 933 1,070 -- -- --

3 685 889 1,030 -- -- --

7 638 829 965 -- -- --

15 586 748 862 -- -- --

30 539 674 763 -- -- --

60 470 562 619 -- -- --

90 419 492 538 -- -- --

Magnitude and probability of seasonal low flow from

July-October based on 12 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 252 223 209 199 -- --

3 254 224 210 200 -- --

7 255 226 212 202 -- --

14 258 228 214 204 -- --

30 260 230 216 207 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 356 225 283 42 13

November 348 227 278 40 13

December 316 220 269 33 13

January 298 222 264 26 13

February 304 226 263 25 13

March 336 239 272 27 13

April 398 276 334 35 12

May 612 367 493 86 12

June 756 273 435 150 12

July 415 221 300 60 12

August 371 212 275 48 12

September 368 217 275 44 12

Annual 399 264 311 40 12
Statistical Summaries of Streamflow 45

06037000 Gibbon River near West Yellowstone, Mont.

Site Number 29

LOCATION.--Lat 44°38'58", long 111°47'02" (NAD 27), Yellowstone National Park, Hydrologic Unit 10020007, on right bank, 0.6 mi downstream from Canyon 

Creek, 4.0 mi east of Madison Junction, 16.7 mi east of West Yellowstone, and at river mile 15.6. 

DRAINAGE AREA.--118 mi2. 

PERIOD OF RECORD.--June 1913 to December 1916 (incomplete record most years), October 1983 to March 1996 (discontinued). 

GAGE.--Water-stage recorder. Altitude of gage is 6,940 ft (NGVD 29, from topographic map). Nonrecording gage at site 0.1 mi downstream at different datum, 

1913-16. 

REMARKS.--No regulation or diversions upstream from station. 

Magnitude and probability of annual low flow

based on 13 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 66 61 59 57 -- --

3 67 63 60 58 -- --

7 69 64 61 59 -- --

14 71 66 63 61 -- --

30 73 68 65 62 -- --

60 76 71 68 65 -- --

90 78 73 69 66 -- --

120 80 74 70 67 -- --

183 83 76 72 69 -- --

Magnitude and probability of seasonal low flow from

March-June based on 13 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 71 65 61 58 -- --

3 73 67 63 60 -- --

7 74 68 64 61 -- --

14 76 69 65 62 -- --

30 78 71 67 64 -- --

Magnitude and probability of seasonal low flow from

November-February based on 16 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 68 63 60 58 -- --

3 70 64 62 60 -- --

7 71 66 64 62 -- --

14 73 68 66 63 -- --

30 75 70 67 65 -- --

Duration of daily mean flows based on 13 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

53 60 67 70 75 80 85 90

40% 30% 20% 15% 10% 5% 2% 1%

100 115 133 159 185 262 378 529

Magnitude and probability of annual high flow

based on 13 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 519 837 1,060 1,350 -- --

3 481 766 960 1,210 -- --

7 435 680 844 1,050 -- --

15 373 565 693 851 -- --

30 314 455 544 651 -- --

60 244 332 387 454 -- --

90 207 272 311 358 -- --

Magnitude and probability of seasonal low flow from

July-October based on 15 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 78 70 67 64 -- --

3 79 71 67 64 -- --

7 79 72 68 66 -- --

14 80 73 70 68 -- --

30 83 75 71 69 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 128 69 93 17 16

November 115 70 87 12 16

December 104 67 83 9.1 16

January 95 64 80 7.5 16

February 95 62 76 7.6 16

March 112 62 81 12 16

April 230 96 136 36 15

May 532 123 289 123 13

June 362 99 193 86 13

July 216 73 128 39 15

August 154 66 101 24 16

September 123 66 93 16 16

Annual 159 82 118 21 13
46 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06037500 Madison River near West Yellowstone, Mont.

Site Number 30

LOCATION.--Lat 44°39'25", long 111°04'03" (NAD 27), in NE1⁄4NW1⁄4SW1⁄4 sec.36, T.13 S., R.5 E., Gallatin County, Hydrologic Unit 10020007, Yellowstone 

National Park, on left bank 0.7 mi downstream from Montana-Wyoming State line, 1.5 mi east of West Yellowstone, 16.4 mi downstream from Gibbon River, 

and at river mile 132.7.

DRAINAGE AREA.--420 mi2.

PERIOD OF RECORD.--June 1913 to December 1917, July 1918 to October 1921, June 1922 to September 1973, August 1983 to September 1986, October 1988 

to current year (2002). Monthly discharge only for some periods, published in WSP 1309.

GAGE.--Water-stage recorder. Altitude of gage is 6,650 ft (NGVD 29). Prior to Oct. 20, 1918, nonrecording gage, and Oct. 20, 1918, to June 29, 1930, 

nonrecording gage or water-stage recorder at sites 2.5 mi upstream at different datums. Supplementary nonrecording gage at site 0.3 mi downstream at different 

datum used at time during 1927-30.

REMARKS.--No regulation or diversions upstream from station. U.S. Geological Survey satellite telemeter at station. 

Magnitude and probability of annual low flow

based on 71 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 339 300 281 267 252 242

3 346 308 290 276 261 252

7 356 318 299 285 269 259

14 363 324 304 289 273 262

30 372 331 311 295 279 268

60 387 342 320 302 283 271

90 396 349 326 308 289 276

120 401 353 330 311 292 279

183 408 357 334 315 295 283

Magnitude and probability of seasonal low flow from

March-June based on 75 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 375 337 319 304 287 277

3 379 341 323 308 291 280

7 384 346 327 312 296 286

14 391 352 333 317 301 290

30 400 361 342 328 313 303

Magnitude and probability of seasonal low flow from

November-February based on 75 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 350 307 288 272 256 246

3 359 318 299 284 269 260

7 368 329 311 298 284 275

14 377 337 318 304 289 280

30 385 344 325 310 295 286

Duration of daily mean flows based on 75 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

274 278 292 314 358 395 424 453

40% 30% 20% 15% 10% 5% 2% 1%

482 512 590 671 752 1,000 1,300 1,470

Magnitude and probability of annual high flow

based on 75 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 1,290 1,660 1,900 2,200 2,420 2,640

3 1,220 1,570 1,810 2,110 2,340 2,570

7 1,150 1,490 1,710 1,990 2,200 2,410

15 1,060 1,370 1,570 1,820 2,000 2,170

30 968 1,240 1,410 1,630 1,790 1,940

60 827 1,030 1,160 1,320 1,430 1,540

90 723 891 994 1,120 1,210 1,300

Magnitude and probability of seasonal low flow from

July-October based on 75 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 377 326 304 288 271 261

3 380 328 305 288 271 261

7 384 330 307 290 273 262

14 388 334 311 294 277 266

30 397 341 317 299 281 270

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 710 297 434 84 76

November 697 297 425 71 76

December 641 304 416 65 75

January 586 304 405 61 75

February 572 303 399 52 75

March 539 313 406 52 75

April 671 369 496 78 75

May 1,720 388 851 218 75

June 1,480 341 815 291 76

July 917 282 500 134 78

August 759 273 434 92 79

September 704 282 427 86 79

Annual 789 337 499 86 75
Statistical Summaries of Streamflow 47

06038500 Madison River below Hebgen Lake, near Grayling, Mont.

Site Number 31

LOCATION.--Lat 44°52'00", long 111°20'15" (NAD 27), NE1⁄4NE1⁄4NE1⁄4 sec.22, T.11 S., R.3 E., Gallatin County, Hydrologic Unit 10020007, Gallatin National 

Forest, on right bank 1,500 ft downstream from Hebgen Dam, 8 mi northwest of Grayling, 17 mi upstream from West Fork, and at river mile 108.8.

DRAINAGE AREA.--905 mi2.

PERIOD OF RECORD.--June 1909 to current year (2002). Prior to October 1938 adjusted runoff only, published in WSP 1309. Prior to October 1949, published 

as "below Hebgen Reservoir."

REVISED RECORDS.--WSP 1509: 1948. WSP 1559: Drainage area. WSP 1629: 1943. WSP 1709: 1959. WSP 1729: 1943.

GAGE.--Water-stage recorder. Altitude of gage is 6,448.47 ft (NGVD 29, after 1959 earthquake). Prior to July 13, 1943, nonrecording gage in stilling well.

REMARKS.--Flow completely regulated by Hebgen Lake (station number 06038000). Diversions for irrigation of about 1,100 acres upstream from station. 

Bureau of Reclamation satellite telemeter at station. 

Magnitude and probability of annual low flow

based on 63 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 281 106 56 32 15 9.1

3 295 112 60 34 16 9.7

7 313 121 65 37 18 11

14 346 138 76 44 22 13

30 443 192 108 62 31 18

60 550 321 231 172 120 93

90 652 433 338 271 206 170

120 814 574 463 380 299 251

183 918 713 617 543 468 421

Magnitude and probability of seasonal low flow from

March-June based on 64 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 301 109 58 32 16 9.3

3 314 115 61 34 17 9.9

7 333 125 67 37 18 11

14 370 143 78 44 22 13

30 492 213 120 69 34 20

Magnitude and probability of seasonal low flow from

November-February based on 63 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 729 517 401 312 225 176

3 749 541 423 330 237 185

7 773 574 453 355 257 201

14 797 605 483 382 278 218

30 844 662 533 422 305 237

Duration of daily mean flows based on 64 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

79 169 303 499 661 791 889 986

40% 30% 20% 15% 10% 5% 2% 1%

1,080 1,250 1,440 1,580 1,850 2,110 2,620 2,940

Magnitude and probability of annual high flow

based on 64 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 2,390 3,000 3,380 3,840 4,170 4,480

3 2,330 2,920 3,290 3,740 4,070 4,390

7 2,250 2,820 3,160 3,580 3,880 4,170

15 2,120 2,620 2,920 3,270 3,510 3,750

30 1,950 2,360 2,600 2,860 3,040 3,210

60 1,660 2,000 2,190 2,410 2,560 2,700

90 1,450 1,700 1,850 2,020 2,130 2,230

Magnitude and probability of seasonal low flow from

July-October based on 63 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 676 432 306 215 135 94

3 720 473 335 235 145 100

7 774 516 364 252 153 104

14 846 586 415 285 169 112

30 899 671 535 426 315 251

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 2,480 215 1,360 478 64

November 2,540 501 1,400 461 64

December 2,840 410 986 310 64

January 1,410 180 900 212 64

February 1,900 181 839 243 64

March 1,570 291 838 298 64

April 2,340 217 929 502 64

May 2,490 46 857 556 64

June 2,940 96 1,270 705 64

July 2,060 503 1,030 275 64

August 1,720 662 1,080 219 64

September 1,690 368 1,140 278 64

Annual 1,560 506 1,050 190 64
48 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06038800 Madison River at Kirby Ranch, near Cameron, Mont.

Site Number 32

LOCATION.--Lat 44°53'22", long 111°34'46" (NAD 27), in NE1⁄4NE1⁄4SE1⁄4 sec.10, T.11 S., R.1 E., Madison County, Hydrologic Unit 10020007, 75 ft upstream 

from county bridge, 0.2 mi upstream from West Fork Madison River, and 22 mi south of Cameron, and at river mile 89.8.

DRAINAGE AREA.--1,065 mi2.

PERIOD OF RECORD.--September 1959 to September 1963, May 1978 to September 1994 (seasonal records only), October 1995 to current year (2002).

GAGE.--Water-stage recorder. Altitude of gage is 5,860 ft (NGVD 29). Aug. 31, 1959, to Oct. 2, 1959, nonrecording gage 75 ft downstream at datum 0.96 ft 

lower. Oct. 3, 1959, to September 1963, water-stage recorder at present site and datum. May 1978 to September 1994, nonrecording gage 75 ft downstream 

at present datum.

REMARKS.--Flow regulated by Hebgen Lake (station number 06038000). Diversions for irrigation of about 1,500 acres upstream from station. U.S. Geological 

Survey satellite telemeter at station.

Magnitude and probability of annual low flow

based on 10 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 734 429 310 232 -- --

3 738 433 313 234 -- --

7 744 440 320 240 -- --

14 761 463 343 262 -- --

30 811 523 401 316 -- --

60 879 596 469 378 -- --

90 947 665 537 443 -- --

120 1,040 743 604 502 -- --

183 1,130 841 709 610 -- --

Magnitude and probability of seasonal low flow from

March-June based on 12 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 736 432 314 234 -- --

3 740 436 317 237 -- --

7 747 443 325 244 -- --

14 765 466 346 265 -- --

30 814 529 408 320 -- --

Magnitude and probability of seasonal low flow from

November-February based on 12 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 923 720 624 550 -- --

3 928 724 627 552 -- --

7 937 732 634 559 -- --

14 945 739 641 566 -- --

30 967 772 681 612 -- --

Duration of daily mean flows based on 12 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

346 423 564 683 849 980 1,110 1,230

40% 30% 20% 15% 10% 5% 2% 1%

1,350 1,470 1,800 1,990 2,180 2,880 3,740 4,160

Magnitude and probability of annual high flow

based on 12 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 3,080 4,200 4,800 -- -- --

3 3,000 4,100 4,690 -- -- --

7 2,900 3,970 4,570 -- -- --

15 2,780 3,860 4,450 -- -- --

30 2,550 3,530 4,090 -- -- --

60 2,160 2,900 3,310 -- -- --

90 1,900 2,470 2,800 -- -- --

Magnitude and probability of seasonal low flow from

July-October based on 10 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 980 804 715 644 -- --

3 1,000 828 739 667 -- --

7 1,020 860 775 706 -- --

14 1,070 900 810 736 -- --

30 1,100 914 818 741 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 2,570 938 1,610 581 12

November 2,780 736 1,610 588 12

December 3,000 739 1,240 599 12

January 1,450 737 1,060 256 12

February 1,520 626 1,030 302 12

March 1,610 525 1,040 345 12

April 1,530 370 1,010 420 12

May 2,860 445 1,380 611 29

June 3,860 619 1,880 943 29

July 2,120 716 1,330 387 29

August 1,670 734 1,140 238 13

September 1,570 732 1,180 247 14

Annual 1,900 733 1,320 325 12
Statistical Summaries of Streamflow 49

06040000 Madison River near Cameron, Mont.

Site Number 33

LOCATION.--Lat 45°14'00", long 111°45'00" (NAD 27), at center of south line of sec.8, T.7 S., R.1 W., Madison County, on right bank 30 ft downstream from 

Varney Bridge, 1.8 mi downstream from Wigwam Creek, and 4.1 mi northwest of Cameron.

DRAINAGE AREA.--1,669 mi2.

PERIOD OF RECORD.--13 years. October 1951 to September 1958, August 1959 to September 1963, April 1968 to September 1970 (discontinued).

GAGE.--Water-stage recorder. Altitude of gage is 5,135 ft (NGVD 29, from topographic map). 

REMARKS.--Flow regulated by Hebgen Lake (station number 06038000). Diversions for irrigation of about 5,300 acres upstream from station.

Magnitude and probability of annual low flow

based on 10 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 584 426 357 307 -- --

3 643 494 426 376 -- --

7 684 523 448 391 -- --

14 735 558 469 401 -- --

30 791 589 488 409 -- --

60 853 639 534 453 -- --

90 917 726 634 562 -- --

120 1,140 930 815 720 -- --

183 1,280 1,040 904 791 -- --

Magnitude and probability of seasonal low flow from

March-June based on 13 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 635 489 426 380 -- --

3 660 505 437 387 -- --

7 696 528 453 399 -- --

14 745 562 470 408 -- --

30 811 592 491 413 -- --

Magnitude and probability of seasonal low flow from

November-February based on 12 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 816 469 370 310 -- --

3 836 723 669 626 -- --

7 870 748 691 646 -- --

14 883 765 711 670 -- --

30 923 823 781 750 -- --

Duration of daily mean flows based on 12 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

416 472 604 770 887 1,010 1,130 1,270

40% 30% 20% 15% 10% 5% 2% 1%

1,410 1,610 1,930 2,090 2,400 3,030 4,030 4,750

Magnitude and probability of annual high flow

based on 12 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 4,190 5,760 6,630 -- -- --

3 4,010 5,370 6,090 -- -- --

7 3,750 4,970 5,610 -- -- --

15 3,300 4,350 4,930 -- -- --

30 2,990 3,790 4,190 -- -- --

60 2,480 3,010 3,240 -- -- --

90 2,050 2,550 2,820 -- -- --

Magnitude and probability of seasonal low flow from

July-October based on 11 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 995 797 697 617 -- --

3 1,010 818 720 641 -- --

7 1,090 901 798 714 -- --

14 1,180 1,000 912 835 -- --

30 1,250 1,050 944 854 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 2,640 1,140 1,970 442 12

November 3,130 974 1,850 586 12

December 3,030 957 1,290 555 13

January 1,420 859 1,090 177 13

February 1,460 762 1,010 223 13

March 1,640 620 978 330 13

April 1,790 425 999 423 14

May 3,780 677 1,420 798 14

June 4,560 1,000 2,570 1,070 14

July 2,020 884 1,490 342 14

August 1,730 876 1,330 232 14

September 1,830 897 1,440 253 15

Annual 1,740 891 1,410 234 12
50 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06040300 Jack Creek near Ennis, Mont.

Site Number 34

LOCATION.--Lat 45°21'22", long 111°34'55" (NAD 27), in NE1⁄4NW1⁄4SE1⁄4 sec.34, T.5 S., R.l E., Madison County, Hydrologic Unit 10020007, Beaverhead 

National Forest, on left bank 800 ft upstream from bridge at forest boundary, 8.8 mi east of Ennis, and at river mile 6.5. 

DRAINAGE AREA.--51.5 mi2. 

PERIOD OF RECORD.--September 1973 to September 1986; April 1991 to September 1992, seasonal records only (discontinued). 

GAGE.--Water-stage recorder. Altitude of gage is 5,470 ft (NGVD 29, from topographic map). 

REMARKS.--No known regulation or diversion upstream from station. 

Magnitude and probability of annual low flow

based on 12 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 8.8 7.3 6.6 6.1 -- --

3 9.9 8.7 8.2 7.8 -- --

7 11 9.8 9.3 8.9 -- --

14 12 10 9.8 9.3 -- --

30 12 11 10 9.6 -- --

60 13 12 11 11 -- --

90 15 13 13 12 -- --

120 16 14 13 13 -- --

183 20 17 16 15 -- --

Magnitude and probability of seasonal low flow from

March-June based on 13 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 12 9.9 9.0 8.3 -- --

3 12 11 9.8 9.2 -- --

7 13 11 10 9.6 -- --

14 13 11 10 9.8 -- --

30 14 12 11 10 -- --

Magnitude and probability of seasonal low flow from

November-February based on 13 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 9.0 7.4 6.7 6.2 -- --

3 10 8.9 8.3 7.8 -- --

7 11 10 9.6 9.1 -- --

14 12 11 10 9.8 -- --

30 13 12 11 10 -- --

Duration of daily mean flows based on 13 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

9.3 11 12 13 15 18 21 26

40% 30% 20% 15% 10% 5% 2% 1%

32 44 66 89 123 179 244 270

Magnitude and probability of annual high flow

based on 13 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 261 364 431 515 -- --

3 243 336 394 463 -- --

7 222 304 353 410 -- --

15 202 267 303 343 -- --

30 182 233 259 285 -- --

60 148 188 210 233 -- --

90 121 152 168 185 -- --

Magnitude and probability of seasonal low flow from

July-October based on 13 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 20 16 14 13 -- --

3 21 17 16 15 -- --

7 22 19 17 17 -- --

14 22 19 18 17 -- --

30 24 20 19 18 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 35 18 24 5.2 14

November 28 15 20 4.0 13

December 20 13 17 2.1 13

January 18 11 15 1.9 13

February 16 11 13 1.6 13

March 18 9.9 14 2.5 13

April 44 13 33 9.2 15

May 175 37 111 40 15

June 268 72 163 58 15

July 136 35 77 31 15

August 56 26 39 10 15

September 39 22 29 5.9 16

Annual 65 33 47 10 13
Statistical Summaries of Streamflow 51

06041000 Madison River below Ennis Lake, near McAllister, Mont.

Site Number 35

LOCATION.--Lat 45°29'25", long 111°38'00" (NAD 27), in SW1⁄4SE1⁄4NW1⁄4 sec.17, T.4 S., R.1 E., Madison County, Hydrologic Unit 10020007, on right bank 

500 ft downstream from Madison powerplant, 1.5 mi downstream from Ennis Lake, 5.7 mi northeast of McAllister, and at river mile 38.8.

DRAINAGE AREA.--2,186 mi2.

PERIOD OF RECORD.--October 1901 to December 1905, October 1906 to current year (2002). Prior to October 1938 adjusted monthly runoff only, published 

in WSP 1309. Published as "below Madison Reservoir," 1938-49. Records published as "near Red Bluff," 1890-94 and as "near Norris," 1910 are not 

equivalent and are published as "near Norris" in WSP 1309.

REVISED RECORDS.--WSP 1559: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 4,689.03 ft (NGVD 29, levels by U.S. Army Corps of Engineers). Prior to May 7, 1941, nonrecording gage in 

wooden stilling well at present site at different datum. May 7, 1941, to Jan. 13, 1945, nonrecording gages in concrete stilling well at present site and datum.

REMARKS.--Flow regulated by Hebgen Lake (station number 06038000) and Ennis Lake (station number 06040500). Diversions for irrigation of about 

23,000 acres upstream from station. U.S. Geological Survey satellite telemeter at station. 

Magnitude and probability of annual low flow

based on 50 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 966 718 571 453 333 263

3 1,020 778 633 513 387 313

7 1,070 852 731 631 523 455

14 1,130 913 791 692 585 518

30 1,200 992 880 789 690 627

60 1,270 1,080 984 908 827 774

90 1,350 1,170 1,070 998 918 865

120 1,550 1,320 1,210 1,110 1,000 935

183 1,640 1,400 1,270 1,170 1,050 976

Magnitude and probability of seasonal low flow from

March-June based on 51 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1,110 849 708 594 476 404

3 1,130 885 754 651 541 473

7 1,180 959 849 762 669 610

14 1,240 1,010 895 805 708 647

30 1,330 1,070 952 856 756 693

Magnitude and probability of seasonal low flow from

November-February based on 50 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 968 820 751 699 645 611

3 1,020 882 815 764 709 675

7 1,120 963 884 821 752 708

14 1,200 1,040 957 894 826 782

30 1,290 1,140 1,060 1,000 938 898

Duration of daily mean flows based on 51 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

765 802 911 1,090 1,230 1,350 1,480 1,650

40% 30% 20% 15% 10% 5% 2% 1%

1,830 2,020 2,200 2,510 2,830 3,360 4,340 5,420

Magnitude and probability of annual high flow

based on 51 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 4,600 6,190 7,180 8,350 9,170 9,960

3 4,410 5,960 6,920 8,080 8,910 9,710

7 4,120 5,570 6,480 7,580 8,370 9,140

15 3,800 5,100 5,910 6,880 7,570 8,230

30 3,420 4,480 5,110 5,860 6,380 6,880

60 2,900 3,650 4,090 4,600 4,950 5,280

90 2,520 3,140 3,510 3,950 4,260 4,550

Magnitude and probability of seasonal low flow from

July-October based on 50 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1,300 1,020 859 693 532 403

3 1,340 1,070 892 736 581 448

7 1,380 1,130 952 795 620 512

14 1,420 1,160 992 845 683 580

30 1,450 1,200 1,050 928 793 706

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 2,960 1,120 2,090 445 51

November 3,320 1,300 2,180 421 51

December 3,240 1,200 1,540 313 51

January 2,060 1,040 1,400 227 51

February 1,960 1,040 1,410 213 51

March 2,050 911 1,460 282 51

April 2,760 746 1,570 479 51

May 4,190 859 2,090 800 51

June 6,140 1,120 3,070 1,300 51

July 3,450 972 1,900 642 51

August 2,340 1,040 1,520 299 51

September 2,300 1,120 1,670 336 51

Annual 2,530 1,140 1,820 320 51
52 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06042500 Madison River near Three Forks, Mont.

Site Number 36

LOCATION.--Lat 45°49'25", long 111°29'50" (NAD 27), in SW1⁄4NE1⁄4 sec.20 T.1 N., R.2 E., Gallatin County, 5 mi south of Three Forks and 8 mi upstream from 

confluence with Jefferson and Gallatin Rivers.

DRAINAGE AREA.--2,511 mi2.

PERIOD OF RECORD.--16 years (1893-96, 1928-32, 1941-50).

GAGE.--Water-stage recorder. Altitude of gage is 4,160 ft (NGVD 29, from topographic map). Aug. 24, 1893, to May 1, 1897, slope gage, and Nov. 8, 1928, to 

Sept. 30, 1932, wire-weight gage at different datums at site 6 miles downstream.

REMARKS.--Diversions for irrigation of about 31,000 acres upstream from station. Flow regulated by Hebgen Lake (station number 06038000) since 1915 and 

Ennis Lake (station number 06040500) since 1900.

Magnitude and probability of annual low flow

based on 12 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 736 568 489 428 -- --

3 764 592 510 448 -- --

7 829 654 570 504 -- --

14 882 721 642 581 -- --

30 977 788 688 608 -- --

60 1,130 917 804 713 -- --

90 1,240 1,030 907 806 -- --

120 1,350 1,140 989 858 -- --

183 1,440 1,210 1,060 919 -- --

Magnitude and probability of seasonal low flow from

March-June based on 13 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 807 658 599 557 -- --

3 867 689 616 565 -- --

7 973 765 678 615 -- --

14 1,050 851 769 712 -- --

30 1,180 928 826 754 -- --

Magnitude and probability of seasonal low flow from

November-February based on 12 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 956 738 612 511 -- --

3 998 776 647 542 -- --

7 1,040 830 711 613 -- --

14 1,090 919 826 750 -- --

30 1,170 1,020 950 889 -- --

Duration of daily mean flows based on 13 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

590 664 798 912 1,120 1,230 1,350 1,460

40% 30% 20% 15% 10% 5% 2% 1%

1,630 1,840 2,050 2,150 2,490 3,030 4,000 4,690

Magnitude and probability of annual high flow

based on 13 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 4,100 5,710 6,800 8,190 -- --

3 3,900 5,400 6,410 7,700 -- --

7 3,610 4,920 5,790 6,900 -- --

15 3,340 4,390 5,030 5,780 -- --

30 2,930 3,840 4,410 5,120 -- --

60 2,450 3,100 3,510 4,030 -- --

90 2,210 2,680 2,970 3,310 -- --

Magnitude and probability of seasonal low flow from

July-October based on 12 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 912 708 605 523 -- --

3 953 735 622 533 -- --

7 1,020 786 660 561 -- --

14 1,090 839 704 597 -- --

30 1,210 926 765 635 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 1,820 826 1,300 291 13

November 1,580 884 1,320 195 13

December 1,760 1,000 1,500 219 13

January 2,100 1,100 1,510 266 13

February 2,500 898 1,490 501 13

March 2,000 834 1,440 389 13

April 3,100 778 1,670 694 13

May 2,910 972 1,700 479 13

June 5,580 886 2,670 1,210 13

July 2,560 783 1,600 442 13

August 3,030 884 1,450 536 13

September 2,740 547 1,420 504 13

Annual 1,980 1,040 1,590 275 13
Statistical Summaries of Streamflow 53

06043500 Gallatin River near Gallatin Gateway, Mont.

Site Number 37

LOCATION.--Lat 45°29'51", long 111°16'11" (NAD 27), in SE1⁄4SE1⁄4SE1⁄4 sec.7, T.4 S., R.4 E., Gallatin County, Hydrologic Unit 10020008, on left bank 0.3 mi 

downstream from Spanish Creek, 7.3 mi south of Gallatin Gateway and at river mile 47.7. 

DRAINAGE AREA.--825 mi2.

PERIOD OF RECORD.--August 1889 to September 1894, June 1930 to September 1969, annual maximum, water years 1970-71, October 1971 to September 

1981, October 1984 to current year (2002). Monthly discharge only for some periods, published in WSP 1309. Published as "West Gallatin River near 

Bozeman," 1889-94.

REVISED RECORDS.--WSP 1389: 1892(M), 1893-94. WSP 1559: Drainage area. WDR MT-85-1 (M), WDR MT-02-1: 1970-71 (M).

GAGE.--Water-stage recorder. Altitude of gage is 5,167.67 ft (NGVD 29). Prior to Oct. 20, 1932, nonrecording gages at several different sites and datums within 

0.8 mi of present site.

REMARKS.--Diversions for irrigation of about 1,400 acres upstream from station. U.S. Geological Survey satellite telemeter at station.

Magnitude and probability of annual low flow

based on 65 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 222 195 183 174 165 160

3 233 205 192 183 173 167

7 247 218 204 194 183 177

14 257 228 215 205 194 187

30 273 242 228 217 205 197

60 289 256 240 228 215 207

90 296 261 245 233 221 213

120 313 274 257 244 230 222

183 362 310 286 268 250 238

Magnitude and probability of seasonal low flow from

March-June based on 67 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 265 230 213 199 185 176

3 273 237 220 207 192 183

7 280 244 227 213 199 189

14 288 251 233 219 204 194

30 301 261 243 229 214 205

Magnitude and probability of seasonal low flow from

November-February based on 67 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 229 197 184 175 166 160

3 240 207 193 184 174 168

7 256 222 206 195 184 178

14 270 235 219 207 195 188

30 284 248 232 219 206 198

Duration of daily mean flows based on 67 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

196 204 226 264 303 338 374 437

40% 30% 20% 15% 10% 5% 2% 1%

506 654 1,000 1,410 2,050 3,010 4,100 4,980

Magnitude and probability of annual high flow

based on 67 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 4,620 5,920 6,650 7,460 7,990 8,470

3 4,310 5,580 6,320 7,150 7,710 8,230

7 3,960 5,170 5,880 6,690 7,250 7,770

15 3,590 4,680 5,300 5,990 6,460 6,880

30 3,160 4,040 4,530 5,040 5,380 5,680

60 2,500 3,150 3,510 3,910 4,160 4,390

90 2,000 2,500 2,780 3,090 3,290 3,470

Magnitude and probability of seasonal low flow from

July-October based on 66 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 379 318 289 267 244 229

3 393 330 299 275 249 233

7 403 337 306 281 255 238

14 411 343 310 285 259 242

30 425 351 317 291 264 247

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 721 238 447 102 67

November 589 247 375 74 68

December 488 214 313 56 67

January 428 200 302 51 67

February 407 220 299 45 67

March 465 206 307 52 67

April 899 263 503 149 67

May 3,140 873 1,790 541 67

June 5,110 643 2,910 1,010 68

July 3,670 345 1,270 576 68

August 1,160 270 602 170 68

September 788 233 483 112 68

Annual 1,180 408 802 174 67
54 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06048000 East Gallatin River at Bozeman, Mont.

Site Number 38

LOCATION.--Lat 45°42'00", long 111°01'45" (NAD 27), near center of south line of sec.31, T.1 S., R.6 E., Gallatin County, on left bank 100 ft upstream from 

highway bridge, 500 ft downstream from Bozeman Creek, 0.5 mi upstream from Bridger Creek, and 0.5 mi north of Bozeman.

DRAINAGE AREA.--148 mi2.

PERIOD OF RECORD.--22 years. August 1939 to September 1961 (discontinued).

REVISED RECORDS.--WSP 1559: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 4,701.6 ft (NGVD 29). 

REMARKS.--Diversions for irrigation of about 4,000 acres upstream from station. Some diurnal fluctuation caused by mill upstream from station.

Magnitude and probability of annual low flow

based on 21 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 22 17 15 14 -- --

3 23 18 16 14 -- --

7 25 21 19 17 -- --

14 29 25 23 21 -- --

30 33 28 25 23 -- --

60 37 32 30 29 -- --

90 40 36 34 32 -- --

120 43 38 36 34 -- --

183 45 39 37 35 -- --

Magnitude and probability of seasonal low flow from

March-June based on 22 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 35 26 21 17 -- --

3 36 27 22 18 -- --

7 38 30 25 21 -- --

14 42 34 30 26 -- --

30 55 43 38 35 -- --

Magnitude and probability of seasonal low flow from

November-February based on 22 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 24 19 17 15 -- --

3 26 20 17 15 -- --

7 28 23 20 18 -- --

14 32 27 24 22 -- --

30 36 31 27 24 -- --

Duration of daily mean flows based on 22 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

20 23 26 32 37 42 46 53

40% 30% 20% 15% 10% 5% 2% 1%

60 70 107 145 196 272 378 482

Magnitude and probability of annual high flow

based on 22 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 441 674 845 1,080 -- --

3 392 593 743 950 -- --

7 342 502 619 780 -- --

15 304 426 509 617 -- --

30 261 357 418 493 -- --

60 217 301 356 425 -- --

90 185 252 297 352 -- --

Magnitude and probability of seasonal low flow from

July-October based on 21 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 30 24 21 19 -- --

3 32 25 22 20 -- --

7 33 26 23 21 -- --

14 35 28 25 23 -- --

30 37 30 27 24 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 86 30 52 12 22

November 75 31 50 11 22

December 75 28 46 10 22

January 64 23 39 8.4 22

February 56 28 42 7.8 22

March 124 26 60 20 22

April 329 68 158 77 22

May 529 90 236 108 22

June 343 46 178 83 22

July 134 23 63 24 22

August 96 19 42 17 22

September 83 32 49 12 23

Annual 156 50 85 24 22
Statistical Summaries of Streamflow 55

06048500 Bridger Creek near Bozeman, Mont.

Site Number 39

LOCATION.--Lat 45°42'20", long 110°57'40" (NAD 27), in NE1⁄4NE1⁄4SE1⁄4 sec.34, T.1 S., R.1 E., Gallatin County, Hydrologic Unit 10020008, on right bank, 

3.5 mi northeast of Bozeman, and at river mile 3.6.

DRAINAGE AREA.--62.5 mi2. 

PERIOD OF RECORD.--October 1945 to September 1969, May 1971 to June 1972, March 1987 to August 1987 (discontinued). Monthly discharge only for some 

periods, published in WSP 1309. 

REVISED RECORDS.--WSP 1309: 1948. WSP 1559: Drainage area. 

GAGE.--Water-stage recorder. Altitude of gage is 4,960 ft (NGVD 29, from topographic map). Prior to June 28, 1946, nonrecording gage at present site and 

datum. 

REMARKS.--Diversions for irrigation of about 1,200 acres upstream from station.

Magnitude and probability of annual low flow

based on 23 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 3.4 2.2 1.7 1.4 -- --

3 3.8 2.5 1.9 1.6 -- --

7 4.2 2.9 2.3 1.9 -- --

14 4.7 3.4 2.9 2.6 -- --

30 5.5 3.9 3.3 2.9 -- --

60 6.4 4.7 4.0 3.5 -- --

90 7.1 5.2 4.5 4.0 -- --

120 7.8 5.8 5.0 4.5 -- --

183 8.4 6.3 5.6 5.0 -- --

Magnitude and probability of seasonal low flow from

March-June based on 26 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 5.9 3.5 2.7 2.2 1.7 --

3 6.2 3.7 2.9 2.3 1.8 --

7 6.7 4.1 3.2 2.7 2.2 --

14 7.3 4.9 4.2 3.7 3.3 --

30 12 7.0 5.4 4.4 3.4 --

Magnitude and probability of seasonal low flow from

November-February based on 24 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 3.5 2.2 1.9 1.6 -- --

3 3.8 2.5 2.1 1.8 -- --

7 4.3 3.0 2.5 2.2 -- --

14 5.0 3.6 3.1 2.7 -- --

30 5.7 4.2 3.6 3.2 -- --

Duration of daily mean flows based on 24 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

2.9 3.6 4.4 5.3 6.7 8.1 10 13

40% 30% 20% 15% 10% 5% 2% 1%

17 28 53 74 109 170 249 316

Magnitude and probability of annual high flow

based on 24 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 260 408 518 668 -- --

3 244 378 475 607 -- --

7 223 334 411 512 -- --

15 193 279 336 408 -- --

30 163 230 272 325 -- --

60 129 181 214 255 -- --

90 105 144 169 199 -- --

Magnitude and probability of seasonal low flow from

July-October based on 24 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 6.7 4.3 3.5 2.8 -- --

3 7.0 4.6 3.6 3.0 -- --

7 7.3 4.9 3.9 3.3 -- --

14 7.8 5.3 4.3 3.7 -- --

30 8.3 5.9 5.1 4.5 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 22 6.1 11 4.3 25

November 22 5.8 10 3.8 25

December 17 4.1 8.7 4.0 25

January 15 3.0 7.2 3.4 25

February 34 2.8 8.9 6.4 25

March 45 2.8 15 11 26

April 148 20 64 35 26

May 333 45 154 72 27

June 240 32 101 56 27

July 84 11 31 16 27

August 38 3.9 13 7.3 26

September 29 5.2 11 5.9 25

Annual 70 16 37 14 24
56 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06050000 Hyalite Creek at Hyalite Ranger Station, near Bozeman, Mont.

Site Number 40

LOCATION.--Lat 45°33'42", long 111°04'12" (NAD 27), in NW1⁄4NW1⁄4SE1⁄4 sec.23, T.3 S., R.5 E., Gallatin County, Hydrologic Unit 10020008, Gallatin National 

Forest, on right bank 0.8 mi south of former Hyalite Ranger Station, 7.3 mi south of Bozeman, and at river mile 20.8. 

DRAlNAGE AREA.--48.2 m2. 

PERIOD OF RECORD.--August 1895 to October 1896, calendar year 1897 (discharge measurements only), April 1898 to October 1899, June to October 1900, 

May to September 1902, calendar year 1903 (discharge measurements only), September to December 1904, September 1934 to September 1994, October 1994 

to September 1995 (seasonal records only, discontinued). Monthly discharge only for some periods, published in WSP 1309. Prior to 1934, published as 

"Middle Creek near Bozeman."

REVISED RECORDS.--WSP 1509: 1902, 1939(M). WSP 1559: Drainage area. WSP 1709: 1953, 1956-57. 

GAGE.--Water-stage recorder. Altitude of gage is 5,539.6 ft (NGVD 29). Prior to September 1934, nonrecording gages at two sites 0.5 mi upstream at different 

datums. Sept. 13, 1934, to May 13, 1948, water-stage recorder at site 0.3 mi downstream at different datum.

REMARKS.--Flow regulated by Middle Creek Reservoir (station 06049500) after March 1951.

Unregulated streamflow period

Magnitude and probability of annual low flow

based on 16 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 12 9.8 8.4 7.3 -- --

3 12 10 8.6 7.4 -- --

7 12 11 10 8.8 -- --

14 14 12 11 9.6 -- --

30 15 13 12 11 -- --

60 18 15 14 13 -- --

90 20 16 15 14 -- --

120 21 18 16 15 -- --

183 25 21 18 17 -- --

Magnitude and probability of seasonal low flow from

March-June based on 17 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 13 11 10 9.4 -- --

3 13 11 10 9.5 -- --

7 14 11 10 9.6 -- --

14 15 12 11 10 -- --

30 16 14 12 11 -- --

Magnitude and probability of seasonal low flow from

November-February based on 17 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 13 11 9.7 8.8 -- --

3 13 11 9.9 9.0 -- --

7 13 11 10 9.2 -- --

14 14 12 11 9.7 -- --

30 16 13 12 11 -- --

Duration of daily mean flows based on 17 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

9.9 11 13 15 19 22 27 32

40% 30% 20% 15% 10% 5% 2% 1%

40 53 87 118 158 213 264 327

Magnitude and probability of annual high flow

based on 17 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 291 378 438 515 -- --

3 268 349 405 478 -- --

7 246 317 365 426 -- --

15 214 278 323 383 -- --

30 191 245 283 334 -- --

60 168 208 234 267 -- --

90 140 174 196 225 -- --

Magnitude and probability of seasonal low flow from

July-October based on 17 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 27 18 13 9.6 -- --

3 28 18 13 9.9 -- --

7 28 21 19 18 -- --

14 29 23 21 19 -- --

30 30 24 22 20 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 53 19 34 10 20

November 39 17 27 7.1 18

December 31 12 22 6.0 18

January 29 9.7 19 4.7 17

February 25 12 17 4.0 17

March 24 11 17 3.7 17

April 122 18 45 28 17

May 290 99 141 45 18

June 270 89 192 53 19

July 160 30 97 37 19

August 75 25 46 15 19

September 58 16 36 11 21

Annual 91 37 57 13 17
Statistical Summaries of Streamflow 57

06050000 Hyalite Creek at Hyalite Ranger Station, near Bozeman, Mont.—Continued

Site Number 40

Regulated streamflow period

Magnitude and probability of annual low flow

based on 41 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 9.9 7.4 6.4 5.6 4.9 --

3 10 7.8 6.7 5.9 5.1 --

7 11 8.5 7.3 6.4 5.6 --

14 12 9.3 8.0 7.1 6.2 --

30 13 10 8.9 7.8 6.7 --

60 15 12 10 9.0 7.7 --

90 17 14 12 10 9.0 --

120 19 15 13 12 10 --

183 28 22 19 18 16 --

Magnitude and probability of seasonal low flow from

March-June based on 42 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 14 11 8.9 7.7 6.6 --

3 15 11 9.3 8.1 6.9 --

7 15 12 10 8.9 7.7 --

14 16 12 11 9.6 8.4 --

30 17 13 11 10 8.7 --

Magnitude and probability of seasonal low flow from

November-February based on 41 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 11 7.8 6.6 5.7 5.0 --

3 11 8.2 6.9 6.0 5.2 --

7 12 8.9 7.5 6.5 5.6 --

14 13 9.7 8.2 7.1 6.2 --

30 15 11 9.3 8.1 6.8 --

Duration of daily mean flows based on 42 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

7.7 9.1 12 14 18 22 28 37

40% 30% 20% 15% 10% 5% 2% 1%

52 79 113 134 174 241 324 365

Magnitude and probability of annual high flow

based on 42 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 361 471 540 626 687 --

3 337 438 502 580 636 --

7 301 388 442 506 552 --

15 269 341 383 433 468 --

30 236 296 331 370 397 --

60 197 246 276 310 334 --

90 169 207 229 254 271 --

Magnitude and probability of seasonal low flow from

July-October based on 43 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 27 20 17 15 13 --

3 28 21 18 16 14 --

7 29 22 19 17 15 --

14 32 24 21 18 16 --

30 36 27 24 21 19 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 80 20 39 14 44

November 62 12 26 9.7 42

December 30 7.7 20 5.4 42

January 32 6.3 17 5.2 42

February 35 8.6 17 4.9 42

March 37 8.5 18 6.1 42

April 66 13 36 13 44

May 273 56 133 50 44

June 383 108 219 59 44

July 275 63 142 45 44

August 145 41 89 22 44

September 117 28 53 19 44

Annual 102 43 68 14 42
58 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06052500 Gallatin River at Logan, Mont.

Site Number 41

LOCATION.--Lat 45°53'07", long 111°26'15" (NAD 27), in SE1⁄4NW1⁄4NE1⁄4 sec.35, T.2 N., R.2 E., Gallatin County, Hydrologic Unit 10020008, on right bank at 

former county road bridge site, 0.2 mi upstream from present county bridge, 0.5 mi west of Logan, and at river mile 6.3.

DRAINAGE AREA.--1,795 mi2.

PERIOD OF RECORD.--September 1893 to December 1905, August 1928 to current year (2002). Monthly discharge only for some periods, published in WSP 

1309.

REVISED RECORDS.--WSP 1389: 1898-99, 1903, 1905, 1929(M), 1935-36(M), 1938-39(M), 1941(M). WSP 1559: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 4,086.42 ft (NGVD 29). Prior to Aug. 10, 1928, nonrecording gages at several sites within 0.5 mi of present 

site at various datums. Aug. 10, 1928, to Oct. 7, 1941, nonrecording gage at present site and datum.

REMARKS.--Some regulation by Middle Creek Reservoir (station number 06049500). Diversions for irrigation of about 110,000 acres upstream from station. 

U.S. Army Corps of Engineers satellite telemeter at station.

Magnitude and probability of annual low flow

based on 78 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 326 241 203 176 149 133

3 332 246 209 183 157 141

7 346 256 218 191 163 147

14 366 268 226 196 167 149

30 401 289 241 207 173 153

60 473 336 276 233 190 166

90 541 392 324 274 225 195

120 606 449 375 319 262 228

183 674 522 445 385 322 284

Magnitude and probability of seasonal low flow from

March-June based on 80 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 610 440 349 279 209 169

3 634 462 368 295 221 178

7 669 496 398 320 240 194

14 726 567 469 388 301 248

30 824 653 542 448 347 286

Magnitude and probability of seasonal low flow from

November-February based on 79 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 516 404 347 303 256 227

3 536 422 364 319 271 241

7 568 455 396 350 300 269

14 607 491 431 383 331 298

30 648 536 477 428 376 342

Duration of daily mean flows based on 80 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

205 248 322 416 550 622 693 767

40% 30% 20% 15% 10% 5% 2% 1%

888 1,010 1,230 1,490 2,120 3,270 4,630 5,560

Magnitude and probability of annual high flow

based on 80 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 4,880 6,430 7,160 7,820 8,180 8,460

3 4,570 6,070 6,800 7,490 7,880 8,190

7 4,140 5,590 6,340 7,100 7,560 7,950

15 3,690 5,100 5,890 6,740 7,280 7,750

30 3,180 4,470 5,210 6,020 6,540 7,010

60 2,520 3,530 4,120 4,800 5,250 5,670

90 2,060 2,830 3,300 3,850 4,220 4,570

Magnitude and probability of seasonal low flow from

July-October based on 79 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 328 244 206 178 150 135

3 334 248 212 186 158 142

7 349 260 222 194 164 148

14 369 272 230 198 169 151

30 406 293 246 209 175 155

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 1,260 333 777 227 81

November 1,190 328 829 175 81

December 1,050 464 751 127 81

January 971 410 690 118 80

February 1,250 385 707 143 80

March 1,290 478 799 148 80

April 1,990 429 1,050 302 80

May 4,690 176 2,110 896 80

June 5,960 280 2,900 1,360 80

July 3,900 162 1,010 710 80

August 1,660 167 487 230 81

September 1,270 238 647 232 81

Annual 1,670 454 1,060 297 80
Statistical Summaries of Streamflow 59

06054500 Missouri River at Toston, Mont.

Site Number 42

LOCATION.--Lat 46°08'46", long 111°25'11" (NAD 27), in NW1⁄4SE1⁄4NW1⁄4 sec.36, T.5 N., R.2 E., Broadwater County, Hydrologic Unit 10030101, on left bank 

2.2 mi southeast of Toston, 4.8 mi upstream from Crow Creek, 7.8 mi downstream from Sixteenmile Creek, and at river mile 2,296.1.

DRAINAGE AREA.--14,669 mi2. 

PERIOD OF RECORD.--April 1890 to February 1891, April 1910 to December 1916, April 1941 to current year (2002). Monthly discharge only for some periods, 

published in WSP 1309.

GAGE.--Water-stage recorder. Altitude of gage is 3,905.68 ft (NGVD 29). Prior to Dec. 20, 1916, nonrecording gages at site 2.5 mi downstream at different 

datums.

REMARKS.--Some regulation by six reservoirs on tributaries and Clark Canyon Reservoir (station number 06015300). Diversions for irrigation of about 

555,400 acres of which 12,000 acres lies downstream from station. U.S. Army Corps of Engineers satellite telemeter at station.

Magnitude and probability of annual low flow

based on 65 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1,610 1,180 994 855 716 633

3 1,710 1,260 1,060 914 764 675

7 1,900 1,410 1,180 1,010 839 737

14 2,080 1,510 1,260 1,060 872 758

30 2,320 1,670 1,380 1,160 941 814

60 2,670 1,940 1,610 1,350 1,100 949

90 3,010 2,270 1,910 1,640 1,360 1,200

120 3,390 2,650 2,290 2,000 1,710 1,530

183 3,610 2,990 2,690 2,470 2,220 2,070

Magnitude and probability of seasonal low flow from

March-June based on 67 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 2,920 2,180 1,830 1,570 1,300 1,140

3 3,080 2,330 1,960 1,680 1,390 1,210

7 3,340 2,610 2,230 1,930 1,610 1,420

14 3,600 2,920 2,560 2,280 1,980 1,790

30 4,020 3,340 3,000 2,720 2,430 2,250

Magnitude and probability of seasonal low flow from

November-February based on 66 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1,960 1,450 1,200 1,010 815 699

3 2,100 1,600 1,350 1,160 955 832

7 2,390 1,940 1,710 1,530 1,340 1,230

14 2,730 2,310 2,110 1,950 1,770 1,660

30 3,110 2,700 2,510 2,350 2,190 2,080

Duration of daily mean flows based on 67 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

1,210 1,460 1,850 2,340 2,990 3,400 3,760 4,120

40% 30% 20% 15% 10% 5% 2% 1%

4,670 5,400 6,180 7,630 9,560 13,900 19,500 22,700

Magnitude and probability of annual high flow

based on 67 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 17,800 24,300 27,900 31,800 34,300 36,500

3 17,400 23,800 27,400 31,300 33,800 36,100

7 16,400 22,700 26,300 30,200 32,800 35,100

15 15,000 21,100 24,500 28,300 30,800 33,000

30 13,400 18,600 21,600 24,900 27,000 29,000

60 10,900 14,900 17,100 19,500 21,100 22,500

90 9,350 12,500 14,200 16,100 17,300 18,400

Magnitude and probability of seasonal low flow from

July-October based on 67 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1,970 1,380 1,130 964 801 706

3 2,020 1,400 1,150 976 807 710

7 2,090 1,450 1,190 1,020 841 745

14 2,180 1,520 1,270 1,070 881 766

30 2,390 1,680 1,390 1,180 944 825

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 6,780 2,510 4,450 993 68

November 7,030 3,130 4,740 887 68

December 5,970 2,680 3,780 641 68

January 4,890 2,430 3,400 587 67

February 5,220 2,270 3,730 600 67

March 6,900 2,840 4,120 773 67

April 10,100 2,390 5,630 1,680 67

May 18,400 3,130 8,750 3,490 68

June 24,500 3,180 12,500 5,460 68

July 14,200 1,240 5,210 2,760 68

August 5,730 896 2,750 1,170 68

September 5,810 1,450 3,430 1,030 68

Annual 7,740 2,930 5,220 1,220 67
60 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06055500 Crow Creek near Radersburg, Mont.

Site Number 43

LOCATION.--Lat 46°16'10", long 111°41'38" (NAD 27), Broadwater County, Hydrologic Unit 10030101, on left bank, 0.8 mi west of Helena National Forest 

boundary, 1.5 mi upstream from Slim Sam Creek, and 6.0 mi northwest of Radersburg. 

DRAINAGE AREA.--76.6 mi2. 

PERIOD OF RECORD.--Apri1 to June 1901, May 1919 to September 1929, June 1966 to June 1972, April 1989 to October 1990 (discontinued, seasonal records 

only). Monthly discharge only for some periods, published in WSP 1309. 

REVISED RECORDS.--WSP 1509: 1920, 1921, 1922(M), 1924(M). WRD MT-66: Drainage area. 

GAGE.--Water-stage recorder. Altitude of gage is 4,870 ft (NGVD 29, from topographic map). Prior to June 29, 1901, nonrecording gage at site 1.5 mi 

downstream at different datum. May 25, 1919, to Apr. 16, 1924, nonrecording gage at about the same site as earlier record but different datum. Apr. 17, 1924, 

to Sept. 30, 1929, at site 0.6 mi downstream at different datum.

REMARKS.--No known diversions upstream from gage.

Magnitude and probability of annual low flow

based on 14 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 4.7 3.2 2.6 2.2 -- --

3 5.1 3.5 2.9 2.4 -- --

7 5.4 3.7 3.0 2.4 -- --

14 6.1 4.1 3.3 2.6 -- --

30 6.6 4.7 3.9 3.2 -- --

60 7.5 5.6 4.9 4.3 -- --

90 8.6 6.7 5.8 5.1 -- --

120 10 7.8 6.7 5.8 -- --

183 13 11 9.6 8.6 -- --

Magnitude and probability of seasonal low flow from

March-June based on 16 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 7.8 5.2 4.1 3.3 -- --

3 7.9 5.8 4.9 4.4 -- --

7 8.4 6.1 5.2 4.6 -- --

14 8.9 6.8 6.0 5.4 -- --

30 11 8.1 6.9 6.1 -- --

Magnitude and probability of seasonal low flow from

November-February based on 16 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 5.3 3.6 3.0 2.5 -- --

3 5.5 3.8 3.0 2.6 -- --

7 5.9 4.0 3.2 2.6 -- --

14 6.4 4.3 3.4 2.8 -- --

30 6.9 4.9 4.0 3.4 -- --

Duration of daily mean flows based on 15 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

3.5 4.5 5.9 6.7 8.7 12 15 18

40% 30% 20% 15% 10% 5% 2% 1%

22 31 63 92 138 223 332 406

Magnitude and probability of annual high flow

based on 15 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 427 520 578 647 -- --

3 386 475 531 600 -- --

7 345 430 488 562 -- --

15 292 373 430 505 -- --

30 244 313 362 428 -- --

60 179 224 258 305 -- --

90 138 171 196 230 -- --

Magnitude and probability of seasonal low flow from

July-October based on 16 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 11 7.1 5.6 4.6 -- --

3 11 7.8 6.4 5.4 -- --

7 12 9.0 7.4 6.3 -- --

14 14 9.9 8.2 7.0 -- --

30 16 12 9.4 7.8 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 24 7.0 17 5.2 16

November 25 7.0 14 4.8 16

December 17 5.0 9.8 2.8 16

January 17 4.0 8.4 3.0 16

February 14 3.0 8.5 3.0 16

March 20 6.0 12 3.9 16

April 96 9.6 34 21 19

May 263 108 167 46 19

June 377 46 168 94 21

July 142 9.0 54 29 19

August 38 6.9 23 7.7 19

September 27 2.5 17 6.1 20

Annual 68 34 48 9.0 15
Statistical Summaries of Streamflow 61

06061500 Prickly Pear Creek near Clancy, Mont.

Site Number 44

LOCATION.--Lat 46°31'09", long 111°56'45" (NAD 27), in NE1⁄4SE1⁄4SW1⁄4 sec.23, T.9 N., R.3 W., Jefferson County, Hydrologic Unit 10030101, on right bank 

3.5 mi downstream from Lump Gulch, 4 mi northeast of Clancy, 7 mi southeast of Helena, and at river mile 24.4.

DRAINAGE AREA.--192 mi2.

PERIOD OF RECORD.--July 1908 to September 1916, July 1921 to September 1933, October 1945 to October 1953, October 1954 to September 1969, October 

1978 to 2002 (discontinued). October 1969 to September 1980 record collected by Montana Department of Natural Resources and Conservation. Monthly 

discharge only for some periods, published in WSP 1309.

REVISED RECORDS.--WSP 1086: 1946(M). WSP 1309: 1925, 1927, 1931(M), 1933, 1948(M). WSP 1729: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 4,067.1 ft (NGVD 29). Prior to July 12, 1910, nonrecording gage at site 1.2 mi upstream at different datum. 

July 12, 1910, to Sept. 30, 1916, and July 28, 1921, to Aug. 12, 1933, nonrecording gage at site 2.2 mi upstream at different datum.

REMARKS.--Diversions for irrigation of about 700 acres upstream from station.

Magnitude and probability of annual low flow

based on 63 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 12 8.6 7.0 5.8 4.8 4.2

3 13 9.0 7.3 6.2 5.0 4.4

7 14 9.8 8.0 6.6 5.3 4.5

14 15 11 8.7 7.1 5.6 4.8

30 17 12 9.7 7.9 6.1 5.1

60 19 14 11 9.0 7.0 5.9

90 21 15 13 11 8.8 7.6

120 22 16 14 12 9.9 8.8

183 24 17 15 13 11 9.6

Magnitude and probability of seasonal low flow from

March-June based on 67 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 20 14 11 9.7 8.2 7.4

3 20 14 12 10 8.7 7.8

7 22 16 13 12 10 9.3

14 24 17 15 13 12 11

30 28 21 18 16 14 13

Magnitude and probability of seasonal low flow from

November-February based on 67 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 15 10 8.3 7.0 5.8 5.1

3 15 11 8.8 7.5 6.2 5.5

7 16 12 9.6 8.2 6.9 6.1

14 17 13 11 9.1 7.6 6.7

30 19 14 12 11 9.1 8.2

Duration of daily mean flows based on 67 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

8.1 10 13 16 19 22 27 31

40% 30% 20% 15% 10% 5% 2% 1%

37 45 63 79 102 149 208 257

Magnitude and probability of annual high flow

based on 67 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 215 361 482 664 823 1,000

3 195 320 419 563 684 819

7 174 280 361 476 571 673

15 157 248 315 406 477 552

30 138 213 265 333 384 436

60 114 170 206 250 282 312

90 96 140 168 201 225 247

Magnitude and probability of seasonal low flow from

July-October based on 66 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 19 11 8.6 6.7 5.0 4.1

3 19 12 8.8 6.9 5.2 4.2

7 19 12 9.1 7.2 5.4 4.4

14 20 13 9.6 7.6 5.7 4.7

30 22 14 10 8.2 6.2 5.2

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 70 11 31 14 68

November 60 12 29 11 67

December 44 10 24 7.8 67

January 37 9.9 21 6.3 67

February 57 8.6 24 8.9 67

March 80 12 31 12 67

April 131 23 52 20 67

May 453 21 108 56 67

June 450 20 129 82 67

July 141 9.9 57 34 69

August 89 4.7 30 17 69

September 71 7.3 29 15 69

Annual 117 15 47 18 67
62 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06062500 Tenmile Creek near Rimini, Mont.

Site Number 45

LOCATION.--Lat 46°31'27", long 112°15'22" (NAD 27), in NE1⁄4SW1⁄4NE1⁄4 sec.20, T.9 N., R.5 W., Lewis and Clark County, Hydrologic Unit 10030101, Helena 

National Forest, on left bank at U.S. Forest Service Moose Creek campground, 500 ft upstream from Moose Creek, 2.5 mi north of Rimini, and at river mile 

20.4.

DRAINAGE AREA.--30.9 mi2.

PERIOD OF RECORD.--July 1914 to September 1994, May 1997 to current year (2002). Monthly discharge only for some periods, published in WSP 1309.

REVISED RECORDS.--WSP 1309: 1917, 1921, 1924-25. WSP 1509: 1915, 1916-17(M), 1920(M), 1927(M), 1928-30, 1947(M), 1948, 1950(M). WSP 1559: 

Drainage area. WSP 1709: 1959. WDR-MT-97-1: Drainage area.

GAGE.--Water-stage recorder and concrete control. Altitude of gage is 4,850 ft (NGVD 29). Prior to Dec. 17, 1934, water-stage recorder at site 40 ft downstream 

at different datum and different control.

REMARKS.--Flow partly regulated by Chessman and Scott Reservoirs on tributaries upstream from station, combined capacity, 2,340 acre-feet. Some small 

diversions upstream from station. U.S. Geological Survey satellite telemeter at station.

Magnitude and probability of annual low flow

based on 84 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.33 0.13 0.04 0.00 0.00 0.00

3 .36 .14 .07 .00 .00 .00

7 .43 .15 .07 .04 .00 .00

14 .47 .20 .13 .09 .06 .04

30 .58 .27 .18 .13 .09 .07

60 .76 .37 .26 .19 .14 .11

90 .91 .44 .30 .22 .15 .12

120 1.0 .50 .34 .25 .18 .14

183 1.3 .60 .42 .32 .23 .19

Magnitude and probability of seasonal low flow from

March-June based on 86 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.96 0.41 0.26 0.18 0.12 0.09

3 1.0 .43 .28 .19 .12 .09

7 1.1 .49 .31 .21 .14 .10

14 1.3 .58 .37 .26 .17 .12

30 1.8 .81 .51 .35 .22 .16

Magnitude and probability of seasonal low flow from

November-February based on 85 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.49 0.22 0.14 0.10 0.07 0.05

3 .53 .23 .15 .11 .07 .06

7 .62 .28 .19 .13 .09 .07

14 .72 .34 .22 .16 .10 .08

30 .86 .40 .26 .18 .12 .09

Duration of daily mean flows based on 85 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

0.03 0.07 0.17 0.33 0.66 0.99 1.4 2.1

40% 30% 20% 15% 10% 5% 2% 1%

3.5 6.2 17 30 54 101 168 215

Magnitude and probability of annual high flow

based on 85 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 172 299 397 532 641 756

3 165 271 342 428 489 548

7 148 237 291 352 391 427

15 125 200 244 294 327 356

30 103 164 201 243 270 295

60 75 118 144 171 189 204

90 56 88 106 127 140 151

Magnitude and probability of seasonal low flow from

July-October based on 85 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.42 0.17 0.07 0.00 0.00 0.00

3 .45 .17 .09 .00 .00 .00

7 .52 .18 .09 .04 .00 .00

14 .56 .23 .15 .10 .06 .05

30 .70 .31 .21 .16 .11 .09

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 23 0.19 3.1 4.2 86

November 14 .22 2.3 2.5 86

December 9.6 .17 1.8 1.7 86

January 7.0 .14 1.5 1.2 86

February 5.1 .06 1.3 1.0 86

March 18 .07 2.5 2.7 86

April 67 1.5 18 14 86

May 300 6.1 83 46 87

June 346 3.0 73 63 87

July 66 .34 12 14 86

August 22 .13 2.5 3.1 86

September 22 .23 2.4 3.5 86

Annual 53 1.7 17 9.2 85
Statistical Summaries of Streamflow 63

06063000 Tenmile Creek near Helena, Mont.

Site Number 46

LOCATION.--Lat 46°36'20", long 112°05'20" (NAD 27), near center of SE1⁄4 sec.22, T.10 N., R.4 W., Lewis and Clark County, on right bank near Broadwater 

Hotel 1.5 mi west of Helena and 2.5 mi upstream from Sevenmile Creek.

DRAINAGE AREA.--96.5 mi2. 

PERIOD OF RECORD.--46 years. July 1908 to September 1954 (discontinued).

GAGE.--Water-stage recorder and concrete control. Altitude of gage is 3,960 ft (NGVD 29, from topographic map). Prior to Sept. 18, 1925, staff gage and 

Sept. 18, 1925, to Mar. 15, 1929, water-stage recorder, at site 100 ft downstream at different datum.

REMARKS.--Diversions for irrigation of about 1,200 acres upstream from station.

Magnitude and probability of annual low flow

based on 40 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.35 0.10 0.00 0.00 0.00 --

3 .39 .11 .00 .00 .00 --

7 .44 .14 .00 .00 .00 --

14 .52 .15 .00 .00 .00 --

30 .70 .28 .00 .00 .00 --

60 1.3 .35 .12 .00 .00 --

90 2.2 .65 .27 .10 .00 --

120 3.0 1.3 .76 .49 .29 --

183 4.0 2.0 1.4 1.0 .72 --

Magnitude and probability of seasonal low flow from

March-June based on 46 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 3.5 1.6 0.88 0.31 0.00 --

3 3.8 1.7 1.0 .58 .00 --

7 4.7 2.1 1.2 .68 .34 --

14 5.1 2.5 1.6 1.0 .63 --

30 7.3 3.9 2.7 2.0 1.4 --

Magnitude and probability of seasonal low flow from

November-February based on 46 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 2.7 1.3 0.78 0.50 0.28 --

3 2.8 1.3 .84 .54 .31 --

7 2.9 1.5 .94 .62 .38 --

14 3.2 1.6 1.1 .71 .44 --

30 3.5 1.9 1.3 .96 .66 --

Duration of daily mean flows based on 46 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

0.08 0.17 0.42 0.84 1.9 3.2 4.7 6.5

40% 30% 20% 15% 10% 5% 2% 1%

9.5 15 29 43 72 140 246 329

Magnitude and probability of annual high flow

based on 46 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 230 420 560 747 891 --

3 212 391 524 701 837 --

7 187 346 464 620 740 --

15 159 291 390 523 625 --

30 130 242 327 446 541 --

60 98 175 233 310 370 --

90 75 134 176 231 272 --

Magnitude and probability of seasonal low flow from

July-October based on 40 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.36 0.10 0.00 0.00 0.00 --

3 .40 .12 .00 .00 .00 --

7 .45 .15 .00 .00 .00 --

14 .53 .16 .00 .00 .00 --

30 .71 .30 .00 .00 .00 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 40 0.62 8.5 8.3 46

November 26 .99 8.3 6.1 46

December 19 .75 6.3 4.6 46

January 19 .86 5.5 3.9 46

February 14 1.6 5.3 3.0 46

March 31 1.8 9.8 6.8 46

April 111 5.2 36 24 46

May 381 23 115 78 46

June 423 4.4 106 99 46

July 117 .32 19 23 45

August 20 .16 3.6 4.9 42

September 20 .27 3.5 4.2 44

Annual 74 4.6 28 17 46
64 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06065500 Missouri River below Hauser Dam, near Helena, Mont.

Site Number 47

LOCATION.--Lat 46°46'02", long 111°53'27" (NAD 27), in SE1⁄4NW1⁄4SW1⁄4 sec.29, T.12 N., R.2 W., Lewis and Clark County, Hydrologic Unit 10030101, 0.2 mi 

downstream from Hauser Dam, 1.3 mi upstream from Beaver Creek, 15 mi northeast of Helena, and at river mile 2,237.2.

DRAINAGE AREA.--16,876 mi2.

PERIOD OF RECORD.--January 1923 to September 1942, October 1994 to current year (2002). Monthly mean discharges for October, November, and December 

1922 were from Congressional documents: 73rd Congress, 2nd session, H. Doc. 238, Missouri River. Published figures are in acre feet.

GAGE.--Water-stage recorder. Altitude of gage is 3,580 ft (NGVD 29).

REMARKS.--Flow regulated by eight small irrigation reservoirs and two powerplants, Clark Canyon Reservoir (station number 06015300) and Canyon Ferry Lake 

(station number 06058500). Diversions for irrigation of about 594,400 acres. U.S. Geological Survey satellite telemeter at station.

Magnitude and probability of annual low flow

based on 19 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 681 458 362 293 -- --

3 1,240 840 676 561 -- --

7 1,620 1,170 990 863 -- --

14 1,850 1,340 1,120 962 -- --

30 2,080 1,510 1,250 1,060 -- --

60 2,320 1,730 1,460 1,260 -- --

90 2,490 1,890 1,630 1,430 -- --

120 2,650 2,040 1,780 1,590 -- --

183 2,850 2,250 1,990 1,790 -- --

Magnitude and probability of seasonal low flow from

March-June based on 20 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1,820 974 659 460 -- --

3 2,260 1,380 1,020 768 -- --

7 2,610 1,820 1,470 1,220 -- --

14 2,970 2,170 1,820 1,550 -- --

30 3,500 2,730 2,390 2,140 -- --

Magnitude and probability of seasonal low flow from

November-February based on 19 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 998 629 493 403 -- --

3 1,620 1,170 987 854 -- --

7 2,050 1,530 1,300 1,130 -- --

14 2,290 1,790 1,570 1,410 -- --

30 2,610 2,090 1,850 1,660 -- --

Duration of daily mean flows based on 20 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

826 1,020 1,430 1,740 2,260 2,640 3,010 3,410

40% 30% 20% 15% 10% 5% 2% 1%

3,820 4,230 5,240 5,800 7,070 9,800 14,200 16,800

Magnitude and probability of annual high flow

based on 20 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 12,500 18,900 23,300 29,000 -- --

3 12,100 18,400 22,900 28,800 -- --

7 11,200 17,200 21,600 27,400 -- --

15 9,860 15,200 19,100 24,300 -- --

30 8,600 13,100 16,500 21,200 -- --

60 7,230 10,700 13,100 16,400 -- --

90 6,280 9,060 11,100 13,800 -- --

Magnitude and probability of seasonal low flow from

July-October based on 19 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 922 551 414 324 -- --

3 1,490 975 766 621 -- --

7 1,840 1,280 1,040 877 -- --

14 2,070 1,440 1,160 964 -- --

30 2,260 1,580 1,280 1,060 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 5,540 1,940 3,300 913 20

November 5,940 2,000 3,430 992 20

December 4,720 1,940 3,250 796 20

January 4,340 1,900 3,080 717 20

February 5,150 1,670 3,220 936 20

March 7,280 2,400 3,940 1,080 20

April 9,230 2,580 5,150 1,920 20

May 16,300 2,380 7,150 3,480 20

June 23,500 2,550 7,960 5,140 20

July 7,640 1,210 3,560 1,760 20

August 3,710 971 2,520 802 20

September 4,620 1,500 2,840 929 20

Annual 6,410 2,380 4,120 1,230 20
Statistical Summaries of Streamflow 65

06066500 Missouri River below Holter Dam, near Wolf Creek, Mont.

Site Number 48

LOCATION.--Lat 46°59'41", long 112°00'37" (NAD 27), in NE1⁄4SW1⁄4SE1⁄4 sec.5, T.14 N., R.3 W., Lewis and Clark County, Hydrologic Unit 10030102, on left 

bank 0.4 mi downstream from Holter Dam, 2.8 mi southeast of Wolf Creek, and at river mile 2,210.7.

DRAINAGE AREA.--17,149 mi2.

PERIOD OF RECORD.--October 1945 to current year (2002).

GAGE.--Water-stage recorder. Altitude of gage is 3,464.11 ft (NGVD 29).

REMARKS.--Flow regulated by nine smaller irrigation reservoirs and powerplants, Clark Canyon Reservoir (station number 06015300), and Canyon Ferry Lake 

(station number 06058500). Diversions for irrigation of about 594,400 acres. Bureau of Reclamation satellite telemeter at station.

Magnitude and probability of annual low flow

based on 49 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 2,720 1,720 1,290 992 718 --

3 2,950 1,920 1,450 1,120 811 --

7 3,120 2,140 1,680 1,340 1,020 --

14 3,270 2,290 1,830 1,490 1,150 --

30 3,500 2,560 2,110 1,770 1,430 --

60 3,690 2,810 2,400 2,090 1,770 --

90 3,890 3,040 2,650 2,360 2,060 --

120 4,110 3,210 2,800 2,490 2,170 --

183 4,370 3,460 3,050 2,730 2,410 --

Magnitude and probability of seasonal low flow from

March-June based on 50 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 3,140 1,850 1,350 1,020 725 570

3 3,390 2,030 1,490 1,130 822 625

7 3,540 2,230 1,700 1,350 1,030 821

14 3,710 2,380 1,840 1,510 1,170 930

30 4,080 2,750 2,190 1,790 1,450 1,190

Magnitude and probability of seasonal low flow from

November-February based on 49 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 3,670 2,960 2,650 2,410 2,180 --

3 3,890 3,250 2,960 2,750 2,520 --

7 4,070 3,420 3,120 2,890 2,650 --

14 4,170 3,490 3,180 2,930 2,680 --

30 4,350 3,630 3,300 3,040 2,760 --

Duration of daily mean flows based on 50 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

1,760 2,220 2,480 2,910 3,470 3,950 4,430 4,920

40% 30% 20% 15% 10% 5% 2% 1%

5,410 5,890 6,940 7,670 8,390 11,000 15,200 17,000

Magnitude and probability of annual high flow

based on 50 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 12,200 18,600 22,600 27,300 30,500 33,500

3 11,900 18,200 22,200 26,900 30,200 33,300

7 11,300 17,500 21,400 26,100 29,400 32,500

15 10,500 16,300 20,100 24,800 28,200 31,500

30 9,420 14,100 17,300 21,100 24,000 26,800

60 8,140 11,500 13,700 16,300 18,200 20,000

90 7,400 10,100 11,800 13,700 15,100 16,500

Magnitude and probability of seasonal low flow from

July-October based on 49 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 3,040 2,130 1,720 1,420 1,120 --

3 3,280 2,420 2,010 1,700 1,390 --

7 3,450 2,660 2,290 2,010 1,730 --

14 3,610 2,800 2,420 2,120 1,820 --

30 3,750 2,950 2,590 2,320 2,040 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 10,100 2,710 4,520 1,340 50

November 8,500 2,970 4,850 1,320 50

December 9,640 3,020 5,100 1,120 50

January 6,640 3,070 5,200 901 50

February 7,950 3,040 5,150 1,040 50

March 9,190 2,760 5,170 1,490 50

April 11,100 2,490 5,350 1,910 50

May 14,300 2,060 6,190 3,030 50

June 20,700 1,530 8,530 5,000 50

July 16,600 2,450 6,060 3,140 50

August 7,590 1,970 4,420 1,300 50

September 10,000 2,080 4,300 1,390 50

Annual 8,500 3,010 5,400 1,430 50
66 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06068500 Little Prickly Pear Creek near Marysville, Mont.

Site Number 49

LOCATION.--Lat 46°47'16", long 112°24'24" (NAD 27), in SW1⁄4 sec.18 T.12 N., R.6 W., Lewis and Clark County, 0.5 mi (revised) downstream from Deadman 

Creek and 6 mi northeast of Marysville.

DRAINAGE AREA.--44.4 mi 2.

PERIOD OF RECORD.--19 years (1913-32).

GAGE.--Staff gage. Altitude of gage is 4,700 ft (NGVD 29, from topographic map). Apr. 12 to May 23, 1913, at site just downstream from mouth of Deadman 

Creek at different datum.

REMARKS.--Some diversions for irrigation upstream from station.

Magnitude and probability of annual low flow

based on 18 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 4.4 3.1 2.5 2.1 -- --

3 4.4 3.1 2.6 2.2 -- --

7 4.4 3.1 2.6 2.2 -- --

14 4.7 3.5 2.9 2.6 -- --

30 5.4 4.2 3.7 3.4 -- --

60 6.6 5.4 4.8 4.3 -- --

90 7.7 6.3 5.6 5.1 -- --

120 8.7 7.0 6.2 5.6 -- --

183 11 8.3 7.2 6.4 -- --

Magnitude and probability of seasonal low flow from

March-June based on 19 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 5.7 3.7 2.9 2.4 -- --

3 5.7 3.7 3.0 2.4 -- --

7 5.9 3.9 3.0 2.5 -- --

14 6.5 4.2 3.4 2.8 -- --

30 7.8 5.1 4.2 3.6 -- --

Magnitude and probability of seasonal low flow from

November-February based on 19 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 5.3 3.9 3.3 2.8 -- --

3 5.4 4.0 3.3 2.8 -- --

7 5.4 4.0 3.3 2.8 -- --

14 5.5 4.2 3.5 3.1 -- --

30 5.8 4.6 4.0 3.6 -- --

Duration of daily mean flows based on 19 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

3.4 4.1 4.8 5.8 7.1 8.9 12 14

40% 30% 20% 15% 10% 5% 2% 1%

18 22 32 44 63 107 168 215

Magnitude and probability of annual high flow

based on 19 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 156 243 288 332 -- --

3 151 232 273 313 -- --

7 138 212 251 289 -- --

15 117 182 219 258 -- --

30 96 154 190 234 -- --

60 74 118 147 184 -- --

90 61 95 115 140 -- --

Magnitude and probability of seasonal low flow from

July-October based on 20 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 11 7.6 6.1 5.0 -- --

3 11 8.0 6.6 5.6 -- --

7 12 8.3 6.9 5.9 -- --

14 12 8.6 7.1 6.0 -- --

30 12 9.2 7.7 6.6 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 18 7.2 13 3.9 20

November 16 4.6 11 3.4 20

December 14 5.3 9.4 2.4 20

January 11 5.0 7.9 1.9 19

February 10 3.5 6.1 1.8 19

March 24 3.3 9.4 5.5 19

April 64 5.0 30 18 20

May 190 23 87 44 20

June 245 17 78 60 20

July 67 8.7 32 16 20

August 28 7.2 19 6.4 20

September 20 7.3 14 4.0 20

Annual 51 8.8 26 10 19
Statistical Summaries of Streamflow 67

06071000 Little Prickly Pear Creek near Canyon Creek, Mont.

Site Number 50

LOCATION.--Lat 46°49'08", long 112°15'01" (NAD 27), in NW1⁄4 sec.9, T.12 N., R.5 W., Lewis and Clark County, 0.5 mi downstream from Canyon Creek and 

1 mi (revised) northeast of Canyon Creek Post Office.

DRAINAGE AREA.--183 mi2.

PERIOD OF RECORD.--13 years (1909-11, 1913-24).

GAGE.--Staff gage. Altitude of gage is 4,240 ft (NGVD 29, from topographic map). Prior to June 2, 1917, at site 0.25 mi downstream at different datum.

REMARKS.--Flow is greatly affected by diversions for irrigation upstream from station.

Magnitude and probability of annual low flow

based on 10 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.66 0.13 0.00 0.00 -- --

3 .78 .16 .00 .00 -- --

7 1.3 .29 .00 .00 -- --

14 1.8 .49 .24 .14 -- --

30 3.1 .97 .53 .32 -- --

60 7.0 2.1 1.0 .51 -- --

90 11 5.0 3.0 1.9 -- --

120 13 6.4 4.1 2.7 -- --

183 17 9.8 6.8 4.8 -- --

Magnitude and probability of seasonal low flow from

March-June based on 12 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 10 0.71 0.02 0.00 -- --

3 11 .84 .03 .00 -- --

7 13 1.2 .05 .00 -- --

14 15 2.5 .80 .27 -- --

30 31 8.2 2.9 1.1 -- --

Magnitude and probability of seasonal low flow from

November-February based on 13 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 16 9.2 6.1 4.1 -- --

3 16 9.8 7.0 5.0 -- --

7 17 11 8.0 6.1 -- --

14 17 12 9.9 8.2 -- --

30 19 14 12 11 -- --

Duration of daily mean flows based on 12 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

0.27 0.54 1.8 4.7 13 18 22 27

40% 30% 20% 15% 10% 5% 2% 1%

31 41 64 88 139 232 337 418

Magnitude and probability of annual high flow

based on 12 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 282 398 444 -- -- --

3 271 384 425 -- -- --

7 252 358 395 -- -- --

15 219 320 358 -- -- --

30 181 272 309 -- -- --

60 139 209 240 -- -- --

90 111 168 194 -- -- --

Magnitude and probability of seasonal low flow from

July-October based on 15 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1.7 0.21 0.00 0.00 -- --

3 1.9 .23 .00 .00 -- --

7 2.3 .47 .14 .00 -- --

14 2.9 .86 .46 .27 -- --

30 4.0 1.3 .75 .47 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 44 4.9 23 9.4 15

November 40 10 25 8.8 15

December 49 12 24 8.6 15

January 44 13 23 8.1 13

February 47 13 25 10 13

March 80 20 41 20 13

April 181 23 83 41 15

May 458 9.4 189 116 15

June 291 .40 111 96 14

July 134 .66 32 40 15

August 36 .84 13 11 15

September 38 2.2 20 11 15

Annual 79 12 44 18 12
68 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06071300 Little Prickly Pear Creek at Wolf Creek, Mont.

Site Number 51

LOCATION.--Lat 47°00'19", long 112°04'10" (NAD 27), in NE1⁄4NW1⁄4NE1⁄4 sec.2, T.14 N., R.4 W., Lewis and Clark County, Hydrologic Unit 10030102, on right 

bank 30 ft downstream from Interstate 15 access road bridge, 500 ft southwest of Wolf Creek Post Office, 0.5 mi downstream from Wolf Creek, and at river 

mile 3.2.

DRAINAGE AREA.--381 mi2.

PERIOD OF RECORD.--May 1962 to September 1967, October 1991 to current year (2002).

GAGE.--Water-stage recorder. Altitude of gage is 3,547.38 ft (NGVD 29). May 10, 1962, to July 6, 1965, water-stage recorder on left bank at present datum. 

July 7, 1965, to Apr. 11, 1966, non-recording gage on bridge 0.25 mi upstream at datum 3.27 ft higher. Apr. 12, 1966, to Sept. 30, 1967, water-stage recorder 

on right bank 23 ft upstream at present datum.

REMARKS.--Diversions for irrigation of about 2,500 acres upstream from station. U.S. Geological Survey satellite telemeter at station. 

Magnitude and probability of annual low flow

based on 15 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 19 14 11 9.8 -- --

3 21 15 12 10 -- --

7 24 17 14 11 -- --

14 28 19 15 13 -- --

30 32 22 17 14 -- --

60 36 24 19 16 -- --

90 38 27 22 18 -- --

120 40 29 24 20 -- --

183 42 31 27 24 -- --

Magnitude and probability of seasonal low flow from

March-June based on 16 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 34 23 19 16 -- --

3 35 24 20 17 -- --

7 39 28 24 20 -- --

14 48 35 29 25 -- --

30 58 41 33 27 -- --

Magnitude and probability of seasonal low flow from

November-February based on 16 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 21 16 15 13 -- --

3 23 18 16 15 -- --

7 27 21 19 17 -- --

14 32 26 23 21 -- --

30 39 31 27 24 -- --

Duration of daily mean flows based on 16 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

15 18 24 28 36 43 50 58

40% 30% 20% 15% 10% 5% 2% 1%

65 82 110 131 182 300 519 677

Magnitude and probability of annual high flow

based on 16 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 495 1,040 1,510 2,210 -- --

3 438 862 1,200 1,670 -- --

7 363 671 902 1,210 -- --

15 297 525 691 910 -- --

30 237 428 580 799 -- --

60 193 348 477 671 -- --

90 162 281 378 522 -- --

Magnitude and probability of seasonal low flow from

July-October based on 16 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 30 18 13 10 -- --

3 31 18 14 11 -- --

7 32 19 14 12 -- --

14 33 20 15 13 -- --

30 35 22 17 14 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 131 30 52 28 16

November 98 32 54 17 16

December 75 26 50 13 16

January 69 31 45 11 16

February 190 29 61 40 16

March 102 42 66 18 16

April 372 65 134 87 16

May 580 36 235 178 17

June 684 26 210 184 17

July 175 18 83 47 17

August 95 14 47 24 17

September 127 18 50 32 17

Annual 179 35 90 42 16
Statistical Summaries of Streamflow 69

06073000 Dearborn River near Clemons, Mont.

Site Number 52

LOCATION.--Lat 47°17'30", long 112°27'00" (NAD 27), in SE1⁄4 SE1⁄4 sec.23, T.18 N., R.7 W., Lewis and Clark County, on right bank 300 ft upstream from 

highway bridge, 0.5 mi southeast of former post office at Clemons, 2 mi downstream from Falls Creek, and 14 mi south of Augusta.

DRAINAGE AREA.--123 mi2 . 

PERIOD OF RECORD.--26 years. April 1921 to September 1923, May 1929 to September 1953. May 1908 to December 1911 at site 2.5 mi upstream; records 

not equivalent owing to tributary inflow (published as "above Falls Creek, near Clemons" in WSP 1309). Monthly discharge only for some periods, published 

in WSP 1309.

GAGE.--Water-stage recorder. Altitude of gage is 4,560 ft (NGVD 29, by barometer). Prior to Apr. 8, 1931, wire-weight gage at same site and datum.

REMARKS.--Diversions for irrigation of about 2,500 acres in Flat Creek drainage, all of which lies downstream from station.

Magnitude and probability of annual low flow

based on 24 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 16 11 8.6 7.3 -- --

3 16 11 8.7 7.4 -- --

7 16 11 9.2 7.8 -- --

14 17 12 9.7 8.2 -- --

30 19 13 10 8.7 -- --

60 23 15 12 9.9 -- --

90 27 18 14 12 -- --

120 30 21 17 14 -- --

183 33 23 19 17 -- --

Magnitude and probability of seasonal low flow from

March-June based on 26 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 25 19 17 16 15 --

3 26 20 18 16 15 --

7 27 21 18 17 15 --

14 29 22 20 18 17 --

30 31 24 22 20 19 --

Magnitude and probability of seasonal low flow from

November-February based on 26 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 22 18 16 15 14 --

3 23 18 16 16 14 --

7 25 20 18 16 15 --

14 26 20 18 17 15 --

30 27 21 19 17 16 --

Duration of daily mean flows based on 26 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

10 12 16 19 25 29 34 42

40% 30% 20% 15% 10% 5% 2% 1%

53 75 141 216 339 529 805 1,050

Magnitude and probability of annual high flow

based on 26 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 1,090 1,790 2,120 2,400 2,540 --

3 1,010 1,630 1,920 2,160 2,280 --

7 851 1,350 1,580 1,780 1,870 --

15 684 1,080 1,270 1,440 1,520 --

30 542 853 1,010 1,150 1,220 --

60 422 653 762 856 904 --

90 326 514 610 700 749 --

Magnitude and probability of seasonal low flow from

July-October based on 26 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 16 11 8.7 7.4 6.2 --

3 16 11 8.8 7.4 6.3 --

7 17 11 9.3 7.8 6.7 --

14 18 12 9.8 8.3 7.1 --

30 20 13 10 8.8 7.4 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 111 11 44 24 26

November 125 22 45 24 26

December 97 20 39 19 26

January 65 18 33 12 26

February 51 18 31 11 26

March 104 18 36 18 26

April 440 25 129 105 27

May 675 50 375 160 28

June 1,210 23 451 309 28

July 364 14 123 101 28

August 213 10 47 43 28

September 109 9.4 35 22 28

Annual 214 24 116 55 26
70 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06073500 Dearborn River near Craig, Mont.

Site Number 53

LOCATION.--Lat 47°11'57", long 112°05'44" (NAD 27), in NW1⁄4 NW1⁄4 SE1⁄4 sec.27, T.17 N., R.4 W., Lewis and Clark County, Hydrologic Unit 10030102, on 

left bank at upstream side of bridge on U.S. Highway 287, 7.0 mi downstream from South Fork Dearborn River, 10.5 mi northwest of Craig, 13.5 mi north of 

Wolf Creek, and at river mile 19.0.

DRAINAGE AREA.--325 mi2.

PERIOD OF RECORD.--October 1945 to September 1969, October 1993 to current year (2002).

GAGE.--Water-stage recorder. Altitude of gage is 3,800 ft (NGVD 29). Oct. 1, 1945, to Sept. 30, 1946, nonrecording gage; Oct. 1, 1946, to June 9, 1964, waterstage recorder on upstream side of bridge; June 10, 1964, to May 31, 1965, nonrecording gage; June 1, 1965, to Sept. 30 1969, water-stage recorder on 

downstream side of abandoned bridge, all at same datum.

REMARKS.--U.S. Geological Survey satellite telemeter at station.

Magnitude and probability of annual low flow

based on 31 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 25 18 14 12 9.3 --

3 27 19 16 13 10 --

7 29 21 17 14 11 --

14 32 22 18 15 12 --

30 37 25 20 16 12 --

60 42 29 23 19 15 --

90 49 35 29 23 18 --

120 55 40 33 28 23 --

183 58 42 36 31 27 --

Magnitude and probability of seasonal low flow from

March-June based on 33 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 43 30 25 21 17 --

3 45 32 27 23 20 --

7 48 35 30 26 22 --

14 52 40 35 32 29 --

30 75 52 44 38 32 --

Magnitude and probability of seasonal low flow from

November-February based on 32 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 29 22 20 18 16 --

3 31 24 21 19 17 --

7 34 26 24 22 20 --

14 39 31 27 24 21 --

30 46 35 30 27 24 --

Duration of daily mean flows based on 33 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

17 21 28 35 44 54 63 79

40% 30% 20% 15% 10% 5% 2% 1%

99 143 251 368 564 865 1,340 1,790

Magnitude and probability of annual high flow

based on 33 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 1,650 3,180 4,610 6,980 9,240 --

3 1,530 2,800 3,870 5,520 6,970 --

7 1,330 2,240 2,930 3,880 4,630 --

15 1,090 1,760 2,250 2,900 3,410 --

30 895 1,380 1,710 2,110 2,410 --

60 700 1,060 1,290 1,570 1,770 --

90 561 833 1,000 1,200 1,330 --

Magnitude and probability of seasonal low flow from

July-October based on 31 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 33 20 16 12 9.2 --

3 34 21 17 13 10 --

7 35 22 17 14 11 --

14 36 23 18 15 12 --

30 40 26 20 16 13 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 187 17 74 39 33

November 165 34 75 31 33

December 155 24 67 29 33

January 104 22 57 20 33

February 184 22 61 29 33

March 187 34 84 37 33

April 518 51 236 129 33

May 1,340 135 692 302 33

June 2,100 113 784 545 33

July 583 27 213 131 33

August 163 13 69 39 33

September 230 19 58 43 34

Annual 363 58 206 80 33
Statistical Summaries of Streamflow 71

06074000 Missouri River at Cascade, Mont.

Site Number 54

LOCATION.--Lat 47°16'10", long 111°41'43" (NAD 27), in SW1⁄4NE1⁄4 sec.35, T.18 N., R.1 W., Cascade County, at highway bridge at Cascade.

DRAINAGE AREA.--18,493 mi2.

PERIOD OF RECORD.--13 years (1902-15).

GAGE.--Chain gage. Altitude of gage is 3,337.8 ft (NGVD 29).

REMARKS.--Diversions for irrigation of about 588,000 acres upstream from station. Flow regulated by Hauser Lake and Canyon Ferry powerplants.

Magnitude and probability of annual low flow

based on 12 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1,890 1,350 1,080 873 -- --

3 2,050 1,570 1,350 1,180 -- --

7 2,260 1,850 1,670 1,530 -- --

14 2,350 1,940 1,760 1,620 -- --

30 2,470 2,040 1,840 1,700 -- --

60 2,740 2,290 2,080 1,910 -- --

90 3,040 2,580 2,340 2,150 -- --

120 3,360 2,790 2,510 2,290 -- --

183 3,610 3,010 2,720 2,480 -- --

Magnitude and probability of seasonal low flow from

March-June based on 13 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 3,640 2,470 1,820 1,330 -- --

3 3,820 2,710 2,090 1,600 -- --

7 3,890 3,350 3,100 2,910 -- --

14 4,170 3,530 3,230 3,000 -- --

30 4,340 3,540 3,260 3,070 -- --

Magnitude and probability of seasonal low flow from

November-February based on 13 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 2,650 2,440 2,350 2,290 -- --

3 2,770 2,540 2,430 2,360 -- --

7 2,870 2,620 2,500 2,400 -- --

14 2,950 2,700 2,560 2,440 -- --

30 3,010 2,740 2,580 2,450 -- --

Duration of daily mean flows based on 13 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

1,630 1,790 2,220 2,450 2,910 3,340 3,740 4,150

40% 30% 20% 15% 10% 5% 2% 1%

4,970 6,030 8,410 10,700 13,900 19,000 25,000 31,600

Magnitude and probability of annual high flow

based on 13 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 25,100 34,800 40,800 47,900 -- --

3 24,600 33,900 39,600 46,200 -- --

7 23,700 32,200 37,300 43,000 -- --

15 22,100 29,800 34,300 39,400 -- --

30 19,900 26,300 30,000 34,200 -- --

60 16,700 20,900 22,700 24,300 -- --

90 14,100 17,100 18,200 19,100 -- --

Magnitude and probability of seasonal low flow from

July-October based on 13 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 2,140 1,590 1,280 1,030 -- --

3 2,170 1,720 1,510 1,360 -- --

7 2,280 1,860 1,690 1,550 -- --

14 2,370 1,960 1,780 1,640 -- --

30 2,570 2,050 1,860 1,710 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 6,320 2,160 4,320 1,470 13

November 6,150 2,900 4,370 1,130 13

December 4,300 2,700 3,480 473 13

January 3,600 2,300 3,130 395 13

February 5,700 3,000 3,500 754 13

March 9,350 3,100 4,810 1,640 13

April 11,500 3,640 7,430 2,110 13

May 15,900 3,940 11,600 3,560 13

June 36,700 8,080 18,900 7,720 13

July 18,700 2,840 7,790 3,930 14

August 6,010 1,800 3,410 1,360 14

September 5,370 1,930 3,360 1,140 14

Annual 7,910 3,660 6,360 1,250 13
72 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06074500 Smith River near White Sulphur Springs, Mont.

Site Number 55

LOCATION.--Lat 46°40'18", long 110°43'24" (NAD 27), near center of sec.33, T.11 N., R.8 E., Meagher County, at Meachen Ranch, 12 mi (revised) northeast 

of White Sulphur Springs.

DRAINAGE AREA.--30.7 mi2.

PERIOD OF RECORD.--11 years (1922-31, 1934-36).

GAGE.--Chain gage. Altitude of gage is 5,600 ft (NGVD 29, from topographic map). Prior to Jun. 27, 1927, staff gage at site 150 ft downstream at same datum.

REMARKS.--A few small diversions for irrigation upstream from station.

Magnitude and probability of annual low flow

based on 10 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 2.9 1.9 1.6 1.4 -- --

3 3.0 2.0 1.7 1.4 -- --

7 3.2 2.2 1.8 1.5 -- --

14 3.5 2.4 2.0 1.7 -- --

30 4.0 2.8 2.3 2.0 -- --

60 4.8 3.4 2.8 2.4 -- --

90 5.7 4.0 3.3 2.9 -- --

120 6.6 4.6 3.9 3.3 -- --

183 7.6 5.3 4.3 3.6 -- --

Magnitude and probability of seasonal low flow from

March-June based on 12 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 5.3 3.0 2.4 2.0 -- --

3 5.5 3.1 2.4 2.0 -- --

7 5.8 3.3 2.5 2.0 -- --

14 6.1 3.7 2.9 2.5 -- --

30 7.5 4.9 4.0 3.5 -- --

Magnitude and probability of seasonal low flow from

November-February based on 10 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 3.8 2.4 1.9 1.5 -- --

3 3.9 2.5 1.9 1.5 -- --

7 4.1 2.7 2.1 1.7 -- --

14 4.2 2.8 2.2 1.8 -- --

30 4.4 3.1 2.5 2.1 -- --

Duration of daily mean flows based on 11 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

2.0 2.4 3.2 4.2 5.4 6.6 7.8 10

40% 30% 20% 15% 10% 5% 2% 1%

13 17 25 34 50 78 123 170

Magnitude and probability of annual high flow

based on 11 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 125 244 338 -- -- --

3 109 209 289 -- -- --

7 97 181 247 -- -- --

15 83 151 205 -- -- --

30 73 131 175 -- -- --

60 62 105 134 -- -- --

90 50 83 104 -- -- --

Magnitude and probability of seasonal low flow from

July-October based on 10 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 4.8 2.7 2.0 1.6 -- --

3 5.1 3.0 2.3 1.9 -- --

7 5.5 3.2 2.5 2.0 -- --

14 6.2 3.7 2.8 2.3 -- --

30 7.2 4.2 3.2 2.5 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 16 4.0 10 4.0 11

November 18 2.9 9.3 4.2 11

December 12 2.9 7.5 3.5 11

January 8.0 3.0 5.5 1.8 11

February 11 2.0 5.8 2.4 12

March 27 3.5 9.5 6.5 12

April 69 9.9 34 23 12

May 135 16 59 33 12

June 250 12 58 65 12

July 64 6.2 22 17 12

August 27 3.8 11 7.7 12

September 18 2.3 8.8 5.2 12

Annual 43 7.3 21 10 11
Statistical Summaries of Streamflow 73

06076690 Smith River near Fort Logan, Mont.

Site Number 56

LOCATION.--Lat 46°47'45", long 111°10'41" (NAD 27), in NE1⁄4SW1⁄4SW1⁄4 sec.13, T.12 N., R.4 E., Meagher County, Hydrologic Unit 10030103, on left bank, 

15 ft downstream from ranch bridge, 1.0 mi upstream from Sheep Creek, 9.0 mi north of Fort Logan, and at river mile 83.7.

DRAINAGE AREA.--846 mi2. 

PERIOD OF RECORD.--October 1977 to September 1996 (discontinued). 

GAGE.--Water-stage recorder. Altitude of gage is 4,400 ft (NGVD 29, from topographic map). 

REMARKS.--Flow slightly regulated by Smith River Reservoir (station number 06075000). Diversions for irrigation of about 19,300 acres upstream from station.

Magnitude and probability of annual low flow

based on 18 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 48 34 27 22 -- --

3 51 36 29 24 -- --

7 57 39 31 26 -- --

14 60 41 33 26 -- --

30 67 45 36 29 -- --

60 74 52 42 35 -- --

90 81 57 47 39 -- --

120 86 63 53 46 -- --

183 89 67 58 52 -- --

Magnitude and probability of seasonal low flow from

March-June based on 19 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 76 50 38 30 -- --

3 80 52 40 32 -- --

7 90 59 45 36 -- --

14 106 69 53 42 -- --

30 125 83 67 56 -- --

Magnitude and probability of seasonal low flow from

November-February based on 18 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 53 41 35 32 -- --

3 58 44 39 35 -- --

7 64 50 43 38 -- --

14 72 55 47 41 -- --

30 80 61 51 44 -- --

Duration of daily mean flows based on 19 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

34 38 48 57 72 84 97 112

40% 30% 20% 15% 10% 5% 2% 1%

127 156 189 236 298 401 590 744

Magnitude and probability of annual high flow

based on 19 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 640 1,310 1,920 2,910 -- --

3 564 1,090 1,550 2,260 -- --

7 468 867 1,200 1,680 -- --

15 384 686 926 1,270 -- --

30 333 560 731 966 -- --

60 276 439 554 703 -- --

90 248 380 469 578 -- --

Magnitude and probability of seasonal low flow from

July-October based on 18 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 62 39 30 24 -- --

3 64 40 32 26 -- --

7 66 42 33 27 -- --

14 68 43 33 27 -- --

30 71 46 37 31 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 272 64 116 48 19

November 237 50 108 39 19

December 220 46 99 38 19

January 146 46 90 28 19

February 373 49 120 72 19

March 399 82 163 76 19

April 363 79 181 83 19

May 798 63 264 170 19

June 833 46 304 201 19

July 445 37 175 122 19

August 276 27 90 53 19

September 299 50 102 56 19

Annual 244 64 151 56 19
74 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06077000 Sheep Creek near White Sulphur Springs, Mont.

Site Number 57

LOCATION.--Lat 46°46'05", long 110°48'33" (NAD 27), SW1⁄4SW1⁄4SE1⁄4 sec.26, T.12 N., R.7 E., Meagher County, Lewis and Clark National Forest, on right 

bank 7 mi upstream from Moose Creek and 16 mi north of White Sulphur Springs.

DRAINAGE AREA.--42.8 mi2. 

PERIOD OF RECORD.--31 years. July 1941 to September 1972 (discontinued).

REVISED RECORDS.--WSP 1309: 1942(M). WSP 1559: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 5,820 ft (NGVD 29, by barometer). Prior to Oct 1, 1942, nonrecording gages at site 1,000 ft upstream at datum 

7.03 ft higher, and Oct. 1, 1942, to May 3, 1955, at site 700 ft upstream at datum 5.33 ft higher. 

REMARKS.--Diversions for irrigation of about 200 acres upstream from station.

Magnitude and probability of annual low flow

based on 30 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 5.7 4.7 4.2 3.8 3.4 --

3 6.0 4.9 4.4 4.0 3.5 --

7 6.6 5.4 4.9 4.4 4.0 --

14 7.1 5.9 5.3 4.8 4.3 --

30 7.8 6.6 6.0 5.5 5.1 --

60 8.9 7.4 6.7 6.2 5.6 --

90 9.5 8.0 7.3 6.8 6.3 --

120 10 8.7 8.0 7.4 6.9 --

183 12 10 9.7 9.2 8.7 --

Magnitude and probability of seasonal low flow from

March-June based on 31 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 6.9 5.8 5.2 4.7 4.2 --

3 7.2 5.9 5.3 4.8 4.2 --

7 7.6 6.3 5.6 5.2 4.6 --

14 7.8 6.6 6.1 5.8 5.5 --

30 8.5 7.3 6.9 6.7 6.5 --

Magnitude and probability of seasonal low flow from

November-February based on 31 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 6.3 5.0 4.4 3.9 3.4 --

3 6.6 5.3 4.7 4.2 3.6 --

7 7.2 5.9 5.2 4.7 4.1 --

14 7.8 6.3 5.6 5.0 4.4 --

30 8.4 6.9 6.2 5.6 5.0 --

Duration of daily mean flows based on 31 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

5.4 5.9 6.5 7.6 9.5 11 13 16

40% 30% 20% 15% 10% 5% 2% 1%

19 26 41 57 82 123 189 243

Magnitude and probability of annual high flow

based on 31 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 191 276 339 427 498 --

3 182 262 321 404 471 --

7 168 240 293 368 429 --

15 151 214 262 327 380 --

30 131 185 224 278 322 --

60 102 138 163 195 220 --

90 82 109 126 147 163 --

Magnitude and probability of seasonal low flow from

July-October based on 30 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 13 11 10 9.7 9.3 --

3 13 11 10 9.8 9.3 --

7 13 11 11 10 9.5 --

14 14 12 11 10 9.9 --

30 15 12 11 11 10 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 34 9.9 16 4.6 31

November 24 8.3 13 3.2 31

December 17 6.1 10 2.3 31

January 13 5.9 9.2 1.9 31

February 14 6.2 9.1 1.9 31

March 21 6.2 9.4 2.8 31

April 47 9.0 21 11 31

May 169 46 95 35 31

June 232 44 115 56 31

July 84 19 43 14 31

August 39 11 23 6.5 32

September 36 10 18 5.0 32

Annual 51 18 32 8.3 31
Statistical Summaries of Streamflow 75

06077500 Smith River near Eden, Mont.

Site Number 58

LOCATION.--Lat 47°11'24", long 111°23'12" (NAD 27), in SW1⁄4SW1⁄4 sec.29, T.17 N., R.3 E., Cascade County, on left bank 0.3 mi upstream from Mullens 

Creek, 2.3 mi upstream from Hound Creek, and 7.7 mi southeast of Eden.

DRAINAGE AREA.--1,594 mi2.

PERIOD OF RECORD.--18 years. April 1951 to September 1969 (discontinued). 

REVISED RECORDS.--WSP 1559: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 3,500 ft (NGVD 29, by barometer). 

REMARKS.--Flow affected by storage in Smith River Reservoir. Diversions for irrigation of about 24,500 acres upstream from station.

Magnitude and probability of annual low flow

based on 17 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 30 12 7.3 4.7 -- --

3 37 16 9.6 6.1 -- --

7 51 24 14 8.8 -- --

14 61 31 20 13 -- --

30 73 42 29 21 -- --

60 85 51 38 30 -- --

90 96 60 46 37 -- --

120 104 68 54 44 -- --

183 110 70 56 47 -- --

Magnitude and probability of seasonal low flow from

March-June based on 18 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 84 51 39 32 -- --

3 88 55 44 36 -- --

7 100 66 54 45 -- --

14 113 76 61 51 -- --

30 160 107 87 72 -- --

Magnitude and probability of seasonal low flow from

November-February based on 18 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 31 14 9.3 6.5 -- --

3 37 19 14 10 -- --

7 51 29 22 17 -- --

14 63 39 29 23 -- --

30 74 49 39 33 -- --

Duration of daily mean flows based on 18 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

21 30 45 61 88 111 136 168

40% 30% 20% 15% 10% 5% 2% 1%

213 299 450 588 836 1,340 2,140 2,760

Magnitude and probability of annual high flow

based on 18 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 1,780 3,300 4,800 7,470 -- --

3 1,660 3,000 4,270 6,450 -- --

7 1,530 2,640 3,620 5,200 -- --

15 1,360 2,290 3,070 4,280 -- --

30 1,210 2,020 2,680 3,660 -- --

60 964 1,580 2,030 2,670 -- --

90 786 1,250 1,580 2,020 -- --

Magnitude and probability of seasonal low flow from

July-October based on 18 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 102 39 19 9.9 -- --

3 105 41 21 11 -- --

7 108 44 23 12 -- --

14 110 48 28 16 -- --

30 114 56 36 25 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 501 52 169 111 18

November 370 57 150 81 18

December 260 31 110 62 18

January 212 43 99 52 18

February 350 49 137 78 18

March 372 63 179 81 18

April 1,160 137 393 258 19

May 2,090 289 955 517 19

June 3,120 279 1,190 869 19

July 833 36 374 222 19

August 344 16 158 93 19

September 537 30 154 124 19

Annual 614 107 338 159 18
76 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06078200 Missouri River near Ulm, Mont.

Site Number 59

LOCATION.--Lat 47°26'06", long 111°23'07" (NAD 27), in NE1⁄4NW1⁄4NW1⁄4 sec.5, T.19 N., R.3 E., Cascade County, Hydrologic Unit 10030102, on left bank 

5.6 mi east of Ulm, 9.1 mi downstream from Smith River, and at river mile 2,140.4.

DRAINAGE AREA.--20,941 mi2.

PERIOD OF RECORD.--August 1957 to current year (2002).

GAGE.--Water-stage recorder. Altitude of gage is 3,313.27 ft (NGVD 29). 

REMARKS.--Flow regulated by 10 smaller irrigation reservoirs and powerplants, Clark Canyon Reservoir (station number 06015300), and Canyon Ferry Lake 

(station number 06058500). Diversions for irrigation of about 630,400 acres upstream from station. U.S. Army Corps of Engineers satellite telemeter at station. 

Magnitude and probability of annual low flow

based on 44 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 3,390 2,690 2,380 2,150 1,910 --

3 3,510 2,820 2,520 2,300 2,070 --

7 3,670 2,960 2,650 2,420 2,190 --

14 3,770 3,080 2,780 2,550 2,330 --

30 3,950 3,210 2,880 2,640 2,400 --

60 4,160 3,370 3,020 2,770 2,510 --

90 4,380 3,520 3,150 2,880 2,610 --

120 4,550 3,670 3,290 3,010 2,730 --

183 4,880 3,930 3,510 3,190 2,850 --

Magnitude and probability of seasonal low flow from

March-June based on 45 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 4,290 3,150 2,660 2,310 1,970 --

3 4,410 3,280 2,810 2,480 2,150 --

7 4,580 3,420 2,930 2,580 2,240 --

14 4,810 3,620 3,110 2,750 2,390 --

30 5,160 3,910 3,380 2,990 2,610 --

Magnitude and probability of seasonal low flow from

November-February based on 45 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 4,120 3,440 3,140 2,920 2,690 --

3 4,280 3,570 3,260 3,020 2,780 --

7 4,460 3,730 3,390 3,130 2,850 --

14 4,580 3,810 3,460 3,190 2,900 --

30 4,750 3,930 3,540 3,250 2,950 --

Duration of daily mean flows based on 45 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

2,440 2,690 3,180 3,450 3,990 4,540 5,100 5,670

40% 30% 20% 15% 10% 5% 2% 1%

6,310 7,210 8,120 8,580 10,500 14,300 19,600 22,900

Magnitude and probability of annual high flow

based on 45 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 14,900 21,900 26,000 30,700 33,900 --

3 14,500 21,500 25,700 30,500 33,700 --

7 13,900 20,700 24,900 29,900 33,300 --

15 13,000 19,600 23,800 29,100 32,900 --

30 11,700 17,600 21,500 26,400 30,000 --

60 10,300 14,800 17,600 21,000 23,400 --

90 9,360 13,000 15,300 17,900 19,800 --

Magnitude and probability of seasonal low flow from

July-October based on 44 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 3,530 2,780 2,460 2,230 2,000 --

3 3,670 2,920 2,600 2,360 2,130 --

7 3,830 3,070 2,740 2,500 2,260 --

14 3,940 3,170 2,850 2,610 2,380 --

30 4,080 3,270 2,920 2,670 2,420 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 10,000 2,200 4,160 1,390 45

November 7,950 2,920 4,690 1,240 45

December 6,790 3,020 4,650 1,060 45

January 6,760 3,100 5,080 971 45

February 8,000 3,000 5,150 1,220 45

March 8,820 2,820 5,010 1,440 45

April 9,320 2,370 5,290 1,690 45

May 15,300 2,520 6,380 2,880 45

June 17,500 1,700 7,420 4,100 45

July 9,930 2,200 4,860 1,810 45

August 7,280 2,230 4,220 1,300 46

September 9,340 1,900 3,940 1,370 46

Annual 5,800 1,700 3,220 787 45
Statistical Summaries of Streamflow 77

06078500 North Fork Sun River near Augusta, Mont.

Site Number 60

LOCATION.--Lat 47°38'27", long 112°51'34" (NAD 27), in SW1⁄4SW1⁄4SW1⁄4 sec.23, T.22 N., R.10 W., Teton County, Hydrologic Unit 10030104, on left bank 

400 ft upstream from Arsenic Creek, 1 mi upstream from South Fork and Gibson Reservoir, and 25 mi northwest of Augusta. 

DRAINAGE AREA.--258 mi2. 

PERIOD OF RECORD.--May 1911 to September 1912, October 1945 to September 1968, May 1989 to September 1993 (discontinued, seasonal records only). 

Monthly discharge only for some periods, published in WSP 1309. Prior to October 1959, published as "North Fork of North Fork Sun River near Augusta."

GAGE.--Water-stage recorder. Altitude of gage is 4,785.72 ft (NGVD 29, levels by Bureau of Reclamation). May 27, 1911, to Sept. 30, 1912, staff gage near 

present site at different datum. Oct. 1, 1945, to July 22, 1946, wire-weight gage at site 0.75 mi downstream at different datum. July 23, 1946, to June, 8, 1964, 

water-stage recorder at present site and datum. Sept. 12, 1964, to Sept. 30, 1968, water-stage recorder at present site and datum. 

REMARKS.--No known regulation or diversion upstream from station.

Magnitude and probability of annual low flow

based on 23 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 40 35 32 31 -- --

3 42 36 33 31 -- --

7 44 39 36 34 -- --

14 48 43 41 39 -- --

30 54 48 45 43 -- --

60 62 55 51 49 -- --

90 69 60 56 54 -- --

120 75 65 61 58 -- --

183 89 74 68 64 -- --

Magnitude and probability of seasonal low flow from

March-June based on 24 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 48 40 37 35 -- --

3 50 42 39 37 -- --

7 52 45 42 40 -- --

14 57 49 46 43 -- --

30 64 54 50 47 -- --

Magnitude and probability of seasonal low flow from

November-February based on 24 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 44 37 33 31 -- --

3 46 38 34 32 -- --

7 50 41 37 35 -- --

14 54 45 42 39 -- --

30 59 51 47 44 -- --

Duration of daily mean flows based on 24 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

38 44 50 57 71 85 102 125

40% 30% 20% 15% 10% 5% 2% 1%

168 255 527 837 1,240 1,830 2,480 2,870

Magnitude and probability of annual high flow

based on 24 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 2,500 3,710 5,290 8,790 -- --

3 2,360 3,450 4,680 7,090 -- --

7 2,220 3,090 3,880 5,180 -- --

15 2,050 2,710 3,210 3,910 -- --

30 1,830 2,320 2,650 3,050 -- --

60 1,440 1,770 1,970 2,190 -- --

90 1,110 1,350 1,490 1,660 -- --

Magnitude and probability of seasonal low flow from

July-October based on 28 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 90 73 66 61 56 --

3 92 77 70 65 60 --

7 95 79 72 67 62 --

14 97 80 73 68 63 --

30 102 83 76 70 65 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 286 72 123 49 28

November 191 65 102 30 24

December 152 59 83 24 24

January 96 43 67 13 24

February 100 47 66 14 24

March 113 44 68 17 24

April 935 76 265 189 28

May 1,920 688 1,260 329 30

June 3,220 455 1,480 613 30

July 1,010 203 486 234 30

August 249 95 173 44 30

September 291 84 130 46 30

Annual 468 253 360 68 24
78 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06080000 Sun River near Augusta, Mont.

Site Number 61

LOCATION.--Lat 47°37', long 112°42' (NAD 27), in NW1⁄4 sec.36, T.22 N., R.9 W., Lewis and Clark County, about 150 ft upstream from diversion dam and 18 mi 

northwest of Augusta.

DRAINAGE AREA.--609 mi2.

PERIOD OF RECORD.--37 years (1889-90, 1904-40).

GAGE.--Water-stage recorder. Altitude of gage is 4,474 ft (NGVD 29, levels by Bureau of Reclamation). Prior to Jan, 1, 1916, staff or chain gages at site 8 mi 

downstream at different datum. Jan. 1, 1916, to Sept. 30, 1936, slope gage on diversion dam 150 ft downstream at same datum.

REMARKS.--Flow regulated for 1916-36 and Pishkun Canal, data furnished by Bureau of Reclamation. Records for 1929-36 not previously published by U.S. 

Geological Survey.

Magnitude and probability of annual low flow

based on 24 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 128 74 49 33 -- --

3 130 91 73 60 -- --

7 136 102 87 76 -- --

14 141 109 96 86 -- --

30 149 117 104 94 -- --

60 181 139 120 107 -- --

90 197 148 127 112 -- --

120 220 162 138 121 -- --

183 259 193 162 140 -- --

Magnitude and probability of seasonal low flow from

March-June based on 25 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 154 103 67 43 24 --

3 159 119 103 92 82 --

7 167 127 112 101 91 --

14 172 131 115 105 95 --

30 183 137 122 113 104 --

Magnitude and probability of seasonal low flow from

November-February based on 25 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 147 106 90 79 69 --

3 152 111 95 84 74 --

7 159 115 99 87 76 --

14 164 119 102 90 78 --

30 170 126 109 97 85 --

Duration of daily mean flows based on 25 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

96 103 125 145 180 223 270 330

40% 30% 20% 15% 10% 5% 2% 1%

402 557 1,130 1,690 2,490 3,890 5,750 7,540

Magnitude and probability of annual high flow

based on 25 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 6,600 10,500 13,800 18,700 22,900 --

3 6,200 9,390 11,700 14,800 17,200 --

7 5,650 8,310 10,100 12,200 13,800 --

15 4,900 7,040 8,440 10,200 11,400 --

30 4,160 5,860 6,900 8,120 8,970 --

60 3,220 4,380 5,070 5,860 6,390 --

90 2,530 3,420 3,950 4,560 4,970 --

Magnitude and probability of seasonal low flow from

July-October based on 25 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 249 151 106 74 47 --

3 251 156 111 80 53 --

7 252 164 127 101 76 --

14 253 177 145 122 99 --

30 264 195 166 145 125 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 544 128 301 105 25

November 682 120 297 135 25

December 450 100 229 88 25

January 521 96 204 95 25

February 421 100 208 90 25

March 579 102 222 112 25

April 1,900 200 686 405 25

May 6,260 1,120 2,760 1,140 25

June 7,840 1,000 3,560 1,790 25

July 4,350 264 1,250 850 26

August 982 182 442 199 26

September 714 59 321 132 26

Annual 1,620 444 876 285 25
Statistical Summaries of Streamflow 79

06080900 Sun River below diversion dam, near Augusta, Mont.

Site Number 62

LOCATION.--Lat 47°37'10", long 112°41'28" (NAD 27), near center of east line of sec.36, T.22 N., R.9 W., Lewis and Clark County, Hydrologic Unit 10030104, 

Lewis and Clark National Forest, on road bridge 1.0 mi downstream from diversion dam, 16.5 mi northwest of Augusta, and at river mile 96.4 (revised). 

DRAINAGE AREA.--609 mi2. 

PERIOD OF RECORD.--September 1967 to Sept. 30, 1980 (discontinued). 

GAGE.--Water-stage recorder. Altitude of gage is 14,370 ft (NGVD 29, from topographic map). 

REMARKS.--Flow regulated by Gibson Dam (station number 06079500). Diversions upstream from station into Pishkun Canal and Willow Creek feeder canal 

for irrigation of about 91,000 acres downstream from station. 

Magnitude and probability of annual low flow

based on 12 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 40 29 24 20 -- --

3 44 31 25 21 -- --

7 46 33 27 23 -- --

14 50 35 29 24 -- --

30 60 44 36 31 -- --

60 70 55 48 42 -- --

90 84 64 56 50 -- --

120 95 69 60 53 -- --

183 116 81 67 57 -- --

Magnitude and probability of seasonal low flow from

March-June based on 13 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 56 32 24 20 -- --

3 61 36 27 22 -- --

7 68 40 30 24 -- --

14 81 47 35 27 -- --

30 100 53 38 31 -- --

Magnitude and probability of seasonal low flow from

November-February based on 12 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 69 42 32 25 -- --

3 73 46 35 27 -- --

7 82 50 37 28 -- --

14 89 53 38 28 -- --

30 99 63 48 39 -- --

Duration of daily mean flows based on 13 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

30 36 47 56 72 87 112 141

40% 30% 20% 15% 10% 5% 2% 1%

167 201 323 505 1,140 2,260 4,010 5,420

Magnitude and probability of annual high flow

based on 13 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 5,020 10,900 14,800 19,200 -- --

3 4,730 9,580 12,500 15,400 -- --

7 3,990 7,540 9,460 11,300 -- --

15 3,170 5,820 7,250 8,620 -- --

30 2,470 4,460 5,540 6,570 -- --

60 1,710 3,000 3,720 4,430 -- --

90 1,270 2,180 2,670 3,150 -- --

Magnitude and probability of seasonal low flow from

July-October based on 12 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 51 34 27 23 -- --

3 53 36 30 25 -- --

7 55 39 33 28 -- --

14 60 43 37 33 -- --

30 71 59 54 51 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 470 50 139 110 13

November 468 58 141 107 13

December 295 41 136 71 13

January 238 56 133 56 13

February 198 48 125 51 13

March 276 40 138 78 13

April 910 35 279 293 13

May 3,600 289 1,330 1,020 13

June 6,260 230 2,180 1,640 13

July 1,680 71 423 467 13

August 282 64 137 71 13

September 299 60 120 66 13

Annual 818 112 440 210 13
80 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06081500 Willow Creek near Augusta, Mont.

Site Number 63

LOCATION.--Lat 47°33', long 112°28' (NAD 27), in NW1⁄4SW1⁄4 sec.26, T.21 N., R.7 W., Lewis and Clark County, just downstream from Little Willow Creek 

and 5 mi (revised) northwest of Augusta.

DRAINAGE AREA.--96.1 mi2.

PERIOD OF RECORD.--20 years (1905-25).

GAGE.--Chain gage. Altitude of gage is 4,150 ft (NGVD 29, by barometer). Prior to Aug. 22, 1905, staff gage at same site and datum.

REMARKS.--Diversions for irrigation of about 2,000 acres upstream from station.

Magnitude and probability of annual low flow

based on 18 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 4.6 1.5 0.49 0.00 -- --

3 4.6 1.6 .75 .37 -- --

7 5.0 1.8 .87 .44 -- --

14 5.7 2.1 1.0 .50 -- --

30 6.9 2.6 1.2 .59 -- --

60 7.6 3.0 1.5 .80 -- --

90 8.3 3.6 2.0 1.1 -- --

120 9.4 4.2 2.4 1.4 -- --

183 11 5.0 3.0 1.8 -- --

Magnitude and probability of seasonal low flow from

March-June based on 19 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 6.9 3.1 1.8 1.2 -- --

3 7.4 3.2 1.9 1.2 -- --

7 7.9 3.5 2.1 1.3 -- --

14 9.0 4.3 2.8 1.8 -- --

30 11 6.2 4.3 3.1 -- --

Magnitude and probability of seasonal low flow from

November-February based on 20 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 5.9 3.0 1.9 1.2 -- --

3 6.0 3.2 2.1 1.5 -- --

7 6.2 3.4 2.3 1.6 -- --

14 6.4 3.5 2.3 1.6 -- --

30 6.9 3.7 2.5 1.7 -- --

Duration of daily mean flows based on 19 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

0.77 1.2 2.1 4.2 6.4 7.9 10 13

40% 30% 20% 15% 10% 5% 2% 1%

17 23 32 42 57 90 183 294

Magnitude and probability of annual high flow

based on 19 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 165 429 707 1,200 -- --

3 144 365 599 1,020 -- --

7 123 306 502 860 -- --

15 102 249 405 692 -- --

30 83 187 292 477 -- --

60 65 137 203 313 -- --

90 54 108 156 233 -- --

Magnitude and probability of seasonal low flow from

July-October based on 19 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 7.1 2.1 0.67 0.00 -- --

3 7.3 2.2 .97 .45 -- --

7 7.7 2.5 1.1 .54 -- --

14 8.3 2.7 1.2 .56 -- --

30 9.2 2.9 1.3 .61 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 30 0.86 13 7.8 20

November 24 1.0 12 6.2 20

December 26 4.6 10 5.3 20

January 37 3.7 10 8.1 20

February 70 1.7 14 17 20

March 48 4.7 16 11 20

April 50 8.2 24 13 20

May 320 4.8 68 69 19

June 363 1.9 99 107 20

July 211 1.0 39 48 20

August 53 .46 18 15 20

September 35 .23 13 10 20

Annual 77 7.2 28 20 19
Statistical Summaries of Streamflow 81

06084500 Elk Creek at Augusta, Mont.

Site Number 64

LOCATION.--Lat 47°29', long 111°23' (NAD 27), in NW1⁄4 SE1⁄4 sec.17, T.20 N., R.6 W., Lewis and Clark County, at old highway bridge 0.5 mi from Augusta 

and 6 mi upstream from mouth.

DRAINAGE AREA.--157 mi2.

PERIOD OF RECORD.--20 years (1904-24).

GAGE.--Staff gage. Altitude of gage is 4,070 ft (NGVD 29, by barometer). Apr. 20, 1907, to December 1908, staff gage at site 300 ft upstream at different datum.

REMARKS.--Diversions for irrigation of about 4,500 acres upstream from station.

Magnitude and probability of annual low flow

based on 19 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 11 2.0 0.00 0.00 -- --

3 13 2.2 .00 .00 -- --

7 14 2.3 .41 .00 -- --

14 16 3.8 1.0 .00 -- --

30 17 5.5 2.4 1.0 -- --

60 20 8.0 4.2 2.3 -- --

90 23 9.9 5.5 3.2 -- --

120 28 13 8.3 5.2 -- --

183 32 18 13 9.2 -- --

Magnitude and probability of seasonal low flow from

March-June based on 20 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 24 6.0 1.9 0.00 -- --

3 25 7.4 3.2 1.4 -- --

7 31 13 6.8 3.8 -- --

14 33 16 10 6.9 -- --

30 36 19 13 9.0 -- --

Magnitude and probability of seasonal low flow from

November-February based on 19 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 22 16 13 12 -- --

3 22 16 13 12 -- --

7 22 16 14 12 -- --

14 23 16 14 12 -- --

30 23 17 14 12 -- --

Duration of daily mean flows based on 20 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

0.74 2.5 7.2 14 22 28 32 42

40% 30% 20% 15% 10% 5% 2% 1%

53 65 94 128 206 351 678 1,020

Magnitude and probability of annual high flow

based on 20 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 833 1,920 2,740 3,800 -- --

3 743 1,620 2,240 3,010 -- --

7 630 1,350 1,890 2,560 -- --

15 498 1,040 1,440 1,960 -- --

30 386 769 1,050 1,420 -- --

60 278 530 714 954 -- --

90 215 395 528 707 -- --

Magnitude and probability of seasonal low flow from

July-October based on 20 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 13 2.2 0.00 0.00 -- --

3 16 2.3 .00 .00 -- --

7 16 2.4 .51 .00 -- --

14 18 3.9 1.1 .00 -- --

30 21 5.6 2.4 1.1 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 99 14 46 25 21

November 99 15 44 23 21

December 60 10 34 15 20

January 65 10 28 15 20

February 97 12 32 19 20

March 115 20 47 27 20

April 164 26 68 42 20

May 965 10 262 214 20

June 1,280 4.9 385 377 20

July 417 2.6 105 100 20

August 119 1.0 45 37 20

September 114 .87 38 30 20

Annual 212 20 94 56 20
82 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06085800 Sun River at Simms, Mont.

Site Number 65

LOCATION.--Lat 47°30'06", long 111°55'56" (NAD 27), in NW1⁄4NW1⁄4SE1⁄4 sec.12, T.20 N., R.3 W., Cascade County, Hydrologic Unit 10030104, on left bank 

5 ft downstream from bridge on Montana Secondary Highway 565, 0.7 mi downstream from Simms Creek, 0.7 mi north of Simms, and at river mile 45.0.

DRAINAGE AREA.--1,320 mi2.

PERIOD OF RECORD.--May to June 1953 (in WSP 1320-B), May to June 1964 (in WSP 1840-B), April 1966 to September 1979, April 1997 to current year 

(2002).

REVISED RECORDS.--WDR MT-75-1: 1964 (M).

GAGE.--Water-stage recorder. Altitude of gage is 3,570 ft (NGVD 29). May 1941 to October 1965, nonrecording gage at different datum. April 1966 to 

September 1979, water-stage recorder at site about 500 ft downstream at different datum.

REMARKS.--Flow regulated by Gibson, Pishkun, Willow Creek, and Nilan Reservoirs. Diversions for irrigation of about 105,000 acres upstream from station. 

Bureau of Reclamation satellite telemeter at station. 

Magnitude and probability of annual low flow

based on 16 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 49 33 26 21 -- --

3 54 37 30 25 -- --

7 62 44 36 30 -- --

14 75 50 40 33 -- --

30 88 59 47 39 -- --

60 110 75 61 51 -- --

90 127 88 72 61 -- --

120 145 101 84 72 -- --

183 168 119 100 86 -- --

Magnitude and probability of seasonal low flow from

March-June based on 18 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 76 43 31 24 -- --

3 87 50 38 29 -- --

7 100 59 45 36 -- --

14 119 69 52 42 -- --

30 151 88 66 53 -- --

Magnitude and probability of seasonal low flow from

November-February based on 18 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 93 64 53 44 -- --

3 100 76 66 59 -- --

7 117 89 78 69 -- --

14 134 103 90 80 -- --

30 153 114 98 86 -- --

Duration of daily mean flows based on 18 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

38 46 63 84 117 143 167 190

40% 30% 20% 15% 10% 5% 2% 1%

228 266 368 553 1,060 2,230 4,140 5,970

Magnitude and probability of annual high flow

based on 18 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 4,180 10,100 14,900 21,200 -- --

3 3,880 9,200 13,300 18,600 -- --

7 3,380 7,560 10,600 14,300 -- --

15 2,690 5,890 8,160 10,900 -- --

30 2,130 4,590 6,330 8,430 -- --

60 1,420 2,970 4,120 5,610 -- --

90 1,080 2,150 2,950 3,990 -- --

Magnitude and probability of seasonal low flow from

July-October based on 18 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 55 35 28 23 -- --

3 61 40 32 27 -- --

7 70 46 38 32 -- --

14 84 54 42 34 -- --

30 100 64 49 40 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 519 89 211 105 18

November 596 120 224 103 18

December 456 101 199 83 18

January 314 122 197 59 18

February 291 96 194 66 18

March 473 104 223 106 18

April 1,120 81 327 273 20

May 4,120 72 1,180 1,100 20

June 8,560 109 2,320 2,140 20

July 2,160 54 418 511 20

August 383 49 168 97 20

September 422 49 151 86 20

Annual 1,180 123 478 282 18
Statistical Summaries of Streamflow 83

06086000 Sun River at Fort Shaw, Mont.

Site Number 66

LOCATION.--Lat 47°31'10", long 111°48'50" (NAD 27), on west line of SW1⁄4 sec.1, T.20 N., R.2 W., Cascade County, at highway bridge at Fort Shaw.

DRAINAGE AREA.--1,417 mi2.

PERIOD OF RECORD.--13 years (1912-28).

GAGE.--Water-stage recorder. Altitude of gage is 3,465 ft (NGVD 29, from topographic map). Prior to May 20, 1925, chain or staff gages at several sites within 

0.25 mi of present site at different datums.

REMARKS.--Numerous diversions for irrigation upstream and downstream from station. Diversion to Pishkun Canal and Pishkun Reservoir began in 1916. Some 

regulation in Willow Creek Reservoir.

Magnitude and probability of annual low flow

based on 15 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 121 72 53 40 -- --

3 142 89 67 52 -- --

7 171 110 82 62 -- --

14 187 129 102 82 -- --

30 203 146 119 100 -- --

60 227 172 149 133 -- --

90 259 194 166 145 -- --

120 290 218 186 161 -- --

183 320 236 198 171 -- --

Magnitude and probability of seasonal low flow from

March-June based on 16 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 204 121 88 65 -- --

3 217 139 107 85 -- --

7 237 181 158 142 -- --

14 251 199 181 168 -- --

30 270 221 205 195 -- --

Magnitude and probability of seasonal low flow from

November-February based on 16 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 208 133 98 73 -- --

3 218 142 105 78 -- --

7 232 152 111 81 -- --

14 234 168 136 112 -- --

30 236 188 171 158 -- --

Duration of daily mean flows based on 16 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

100 127 162 198 233 268 322 377

40% 30% 20% 15% 10% 5% 2% 1%

474 637 1,100 1,700 2,530 3,980 6,030 7,910

Magnitude and probability of annual high flow

based on 16 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 6,580 10,000 12,700 16,500 -- --

3 6,160 9,210 11,400 14,300 -- --

7 5,620 8,310 10,200 12,600 -- --

15 4,800 7,170 8,860 11,100 -- --

30 4,090 6,100 7,480 9,240 -- --

60 3,190 4,620 5,540 6,680 -- --

90 2,500 3,550 4,230 5,080 -- --

Magnitude and probability of seasonal low flow from

July-October based on 15 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 179 91 61 44 -- --

3 197 107 75 55 -- --

7 216 121 87 65 -- --

14 236 136 103 83 -- --

30 263 159 122 102 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 708 181 402 150 16

November 622 165 369 125 16

December 423 190 297 79 16

January 600 170 280 104 16

February 824 168 312 182 16

March 669 200 310 123 16

April 1,160 308 755 259 16

May 5,220 1,490 2,980 1,010 16

June 7,630 723 3,450 1,990 17

July 5,140 103 1,150 1,170 17

August 938 120 397 223 17

September 845 134 382 185 16

Annual 1,770 415 929 356 16
84 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06088300 Muddy Creek near Vaughn, Mont.

Site Number 67

LOCATION.--Lat 47°37'30", long 111°38'05" (NAD 27), in NE1⁄4NE1⁄4NW1⁄4 sec.32, T.22 N., R.1 E., Cascade County, Hydrologic Unit 10030104, on left bank 

200 ft downstream from bridge on county road, 6.2 mi northwest of Vaughn and at river mile 14.6.

DRAINAGE AREA.--282 mi2.

PERIOD OF RECORD.--July 1968 to September 1987, March 1996 to current year (2002).

GAGE.--Water-stage recorder. Altitude of gage is 3,441.79 ft (NGVD 29, levels by U.S. Army Corps of Engineers).

REMARKS.--Natural flow increased by wastage from Greenfield Irrigation Project. Diversions for irrigation of about 400 acres upstream from station and pumped 

diversions from Muddy Creek upstream from station in SW1⁄4 sec.2, T.22 N., R.1 W, to supplement water supply for Benton Lake Wildlife Refuge. Bureau of 

Reclamation satellite telemeter at station.

Magnitude and probability of annual low flow

based on 24 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 17 13 11 9.6 -- --

3 18 14 13 11 -- --

7 20 16 14 13 -- --

14 22 18 16 14 -- --

30 25 21 19 17 -- --

60 29 24 22 21 -- --

90 36 29 26 24 -- --

120 40 34 31 29 -- --

183 65 52 45 40 -- --

Magnitude and probability of seasonal low flow from

March-June based on 26 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 21 16 13 12 9.6 --

3 23 18 15 13 11 --

7 25 19 17 15 13 --

14 27 22 19 18 16 --

30 30 25 23 23 22 --

Magnitude and probability of seasonal low flow from

November-February based on 25 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 19 15 13 11 9.2 --

3 20 16 14 12 11 --

7 22 18 16 14 12 --

14 24 19 17 15 13 --

30 28 22 19 17 15 --

Duration of daily mean flows based on 25 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

17 19 23 27 33 41 51 63

40% 30% 20% 15% 10% 5% 2% 1%

88 138 189 225 262 333 393 491

Magnitude and probability of annual high flow

based on 25 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 583 939 1,260 1,780 2,270 --

3 509 742 924 1,190 1,410 --

7 403 538 638 777 890 --

15 330 400 445 501 543 --

30 295 352 387 430 461 --

60 270 314 337 361 376 --

90 242 285 309 335 353 --

Magnitude and probability of seasonal low flow from

July-October based on 25 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 54 44 40 37 34 --

3 56 46 41 38 35 --

7 58 48 43 40 37 --

14 61 50 45 42 39 --

30 71 57 51 47 42 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 145 41 77 23 25

November 71 35 54 8.1 25

December 58 22 42 8.8 25

January 60 19 33 11 25

February 65 18 36 12 25

March 238 23 60 61 26

April 162 21 41 27 26

May 264 56 115 47 26

June 455 101 200 67 26

July 367 137 259 51 27

August 402 138 245 68 27

September 218 46 136 46 27

Annual 160 77 109 21 25
Statistical Summaries of Streamflow 85

06088500 Muddy Creek at Vaughn, Mont.

Site Number 68

LOCATION.--Lat 47°33'40", long 111°32'15" (NAD 27), in SW1⁄4SE1⁄4NE1⁄4 sec.24, T.21 N., R.1 E., Cascade County, Hydrologic Unit 10030104, on left bank at 

Vaughn, and at river mile 1.1.

DRAINAGE AREA.--314 mi2.

PERIOD OF RECORD.--June 1925 to January 1926, April 1934 to September 1968, July 1971 to current year (2002).

REVISED RECORDS.--WSP 856: 1937. WSP 1509: 1934-35, 1941(M). WSP 1559: 1956. WSP 1629: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 3,330 ft (NGVD 29). May 21, 1925, to Feb. 8, 1926, nonrecording gage at site 500 ft downstream at different 

datum. Apr. 19, 1925, to Sept. 30, 1955, at previous site at datum. May 18, 1955, to Apr. 25, 1960, and Sept. 24, 1962, to Sept. 30, 1968, auxiliary crest-stage 

gage. Oct. 1, 1955, to Sept. 30, 1968, nonrecording gage at bridge 670 ft upstream at previous datum. July 1, 1971, to May 9, 1996, 700 ft upstream at previous 

datum.

REMARKS.--Natural flow increased by wastage from Sun River Canal and by return flow from irrigation. Diversions for irrigation of about 700 acres upstream 

from station. Bureau of Reclamation satellite telemeter at station.

Magnitude and probability of annual low flow

based on 63 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 16 12 9.7 8.0 6.3 5.3

3 17 13 11 8.9 7.3 6.3

7 19 14 12 11 8.9 7.8

14 22 17 14 13 11 9.6

30 26 21 18 16 13 12

60 31 25 22 20 17 16

90 37 30 27 25 23 21

120 43 36 33 31 28 27

183 78 63 56 49 43 39

Magnitude and probability of seasonal low flow from

March-June based on 65 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 20 14 11 9.4 7.5 6.3

3 21 15 12 10 8.3 7.1

7 23 17 15 13 11 10

14 25 20 18 16 15 14

30 30 24 22 21 20 19

Magnitude and probability of seasonal low flow from

November-February based on 65 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 19 14 11 9.5 7.7 6.6

3 19 15 12 11 8.8 7.7

7 21 16 14 12 9.5 8.2

14 24 18 15 13 11 9.4

30 29 22 18 16 13 11

Duration of daily mean flows based on 65 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

14 17 22 26 34 42 55 73

40% 30% 20% 15% 10% 5% 2% 1%

109 162 222 256 305 365 463 511

Magnitude and probability of annual high flow

based on 65 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 553 916 1,280 1,950 2,640 3,560

3 474 716 943 1,330 1,700 2,170

7 402 557 696 920 1,130 1,380

15 353 457 537 652 748 854

30 329 405 448 496 528 557

60 302 366 396 424 440 454

90 278 336 364 391 407 420

Magnitude and probability of seasonal low flow from

July-October based on 65 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 70 49 38 28 19 14

3 73 53 41 31 22 17

7 76 56 45 36 27 22

14 81 60 49 40 31 26

30 98 72 59 49 40 34

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 200 26 100 31 66

November 113 31 60 13 66

December 131 17 44 15 66

January 68 17 34 11 65

February 97 10 37 14 65

March 283 22 55 44 65

April 182 18 42 23 65

May 305 53 138 54 65

June 480 86 237 79 66

July 416 52 275 81 67

August 488 44 284 82 67

September 270 40 176 51 67

Annual 185 61 125 25 65
86 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06089000 Sun River near Vaughn, Mont.

Site Number 69

LOCATION.--Lat 47°31'37", long 111°29'05" (NAD 27), in NW1⁄4SE1⁄4SW1⁄4 sec.33, T.21 N., R.2 E., Cascade County, Hydrologic Unit 10030104, on right bank 

3.7 mi downstream from Muddy Creek, 3.6 mi southeast of Vaughn, and at river mile 13.6.

DRAINAGE AREA.--1,849 mi2.

PERIOD OF RECORD.--July to October 1897 (gage heights and discharge measurements only, published as "near Great Falls"), April 1934 to current year (2002). 

Monthly discharge only for April 1934, published in WSP 1309.

REVISED RECORDS.--WSP 786: 1934. WSP 1729: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 3,317.12 ft (NGVD 29). July 11 to Oct. 30, 1897, nonrecording gage at site 0.8 mi upstream at different datum. 

Apr. 19 to Aug. 3, 1934, non-recording gage at present site and datum.

REMARKS.--Flow regulated by Gibson, Pishkun, Willow Creek, and Nilan Reservoirs. Diversion for irrigation of about 110,000 acres upstream from station. 

U.S. Army Corps of Engineers satellite telemeter at station.

Magnitude and probability of annual low flow

based on 67 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 133 88 68 53 39 31

3 141 95 74 58 44 35

7 153 106 84 69 53 45

14 168 120 99 83 67 57

30 191 138 114 96 78 68

60 216 159 133 114 95 84

90 251 182 152 131 109 97

120 268 198 169 148 127 114

183 319 240 205 179 154 138

Magnitude and probability of seasonal low flow from

March-June based on 68 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 173 105 77 58 42 33

3 182 113 84 64 47 37

7 194 124 96 76 58 48

14 212 141 114 95 77 67

30 243 160 131 112 94 84

Magnitude and probability of seasonal low flow from

November-February based on 68 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 145 101 82 69 56 49

3 152 109 90 77 65 57

7 167 120 99 85 71 62

14 185 132 109 93 77 67

30 210 150 123 105 86 75

Duration of daily mean flows based on 68 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

95 113 143 176 224 268 318 369

40% 30% 20% 15% 10% 5% 2% 1%

445 528 719 951 1,460 2,740 4,480 5,900

Magnitude and probability of annual high flow

based on 68 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 5,180 9,310 12,200 15,700 18,200 20,700

3 4,840 8,480 10,800 13,500 15,400 17,000

7 4,220 7,150 8,890 10,800 12,000 13,000

15 3,430 5,810 7,230 8,770 9,750 10,600

30 2,740 4,670 5,860 7,220 8,100 8,890

60 1,950 3,260 4,080 5,040 5,690 6,280

90 1,540 2,470 3,070 3,770 4,260 4,710

Magnitude and probability of seasonal low flow from

July-October based on 68 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 267 194 160 135 110 96

3 275 203 170 145 120 105

7 290 215 180 154 128 113

14 308 231 195 169 142 125

30 342 261 225 198 170 154

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 779 143 381 134 68

November 908 149 339 138 68

December 896 114 301 141 68

January 656 66 256 103 68

February 601 82 266 104 68

March 868 133 327 166 68

April 3,000 93 501 484 69

May 4,330 87 1,580 1,020 69

June 8,010 280 2,560 1,900 69

July 2,510 265 787 479 69

August 1,020 250 566 170 69

September 1,040 164 444 149 69

Annual 1,310 210 687 281 68
Statistical Summaries of Streamflow 87

06090300 Missouri River near Great Falls, Mont.

Site Number 70

LOCATION.--Lat 47°35'04", long 111°03'35" (NAD 27), in SW1⁄4SE1⁄4SW1⁄4 sec.11, T.21 N., R.5 E., Cascade County, Hydrologic Unit 10030102, on left bank 

700 ft downstream from Morony Dam, 12.6 mi northeast of Great Falls, and at river mile 2,105.4.

DRAINAGE AREA.--23,292 mi2.

PERIOD OF RECORD.--May to July 1953 (in WSP 1320-B), October 1956 to current year (2002).

GAGE.--Water-stage recorder. Altitude of gage is 2,807.21 ft (NGVD 29). Prior to July 27, 1977, nonrecording gage at same site at datum 2.00 ft higher. July 27, 

1977, to May 26, 1987, at site 600 ft upstream at datum 2.00 ft higher. October 1971 to July 27, 1977, discharges were obtained from the Montana Power 

Company at Rainbow Dam 7.05 mi upstream. Prior to October 1971, Foxboro meters were used for determining discharge through powerplant. Water-stage 

recorder on Morony Reservoir was used for determining head on taintor gates with altitude of gage at sea level (levels by Montana Power Company).

REMARKS.--Flow regulated by 18 smaller irrigation reservoirs and powerplants upstream, Clark Canyon Reservoir (station number 06015300), and Canyon Ferry 

Lake (station number 06058500). Diversion for irrigation of about 750,400 acres upstream from station. U.S. Geological Survey satellite telemeter at station. 

Magnitude and probability of annual low flow

based on 45 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 3,200 2,540 2,230 1,990 1,750 --

3 3,820 3,150 2,820 2,560 2,290 --

7 4,360 3,610 3,250 2,960 2,660 --

14 4,600 3,870 3,530 3,270 2,990 --

30 4,810 4,050 3,700 3,440 3,180 --

60 5,050 4,230 3,860 3,570 3,280 --

90 5,270 4,400 4,010 3,720 3,420 --

120 5,440 4,550 4,160 3,860 3,560 --

183 5,790 4,830 4,380 4,040 3,670 --

Magnitude and probability of seasonal low flow from

March-June based on 46 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 4,710 3,310 2,710 2,280 1,850 --

3 5,110 3,880 3,330 2,940 2,540 --

7 5,470 4,280 3,770 3,390 3,010 --

14 5,790 4,540 3,990 3,590 3,190 --

30 6,150 4,820 4,240 3,800 3,370 --

Magnitude and probability of seasonal low flow from

November-February based on 46 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 3,530 2,860 2,520 2,260 1,980 --

3 4,170 3,480 3,120 2,820 2,500 --

7 4,890 4,130 3,730 3,410 3,050 --

14 5,220 4,450 4,060 3,750 3,410 --

30 5,500 4,670 4,270 3,950 3,600 --

Duration of daily mean flows based on 46 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

3,140 3,270 3,630 4,240 4,800 5,320 5,850 6,490

40% 30% 20% 15% 10% 5% 2% 1%

7,240 7,990 8,850 10,500 12,200 16,800 23,100 26,100

Magnitude and probability of annual high flow

based on 46 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 18,500 28,600 35,800 45,400 52,800 --

3 18,100 27,500 33,700 41,300 46,900 --

7 17,300 25,800 31,100 37,400 41,800 --

15 16,000 23,900 28,800 34,700 38,800 --

30 14,600 21,500 25,900 31,200 35,000 --

60 12,700 17,900 21,100 24,900 27,500 --

90 11,200 15,500 18,100 21,200 23,300 --

Magnitude and probability of seasonal low flow from

July-October based on 45 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 4,090 3,100 2,660 2,320 1,990 --

3 4,410 3,550 3,180 2,900 2,630 --

7 4,700 3,830 3,450 3,160 2,870 --

14 4,860 4,010 3,630 3,350 3,070 --

30 5,040 4,150 3,760 3,470 3,180 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 11,900 3,830 5,840 1,570 46

November 10,400 3,950 6,190 1,610 46

December 11,500 3,770 6,170 1,350 46

January 8,230 3,870 6,330 1,100 46

February 9,250 4,030 6,530 1,280 46

March 10,800 4,020 6,830 1,760 46

April 13,200 3,530 7,500 2,410 46

May 24,800 4,450 11,000 4,530 47

June 30,200 3,760 14,100 7,270 47

July 23,600 3,820 8,660 4,130 47

August 9,950 3,720 5,960 1,520 46

September 9,990 3,110 5,590 1,510 46

Annual 11,500 4,350 7,540 1,800 46
88 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06090500 Belt Creek near Monarch, Mont.

Site Number 71

LOCATION.--Lat 47°12'27", long 110°55'53" (NAD 27), in NW1⁄4SE1⁄4NW1⁄4 sec.26, T.17 N., R.6 E., Cascade County, Hydrologic Unit 10030105, on left bank 

0.4 mi south of Riceville, 8.9 mi northwest of Monarch, and at river mile 52.0. 

DRAINAGE AREA.--368 mi2. 

PERIOD OF RECORD.--April 1951 to September 30, 1982 (discontinued). 

GAGE.--Water-stage recorder. Altitude of gage is 3,962.25 ft (NGVD 29, levels by U.S. Army Corps of Engineers). 

REMARKS.--No known regulation or diversion upstream from station. 

Magnitude and probability of annual low flow

based on 30 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 14 5.6 3.1 1.8 0.90 --

3 14 7.0 4.4 3.0 1.8 --

7 16 8.3 5.4 3.6 2.2 --

14 19 9.7 6.3 4.2 2.6 --

30 23 13 9.2 6.6 4.4 --

60 27 17 13 10 7.4 --

90 29 20 16 13 10 --

120 33 23 19 16 13 --

183 42 29 25 22 19 --

Magnitude and probability of seasonal low flow from

March-June based on 31 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 20 11 7.9 5.7 3.9 --

3 22 12 8.5 6.2 4.3 --

7 24 14 9.7 7.1 4.9 --

14 26 15 11 8.4 6.0 --

30 32 20 15 12 8.9 --

Magnitude and probability of seasonal low flow from

November-February based on 31 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 15 6.2 3.4 1.9 0.92 --

3 16 7.7 4.9 3.2 1.9 --

7 19 9.7 6.4 4.3 2.7 --

14 22 12 7.5 5.1 3.0 --

30 25 15 10 7.4 5.0 --

Duration of daily mean flows based on 31 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

6.6 11 17 22 30 39 47 60

40% 30% 20% 15% 10% 5% 2% 1%

79 119 228 347 528 891 1,460 1,960

Magnitude and probability of annual high flow

based on 31 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 1,500 2,780 4,010 6,160 8,290 --

3 1,410 2,470 3,420 4,950 6,380 --

7 1,270 2,090 2,760 3,770 4,650 --

15 1,110 1,750 2,240 2,950 3,530 --

30 935 1,470 1,870 2,410 2,840 --

60 706 1,090 1,350 1,690 1,950 --

90 549 832 1,020 1,250 1,420 --

Magnitude and probability of seasonal low flow from

July-October based on 32 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 47 32 26 22 18 --

3 48 33 27 23 19 --

7 50 35 29 25 20 --

14 51 36 30 26 22 --

30 54 38 32 28 24 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 264 29 68 46 32

November 120 21 50 22 31

December 73 8.8 35 16 31

January 53 4.7 29 12 31

February 55 9.4 31 13 31

March 106 6.7 36 20 31

April 385 30 127 87 31

May 1,570 226 697 348 32

June 2,210 189 819 539 32

July 576 50 226 127 32

August 174 24 91 39 32

September 221 28 74 43 32

Annual 344 62 192 83 31
Statistical Summaries of Streamflow 89

06090800 Missouri River at Fort Benton, Mont.

Site Number 72

LOCATION.--Lat 47°49'03", long 110°39'59" (NAD 27), in NW1⁄4SE1⁄4SE1⁄4 sec.23, T.24 N., R.8 E., Chouteau County, Hydrologic Unit 10030102, on left bank 

at downstream side of Old Fort Benton Bridge at Fort Benton, 3.8 mi upstream from Shonkin Creek, and at river mile 2,073.2.

DRAINAGE AREA.--24,749 mi2.

PERIOD OF RECORD.--October 1890 to current year (2002). Records for June 1881 to September 1890, published in WSP 546 and 761, have been found to be 

unreliable and were not used in analysis.

REVISED RECORDS.--WSP 746: 1932. WSP 1146: 1891-1907, 1908(M), 1909-18, 1937-38. WSP 1209: 1948(P). WSP 1309: 1929(M). WSP 1629: 

Drainage area. Also see PERIOD OF RECORD.

GAGE.--Water-stage recorder. Altitude of gage is 2,614.05 ft (NGVD 1929). Prior to Oct. 11, 1920, nonrecording gages, and Oct. 11, 1920, to Apr. 25, 1924, 

water-stage recorder, all at present site at datum 1.00 ft higher.

REMARKS.--Flow regulated by 18 smaller irrigation reservoirs and powerplants, Clark Canyon Reservoir (station number 06015300), and Canyon Ferry Lake 

(station number 06058500). Diversions for irrigation of about 751,000 acres upstream from station. Extreme diurnal fluctuation caused by powerplant at 

Morony Dam. Bureau of Reclamation satellite telemeter at station. 

Unregulated streamflow period

Magnitude and probability of annual low flow

based on 52 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 2,660 1,880 1,460 1,140 829 653

3 2,960 2,270 1,900 1,600 1,290 1,100

7 3,170 2,440 2,060 1,760 1,450 1,260

14 3,350 2,570 2,180 1,860 1,530 1,330

30 3,460 2,710 2,340 2,040 1,740 1,540

60 3,720 2,960 2,570 2,260 1,940 1,740

90 3,980 3,200 2,800 2,480 2,150 1,940

120 4,220 3,390 2,970 2,640 2,290 2,070

183 4,380 3,540 3,130 2,810 2,460 2,240

Magnitude and probability of seasonal low flow from

March-June based on 53 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 4,070 3,070 2,610 2,270 1,910 1,700

3 4,290 3,420 3,020 2,720 2,410 2,220

7 4,490 3,620 3,220 2,930 2,620 2,440

14 4,780 3,910 3,540 3,280 3,010 2,840

30 5,580 4,490 4,030 3,690 3,350 3,150

Magnitude and probability of seasonal low flow from

November-February based on 52 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 2,910 2,140 1,710 1,370 1,030 826

3 3,260 2,540 2,110 1,750 1,380 1,150

7 3,560 2,830 2,410 2,060 1,690 1,450

14 3,800 3,020 2,570 2,200 1,790 1,540

30 3,950 3,210 2,800 2,460 2,090 1,860

Duration of daily mean flows based on 53 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

2,040 2,280 2,620 3,130 3,660 4,190 4,730 5,280

40% 30% 20% 15% 10% 5% 2% 1%

5,820 7,020 9,170 11,500 15,600 22,700 31,300 35,400

Magnitude and probability of annual high flow

based on 53 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 26,200 39,000 47,600 58,600 66,700 74,900

3 25,800 38,200 46,300 56,300 63,500 70,500

7 25,400 37,000 43,900 51,800 57,000 61,800

15 24,000 34,700 40,700 47,300 51,600 55,400

30 21,400 31,200 36,900 43,200 47,400 51,100

60 17,700 25,000 29,200 33,700 36,600 39,200

90 14,800 20,600 23,800 27,500 29,900 32,000

Magnitude and probability of seasonal low flow from

July-October based on 52 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 3,050 2,110 1,660 1,330 1,000 818

3 3,200 2,420 2,070 1,810 1,540 1,380

7 3,400 2,600 2,230 1,950 1,670 1,500

14 3,510 2,690 2,320 2,040 1,760 1,580

30 3,650 2,810 2,430 2,150 1,860 1,690

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 8,320 2,440 4,910 1,410 53

November 7,670 2,790 5,040 1,230 53

December 6,320 2,450 4,490 889 53

January 5,840 2,380 4,180 789 53

February 6,670 2,490 4,520 986 53

March 11,800 2,990 6,000 1,690 53

April 15,500 4,130 8,590 2,870 53

May 27,600 4,140 14,800 5,790 53

June 53,600 4,590 20,000 10,700 53

July 26,600 2,430 8,340 4,970 53

August 8,050 1,580 4,240 1,450 53

September 7,180 1,890 4,220 1,200 53

Annual 11,500 3,620 7,440 2,100 53
90 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06090800 Missouri River at Fort Benton, Mont.—Continued

Site Number 72

Regulated streamflow period

Magnitude and probability of annual low flow

based on 49 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 3,290 2,550 2,210 1,960 1,690 --

3 3,840 3,140 2,810 2,550 2,280 --

7 4,330 3,560 3,180 2,890 2,580 --

14 4,560 3,770 3,390 3,100 2,790 --

30 4,760 3,940 3,560 3,280 2,990 --

60 4,990 4,120 3,740 3,450 3,150 --

90 5,200 4,280 3,880 3,580 3,270 --

120 5,360 4,450 4,050 3,760 3,460 --

183 5,690 4,710 4,270 3,940 3,600 --

Magnitude and probability of seasonal low flow from

March-June based on 50 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 4,700 3,480 2,950 2,560 2,180 1,950

3 5,120 3,940 3,430 3,050 2,670 2,440

7 5,440 4,310 3,820 3,460 3,100 2,880

14 5,730 4,550 4,030 3,660 3,270 3,040

30 6,080 4,820 4,280 3,890 3,490 3,250

Magnitude and probability of seasonal low flow from

November-February based on 49 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 3,670 2,960 2,630 2,380 2,120 --

3 4,210 3,520 3,180 2,920 2,640 --

7 4,840 4,080 3,700 3,410 3,090 --

14 5,190 4,380 3,990 3,690 3,360 --

30 5,460 4,600 4,190 3,860 3,520 --

Duration of daily mean flows based on 50 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

3,140 3,250 3,570 4,110 4,730 5,250 5,770 6,390

40% 30% 20% 15% 10% 5% 2% 1%

7,170 7,940 8,810 10,500 12,600 17,800 23,800 28,400

Magnitude and probability of annual high flow

based on 50 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 19,900 32,000 41,100 53,800 64,100 75,000

3 19,400 30,800 39,000 49,900 58,400 67,100

7 18,500 28,700 35,400 44,000 50,200 56,300

15 17,000 25,900 31,800 38,900 44,100 49,100

30 15,400 23,100 28,100 34,300 38,600 42,800

60 13,200 19,000 22,700 27,000 30,100 33,000

90 11,600 16,200 19,100 22,600 25,100 27,500

Magnitude and probability of seasonal low flow from

July-October based on 49 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 4,030 2,980 2,510 2,160 1,800 --

3 4,370 3,430 3,020 2,710 2,400 --

7 4,620 3,700 3,280 2,980 2,670 --

14 4,760 3,850 3,440 3,150 2,840 --

30 4,930 3,990 3,590 3,290 2,990 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 12,600 3,580 5,780 1,700 50

November 10,800 3,670 6,090 1,640 50

December 11,600 3,690 6,130 1,420 50

January 8,380 3,790 6,320 1,190 50

February 9,330 4,030 6,550 1,380 50

March 11,000 3,930 6,770 1,830 50

April 13,800 3,570 7,480 2,440 50

May 25,400 4,540 11,500 4,780 50

June 31,400 4,060 14,800 7,880 50

July 23,200 3,680 8,750 4,340 50

August 10,600 3,470 5,820 1,540 50

September 10,200 3,130 5,520 1,590 50

Annual 11,800 4,460 7,620 1,920 50
Statistical Summaries of Streamflow 91

06091700 Two Medicine River below South Fork, near Browning, Mont.

Site Number 73

LOCATION.--Lat 48°25'36", long 112°59'20" (NAD 27), in SE1⁄4SE1⁄4SE1⁄4 sec.23, T.31 N., R.11 W., Glacier County, Hydrologic Unit 10030201, Blackfeet Indian 

Reservation, on left bank 15 ft downstream from bridge on Blackfeet Secondary Highway No. 1, 9.7 mi south of Browning, and 12.3 mi northwest of Heart 

Butte.

DRAINAGE AREA.--250 mi2.

PERIOD OF RECORD.--May 1977 to current year (2002).

GAGE.--Water-stage recorder. Altitude of gage is 4,180 ft (NGVD 29). May 1977 to September 1997 at datum 1.00 ft higher.

REMARKS.--Flow regulated by Lower Two Medicine Lake (station number 06090900). Diversions for irrigation of about 64 acres upstream from station. Bureau 

of Reclamation satellite telemeter at station.

Magnitude and probability of annual low flow

based on 24 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 22 14 12 9.8 -- --

3 23 16 13 11 -- --

7 26 18 15 13 -- --

14 29 20 17 15 -- --

30 35 24 20 17 -- --

60 44 29 23 19 -- --

90 49 32 26 22 -- --

120 56 34 26 22 -- --

183 71 44 36 31 -- --

Magnitude and probability of seasonal low flow from

March-June based on 25 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 54 34 28 24 21 --

3 58 37 31 26 23 --

7 69 43 34 29 24 --

14 78 49 39 33 27 --

30 115 69 53 42 33 --

Magnitude and probability of seasonal low flow from

November-February based on 25 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 25 15 12 9.9 7.6 --

3 26 16 13 11 8.6 --

7 30 19 15 13 11 --

14 35 22 18 15 13 --

30 41 27 22 18 15 --

Duration of daily mean flows based on 25 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

17 20 26 33 46 63 91 128

40% 30% 20% 15% 10% 5% 2% 1%

191 282 516 712 984 1,420 2,030 2,440

Magnitude and probability of annual high flow

based on 25 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 2,400 3,730 4,920 6,850 8,660 --

3 2,190 3,170 3,930 5,030 5,960 --

7 1,900 2,650 3,190 3,910 4,480 --

15 1,610 2,190 2,590 3,120 3,540 --

30 1,380 1,870 2,210 2,670 3,030 --

60 1,150 1,520 1,760 2,080 2,310 --

90 936 1,210 1,390 1,620 1,790 --

Magnitude and probability of seasonal low flow from

July-October based on 25 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 35 23 19 17 15 --

3 36 24 20 17 15 --

7 39 26 21 18 15 --

14 44 28 22 19 16 --

30 52 33 26 21 17 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 533 25 97 104 25

November 558 19 131 162 25

December 394 20 80 79 25

January 180 18 62 38 25

February 394 26 92 88 25

March 474 40 144 97 25

April 923 140 494 194 25

May 2,040 439 1,180 376 26

June 2,920 282 1,070 588 26

July 656 173 366 131 26

August 264 41 161 50 26

September 240 24 104 54 26

Annual 542 199 338 97 25
92 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06092000 Two Medicine River near Browning, Mont.

Site Number 74

LOCATION.--Lat 48°28'25", long 112°48'06" (NAD 27), in NW1⁄4 SW1⁄4 SE1⁄4 sec.5, T.31 N., R.9 W., Glacier County, Hydrologic Unit 10030201, on right bank 

1,000 ft upstream from bridge on U.S. Highway 89, 11 mi southeast of Browning, and 15 mi upstream from Badger Creek.

DRAINAGE AREA.--317 mi2.

PERIOD OF RECORD.--43 years. April 1907 to October 1924, May 1951 to September 1977 (discontinued). Monthly discharge only for some periods, published 

in WSP 1309. Published as "Two Medicine River at Family," 1907-24. October 1957 to September 1964, published as "Two Medicine Creek near Browning."

REVISED RECORDS.--WSP 1309: 1908, 1910, 1913, 1916, 1918. WSP 1559: 1915(M), 1917-18(M), 1921-24. WSP 1729: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 3,930 ft (NGVD 29, from topographic map). Prior to Nov. 1, 1924, nonrecording gage at several sites within 

3 mi of present site at various datums. May 1, 1951, to Sept. 30, 1964, and Oct. 1, 1964, to Sept. 27, 1967, water-stage recorder at site 150 ft downstream at 

datums 2.00 ft higher and present datum, respectively.

REMARKS.--Flow partly regulated by Lower Two Medicine Lake. Diversions upstream from station into Two Medicine Canal for irrigation of about 10,000 acres 

downstream from station. 

Magnitude and probability of annual low flow

based on 41 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 14 5.1 2.9 1.8 1.0 --

3 15 5.5 3.1 1.9 1.1 --

7 18 6.7 3.9 2.4 1.3 --

14 23 9.4 5.4 3.3 1.8 --

30 35 15 9.0 5.5 2.9 --

60 46 23 14 8.9 4.9 --

90 60 33 21 14 8.0 --

120 72 42 28 19 12 --

183 81 51 40 33 26 --

Magnitude and probability of seasonal low flow from

March-June based on 43 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 59 35 27 22 17 --

3 60 38 29 24 19 --

7 64 41 33 28 23 --

14 69 45 38 34 30 --

30 97 60 48 41 34 --

Magnitude and probability of seasonal low flow from

November-February based on 43 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 35 17 11 7.5 4.5 --

3 39 20 13 8.7 5.2 --

7 41 24 18 14 10 --

14 46 30 25 21 17 --

30 52 36 30 25 21 --

Duration of daily mean flows based on 43 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

4.6 8.8 22 35 52 69 87 117

40% 30% 20% 15% 10% 5% 2% 1%

167 270 557 838 1,210 1,780 2,530 3,100

Magnitude and probability of annual high flow

based on 43 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 2,610 5,010 7,890 14,000 21,400 --

3 2,430 4,350 6,360 10,100 14,100 --

7 2,250 3,640 4,780 6,470 7,940 --

15 2,010 3,030 3,740 4,670 5,380 --

30 1,800 2,590 3,040 3,540 3,860 --

60 1,510 1,990 2,190 2,360 2,440 --

90 1,230 1,550 1,650 1,720 1,750 --

Magnitude and probability of seasonal low flow from

July-October based on 44 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 20 6.2 3.2 2.0 1.2 --

3 22 6.6 3.4 2.1 1.3 --

7 25 7.8 4.1 2.5 1.5 --

14 31 11 5.7 3.4 2.1 --

30 45 17 9.4 5.5 3.2 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 474 2.4 131 100 44

November 332 24 114 70 43

December 378 21 91 64 43

January 440 30 85 67 43

February 280 34 90 51 43

March 592 27 134 113 43

April 940 109 481 230 44

May 2,240 286 1,400 415 45

June 4,820 91 1,500 924 45

July 1,130 20 382 266 45

August 283 5.4 92 73 45

September 596 3.4 102 106 45

Annual 624 71 377 113 43
Statistical Summaries of Streamflow 93

06092500 Badger Creek near Browning, Mont.

Site Number 75

LOCATION.--Lat 48°21'03", long 112°50'27" (NAD 27), in NE1⁄4 sec.24, T.30 N., R.10 W., Glacier County, on right bank just upstream from point of diversion 

to Four Horns Canal, 15 mi upstream from mouth, and 17 mi southeast of Browning.

DRAINAGE AREA.--133 mi2 . 

PERIOD OF RECORD.--May 1951 to September 1973. Some monthly discharges in 1980.

REVISED RECORDS.--WSP 1729: 1951(M)

GAGE.--Water-stage recorder and control consisting of concrete diversion dam and two taintor gates (regularly closed). Altitude of gage is 4,179.20 ft (NGVD 29, 

Bureau of Reclamation bench mark).

REMARKS.--Water diverted into Four Horns Canal at station for irrigation of about 6,000 acres downstream from station.

Magnitude and probability of annual low flow

based on 21 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 47 37 32 29 -- --

3 50 39 34 30 -- --

7 54 42 36 32 -- --

14 60 48 42 37 -- --

30 72 58 51 46 -- --

60 79 68 63 59 -- --

90 87 76 70 66 -- --

120 94 82 76 72 -- --

183 104 92 87 83 -- --

Magnitude and probability of seasonal low flow from

March-June based on 22 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 66 51 43 37 -- --

3 68 52 45 39 -- --

7 73 57 49 43 -- --

14 78 63 56 50 -- --

30 88 74 68 65 -- --

Magnitude and probability of seasonal low flow from

November-February based on 22 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 51 39 34 30 -- --

3 54 41 35 31 -- --

7 58 44 38 33 -- --

14 64 49 43 38 -- --

30 74 59 52 46 -- --

Duration of daily mean flows based on 22 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

42 49 65 73 89 102 115 127

40% 30% 20% 15% 10% 5% 2% 1%

155 187 285 406 590 854 1,160 1,390

Magnitude and probability of annual high flow

based on 22 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 1,230 2,240 3,600 6,840 -- --

3 1,170 1,920 2,730 4,270 -- --

7 1,060 1,570 2,030 2,790 -- --

15 980 1,380 1,680 2,130 -- --

30 864 1,160 1,370 1,660 -- --

60 687 882 1,010 1,180 -- --

90 553 696 786 896 -- --

Magnitude and probability of seasonal low flow from

July-October based on 22 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 103 88 81 76 -- --

3 104 89 83 78 -- --

7 107 92 85 80 -- --

14 110 94 87 82 -- --

30 115 101 96 93 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 206 91 132 32 22

November 156 79 112 21 22

December 139 57 95 22 22

January 125 55 83 18 22

February 184 63 92 23 22

March 176 58 96 26 22

April 302 78 179 71 22

May 915 466 651 129 22

June 1,740 318 753 344 23

July 653 139 287 112 23

August 244 94 158 33 23

September 194 101 128 24 23

Annual 298 159 229 38 22
94 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06093200 Badger Creek below Four Horns Canal, near Browning, Mont.

Site Number 76

LOCATION.--Lat 48°22'12", long 112°48'07" (NAD 27), in NW1⁄4SW1⁄4SE1⁄4 sec.8, T.30 N., R.9 W., Glacier County, Hydrologic Unit 10030201, Blackfeet Indian 

Reservation, on left bank, 3.4 mi downstream from point of diversion to Four Horns Canal, 15.5 mi southeast of Browning, and at river mile 11.6.

DRAINAGE AREA.--152 mi2.

PERIOD OF RECORD.--October 1973 to current year (2002). Records equivalent to those published as "Badger Creek near Browning" (station number 06092500) 

if diversion to Four Horns Canal is added to flow at station.

GAGE.--Water-stage recorder. Altitude of gage is 4,140 ft (NGVD 29). May 1951 to September 1973, water-stage recorder at site 3.4 mi upstream (station number 

06092500) at different datum.

REMARKS.--Four Horns Canal diverts water from right bank in NE1⁄4 sec.24, T.30 N., R.10 W., at diversion dam 3.4 mi upstream for irrigation of about 

6,000 acres downstream from station. Bureau of Reclamation satellite telemeter at station.

Magnitude and probability of annual low flow

based on 28 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 31 17 12 8.4 5.6 --

3 33 18 12 9.0 6.0 --

7 34 19 13 9.4 6.3 --

14 37 20 14 10 7.0 --

30 41 23 16 12 8.0 --

60 48 28 21 16 12 --

90 59 37 28 23 17 --

120 71 45 34 26 19 --

183 78 55 46 39 33 --

Magnitude and probability of seasonal low flow from

March-June based on 29 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 69 49 37 29 20 --

3 74 53 41 31 22 --

7 80 57 44 34 24 --

14 86 62 49 39 29 --

30 88 67 58 52 45 --

Magnitude and probability of seasonal low flow from

November-February based on 28 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 53 36 28 22 17 --

3 57 41 33 27 22 --

7 62 44 36 30 24 --

14 68 51 43 37 32 --

30 75 60 53 47 42 --

Duration of daily mean flows based on 29 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

14 18 28 42 62 75 86 99

40% 30% 20% 15% 10% 5% 2% 1%

117 145 213 279 409 677 1,030 1,290

Magnitude and probability of annual high flow

based on 29 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 1,120 2,130 3,240 5,410 7,840 --

3 1,030 1,850 2,650 4,040 5,440 --

7 933 1,550 2,040 2,740 3,320 --

15 814 1,280 1,600 2,000 2,290 --

30 681 1,040 1,280 1,560 1,760 --

60 536 794 948 1,120 1,230 --

90 429 621 729 847 922 --

Magnitude and probability of seasonal low flow from

July-October based on 28 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 33 17 12 8.7 5.6 --

3 34 18 13 9.2 6.3 --

7 36 19 13 9.7 6.5 --

14 38 21 14 11 7.3 --

30 42 23 16 12 8.2 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 316 9.1 83 58 29

November 295 41 112 53 29

December 184 43 97 31 29

January 160 57 89 25 29

February 198 52 90 31 29

March 206 45 94 30 29

April 321 62 172 69 29

May 899 140 503 174 29

June 2,240 59 586 451 29

July 568 18 170 122 29

August 184 16 76 45 29

September 199 16 69 44 29

Annual 350 68 179 60 29
Statistical Summaries of Streamflow 95

06093500 Badger Creek near Family, Mont.

Site Number 77

LOCATION.--Lat 48°26'10", long 112°42'00" (NAD 27), in NE1⁄4 sec.19, T.31 N., R.8 W., Glacier County, at highway bridge, 4 mi southeast of Family.

DRAINAGE AREA.--239 mi2.

PERIOD OF RECORD.--17 years (1907-24).

GAGE.--Chain gage. Altitude of gage is 3,900 ft (NGVD 29, from topographic map). Prior to June 4, 1908, staff gages 700 ft downstream and July 21, 1908, to 

May 24, 1909, chain gage 300 ft downstream from described site at unknown datums.

REMARKS.--Bureau of Reclamation canal began to divert water in 1915 for irrigation upstream from station.

Magnitude and probability of annual low flow

based on 16 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 48 17 7.9 3.7 -- --

3 49 19 9.3 4.6 -- --

7 51 25 15 8.9 -- --

14 53 30 20 13 -- --

30 59 37 27 19 -- --

60 69 48 38 31 -- --

90 77 59 51 45 -- --

120 93 72 63 55 -- --

183 109 84 73 65 -- --

Magnitude and probability of seasonal low flow from

March-June based on 17 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 72 44 33 26 -- --

3 73 45 35 29 -- --

7 73 48 39 33 -- --

14 73 51 43 38 -- --

30 76 54 46 41 -- --

Magnitude and probability of seasonal low flow from

November-February based on 17 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 67 50 40 33 -- --

3 67 50 40 33 -- --

7 67 50 40 33 -- --

14 67 50 40 33 -- --

30 68 51 41 34 -- --

Duration of daily mean flows based on 17 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

25 34 49 61 77 91 113 138

40% 30% 20% 15% 10% 5% 2% 1%

173 225 333 450 618 895 1,290 1,460

Magnitude and probability of annual high flow

based on 17 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 1,250 1,710 1,980 2,280 -- --

3 1,160 1,560 1,790 2,040 -- --

7 1,060 1,430 1,660 1,920 -- --

15 932 1,300 1,540 1,850 -- --

30 826 1,180 1,420 1,750 -- --

60 685 916 1,060 1,240 -- --

90 558 738 852 991 -- --

Magnitude and probability of seasonal low flow from

July-October based on 18 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 110 34 13 5.2 -- --

3 111 37 15 6.3 -- --

7 113 46 23 12 -- --

14 118 55 31 17 -- --

30 132 73 46 29 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 356 66 153 69 18

November 231 80 140 44 18

December 130 65 95 21 18

January 190 30 77 33 17

February 160 25 73 29 17

March 242 35 89 49 17

April 378 70 225 90 17

May 1,100 319 645 182 18

June 2,000 179 765 439 18

July 696 32 291 183 18

August 380 25 159 85 18

September 493 58 161 97 18

Annual 354 120 237 68 17
96 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06098000 Dupuyer Creek near Valier, Mont.

Site Number 78

LOCATION.--Lat 48°14'10", long 112°23'50" (NAD 27), in NW1⁄4 sec.33, T.29 N., R.6 W., Pondera County, 6 mi downstream from Sheep Creek and 8 mi 

(revised) southwest of Valier.

DRAINAGE AREA.--137 mi2.

PERIOD OF RECORD.--25 years (1912-37).

GAGE.--Water-stage recorder. Altitude of gage is 3,920 ft (NGVD 29, from topographic map). Prior to Apr. 20, 1925, staff or chain gage at same site and datum.

REMARKS.--Several small diversions for irrigation upstream from station.

Magnitude and probability of annual low flow

based on 24 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 4.2 0.86 0.00 0.00 -- --

3 4.5 .91 .00 .00 -- --

7 5.5 1.4 .00 .00 -- --

14 6.5 2.2 .00 .00 -- --

30 9.9 2.3 .46 .03 -- --

60 12 3.2 .98 .09 -- --

90 15 4.2 1.3 .12 -- --

120 18 5.2 1.6 .17 -- --

183 19 6.5 3.1 1.5 -- --

Magnitude and probability of seasonal low flow from

March-June based on 25 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 14 3.4 0.67 0.00 0.00 --

3 14 3.6 .70 .00 .00 --

7 16 3.8 .93 .09 .00 --

14 17 5.3 2.3 1.0 .35 --

30 28 11 5.6 3.1 1.4 --

Magnitude and probability of seasonal low flow from

November-February based on 25 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 9.6 4.9 3.3 2.0 0.00 --

3 9.9 5.1 3.4 2.0 .00 --

7 10 5.3 3.5 2.1 .00 --

14 11 5.8 4.0 2.1 .00 --

30 15 6.6 4.6 2.1 .85 --

Duration of daily mean flows based on 25 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

0.26 0.51 2.3 5.6 9.8 14 19 26

40% 30% 20% 15% 10% 5% 2% 1%

34 46 65 82 107 164 266 375

Magnitude and probability of annual high flow

based on 25 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 288 738 1,200 2,020 2,830 --

3 244 599 956 1,570 2,170 --

7 205 470 718 1,120 1,490 --

15 172 384 576 878 1,150 --

30 138 293 429 639 823 --

60 109 219 310 443 553 --

90 93 181 252 353 434 --

Magnitude and probability of seasonal low flow from

July-October based on 25 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 6.3 1.1 0.00 0.00 0.00 --

3 6.8 1.2 .00 .00 .00 --

7 8.1 1.7 .00 .00 .00 --

14 9.2 2.3 .00 .00 .00 --

30 13 2.5 .49 .04 .00 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 78 0.00 28 22 25

November 61 .43 27 16 25

December 52 5.3 20 13 25

January 62 5.3 22 16 25

February 90 4.2 26 20 25

March 127 14 37 26 25

April 147 11 67 39 25

May 436 4.0 115 99 25

June 707 1.4 152 178 25

July 265 .00 50 59 26

August 125 .00 27 30 26

September 91 .00 22 22 26

Annual 150 8.4 49 36 25
Statistical Summaries of Streamflow 97

06098500 Cut Bank Creek near Browning, Mont.

Site Number 79

LOCATION.--Lat 48°37'00", long 113°02'06" (NAD 27), in NE1⁄4NW1⁄4SW1⁄4 sec.15, T.33 N., R.11 W., Glacier County, Hydrologic Unit 10030202, Blackfeet 

Indian Reservation, on right bank 20 ft downstream from bridge on Montana Secondary Highway 464, 4.0 mi north of Browning, and at river mile 73.3.

DRAINAGE AREA.--123 mi2.

PERIOD OF RECORD.--April 1918 to October 1925 (seasonal records only), April 1991 to current year (2002).

REVISED RECORDS.--WDR MT-93-1: 1992(M).

GAGE.--Water-stage recorder. Altitude of gage is 4,380 ft (NGVD 29). April 1918 to October 1925, water-stage recorder at site about 120 ft upstream at different 

datum. April 1991 to September 1995 at datum 1.00 ft higher.

REMARKS.--Diversions for irrigation of about 1,200 acres upstream from station. Bureau of Reclamation satellite telemeter at station.

Magnitude and probability of annual low flow

based on 10 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 16 12 10 9.0 -- --

3 17 13 11 9.5 -- --

7 19 14 12 10 -- --

14 20 15 12 11 -- --

30 23 16 14 12 -- --

60 25 17 14 13 -- --

90 27 18 16 14 -- --

120 31 21 18 17 -- --

183 37 25 21 19 -- --

Magnitude and probability of seasonal low flow from

March-June based on 13 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 26 18 14 12 -- --

3 27 19 15 13 -- --

7 29 21 17 14 -- --

14 32 22 19 17 -- --

30 43 27 21 17 -- --

Magnitude and probability of seasonal low flow from

November-February based on 11 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 17 13 11 9.4 -- --

3 19 14 12 10 -- --

7 20 15 14 13 -- --

14 22 16 15 14 -- --

30 24 18 17 16 -- --

Duration of daily mean flows based on 11 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

12 14 18 23 30 39 50 67

40% 30% 20% 15% 10% 5% 2% 1%

98 157 255 335 448 634 826 1,010

Magnitude and probability of annual high flow

based on 11 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 864 1,420 1,970 -- -- --

3 801 1,220 1,560 -- -- --

7 711 1,000 1,200 -- -- --

15 619 869 1,030 -- -- --

30 542 753 887 -- -- --

60 438 595 694 -- -- --

90 355 469 539 -- -- --

Magnitude and probability of seasonal low flow from

July-October based on 16 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 27 17 14 11 -- --

3 28 18 14 11 -- --

7 29 19 15 12 -- --

14 32 21 16 13 -- --

30 36 24 18 15 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 136 15 55 31 16

November 216 25 63 58 12

December 157 17 42 39 11

January 74 18 32 16 11

February 139 15 40 36 11

March 110 18 53 31 13

April 217 57 134 45 18

May 740 248 421 110 19

June 955 184 512 215 19

July 344 58 190 78 19

August 140 16 68 32 18

September 82 12 43 19 18

Annual 201 69 133 41 11
98 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06099000 Cut Bank Creek at Cut Bank, Mont.

Site Number 80

LOCATION.--Lat 48°38'00", long 112°20'46" (NAD 27), in SW1⁄4SE1⁄4NE1⁄4 sec.11, T.33 N., R.6 W., Glacier County, Hydrologic Unit 10030202, Blackfeet Indian 

Reservation, on right bank, 0.1 mi downstream from bridge on U.S. Highway 2, 0.7 mi west of Cut Bank, 0.8 mi downstream from Old Maids Coulee, and at 

river mile 17.7.

DRAINAGE AREA.--1,041 mi2.

PERIOD OF RECORD.--August 1905 to October 1919, May to July 1920, May 1922 to October 1924, May 1951 to September 1973, October 1981 to current 

year (2002). Monthly discharge only for some periods, published in WSP 1309.

REVISED RECORDS.--WSP 1309; 1907-8, 1910-11, 1924-25. WSP 1509: 1911, 1916(M). WSP 1559: 1905(M), 1908(M). WSP 1709: 1959. WSP 1729: 

Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 3,561.42 ft (NGVD 29). Prior to May 12, 1922, nonrecording gage at several sites 0.5 mi upstream at various 

datums. May 12, 1922, to Nov. 1, 1924, nonrecording gage at present site and different datum.

REMARKS.--Few minor diversions for irrigation upstream from station. Natural flow of stream may be affected by return flow from Two Medicine Canal which 

irrigates lands upstream from station. U.S. Geological Survey satellite telemeter at station.

Magnitude and probability of annual low flow

based on 55 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 13 6.8 4.5 3.1 2.0 1.5

3 14 7.5 5.1 3.7 2.4 1.8

7 16 8.8 6.1 4.4 3.0 2.2

14 19 10 7.3 5.3 3.6 2.8

30 23 13 9.7 7.3 5.2 4.1

60 29 18 13 10 7.8 6.3

90 35 22 17 14 11 9.1

120 43 29 24 20 17 15

183 56 38 31 26 21 19

Magnitude and probability of seasonal low flow from

March-June based on 59 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 42 21 14 10 6.6 4.9

3 44 22 15 11 7.0 5.3

7 48 26 18 13 9.0 7.0

14 59 31 22 16 11 8.7

30 95 47 31 21 13 9.8

Magnitude and probability of seasonal low flow from

November-February based on 59 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 17 8.6 5.5 3.7 2.2 1.6

3 19 9.5 6.1 4.1 2.5 1.9

7 22 11 7.3 4.8 3.0 2.3

14 24 13 8.6 5.7 3.7 3.0

30 29 16 10 7.5 5.3 4.3

Duration of daily mean flows based on 59 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

6.6 9.9 17 24 34 46 61 84

40% 30% 20% 15% 10% 5% 2% 1%

118 177 290 376 504 715 1,010 1,240

Magnitude and probability of annual high flow

based on 59 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 1,390 2,650 3,910 6,130 8,380 11,300

3 1,160 2,050 2,900 4,340 5,750 7,510

7 938 1,530 2,060 2,880 3,640 4,540

15 772 1,190 1,520 2,000 2,410 2,880

30 658 956 1,170 1,460 1,690 1,930

60 541 760 905 1,090 1,230 1,360

90 455 630 744 885 988 1,090

Magnitude and probability of seasonal low flow from

July-October based on 59 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 32 14 7.9 4.7 2.4 1.6

3 34 15 8.7 5.3 2.8 1.9

7 37 17 10 6.5 3.6 2.4

14 40 20 12 8.0 4.7 3.2

30 47 25 17 12 7.5 5.5

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 268 11 84 50 61

November 271 19 77 49 59

December 185 15 47 32 59

January 115 1.6 35 20 59

February 414 11 57 61 59

March 1,050 6.9 149 158 59

April 664 79 241 139 59

May 894 198 485 167 62

June 1,780 174 635 342 62

July 605 17 244 134 62

August 234 5.6 90 52 62

September 298 5.9 76 61 62

Annual 317 74 184 60 59
Statistical Summaries of Streamflow 99

06099500 Marias River near Shelby, Mont.

Site Number 81

LOCATION.--Lat 48°25'38", long 111°53'20" (NAD 27), in SE1⁄4NW1⁄4SE1⁄4 sec.20, T.31 N., R.2 W., Toole County, Hydrologic Unit 10030203, on left bank 20 ft 

downstream from bridge on old U.S. Highway 91, 5.1 mi south of Shelby, 24 mi downstream from Cut Bank Creek, and at river mile 140.6.

DRAINAGE AREA.--3,242 mi2, of which 518 mi2 is probably noncontributing.

PERIOD OF RECORD.--April 1902 to December 1904, May 1905 to December 1906, May 1907 to January 1908, April 1911 to current year (2002). Monthly 

discharge only for some periods, published in WSP 1309.

REVISED RECORDS.--WSP 1309: 1903-4, 1918, 1921, 1933, 1935, 1947. WSP 1509: 1902, 1912(M), 1916, 1943(M). WSP 1729: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 3,087.72 ft (NGVD 29). Prior to Dec. 23, 1947, nonrecording gage or water-stage recorder at several sites 

within 1,000 ft of present site at approximately the same datum. Dec. 23, 1947, to Apr. 6, 1976, water-stage recorder at site 150 ft downstream at same datum.

REMARKS.--Some regulation by Lower Two Medicine Lake (station number 06090900), Four Horns Reservoir (station number 06093000), Swift Reservoir 

(station number 06094000), and Lake Frances (station number 06095500), having a combined capacity of 172,630 acre-ft. Diversions for irrigation of about 

50,000 acres upstream from station and about 15,000 acres downstream from station. Bureau of Reclamation satellite telemeter at station. 

Magnitude and probability of annual low flow

based on 91 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 119 70 50 37 25 19

3 122 76 57 44 32 26

7 133 84 63 49 36 29

14 147 94 70 54 40 32

30 170 111 85 67 50 40

60 196 134 109 91 74 64

90 226 156 128 108 89 77

120 256 176 144 122 101 89

183 287 194 158 133 110 97

Magnitude and probability of seasonal low flow from

March-June based on 94 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 254 152 116 93 72 61

3 264 161 125 102 80 69

7 286 180 142 117 95 83

14 327 211 170 143 119 106

30 439 276 219 181 147 129

Magnitude and probability of seasonal low flow from

November-February based on 94 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 138 88 68 54 42 35

3 146 93 72 57 44 37

7 160 102 78 62 46 38

14 176 113 86 68 51 41

30 199 130 101 80 61 50

Duration of daily mean flows based on 94 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

73 92 126 159 214 262 329 414

40% 30% 20% 15% 10% 5% 2% 1%

543 776 1,350 1,810 2,450 3,630 5,300 6,320

Magnitude and probability of annual high flow

based on 94 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 4,860 9,280 14,300 24,200 35,500 51,600

3 4,660 8,340 12,000 18,400 24,900 33,200

7 4,270 7,110 9,490 13,100 16,400 20,100

15 3,820 6,000 7,600 9,780 11,500 13,300

30 3,330 5,090 6,300 7,860 9,030 10,200

60 2,750 4,070 4,920 5,950 6,670 7,380

90 2,270 3,300 3,940 4,700 5,230 5,730

Magnitude and probability of seasonal low flow from

July-October based on 97 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 183 96 65 45 29 22

3 184 102 73 54 38 30

7 193 110 80 61 44 35

14 207 120 88 68 50 41

30 230 137 104 83 64 53

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 1,450 74 405 248 97

November 1,480 116 394 246 97

December 1,140 103 304 174 97

January 700 42 255 130 94

February 1,170 59 318 206 94

March 2,300 139 579 411 94

April 3,150 280 1,140 563 96

May 5,300 711 2,720 1,040 98

June 10,200 409 3,090 2,070 98

July 3,980 147 1,060 764 98

August 1,100 67 389 233 98

September 1,850 66 358 272 98

Annual 1,930 302 906 351 94
100 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06101500 Marias River near Chester, Mont.

Site Number 82

LOCATION.--Lat 48°18'23", long 111°04'47" (NAD 27), in SW1⁄4SW1⁄4SW1⁄4 sec.34, T.30 N., R.5 E., Liberty County, Hydrologic Unit 10030203, on left bank 

2.0 mi downstream from Tiber Dam, 4.4 mi upstream from Pondera Coulee, 15 mi southwest of Chester, and at river mile 78.3.

DRAINAGE AREA.--4,927 mi2, of which 518 mi2 is probably noncontributing.

PERIOD OF RECORD.--April to September 1921, October 1945 to September 1947, October 1955 to current year (2002). Monthly discharge only for some 

periods, published in WSP 1309.

REVISED RECORDS.--WSP 1629: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 2,814.03 ft (NGVD, Bureau of Reclamation bench mark). Prior to Oct. 1, 1921, nonrecording gage at bridge 

2.5 mi downstream at different datum. Oct. 4, 1945, to Sept. 30, 1946, nonrecording gage at site 3 mi downstream at different datum.

REMARKS.--Flow completely regulated by Lake Elwell after Oct. 28, 1955. Bureau of Reclamation satellite telemeter at station.

Magnitude and probability of annual low flow

based on 46 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 270 137 84 52 28 --

3 287 149 91 56 29 --

7 291 151 98 64 38 --

14 294 157 111 81 54 --

30 300 175 126 93 64 --

60 345 208 148 108 72 --

90 390 237 169 123 82 --

120 449 270 190 136 89 --

183 572 343 242 173 112 --

Magnitude and probability of seasonal low flow from

March-June based on 47 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 357 202 142 103 69 --

3 360 206 145 106 72 --

7 378 216 151 109 73 --

14 385 219 155 114 78 --

30 446 242 170 124 85 --

Magnitude and probability of seasonal low flow from

November-February based on 46 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 275 141 87 54 29 --

3 296 152 94 58 30 --

7 298 158 102 66 39 --

14 302 165 117 83 56 --

30 306 179 132 96 65 --

Duration of daily mean flows based on 47 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

49 81 160 220 309 397 476 579

40% 30% 20% 15% 10% 5% 2% 1%

738 943 1,200 1,380 1,690 2,280 3,090 4,020

Magnitude and probability of annual high flow

based on 47 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 2,180 3,710 4,810 6,250 7,350 --

3 2,160 3,690 4,800 6,250 7,350 --

7 2,110 3,620 4,710 6,170 7,290 --

15 2,020 3,460 4,500 5,880 6,920 --

30 1,850 3,120 4,020 5,180 6,040 --

60 1,620 2,570 3,150 3,820 4,260 --

90 1,460 2,260 2,710 3,200 3,500 --

Magnitude and probability of seasonal low flow from

July-October based on 46 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 417 180 102 59 30 --

3 447 197 111 64 31 --

7 453 205 122 75 41 --

14 457 223 144 97 59 --

30 513 273 188 135 91 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 2,760 208 748 458 47

November 1,730 .40 600 369 47

December 1,050 16 448 225 47

January 1,080 35 407 222 47

February 1,070 35 440 245 47

March 2,030 48 571 385 47

April 2,340 46 789 557 47

May 2,610 51 1,140 657 47

June 6,250 59 1,690 1,220 47

July 5,320 58 1,280 971 47

August 2,910 82 976 641 47

September 3,060 192 892 513 47

Annual 1,490 98 832 328 47
Statistical Summaries of Streamflow 101

06102000 Marias River near Brinkman, Mont.

Site Number 83

LOCATION.--Lat 48°16', long 110°42' (NAD 27), in SE1⁄4 SE1⁄4 sec.17, T.29 N., R.8 E., Hill County, on left bank 4 mi southwest of Brinkman Post Office, 14 mi 

downstream from Cottonwood Creek, and 30 mi north of Fort Benton.

DRAINAGE AREA.--6,425 mi2 (revised), of which 518 mi2 is probably noncontributing. 

PERIOD OF RECORD.--35 years. October 1921 to September 1956 (discontinued).

GAGE.--Water-stage recorder. Altitude of gage is 2,677.25 ft (NGVD 29). Prior to Oct. 6, 1931, cantilever gage at site 2,800 ft downstream at datum 0.64 ft 

higher. Oct. 6, 1931, to July 1, 1939, water-stage recorder at site 1,600 ft downstream at present datum.

REMARKS.--Diversions for irrigation of about 65,000 acres upstream from station. Flow regulated by Tiber Reservoir after Oct 28, 1955, and four other reservoirs 

having a combined capacity of 177,870 acre-ft.

Magnitude and probability of annual low flow

based on 33 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 106 63 46 36 27 --

3 112 66 49 38 28 --

7 119 71 52 40 29 --

14 130 79 59 45 33 --

30 152 95 71 55 40 --

60 182 120 95 78 61 --

90 209 142 116 97 80 --

120 247 164 131 109 87 --

183 281 180 143 118 94 --

Magnitude and probability of seasonal low flow from

March-June based on 34 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 201 131 109 96 85 --

3 209 136 112 98 85 --

7 226 152 128 114 102 --

14 272 189 162 145 131 --

30 436 273 220 187 158 --

Magnitude and probability of seasonal low flow from

November-February based on 33 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 126 67 48 36 27 --

3 131 71 51 39 29 --

7 139 76 55 41 31 --

14 150 85 61 46 34 --

30 171 99 72 55 40 --

Duration of daily mean flows based on 34 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

57 72 99 140 199 248 312 393

40% 30% 20% 15% 10% 5% 2% 1%

526 826 1,410 1,900 2,580 3,770 5,420 6,790

Magnitude and probability of annual high flow

based on 34 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 4,940 9,650 14,600 24,000 34,000 --

3 4,710 8,830 12,900 20,100 27,300 --

7 4,340 7,730 10,700 15,600 20,100 --

15 3,840 6,460 8,520 11,500 14,000 --

30 3,310 5,390 6,970 9,160 10,900 --

60 2,810 4,390 5,470 6,840 7,870 --

90 2,340 3,620 4,470 5,550 6,340 --

Magnitude and probability of seasonal low flow from

July-October based on 33 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 165 93 70 56 44 --

3 169 96 73 59 46 --

7 175 100 76 61 48 --

14 185 108 83 68 55 --

30 208 123 96 80 65 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 1,470 85 413 291 34

November 1,600 120 405 300 34

December 803 94 304 168 34

January 700 40 231 130 34

February 1,000 52 307 240 34

March 2,400 165 627 498 34

April 3,210 291 1,260 743 34

May 5,360 691 2,680 1,110 34

June 11,300 727 3,260 2,500 34

July 3,460 182 1,170 843 34

August 1,110 88 399 276 34

September 1,370 87 348 268 34

Annual 1,990 338 952 447 34
102 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

6102050 Marias River near Loma, Mont.

Site Number 84

LOCATION.--Lat 47°55'59", long 111°31'02" (NAD 27), in SW1⁄4NE1⁄4SE1⁄4 sec.12, T.25 N., R.9 E., Choteau County, Hydrologic Unit 10030203, on left bank 

600 ft upstream from Teton River, 800 ft upstream from highway bridge, 0.2 mi southwest of Loma, and at river mile 2.5.

DRAINAGE AREA.--7,137 mi2, of which 518 mi2 is probably noncontributing.

PERIOD OF RECORD.--October 1959 to September 1972, June 2001 to current year (2002; seasonal records only).

GAGE.--Water-stage recorder. Altitude of gage is 2,570 ft (NGVD 29). Prior to June 2001, water-stage recorder at site 4.5 mi upstream at different datum.

REMARKS.--Flow completely regulated by Lake Elwell. Numerous diversions for irrigation upstream from station.

Magnitude and probability of annual low flow

based on 12 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 140 89 67 52 -- --

3 154 94 70 54 -- --

7 171 101 73 55 -- --

14 190 109 78 57 -- --

30 210 120 86 64 -- --

60 275 155 110 81 -- --

90 341 204 148 110 -- --

120 458 272 194 141 -- --

183 616 409 325 266 -- --

Magnitude and probability of seasonal low flow from

March-June based on 13 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 243 161 131 112 -- --

3 249 166 136 116 -- --

7 263 173 141 119 -- --

14 280 180 144 121 -- --

30 395 215 154 124 -- --

Magnitude and probability of seasonal low flow from

November-February based on 12 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 166 93 67 53 -- --

3 176 99 71 54 -- --

7 192 107 75 55 -- --

14 225 126 87 62 -- --

30 251 142 99 71 -- --

Duration of daily mean flows based on 13 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

80 96 126 187 303 393 499 768

40% 30% 20% 15% 10% 5% 2% 1%

975 1,190 1,410 1,580 2,000 2,770 3,950 5,090

Magnitude and probability of annual high flow

based on 13 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 2,850 4,540 6,050 8,540 -- --

3 2,750 4,470 6,000 8,480 -- --

7 2,620 4,290 5,800 8,290 -- --

15 2,460 4,020 5,390 7,610 -- --

30 2,230 3,520 4,620 6,340 -- --

60 1,930 2,750 3,390 4,290 -- --

90 1,730 2,460 3,000 3,740 -- --

Magnitude and probability of seasonal low flow from

July-October based on 12 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 289 132 91 68 -- --

3 340 149 97 68 -- --

7 378 166 108 76 -- --

14 456 221 151 111 -- --

30 505 255 179 134 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 2,750 292 942 608 13

November 1,580 78 723 450 13

December 908 106 402 207 13

January 517 105 298 126 13

February 910 110 434 245 13

March 1,290 117 568 366 13

April 2,180 180 878 549 14

May 2,180 441 1,320 445 14

June 6,020 693 2,260 1,360 14

July 2,990 250 1,400 839 15

August 3,040 138 1,200 892 15

September 3,260 296 1,110 725 15

Annual 1,330 522 977 281 13
Statistical Summaries of Streamflow 103

06106000 Deep Creek near Choteau, Mont.

Site Number 85

LOCATION.--Lat 47°45'07", long 112°14'22" (NAD 27), in SW1⁄4NW1⁄4 sec.15, T.23 N., R.5 W., Teton County, 2 mi downstream from Willow Creek and 5 mi 

southwest of Choteau.

DRAINAGE AREA.--223 mi2.

PERIOD OF RECORD.--13 years (1911-25).

GAGE.--Chain gage. Altitude of gage is 3,860 ft (NGVD 29, by barometer).

REMARKS.--Several small diversions for irrigation upstream from station.

Magnitude and probability of annual low flow

based on 12 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 12 7.6 5.4 4.0 -- --

3 13 7.7 5.5 4.0 -- --

7 13 8.2 6.3 4.9 -- --

14 13 8.8 7.3 6.2 -- --

30 16 11 9.1 7.8 -- --

60 18 12 10 8.5 -- --

90 20 14 11 9.7 -- --

120 25 17 13 11 -- --

183 28 20 17 15 -- --

Magnitude and probability of seasonal low flow from

March-June based on 13 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 18 11 7.9 6.3 -- --

3 18 11 8.1 6.4 -- --

7 19 11 8.4 6.6 -- --

14 21 12 8.7 6.7 -- --

30 34 21 16 12 -- --

Magnitude and probability of seasonal low flow from

November-February based on 13 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 15 13 12 11 -- --

3 16 13 12 11 -- --

7 16 13 12 11 -- --

14 16 13 12 11 -- --

30 16 13 12 11 -- --

Duration of daily mean flows based on 13 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

6.7 8.2 12 14 18 23 30 37

40% 30% 20% 15% 10% 5% 2% 1%

44 61 89 116 157 240 397 643

Magnitude and probability of annual high flow

based on 13 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 504 1,160 1,820 2,990 -- --

3 415 916 1,400 2,240 -- --

7 337 734 1,130 1,810 -- --

15 275 581 887 1,430 -- --

30 225 451 665 1,030 -- --

60 178 332 465 671 -- --

90 147 260 356 504 -- --

Magnitude and probability of seasonal low flow from

July-October based on 14 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 20 9.9 6.5 4.4 -- --

3 21 11 6.8 4.5 -- --

7 22 11 7.7 5.4 -- --

14 22 13 9.1 6.8 -- --

30 24 14 10 8.1 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 89 11 36 21 14

November 67 14 35 13 14

December 87 15 31 19 14

January 75 13 23 17 13

February 51 12 22 11 13

March 86 13 39 20 13

April 149 30 71 35 14

May 584 50 190 130 14

June 752 24 225 205 14

July 529 11 100 129 14

August 112 8.4 42 28 14

September 77 8.6 33 21 14

Annual 165 28 72 41 13
104 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06108000 Teton River near Dutton, Mont.

Site Number 86

LOCATION.--Lat 47°55'49", long 111°33'07" (NAD 27), in SE1⁄4SW1⁄4SW1⁄4 sec.12, T.25 N., R.1 E., Teton County, Hydrologic Unit 10030205, on right bank 

150 ft upstream from Kerr Bridge, 0.9 mi downstream from Hunt Coulee, 9.5 mi northeast of Dutton, and at river mile 100.9.

DRAINAGE AREA.--1,307 mi2. Area at site used prior to July 17, 1965, 1,308 mi2.

PERIOD OF RECORD.--August 1954 to current year (2002).

GAGE.--Water-stage recorder. Altitude of gage is 3,235 ft (NGVD 29). Prior to July 17, 1965, water-stage recorder at site 1,800 ft downstream at datum 1.97 ft 

lower.

REMARKS.--Water is diverted on left bank in sec.34, T.25 N., R.7 W., for storage in Bynum Reservoir (usable capacity, 75,000 acre-ft). Diversions for irrigation 

of about 44,000 acres upstream from station. U.S. Geological Survey satellite telemeter at station.

Magnitude and probability of annual low flow

based on 47 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 22 9.2 0.00 0.00 0.00 --

3 23 9.9 .00 .00 .00 --

7 32 11 3.0 .94 .00 --

14 36 11 3.5 1.1 .00 --

30 36 11 3.8 1.2 .00 --

60 40 16 8.0 4.2 1.9 --

90 44 21 13 8.3 4.8 --

120 48 25 17 12 7.3 --

183 54 30 21 16 11 --

Magnitude and probability of seasonal low flow from

March-June based on 48 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 41 21 14 9.8 6.5 --

3 43 22 15 11 7.3 --

7 48 24 17 12 8.4 --

14 58 30 21 15 11 --

30 79 40 28 20 13 --

Magnitude and probability of seasonal low flow from

November-February based on 48 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 27 17 13 10 8.2 --

3 29 18 14 11 8.5 --

7 33 20 15 12 9.3 --

14 37 23 17 13 10 --

30 42 26 20 16 12 --

Duration of daily mean flows based on 48 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

2.5 8.2 16 23 36 48 59 72

40% 30% 20% 15% 10% 5% 2% 1%

90 118 167 206 271 454 747 1,080

Magnitude and probability of annual high flow

based on 48 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 858 2,360 4,080 7,450 11,100 --

3 748 1,940 3,210 5,510 7,840 --

7 599 1,440 2,270 3,660 4,980 --

15 464 1,040 1,590 2,470 3,280 --

30 367 778 1,150 1,720 2,230 --

60 273 554 800 1,180 1,520 --

90 232 455 643 929 1,180 --

Magnitude and probability of seasonal low flow from

July-October based on 47 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 29 9.9 0.00 0.00 0.00 --

3 31 10 .00 .00 .00 --

7 40 11 4.0 1.2 .00 --

14 43 11 4.2 1.4 .00 --

30 44 11 4.3 1.5 .00 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 223 15 70 48 48

November 176 18 71 37 48

December 208 15 65 40 48

January 167 13 56 30 48

February 388 15 87 73 48

March 819 29 184 174 48

April 495 47 160 105 48

May 957 20 248 219 48

June 2,730 17 392 495 48

July 551 1.3 160 147 48

August 263 .00 74 59 49

September 211 7.4 66 49 49

Annual 350 27 136 79 48
Statistical Summaries of Streamflow 105

06109000 Missouri River at Loma, Mont.

Site Number 87

LOCATION.--Lat 47°56'04", long 110°28'02" (NAD 27), in NW1⁄4SE1⁄4 sec.8, T.25 N., R.10 E., Chouteau County, 1.5 mi (revised) east of Loma and 0.5 mi 

downstream from Marias River.

DRAINAGE AREA.--34,221 mi2.

PERIOD OF RECORD.--15 years (1935-50).

GAGE.--Water-stage recorder. Altitude of gage is 2,543.40 ft (NGVD 29).

REMARKS.--Diversions for irrigation of about 830,000 acres upstream from station. Flow regulated by 22 smaller irrigation reservoirs and powerplants.

Magnitude and probability of annual low flow

based on 15 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 3,550 2,940 2,660 2,450 -- --

3 3,610 3,030 2,760 2,550 -- --

7 3,620 3,040 2,780 2,570 -- --

14 3,630 3,060 2,780 2,580 -- --

30 3,640 3,060 2,790 2,590 -- --

60 3,830 3,200 2,900 2,670 -- --

90 4,050 3,360 3,050 2,810 -- --

120 4,280 3,540 3,190 2,910 -- --

183 4,440 3,690 3,340 3,060 -- --

Magnitude and probability of seasonal low flow from

March-June based on 16 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 5,570 4,330 3,810 3,430 -- --

3 5,610 4,540 4,120 3,820 -- --

7 5,640 4,560 4,140 3,830 -- --

14 5,690 4,590 4,140 3,840 -- --

30 5,710 4,600 4,150 3,850 -- --

Magnitude and probability of seasonal low flow from

November-February based on 15 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 4,090 3,230 2,810 2,490 -- --

3 4,130 3,290 2,880 2,570 -- --

7 4,140 3,300 2,880 2,580 -- --

14 4,150 3,310 2,890 2,590 -- --

30 4,160 3,320 2,900 2,600 -- --

Duration of daily mean flows based on 15 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

2,480 2,750 3,180 3,410 3,870 4,330 4,860 5,400

40% 30% 20% 15% 10% 5% 2% 1%

5,930 7,390 10,100 12,600 15,500 21,100 29,100 36,500

Magnitude and probability of annual high flow

based on 15 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 18,200 29,100 37,500 49,300 -- --

3 18,100 28,900 37,200 49,000 -- --

7 18,100 28,900 37,100 48,900 -- --

15 18,000 28,800 37,100 48,800 -- --

30 18,000 28,800 37,100 48,800 -- --

60 15,400 23,400 29,100 36,700 -- --

90 13,600 20,100 24,700 30,700 -- --

Magnitude and probability of seasonal low flow from

July-October based on 15 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 3,720 3,200 2,990 2,850 -- --

3 3,760 3,270 3,080 2,950 -- --

7 3,770 3,290 3,100 2,970 -- --

14 3,780 3,300 3,110 2,990 -- --

30 3,790 3,300 3,120 3,000 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 7,230 3,530 4,920 1,120 15

November 6,730 3,210 5,020 1,170 15

December 6,830 3,220 4,720 1,100 15

January 5,810 2,720 4,280 991 15

February 6,840 2,600 4,550 1,210 15

March 10,200 3,780 6,070 1,730 16

April 17,700 4,800 8,740 3,960 16

May 27,200 4,860 13,500 5,930 16

June 52,000 7,540 20,000 12,200 16

July 15,900 3,700 8,220 4,370 16

August 7,780 2,820 4,390 1,490 16

September 6,240 2,820 4,330 956 16

Annual 13,300 4,150 7,500 2,640 15
106 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06109500 Missouri River at Virgelle, Mont.

Site Number 88

LOCATION.--Lat 48°00'18", long 110°15'25" (NAD 27), in SW1⁄4SW1⁄4SE1⁄4 sec.13, T.26 N., R.11 E., Chouteau County, Hydrologic Unit 10040101, on left bank 

0.2 mi upstream from Virgelle ferry, 0.6 mi southwest of Virgelle, 1.8 mi downstream from Spring Coulee, and at river mile 2,034.2.

DRAINAGE AREA.--34,379 mi2.

PERIOD OF RECORD.--February 1935 to current year (2002). Prior to October 1953, published as "at Loma."

REVISED RECORDS.--WSP 1729: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 2,507.50 ft (NGVD 29). Prior to Sept. 30, 1953, water-stage recorder at Loma, 18 mi upstream, 2,543.40 ft.

REMARKS.--Flow regulated by 23 smaller irrigation reservoirs and powerplants, Clark Canyon Reservoir (station number 06015300), Canyon Ferry Lake (station 

number 06058500), and Lake Elwell (station number 06101300). Diversions for irrigation of about 850,400 acres upstream from station. U.S. Army Corps of 

Engineers satellite telemeter at station.

Unregulated streamflow period

Magnitude and probability of annual low flow

based on 17 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 2,740 1,830 1,360 1,010 -- --

3 3,050 2,450 2,170 1,950 -- --

7 3,430 2,740 2,400 2,140 -- --

14 3,580 2,880 2,540 2,280 -- --

30 3,670 3,000 2,690 2,460 -- --

60 3,890 3,200 2,890 2,650 -- --

90 4,180 3,410 3,060 2,790 -- --

120 4,450 3,620 3,230 2,930 -- --

183 4,620 3,780 3,390 3,080 -- --

Magnitude and probability of seasonal low flow from

March-June based on 18 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 4,080 3,300 2,950 2,690 -- --

3 4,390 3,660 3,320 3,070 -- --

7 4,690 3,940 3,590 3,320 -- --

14 5,010 4,210 3,850 3,560 -- --

30 5,950 4,690 4,160 3,780 -- --

Magnitude and probability of seasonal low flow from

November-February based on 17 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 2,870 2,200 1,870 1,610 -- --

3 3,260 2,570 2,240 1,970 -- --

7 3,750 2,940 2,520 2,180 -- --

14 3,970 3,130 2,700 2,350 -- --

30 4,210 3,340 2,890 2,540 -- --

Duration of daily mean flows based on 17 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

2,300 2,480 3,010 3,340 3,890 4,430 4,980 5,530

40% 30% 20% 15% 10% 5% 2% 1%

6,070 7,450 9,330 11,900 16,100 22,900 31,300 36,600

Magnitude and probability of annual high flow

based on 17 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 25,900 40,000 51,300 67,900 -- --

3 25,500 38,400 48,000 61,200 -- --

7 24,800 37,100 45,700 57,100 -- --

15 22,900 34,700 42,700 53,100 -- --

30 20,400 31,100 38,400 47,700 -- --

60 17,300 25,600 30,800 37,200 -- --

90 14,600 21,400 25,900 31,400 -- --

Magnitude and probability of seasonal low flow from

July-October based on 17 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 3,170 2,010 1,460 1,070 -- --

3 3,350 2,730 2,490 2,330 -- --

7 3,650 3,030 2,790 2,610 -- --

14 3,770 3,140 2,880 2,710 -- --

30 3,850 3,220 2,970 2,800 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 7,640 3,530 5,210 1,330 17

November 7,090 3,210 5,260 1,290 17

December 7,040 3,220 4,910 1,180 17

January 5,810 2,720 4,400 997 17

February 6,970 2,600 4,740 1,280 17

March 10,200 3,780 6,410 1,910 18

April 17,700 4,970 9,300 4,100 18

May 27,200 4,860 14,800 6,670 18

June 52,000 7,540 20,000 11,500 18

July 15,900 3,700 8,490 4,250 18

August 7,780 2,820 4,510 1,450 18

September 6,760 2,820 4,470 1,060 18

Annual 13,300 4,150 7,810 2,620 17
Statistical Summaries of Streamflow 107

06109500 Missouri River at Virgelle, Mont.—Continued

Site Number 88

Regulated streamflow period

Magnitude and probability of annual low flow

based on 49 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 3,940 3,200 2,850 2,580 2,300 --

3 4,400 3,690 3,360 3,100 2,830 --

7 4,890 4,130 3,780 3,510 3,220 --

14 5,130 4,350 3,980 3,710 3,420 --

30 5,360 4,510 4,130 3,830 3,530 --

60 5,580 4,680 4,270 3,970 3,650 --

90 5,830 4,850 4,410 4,080 3,740 --

120 6,030 5,020 4,560 4,200 3,840 --

183 6,390 5,280 4,770 4,380 3,970 --

Magnitude and probability of seasonal low flow from

March-June based on 50 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 5,440 4,140 3,570 3,140 2,710 2,450

3 5,860 4,560 3,980 3,550 3,110 2,840

7 6,230 4,910 4,320 3,880 3,430 3,160

14 6,520 5,160 4,560 4,120 3,670 3,390

30 6,900 5,430 4,810 4,370 3,920 3,660

Magnitude and probability of seasonal low flow from

November-February based on 49 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 4,230 3,460 3,100 2,820 2,520 --

3 4,720 3,930 3,550 3,260 2,940 --

7 5,350 4,520 4,100 3,770 3,420 --

14 5,720 4,860 4,430 4,100 3,730 --

30 6,020 5,100 4,660 4,310 3,930 --

Duration of daily mean flows based on 50 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

3,320 3,580 4,310 4,630 5,280 5,930 6,610 7,290

40% 30% 20% 15% 10% 5% 2% 1%

7,970 8,660 10,700 11,800 14,900 20,600 27,400 32,700

Magnitude and probability of annual high flow

based on 50 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 22,100 36,900 49,000 67,000 82,600 100,000

3 21,600 35,700 46,700 62,500 75,800 90,300

7 20,700 33,100 42,000 54,000 63,400 73,100

15 19,300 30,100 37,400 46,900 54,000 61,100

30 17,700 26,700 32,700 40,200 45,600 51,000

60 15,200 21,900 26,100 31,000 34,400 37,600

90 13,300 18,700 22,000 25,900 28,700 31,300

Magnitude and probability of seasonal low flow from

July-October based on 49 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 4,740 3,710 3,270 2,950 2,630 --

3 5,020 4,060 3,660 3,370 3,090 --

7 5,270 4,290 3,890 3,590 3,310 --

14 5,420 4,420 4,010 3,720 3,430 --

30 5,610 4,570 4,140 3,840 3,540 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 15,300 3,870 6,510 1,970 50

November 12,500 4,050 6,720 1,740 50

December 12,200 3,870 6,730 1,500 50

January 9,000 3,990 6,900 1,260 50

February 10,200 4,140 7,230 1,490 50

March 14,500 4,210 7,700 2,320 50

April 15,200 4,060 8,490 2,750 50

May 28,300 4,820 12,900 5,240 50

June 44,800 4,650 17,200 9,540 50

July 29,700 4,030 10,300 5,160 50

August 12,000 4,020 6,760 1,960 50

September 11,600 3,820 6,350 1,930 50

Annual 13,700 4,560 8,650 2,150 50
108 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06109800 South Fork Judith River near Utica, Mont.

Site Number 89

LOCATION.--Lat 46°45'00", long 110°18'54" (NAD 27), in SE1⁄4NE1⁄4SW1⁄4 sec.34, T.12 N., R.ll E., Judith Basin County, Hydrologic Unit 10040103, Lewis and 

Clark National Forest, on right bank just downstream from Trask Gulch, 8 mi upstream from confluence with Middle Fork, and 18 mi southwest of Utica. 

DRAINAGE AREA.--58.7 mi2. 

PERIOD OF RECORD.--20 years. August 1958 to September 1979 (discontinued). 

GAGE.--Water-stage recorder. Altitude of gage is 5,420 ft (NGVD 29, from topographic map). 

REMARKS.--Minor diversions for irrigation upstream from station.

Magnitude and probability of annual low flow

based on 20 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 2.5 1.9 1.6 1.4 -- --

3 2.7 2.1 1.8 1.6 -- --

7 2.9 2.3 2.0 1.8 -- --

14 3.2 2.6 2.4 2.2 -- --

30 3.5 3.0 2.8 2.6 -- --

60 3.9 3.3 3.1 2.9 -- --

90 4.1 3.5 3.3 3.1 -- --

120 4.4 3.8 3.5 3.3 -- --

183 5.5 4.6 4.1 3.7 -- --

Magnitude and probability of seasonal low flow from

March-June based on 21 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 3.4 2.7 2.3 2.0 -- --

3 3.5 2.8 2.4 2.0 -- --

7 3.6 2.9 2.5 2.2 -- --

14 3.8 3.0 2.6 2.3 -- --

30 4.4 3.4 3.1 2.9 -- --

Magnitude and probability of seasonal low flow from

November-February based on 21 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 2.6 1.9 1.7 1.5 -- --

3 2.8 2.1 1.8 1.6 -- --

7 3.0 2.3 2.1 1.8 -- --

14 3.3 2.7 2.4 2.2 -- --

30 3.6 3.1 2.8 2.6 -- --

Duration of daily mean flows based on 21 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

2.2 2.5 3.0 3.4 4.1 4.8 5.6 7.0

40% 30% 20% 15% 10% 5% 2% 1%

9.2 14 25 36 58 104 177 244

Magnitude and probability of annual high flow

based on 21 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 221 453 658 976 -- --

3 200 365 485 644 -- --

7 175 294 369 458 -- --

15 143 235 292 359 -- --

30 112 183 227 280 -- --

60 83 135 168 207 -- --

90 66 102 124 147 -- --

Magnitude and probability of seasonal low flow from

July-October based on 20 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 5.1 3.9 3.3 2.9 -- --

3 5.4 4.4 3.9 3.6 -- --

7 5.8 4.7 4.2 3.9 -- --

14 6.2 5.0 4.4 4.0 -- --

30 6.6 5.3 4.7 4.2 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 12 3.8 6.8 1.8 21

November 9.2 2.9 5.3 1.4 21

December 6.5 2.3 4.4 1.1 21

January 6.0 2.6 3.9 .99 21

February 4.9 2.8 4.0 .57 21

March 13 2.4 5.1 2.3 21

April 47 5.3 21 14 21

May 194 24 104 52 21

June 234 13 73 59 21

July 52 5.3 23 12 21

August 19 3.7 12 3.9 21

September 15 4.0 8.4 2.6 22

Annual 42 6.5 23 9.4 21
Statistical Summaries of Streamflow 109

06110000 Judith River near Utica, Mont.

Site Number 90

LOCATION.--Lat 46°53'30", long 110°13'54" (NAD 27), in NW1⁄4 sec.17, T.13 N., R.12 E., Judith Basin County, on left bank at Noel Ranch, 4 mi downstream 

from confluence of South and Middle Forks, 9 mi southwest of Utica, and at river mile 99.3.

DRAINAGE AREA.--328 mi2 . 

PERIOD OF RECORD.--56 years. October 1919 to September 1975 (discontinued). Monthly discharge only for some periods, published in WSP 1309.

REVISED RECORDS (WATER YEARS)--WSP 896: 1939. WSP 1309: 1920, 1922(M), 1925, 1927(M), 1929-30, 1931(M), 1936(M), 1938(M).

GAGE.--Water-stage recorder. Concrete control after October 1938. Altitude of gage is 4,790 ft (NGVD 29, by barometer). Prior to June 6, 1937, nonrecording 

gage at present site and datum.

REMARKS.--Minor diversions for irrigation upstream from station.

Magnitude and probability of annual low flow

based on 55 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1.1 0.45 0.26 0.15 0.04 0.00

3 1.1 .47 .28 .17 .04 .00

7 1.2 .50 .32 .21 .13 .09

14 1.2 .56 .36 .24 .16 .12

30 1.4 .69 .46 .32 .21 .16

60 2.1 1.0 .69 .48 .32 .24

90 3.7 2.0 1.4 1.1 .75 .59

120 4.8 2.6 1.8 1.3 .87 .66

183 7.4 3.9 2.6 1.9 1.3 .95

Magnitude and probability of seasonal low flow from

March-June based on 56 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1.3 0.51 0.31 0.20 0.07 0.00

3 1.3 .53 .33 .22 .08 .00

7 1.4 .56 .36 .25 .17 .13

14 1.4 .61 .40 .29 .20 .16

30 1.8 .75 .49 .35 .25 .20

Magnitude and probability of seasonal low flow from

November-February based on 55 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1.7 0.76 0.48 0.33 0.20 0.15

3 1.8 .80 .50 .34 .21 .15

7 1.9 .86 .54 .36 .22 .16

14 2.0 .94 .60 .41 .25 .18

30 2.2 1.1 .73 .51 .34 .25

Duration of daily mean flows based on 56 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

0.20 0.40 1.0 1.5 2.4 3.9 6.1 9.6

40% 30% 20% 15% 10% 5% 2% 1%

15 27 64 106 175 310 471 611

Magnitude and probability of annual high flow

based on 56 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 438 719 890 1,080 1,200 1,310

3 422 686 842 1,010 1,120 1,220

7 388 624 760 908 1,000 1,080

15 344 552 675 810 896 972

30 300 482 589 706 781 846

60 231 367 442 520 567 605

90 177 281 339 398 433 462

Magnitude and probability of seasonal low flow from

July-October based on 55 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 8.1 3.8 2.4 1.6 0.98 0.68

3 8.4 4.0 2.6 1.7 1.0 .73

7 8.8 4.2 2.7 1.8 1.1 .76

14 9.2 4.5 2.9 2.0 1.2 .88

30 10 4.9 3.2 2.2 1.4 .97

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 50 1.1 13 9.4 56

November 33 .75 9.3 6.6 56

December 25 .50 6.0 4.1 56

January 18 .40 3.7 2.8 56

February 30 .30 3.3 4.2 56

March 51 .21 3.9 7.1 56

April 129 .25 22 32 56

May 475 8.9 194 108 56

June 835 33 271 184 56

July 286 9.6 85 61 56

August 97 4.4 29 20 56

September 51 1.5 16 11 56

Annual 141 8.8 55 29 56
110 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06111000 Ross Fork Creek near Hobson, Mont.

Site Number 91

LOCATION.--Lat 46°59'34", long 109°48'42" (NAD 27), in NW1⁄4 sec.11, T.14 N., R.15 E., Judith Basin County, on left bank 1 mi downstream from Hauck 

Coulee, 3.5 mi east of Hobson, and 7 mi upstream from mouth.

DRAINAGE AREA.--337 mi2.

PERIOD OF RECORD.--14 years. June 1946 to December 1953 and March 1955 to September 1962 (discontinued).

GAGE.--Water-stage recorder. Altitude of gage is 3,860 ft (NGVD 29, by barometer). 

REMARKS.--Minor diversions for irrigation upstream from station. Flow may be augmented by operation of Ackley Lake, which receives water from Judith 

River.

Magnitude and probability of annual low flow

based on 12 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.00 0.00 0.00 0.00 -- --

3 .00 .00 .00 .00 -- --

7 .00 .00 .00 .00 -- --

14 .00 .00 .00 .00 -- --

30 .02 .00 .00 .00 -- --

60 .19 .00 .00 .00 -- --

90 .42 .07 .00 .00 -- --

120 .76 .29 .10 .00 -- --

183 1.2 .73 .51 .00 -- --

Magnitude and probability of seasonal low flow from

March-June based on 14 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1.8 0.47 0.11 0.00 -- --

3 2.2 .51 .13 .00 -- --

7 2.4 .77 .26 .00 -- --

14 3.0 1.0 .48 .24 -- --

30 5.4 2.0 1.1 .66 -- --

Magnitude and probability of seasonal low flow from

November-February based on 14 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.55 0.00 0.00 0.00 -- --

3 .67 .00 .00 .00 -- --

7 .79 .00 .00 .00 -- --

14 .88 .43 .24 .00 -- --

30 1.2 .70 .52 .00 -- --

Duration of daily mean flows based on 14 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

0.04 0.08 0.19 0.38 0.76 1.2 1.8 2.6

40% 30% 20% 15% 10% 5% 2% 1%

3.6 5.5 11 17 28 52 139 271

Magnitude and probability of annual high flow

based on 14 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 341 987 1,480 2,080 -- --

3 275 780 1,150 1,560 -- --

7 196 516 735 972 -- --

15 129 309 424 546 -- --

30 86 197 271 351 -- --

60 56 115 150 184 -- --

90 42 82 104 126 -- --

Magnitude and probability of seasonal low flow from

July-October based on 15 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.00 0.00 0.00 0.00 -- --

3 .00 .00 .00 .00 -- --

7 .00 .00 .00 .00 -- --

14 .00 .00 .00 .00 -- --

30 .05 .00 .00 .00 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 3.4 0.00 0.97 0.98 15

November 6.1 .00 2.1 1.5 15

December 8.9 .00 2.7 2.0 15

January 4.9 .70 2.1 1.3 14

February 12 .98 4.9 3.1 14

March 175 2.9 63 57 14

April 219 2.0 49 63 15

May 133 2.6 27 35 15

June 125 .71 24 31 15

July 11 .00 3.9 2.7 16

August 4.8 .00 1.1 1.3 16

September 2.5 .00 .44 .64 16

Annual 26 1.4 14 8.2 14
Statistical Summaries of Streamflow 111

06111500 Big Spring Creek near Lewistown, Mont.

Site Number 92

LOCATION.--Lat 47°00'20", long 109°21'00" (NAD 27), SW1⁄4 NW1⁄4 sec.5, T.14 N., R.19 E., Fergus County, on upstream side of left wingwall of old highway 

bridge, 0.5 mi downstream from Big Springs and 5 mi southeast of Lewistown.

DRAINAGE AREA.--20.9 mi2 (revised). 

PERIOD OF RECORD.--25 years. June 1932 to September 1957 (discontinued).

GAGE.--Water-stage recorder. Altitude of gage is 4,130 ft (NGVD 29, by barometer). Prior to Apr. 27, 1955, staff gage on downstream left wingwall.

REMARKS.--Water diversion upstream from station.

Magnitude and probability of annual low flow

based on 24 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 94 86 82 79 -- --

3 95 86 82 79 -- --

7 95 87 83 79 -- --

14 96 88 83 80 -- --

30 97 89 84 80 -- --

60 99 91 87 83 -- --

90 100 92 88 85 -- --

120 101 93 89 86 -- --

183 102 94 91 88 -- --

Magnitude and probability of seasonal low flow from

March-June based on 25 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 98 90 86 82 78 --

3 99 90 86 82 78 --

7 100 91 86 83 78 --

14 100 92 87 83 79 --

30 102 93 88 84 80 --

Magnitude and probability of seasonal low flow from

November-February based on 25 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 99 90 86 82 79 --

3 100 90 86 82 79 --

7 100 90 86 83 79 --

14 101 91 87 83 80 --

30 102 92 88 84 81 --

Duration of daily mean flows based on 25 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

69 71 79 93 97 102 106 110

40% 30% 20% 15% 10% 5% 2% 1%

115 119 123 125 128 130 164 177

Magnitude and probability of annual high flow

based on 25 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 127 158 181 214 242 --

3 123 148 167 195 217 --

7 121 141 156 177 193 --

15 118 134 145 161 173 --

30 115 128 138 150 160 --

60 112 124 133 145 154 --

90 111 123 132 144 153 --

Magnitude and probability of seasonal low flow from

July-October based on 25 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 98 91 88 87 85 --

3 99 92 89 87 85 --

7 99 92 89 87 85 --

14 100 93 90 87 85 --

30 101 94 91 89 86 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 154 90 109 13 25

November 157 88 108 13 25

December 157 88 108 14 25

January 155 84 106 14 25

February 145 77 106 13 25

March 136 80 108 13 25

April 128 81 107 11 25

May 156 82 106 14 25

June 144 83 109 14 26

July 143 84 106 11 26

August 140 86 106 11 26

September 145 90 109 11 26

Annual 134 87 107 10 25
112 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06115200 Missouri River near Landusky, Mont.

Site Number 93

LOCATION.--Lat 47°37'51", long 108°41'13" (NAD 27), in NW1⁄4NE1⁄4 sec.31, T.22 N., R.24 E., Fergus County, Hydrologic Unit 10040104, Charles M. Russell 

National Wildlife Refuge, on right bank 380 ft upstream from bridge on U.S. Highway 191, 0.9 mi upstream from Armells Creek, 20 mi south of Landusky, 

and at river mile 1,921.61.

DRAINAGE AREA.--40,987 mi2. Area at site used prior to Dec. 13, 1968, 40,763 mi2.

PERIOD OF RECORD.--February 1934 to current year (2002). Prior to October 1968, published as "at powerplant ferry, near Zortman."

REVISED RECORDS.--WSP 1729: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 2,239.96 ft (NGVD 29, State Highway bench mark). Prior to Feb. 7, 1935, nonrecording gage, and Feb. 7, 

1935, to Dec. 12, 1968, water-stage recorder, at site 16.5 mi upstream at datum 33.06 ft higher.

REMARKS.--Flow regulated by 24 smaller irrigation reservoirs and powerplants, Clark Canyon Reservoir (station number 06015300), Canyon Ferry Lake (station 

number 06058500), and Lake Elwell (station number 06101300). Diversions for irrigation of about 870,400 acres upstream from station. U.S. Army Corps of 

Engineers satellite telemeter at station.

Unregulated streamflow period

Magnitude and probability of annual low flow

based on 18 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 2,630 1,880 1,560 1,320 -- --

3 2,950 2,120 1,730 1,450 -- --

7 3,420 2,550 2,120 1,800 -- --

14 3,680 2,820 2,410 2,090 -- --

30 3,880 3,000 2,570 2,240 -- --

60 4,150 3,240 2,800 2,470 -- --

90 4,440 3,460 3,000 2,650 -- --

120 4,730 3,720 3,250 2,900 -- --

183 4,900 3,910 3,450 3,100 -- --

Magnitude and probability of seasonal low flow from

March-June based on 19 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 4,430 3,490 3,070 2,750 -- --

3 4,740 3,770 3,320 2,970 -- --

7 5,130 4,150 3,680 3,310 -- --

14 5,560 4,590 4,140 3,790 -- --

30 6,790 5,440 4,910 4,550 -- --

Magnitude and probability of seasonal low flow from

November-February based on 18 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 2,730 1,970 1,630 1,380 -- --

3 3,050 2,200 1,810 1,520 -- --

7 3,590 2,680 2,240 1,910 -- --

14 3,930 3,050 2,630 2,300 -- --

30 4,330 3,340 2,860 2,490 -- --

Duration of daily mean flows based on 18 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

2,210 2,470 3,140 3,440 4,040 4,670 5,310 5,950

40% 30% 20% 15% 10% 5% 2% 1%

6,950 8,070 10,400 12,800 16,800 24,100 33,600 42,600

Magnitude and probability of annual high flow

based on 18 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 28,200 44,600 57,500 76,100 -- --

3 27,400 42,400 53,800 69,600 -- --

7 26,100 39,700 49,300 62,200 -- --

15 23,700 36,300 45,300 57,500 -- --

30 21,100 32,500 40,500 51,200 -- --

60 17,800 26,600 32,400 39,600 -- --

90 15,200 22,400 27,300 33,600 -- --

Magnitude and probability of seasonal low flow from

July-October based on 18 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 3,400 2,340 1,890 1,560 -- --

3 3,780 2,760 2,310 1,970 -- --

7 4,010 3,010 2,560 2,220 -- --

14 4,100 3,110 2,670 2,330 -- --

30 4,180 3,210 2,790 2,480 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 8,440 3,270 5,530 1,530 18

November 7,980 3,580 5,720 1,400 18

December 7,610 3,120 5,130 1,350 18

January 6,490 2,800 4,690 1,150 18

February 8,450 2,510 5,120 1,630 18

March 13,400 4,880 7,520 2,340 19

April 19,200 5,360 10,300 4,480 19

May 27,200 5,260 15,100 6,850 19

June 55,300 8,170 21,100 12,300 19

July 17,700 3,960 9,320 4,830 19

August 8,250 2,080 4,840 1,720 19

September 7,640 2,500 4,770 1,290 19

Annual 14,200 4,440 8,350 2,860 18
Statistical Summaries of Streamflow 113

06115200 Missouri River near Landusky, Mont.—Continued

Site Number 93

Regulated streamflow period

Magnitude and probability of annual low flow

based on 49 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 4,220 3,360 2,980 2,690 2,400 --

3 4,630 3,690 3,260 2,930 2,580 --

7 5,080 4,170 3,740 3,410 3,070 --

14 5,390 4,510 4,100 3,780 3,450 --

30 5,690 4,770 4,340 4,010 3,670 --

60 5,950 4,980 4,530 4,180 3,820 --

90 6,230 5,170 4,670 4,290 3,890 --

120 6,440 5,330 4,810 4,420 4,000 --

183 6,810 5,610 5,040 4,610 4,160 --

Magnitude and probability of seasonal low flow from

March-June based on 50 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 5,960 4,570 3,950 3,490 3,020 2,740

3 6,350 4,950 4,320 3,830 3,340 3,040

7 6,700 5,290 4,650 4,160 3,670 3,370

14 7,090 5,580 4,910 4,410 3,900 3,590

30 7,750 5,980 5,230 4,680 4,140 3,810

Magnitude and probability of seasonal low flow from

November-February based on 49 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 4,590 3,580 3,120 2,770 2,410 --

3 4,960 3,890 3,380 2,990 2,590 --

7 5,560 4,490 3,970 3,560 3,130 --

14 5,980 4,960 4,470 4,080 3,670 --

30 6,340 5,330 4,850 4,460 4,050 --

Duration of daily mean flows based on 50 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

3,450 3,830 4,450 4,870 5,700 6,450 7,130 7,810

40% 30% 20% 15% 10% 5% 2% 1%

8,480 9,810 11,400 13,000 16,200 22,500 30,300 34,600

Magnitude and probability of annual high flow

based on 50 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 24,800 42,400 56,800 78,400 97,000 118,000

3 24,000 40,500 53,700 72,900 89,200 107,000

7 23,000 37,400 47,900 62,300 73,600 85,400

15 21,400 33,700 42,200 53,200 61,500 69,900

30 19,300 29,500 36,300 44,900 51,100 57,300

60 16,600 24,100 28,800 34,400 38,300 42,100

90 14,600 20,600 24,400 28,800 31,900 34,800

Magnitude and probability of seasonal low flow from

July-October based on 49 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 5,100 4,010 3,550 3,220 2,900 --

3 5,370 4,320 3,890 3,570 3,270 --

7 5,620 4,540 4,080 3,740 3,410 --

14 5,780 4,670 4,200 3,860 3,520 --

30 6,000 4,860 4,370 4,020 3,680 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 16,500 3,930 6,910 2,060 50

November 13,900 4,140 7,130 1,850 50

December 13,200 4,000 7,170 1,600 50

January 10,800 4,170 7,310 1,400 50

February 11,400 4,330 7,870 1,680 50

March 19,700 4,310 8,930 3,060 50

April 16,400 4,340 9,280 3,110 50

May 30,500 4,860 14,000 5,910 50

June 53,700 4,940 18,900 10,900 50

July 33,600 4,150 11,300 5,780 50

August 12,600 3,900 7,270 2,110 50

September 12,300 3,780 6,770 1,990 50

Annual 15,300 4,600 9,410 2,370 50
114 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06115500 North Fork Musselshell River near Delpine, Mont.

Site Number 94

LOCATION.--Lat 46°36'36", long 110°34'30" (NAD 27), in SW1⁄4 SE1⁄4 sec.22, T.10 N., R.9 E., Meagher County, Hydrologic Unit 10040201, on right bank 0.5 mi 

upstream from high-water line of Bair Reservoir at elevation 5,330 ft, 3 mi downstream from Lion Creek, and northwest of Delpine.

DRAINAGE AREA.--31.4 mi2 . 

PERIOD OF RECORD.--36 years (1940-80).

REVISED RECORDS.--WSP 1559: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 5,380 ft (NGVD 29, by barometer). 

REMARKS.--Minor diversions for irrigation upstream from station. 

Magnitude and probability of annual low flow

based on 35 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 3.2 2.5 2.2 2.0 1.7 --

3 3.4 2.7 2.4 2.1 1.9 --

7 3.7 2.9 2.6 2.2 1.9 --

14 4.0 3.2 2.8 2.4 2.1 --

30 4.4 3.5 3.1 2.7 2.4 --

60 4.9 3.9 3.5 3.1 2.8 --

90 5.4 4.3 3.8 3.4 3.0 --

120 5.8 4.7 4.2 3.8 3.4 --

183 6.4 5.2 4.7 4.3 3.9 --

Magnitude and probability of seasonal low flow from

March-June based on 36 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 4.4 3.4 3.0 2.7 2.5 --

3 4.6 3.5 3.1 2.8 2.6 --

7 4.8 3.7 3.3 3.0 2.7 --

14 5.2 4.0 3.6 3.3 3.0 --

30 7.4 5.1 4.3 3.7 3.3 --

Magnitude and probability of seasonal low flow from

November-February based on 36 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 3.5 2.8 2.5 2.3 2.1 --

3 3.7 3.1 2.8 2.6 2.4 --

7 4.2 3.4 3.1 2.9 2.6 --

14 4.5 3.7 3.3 3.0 2.8 --

30 4.9 4.1 3.8 3.5 3.2 --

Duration of daily mean flows based on 36 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

2.8 3.0 3.6 4.3 5.1 6.0 6.9 7.9

40% 30% 20% 15% 10% 5% 2% 1%

9.9 13 18 22 29 40 53 62

Magnitude and probability of annual high flow

based on 36 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 54 86 109 137 159 --

3 47 72 88 107 120 --

7 43 63 75 89 97 --

15 39 55 64 72 78 --

30 35 48 55 62 66 --

60 29 40 46 52 55 --

90 26 35 40 45 48 --

Magnitude and probability of seasonal low flow from

July-October based on 39 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 4.7 3.1 2.5 2.1 1.8 --

3 4.8 3.2 2.6 2.2 1.9 --

7 4.9 3.3 2.7 2.3 1.9 --

14 5.1 3.5 2.8 2.4 2.1 --

30 5.5 3.8 3.2 2.7 2.4 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 16 2.9 7.0 2.9 39

November 13 3.9 7.4 1.9 36

December 12 4.2 6.4 1.7 36

January 8.9 3.6 5.7 1.3 36

February 15 3.0 6.3 2.2 36

March 29 2.4 9.2 5.3 36

April 41 5.6 19 9.5 38

May 50 5.2 27 13 39

June 65 5.3 29 14 40

July 29 3.2 14 6.5 40

August 17 2.6 9.0 3.9 40

September 16 3.0 7.3 3.2 40

Annual 20 5.8 12 3.6 36
Statistical Summaries of Streamflow 115

06118500 South Fork Musselshell River above Martinsdale, Mont.

Site Number 95

LOCATION.--Lat 46°27'21", long 110°22'54" (NAD 27), in SW1⁄4 NW1⁄4 sec.17, T.8 N., R.11 E., Meagher County, Hydrologic Unit 10040201, on left bank 2 mi 

downstream from Cottonwood Creek, 3 mi west of Martinsdale, and 6 mi upstream from confluence with North Fork.

DRAINAGE AREA.--287 mi2. 

PERIOD OF RECORD.--38 years. October 1941 to Sept. 30, 1979 (discontinued). Monthly discharge only November 1941 to May 1942, published in WSP 1309.

REVISED RECORDS.--WSP 1309: 1942(M), 1944 (M). WSP 1729: Drainage area. WDR MT-75-1: 1948, 1964(M), 1967.

GAGE.--Water-stage recorder. Altitude of gage is 4,900 ft (NGVD 29, by barometer). Prior to May 15, 1942, nonrecording gage at same site and datum.

REMARKS.--Diversions for irrigation of about 6,600 acres of which 250 acres lie downstream from station.

Magnitude and probability of annual low flow

based on 37 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 6.5 2.1 0.98 0.46 0.17 --

3 7.0 2.4 1.1 .52 .19 --

7 8.1 3.0 1.4 .68 .25 --

14 9.4 3.6 1.8 .85 .32 --

30 12 5.2 2.8 1.5 .62 --

60 14 8.3 5.7 4.0 2.5 --

90 17 11 8.1 6.3 4.6 --

120 19 13 10 8.4 6.4 --

183 21 15 12 10 8.2 --

Magnitude and probability of seasonal low flow from

March-June based on 38 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 15 8.8 5.7 3.7 2.1 --

3 15 9.2 6.4 4.4 2.7 --

7 17 9.9 6.9 4.8 3.1 --

14 18 11 8.0 6.2 4.5 --

30 29 16 12 9.0 6.5 --

Magnitude and probability of seasonal low flow from

November-February based on 37 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 11 7.1 5.7 4.6 3.6 --

3 11 7.6 6.1 5.1 4.1 --

7 12 8.3 6.9 5.8 4.8 --

14 13 9.4 7.8 6.7 5.5 --

30 15 11 9.3 7.9 6.5 --

Duration of daily mean flows based on 38 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

2.4 4.7 8.1 11 15 19 23 29

40% 30% 20% 15% 10% 5% 2% 1%

37 56 111 166 262 450 686 855

Magnitude and probability of annual high flow

based on 38 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 694 1,220 1,680 2,430 3,110 --

3 650 1,080 1,420 1,920 2,350 --

7 586 927 1,160 1,460 1,680 --

15 513 796 980 1,200 1,360 --

30 449 687 831 995 1,100 --

60 345 516 611 711 773 --

90 269 400 473 550 597 --

Magnitude and probability of seasonal low flow from

July-October based on 37 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 9.5 2.7 1.1 0.49 0.20 --

3 10 2.9 1.2 .54 .23 --

7 12 3.6 1.6 .71 .29 --

14 13 4.3 1.9 .92 .36 --

30 16 5.8 2.9 1.5 .67 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 95 4.1 31 19 38

November 60 13 28 11 38

December 58 9.4 23 11 38

January 51 7.3 18 8.1 38

February 41 7.8 21 7.3 38

March 106 4.6 35 22 38

April 370 15 113 73 38

May 783 40 334 170 38

June 1,320 67 365 248 38

July 370 5.0 80 67 38

August 82 .91 25 18 38

September 105 .44 23 18 38

Annual 212 23 91 40 38
116 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06120500 Musselshell River at Harlowton, Mont.

Site Number 96

LOCATION.--Lat 46°25'48", long 109°50'24" (NAD 27), in NE1⁄4 sec.28, T.8 N., R.15 E., Wheatland County, Hydrologic Unit 10040201, on left bank 350 ft 

downstream from bridge on U.S. Highway 191, 1.0 mi southwest of Harlowton, 6 mi upstream from American Fork, and at river mile 327.8.

DRAINAGE AREA.--1,125 mi2.

PERIOD OF RECORD.--July 1907 to November 1929, March 1930 to December 1932, April to August 1933, February 1934 to current year (2002). Monthly 

discharge only for some periods, published in WSP 1309.

REVISED RECORDS.--WSP 1309: 1912, 1915(M), 1918, 1925. WSP 1729: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 4,171.46 ft (NGVD 29, levels by Morrison and Maierle, Inc.). Prior to Dec. 8, 1937, nonrecording gages at 

site 1.2 mi downstream at different datums. Dec. 8, 1937, to Aug. 26, 1955, nonrecording gage at bridge 300 ft upstream at different datums.

REMARKS.--Some regulation by Bair (station number 06116500) and Martinsdale (station number 06119000) Reservoirs. Diversions for irrigation of about 

21,900 acres upstream from station of which about 21,400 acres are flood irrigated. U.S. Geological Survey satellite telemeter at station.

Magnitude and probability of annual low flow

based on 90 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 26 4.5 0.00 0.00 0.00 0.00

3 26 4.9 .00 .00 .00 .00

7 30 5.6 .00 .00 .00 .00

14 31 6.4 .30 .00 .00 .00

30 38 7.0 .77 .00 .00 .00

60 45 12 3.3 .15 .00 .00

90 56 15 4.8 1.3 .10 .00

120 62 25 11 4.4 .78 .00

183 63 33 21 14 6.1 .00

Magnitude and probability of seasonal low flow from

March-June based on 93 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 46 19 10 5.7 2.7 1.5

3 49 22 13 7.8 4.1 2.6

7 55 26 16 9.8 5.4 3.4

14 62 31 20 13 7.5 5.1

30 74 41 30 23 17 13

Magnitude and probability of seasonal low flow from

November-February based on 92 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 36 18 10 6.0 2.2 0.00

3 39 20 12 6.9 2.5 .00

7 41 22 14 8.8 3.8 .00

14 42 25 18 13 7.2 .00

30 47 31 24 19 13 .00

Duration of daily mean flows based on 92 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

0.35 0.70 7.9 24 39 51 62 76

40% 30% 20% 15% 10% 5% 2% 1%

92 120 175 238 362 642 1,030 1,360

Magnitude and probability of annual high flow

based on 92 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 982 1,860 2,500 3,310 3,920 4,510

3 904 1,700 2,250 2,930 3,420 3,870

7 786 1,480 1,950 2,520 2,920 3,300

15 658 1,250 1,660 2,170 2,520 2,850

30 540 1,040 1,400 1,840 2,150 2,440

60 406 773 1,030 1,370 1,610 1,840

90 332 613 808 1,050 1,230 1,390

Magnitude and probability of seasonal low flow from

July-October based on 93 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 33 4.7 0.00 0.00 0.00 0.00

3 35 5.2 .00 .00 .00 .00

7 36 5.8 .00 .00 .00 .00

14 37 6.8 .43 .00 .00 .00

30 42 7.4 .96 .00 .00 .00

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 226 0.00 74 46 94

November 176 .00 78 36 94

December 206 .00 67 33 92

January 250 .00 59 31 92

February 190 10 66 32 93

March 500 20 113 84 93

April 632 22 176 130 95

May 1,960 12 406 334 95

June 2,470 28 507 452 95

July 751 .84 161 143 95

August 292 .00 76 66 95

September 290 .00 63 55 95

Annual 483 21 156 86 92
Statistical Summaries of Streamflow 117

06122000 American Fork below Lebo Creek, near Harlowton, Mont.

Site Number 97

LOCATION.--Lat 46°23'34", long 109°45'49" (NAD 27), in SE1⁄4 sec.6, T.7 N., R.16 E., Wheatland County, on left bank 2 mi upstream from mouth, 2 mi 

downstream from Lebo Creek, 5 mi southeast of Harlowton.

DRAINAGE AREA.--166 mi2.

PERIOD OF RECORD.--21 years. July 1946 to September 1967 (discontinued). Monthly discharge only for July 1946, published in WSP 1309.

REVISED RECORDS.--WSP 1116: 1947. WSP 1309: 1948(M), 1950(M). WSP 1629: 1948(P). WSP 1729: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 4,170 ft (NGVD 29, by barometer). 

REMARKS.--Diversions for irrigation of about 7,500 acres, of which 300 acres downstream from station. During irrigation season, natural flow is supplemented 

by release from Lake Lebo (capacity, about 3,000 acre-ft). Diversions from headwaters in T.5 N., R.12 E., to irrigate about 300 acres in Sweet Grass Creek 

drainage in Yellowstone River basin.

Magnitude and probability of annual low flow

based on 20 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1.2 0.22 0.00 0.00 -- --

3 1.6 .35 .00 .00 -- --

7 2.0 .55 .26 .13 -- --

14 2.9 1.0 .56 .33 -- --

30 4.8 2.3 1.6 1.1 -- --

60 6.2 3.7 2.8 2.3 -- --

90 7.7 4.4 3.2 2.4 -- --

120 8.8 5.5 4.2 3.4 -- --

183 11 7.2 6.0 5.2 -- --

Magnitude and probability of seasonal low flow from

March-June based on 21 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 5.8 1.8 0.82 0.39 -- --

3 7.0 2.4 1.1 .54 -- --

7 8.9 3.0 1.4 .68 -- --

14 12 4.1 2.0 .95 -- --

30 17 7.6 4.4 2.6 -- --

Magnitude and probability of seasonal low flow from

November-February based on 21 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 6.4 3.5 2.4 1.8 -- --

3 6.9 4.0 2.9 2.2 -- --

7 7.7 4.6 3.5 2.7 -- --

14 8.5 5.4 4.2 3.4 -- --

30 9.9 6.7 5.4 4.6 -- --

Duration of daily mean flows based on 21 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

0.57 1.2 3.1 4.8 7.4 10 13 16

40% 30% 20% 15% 10% 5% 2% 1%

19 23 30 38 58 121 242 348

Magnitude and probability of annual high flow

based on 21 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 315 572 714 852 -- --

3 276 507 638 770 -- --

7 218 412 532 664 -- --

15 168 325 429 549 -- --

30 125 242 325 428 -- --

60 88 163 219 292 -- --

90 68 120 159 211 -- --

Magnitude and probability of seasonal low flow from

July-October based on 21 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1.7 0.31 0.02 0.00 -- --

3 2.3 .55 .06 .00 -- --

7 2.8 .79 .36 .17 -- --

14 4.0 1.5 .81 .48 -- --

30 5.6 2.8 1.9 1.3 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 39 2.7 13 9.9 21

November 30 5.3 15 6.9 21

December 32 7.5 15 6.4 21

January 24 4.9 13 5.3 21

February 39 5.2 17 7.8 21

March 59 10 23 12 21

April 62 7.7 23 13 21

May 163 4.8 70 48 21

June 548 7.5 130 134 21

July 139 4.3 30 30 22

August 28 2.0 10 7.0 22

September 52 1.7 12 11 22

Annual 71 8.4 31 16 21
118 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06123500 Musselshell River near Ryegate, Mont.

Site Number 98

LOCATION.--Lat 46°18'02", long 109°12'20" (NAD 27), in center of S1⁄2 sec.3, T.6 N., R.20 E., Golden Valley County, Hydrologic Unit 10040201, on 

downstream side of county bridge 2 mi upstream from Careless Creek and 2 mi east of Ryegate.

DRAINAGE AREA.--1,979 mi2 . 

PERIOD OF RECORD.--33 years. July 1946 to Sept. 30, 1979 (discontinued). Monthly discharge only for July 1946, published in WSP 1309.

REVISED RECORDS.--WSP 1729: Drainage area

GAGE.--Nonrecording and crest-stage gage. Altitude of gage is 3,585.26 ft (NGVD 29, levels by U.S. Army Corps of Engineers). Prior to June 23, 1967, waterstage recorder at site 1 mi downstream at different datum.

REMARKS.--Some regulation by Bair (station number 06116500) and Martinsdale (station number 06119000) Reservoirs. Water is diverted on left bank in sec. 8, 

T.7 N., R.17 E., for storage in Deadmans Basin (station number 06122500) Reservoir, and can be returned to the stream by canal at a point about 9 mi upstream 

from station or through Careless Creek 2 mi downstream from station. Diversions for irrigation of about 45,000 acres upstream from station, of which 

2,700 acres is flood irrigated.

Magnitude and probability of annual low flow

based on 32 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 13 6.5 4.4 3.2 2.2 --

3 15 7.3 4.9 3.5 2.3 --

7 17 8.2 5.4 3.8 2.5 --

14 19 9.1 6.0 4.1 2.7 --

30 25 12 7.4 5.0 3.2 --

60 33 16 11 7.8 5.3 --

90 40 20 14 10 7.2 --

120 44 24 17 13 9.1 --

183 58 31 22 16 11 --

Magnitude and probability of seasonal low flow from

March-June based on 33 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 35 17 11 8.0 5.4 --

3 38 18 12 9.0 6.2 --

7 42 21 14 10 7.1 --

14 49 24 16 12 8.9 --

30 71 32 21 15 10 --

Magnitude and probability of seasonal low flow from

November-February based on 33 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 16 7.5 5.1 3.8 2.7 --

3 18 8.4 5.8 4.3 3.1 --

7 20 9.5 6.5 4.8 3.4 --

14 23 11 7.6 5.5 3.8 --

30 33 16 11 7.9 5.4 --

Duration of daily mean flows based on 33 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

5.8 7.9 13 20 33 45 63 87

40% 30% 20% 15% 10% 5% 2% 1%

116 153 208 269 433 744 1,290 1,810

Magnitude and probability of annual high flow

based on 33 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 1,210 2,700 4,040 6,110 7,930 --

3 1,100 2,370 3,470 5,130 6,540 --

7 943 2,000 2,890 4,170 5,230 --

15 772 1,620 2,310 3,320 4,150 --

30 628 1,280 1,810 2,580 3,220 --

60 458 910 1,290 1,850 2,330 --

90 376 716 995 1,410 1,750 --

Magnitude and probability of seasonal low flow from

July-October based on 33 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 23 9.3 5.1 3.4 2.3 --

3 24 9.9 5.4 3.8 2.5 --

7 26 11 5.8 4.1 2.6 --

14 38 11 6.4 4.5 2.8 --

30 40 16 8.6 5.7 4.0 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 193 3.1 60 47 33

November 189 11 67 45 33

December 255 8.7 67 57 33

January 175 6.6 56 38 33

February 217 8.8 76 49 33

March 620 17 162 155 33

April 626 18 175 172 33

May 1,820 46 442 404 33

June 3,430 76 673 725 33

July 1,390 70 252 258 34

August 346 4.0 128 67 34

September 288 5.2 87 64 34

Annual 568 35 188 119 33
Statistical Summaries of Streamflow 119

06125700 Big Coulee near Lavina, Mont.

Site Number 99

LOCATION.--Lat 46°15'53", long 108°56'50" (NAD 27), SE1⁄4 sec.15, T.6 N., R.22 E., Golden Valley County, on left bank 2 mi upstream from mouth and 2 mi 

southwest of Lavina.

DRAINAGE AREA.--232 mi2. 

PERIOD OF RECORD.--14 years. August 1957 to June 1972 (discontinued).

GAGE.--Water-stage recorder. Altitude of gage is 3,480 ft (NGVD 29, from topographic map).

REMARKS.--Minor flood irrigation in headwaters.

Magnitude and probability of annual low flow

based on 14 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.29 0.00 0.00 0.00 -- --

3 .32 .00 .00 .00 -- --

7 .37 .00 .00 .00 -- --

14 .45 .00 .00 .00 -- --

30 .58 .16 .08 .04 -- --

60 .94 .34 .20 .12 -- --

90 1.2 .44 .27 .18 -- --

120 1.3 .52 .34 .24 -- --

183 1.4 .62 .41 .29 -- --

Magnitude and probability of seasonal low flow from

March-June based on 15 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1.4 0.55 0.31 0.18 -- --

3 1.6 .60 .33 .19 -- --

7 1.7 .68 .40 .25 -- --

14 1.9 .76 .45 .28 -- --

30 2.4 1.3 .91 .69 -- --

Magnitude and probability of seasonal low flow from

November-February based on 15 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.40 0.00 0.00 0.00 -- --

3 .43 .00 .00 .00 -- --

7 .49 .00 .00 .00 -- --

14 .62 .00 .00 .00 -- --

30 .73 .19 .09 .04 -- --

Duration of daily mean flows based on 14 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

0.04 0.08 0.20 0.40 0.80 1.2 1.7 2.5

40% 30% 20% 15% 10% 5% 2% 1%

3.6 5.2 8.0 10 13 21 45 81

Magnitude and probability of annual high flow

based on 14 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 55 195 383 795 -- --

3 42 153 295 584 -- --

7 34 118 217 401 -- --

15 24 84 157 302 -- --

30 17 57 105 202 -- --

60 12 37 65 118 -- --

90 9.9 28 48 85 -- --

Magnitude and probability of seasonal low flow from

July-October based on 14 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1.1 0.46 0.30 0.21 -- --

3 1.2 .47 .30 .21 -- --

7 1.2 .50 .33 .23 -- --

14 1.2 .54 .37 .28 -- --

30 1.3 .59 .41 .32 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 9.7 0.51 3.1 3.2 15

November 9.0 .22 3.1 3.0 15

December 7.2 .30 2.4 2.4 15

January 6.4 .07 1.9 2.0 15

February 17 .12 4.2 5.3 15

March 54 .76 12 14 15

April 14 .66 6.4 4.2 15

May 63 .79 9.7 15 15

June 297 .75 31 75 15

July 32 .65 7.9 9.6 14

August 14 .41 3.8 4.4 15

September 9.0 .41 3.0 3.1 15

Annual 31 .57 7.4 8.1 14
120 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06126470 Halfbreed Creek near Klein, Mont.

Site Number 100

LOCATION.--Lat 46°23'14", long 108°32'29" (NAD 27), in SW1⁄4NE1⁄4SW1⁄4 sec.1, T.7 N., R.25 E., Musselshell County, Hydrologic Unit 10040201, on left bank, 

800 ft upstream from private road bridge, 1.2 mi south of Klein, 3.2 mi upstream from mouth, and 4.1 mi south of Roundup. 

DRAINAGE AREA.--53.2 mi2. 

PERIOD OF RECORD.--October 1977 to September 1986, July 1987 to 1991 (discontinued). 

REVISED RECORDS.--The maximum discharge for water year 1990 has been revised to 37 ft3/s, Aug. 20, 1990, gage height, 5.57 ft.

GAGE.--Water-stage recorder. Altitude of gage is 3,330 ft (NGVD 29, from topographic map). 

Magnitude and probability of annual low flow

based on 11 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.16 0.01 0.00 0.00 -- --

3 .19 .01 .00 .00 -- --

7 .19 .03 .00 .00 -- --

14 .20 .03 .01 .00 -- --

30 .27 .08 .04 .02 -- --

60 .34 .13 .08 .05 -- --

90 .41 .19 .12 .09 -- --

120 .51 .25 .18 .13 -- --

183 .54 .28 .20 .15 -- --

Magnitude and probability of seasonal low flow from

March-June based on 13 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.38 0.18 0.12 0.09 -- --

3 .41 .20 .14 .10 -- --

7 .49 .26 .19 .15 -- --

14 .59 .34 .25 .20 -- --

30 .71 .44 .33 .26 -- --

Magnitude and probability of seasonal low flow from

November-February based on 12 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.22 0.07 0.00 0.00 -- --

3 .26 .09 .00 .00 -- --

7 .33 .10 .01 .00 -- --

14 .34 .11 .01 .00 -- --

30 .41 .14 .07 .04 -- --

Duration of daily mean flows based on 13 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

0.02 0.03 0.08 0.16 0.31 0.47 0.63 0.79

40% 30% 20% 15% 10% 5% 2% 1%

0.94 1.1 1.4 1.6 1.8 2.0 2.6 3.3

Magnitude and probability of annual high flow

based on 13 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 6.4 17 30 60 -- --

3 4.5 9.7 16 27 -- --

7 3.1 5.6 8.1 12 -- --

15 2.1 3.5 4.8 7.0 -- --

30 1.6 2.6 3.4 4.7 -- --

60 1.4 2.1 2.6 3.4 -- --

90 1.3 1.9 2.3 2.8 -- --

Magnitude and probability of seasonal low flow from

July-October based on 12 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.20 0.06 0.03 0.02 -- --

3 .22 .07 .04 .02 -- --

7 .24 .08 .05 .03 -- --

14 .28 .10 .06 .04 -- --

30 .31 .12 .07 .05 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 1.5 0.29 0.87 0.44 13

November 1.6 .22 .78 .49 13

December 1.6 .13 .72 .53 13

January 1.4 .05 .69 .44 13

February 2.0 .16 .96 .54 13

March 2.5 .58 1.3 .57 13

April 2.1 .61 1.1 .44 13

May 4.9 .47 1.4 1.2 13

June 1.9 .27 1.0 .61 13

July 2.0 .12 .72 .61 14

August 1.4 .06 .58 .43 14

September 1.5 .16 .62 .48 14

Annual 1.6 .36 .91 .46 13
Statistical Summaries of Streamflow 121

06126500 Musselshell River near Roundup, Mont.

Site Number 101

LOCATION.--Lat 46°25'41", long 108°34'19" (NAD 27), in NW1⁄4SE1⁄4SE1⁄4 sec.22, T.8 N., R.25 E., Musselshell County, Hydrologic Unit 10040202, on left bank 

20 ft downstream from Halfbreed Creek, 0.1 mi upstream from bridge on U.S. Highway 87, 2.0 mi southwest of Roundup, and at river mile 211.6.

DRAINAGE AREA.--4,023 mi2.

PERIOD OF RECORD.--May 1946 to current year (2002). Monthly discharge only from October 1947 to September 1949, published in WSP 1309.

REVISED RECORDS.--WSP 1086: 1946. WSP 1729: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 3,188.15 ft (NGVD 29, levels by U.S. Army Corps of Engineers). Prior to Sept. 26, 1949, nonrecording gage 

at present site and datum.

REMARKS.--Some regulation by Bair (station number 06116500), Martinsdale (station number 06119000) and Deadmans Basin (station number 06122500) 

Reservoirs. Diversions for irrigation of about 39,100 acres upstream from station, of which about 35,900 acres are flood irrigated. U.S. Army Corps of 

Engineers satellite telemeter at station.

Magnitude and probability of annual low flow

based on 55 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 16 4.3 1.8 0.77 0.27 0.12

3 19 5.3 2.2 1.0 .35 .17

7 22 6.8 3.2 1.6 .64 .33

14 26 9.1 4.7 2.6 1.2 .69

30 35 13 6.8 3.7 1.7 .95

60 43 17 9.5 5.4 2.6 1.5

90 50 21 12 7.2 3.7 2.3

120 55 24 14 8.8 4.8 3.1

183 75 33 19 11 5.9 3.7

Magnitude and probability of seasonal low flow from

March-June based on 56 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 36 8.5 3.3 1.3 0.43 0.19

3 41 10 4.1 1.7 .56 .25

7 47 13 5.7 2.6 .95 .46

14 61 20 9.8 5.0 2.2 1.2

30 87 31 16 9.1 4.5 2.7

Magnitude and probability of seasonal low flow from

November-February based on 56 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 21 7.7 4.1 2.3 1.1 0.66

3 23 8.8 4.8 2.8 1.4 .87

7 26 10 5.8 3.5 1.9 1.2

14 30 12 7.2 4.4 2.5 1.6

30 37 16 9.6 6.2 3.6 2.5

Duration of daily mean flows based on 56 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

2.2 4.1 9.7 21 36 52 73 101

40% 30% 20% 15% 10% 5% 2% 1%

138 181 250 315 450 755 1,400 1,940

Magnitude and probability of annual high flow

based on 56 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 1,180 2,580 3,860 5,890 7,720 9,820

3 1,030 2,290 3,470 5,400 7,170 9,250

7 865 1,930 2,940 4,620 6,180 8,040

15 690 1,540 2,380 3,820 5,200 6,890

30 556 1,230 1,880 2,980 4,030 5,310

60 426 898 1,330 2,040 2,680 3,440

90 368 749 1,080 1,590 2,030 2,530

Magnitude and probability of seasonal low flow from

July-October based on 56 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 37 9.4 3.4 1.3 0.36 0.14

3 40 11 4.1 1.6 .47 .19

7 43 13 5.3 2.3 .78 .35

14 47 15 6.9 3.3 1.3 .68

30 62 22 11 5.2 2.1 1.0

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 335 1.4 79 64 56

November 242 4.0 75 53 56

December 283 3.7 68 57 56

January 222 5.3 65 51 56

February 414 5.8 96 80 56

March 1,280 6.8 198 241 56

April 788 1.8 184 195 56

May 1,810 30 421 407 56

June 4,320 37 665 783 57

July 1,310 14 296 270 57

August 563 2.1 189 114 57

September 504 .01 127 97 57

Annual 608 18 207 140 56
122 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06127500 Musselshell River at Musselshell, Mont.

Site Number 102

LOCATION.--Lat 46°31'23", long 108°06'30" (NAD 27), in SE1⁄4SW1⁄4SW1⁄4 sec.20, T.9 N., R.29 E., Musselshell County, Hydrologic Unit 10040202, on left bank 

0.9 mi upstream from Hawk Creek, 1 mi west of Musselshell, and at river mile 164.5.

DRAINAGE AREA.--4,568 mi2.

PERIOD OF RECORD.--August 1928 to September 1932 (no records December to February for the water years 1930-31), August 1945 to September 1979, 

October 1982 to September 1983, October 1983 to current season (2002, seasonal records only). Monthly discharge only for some periods, published in 

WSP 1309.

REVISED RECORDS.--WSP 1729: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 2,984.72 ft (NGVD 29, levels by U.S. Army Corps of Engineers). Prior to Oct. 8, 1949, nonrecording gage at 

site 1 mi downstream at different datums.

REMARKS.--Some regulation by Bair (station number 06116500), Martinsdale (station number 06119000), and Deadmans Basin (station number 06122500) 

Reservoirs. Diversions for irrigation of about 44,600 acres upstream from station, of which about 39,400 acres is flood irrigated. U.S. Geological Survey 

satellite telemeter at station. 

Magnitude and probability of annual low flow

based on 34 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 16 4.5 0.84 0.00 0.00 --

3 18 5.1 .99 .00 .00 --

7 20 5.9 1.2 .00 .00 --

14 24 7.3 1.6 .00 .00 --

30 32 11 3.7 .00 .00 --

60 42 20 13 6.7 .00 --

90 49 25 17 11 .00 --

120 54 28 19 13 .00 --

183 71 37 24 15 .00 --

Magnitude and probability of seasonal low flow from

March-June based on 39 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 58 13 2.6 0.00 0.00 --

3 63 14 2.9 .00 .00 --

7 75 14 3.0 .44 .00 --

14 93 15 3.4 .70 .08 --

30 144 32 9.3 2.6 .44 --

Magnitude and probability of seasonal low flow from

November-February based on 37 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 22 10 6.8 4.4 0.00 --

3 24 12 7.7 5.0 .00 --

7 27 13 8.5 5.5 .00 --

14 32 15 9.8 6.2 .00 --

30 41 21 14 9.1 .00 --

Duration of daily mean flows based on 37 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

0.25 0.50 2.7 15 35 52 73 99

40% 30% 20% 15% 10% 5% 2% 1%

130 172 240 305 445 769 1,390 1,960

Magnitude and probability of annual high flow

based on 37 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 1,430 3,030 4,430 6,570 8,430 --

3 1,220 2,630 3,900 5,890 7,660 --

7 1,030 2,230 3,280 4,900 6,320 --

15 820 1,750 2,560 3,810 4,910 --

30 634 1,310 1,890 2,780 3,550 --

60 468 938 1,340 1,960 2,500 --

90 394 771 1,090 1,570 1,980 --

Magnitude and probability of seasonal low flow from

July-October based on 55 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 25 4.7 0.94 0.00 0.00 0.00

3 28 5.5 1.1 .00 .00 .00

7 31 6.3 1.4 .00 .00 .00

14 35 7.7 1.8 .00 .00 .00

30 61 12 4.0 .00 .00 .00

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 328 0.00 77 67 58

November 236 .00 76 55 39

December 268 .00 77 60 37

January 222 .00 71 49 37

February 460 .04 108 87 37

March 1,360 13 273 306 39

April 859 1.2 191 206 58

May 1,670 .36 356 374 58

June 4,220 .49 579 759 58

July 1,380 .00 238 276 58

August 534 .00 140 106 59

September 478 .00 107 94 60

Annual 609 34 215 138 37
Statistical Summaries of Streamflow 123

06127900 Flatwillow Creek near Flatwillow, Mont.

Site Number 103

LOCATION.--Lat 46°47',28" long 108°36'51" (NAD 27), in NE1⁄4 sec.19, T.12 N., R.25 E., Petroleum County, 10 mi southwest of Flatwillow and 14 mi upstream 

from Pike Creek.

DRAINAGE AREA.--188 mi2 (revised). 

PERIOD OF RECORD.--19 years (1911-30). May 1911 to September 1932, February 1934 to September 1956 (discontinued). Monthly discharge only for some 

periods, published in WSP 1309.

GAGE.--Wire-weight gage and masonry control. Altitude of gage is 3,560 ft (NGVD 29, by barometer). Prior to Apr. 17, 1918, staff gage at site 5 mi downstream 

at different datum. Apr. 17, 1918, to Apr. 15, 1925, staff gage at present site at different datum. Apr. 16, 1925, to Sept. 30, 1932, wire-weight gage at site 

300 ft upstream at different datum.

REMARKS.--Diversions for irrigation of 9,000 acres upstream from station.

Magnitude and probability of annual low flow

based on 42 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.00 0.00 0.00 0.00 0.00 --

3 .00 .00 .00 .00 .00 --

7 .00 .00 .00 .00 .00 --

14 .00 .00 .00 .00 .00 --

30 .42 .00 .00 .00 .00 --

60 1.3 .00 .00 .00 .00 --

90 2.0 .00 .00 .00 .00 --

120 4.6 .14 .00 .00 .00 --

183 6.4 .96 .00 .00 .00 --

Magnitude and probability of seasonal low flow from

March-June based on 44 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 4.1 0.00 0.00 0.00 0.00 --

3 4.9 .00 .00 .00 .00 --

7 6.1 .00 .00 .00 .00 --

14 7.4 .40 .00 .00 .00 --

30 14 .56 .00 .00 .00 --

Magnitude and probability of seasonal low flow from

November-February based on 43 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 5.0 0.00 0.00 0.00 0.00 --

3 5.3 .00 .00 .00 .00 --

7 5.4 .00 .00 .00 .00 --

14 6.7 .11 .00 .00 .00 --

30 7.1 .98 .00 .00 .00 --

Duration of daily mean flows based on 43 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

0.04 0.09 0.22 0.43 0.87 3.4 7.1 13

40% 30% 20% 15% 10% 5% 2% 1%

19 27 40 51 66 114 185 257

Magnitude and probability of annual high flow

based on 43 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 141 289 414 599 758 --

3 119 254 376 570 746 --

7 102 229 347 540 720 --

15 90 205 310 476 625 --

30 73 172 263 406 531 --

60 57 135 204 307 396 --

90 48 113 168 250 317 --

Magnitude and probability of seasonal low flow from

July-October based on 43 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.00 0.00 0.00 0.00 0.00 --

3 .00 .00 .00 .00 .00 --

7 .28 .00 .00 .00 .00 --

14 .57 .00 .00 .00 .00 --

30 .89 .00 .00 .00 .00 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 52 0.00 14 15 43

November 51 .00 15 15 43

December 45 .00 13 13 43

January 41 .00 12 11 43

February 53 .00 14 13 44

March 79 .00 24 20 44

April 163 .00 44 43 44

May 495 .00 63 90 45

June 674 .00 81 115 45

July 130 .00 34 36 45

August 122 .00 14 22 45

September 58 .00 10 14 45

Annual 134 .00 28 26 43
124 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06128200 Flatwillow Creek near Winnett, Mont.

Site Number 104

LOCATION.--Lat 46°56'18", long 108°11'52" (NAD 27), in NW1⁄4NE1⁄4 sec.32, T.14 N., R.28 E., Petroleum County, 8 mi upstream from Box Elder Creek and 

8.5 mi southeast of Winnett.

DRAINAGE AREA.--642 mi2 (revised). At site used 1921-32 (at Petrolia) 660 mi2.

PERIOD OF RECORD.--11 years. June 1921 to November 1929, March to December 1930, February to December 1931, March to September 1932, April 1948 

to October 1951 (discontinued). Monthly discharge only for some periods, published in WSP 1309. Published as "at Petrolia" 1931-32.

GAGE.--Water-stage recorder. Altitude of gage is 2,790 ft (NGVD 29, by barometer). June 11, 1921, to September 1932, staff or chain gage at site 6 mi 

downstream at datum about 90 ft lower.

REMARKS.--Diversions for irrigation of about 13,000 acres upstream from station. Storage in Petrolia Reservoir, 3 mi upstream, began in July 1951.

Magnitude and probability of annual low flow

based on 5 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 -- -- -- -- -- --

3 -- -- -- -- -- --

7 -- -- -- -- -- --

14 -- -- -- -- -- --

30 -- -- -- -- -- --

60 -- -- -- -- -- --

90 -- -- -- -- -- --

120 -- -- -- -- -- --

183 -- -- -- -- -- --

Magnitude and probability of seasonal low flow from

March-June based on 11 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.94 0.00 0.00 0.00 -- --

3 1.3 .00 .00 .00 -- --

7 1.7 .00 .00 .00 -- --

14 2.8 .00 .00 .00 -- --

30 6.4 .00 .00 .00 -- --

Magnitude and probability of seasonal low flow from

November-February based on 10 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 6.1 0.00 0.00 0.00 -- --

3 8.4 .00 .00 .00 -- --

7 9.2 .00 .00 .00 -- --

14 9.8 .00 .00 .00 -- --

30 9.9 .60 .01 .00 -- --

Duration of daily mean flows based on 11 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

0.03 0.06 0.15 0.31 0.62 0.93 4.2 8.8

40% 30% 20% 15% 10% 5% 2% 1%

17 28 47 62 85 156 261 474

Magnitude and probability of annual high flow

based on 11 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 340 1,050 1,990 -- -- --

3 249 845 1,720 -- -- --

7 175 573 1,130 -- -- --

15 138 442 854 -- -- --

30 113 336 610 -- -- --

60 82 234 412 -- -- --

90 67 188 325 -- -- --

Magnitude and probability of seasonal low flow from

July-October based on 6 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 -- -- -- -- -- --

3 -- -- -- -- -- --

7 -- -- -- -- -- --

14 -- -- -- -- -- --

30 -- -- -- -- -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 193 0.52 39 59 11

November 70 .15 20 19 12

December 50 2.5 19 15 11

January 41 3.1 17 13 11

February 35 1.5 16 11 11

March 145 8.0 59 41 13

April 203 1.5 46 51 14

May 448 .69 88 129 14

June 480 2.6 157 168 14

July 510 .30 71 127 15

August 126 .28 21 38 11

September 66 .60 16 20 11

Annual 117 8.8 49 42 11
Statistical Summaries of Streamflow 125

06129000 Box Elder Creek near Winnett, Mont.

Site Number 105

LOCATION.--Lat 47°00'45", long 108°09'30" (NAD 27), SW1⁄4 sec.34, T.15 N., R.28 E., Petroleum County, on right bank 500 ft upstream from bridge on State 

Highway 20, 0.4 mi upstream from McDonald Creek, 7 mi upstream from mouth, and 9 mi east of Winnett.

DRAINAGE AREA.--684 mi2. 

PERIOD OF RECORD.--17 years. June 1930 to December 1932, February 1934 to September 1936, April to August 1937, March to September 1938, August 

1958 to June 1972 (discontinued). Monthly discharge only for some periods, published in WSP 1309.

GAGE.--Water-stage recorder. Altitude of gage is 2,720 ft (NGVD 29, by barometer). Prior to Aug. 22, 1958, nonrecording gages 1,500 ft downstream at different 

datums.

REMARKS.--Minor diversions for storage and irrigation.

Magnitude and probability of annual low flow

based on 16 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.00 0.00 0.00 0.00 -- --

3 .00 .00 .00 .00 -- --

7 .00 .00 .00 .00 -- --

14 .00 .00 .00 .00 -- --

30 .00 .00 .00 .00 -- --

60 .00 .00 .00 .00 -- --

90 .00 .00 .00 .00 -- --

120 .00 .00 .00 .00 -- --

183 .06 .00 .00 .00 -- --

Magnitude and probability of seasonal low flow from

March-June based on 19 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.00 0.00 0.00 0.00 -- --

3 .00 .00 .00 .00 -- --

7 .00 .00 .00 .00 -- --

14 .00 .00 .00 .00 -- --

30 .44 .00 .00 .00 -- --

Magnitude and probability of seasonal low flow from

November-February based on 18 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.00 0.00 0.00 0.00 -- --

3 .00 .00 .00 .00 -- --

7 .00 .00 .00 .00 -- --

14 .00 .00 .00 .00 -- --

30 .00 .00 .00 .00 -- --

Duration of daily mean flows based on 17 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

0.01 0.03 0.07 0.14 0.29 0.43 0.58 0.72

40% 30% 20% 15% 10% 5% 2% 1%

0.87 1.1 4.6 9.6 25 81 282 517

Magnitude and probability of annual high flow

based on 17 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 976 2,350 3,040 3,570 -- --

3 722 1,740 2,260 2,680 -- --

7 469 1,120 1,450 1,730 -- --

15 273 663 881 1,080 -- --

30 166 382 493 585 -- --

60 101 227 287 332 -- --

90 71 159 201 232 -- --

Magnitude and probability of seasonal low flow from

July-October based on 19 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.00 0.00 0.00 0.00 -- --

3 .00 .00 .00 .00 -- --

7 .00 .00 .00 .00 -- --

14 .00 .00 .00 .00 -- --

30 .00 .00 .00 .00 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 7.0 0.00 0.42 1.6 19

November 1.1 .00 .16 .27 19

December 1.9 .00 .24 .46 19

January 2.5 .00 .34 .70 18

February 206 .00 20 51 18

March 184 .00 51 61 19

April 134 .00 14 29 20

May 513 .00 57 119 21

June 624 .00 100 171 22

July 170 .00 23 45 21

August 19 .00 3.2 5.9 20

September 12 .00 .83 2.7 20

Annual 60 .18 23 19 17
126 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06129500 McDonald Creek at Winnett, Mont.

Site Number 106

LOCATION.--Lat 47°00'00", long 108°21'00" (NAD 27), in NE1⁄4 sec.6, T.14 N., R.27 E., Petroleum County, at Winnett, about 12 mi upstream from mouth.

DRAINAGE AREA.--421 mi2 (revised). 

PERIOD OF RECORD.--15 years. April 1930 to December 1931, March to December 1932, February 1934 to September 1945, February 1953 to September 

1956, water years 1957-58 (annual maximum). Monthly discharge only for some periods, published in WSP 1309.

GAGE.--Crest-stage gage since Oct. 1, 1956. Altitude of gage is 2,930 ft (NGVD 29, by barometer). Apr. 18, 1930, to Dec. 5, 1932, and Feb. 4, 1934, to Sept. 30, 

1945, wire-weight gage at sites within 1 mi of present site at different datums. Feb. 1, 1953, to Sept. 30, 1956, wire-weight gage at same site and datum.

REMARKS.--Small reservoirs in headwaters. Diversions for irrigation of several thousand acres upstream from station.

Magnitude and probability of annual low flow

based on 14 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.00 0.00 0.00 0.00 -- --

3 .00 .00 .00 .00 -- --

7 .00 .00 .00 .00 -- --

14 .00 .00 .00 .00 -- --

30 .00 .00 .00 .00 -- --

60 .01 .00 .00 .00 -- --

90 .03 .00 .00 .00 -- --

120 .19 .01 .00 .00 -- --

183 .29 .02 .00 .00 -- --

Magnitude and probability of seasonal low flow from

March-June based on 17 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.00 0.00 0.00 0.00 -- --

3 .00 .00 .00 .00 -- --

7 .04 .00 .00 .00 -- --

14 .12 .00 .00 .00 -- --

30 .28 .02 .00 .00 -- --

Magnitude and probability of seasonal low flow from

November-February based on 15 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.00 0.00 0.00 0.00 -- --

3 .00 .00 .00 .00 -- --

7 .00 .00 .00 .00 -- --

14 .01 .00 .00 .00 -- --

30 .03 .00 .00 .00 -- --

Duration of daily mean flows based on 15 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

0.02 0.03 0.08 0.15 0.31 0.46 0.61 0.77

40% 30% 20% 15% 10% 5% 2% 1%

0.92 2.5 8.5 13 21 56 159 278

Magnitude and probability of annual high flow

based on 15 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 169 421 609 839 -- --

3 124 346 545 837 -- --

7 77 245 434 781 -- --

15 46 168 339 732 -- --

30 28 108 233 552 -- --

60 17 64 142 347 -- --

90 12 46 101 253 -- --

Magnitude and probability of seasonal low flow from

July-October based on 17 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.00 0.00 0.00 0.00 -- --

3 .00 .00 .00 .00 -- --

7 .00 .00 .00 .00 -- --

14 .00 .00 .00 .00 -- --

30 .00 .00 .00 .00 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 9.1 0.00 1.8 3.2 17

November 15 .00 2.6 4.7 17

December 11 .00 2.5 4.4 16

January 10 .00 2.2 3.8 15

February 65 .00 6.6 16 16

March 45 .01 10 13 17

April 52 .01 11 17 18

May 227 .01 19 52 19

June 306 .00 67 104 19

July 104 .00 19 31 19

August 29 .00 3.5 7.8 19

September 12 .00 2.2 4.4 19

Annual 57 .57 13 20 15
Statistical Summaries of Streamflow 127

06130500 Musselshell River at Mosby, Mont.

Site Number 107

LOCATION.--Lat 46°59'41", long 107°53'18" (NAD 27), in SW1⁄4NW1⁄4NW1⁄4 sec.11, T.14 N., R.30 E., Petroleum County, Hydrologic Unit 10040205, on right 

bank, downstream side of bridge on State Highway 20, 0.3 mi west of Mosby, 10.9 mi downstream from Flatwillow Creek, and at river mile 60.0.

DRAINAGE AREA.--7,846 mi2.

PERIOD OF RECORD.--May to November 1929, March 1930 to September 1932, February 1934 to current year (2002). Monthly discharge only for some 

periods, published in WSP 1309.

REVISED RECORDS.--WSP 1559: 1935-36. WSP 1729: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 2,493.23 ft (NGVD 29). Dec. 6, 1962, to Mar. 14, 1966, water-stage recorder at site 900 ft downstream at 

different datum. Mar. 15, 1966, to Dec. 11, 1973, water-stage recorder and nonrecording gages at site 400 ft downstream at same datum. Dec. 12, 1973, to 

Oct. 1, 1981, nonrecording gage at site 400 ft downstream at same datum. Oct. 1, 1981, to July 25, 1995, water-stage recorder at site 400 ft upstream from 

bridge at datum 2.67 ft higher. See WSP 2116 for history of changes prior to 1962.

REMARKS.--Some regulation by Bair (station number 06116500), Martinsdale (station number 06119000) and Deadmans Basin (station number 06122500) 

Reservoirs. Diversions for irrigation of about 47,000 acres upstream from station. U.S. Geological Survey satellite telemeter at station.

Magnitude and probability of annual low flow

based on 70 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1.8 0.00 0.00 0.00 0.00 0.00

3 2.3 .00 .00 .00 .00 .00

7 3.6 .00 .00 .00 .00 .00

14 6.2 .00 .00 .00 .00 .00

30 19 .11 .00 .00 .00 .00

60 45 6.3 .31 .00 .00 .00

90 45 6.3 .31 .00 .00 .00

120 67 8.4 .43 .00 .00 .00

183 84 10 .79 .00 .00 .00

Magnitude and probability of seasonal low flow from

March-June based on 72 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 25 0.51 0.00 0.00 0.00 0.00

3 30 1.3 .00 .00 .00 .00

7 36 2.6 .00 .00 .00 .00

14 62 4.6 .19 .00 .00 .00

30 91 14 2.8 .15 .00 .00

Magnitude and probability of seasonal low flow from

November-February based on 70 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 18 1.6 0.00 0.00 0.00 0.00

3 21 1.9 .00 .00 .00 .00

7 25 2.8 .00 .00 .00 .00

14 37 2.9 .00 .00 .00 .00

30 51 5.7 .00 .00 .00 .00

Duration of daily mean flows based on 70 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

0.08 0.17 0.42 0.84 17 38 59 84

40% 30% 20% 15% 10% 5% 2% 1%

118 169 262 365 585 1,130 2,210 3,390

Magnitude and probability of annual high flow

based on 70 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 2,890 6,530 9,490 13,600 16,800 20,100

3 2,240 5,200 7,660 11,100 13,900 16,700

7 1,690 4,060 6,050 8,900 11,200 13,500

15 1,250 3,070 4,620 6,840 8,630 10,500

30 893 2,190 3,310 4,950 6,280 7,680

60 605 1,490 2,270 3,440 4,400 5,420

90 481 1,180 1,790 2,690 3,420 4,200

Magnitude and probability of seasonal low flow from

July-October based on 71 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 2.1 0.00 0.00 0.00 0.00 0.00

3 2.7 .00 .00 .00 .00 .00

7 4.2 .00 .00 .00 .00 .00

14 7.2 .00 .00 .00 .00 .00

30 24 .15 .00 .00 .00 .00

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 478 0.00 80 85 71

November 337 .00 79 70 71

December 278 .00 72 63 70

January 376 .00 78 79 70

February 1,860 .00 175 282 71

March 4,660 .00 458 785 72

April 1,920 3.1 290 357 72

May 3,770 .00 522 703 73

June 4,970 1.9 863 1,030 73

July 2,150 .00 316 473 73

August 870 .00 113 136 73

September 787 .00 111 151 73

Annual 1,090 8.1 268 231 70
128 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06131000 Big Dry Creek near Van Norman, Mont.

Site Number 108

LOCATION.--Lat 47°20'58", long 106°21'26" (NAD 27), in NE1⁄4SW1⁄4NW1⁄4 sec.3, T.18 N., R.42 E., Garfield County, Hydrologic Unit 10040105, on left bank 

900 ft downstream from Little Dry Creek, 3.2 mi northeast of Van Norman Post Office, 26 mi east of Jordan, and at river mile 55.1.

DRAINAGE AREA.--2,554 mi2.

PERIOD OF RECORD.--October 1939 to July 1969, July 1970 to current year (2002; discharge measurements only, October 1947 to March 1949). Prior to July 

1970, published as "Dry Creek near Van Norman."

REVISED RECORDS.--WSP 1309: 1947(M). WSP 1559: 1944(M), 1947. WSP 1729: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 2,330 ft (NGVD 29). Prior to July 24, 1978, at site 400 ft upstream at same datum.

REMARKS.--Minor diversions for irrigation upstream from station. U.S. Army Corps of Engineers satellite telemeter at station. 

Magnitude and probability of annual low flow

based on 57 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.00 0.00 0.00 0.00 0.00 0.00

3 .00 .00 .00 .00 .00 .00

7 .00 .00 .00 .00 .00 .00

14 .00 .00 .00 .00 .00 .00

30 .00 .00 .00 .00 .00 .00

60 .27 .01 .00 .00 .00 .00

90 1.0 .17 .04 .00 .00 .00

120 1.3 .45 .22 .09 .00 .00

183 2.3 .61 .27 .12 .05 .03

Magnitude and probability of seasonal low flow from

March-June based on 60 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.31 0.00 0.00 0.00 0.00 0.00

3 .49 .00 .00 .00 .00 .00

7 .88 .00 .00 .00 .00 .00

14 1.5 .25 .06 .00 .00 .00

30 3.4 1.1 .58 .32 .16 .10

Magnitude and probability of seasonal low flow from

November-February based on 59 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.00 0.00 0.00 0.00 0.00 0.00

3 .00 .00 .00 .00 .00 .00

7 .00 .00 .00 .00 .00 .00

14 .00 .00 .00 .00 .00 .00

30 .01 .00 .00 .00 .00 .00

Duration of daily mean flows based on 59 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

0.03 0.06 0.15 0.31 0.61 0.92 1.6 2.6

40% 30% 20% 15% 10% 5% 2% 1%

4.1 6.9 14 22 44 122 444 940

Magnitude and probability of annual high flow

based on 59 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 1,360 4,760 8,510 15,000 21,100 28,100

3 942 3,350 6,100 11,100 15,900 21,600

7 567 1,970 3,560 6,430 9,210 12,500

15 332 1,100 1,950 3,440 4,850 6,530

30 198 638 1,120 1,970 2,780 3,740

60 115 363 633 1,110 1,570 2,110

90 83 254 437 757 1,060 1,430

Magnitude and probability of seasonal low flow from

July-October based on 59 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.03 0.00 0.00 0.00 0.00 0.00

3 .08 .00 .00 .00 .00 .00

7 .11 .00 .00 .00 .00 .00

14 .16 .00 .00 .00 .00 .00

30 .31 .00 .00 .00 .00 .00

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 98 0.00 6.4 14 60

November 14 .00 3.0 3.1 60

December 34 .00 2.7 4.9 60

January 192 .00 6.5 26 60

February 1,000 .00 74 174 60

March 1,760 2.8 256 459 60

April 2,040 1.0 85 292 61

May 300 .21 29 59 61

June 552 .07 59 102 61

July 458 .00 44 84 62

August 367 .00 16 51 61

September 390 .00 17 59 61

Annual 243 1.2 50 57 59
Statistical Summaries of Streamflow 129

06132000 Missouri River below Fort Peck Dam, at Fort Peck

Site Number 109

LOCATION.--Lat 48°02'39" (NAD 27), long 106°21'21", in NW1⁄4 sec.6, T.26 N., R.42 E., McCone County, Hydrologic Unit 10060001, on right bank 2 mi 

upstream from Milk River, 6 mi south of Nashua, 8 mi downstream from Fort Peck Dam, and at river mile 1,763.5.

DRAINAGE AREA.--57,556 mi2.

PERIOD OF RECORD.--March 1934 to current year (2002).

REVISED RECORDS.--WSP 1729: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 2,018 ft (NGVD 29, U.S. Army Corps of Engineers bench mark). Prior to Apr. 14, 1938, at site 0.7 mi upstream 

at different datum; Apr. 14, 1938, to Sept. 30, 1963, at present site at datum 2.00 ft higher, all water-stage recorders. Since Oct. 1, 1969, published discharge 

is determined by flow meters and spillway discharge at Fort Peck Dam.

REMARKS.--Flow completely regulated by Fort Peck Lake. Diversions for irrigation of about 880,400 acres upstream from station. Operational level in Fort 

Peck Lake was reached beginning 1944 water year.

Magnitude and probability of annual low flow

based on 57 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 3,190 1,760 1,230 888 599 452

3 3,620 2,070 1,470 1,070 730 554

7 4,110 2,450 1,760 1,290 877 663

14 4,540 2,810 2,040 1,510 1,040 786

30 5,020 3,170 2,320 1,730 1,190 908

60 5,880 3,850 2,870 2,160 1,500 1,150

90 6,680 4,430 3,310 2,480 1,710 1,300

120 7,230 4,770 3,540 2,640 1,810 1,370

183 8,180 5,920 4,860 4,070 3,290 2,820

Magnitude and probability of seasonal low flow from

March-June based on 58 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 3,880 2,090 1,420 994 642 468

3 4,260 2,410 1,680 1,200 790 583

7 4,740 2,810 1,980 1,420 939 692

14 5,170 3,130 2,230 1,620 1,070 793

30 5,730 3,500 2,510 1,840 1,230 918

Magnitude and probability of seasonal low flow from

November-February based on 58 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 5,550 3,090 2,080 1,420 881 618

3 5,780 3,280 2,260 1,590 1,020 733

7 6,070 3,500 2,450 1,750 1,150 851

14 6,410 3,770 2,670 1,930 1,280 953

30 7,210 4,450 3,200 2,340 1,570 1,160

Duration of daily mean flows based on 58 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

1,120 1,710 3,190 4,280 5,690 6,760 7,690 8,630

40% 30% 20% 15% 10% 5% 2% 1%

10,000 11,500 13,600 14,800 16,000 19,100 26,800 31,300

Magnitude and probability of annual high flow

based on 58 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 15,700 22,200 26,700 32,700 37,300 42,100

3 15,500 21,900 26,400 32,400 37,000 41,800

7 15,300 21,700 26,100 32,000 36,600 41,400

15 15,000 21,300 25,700 31,600 36,300 41,100

30 14,500 20,400 24,700 30,300 34,700 39,300

60 13,600 18,600 22,200 26,800 30,400 34,200

90 12,600 16,700 19,500 23,200 26,000 28,800

Magnitude and probability of seasonal low flow from

July-October based on 57 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 5,190 3,080 2,310 1,810 1,370 1,130

3 5,640 3,360 2,510 1,960 1,460 1,200

7 6,010 3,590 2,700 2,100 1,580 1,290

14 6,400 3,890 2,940 2,320 1,750 1,440

30 7,460 4,590 3,460 2,700 2,010 1,630

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 28,800 3,020 11,100 7,010 58

November 21,200 2,080 8,970 3,980 58

December 12,200 1,490 9,100 2,330 58

January 14,000 1,390 9,880 3,060 58

February 15,200 1,180 9,870 3,910 58

March 13,400 1,060 7,520 3,160 58

April 17,200 856 7,300 3,150 58

May 18,800 1,030 8,570 3,490 58

June 26,200 1,060 8,800 4,300 58

July 35,000 1,160 10,000 5,350 58

August 26,200 3,450 11,800 5,650 58

September 27,100 3,000 11,500 6,540 58

Annual 14,900 5,340 9,530 2,530 58
130 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06134500 Milk River at Milk River, Alberta

(International gaging station)

Site Number 110

LOCATION.--Lat 49°08'37", long 112°04'44" (NAD 27), in NE1⁄4 sec.21, T.2, R.16 W., fourth meridian, in Alberta, Hydrologic Unit 10050002, on right bank 5 ft 

downstream from highway bridge at Milk River, Alberta, 22 mi downstream from North Fork Milk River, and at river mile 613.4.

DRAINAGE AREA.--1,050 mi2.

PERIOD OF RECORD.--June 1909 to October 1910 (no winter records), April 1911 to current year (2002). Monthly discharge only for June 1909, published in 

WSP 1309.

REVISED RECORDS.--WSP 1309: 1912. WSP 1559: 1916, 1927(M), 1947(M). WDR-MT-83: Drainage area. WDR-MT-84: 1983 (M).

GAGE.--Water-stage recorder. Altitude of gage is 3,402.78 ft (Canadian Geodetic Vertical Datum 1928). Prior to June 17, 1919, nonrecording gages, and June 17, 

1919, to Nov. 2, 1921, water-stage recorder at several sites 300 ft upstream at datum 0.61 ft higher. Nov. 3, 1921, to Aug. 28, 1947, water-stage recorder at 

site 60 ft upstream at present datum. Aug. 29, 1947, to Nov. 10, 1976, water-stage recorder located 700 ft downstream on left bank at present datum.

REMARKS.--Since 1917, flow increased during irrigation season by water from St. Mary Canal (station number 05018500). Several diversions for irrigation 

upstream from station. Environment Canada satellite telemeter at station. 

Magnitude and probability of annual low flow

based on 83 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 4.9 1.0 0.00 0.00 0.00 0.00

3 5.5 1.2 .12 .00 .00 .00

7 6.7 1.4 .40 .00 .00 .00

14 8.0 2.2 .89 .10 .00 .00

30 12 4.1 2.0 .95 .00 .00

60 18 6.5 3.4 1.8 .62 .00

90 24 10 5.9 3.6 2.0 1.3

120 31 16 11 8.1 5.7 4.4

183 99 46 28 17 9.5 6.1

Magnitude and probability of seasonal low flow from

March-June based on 86 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 31 10 4.6 2.0 0.00 0.00

3 34 11 5.3 2.4 .00 .00

7 40 15 8.3 4.3 .00 .00

14 69 24 12 5.5 1.4 .00

30 161 68 37 21 10 5.8

Magnitude and probability of seasonal low flow from

November-February based on 83 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 6.1 1.3 0.00 0.00 0.00 0.00

3 6.7 1.4 .30 .00 .00 .00

7 7.7 1.6 .51 .03 .00 .00

14 8.7 2.4 1.0 .33 .00 .00

30 12 4.1 2.0 .96 .00 .00

Duration of daily mean flows based on 86 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

1.0 2.2 6.3 13 28 45 76 162

40% 30% 20% 15% 10% 5% 2% 1%

369 553 650 698 747 944 1,090 1,440

Magnitude and probability of annual high flow

based on 86 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 1,640 2,920 4,070 5,920 7,640 9,700

3 1,420 2,360 3,160 4,410 5,530 6,820

7 1,160 1,760 2,240 2,940 3,550 4,220

15 970 1,340 1,620 1,990 2,290 2,610

30 833 1,070 1,220 1,430 1,590 1,750

60 751 919 1,020 1,140 1,230 1,310

90 715 849 917 988 1,030 1,070

Magnitude and probability of seasonal low flow from

July-October based on 85 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 33 15 9.3 6.3 3.9 2.8

3 35 16 11 7.4 4.8 3.6

7 39 18 12 8.3 5.5 4.1

14 43 20 13 9.2 6.1 4.7

30 61 25 16 10 6.6 4.8

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 555 7.8 101 103 86

November 216 8.7 56 42 86

December 133 2.2 34 25 86

January 268 1.0 31 41 85

February 616 .90 63 90 84

March 1,020 4.6 228 195 86

April 1,380 94 496 245 86

May 1,180 236 660 219 86

June 1,630 162 720 231 86

July 965 192 616 138 86

August 795 29 552 161 86

September 713 3.7 353 225 86

Annual 489 157 328 77 86
Statistical Summaries of Streamflow 131

06137400 Big Sandy Creek at reservation boundary, near Rocky Boy, Mont.

Site Number 111

LOCATION.--Lat 48°10'27", long 109°49'23" (NAD 27), in SW1⁄4NW1⁄4NE1⁄4 sec.20, T.28 N., R.15 E., Chouteau County, Hydrologic Unit 10050005, on left bank 

0.9 mi downstream from Muddy Creek, 6.0 mi south of Rocky Boy Agency, and at river mile 90.6.

DRAINAGE AREA.--24.7 mi2.

PERIOD OF RECORD.--May 1982 to current year (2002).

GAGE.--Water-stage recorder. Altitude of gage is 3,830 ft (NGVD 29). Prior to Sept. 6, 2001, water-stage recorder at site 0.1 mi downstream at different datum.

REMARKS.--No known regulation or diversions upstream from station. U.S. Geological Survey satellite telemeter at station.

Magnitude and probability of annual low flow

based on 19 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1.2 0.65 0.49 0.39 -- --

3 1.3 .73 .53 .41 -- --

7 1.5 .83 .61 .47 -- --

14 1.9 1.0 .74 .54 -- --

30 2.3 1.2 .86 .62 -- --

60 2.8 1.5 1.0 .73 -- --

90 3.1 1.7 1.2 .87 -- --

120 3.3 1.8 1.3 .98 -- --

183 3.8 2.0 1.4 1.1 -- --

Magnitude and probability of seasonal low flow from

March-June based on 20 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 2.1 1.0 0.70 0.51 -- --

3 2.4 1.2 .80 .58 -- --

7 2.6 1.3 .92 .68 -- --

14 3.2 1.8 1.3 1.0 -- --

30 4.1 2.2 1.5 1.2 -- --

Magnitude and probability of seasonal low flow from

November-February based on 20 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1.8 1.0 0.77 0.62 -- --

3 1.9 1.1 .83 .66 -- --

7 2.2 1.2 .92 .72 -- --

14 2.4 1.4 1.0 .77 -- --

30 2.7 1.5 1.1 .89 -- --

Duration of daily mean flows based on 20 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

0.19 0.37 0.93 1.6 2.4 3.2 4.0 4.9

40% 30% 20% 15% 10% 5% 2% 1%

5.9 7.9 11 14 17 26 40 58

Magnitude and probability of annual high flow

based on 20 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 40 107 184 336 -- --

3 34 85 139 240 -- --

7 29 67 105 174 -- --

15 23 51 77 121 -- --

30 19 39 58 86 -- --

60 16 30 42 59 -- --

90 14 26 35 47 -- --

Magnitude and probability of seasonal low flow from

July-October based on 20 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 2.5 1.0 0.60 0.39 -- --

3 2.6 1.1 .66 .43 -- --

7 2.9 1.3 .77 .49 -- --

14 3.2 1.4 .84 .54 -- --

30 3.5 1.6 .99 .64 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 14 0.66 5.5 4.0 20

November 11 .92 4.8 3.2 20

December 12 .81 4.3 2.9 20

January 9.4 .71 3.6 2.2 20

February 22 .76 4.4 4.5 20

March 28 .89 6.4 5.9 20

April 33 3.7 11 8.5 20

May 68 1.8 14 15 21

June 50 1.4 17 14 21

July 54 1.0 13 14 21

August 29 .50 6.6 6.2 21

September 19 .65 5.5 4.5 21

Annual 18 1.8 7.9 4.6 20
132 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06137570 Boxelder Creek near Rocky Boy, Mont.

Site Number 112

LOCATION.--Lat 48°18'07", long 109°50'37" (NAD 27), in SW1⁄4SW1⁄4NW1⁄4 sec.6, T.29 N., R.15 E., Hill County, Hydrologic Unit 10050005, on Rocky Boys 

Indian Reservation, on right bank 1,000 ft upstream from Bonneau Reservoir, 4,000 ft downstream from Wolf Creek, 4.1 mi northwest of Rocky Boy Agency, 

and at river mile 14.0. 

DRAINAGE AREA.--48.2 mi2. 

PERIOD OF RECORD.--22 years. October 1975 to September 1997 (discontinued). 

GAGE.--Water-stage recorder. Altitude of gage is 3,225 ft (NGVD 29, from topographic map).

REMARKS.--Other than beaver dams, no known regulation or diversions upstream from station. 

Magnitude and probability of annual low flow

based on 21 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1.3 0.19 0.00 0.00 -- --

3 1.3 .20 .00 .00 -- --

7 1.4 .22 .03 .00 -- --

14 1.5 .25 .06 .00 -- --

30 1.8 .42 .12 .00 -- --

60 2.5 .69 .23 .01 -- --

90 3.4 .84 .28 .03 -- --

120 3.5 1.2 .54 .25 -- --

183 3.7 1.7 1.0 .66 -- --

Magnitude and probability of seasonal low flow from

March-June based on 22 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 3.3 1.3 0.73 0.41 -- --

3 3.5 1.5 .81 .46 -- --

7 4.1 1.8 1.1 .64 -- --

14 4.7 2.4 1.6 1.1 -- --

30 6.1 3.0 1.9 1.4 -- --

Magnitude and probability of seasonal low flow from

November-February based on 21 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 2.1 1.1 0.73 0.52 -- --

3 2.2 1.2 .79 .56 -- --

7 2.5 1.3 .89 .62 -- --

14 2.9 1.5 1.0 .73 -- --

30 3.3 1.8 1.3 .95 -- --

Duration of daily mean flows based on 22 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

0.16 0.31 0.78 1.5 2.6 3.4 4.2 5.2

40% 30% 20% 15% 10% 5% 2% 1%

6.6 8.6 13 16 22 33 54 72

Magnitude and probability of annual high flow

based on 22 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 61 165 286 520 -- --

3 48 118 190 321 -- --

7 38 87 137 223 -- --

15 30 66 100 158 -- --

30 24 50 75 114 -- --

60 20 38 55 80 -- --

90 17 32 45 64 -- --

Magnitude and probability of seasonal low flow from

July-October based on 21 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1.5 0.19 0.00 0.00 -- --

3 1.6 .22 .00 .00 -- --

7 1.7 .23 .04 .00 -- --

14 1.7 .27 .07 .00 -- --

30 2.1 .43 .14 .01 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 26 0.05 6.1 6.1 22

November 20 .51 5.6 4.4 22

December 15 .93 5.0 3.4 22

January 12 1.6 4.3 2.6 22

February 9.6 1.8 5.4 2.1 22

March 29 3.4 11 8.1 22

April 37 3.9 13 9.9 22

May 100 2.4 22 24 22

June 81 .90 19 19 22

July 78 .43 12 17 22

August 34 .00 5.4 7.1 22

September 22 .00 4.8 6.0 22

Annual 22 2.7 9.5 5.6 22
Statistical Summaries of Streamflow 133

06137580 Sage Creek near Whitlash, Mont.

Site Number 113

LOCATION.--Lat 48°53'30", long 111°01'47" (NAD 27), in NW1⁄4NW1⁄4SW1⁄4 sec.12, T.36 N., R.5 E., Liberty County, Hydrologic Unit 10050006, on left bank, 

0.2 mi downstream from bridge on Black Jack Road, 10 mi southeast of Whitlash. 

DRAINAGE AREA.--7.26 mi2. 

PERIOD OF RECORD.--October 1976 to September 1982, October 1984 to September 1990 (discontinued). 

GAGE.--Water-stage recorder, Parshall flume, and V-notch sharp-crested weir. Altitude of gage is 3,900 ft (NGVD 29, from topographic map). 

REMARKS.--Diversions for irrigation of about 40 acres upstream from station. 

Magnitude and probability of annual low flow

based on 11 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.13 0.05 0.03 0.01 -- --

3 .16 .07 .04 .03 -- --

7 .24 .12 .08 .05 -- --

14 .31 .16 .11 .08 -- --

30 .39 .23 .17 .13 -- --

60 .48 .28 .20 .16 -- --

90 .60 .36 .27 .21 -- --

120 .71 .43 .33 .27 -- --

183 .90 .50 .38 .31 -- --

Magnitude and probability of seasonal low flow from

March-June based on 12 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.42 0.21 0.14 0.10 -- --

3 .52 .26 .17 .12 -- --

7 .63 .32 .22 .16 -- --

14 .95 .52 .36 .25 -- --

30 1.5 .81 .56 .39 -- --

Magnitude and probability of seasonal low flow from

November-February based on 11 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.23 0.09 0.05 0.03 -- --

3 .25 .12 .08 .05 -- --

7 .29 .18 .14 .11 -- --

14 .34 .23 .19 .17 -- --

30 .43 .30 .26 .23 -- --

Duration of daily mean flows based on 12 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

0.02 0.04 0.10 0.21 0.41 0.62 0.83 1.1

40% 30% 20% 15% 10% 5% 2% 1%

1.5 2.1 3.4 4.5 6.8 12 19 23

Magnitude and probability of annual high flow

based on 12 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 26 47 60 -- -- --

3 22 41 53 -- -- --

7 18 33 42 -- -- --

15 14 26 32 -- -- --

30 11 20 25 -- -- --

60 8.2 14 17 -- -- --

90 6.5 11 13 -- -- --

Magnitude and probability of seasonal low flow from

July-October based on 11 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.40 0.15 0.07 0.04 -- --

3 .44 .18 .10 .05 -- --

7 .50 .22 .12 .07 -- --

14 .54 .25 .15 .09 -- --

30 .63 .31 .20 .14 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 9.3 0.49 1.9 2.7 12

November 2.6 .52 1.1 .67 12

December 1.6 .36 .79 .40 12

January 1.5 .29 .66 .40 12

February 2.3 .31 .86 .51 12

March 3.4 .67 1.8 .91 12

April 7.3 1.3 4.0 1.9 12

May 20 .69 9.3 6.9 12

June 20 .34 6.8 6.2 12

July 3.6 .30 1.7 1.1 12

August 4.6 .14 1.2 1.2 12

September 7.1 .27 1.9 2.1 12

Annual 4.4 .67 2.7 1.2 12
134 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06138500 Big Sandy Creek near Box Elder, Mont.

Site Number 114

LOCATION.--Lat 48°21'36", long 109°59'32" (NAD 27, revised), in NE1⁄4 sec.13, T.30 N., R.13 E., Hill County, just downstream from mouth of Sage Creek at 

Cowan ranch and 3 mi north of Box Elder.

DRAINAGE AREA.--1,629 mi2.

PERIOD OF RECORD.--11 years (1927-38).

GAGE.--Staff gage. Altitude of gage is 2,620 ft (NGVD 29, from topographic map). Prior to Mar. 7, 1928, several staff gages 0.5 mi upstream at different datum 

on spillways of Cowan dam.

REMARKS.--Flow regulated by small storage dam and some diversions for irrigation upstream from station.

Magnitude and probability of annual low flow

based on 11 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.07 0.00 0.00 0.00 -- --

3 .13 .00 .00 .00 -- --

7 .16 .00 .00 .00 -- --

14 .19 .00 .00 .00 -- --

30 .22 .00 .00 .00 -- --

60 .24 .04 .01 .00 -- --

90 .34 .07 .03 .01 -- --

120 .42 .12 .06 .04 -- --

183 .66 .17 .08 .05 -- --

Magnitude and probability of seasonal low flow from

March-June based on 12 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.19 0.00 0.00 0.00 -- --

3 .26 .10 .04 .00 -- --

7 .34 .12 .06 .00 -- --

14 .38 .17 .13 .10 -- --

30 .48 .22 .18 .16 -- --

Magnitude and probability of seasonal low flow from

November-February based on 11 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.17 0.00 0.00 0.00 -- --

3 .18 .00 .00 .00 -- --

7 .19 .00 .00 .00 -- --

14 .23 .00 .00 .00 -- --

30 .25 .01 .00 .00 -- --

Duration of daily mean flows based on 11 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

0.02 0.04 0.09 0.18 0.36 0.54 0.71 0.89

40% 30% 20% 15% 10% 5% 2% 1%

1.2 2.9 4.8 9.5 25 53 122 222

Magnitude and probability of annual high flow

based on 11 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 104 283 382 -- -- --

3 90 240 323 -- -- --

7 64 169 230 -- -- --

15 39 108 154 -- -- --

30 24 70 106 -- -- --

60 14 42 67 -- -- --

90 11 33 53 -- -- --

Magnitude and probability of seasonal low flow from

July-October based on 12 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.29 0.00 0.00 0.00 -- --

3 .29 .00 .00 .00 -- --

7 .30 .02 .00 .00 -- --

14 .30 .04 .00 .00 -- --

30 .33 .07 .00 .00 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 10 0.01 2.0 3.1 12

November 9.1 .10 2.4 2.8 12

December 3.5 .10 1.1 1.2 12

January 8.0 .00 1.6 2.4 11

February 25 .00 3.5 7.2 11

March 75 .40 13 21 12

April 55 .30 14 19 12

May 485 .21 50 138 12

June 482 .27 60 136 12

July 60 .19 11 20 12

August 36 .03 7.4 13 12

September 20 .00 3.0 5.8 12

Annual 21 .27 6.6 7.4 11
Statistical Summaries of Streamflow 135

06140500 Milk River at Havre, Mont.

Site Number 115

LOCATION.--Lat 48°33'50", long 109°41'42" (NAD 27), in SE1⁄4NE1⁄4NE1⁄4 sec.6, T.32 N., R.16 E., Hill County, Hydrologic Unit 10050004, on left bank, 1.25 mi 

upstream from Bullhook Creek and 7th Avenue East highway bridge in Havre, 8.2 mi downstream from Big Sandy Creek, 15.8 mi downstream from Fresno 

Dam, and at river mile 419.2.

DRAINAGE AREA.--5,785 mi2, of which 670 mi2 is probably noncontributing.

PERIOD OF RECORD.--May to November 1898, April 1899 to November 1922, March, April 1923, March, April 1952 (gage heights only, in WSP 1260-B), 

June 1953 (in WSP 1320-B), September 1954 to current year (2002). Monthly discharge only for some periods, published in WSP 1309.

REVISED RECORDS.--WSP 1309: 1899-1900, 1902-04, 1907-08, 1909(M), 1912, 1917(M), 1920(M). WSP 1729: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 2,465.24 ft (NGVD 29). Prior to Nov. 4, 1902, nonrecording gage at site 0.75 mi downstream at different 

datum. Nov. 4, 1902, to Aug. 6, 1980, nonrecording gages 1.25 mi downstream on 7th Avenue East highway bridges, all at datums then in use.

REMARKS.--Diversions for irrigation of about 6,000 acres upstream from station. Since 1917, flow increased during irrigation season by water from St. Mary 

Canal (station number 05018500). Since 1939, flow regulated by Fresno Reservoir (station number 06136500). U.S. Geological Survey satellite telemeter at 

station. 

Unregulated streamflow period

Magnitude and probability of annual low flow

based on 13 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 13 0.00 0.00 0.00 -- --

3 15 .00 .00 .00 -- --

7 16 .00 .00 .00 -- --

14 17 .00 .00 .00 -- --

30 19 .09 .00 .00 -- --

60 24 2.2 .00 .00 -- --

90 41 3.9 .27 .00 -- --

120 57 9.6 1.2 .00 -- --

183 70 16 3.3 .00 -- --

Magnitude and probability of seasonal low flow from

March-June based on 17 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 70 20 9.4 4.8 -- --

3 80 24 12 6.0 -- --

7 93 30 15 7.7 -- --

14 110 36 17 8.6 -- --

30 165 81 52 34 -- --

Magnitude and probability of seasonal low flow from

November-February based on 14 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 26 7.0 0.00 0.00 -- --

3 27 7.5 .00 .00 -- --

7 27 7.9 .00 .00 -- --

14 27 8.3 .00 .00 -- --

30 28 9.0 .00 .00 -- --

Duration of daily mean flows based on 17 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

0.17 0.35 0.87 5.2 29 53 77 107

40% 30% 20% 15% 10% 5% 2% 1%

155 225 360 482 670 1,090 1,920 2,710

Magnitude and probability of annual high flow

based on 17 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 2,970 5,490 7,120 9,000 -- --

3 2,670 4,730 5,930 7,180 -- --

7 2,220 3,720 4,480 5,200 -- --

15 1,710 2,770 3,300 3,790 -- --

30 1,250 2,030 2,430 2,820 -- --

60 878 1,340 1,560 1,750 -- --

90 703 1,070 1,240 1,390 -- --

Magnitude and probability of seasonal low flow from

July-October based on 14 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 25 0.00 0.00 0.00 -- --

3 25 .00 .00 .00 -- --

7 26 .08 .00 .00 -- --

14 28 .26 .00 .00 -- --

30 30 1.3 .00 .00 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 281 1.5 115 76 16

November 250 1.0 100 64 16

December 160 25 72 44 15

January 150 5.0 54 47 15

February 1,400 1.4 153 332 17

March 1,600 30 469 431 17

April 1,740 59 593 532 17

May 1,620 61 511 408 17

June 2,190 35 631 561 17

July 2,040 18 372 514 17

August 414 5.0 136 138 16

September 664 2.8 130 166 16

Annual 571 45 286 141 17
136 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06140500 Milk River at Havre, Mont.—Continued

Site Number 115

Regulated streamflow period

Magnitude and probability of annual low flow

based on 51 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 23 10 5.5 2.8 0.22 0.00

3 25 12 6.9 3.8 .39 .00

7 27 15 9.8 6.4 1.4 .00

14 32 18 12 7.5 1.6 .00

30 38 21 13 7.8 1.7 .00

60 45 25 14 8.1 2.8 1.0

90 50 27 15 8.5 3.3 1.7

120 54 28 18 11 6.0 3.8

183 133 68 43 28 16 11

Magnitude and probability of seasonal low flow from

March-June based on 54 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 39 19 12 8.6 5.5 4.1

3 44 22 15 11 7.5 5.8

7 50 26 18 13 9.3 7.3

14 63 32 22 16 11 8.6

30 97 40 25 17 11 8.8

Magnitude and probability of seasonal low flow from

November-February based on 52 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 24 13 8.2 5.1 1.2 0.00

3 27 15 9.9 6.5 1.8 .00

7 30 17 11 7.6 2.1 .00

14 34 19 13 8.2 2.1 .00

30 39 21 14 8.7 2.3 .00

Duration of daily mean flows based on 54 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

5.1 10 23 30 42 55 81 170

40% 30% 20% 15% 10% 5% 2% 1%

363 595 847 970 1,090 1,340 1,490 2,010

Magnitude and probability of annual high flow

based on 54 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 1,650 2,800 3,990 6,210 8,570 11,700

3 1,560 2,570 3,610 5,530 7,540 10,200

7 1,470 2,320 3,130 4,500 5,850 7,550

15 1,370 1,970 2,460 3,180 3,810 4,520

30 1,240 1,640 1,890 2,210 2,430 2,660

60 1,080 1,340 1,480 1,620 1,710 1,790

90 1,020 1,240 1,340 1,430 1,480 1,520

Magnitude and probability of seasonal low flow from

July-October based on 53 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 48 19 10 5.7 2.7 1.6

3 53 21 12 7.1 3.7 2.3

7 56 25 16 11 6.9 5.0

14 70 34 23 17 12 9.0

30 101 46 30 20 13 9.9

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 628 9.0 158 127 55

November 325 5.0 71 56 55

December 144 2.0 50 28 54

January 780 5.0 61 104 53

February 691 5.0 74 103 53

March 2,110 5.0 274 447 55

April 2,570 25 462 508 55

May 2,190 261 894 342 54

June 1,570 233 877 270 54

July 1,580 252 918 303 54

August 1,300 51 716 293 54

September 956 33 397 212 55

Annual 728 160 416 127 54
Statistical Summaries of Streamflow 137

06154100 Milk River near Harlem, Mont.

Site Number 116

LOCATION.--Lat 48°29'22", long 108°45'28" (NAD 27), in NE1⁄4SE1⁄4NE1⁄4 sec.32, T.32 N., R.23 E., Blaine County, Hydrologic Unit 10050004, Fort Belknap 

Indian Reservation, on right bank 30 ft downstream from U.S. Highway 2 bridge, 0.6 mi northeast of unincorporated community of Fort Belknap Agency, 

3.5 mi southeast of Harlem, and at river mile 332.2.

DRAINAGE AREA.--9,822 mi2.

PERIOD OF RECORD.--October 1959 to September 1969, October 1982 to current year (2002; seasonal record beginning 1994 water year). Gage heights only 

for period Apr. 3-25, 1952, published as "at Fort Belknap" in WSP 1260-B.

REVISED RECORDS.--WSP 1729: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 2,319.48 ft (NGVD 29). Apr. 3-25, 1952, nonrecording gage on old bridge 200 ft downstream at different 

datum. Nov. 1, 1959, to Mar. 12, 1968, nonrecording gage or water-stage recorder at several sites within 0.5 mi of present site at different datum.

REMARKS.--Flow increased during irrigation season by water from St. Mary Canal (station number 05018500). Flow mainly regulated by Fresno Reservoir 

(station number 06136500) since 1939. Diversions for irrigation of about 60,000 acres of which about 13,000 acres lie downstream from station. Bureau of 

Reclamation satellite telemeter at station. 

Magnitude and probability of annual low flow

based on 20 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 23 5.3 1.5 0.00 -- --

3 30 8.9 3.1 .00 -- --

7 33 10 3.7 .00 -- --

14 36 17 9.8 .00 -- --

30 48 25 13 6.2 -- --

60 53 31 24 18 -- --

90 59 37 29 23 -- --

120 64 40 32 27 -- --

183 112 67 53 44 -- --

Magnitude and probability of seasonal low flow from

March-June based on 30 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 49 16 8.2 4.6 2.3 --

3 62 20 10 5.8 2.9 --

7 70 25 13 7.9 4.2 --

14 89 43 31 24 18 --

30 150 67 45 32 22 --

Magnitude and probability of seasonal low flow from

November-February based on 20 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 32 19 15 12 -- --

3 35 21 16 13 -- --

7 39 23 18 14 -- --

14 43 26 20 16 -- --

30 57 32 25 20 -- --

Duration of daily mean flows based on 21 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

14 20 31 41 65 89 130 244

40% 30% 20% 15% 10% 5% 2% 1%

350 451 567 652 736 1,050 1,930 2,910

Magnitude and probability of annual high flow

based on 21 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 1,450 3,450 5,810 10,700 -- --

3 1,320 3,060 5,080 9,240 -- --

7 1,160 2,560 4,150 7,320 -- --

15 957 1,940 2,990 4,980 -- --

30 799 1,480 2,170 3,470 -- --

60 650 1,110 1,560 2,360 -- --

90 595 1,000 1,390 2,080 -- --

Magnitude and probability of seasonal low flow from

July-October based on 29 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 71 16 4.5 0.62 0.00 --

3 78 21 7.4 1.4 .00 --

7 87 25 8.7 1.8 .00 --

14 94 34 17 6.4 .00 --

30 145 49 22 10 3.9 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 949 37 209 194 30

November 289 31 94 67 21

December 198 26 72 43 21

January 139 19 69 32 21

February 200 26 85 44 21

March 2,290 37 436 555 30

April 2,940 54 576 762 30

May 3,510 129 669 590 30

June 1,510 232 596 268 30

July 2,480 138 576 396 30

August 726 19 399 177 30

September 1,910 32 354 338 30

Annual 857 139 350 201 21
138 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06154400 Peoples Creek near Hays, Mont.

Site Number 117

LOCATION.--Lat 48°13'25", long 108°42'48" (NAD 27), in SW1⁄4 sec.35, T.29 N., R.23 E., Blaine County, Hydrologic Unit 10050009, on right bank 45 ft 

downstream from bridge on State Highway 66, 2.5 mi downstream from Myrtle Creek, 16.4 mi north of Hays, and at river mile 47.2.

DRAINAGE AREA.--220 mi2.

PERIOD OF RECORD.--December 1966 to current year (2002).

GAGE.--Water-stage recorder. Altitude of gage is 2,714.10 ft (NGVD 29).

REMARKS.--Some storage in numerous stock and beaver ponds and diversions for irrigation of about 1,300 acres upstream from station. Bureau of Indian Affairs 

satellite telemeter at station. 

Magnitude and probability of annual low flow

based on 35 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.00 0.00 0.00 0.00 0.00 --

3 .00 .00 .00 .00 .00 --

7 .00 .00 .00 .00 .00 --

14 .00 .00 .00 .00 .00 --

30 .01 .00 .00 .00 .00 --

60 .05 .00 .00 .00 .00 --

90 .13 .01 .00 .00 .00 --

120 .20 .01 .00 .00 .00 --

183 .41 .03 .00 .00 .00 --

Magnitude and probability of seasonal low flow from

March-June based on 36 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.12 0.00 0.00 0.00 0.00 --

3 .19 .00 .00 .00 .00 --

7 .32 .02 .00 .00 .00 --

14 .77 .07 .01 .00 .00 --

30 2.6 .25 .05 .01 .00 --

Magnitude and probability of seasonal low flow from

November-February based on 35 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.00 0.00 0.00 0.00 0.00 --

3 .00 .00 .00 .00 .00 --

7 .00 .00 .00 .00 .00 --

14 .04 .00 .00 .00 .00 --

30 .14 .00 .00 .00 .00 --

Duration of daily mean flows based on 35 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

0.02 0.04 0.10 0.21 0.42 0.63 0.84 1.3

40% 30% 20% 15% 10% 5% 2% 1%

3.7 6.5 11 15 23 47 106 175

Magnitude and probability of annual high flow

based on 35 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 88 325 630 1,260 1,950 --

3 75 275 527 1,030 1,560 --

7 58 205 383 724 1,080 --

15 40 139 252 461 668 --

30 29 95 165 286 398 --

60 21 67 112 185 247 --

90 18 55 90 141 182 --

Magnitude and probability of seasonal low flow from

July-October based on 35 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.00 0.00 0.00 0.00 0.00 --

3 .00 .00 .00 .00 .00 --

7 .00 .00 .00 .00 .00 --

14 .00 .00 .00 .00 .00 --

30 .02 .00 .00 .00 .00 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 37 0.00 3.5 7.1 35

November 20 .00 3.4 4.7 35

December 13 .00 2.8 3.6 36

January 30 .00 3.6 6.3 36

February 75 .00 9.2 18 36

March 285 .00 29 54 36

April 122 .05 18 25 36

May 190 .01 31 51 36

June 123 .03 21 31 36

July 52 .00 8.4 13 36

August 21 .00 2.4 5.3 36

September 58 .00 3.7 10 36

Annual 48 .10 11 13 35
Statistical Summaries of Streamflow 139

06154410 Little Peoples Creek near Hays, Mont.

Site Number 118

LOCATION.--Lat 47°57'58", long 108°39'36" (NAD 27), in SE1⁄4SE1⁄4NW1⁄4 sec.32, T.26 N., R.24 E., Blaine County, Hydrologic Unit 10050009, on right bank 

0.5 mi upstream from west entrance to Mission Canyon, 2 mi southeast of Hays, and at river mile 23.1.

DRAINAGE AREA.--13.0 mi2.

PERIOD OF RECORD.--August 1972 to current year (2002).

REVISED RECORDS.--WDR MT-81-1: Drainage area.

GAGE.--Water-stage recorder and crest-stage gage. Altitude of gage is 3,769.72 ft (NGVD 29). August 1972 to June 24, 1976, gage at former site at datum 10.00 ft 

higher. Prior to Apr. 22, 1987, gage located 330 ft downstream.

REMARKS.--No known regulation or diversion upstream from station.

Magnitude and probability of annual low flow

based on 29 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1.3 1.0 0.88 0.78 0.68 --

3 1.3 1.0 .90 .81 .71 --

7 1.3 1.1 .93 .83 .74 --

14 1.4 1.1 .98 .89 .80 --

30 1.5 1.2 1.0 .93 .84 --

60 1.7 1.3 1.1 1.0 .88 --

90 1.8 1.3 1.2 1.0 .91 --

120 1.8 1.4 1.2 1.1 .96 --

183 1.9 1.4 1.3 1.1 1.0 --

Magnitude and probability of seasonal low flow from

March-June based on 30 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1.5 1.1 0.97 0.85 0.74 --

3 1.6 1.2 1.0 .89 .78 --

7 1.6 1.2 1.0 .93 .81 --

14 1.7 1.3 1.1 1.0 .90 --

30 1.9 1.4 1.2 1.1 .96 --

Magnitude and probability of seasonal low flow from

November-February based on 30 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1.4 1.1 0.98 0.89 0.80 --

3 1.5 1.1 .99 .89 .80 --

7 1.5 1.2 1.0 .91 .81 --

14 1.5 1.2 1.0 .92 .82 --

30 1.6 1.2 1.1 .94 .83 --

Duration of daily mean flows based on 30 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

0.90 1.0 1.2 1.4 1.6 1.8 2.0 2.3

40% 30% 20% 15% 10% 5% 2% 1%

2.7 3.3 4.4 5.3 7.1 12 22 35

Magnitude and probability of annual high flow

based on 30 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 32 84 139 236 331 --

3 25 63 104 177 251 --

7 18 45 74 128 184 --

15 14 32 51 86 122 --

30 11 23 36 57 79 --

60 8.5 17 25 38 50 --

90 7.0 13 19 28 36 --

Magnitude and probability of seasonal low flow from

July-October based on 29 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1.7 1.3 1.2 1.1 1.0 --

3 1.7 1.3 1.2 1.1 1.0 --

7 1.7 1.4 1.2 1.1 1.1 --

14 1.8 1.4 1.3 1.2 1.1 --

30 1.8 1.4 1.3 1.2 1.1 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 6.9 1.1 2.4 1.2 30

November 4.6 1.1 2.2 .88 30

December 3.8 .93 2.0 .73 30

January 3.8 .90 1.9 .72 30

February 3.5 .95 1.8 .64 30

March 5.5 1.1 2.3 1.2 30

April 22 1.2 4.6 4.4 30

May 76 1.5 12 16 30

June 27 2.0 8.4 6.4 30

July 33 1.4 5.4 5.8 30

August 8.1 1.2 3.0 1.5 31

September 8.4 1.1 2.6 1.6 31

Annual 12 1.5 4.1 2.4 30
140 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06154430 Lodge Pole Creek at Lodge Pole, Mont.

Site Number 119

LOCATION.--Lat 48°01'52", long 108°31'55" (NAD 27), in SE1⁄4SE1⁄4SW1⁄4 sec.5, T.26 N., R.25 E., Blaine County, Hydrologic Unit 10050009, Fort Belknap 

Indian Reservation, 10 ft upstream from culvert in county road just south of Lodge Pole and 8 mi northeast of Hays. 

DRAINAGE AREA.--19.5 mi2. 

PERIOD OF RECORD.--March 1987 to October 2000 (discontinued). 

GAGE.--Water-stage recorder and crest-stage gage. Altitude of gage is 3,420 ft (NGVD 29, from topographic map). 

REMARKS.--No known diversion for irrigation upstream from station. 

Magnitude and probability of annual low flow

based on 13 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.32 0.12 0.06 0.03 -- --

3 .34 .14 .07 .04 -- --

7 .38 .15 .08 .04 -- --

14 .40 .16 .09 .05 -- --

30 .44 .18 .10 .05 -- --

60 .57 .24 .13 .07 -- --

90 .88 .47 .29 .18 -- --

120 1.1 .65 .41 .25 -- --

183 1.5 .85 .51 .30 -- --

Magnitude and probability of seasonal low flow from

March-June based on 14 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.42 0.15 0.08 0.04 -- --

3 .44 .17 .09 .05 -- --

7 .48 .19 .11 .06 -- --

14 .52 .21 .12 .06 -- --

30 .59 .24 .13 .08 -- --

Magnitude and probability of seasonal low flow from

November-February based on 13 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.63 0.30 0.17 0.09 -- --

3 .67 .34 .19 .11 -- --

7 .74 .38 .22 .12 -- --

14 .79 .41 .24 .14 -- --

30 .88 .46 .27 .15 -- --

Duration of daily mean flows based on 13 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

0.03 0.05 0.13 0.26 0.51 0.77 1.0 1.4

40% 30% 20% 15% 10% 5% 2% 1%

1.7 2.2 2.8 3.5 4.8 9.8 20 31

Magnitude and probability of annual high flow

based on 13 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 44 94 123 152 -- --

3 30 65 87 111 -- --

7 18 42 61 84 -- --

15 13 30 43 61 -- --

30 9.8 22 32 45 -- --

60 7.2 15 21 29 -- --

90 5.8 11 16 21 -- --

Magnitude and probability of seasonal low flow from

July-October based on 14 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1.1 0.43 0.23 0.12 -- --

3 1.2 .47 .25 .14 -- --

7 1.2 .50 .27 .14 -- --

14 1.4 .55 .29 .15 -- --

30 1.5 .59 .31 .17 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 2.8 0.23 1.8 0.83 14

November 2.3 .21 1.6 .55 13

December 1.8 .14 1.1 .40 13

January 1.8 .10 1.0 .43 13

February 1.6 .07 .82 .37 13

March 4.6 .07 1.1 1.1 14

April 5.8 .04 1.5 1.8 14

May 18 .32 5.2 5.8 14

June 21 .29 7.4 7.1 14

July 29 .30 5.5 7.4 14

August 8.1 .12 2.5 2.0 14

September 3.6 .18 1.9 1.0 14

Annual 4.6 .55 2.7 1.5 13
Statistical Summaries of Streamflow 141

06154550 Peoples Creek below Kuhr Coulee, near Dodson, Mont.

Site Number 120

LOCATION.--Lat 48°21'49", long 108°21'16" (NAD 27), in NW1⁄4NW1⁄4NE1⁄4 sec.16, T.30 N., R.26 E., Phillips County, Hydrologic Unit 10050009, on right bank 

10 ft downstream from bridge on county highway, 2.4 mi downstream from Kuhr Coulee, 5.5 mi southwest of Dodson, and at river mile 7.8.

DRAINAGE AREA.--675 mi2.

PERIOD OF RECORD.--April 1918 to November 1921 (fragmentary), June 1951 to September 1973, October 1981 to September 1988, published as "near 

Dodson," October 1988 to current year (2002). Monthly discharge only for some periods, published in WSP 1309.

GAGE.--Water-stage recorder. Altitude of gage is 2,309.18 ft (NGVD 29, levels by Bureau of Indian Affairs). Prior to June 1951, nonrecording gage at site 0.5 mi 

upstream at different datum. June 1, 1951, to Sept. 30, 1988, water-stage recorder at sites 2.5 mi upstream at different datum.

REMARKS.--Diversions for irrigation of about 3,300 acres upstream from station. U.S. Geological Survey satellite telemeter at station. 

Magnitude and probability of annual low flow

based on 41 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.00 0.00 0.00 0.00 0.00 --

3 .00 .00 .00 .00 .00 --

7 .00 .00 .00 .00 .00 --

14 .00 .00 .00 .00 .00 --

30 .00 .00 .00 .00 .00 --

60 .02 .00 .00 .00 .00 --

90 .42 .00 .00 .00 .00 --

120 1.3 .03 .00 .00 .00 --

183 1.8 .07 .00 .00 .00 --

Magnitude and probability of seasonal low flow from

March-June based on 43 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.25 0.00 0.00 0.00 0.00 --

3 .44 .00 .00 .00 .00 --

7 .98 .00 .00 .00 .00 --

14 2.3 .03 .00 .00 .00 --

30 5.8 .47 .07 .01 .00 --

Magnitude and probability of seasonal low flow from

November-February based on 43 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.00 0.00 0.00 0.00 0.00 --

3 .00 .00 .00 .00 .00 --

7 .00 .00 .00 .00 .00 --

14 .00 .00 .00 .00 .00 --

30 .16 .00 .00 .00 .00 --

Duration of daily mean flows based on 43 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

0.03 0.05 0.13 0.26 0.51 0.77 1.1 2.9

40% 30% 20% 15% 10% 5% 2% 1%

6.0 11 21 30 46 101 261 473

Magnitude and probability of annual high flow

based on 43 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 411 1,230 2,170 3,960 5,830 --

3 311 953 1,710 3,200 4,780 --

7 222 674 1,190 2,150 3,130 --

15 144 423 726 1,270 1,800 --

30 92 265 445 756 1,050 --

60 61 171 282 466 635 --

90 48 131 210 337 450 --

Magnitude and probability of seasonal low flow from

July-October based on 43 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.00 0.00 0.00 0.00 0.00 --

3 .00 .00 .00 .00 .00 --

7 .00 .00 .00 .00 .00 --

14 .00 .00 .00 .00 .00 --

30 .01 .00 .00 .00 .00 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 195 0.00 8.6 29 44

November 64 .00 5.8 10 44

December 62 .00 4.6 10 43

January 64 .00 5.3 12 43

February 369 .00 31 67 43

March 384 .00 79 102 43

April 520 .57 55 107 46

May 575 .09 54 111 47

June 332 .00 42 66 48

July 128 .00 23 34 48

August 31 .00 3.4 6.1 47

September 480 .00 13 69 48

Annual 131 1.0 27 29 43
142 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06155030 Milk River near Dodson, Mont.

Site Number 121

LOCATION.--Lat 48°24'11", long 108°17'35" (NAD 27), in NE1⁄4SE1⁄4NW1⁄4 sec.36, T.31 N., R.26 E., Phillips County, Hydrologic Unit 10050004, on left bank 

30 ft downstream from U.S. Highway 2 bridge, 0.95 mi downstream from Dodson Dam, 1.9 mi west of Dodson, and at river mile 273.2.

DRAINAGE AREA.--11,192 mi2.

PERIOD OF RECORD.--October 1982 to current year (2002; seasonal record beginning water year 1994).

GAGE.--Water-stage recorder. Altitude of gage is 2,250 ft (NGVD 29).

REMARKS.--Numerous diversions for irrigation upstream from station. Bureau of Reclamation satellite telemeter at station. 

Magnitude and probability of annual low flow

based on 10 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.00 0.00 0.00 0.00 -- --

3 .00 .00 .00 .00 -- --

7 .29 .00 .00 .00 -- --

14 .96 .07 .00 .00 -- --

30 3.5 .72 .27 .11 -- --

60 14 7.2 5.1 3.8 -- --

90 24 12 8.1 5.9 -- --

120 34 21 18 16 -- --

183 42 28 25 24 -- --

Magnitude and probability of seasonal low flow from

March-June based on 20 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 3.1 0.53 0.00 0.00 -- --

3 4.0 .96 .41 .00 -- --

7 5.3 1.5 .76 .45 -- --

14 7.8 2.2 1.2 .70 -- --

30 13 4.0 2.3 1.5 -- --

Magnitude and probability of seasonal low flow from

November-February based on 11 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 27 7.7 1.5 0.00 -- --

3 37 16 5.5 .00 -- --

7 39 17 5.7 .00 -- --

14 45 19 9.1 .23 -- --

30 49 29 22 17 -- --

Duration of daily mean flows based on 11 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

0.35 0.70 2.7 5.7 13 21 33 49

40% 30% 20% 15% 10% 5% 2% 1%

69 94 162 232 395 738 1,630 2,850

Magnitude and probability of annual high flow

based on 11 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 1,020 3,610 7,480 -- -- --

3 937 3,270 6,750 -- -- --

7 764 2,580 5,210 -- -- --

15 544 1,620 3,000 -- -- --

30 357 975 1,730 -- -- --

60 249 617 1,050 -- -- --

90 210 511 859 -- -- --

Magnitude and probability of seasonal low flow from

July-October based on 19 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 2.0 0.00 0.00 0.00 -- --

3 2.8 .00 .00 .00 -- --

7 3.2 .09 .00 .00 -- --

14 4.7 .65 .16 .00 -- --

30 8.5 2.2 1.1 .61 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 2,690 5.1 203 604 20

November 421 25 106 108 11

December 275 17 78 70 11

January 230 18 83 61 11

February 526 20 130 142 11

March 2,250 16 449 693 20

April 1,690 2.3 197 443 20

May 1,680 3.4 190 366 20

June 655 16 244 215 20

July 599 8.7 181 161 20

August 362 6.7 67 78 20

September 1,730 .71 135 396 20

Annual 524 37 163 162 11
Statistical Summaries of Streamflow 143

06155500 Milk River at Malta, Mont.

Site Number 122

LOCATION.--Lat 48°21'43", long 107°51'46" (NAD 27), in NW1⁄4 sec.17, T.30 N., R.30 E. Phillips County, at the old highway bridge at Malta.

DRAINAGE AREA.--11,762 mi2.

PERIOD OF RECORD.--14 years (1902-16).

GAGE.--Chain gage. Altitude of gage is 2,221.40 ft (NGVD 29). 

REMARKS.--Many large diversions for irrigation upstream from station. Flow has been increased by water from the St. Mary Canal since 1917.

Magnitude and probability of annual low flow

based on 9 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 -- -- -- -- -- --

3 -- -- -- -- -- --

7 -- -- -- -- -- --

14 -- -- -- -- -- --

30 -- -- -- -- -- --

60 -- -- -- -- -- --

90 -- -- -- -- -- --

120 -- -- -- -- -- --

183 -- -- -- -- -- --

Magnitude and probability of seasonal low flow from

March-June based on 13 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 54 6.5 0.84 0.00 -- --

3 61 7.2 .86 .00 -- --

7 74 8.5 .90 .00 -- --

14 80 11 1.6 .00 -- --

30 122 20 5.9 1.8 -- --

Magnitude and probability of seasonal low flow from

November-February based on 11 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 43 13 0.00 0.00 -- --

3 44 14 .00 .00 -- --

7 44 15 .00 .00 -- --

14 47 15 1.3 .00 -- --

30 47 15 3.8 .00 -- --

Duration of daily mean flows based on 11 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

0.09 0.18 0.44 0.89 23 52 79 114

40% 30% 20% 15% 10% 5% 2% 1%

184 262 501 840 1,260 1,980 4,110 5,830

Magnitude and probability of annual high flow

based on 11 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 4,550 8,140 10,300 -- -- --

3 4,330 7,700 9,650 -- -- --

7 3,880 6,850 8,450 -- -- --

15 3,180 5,470 6,670 -- -- --

30 2,460 3,800 4,330 -- -- --

60 1,690 2,540 2,810 -- -- --

90 1,260 1,950 2,200 -- -- --

Magnitude and probability of seasonal low flow from

July-October based on 9 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 -- -- -- -- -- --

3 -- -- -- -- -- --

7 -- -- -- -- -- --

14 -- -- -- -- -- --

30 -- -- -- -- -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 392 82 183 94 10

November 292 21 141 72 11

December 200 15 86 48 11

January 220 5.0 63 55 12

February 1,250 5.0 229 388 12

March 3,980 80 855 1,070 13

April 6,430 10 1,810 2,100 13

May 1,830 5.3 643 643 13

June 2,260 25 855 782 13

July 2,440 1.1 495 655 13

August 423 1.0 183 142 13

September 1,740 12 277 489 11

Annual 983 55 446 260 11
144 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06164510 Milk River at Juneberg Bridge, near Saco, Mont.

Site Number 123

LOCATION.--Lat 48°30'32", long 107°13'02" (NAD 27), in NE1⁄4NE1⁄4 sec.30, T.32 N., R.35 E., Phillips County, Hydrologic Unit 10050014, on left bank 25 ft 

upstream from Juneberg bridge on Phillips County road, 1.5 mi downstream from Frenchman River, 6.9 mi northeast of Saco, and at river mile 152.3.

DRAINAGE AREA.--17,670 mi2.

PERIOD OF RECORD.--October 1977 to current year (2002).

GAGE.--Water-stage recorder. Altitude of gage is 2,130 ft (NGVD 29).

REMARKS.--Flow increased during irrigation season by water from St. Mary Canal which diverts from the St. Mary River near Babb (station number 05017500). 

Flow regulated by Fresno Reservoir (station number 06136500), two reservoirs in Lodge Creek basin in Saskatchewan (station numbers 06144260 and 

06144360), and four reservoirs in Frenchman River basin in Saskatchewan. Many small dams are used to divert water for irrigation upstream from station. 

U.S. Army Corps of Engineers satellite telemeter at station. 

Magnitude and probability of annual low flow

based on 24 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 51 25 14 7.8 -- --

3 53 27 16 9.1 -- --

7 55 29 18 11 -- --

14 57 31 21 14 -- --

30 67 35 23 16 -- --

60 86 47 32 22 -- --

90 100 59 43 32 -- --

120 107 63 48 37 -- --

183 116 70 56 47 -- --

Magnitude and probability of seasonal low flow from

March-June based on 25 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 53 29 22 17 13 --

3 56 32 24 19 15 --

7 59 33 25 21 17 --

14 68 37 28 23 19 --

30 100 47 33 25 19 --

Magnitude and probability of seasonal low flow from

November-February based on 24 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 61 38 31 25 -- --

3 65 41 32 27 -- --

7 70 45 36 30 -- --

14 79 51 40 32 -- --

30 86 56 44 36 -- --

Duration of daily mean flows based on 25 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

20 25 35 49 70 97 124 153

40% 30% 20% 15% 10% 5% 2% 1%

182 233 326 433 721 1,380 3,130 5,510

Magnitude and probability of annual high flow

based on 25 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 2,090 6,060 10,400 18,300 26,300 --

3 1,950 5,710 9,900 17,600 25,500 --

7 1,650 5,020 8,960 16,600 24,700 --

15 1,250 3,910 7,220 14,100 21,800 --

30 897 2,600 4,630 8,730 13,300 --

60 642 1,730 2,960 5,350 7,920 --

90 549 1,420 2,380 4,180 6,080 --

Magnitude and probability of seasonal low flow from

July-October based on 24 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 73 32 17 8.9 -- --

3 75 33 18 10 -- --

7 77 35 20 12 -- --

14 80 37 23 15 -- --

30 92 41 26 17 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 4,040 25 296 798 25

November 597 60 155 108 25

December 406 45 122 77 25

January 271 33 119 62 25

February 1,760 49 223 343 25

March 4,080 47 1,010 1,290 25

April 6,220 38 778 1,470 25

May 2,540 56 470 653 25

June 2,260 103 484 461 25

July 1,840 30 423 367 25

August 693 9.4 240 140 25

September 1,520 23 242 341 25

Annual 1,040 70 381 316 25
Statistical Summaries of Streamflow 145

06169500 Rock Creek below Horse Creek, near international boundary

(hydrologic bench-mark station)

Site Number 124

LOCATION.--Lat 48°58'10", long 106°50'20" (NAD 27), in NE1⁄4NW1⁄4 sec.15, T.37 N., R.37 E., Valley County, Hydrologic Unit 10050015, on right bank 2 mi 

south of international boundary, 3 mi downstream from Horse Creek, 21 mi northwest of Opheim, and at river mile 82.0.

DRAINAGE AREA.--328 mi2.

PERIOD OF RECORD.--March 1916 to October 1926, September 1956 to current year (2002; seasonal records only prior to October 1978). Monthly discharge 

only for some periods, published in WSP 1309. Published as "Rock Creek near Barnard, Mt.", 1916-17. Prior to September 1956, records were collected at 

both Horse Creek (1914-56) and Rock Creek above Horse Creek (1914-56). Summations are equivalent to records at this site.

REVISED RECORDS.--WSP 1509: 1925(M), WSP 1729: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 2,530 ft (NGVD 29). March 1916 to October 1926, nonrecording gages at several sites within 500 ft upstream 

at different datum.

REMARKS.--Several small diversions for irrigation upstream from station. U.S. Geological Survey satellite telemeter at station. 

Magnitude and probability of annual low flow

based on 24 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.00 0.00 0.00 0.00 -- --

3 .00 .00 .00 .00 -- --

7 .00 .00 .00 .00 -- --

14 .00 .00 .00 .00 -- --

30 .00 .00 .00 .00 -- --

60 .02 .00 .00 .00 -- --

90 .28 .03 .00 .00 -- --

120 .70 .23 .08 .02 -- --

183 .71 .30 .17 .10 -- --

Magnitude and probability of seasonal low flow from

March-June based on 55 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.00 0.00 0.00 0.00 0.00 0.00

3 .00 .00 .00 .00 .00 .00

7 .02 .00 .00 .00 .00 .00

14 .43 .00 .00 .00 .00 .00

30 3.1 .80 .19 .00 .00 .00

Magnitude and probability of seasonal low flow from

November-February based on 24 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.00 0.00 0.00 0.00 -- --

3 .00 .00 .00 .00 -- --

7 .00 .00 .00 .00 -- --

14 .00 .00 .00 .00 -- --

30 .00 .00 .00 .00 -- --

Duration of daily mean flows based on 24 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

0.03 0.05 0.13 0.26 0.51 0.77 1.1 1.9

40% 30% 20% 15% 10% 5% 2% 1%

3.0 5.2 10 16 30 85 260 550

Magnitude and probability of annual high flow

based on 24 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 436 1,090 1,620 2,360 -- --

3 323 864 1,370 2,170 -- --

7 206 550 892 1,460 -- --

15 126 324 522 857 -- --

30 79 197 311 501 -- --

60 46 109 170 271 -- --

90 34 78 119 186 -- --

Magnitude and probability of seasonal low flow from

July-October based on 56 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.00 0.00 0.00 0.00 0.00 0.00

3 .01 .00 .00 .00 .00 .00

7 .02 .00 .00 .00 .00 .00

14 .04 .00 .00 .00 .00 .00

30 .11 .00 .00 .00 .00 .00

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 58 0.00 3.4 7.9 57

November 2.8 .10 1.5 .72 24

December 2.2 .03 .75 .57 24

January 1.8 .00 .29 .46 24

February 96 .00 6.2 20 24

March 398 .00 82 107 55

April 487 4.0 102 127 57

May 89 1.5 17 19 57

June 172 .17 17 27 57

July 74 .00 11 18 57

August 15 .00 1.6 2.9 57

September 21 .00 1.8 3.5 57

Annual 37 1.9 14 12 24
146 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06172000 Milk River near Vandalia, Mont.

Site Number 125

LOCATION.--Lat 48°22'21", long 106°58'25" (NAD 27), in SW1⁄4SW1⁄4NE1⁄4 sec.7, T.30 N., R.37 E., Valley County, Hydrologic Unit 10050012, on right bank, 

just downstream from Vandalia Dam, 3.0 mi upstream from Long Coulee, 3.2 mi northwest of Vandalia, and at river mile 117.3. 

DRAINAGE AREA.--20,926 mi2. Area at site used October 1969 to September 1973, 20,944 mi2. 

PERIOD OF RECORD.--October 1914 to September 1925, August 1928 to September 1939, October 1969 to September 1973, October 1982 to May 31, 1987 

(discontinued). April to May 1952, infrequent gage heights, published in WSP 1260-B. Monthly discharge only for some periods, published in WSP 1309. 

Published as "at Vandalia" October 1969 to September 1973. 

REVISED RECORDS.--WSP 1309: 1920(M). WSP 1729: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 2,090.00 ft (NGVD 29, from topographic map). October 1969 to September 1973, nonrecording gage 7.1 mi 

downstream at datum 5.00 ft lower. 

REMARKS.--Since 1917, flow increased during irrigation season by water from St. Mary Canal which diverts from the St. Mary River near Babb. Flow regulated 

by Fresno and Nelson Reservoirs, five reservoirs in Lodge Creek basin in Saskatchewan, and four reservoirs in Frenchman River basin in Saskatchewan. Water 

is diverted at Vandalia Dam by canal, capacity about 300 ft3/s, for irrigation downstream. Diversions upstream from station for irrigation of about 126,000 acres 

of which about 18,000 acres lies downstream from station.

Magnitude and probability of annual low flow

based on 27 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 2.0 0.00 0.00 0.00 0.00 --

3 3.1 .37 .00 .00 .00 --

7 5.4 .38 .01 .00 .00 --

14 8.5 1.7 .56 .09 .00 --

30 19 4.9 2.1 .93 .35 --

60 38 11 4.9 2.3 .84 --

90 58 24 14 8.0 4.1 --

120 74 29 16 9.6 5.0 --

183 93 39 25 16 10 --

Magnitude and probability of seasonal low flow from

March-June based on 28 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 13 1.2 0.14 0.00 0.00 --

3 15 1.6 .35 .05 .00 --

7 22 2.0 .41 .09 .01 --

14 28 4.1 1.3 .49 .15 --

30 88 12 3.5 1.1 .44 --

Magnitude and probability of seasonal low flow from

November-February based on 28 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 27 7.0 2.8 0.87 0.00 --

3 33 11 5.9 3.4 1.7 --

7 41 18 11 7.3 4.4 --

14 49 26 19 14 10 --

30 56 30 22 17 12 --

Duration of daily mean flows based on 28 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

0.84 1.6 4.4 12 34 58 82 114

40% 30% 20% 15% 10% 5% 2% 1%

165 250 517 877 1,410 2,970 5,970 9,150

Magnitude and probability of annual high flow

based on 28 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 7,090 16,500 23,100 30,900 36,100 --

3 6,320 15,300 21,600 28,900 33,600 --

7 5,320 13,200 18,900 25,700 30,100 --

15 3,880 9,780 14,300 19,900 23,800 --

30 2,530 6,320 9,240 13,000 15,600 --

60 1,690 4,080 5,890 8,180 9,790 --

90 1,420 3,210 4,450 5,890 6,840 --

Magnitude and probability of seasonal low flow from

July-October based on 27 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 5.1 0.94 0.00 0.00 0.00 --

3 6.3 1.5 .42 .00 .00 --

7 7.4 1.8 .56 .00 .00 --

14 12 3.5 1.6 .51 .00 --

30 26 7.6 3.7 2.0 .91 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 4,640 9.5 315 846 29

November 660 47 165 112 29

December 456 26 106 81 29

January 1,440 20 134 258 29

February 2,160 15 287 443 29

March 6,900 43 1,550 1,800 29

April 13,600 1.5 2,190 3,020 29

May 4,120 2.1 884 1,210 29

June 6,570 1.9 1,060 1,380 28

July 4,560 4.4 494 927 28

August 1,100 5.9 178 263 28

September 1,320 5.7 185 264 29

Annual 1,680 39 618 454 28
Statistical Summaries of Streamflow 147

06174500 Milk River at Nashua, Mont.

Site Number 126

LOCATION.--Lat 48°07'47", long 106°21'50" (NAD 27), in NE1⁄4NE1⁄4 sec.1, T.27 N., R.41 E., Valley County, Hydrologic Unit 10050012, on right bank at 

downstream side of former highway bridge site, 0.6 mi southwest of Nashua, 2.0 mi upstream from Porcupine Creek, and at river mile 22.7.

DRAINAGE AREA.--22,332 mi2.

PERIOD OF RECORD.--October 1939 to current year (2002).

REVISED RECORDS.--WSP 1729: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 2,027.75 ft (NGVD 29).

REMARKS.--Flow increased during irrigation season by water from St. Mary Canal which diverts from the St. Mary River near Babb. Flow regulated by Fresno 

Reservoir (station number 06136500), two reservoirs in Lodge Creek basin in Saskatchewan, and four reservoirs in Frenchman River basin in Saskatchewan. 

Diversions for irrigation of about 140,000 acres upstream from station. U.S. Army Corps of Engineers satellite telemeter at station.

Magnitude and probability of annual low flow

based on 62 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 44 12 3.1 0.00 0.00 0.00

3 54 15 4.4 .79 .00 .00

7 55 16 5.1 1.1 .00 .00

14 72 22 7.2 2.0 .06 .00

30 88 35 17 8.5 3.4 1.7

60 113 54 31 17 8.0 4.5

90 126 71 48 33 20 14

120 143 81 56 40 26 20

183 158 91 68 53 40 33

Magnitude and probability of seasonal low flow from

March-June based on 63 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 61 17 5.9 0.29 0.00 0.00

3 68 19 6.9 1.4 .00 .00

7 76 21 8.2 3.1 .30 .00

14 108 29 11 4.0 1.1 .40

30 165 54 28 15 7.3 4.3

Magnitude and probability of seasonal low flow from

November-February based on 62 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 73 48 38 32 26 22

3 77 51 41 34 28 24

7 84 55 44 37 30 26

14 92 61 48 40 32 28

30 105 70 55 45 36 31

Duration of daily mean flows based on 63 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

11 20 37 57 90 119 149 181

40% 30% 20% 15% 10% 5% 2% 1%

235 329 528 756 1,310 3,040 6,310 8,540

Magnitude and probability of annual high flow

based on 63 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 5,490 11,700 16,200 21,800 25,600 29,200

3 5,240 11,300 15,700 20,900 24,600 28,000

7 4,600 10,400 14,800 20,300 24,300 28,000

15 3,630 8,610 12,600 17,900 21,900 25,700

30 2,480 5,990 8,910 13,000 16,200 19,500

60 1,580 3,780 5,650 8,370 10,600 12,900

90 1,240 2,900 4,340 6,470 8,240 10,100

Magnitude and probability of seasonal low flow from

July-October based on 62 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 62 21 9.6 4.1 0.50 0.00

3 68 24 11 4.9 .64 .00

7 80 29 14 6.1 .82 .00

14 94 38 20 10 2.2 .00

30 142 54 26 13 5.0 2.4

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 6,840 34 307 849 63

November 768 61 213 134 63

December 487 40 158 78 63

January 843 36 147 112 63

February 2,340 39 241 324 63

March 6,680 56 1,270 1,490 63

April 20,900 15 2,220 3,400 63

May 5,210 10 995 1,400 63

June 6,610 28 957 1,100 63

July 3,580 3.6 671 770 63

August 1,750 3.4 310 291 63

September 2,140 13 276 319 63

Annual 2,360 58 647 485 63
148 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06176500 Wolf Creek near Wolf Point, Mont.

Site Number 127

LOCATION.--Lat 48°05'47", long 105°40'41" (NAD 27), in NE1⁄4SE1⁄4NW1⁄4 sec.17, T.27 N., R.47 E., Roosevelt County, Hydrologic Unit 10060001, on right 

bank 0.5 mi north of U.S. Highway 2, 1.5 mi west of Wolf Point, and at river mile 2.3. 

DRAINAGE AREA.--251 mi2. 

PERIOD OF RECORD.--August 1908 to July 1914 (no winter records 1909, 1913-14), March 1950 to September 1953, water years 1954, 1956-73 (annual 

maximums), October 1981 to September 1992 (discontinued). Monthly discharge only for some periods, published in WSP 1309. 

REVISED RECORDS.--WSP 1729: Drainage area. 

GAGE.--Water-stage recorder. Altitude of gage is 2,000 ft (NGVD 29, from topographic map). Prior to July 31, 1914, nonrecording gage at site 0.8 mi upstream 

at different datum. Aug. 1, 1914, to Sept. 30, 1953, water-stage recorder at same site and datum. May 1955 to September 1973, crest-stage gage at same site 

and datum. 

REMARKS.--Minor diversion for irrigation upstream from station. 

Magnitude and probability of annual low flow

based on 15 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.00 0.00 0.00 0.00 -- --

3 .00 .00 .00 .00 -- --

7 .00 .00 .00 .00 -- --

14 .00 .00 .00 .00 -- --

30 .00 .00 .00 .00 -- --

60 .00 .00 .00 .00 -- --

90 .00 .00 .00 .00 -- --

120 .00 .00 .00 .00 -- --

183 .02 .00 .00 .00 -- --

Magnitude and probability of seasonal low flow from

March-June based on 17 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.00 0.00 0.00 0.00 -- --

3 .00 .00 .00 .00 -- --

7 .00 .00 .00 .00 -- --

14 .05 .00 .00 .00 -- --

30 .51 .01 .00 .00 -- --

Magnitude and probability of seasonal low flow from

November-February based on 17 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.00 0.00 0.00 0.00 -- --

3 .00 .00 .00 .00 -- --

7 .00 .00 .00 .00 -- --

14 .00 .00 .00 .00 -- --

30 .00 .00 .00 .00 -- --

Duration of daily mean flows based on 17 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

0.02 0.03 0.08 0.16 0.32 0.48 0.64 0.80

40% 30% 20% 15% 10% 5% 2% 1%

0.96 1.8 4.2 6.3 9.6 21 64 113

Magnitude and probability of annual high flow

based on 17 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 89 638 1,630 4,110 -- --

3 70 448 1,060 2,480 -- --

7 52 288 625 1,310 -- --

15 36 181 365 702 -- --

30 25 110 207 367 -- --

60 17 63 108 170 -- --

90 13 45 74 112 -- --

Magnitude and probability of seasonal low flow from

July-October based on 19 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.00 0.00 0.00 0.00 -- --

3 .00 .00 .00 .00 -- --

7 .00 .00 .00 .00 -- --

14 .00 .00 .00 .00 -- --

30 .00 .00 .00 .00 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 7.1 0.00 0.88 1.7 20

November 6.0 .00 .83 1.4 20

December 2.0 .00 .52 .73 18

January 1.1 .00 .24 .39 17

February 56 .00 4.3 13 17

March 143 .00 23 40 17

April 235 .10 28 55 21

May 20 .08 6.2 6.5 21

June 49 .00 7.1 12 21

July 45 .00 5.6 11 21

August 8.4 .00 .84 2.2 21

September 55 .00 3.0 12 21

Annual 21 .02 6.9 6.7 17
Statistical Summaries of Streamflow 149

06177000 Missouri River near Wolf Point, Mont.

Site Number 128

LOCATION.--Lat 48°04'00", long 105°31'55" (NAD 27), in SW1⁄4NW1⁄4 sec.28, T.27 N., R.48 E., McCone County, Hydrologic Unit 10060001, on right bank 

500 ft downstream from bridge on State Highway 13, 5 mi southeast of Wolf Point, 7.8 mi downstream from Wolf Creek, and at river mile 1,701.4.

DRAINAGE AREA.--82,290 mi2.

PERIOD OF RECORD.--September 1928 to current year (2002).

REVISED RECORDS.--WSP 1146: 1931. WSP 1729: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 1,958.57 ft (NGVD 29). Prior to Apr. 13, 1930, nonrecording gages at Wolf Point ferry landing 5.5 mi upstream 

at different datum.

REMARKS.--Flow partly regulated by Fort Peck Lake and many other reservoirs upstream from station. Diversion for irrigation of about 1,010,400 acres upstream 

from station. U.S. Army Corps of Engineers satellite telemeter at station. 

Magnitude and probability of annual low flow

based on 57 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 4,370 2,560 1,800 1,300 862 638

3 4,620 2,760 1,970 1,440 970 728

7 4,880 2,980 2,170 1,620 1,120 856

14 5,090 3,240 2,450 1,890 1,380 1,100

30 5,500 3,690 2,880 2,300 1,750 1,440

60 6,430 4,330 3,360 2,650 1,960 1,580

90 7,190 4,860 3,720 2,890 2,100 1,660

120 7,940 5,400 4,110 3,160 2,250 1,740

183 8,820 6,400 5,280 4,450 3,620 3,120

Magnitude and probability of seasonal low flow from

March-June based on 58 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 5,160 3,060 2,190 1,600 1,090 822

3 5,400 3,230 2,320 1,700 1,160 878

7 5,680 3,430 2,480 1,830 1,260 954

14 5,950 3,680 2,730 2,070 1,480 1,160

30 6,490 4,170 3,180 2,490 1,850 1,490

Magnitude and probability of seasonal low flow from

November-February based on 57 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 5,570 3,180 2,180 1,530 974 699

3 5,820 3,360 2,340 1,670 1,090 793

7 6,100 3,580 2,530 1,830 1,220 904

14 6,470 3,870 2,770 2,030 1,420 1,130

30 7,200 4,520 3,320 2,470 1,780 1,470

Duration of daily mean flows based on 58 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

1,430 2,260 3,580 4,670 6,190 7,140 8,090 9,220

40% 30% 20% 15% 10% 5% 2% 1%

10,700 12,200 14,300 15,400 16,500 21,400 27,700 31,800

Magnitude and probability of annual high flow

based on 58 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 18,400 25,200 29,900 36,100 40,900 45,900

3 18,000 24,600 29,100 35,200 39,900 44,700

7 17,400 23,800 28,200 33,900 38,400 43,000

15 16,600 22,900 27,200 33,000 37,400 42,100

30 15,600 21,500 25,700 31,300 35,700 40,300

60 14,300 19,400 23,000 27,800 31,500 35,300

90 13,300 17,500 20,400 24,200 27,000 29,900

Magnitude and probability of seasonal low flow from

July-October based on 57 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 5,840 3,640 2,800 2,230 1,720 1,440

3 6,200 3,870 2,970 2,360 1,810 1,500

7 6,560 4,070 3,110 2,460 1,870 1,540

14 6,860 4,280 3,290 2,610 2,000 1,660

30 7,720 4,810 3,660 2,880 2,160 1,770

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 29,100 3,150 11,400 7,090 58

November 22,200 2,330 9,170 4,130 58

December 12,100 1,500 9,070 2,350 58

January 14,300 1,420 9,880 3,100 58

February 15,800 1,350 10,200 3,960 58

March 16,800 2,300 9,110 3,680 58

April 27,200 1,470 9,720 5,030 58

May 21,800 1,180 9,510 4,120 58

June 26,000 1,270 9,630 4,460 58

July 36,300 1,170 10,600 5,450 58

August 27,100 3,520 12,000 5,790 58

September 27,200 3,270 11,700 6,540 58

Annual 15,800 5,630 10,200 2,790 58
150 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06177500 Redwater River at Circle, Mont.

Site Number 129

LOCATION.--Lat 47°24'51", long 105°34'30" (NAD 27), in SW1⁄4SW1⁄4 sec.11, T.19 N., R.48 E., McCone County, Hydrologic Unit 10060002, on left bank at 

Circle, 1 mi upstream from Horse Creek, and at river mile 110.2.

DRAINAGE AREA.--547 mi2.

PERIOD OF RECORD.--April to November 1929, March to November 1930, July 1931 to December 1932, March to June 1933, February to November 1934, 

April 1935 to December 1936, April 1937 to June 1972, October 1974 to current year (2002). Monthly discharge only for some periods, published in WSP 

1309. Prior to October 1967, published as "Redwater Creek at Circle."

REVISED RECORDS.--WSP 1006: 1929-30, 1932-33, 1935-39. WSP 1509: 1929, 1934. WSP 1729: Drainage area.

GAGE.--Water-stage recorder. Sharp-crested weir since Sept. 24, 1938. Altitude of gage is 2,394.32 ft (NGVD 29, levels by U.S. Army Corps of Engineers). 

Prior to June 1, 1941, and Mar. 23, 1943, to Feb. 16, 1948, nonrecording gage at site 0.3 mi upstream at same datum. June 1, 1941, to Mar. 22, 1943, 

nonrecording gage at site 200 ft upstream at datum 2.8 ft lower. Feb. 26, 1948, to May 7, 1950, nonrecording gage at site 200 ft upstream at present datum.

REMARKS.--Diversions for irrigation of about 1,200 acres upstream from station. U.S. Geological Survey satellite telemeter at station. 

Magnitude and probability of annual low flow

based on 61 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.00 0.00 0.00 0.00 0.00 0.00

3 .00 .00 .00 .00 .00 .00

7 .00 .00 .00 .00 .00 .00

14 .00 .00 .00 .00 .00 .00

30 .00 .00 .00 .00 .00 .00

60 .02 .00 .00 .00 .00 .00

90 .04 .00 .00 .00 .00 .00

120 .06 .01 .00 .00 .00 .00

183 .08 .02 .01 .00 .00 .00

Magnitude and probability of seasonal low flow from

March-June based on 68 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.05 0.00 0.00 0.00 0.00 0.00

3 .07 .00 .00 .00 .00 .00

7 .14 .02 .00 .00 .00 .00

14 .25 .05 .01 .00 .00 .00

30 .59 .15 .07 .03 .01 .01

Magnitude and probability of seasonal low flow from

November-February based on 65 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.00 0.00 0.00 0.00 0.00 0.00

3 .00 .00 .00 .00 .00 .00

7 .00 .00 .00 .00 .00 .00

14 .00 .00 .00 .00 .00 .00

30 .02 .00 .00 .00 .00 .00

Duration of daily mean flows based on 64 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

0.01 0.03 0.07 0.14 0.29 0.43 0.58 0.72

40% 30% 20% 15% 10% 5% 2% 1%

0.87 1.1 2.4 3.9 7.1 20 86 230

Magnitude and probability of annual high flow

based on 64 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 252 1,350 2,900 6,070 9,390 13,500

3 184 909 1,870 3,740 5,610 7,870

7 118 526 1,030 1,950 2,820 3,830

15 71 290 545 989 1,400 1,860

30 43 164 295 513 704 913

60 26 93 162 269 359 454

90 19 67 113 185 243 303

Magnitude and probability of seasonal low flow from

July-October based on 69 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.00 0.00 0.00 0.00 0.00 0.00

3 .00 .00 .00 .00 .00 .00

7 .00 .00 .00 .00 .00 .00

14 .00 .00 .00 .00 .00 .00

30 .02 .00 .00 .00 .00 .00

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 19 0.00 0.52 2.3 70

November 7.1 .00 .37 .94 70

December 8.6 .00 .44 1.2 67

January 6.1 .00 .36 .92 65

February 141 .00 15 32 66

March 476 .05 73 112 68

April 418 .07 17 56 70

May 32 .02 3.7 5.4 71

June 167 .00 15 31 71

July 116 .00 11 26 70

August 37 .00 2.0 6.0 70

September 139 .00 2.4 17 70

Annual 62 .04 12 13 64
Statistical Summaries of Streamflow 151

06178500 East Poplar River at international boundary

(International gaging station)

Site Number 130

LOCATION.--Lat 49°00'00", long 105°24'32" (NAD 27), in SW1⁄4SW1⁄4 sec.3, T.1 N., R.26 W., second meridian, in Saskatchewan, Hydrologic Unit 10060003, 

on left bank 10 ft north of international boundary, 400 ft southwest of Canadian East Poplar Port of Entry, 14 mi north of Scobey, Mont., and at river mile 21.9.

DRAINAGE AREA.--541 mi2.

PERIOD OF RECORD.--March 1931 to current year (2002; seasonal records only in most seasons prior to October 1974). Prior to March 1962, published as "East 

Fork Poplar River at international boundary."

REVISED RECORDS.--WSP 1389: 1932, 1939, 1942-43, 1947. WDR-MT-83: Drainage area.

GAGE.--Water-stage recorder and concrete control. Altitude of gage is 2,410.92 ft (International Boundary Commission Survey Datum). Prior to Oct. 5, 1953, 

water-stage recorder at site 80 ft upstream at same datum.

REMARKS.--U.S. Geological Survey satellite telemeter at station. After September 1975 flow regulated by Morrison Dam at Cookson Reservoir 3.1 mi upstream.

Magnitude and probability of annual low flow

based on 27 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1.4 1.0 0.85 0.72 0.60 --

3 1.5 1.2 1.0 .87 .75 --

7 1.7 1.3 1.1 .93 .78 --

14 1.8 1.3 1.1 .98 .82 --

30 2.0 1.5 1.3 1.1 .94 --

60 2.0 1.6 1.4 1.3 1.1 --

90 2.1 1.7 1.6 1.5 1.4 --

120 2.1 1.8 1.7 1.6 1.5 --

183 2.3 1.9 1.8 1.6 1.5 --

Magnitude and probability of seasonal low flow from

March-June based on 27 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1.8 1.4 1.1 0.96 0.77 --

3 2.0 1.5 1.3 1.1 .91 --

7 2.1 1.7 1.4 1.2 1.0 --

14 2.4 1.8 1.6 1.3 1.1 --

30 2.8 2.0 1.8 1.7 1.6 --

Magnitude and probability of seasonal low flow from

November-February based on 27 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1.6 1.0 0.87 0.73 0.43 --

3 1.7 1.2 1.0 .89 .51 --

7 1.8 1.3 1.1 .95 .58 --

14 1.9 1.4 1.2 1.0 .63 --

30 2.0 1.6 1.3 1.1 .68 --

Duration of daily mean flows based on 27 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

0.55 1.0 1.5 1.6 2.0 2.2 2.4 2.6

40% 30% 20% 15% 10% 5% 2% 1%

2.8 3.4 3.9 5.1 7.9 21 66 145

Magnitude and probability of annual high flow

based on 27 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 23 116 345 1,340 3,610 --

3 20 98 285 1,070 2,810 --

7 18 83 230 809 2,010 --

15 15 63 157 480 1,080 --

30 13 46 105 292 609 --

60 9.4 31 69 180 360 --

90 7.7 24 51 127 248 --

Magnitude and probability of seasonal low flow from

July-October based on 27 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1.8 1.4 1.2 0.99 0.83 --

3 1.9 1.5 1.4 1.3 1.1 --

7 2.0 1.7 1.5 1.4 1.3 --

14 2.1 1.8 1.6 1.5 1.4 --

30 2.2 1.8 1.7 1.6 1.4 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 4.6 0.76 2.5 0.74 27

November 4.4 .58 2.4 .68 27

December 4.4 .63 2.2 .69 27

January 4.4 1.3 2.2 .69 27

February 8.0 .93 2.8 1.5 27

March 280 1.9 27 60 27

April 306 1.8 30 71 27

May 41 3.0 12 9.4 27

June 101 1.7 8.9 19 27

July 109 1.8 6.8 20 27

August 14 1.6 2.8 2.3 27

September 4.1 1.5 2.5 .57 27

Annual 51 2.1 8.5 12 27
152 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06181000 Poplar River near Poplar, Mont.

Site Number 131

LOCATION.--Lat 48°10'15", long 105°10'42" (NAD 27), in NE1⁄4NE1⁄4 sec.19, T.28 N., R.51 E., Roosevelt County, Hydrologic Unit 10060003, on right bank 4 mi 

north of Poplar, and at river mile 11.0.

DRAINAGE AREA.---3,174 mi2.

PERIOD OF RECORD.--August 1908 to October 1924, August 1947 to September 1969, June 1975 to September 1979, October 1981 to current year (2002). 

Monthly discharge only for some periods, published in WSP 1309.

REVISED RECORDS.--WSP 1176: 1948. WSP 1389: 1911. WSP 1729: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 1,953.16 ft (NGVD 29). Prior to May 1, 1911, nonrecording gage at site 4.2 mi upstream at different datum. 

May 1, 1911, to Oct. 4, 1913, nonrecording gage at site 14 mi upstream at different datum. Oct. 5, 1913, to Oct. 31, 1924, nonrecording gage at site 2.2 mi 

upstream at different datum. Aug. 10, 1947, to Sept. 30, 1969, water-stage recorder at present site and datum.

REMARKS.--Diversions for irrigation of about 5,500 acres upstream from station. Flow partially regulated by Coronach Dam, on the East Fork Poplar River, 2 mi 

north of international boundary. U.S. Geological Survey satellite telemeter at station.

Magnitude and probability of annual low flow

based on 60 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1.0 0.10 0.00 0.00 0.00 0.00

3 1.1 .13 .00 .00 .00 .00

7 1.3 .16 .00 .00 .00 .00

14 1.8 .24 .03 .00 .00 .00

30 2.9 .41 .10 .02 .00 .00

60 4.8 1.2 .48 .21 .07 .03

90 8.7 3.6 2.1 1.3 .68 .43

120 13 6.5 4.3 3.0 1.9 1.4

183 16 8.2 5.4 3.8 2.4 1.8

Magnitude and probability of seasonal low flow from

March-June based on 63 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 6.7 1.2 0.41 0.14 0.01 0.00

3 7.0 1.3 .42 .14 .01 .00

7 8.4 1.5 .53 .20 .06 .03

14 13 2.9 1.1 .45 .15 .07

30 40 12 4.5 1.8 .51 .20

Magnitude and probability of seasonal low flow from

November-February based on 63 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 2.5 0.36 0.05 0.00 0.00 0.00

3 2.6 .43 .10 .00 .00 .00

7 2.9 .51 .13 .00 .00 .00

14 3.3 .61 .18 .04 .00 .00

30 4.2 .91 .31 .11 .01 .00

Duration of daily mean flows based on 63 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

0.18 0.36 0.89 2.9 7.5 12 17 23

40% 30% 20% 15% 10% 5% 2% 1%

33 49 83 115 182 373 873 1,790

Magnitude and probability of annual high flow

based on 63 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 1,730 5,710 10,600 20,200 30,700 44,400

3 1,460 4,810 8,940 17,300 26,600 39,000

7 1,120 3,450 6,190 11,500 17,300 24,800

15 792 2,240 3,870 6,960 10,200 14,400

30 540 1,390 2,270 3,860 5,440 7,400

60 346 820 1,290 2,100 2,870 3,820

90 263 592 905 1,420 1,910 2,480

Magnitude and probability of seasonal low flow from

July-October based on 62 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 6.0 1.2 0.30 0.00 0.00 0.00

3 6.5 1.3 .36 .00 .00 .00

7 7.1 1.5 .43 .00 .00 .00

14 7.7 1.7 .52 .01 .00 .00

30 11 2.1 .55 .14 .02 .01

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 82 2.2 28 20 64

November 94 4.2 27 16 63

December 50 1.3 16 10 63

January 30 .01 8.5 7.4 63

February 743 .10 27 94 63

March 2,440 .18 332 496 63

April 4,920 37 672 1,010 63

May 421 17 123 102 63

June 336 2.8 86 75 64

July 800 .68 78 111 64

August 220 .04 28 37 66

September 206 .15 24 30 66

Annual 435 14 120 99 63
Statistical Summaries of Streamflow 153

06182500 Big Muddy Creek at Daleview, Mont.

Site Number 132

LOCATION.--Lat 48°54'40", long 104°56'42" (NAD 27), near center of north line of sec.5, T.36 N., R.52 E., Sheridan County, on right bank 0.5 mi west of 

Daleview, 0.5 mi upstream from Whitetail Creek, 6 mi north of Redstone, and at river mile 149.6.

DRAINAGE AREA.--279 mi2. 

PERIOD OF RECORD.--24 years (1947-71).

REVISED RECORDS.--WSP 1209: 1948(M). WSP 1309: Drainage area. WSP 1389: 1948. WSP 1559: 1955.

GAGE.--Water-stage recorder. Altitude of gage is 2,120 ft (NGVD 29, by barometer).

REMARKS.--Diversions for irrigation of about 90 acres upstream from station.

Magnitude and probability of annual low flow

based on 24 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.00 0.00 0.00 0.00 -- --

3 .00 .00 .00 .00 -- --

7 .00 .00 .00 .00 -- --

14 .00 .00 .00 .00 -- --

30 .00 .00 .00 .00 -- --

60 .06 .00 .00 .00 -- --

90 .34 .09 .04 .02 -- --

120 .72 .45 .35 .28 -- --

183 .92 .62 .52 .46 -- --

Magnitude and probability of seasonal low flow from

March-June based on 25 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.00 0.00 0.00 0.00 0.00 --

3 .00 .00 .00 .00 .00 --

7 .00 .00 .00 .00 .00 --

14 .48 .00 .00 .00 .00 --

30 2.6 .59 .18 .05 .01 --

Magnitude and probability of seasonal low flow from

November-February based on 25 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.00 0.00 0.00 0.00 0.00 --

3 .00 .00 .00 .00 .00 --

7 .00 .00 .00 .00 .00 --

14 .00 .00 .00 .00 .00 --

30 .00 .00 .00 .00 .00 --

Duration of daily mean flows based on 24 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

0.03 0.05 0.13 0.26 0.52 0.78 1.1 1.5

40% 30% 20% 15% 10% 5% 2% 1%

2.1 3.0 5.2 7.6 14 36 132 339

Magnitude and probability of annual high flow

based on 24 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 759 1,810 2,770 4,250 -- --

3 543 1,260 1,900 2,860 -- --

7 329 737 1,100 1,660 -- --

15 186 402 600 918 -- --

30 110 227 330 491 -- --

60 61 122 174 254 -- --

90 44 85 118 167 -- --

Magnitude and probability of seasonal low flow from

July-October based on 24 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.00 0.00 0.00 0.00 -- --

3 .00 .00 .00 .00 -- --

7 .00 .00 .00 .00 -- --

14 .11 .00 .00 .00 -- --

30 .32 .00 .00 .00 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 8.1 0.90 2.1 1.5 25

November 3.7 .84 1.8 .68 25

December 3.5 .01 .90 .85 25

January 3.5 .00 .39 .72 25

February 38 .00 3.2 8.5 25

March 282 .04 53 75 25

April 534 4.3 100 141 25

May 59 2.0 12 14 25

June 96 .84 13 22 25

July 26 .46 3.9 6.1 24

August 19 .00 2.2 3.9 24

September 10 .00 1.8 2.5 25

Annual 45 3.3 16 11 24
154 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06183450 Big Muddy Creek near Antelope, Mont.

Site Number 133

LOCATION.--Lat 48°40'22", long 104°30'42" (NAD 27), in SW1⁄4SW1⁄4NW1⁄4 sec.27, T.34 N., R.55 E., Sheridan County, Hydrologic Unit 10060006, on right 

bank, 3 mi southwest of Antelope, and 7 mi south of Plentywood.

DRAINAGE AREA.--967 mi2. Prior to 1981, drainage area published as 1,171 mi2.

PERIOD OF RECORD.--October 1978 to current year (2002).

REVISED RECORDS.--WDR MT-81-1: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 2,000 ft (NGVD 29).

REMARKS.--Several known diversions for irrigation upstream from station. U.S. Geological Survey satellite telemeter at station. 

Magnitude and probability of annual low flow

based on 23 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.02 0.00 0.00 0.00 -- --

3 .05 .00 .00 .00 -- --

7 .07 .00 .00 .00 -- --

14 .13 .00 .00 .00 -- --

30 .19 .00 .00 .00 -- --

60 .61 .08 .00 .00 -- --

90 1.5 .55 .25 .05 -- --

120 2.5 1.0 .56 .30 -- --

183 3.4 1.7 1.1 .71 -- --

Magnitude and probability of seasonal low flow from

March-June based on 24 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.92 0.20 0.00 0.00 -- --

3 1.0 .23 .00 .00 -- --

7 1.8 .28 .00 .00 -- --

14 3.2 .84 .35 .15 -- --

30 6.1 2.2 1.2 .67 -- --

Magnitude and probability of seasonal low flow from

November-February based on 23 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.45 0.00 0.00 0.00 -- --

3 .48 .00 .00 .00 -- --

7 .54 .08 .00 .00 -- --

14 .79 .09 .00 .00 -- --

30 .86 .18 .00 .00 -- --

Duration of daily mean flows based on 24 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

0.05 0.10 0.26 0.52 1.1 2.0 3.2 4.7

40% 30% 20% 15% 10% 5% 2% 1%

6.6 10 18 26 39 90 307 609

Magnitude and probability of annual high flow

based on 24 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 600 1,510 2,370 3,750 -- --

3 506 1,320 2,130 3,490 -- --

7 364 990 1,660 2,860 -- --

15 226 635 1,090 1,940 -- --

30 138 374 628 1,090 -- --

60 86 219 356 596 -- --

90 63 156 251 419 -- --

Magnitude and probability of seasonal low flow from

July-October based on 23 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.15 0.00 0.00 0.00 -- --

3 .21 .00 .00 .00 -- --

7 .23 .02 .00 .00 -- --

14 .26 .03 .00 .00 -- --

30 .44 .05 .01 .00 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 25 0.14 5.3 5.4 24

November 12 .88 5.9 2.9 24

December 6.9 .45 3.6 2.0 24

January 6.4 .00 1.8 1.6 24

February 290 .00 25 62 24

March 851 2.7 133 197 24

April 826 5.0 116 220 24

May 120 5.3 25 29 24

June 62 .23 16 18 24

July 226 .03 26 47 24

August 92 .00 9.1 19 24

September 36 .00 4.5 7.5 24

Annual 93 4.7 31 28 24
Statistical Summaries of Streamflow 155

06185000 Big Muddy Creek near Culbertson, Mont.

Site Number 134

LOCATION.--Lat 48°15'26", long 104°43'25" (NAD 27), in NE1⁄4 sec.20, T.29 N., R.54 E., Roosevelt County, 11 mi upstream from mouth and 12 mi northwest 

of Culbertson.

DRAINAGE AREA.--2,447 mi2.

PERIOD OF RECORD.--13 years (1908-21).

GAGE.--Wire-weight gage. Altitude of gage is 1,910 ft (NGVD 29, from topographic map). July 19, 1909, to Sept. 16, 1918, slope gage at same datum. Prior to 

July 19, 1909, staff gage at site 8 mi downstream at different datum.

REMARKS.--Several small diversions upstream from station.

Magnitude and probability of annual low flow

based on 12 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.00 0.00 0.00 0.00 -- --

3 .00 .00 .00 .00 -- --

7 .00 .00 .00 .00 -- --

14 .00 .00 .00 .00 -- --

30 .60 .00 .00 .00 -- --

60 1.2 .00 .00 .00 -- --

90 1.9 .00 .00 .00 -- --

120 2.4 .34 .03 .00 -- --

183 4.4 1.0 .39 .15 -- --

Magnitude and probability of seasonal low flow from

March-June based on 13 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 3.8 1.0 0.00 0.00 -- --

3 4.1 1.3 .00 .00 -- --

7 4.8 1.5 .00 .00 -- --

14 7.3 3.2 2.1 1.5 -- --

30 11 6.1 4.7 4.0 -- --

Magnitude and probability of seasonal low flow from

November-February based on 13 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1.7 0.00 0.00 0.00 -- --

3 1.8 .00 .00 .00 -- --

7 1.9 .00 .00 .00 -- --

14 2.0 .00 .00 .00 -- --

30 2.2 .00 .00 .00 -- --

Duration of daily mean flows based on 13 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

0.07 0.14 0.35 0.70 2.1 3.7 5.2 7.4

40% 30% 20% 15% 10% 5% 2% 1%

11 21 39 60 109 258 788 1,090

Magnitude and probability of annual high flow

based on 13 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 840 1,250 1,490 1,820 -- --

3 789 1,210 1,460 1,790 -- --

7 698 1,160 1,450 1,780 -- --

15 516 940 1,260 1,690 -- --

30 328 661 952 1,400 -- --

60 191 392 574 866 -- --

90 140 277 404 613 -- --

Magnitude and probability of seasonal low flow from

July-October based on 13 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.77 0.00 0.00 0.00 -- --

3 .82 .00 .00 .00 -- --

7 1.0 .22 .05 .00 -- --

14 1.3 .48 .22 .00 -- --

30 1.9 .74 .38 .00 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 35 0.00 8.4 8.6 14

November 11 .00 5.9 4.0 14

December 12 .00 3.9 3.5 13

January 10 .00 2.5 2.8 13

February 30 .00 3.7 8.0 13

March 359 10 116 139 13

April 1,210 47 369 373 13

May 246 3.7 68 77 13

June 249 6.9 59 71 13

July 143 2.0 44 47 13

August 45 .54 13 12 14

September 51 .44 11 16 14

Annual 170 19 58 43 13
156 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06185110 Big Muddy Creek near mouth, near Culbertson, Mont.

Site Number 135

LOCATION.--Lat 48°09'52", long 104°37'45" (NAD 27), in NE1⁄4NW1⁄4SW1⁄4 sec.21, T.28 N., R.55 E., Roosevelt County, Hydrologic Unit 10060006, Fort Peck 

Indian Reservation, on right bank 30 ft downstream from U.S. Highway 2 bridge and 5.3 mi northwest of Culbertson. 

DRAINAGE AREA.--2,684 mi2. 

PERIOD OF RECORD.--November 1981 to September 1992 (discontinued).

GAGE.--Water-stage recorder. Altitude of gage is 1,896.52 ft (NVGD 29).

REMARKS.--Flows are subject to extreme regulation by diversions and dams at Medicine Lake National Wildlife Refuge about 40 mi upstream. 

Magnitude and probability of annual low flow

based on 10 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.00 0.00 0.00 0.00 -- --

3 .00 .00 .00 .00 -- --

7 .00 .00 .00 .00 -- --

14 .00 .00 .00 .00 -- --

30 .01 .00 .00 .00 -- --

60 .09 .00 .00 .00 -- --

90 .23 .00 .00 .00 -- --

120 .66 .00 .00 .00 -- --

183 1.4 .24 .00 .00 -- --

Magnitude and probability of seasonal low flow from

March-June based on 11 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.00 0.00 0.00 0.00 -- --

3 .00 .00 .00 .00 -- --

7 .01 .00 .00 .00 -- --

14 .24 .00 .00 .00 -- --

30 1.6 .19 .01 .00 -- --

Magnitude and probability of seasonal low flow from

November-February based on 10 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.00 0.00 0.00 0.00 -- --

3 .00 .00 .00 .00 -- --

7 .00 .00 .00 .00 -- --

14 .03 .00 .00 .00 -- --

30 .07 .00 .00 .00 -- --

Duration of daily mean flows based on 11 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

0.02 0.04 0.11 0.21 0.43 0.64 0.85 1.2

40% 30% 20% 15% 10% 5% 2% 1%

2.9 5.6 11 18 36 94 231 352

Magnitude and probability of annual high flow

based on 11 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 77 360 857 -- -- --

3 64 304 743 -- -- --

7 50 236 585 -- -- --

15 39 188 480 -- -- --

30 30 142 358 -- -- --

60 22 100 243 -- -- --

90 17 76 184 -- -- --

Magnitude and probability of seasonal low flow from

July-October based on 10 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.00 0.00 0.00 0.00 -- --

3 .00 .00 .00 .00 -- --

7 .00 .00 .00 .00 -- --

14 .00 .00 .00 .00 -- --

30 .04 .00 .00 .00 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 39 0.00 7.5 13 11

November 6.6 .00 2.5 2.6 11

December 5.3 .00 1.3 1.9 11

January 1.6 .00 .49 .59 11

February 5.4 .00 1.5 2.0 11

March 254 .18 34 74 11

April 779 .63 96 228 11

May 422 .46 55 125 11

June 235 .00 27 69 11

July 110 .00 20 34 11

August 58 .00 7.8 17 11

September 128 .00 14 38 11

Annual 141 .88 22 41 11
Statistical Summaries of Streamflow 157

06185500 Missouri River near Culbertson, Mont.

Site Number 136

LOCATION.--Lat 48°07'30", long 104°28'20" (NAD 27), in SE1⁄4NW1⁄4 sec.3, T.27 N., R.56 E., Richland County, Hydrologic Unit 10060005, on right bank at 

upstream side of bridge on State Highway 16, 2.5 mi southeast of Culbertson, 10 mi downstream from Big Muddy Creek, and at river mile 1,620.76.

DRAINAGE AREA.--91,557 mi2.

PERIOD OF RECORD.--July 1941 to December 1951, April 1958 to current year (2002).

REVISED RECORDS.--WSP 1729: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 1,883.4 ft (NGVD 29, U.S. Army Corps of Engineers bench mark). July 1 to Nov. 6, 1941, water-stage recorder 

at site 400 ft upstream at datum 0.11 ft higher. Nov. 7, 1941, to Aug. 17, 1950, water-stage recorder at site 580 ft downstream at present datum. Aug. 18, 1950, 

to Dec. 31, 1951, nonrecording gage on bridge at present datum. Apr. 1, 1958, to Nov. 1, 1967, water-stage recorder at site 580 ft downstream at present datum.

REMARKS.--Flow partly regulated by Fort Peck Lake (station number 06131500) and many other reservoirs upstream from station. Diversions for irrigation of 

about 1,030,400 acres upstream from station. U.S. Army Corps of Engineers satellite telemeter at station.

Magnitude and probability of annual low flow

based on 52 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 4,560 2,550 1,740 1,220 785 568

3 4,690 2,630 1,810 1,280 827 602

7 4,910 2,790 1,940 1,380 908 668

14 5,170 3,020 2,140 1,550 1,040 781

30 5,790 3,530 2,550 1,880 1,280 961

60 6,550 4,010 2,900 2,130 1,440 1,090

90 7,150 4,460 3,250 2,410 1,650 1,250

120 7,680 5,030 3,810 2,940 2,110 1,660

183 8,560 6,260 5,230 4,460 3,690 3,230

Magnitude and probability of seasonal low flow from

March-June based on 54 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 5,530 3,070 2,090 1,460 937 676

3 5,630 3,140 2,150 1,520 977 710

7 5,860 3,280 2,260 1,600 1,040 759

14 6,160 3,520 2,480 1,790 1,200 899

30 6,910 4,150 3,020 2,250 1,570 1,210

Magnitude and probability of seasonal low flow from

November-February based on 54 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 5,220 2,780 1,820 1,230 794 574

3 5,440 2,880 1,890 1,290 837 610

7 5,800 3,140 2,100 1,430 924 677

14 6,230 3,430 2,300 1,580 1,050 796

30 7,080 4,050 2,750 1,890 1,300 992

Duration of daily mean flows based on 54 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

1,230 1,460 2,890 4,420 6,230 7,250 8,270 9,510

40% 30% 20% 15% 10% 5% 2% 1%

10,900 12,400 14,500 15,500 16,600 20,700 24,700 30,600

Magnitude and probability of annual high flow

based on 54 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 19,300 28,100 35,400 46,600 56,600 68,000

3 18,800 26,800 33,200 42,600 50,700 59,800

7 18,100 25,300 30,700 38,300 44,600 51,500

15 17,200 23,300 27,700 33,800 38,600 43,700

30 15,900 21,200 25,000 30,200 34,400 38,700

60 14,400 18,900 22,100 26,400 29,800 33,300

90 13,300 17,100 19,800 23,300 26,100 28,900

Magnitude and probability of seasonal low flow from

July-October based on 55 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 5,960 3,380 2,380 1,720 1,150 866

3 6,140 3,480 2,440 1,760 1,180 883

7 6,450 3,650 2,550 1,830 1,220 907

14 6,760 3,880 2,740 2,000 1,350 1,020

30 7,350 4,380 3,180 2,380 1,670 1,290

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 28,600 1,240 10,700 5,930 55

November 22,400 1,130 9,260 4,420 55

December 13,300 1,060 9,140 2,830 55

January 14,400 1,010 9,910 3,480 54

February 17,400 1,170 10,500 4,400 54

March 20,700 2,670 10,400 4,330 54

April 32,800 1,960 10,500 5,590 55

May 26,200 1,350 9,540 4,770 55

June 26,600 1,370 9,740 4,780 55

July 37,000 1,270 10,200 5,340 56

August 25,300 3,820 11,400 4,720 56

September 26,600 3,770 11,100 5,440 56

Annual 16,600 4,080 10,200 2,860 54
158 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06186500 Yellowstone River at Yellowstone Lake outlet, Yellowstone National Park, Wyo.

Site Number 137

LOCATION.--Lat 44°34'03", long 110°22'48" (NAD 27), Yellowstone National Park, Hydrologic Unit 10070001, on left bank 450 ft downstream from Fishing 

Bridge, 0.3 mi downstream from outlet of Yellowstone Lake, and at river mile 616.4.

DRAINAGE AREA.--991 mi2.

PERIOD OF RECORD.--December 1922 to September 1982, October 1983 to September 1986, October 1988 to current year (2002). Prior to October 1926, gage 

heights only. Monthly discharge only for winter periods in water years 1927-30, 1932-33, 1935-38, 1940, 1942-46 published in WSP 1309; figures of daily 

discharge for these months published in WSP 646, 666, 686, 701, 731, 746, 786, 806, 826, 856, 896, 956, 976, 1006, 1036, and 1056, have been found to be 

unreliable and were not used in analysis.

REVISED RECORDS.--WSP 1309: See PERIOD OF RECORD. WSP 1729: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 7,729.58 ft (NGVD 29). Prior to Oct. 2, 1928, nonrecording gage at site 450 ft upstream at datum 1.07 ft higher.

REMARKS.--No diversion or regulation upstream from station. U.S. Geological Survey satellite telemeter at station. 

Magnitude and probability of annual low flow

based on 71 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 293 204 166 138 111 96

3 294 206 167 140 113 98

7 297 208 170 143 116 101

14 303 214 175 147 120 104

30 318 227 187 158 129 112

60 356 264 223 191 160 141

90 402 309 267 235 202 182

120 454 354 308 274 238 217

183 644 506 441 392 340 309

Magnitude and probability of seasonal low flow from

March-June based on 73 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 404 280 221 177 134 109

3 406 281 222 177 134 109

7 410 285 225 181 137 112

14 420 294 233 187 142 116

30 450 323 260 211 162 134

Magnitude and probability of seasonal low flow from

November-February based on 73 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 342 236 189 155 122 103

3 342 237 191 157 125 106

7 344 240 194 160 128 109

14 349 244 198 164 131 112

30 358 252 205 170 136 117

Duration of daily mean flows based on 73 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

167 200 265 328 427 510 607 708

40% 30% 20% 15% 10% 5% 2% 1%

909 1,310 2,130 2,770 3,570 4,700 5,890 7,010

Magnitude and probability of annual high flow

based on 73 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 4,780 6,310 7,230 8,300 9,050 9,750

3 4,770 6,300 7,210 8,280 9,020 9,720

7 4,740 6,250 7,160 8,230 8,970 9,660

15 4,660 6,140 7,030 8,070 8,800 9,480

30 4,450 5,820 6,630 7,580 8,230 8,840

60 3,890 5,000 5,650 6,380 6,870 7,320

90 3,320 4,230 4,740 5,320 5,710 6,060

Magnitude and probability of seasonal low flow from

July-October based on 71 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 671 532 468 420 370 339

3 679 538 474 425 374 343

7 693 549 484 434 382 350

14 718 570 501 449 396 363

30 785 621 543 484 423 386

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 1,260 327 800 213 73

November 984 276 606 162 73

December 775 246 475 134 73

January 700 168 398 135 73

February 637 122 387 133 73

March 717 130 446 133 73

April 801 175 543 118 73

May 2,210 604 1,160 391 73

June 8,570 1,710 3,700 1,220 73

July 7,160 1,270 4,050 1,380 73

August 4,030 812 2,210 723 73

September 1,950 538 1,210 344 73

Annual 2,250 682 1,340 318 73
Statistical Summaries of Streamflow 159

06187500 Tower Creek at Tower Falls, Yellowstone National Park, Wyo.

Site Number 138

LOCATION.--Lat 44°54', long 110°23' (NAD 27), just upstream from Tower Falls, 0.25 mi upstream from mouth and 2 mi southeast of Camp Roosevelt.

DRAINAGE AREA.--50.4 mi2.

PERIOD OF RECORD.--20 years (1923-43).

GAGE.--Staff gage. Altitude of gage is 6,400 ft (NGVD 29, from topographic map). Prior to Sept. 26, 1931, staff gage at site 25 ft downstream at datum 2.22 ft 

lower. Sept. 26, 1931, to July 11, 1933, staff gage at site 75 ft downstream at different datum. July 12, 1933, to Oct. 13, 1934, staff gage at described site and 

datum 0.50 ft higher. 

REMARKS.--No diversion or regulation upstream from station. 

Magnitude and probability of annual low flow

based on 19 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 14 11 9.3 7.8 -- --

3 14 12 10 9.4 -- --

7 14 12 11 9.7 -- --

14 14 12 11 9.8 -- --

30 15 12 11 9.9 -- --

60 16 13 12 11 -- --

90 17 15 13 12 -- --

120 18 16 14 13 -- --

183 21 18 17 16 -- --

Magnitude and probability of seasonal low flow from

March-June based on 20 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 16 13 10 8.4 -- --

3 16 13 11 10 -- --

7 16 13 12 10 -- --

14 16 13 12 11 -- --

30 17 14 12 11 -- --

Magnitude and probability of seasonal low flow from

November-February based on 20 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 15 13 11 10 -- --

3 15 13 11 10 -- --

7 15 13 11 10 -- --

14 15 13 11 10 -- --

30 16 13 11 10 -- --

Duration of daily mean flows based on 20 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

10 11 13 15 18 20 22 25

40% 30% 20% 15% 10% 5% 2% 1%

29 35 53 71 110 187 302 374

Magnitude and probability of annual high flow

based on 20 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 324 474 566 672 -- --

3 300 438 524 624 -- --

7 263 394 483 598 -- --

15 230 351 438 555 -- --

30 194 292 362 457 -- --

60 142 210 260 331 -- --

90 110 159 196 248 -- --

Magnitude and probability of seasonal low flow from

July-October based on 20 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 22 19 18 17 -- --

3 22 19 18 17 -- --

7 23 20 18 17 -- --

14 23 20 19 18 -- --

30 24 21 19 18 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 36 18 25 4.9 21

November 44 16 22 6.0 20

December 25 14 19 3.4 20

January 22 12 17 3.3 20

February 20 10 16 3.3 20

March 22 10 16 3.1 20

April 39 12 26 7.8 20

May 278 46 104 57 21

June 397 46 185 96 21

July 261 25 74 52 21

August 61 20 34 9.4 21

September 40 19 27 5.3 22

Annual 85 26 47 16 20
160 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06187950 Soda Butte Creek near Lamar Ranger Station, Yellowstone National Park, Wyo.

Site Number 139

LOCATION.--Lat 44°52'06", long 110°09'53" (NAD 27), Yellowstone National Park, Hydrologic Unit 10070001, on left bank, 4 mi southeast of Lamar Ranger 

Station, and at river mile 1.5.

DRAINAGE AREA.--99.0 mi2.

PERIOD OF RECORD.--October 1988 to current year (2002).

GAGE.--Water-stage recorder. Altitude of gage is 6,630 ft (NGVD 29).

REMARKS.--No regulation or diversion upstream from station. U.S. Geological Survey satellite telemeter at station.

Magnitude and probability of annual low flow

based on 13 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 17 14 13 12 -- --

3 18 15 14 12 -- --

7 19 16 15 14 -- --

14 21 18 16 15 -- --

30 22 19 18 17 -- --

60 25 21 19 18 -- --

90 26 22 20 18 -- --

120 28 24 22 20 -- --

183 36 31 28 26 -- --

Magnitude and probability of seasonal low flow from

March-June based on 14 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 19 15 14 13 -- --

3 20 16 14 13 -- --

7 20 17 15 14 -- --

14 21 19 17 16 -- --

30 23 20 19 18 -- --

Magnitude and probability of seasonal low flow from

November-February based on 13 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 18 15 13 12 -- --

3 19 15 14 12 -- --

7 20 17 15 14 -- --

14 21 18 17 16 -- --

30 22 19 18 17 -- --

Duration of daily mean flows based on 14 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

14 16 18 21 26 29 33 43

40% 30% 20% 15% 10% 5% 2% 1%

59 91 200 334 493 702 974 1,100

Magnitude and probability of annual high flow

based on 14 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 1,150 1,500 1,750 2,070 -- --

3 1,050 1,370 1,590 1,880 -- --

7 928 1,220 1,440 1,720 -- --

15 851 1,110 1,280 1,510 -- --

30 747 926 1,040 1,170 -- --

60 595 716 785 863 -- --

90 470 559 605 655 -- --

Magnitude and probability of seasonal low flow from

July-October based on 13 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 34 27 24 21 -- --

3 36 30 26 23 -- --

7 38 33 30 28 -- --

14 39 34 32 31 -- --

30 44 37 35 33 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 69 28 44 9.9 14

November 40 21 32 6.0 14

December 31 16 25 4.9 14

January 33 17 25 4.9 14

February 32 16 24 5.0 14

March 32 17 24 4.3 14

April 127 32 62 29 14

May 580 217 406 103 14

June 1,250 338 690 232 14

July 446 106 291 110 14

August 162 51 96 30 14

September 92 36 58 14 14

Annual 204 96 148 28 14
Statistical Summaries of Streamflow 161

06188000 Lamar River near Tower Falls Ranger Station, Yellowstone National Park, Wyo.

Site Number 140

LOCATION.--Lat 44°55'40", long 110°23'35" (NAD 27), Yellowstone National Park, Hydrologic Unit 10070001, on left bank 0.5 mi north of the Cooke City 

highway, 1.6 mi northeast of Tower Falls Ranger Station, 2.7 mi downstream from Slough Creek, and at river mile 0.5.

DRAINAGE AREA.--660 mi2.

PERIOD OF RECORD.--September 1922, April 1923 to September 1969, May 1985 to September 1986 (seasonal records only), October 1988 to current year 

(2002).

GAGE.--Water-stage recorder. Altitude of gage is 6,000 ft (NGVD 29). Prior to Sept. 16, 1925, nonrecording gage and Sept. 16, 1925, to July 29, 1927, waterstage recorder at same site at datum 1.00 ft higher. July 29, 1927, to Sept. 30, 1969, water-stage recorder at same site and datum. May 1985 to September 

1986, nonrecording gage at same site and datum.

REMARKS.--No regulation or diversion upstream from station. U.S. Geological Survey satellite telemeter at station. 

Magnitude and probability of annual low flow

based on 58 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 81 66 59 53 47 43

3 83 70 64 59 54 51

7 85 74 69 65 60 57

14 88 77 72 69 65 62

30 92 81 76 72 69 66

60 100 88 83 79 75 73

90 106 93 87 83 79 77

120 118 101 94 88 83 80

183 149 123 113 105 98 94

Magnitude and probability of seasonal low flow from

March-June based on 60 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 97 79 70 62 54 48

3 97 81 74 68 61 57

7 99 84 77 71 66 62

14 101 86 79 74 69 65

30 107 90 83 78 73 70

Magnitude and probability of seasonal low flow from

November-February based on 60 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 85 69 61 56 50 46

3 87 72 66 61 56 53

7 89 77 71 67 63 60

14 92 80 75 71 67 65

30 95 83 78 75 71 69

Duration of daily mean flows based on 60 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

68 71 79 92 110 127 157 189

40% 30% 20% 15% 10% 5% 2% 1%

259 430 1,110 1,930 2,990 4,520 6,590 8,040

Magnitude and probability of annual high flow

based on 60 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 7,600 9,700 11,000 12,700 13,800 15,000

3 7,060 9,070 10,400 12,000 13,300 14,500

7 6,400 8,290 9,540 11,100 12,300 13,500

15 5,560 7,280 8,430 9,910 11,000 12,200

30 4,780 6,130 7,010 8,130 8,950 9,780

60 3,690 4,630 5,230 5,970 6,510 7,050

90 2,830 3,540 3,970 4,490 4,850 5,210

Magnitude and probability of seasonal low flow from

July-October based on 59 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 148 120 109 101 93 88

3 152 124 112 104 96 92

7 157 127 116 108 100 96

14 165 133 121 112 104 100

30 178 142 129 119 111 106

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 485 109 213 87 60

November 330 88 157 50 60

December 202 76 120 26 60

January 200 72 106 22 60

February 171 70 102 20 60

March 204 68 113 28 60

April 1,680 106 465 341 60

May 6,880 970 2,850 1,120 63

June 9,040 1,410 4,260 1,590 63

July 3,260 344 1,350 695 63

August 886 173 352 135 63

September 518 115 229 82 64

Annual 1,530 525 867 215 60
162 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06189000 Blacktail Deer Creek near Mammoth, Yellowstone National Park, Wyo.

Site Number 141

LOCATION.--Lat 44°56'50", long 110°35'07" (NAD 27), Yellowstone National Park, Hydrologic Unit 10070001, on left bank 0.6 mi upstream from East Fork, 

0.7 mi upstream from culvert on Mammoth-Tower Falls highway, and 6.0 mi southeast of Mammoth. 

DRAINAGE AREA.--15.0 mi2. 

PERIOD OF RECORD.--December 1937 to October 1945, October 1988 to September 1993 (discontinued). 

GAGE.--Water-stage recorder. Altitude of gage is 6,680 ft (NGVD 29, from topographic map). December 1937 to October 1945, water-stage recorder and 

Cippoletti weir at site 300 ft downstream at different datum. 

REMARKS.--No diversion or regulation upstream from station. 

Magnitude and probability of annual low flow

based on 11 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1.3 0.95 0.78 0.66 -- --

3 1.4 1.0 .88 .77 -- --

7 1.4 1.1 1.0 .92 -- --

14 1.5 1.2 1.1 .98 -- --

30 1.5 1.3 1.1 1.1 -- --

60 1.7 1.4 1.3 1.2 -- --

90 1.8 1.5 1.3 1.2 -- --

120 2.1 1.6 1.4 1.2 -- --

183 2.5 2.0 1.7 1.5 -- --

Magnitude and probability of seasonal low flow from

March-June based on 13 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1.6 1.3 1.2 1.1 -- --

3 1.6 1.3 1.2 1.1 -- --

7 1.6 1.3 1.2 1.1 -- --

14 1.7 1.3 1.2 1.1 -- --

30 1.9 1.4 1.3 1.1 -- --

Magnitude and probability of seasonal low flow from

November-February based on 12 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1.4 1.0 0.82 0.68 -- --

3 1.4 1.1 .92 .79 -- --

7 1.5 1.2 1.1 .95 -- --

14 1.6 1.3 1.1 1.0 -- --

30 1.6 1.4 1.2 1.1 -- --

Duration of daily mean flows based on 12 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

1.0 1.1 1.2 1.5 1.8 2.2 2.6 3.2

40% 30% 20% 15% 10% 5% 2% 1%

4.0 5.6 11 17 23 35 57 78

Magnitude and probability of annual high flow

based on 12 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 62 104 138 -- -- --

3 57 94 124 -- -- --

7 51 86 114 -- -- --

15 44 72 95 -- -- --

30 37 57 74 -- -- --

60 30 43 53 -- -- --

90 24 34 41 -- -- --

Magnitude and probability of seasonal low flow from

July-October based on 12 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 2.1 1.6 1.4 1.3 -- --

3 2.3 1.8 1.6 1.4 -- --

7 2.5 1.9 1.7 1.5 -- --

14 2.6 2.1 1.8 1.6 -- --

30 2.9 2.3 2.0 1.7 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 4.8 1.7 3.2 1.0 13

November 3.9 1.3 2.6 .83 12

December 3.3 1.2 2.0 .59 13

January 2.3 1.3 1.8 .37 13

February 2.3 1.2 1.7 .39 13

March 3.3 1.2 2.0 .65 13

April 28 2.5 10 7.9 13

May 78 14 31 21 13

June 65 13 28 13 13

July 29 4.7 11 6.3 13

August 8.1 1.9 4.5 1.7 13

September 4.8 1.9 3.3 .82 13

Annual 14 4.2 8.6 3.0 12
Statistical Summaries of Streamflow 163

06190500 Gardner River at Mammoth, Yellowstone National Park, Wyo.

Site Number 142

LOCATION.--Lat 44°59'00", long 110°41'00" (NAD 27), 0.25 mi downstream from footbridge on Mount Everts trail, 0.5 mi upstream from Boiling River 

(formerly Hot River), 0.9 mi northeast of Mammoth, and 3.75 mi (revised) upstream from mouth.

DRAINAGE AREA.--200 mi2.

PERIOD OF RECORD.--15 years (1923-38).

GAGE.--Water-stage recorder. Altitude of gage is 5,680 ft (NGVD 29, from topographic map). Prior to June 10, 1927, staff gage at site 0.25 mi upstream at 

different datum. June 10 to July 29, 1927, staff gage at described site and datum.

REMARKS.--No diversion or regulation upstream from station. Records not equivalent to those for station near Mammoth, 1.25 mi downstream.

Magnitude and probability of annual low flow

based on 15 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 57 51 47 45 -- --

3 61 54 50 48 -- --

7 63 55 52 49 -- --

14 63 56 52 49 -- --

30 64 57 53 50 -- --

60 69 61 57 54 -- --

90 71 63 59 56 -- --

120 74 64 61 58 -- --

183 81 70 65 62 -- --

Magnitude and probability of seasonal low flow from

March-June based on 16 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 62 54 51 48 -- --

3 64 57 53 51 -- --

7 65 58 54 52 -- --

14 66 58 55 53 -- --

30 69 60 57 54 -- --

Magnitude and probability of seasonal low flow from

November-February based on 15 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 60 53 50 47 -- --

3 64 56 53 50 -- --

7 66 57 53 50 -- --

14 66 58 53 50 -- --

30 67 58 54 51 -- --

Duration of daily mean flows based on 15 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

47 49 52 59 69 77 84 92

40% 30% 20% 15% 10% 5% 2% 1%

109 128 197 274 375 559 796 1,020

Magnitude and probability of annual high flow

based on 15 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 827 1,200 1,460 1,820 -- --

3 783 1,110 1,350 1,660 -- --

7 713 1,020 1,250 1,550 -- --

15 646 932 1,130 1,410 -- --

30 567 803 968 1,190 -- --

60 459 627 736 872 -- --

90 368 496 579 682 -- --

Magnitude and probability of seasonal low flow from

July-October based on 16 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 79 67 62 59 -- --

3 80 69 64 60 -- --

7 83 71 66 62 -- --

14 85 73 68 64 -- --

30 89 75 70 66 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 132 72 97 21 17

November 153 65 87 23 15

December 104 59 78 14 15

January 98 55 71 11 15

February 90 50 69 13 15

March 90 52 71 12 16

April 180 69 114 40 16

May 977 201 407 189 16

June 1,070 161 518 241 16

July 409 89 217 94 16

August 185 71 116 34 16

September 146 70 101 23 17

Annual 246 106 161 41 15
164 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06191000 Gardner River near Mammoth, Yellowstone National Park, Wyo.

Site Number 143

LOCATION.--Lat 44°59'33", long 110°41'26" (NAD 27), Yellowstone National Park, Hydrologic Unit 10070001, on left bank at Wyoming-Montana State line, 

400 ft upstream from highway bridge, 0.5 mi downstream from Boiling River (formerly Hot River), 1.5 mi north of Mammoth, and at river mile 2.9.

DRAINAGE AREA.--202 mi2.

PERIOD OF RECORD.--October 1938 to September 1972, April l984 to current year (2002). Prior to October 1959, published as "Gardiner River near 

Mammoth."

REVISED RECORDS.--WSP 1729: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 5,623.97 ft (NGVD 29, levels by National Park Service).

REMARKS.--No regulation or diversion upstream from station. U.S. Geological Survey satellite telemeter at station. 

Magnitude and probability of annual low flow

based on 50 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 72 64 60 57 54 52

3 79 70 66 63 59 57

7 83 75 71 68 64 62

14 85 78 75 72 70 68

30 87 81 78 76 74 73

60 92 84 81 79 77 76

90 96 88 84 81 78 76

120 100 91 87 83 80 78

183 111 99 93 89 85 82

Magnitude and probability of seasonal low flow from

March-June based on 52 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 81 73 69 66 63 62

3 85 77 74 71 68 67

7 88 80 77 75 72 71

14 89 82 79 77 74 73

30 92 84 81 79 77 75

Magnitude and probability of seasonal low flow from

November-February based on 51 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 74 65 60 57 54 52

3 81 71 67 64 60 58

7 86 76 72 69 65 63

14 88 80 76 73 70 68

30 91 83 80 77 75 73

Duration of daily mean flows based on 52 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

67 69 74 82 96 106 115 125

40% 30% 20% 15% 10% 5% 2% 1%

145 177 259 359 519 759 1,070 1,310

Magnitude and probability of annual high flow

based on 52 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 1,120 1,440 1,620 1,820 1,940 2,060

3 1,060 1,370 1,550 1,750 1,880 2,000

7 979 1,290 1,460 1,660 1,790 1,910

15 876 1,170 1,340 1,550 1,700 1,840

30 776 1,030 1,190 1,390 1,530 1,660

60 622 818 939 1,080 1,180 1,280

90 502 650 740 845 918 988

Magnitude and probability of seasonal low flow from

July-October based on 51 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 113 99 93 88 82 79

3 116 102 96 91 85 82

7 118 104 98 93 87 84

14 121 106 99 94 88 84

30 125 109 102 96 90 86

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 176 95 127 20 52

November 151 86 113 16 52

December 135 79 103 12 52

January 134 78 97 13 52

February 128 75 93 10 52

March 128 75 94 11 52

April 304 84 141 47 53

May 1,070 283 510 163 53

June 1,350 212 715 285 53

July 662 133 303 125 53

August 236 103 162 36 53

September 190 93 137 23 53

Annual 324 138 217 47 52
Statistical Summaries of Streamflow 165

06191500 Yellowstone River at Corwin Springs, Mont.

Site Number 144

LOCATION.--Lat 45°06'43", long 110°47'37" (NAD 27), in NW1⁄4SE1⁄4NW1⁄4 sec.30, T.8 S., R.8 E., Park County, Hydrologic Unit 10070002, on left bank 20 ft 

downstream from county road bridge at Corwin Springs, 1.3 mi upstream from Mol Heron Creek, 7 mi northwest of Gardiner, and at river mile 549.7.

DRAINAGE AREA.--2,619 mi2.

PERIOD OF RECORD.--August 1889 to November 1893, published as "at Horr," September 1910 to current year (2002). Monthly discharge only for some 

periods, published in WSP 1309.

REVISED RECORDS.--WSP 1309: 1912. WSP 1509: 1889-94, 1911, 1913, 1916-18, 1920-21, 1925, 1927. WSP 1559: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 5,079.09 ft (NGVD 29). Aug. 12, 1889, to Nov. 4, 1893, nonrecording gages at site 2 mi upstream at different 

datums. Sept. 2, 1910, to Apr. 19, 1935, nonrecording gages on bridge at present datum. 

REMARKS.--Natural storage in Yellowstone Lake. Diversions for irrigation of about 960 acres of which 40 acres lie downstream from station. U.S. Geological 

Survey satellite telemeter at station. 

Magnitude and probability of annual low flow

based on 91 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 641 515 458 415 371 344

3 660 532 474 430 386 358

7 686 556 497 452 406 377

14 713 582 521 475 427 398

30 750 609 543 492 439 406

60 808 664 594 540 483 448

90 870 719 647 591 531 494

120 944 783 706 647 585 546

183 1,210 991 888 808 723 671

Magnitude and probability of seasonal low flow from

March-June based on 92 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 799 647 570 510 446 405

3 821 664 586 523 456 414

7 844 687 606 543 474 431

14 866 708 627 563 494 450

30 922 757 671 601 525 477

Magnitude and probability of seasonal low flow from

November-February based on 92 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 685 546 481 431 380 348

3 706 565 499 449 397 364

7 735 592 524 473 419 385

14 764 618 549 496 441 406

30 792 642 570 514 455 419

Duration of daily mean flows based on 92 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

507 552 631 762 897 1,030 1,210 1,440

40% 30% 20% 15% 10% 5% 2% 1%

1,900 2,750 4,670 6,320 8,590 11,800 16,000 19,200

Magnitude and probability of annual high flow

based on 92 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 16,500 21,000 23,600 26,600 28,600 30,500

3 15,600 20,000 22,700 25,900 28,100 30,300

7 14,500 18,900 21,700 25,000 27,300 29,700

15 13,300 17,400 20,000 23,200 25,500 27,800

30 12,000 15,500 17,700 20,200 22,000 23,700

60 9,950 12,500 14,100 15,800 17,000 18,100

90 8,220 10,300 11,400 12,800 13,700 14,500

Magnitude and probability of seasonal low flow from

July-October based on 91 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1,270 1,030 921 836 748 693

3 1,290 1,050 937 850 760 704

7 1,320 1,080 960 871 778 720

14 1,360 1,110 992 902 809 751

30 1,460 1,180 1,040 945 842 779

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 2,430 782 1,500 381 92

November 2,060 702 1,180 272 92

December 1,420 551 961 196 92

January 1,360 448 848 197 92

February 1,340 411 836 191 92

March 1,380 412 920 184 92

April 3,540 576 1,560 555 92

May 13,600 2,580 6,140 2,020 92

June 22,500 4,240 11,600 3,800 92

July 13,300 2,020 6,770 2,690 92

August 5,690 1,320 3,160 990 92

September 3,210 938 1,930 496 93

Annual 5,160 1,900 3,120 683 92
166 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06192500 Yellowstone River near Livingston, Mont.

Site Number 145

LOCATION.--Lat 45°35'50", long 110°33'55" (NAD 27), in NE1⁄4NW1⁄4NW1⁄4 sec.12, T.3 S., R.9 E., Park County, Hydrologic Unit 10070002, on right bank 50 ft 

downstream from bridge on Montana Secondary Highway 540, 2 mi downstream from Suce Creek, 4 mi south of Livingston, and at river mile 501.4.

DRAINAGE AREA.--3,551 mi2.

PERIOD OF RECORD.--May 1897 to December 1905, August 1928 to September 1932, October 1937 to current year (2002). Monthly discharge only for some 

periods, published in WSP 1309.

REVISED RECORDS.--WSP 1309: 1899. WSP 1509: 1902. WSP 1629: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 4,542.49 ft (NGVD 29). May 2, 1897, to Dec. 31, 1905, nonrecording gage on highway bridge at different 

datum. Aug. 23, 1928, to Sept. 30, 1932, and Mar. 14, 1938, to Feb. 3, 1951, nonrecording gage on highway bridge at present datum.

REMARKS.--Diversions for irrigation of about 24,200 acres of which about 2,000 acres lie downstream from station. U.S. Geological Survey satellite telemeter 

at station.

Magnitude and probability of annual low flow

based on 73 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 877 737 672 622 569 536

3 918 776 709 656 601 566

7 977 834 767 714 659 624

14 1,030 892 827 777 724 691

30 1,090 946 878 826 771 736

60 1,160 1,010 943 887 827 789

90 1,260 1,090 1,010 951 885 843

120 1,360 1,180 1,090 1,030 958 913

183 1,650 1,400 1,280 1,180 1,080 1,020

Magnitude and probability of seasonal low flow from

March-June based on 75 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1,110 941 856 789 717 671

3 1,140 974 890 823 751 704

7 1,190 1,030 946 882 813 769

14 1,210 1,070 997 941 881 843

30 1,270 1,120 1,050 998 939 902

Magnitude and probability of seasonal low flow from

November-February based on 74 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 907 757 687 632 575 539

3 953 800 726 668 606 568

7 1,020 860 784 723 659 618

14 1,080 917 840 780 717 676

30 1,140 972 892 829 762 719

Duration of daily mean flows based on 75 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

787 832 965 1,130 1,280 1,440 1,670 1,960

40% 30% 20% 15% 10% 5% 2% 1%

2,340 3,160 5,260 7,200 9,860 14,000 18,500 22,200

Magnitude and probability of annual high flow

based on 75 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 19,200 24,000 26,700 29,600 31,600 33,400

3 18,200 23,000 25,800 29,000 31,200 33,200

7 16,900 21,600 24,400 27,800 30,100 32,300

15 15,400 19,800 22,400 25,500 27,700 29,800

30 13,800 17,600 19,900 22,500 24,400 26,200

60 11,300 14,300 16,000 18,000 19,500 20,800

90 9,340 11,600 13,000 14,500 15,600 16,600

Magnitude and probability of seasonal low flow from

July-October based on 74 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1,770 1,480 1,340 1,230 1,120 1,040

3 1,800 1,500 1,360 1,250 1,140 1,060

7 1,830 1,530 1,380 1,270 1,150 1,080

14 1,870 1,550 1,400 1,290 1,170 1,090

30 1,960 1,620 1,460 1,340 1,210 1,130

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 3,120 1,130 2,020 434 76

November 2,600 1,100 1,680 314 76

December 1,980 930 1,390 226 76

January 1,760 727 1,220 223 75

February 1,730 763 1,210 217 75

March 1,800 899 1,290 189 75

April 3,850 1,170 1,940 587 75

May 13,000 2,750 6,930 2,190 75

June 27,100 5,000 13,300 4,190 75

July 15,000 2,750 7,650 2,960 75

August 5,730 1,710 3,600 1,030 76

September 3,810 1,280 2,390 565 76

Annual 6,120 2,400 3,730 763 75
Statistical Summaries of Streamflow 167

06193000 Shields River near Wilsall, Mont.

Site Number 146

LOCATION.--Lat 46°09'09", long 110°35'13" (NAD 27), in SE1⁄4NW1⁄4 sec.34, T.5 N., R.9 E., Park County, on left bank 11 mi northeast of Wilsall and 12 mi 

upstream from Flathead Creek.

DRAINAGE AREA.--87.8 mi2 (revised). 

PERIOD OF RECORD.--23 years (1935-57).

GAGE.--Wire-weight gage. Altitude of gage is 5,590 ft (NGVD 29, by barometer). May 10, 1935, to Oct. 12, 1942, staff gage at site 800 ft downstream at different 

datum. Oct. 13, 1942, to May 21, 1948, staff gage at present site and datum.

REMARKS.--Diversions for irrigation of 3,100 acres, of which 830 acres lie downstream from station.

Magnitude and probability of annual low flow

based on 21 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 5.5 4.5 4.0 3.7 -- --

3 5.7 4.6 4.1 3.7 -- --

7 6.3 5.0 4.4 3.9 -- --

14 7.5 5.7 4.9 4.3 -- --

30 9.0 6.8 5.7 4.9 -- --

60 10 7.7 6.4 5.4 -- --

90 12 8.5 7.1 6.0 -- --

120 13 9.4 7.7 6.5 -- --

183 14 10 9.0 8.0 -- --

Magnitude and probability of seasonal low flow from

March-June based on 22 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 7.4 5.6 4.7 4.1 -- --

3 7.7 5.7 4.8 4.2 -- --

7 8.4 6.4 5.4 4.7 -- --

14 9.5 7.2 6.1 5.2 -- --

30 11 8.8 7.4 6.4 -- --

Magnitude and probability of seasonal low flow from

November-February based on 22 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 6.4 4.6 4.0 3.7 -- --

3 6.7 4.7 4.1 3.7 -- --

7 7.1 5.0 4.4 4.0 -- --

14 8.1 5.8 5.0 4.3 -- --

30 9.2 6.9 5.8 4.9 -- --

Duration of daily mean flows based on 22 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

4.2 4.8 6.2 7.6 10 13 15 18

40% 30% 20% 15% 10% 5% 2% 1%

22 32 73 121 178 296 447 527

Magnitude and probability of annual high flow

based on 22 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 503 761 965 1,260 -- --

3 464 690 863 1,110 -- --

7 410 597 734 922 -- --

15 354 520 639 798 -- --

30 295 433 530 656 -- --

60 236 325 384 457 -- --

90 182 249 293 348 -- --

Magnitude and probability of seasonal low flow from

July-October based on 22 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 9.8 6.5 5.1 4.1 -- --

3 10 6.8 5.4 4.4 -- --

7 11 7.2 5.7 4.7 -- --

14 11 7.8 6.5 5.5 -- --

30 12 8.7 7.2 6.2 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 63 7.6 19 12 22

November 36 3.8 16 6.6 22

December 26 4.5 13 4.7 22

January 18 5.0 11 3.5 22

February 18 4.4 10 3.8 22

March 17 6.2 12 2.8 22

April 184 14 61 42 22

May 441 65 221 97 23

June 656 80 242 141 23

July 184 19 63 37 23

August 48 7.3 21 9.4 23

September 38 6.7 16 7.7 23

Annual 105 33 60 20 22
168 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06193500 Shields River at Clyde Park, Mont.

Site Number 147

LOCATION.--Lat 45°53'08", long 110°37'05" (NAD 27), in NW1⁄4NW1⁄4 sec.33, T.2 N., R.9 E., Park County, on right bank just downstream from highway bridge, 

0.3 mi west of Clyde Park, 2 mi upstream from Brackett Creek, and at river mile 14.2.

DRAINAGE AREA.--543 mi2.

PERIOD OF RECORD.--38 years. March 1921 to September 1923, April 1929 to December 1932, February 1934 to September 1967 (discontinued). Monthly 

discharge only for some periods, published in WSP 1309.

REVISED RECORDS.--WSP 1309: 1922, 1948(M). WSP 1729: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 4,780 ft (NGVD 29, from topographic map). Mar. 31, 1921, to Sept. 30, 1923, nonrecording gage at present 

site at different datum. Apr. 27, 1929, to Jan. 5, 1951, nonrecording gage at present site and datum.

REMARKS.--Diversions for irrigation of about 19,500 acres, of which 500 acres lie downstream from station.

Magnitude and probability of annual low flow

based on 36 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 18 8.4 5.2 3.3 1.9 --

3 19 8.9 5.4 3.4 1.9 --

7 20 9.6 5.9 3.7 2.1 --

14 22 11 6.7 4.3 2.4 --

30 27 13 7.9 5.0 2.8 --

60 33 17 11 6.9 4.0 --

90 39 21 14 9.9 6.3 --

120 46 27 20 15 10 --

183 51 33 25 20 15 --

Magnitude and probability of seasonal low flow from

March-June based on 39 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 33 22 17 13 10 --

3 35 24 19 15 11 --

7 38 28 24 21 18 --

14 45 33 29 26 23 --

30 79 51 41 35 29 --

Magnitude and probability of seasonal low flow from

November-February based on 38 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 25 18 15 12 10 --

3 27 19 16 13 11 --

7 30 21 18 15 13 --

14 33 24 20 17 14 --

30 38 28 23 20 17 --

Duration of daily mean flows based on 38 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

5.2 9.3 18 26 36 44 54 65

40% 30% 20% 15% 10% 5% 2% 1%

84 120 216 309 448 678 982 1,180

Magnitude and probability of annual high flow

based on 38 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 1,020 1,590 2,010 2,580 3,030 --

3 934 1,420 1,740 2,170 2,480 --

7 837 1,220 1,470 1,770 1,980 --

15 724 1,060 1,270 1,520 1,690 --

30 611 902 1,090 1,310 1,470 --

60 500 736 887 1,070 1,200 --

90 411 603 725 874 981 --

Magnitude and probability of seasonal low flow from

July-October based on 39 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 19 8.5 5.4 3.5 2.0 --

3 20 9.0 5.7 3.5 2.1 --

7 22 9.7 6.1 4.0 2.2 --

14 24 11 6.8 4.5 2.5 --

30 29 13 8.1 5.3 2.9 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 199 16 70 38 39

November 136 22 66 23 39

December 130 17 53 22 39

January 99 16 45 17 38

February 201 19 57 38 39

March 348 33 103 65 39

April 820 62 252 162 40

May 1,260 48 485 252 41

June 1,320 63 507 305 41

July 318 9.6 133 89 41

August 158 3.1 47 37 41

September 187 4.3 54 39 41

Annual 352 46 159 66 38
Statistical Summaries of Streamflow 169

06194000 Brackett Creek near Clyde Park, Mont.

Site Number 148

LOCATION.--Lat 45°52'00", long 110°40'10" (NAD 27), in SE1⁄4NE1⁄4 sec.1, T.1 N., R.8 E., Park County, near right bank on upstream side of private bridge, 

3.5 mi southwest of Clyde Park and 4 mi upstream from mouth.

DRAINAGE AREA.--57.9 mi2 (revised). 

PERIOD OF RECORD.--25 years (1921-23, 1934-57).

GAGE.--Wire-weight gage. Altitude of gage is 4,930 ft (NGVD 29, from topographic map). Mar. 30, 1921, to Sept. 30, 1923, staff gage at site 0.75 mi upstream 

at different datum. Apr. 5, 1934, to May 24, 1949, staff gage and May 25, 1949, to Dec. 14, 1953, wire-weight gage at site 25 ft upstream at present datum.

Magnitude and probability of annual low flow

based on 23 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 2.5 1.3 0.90 0.63 -- --

3 2.9 1.8 1.3 1.0 -- --

7 3.4 2.4 1.9 1.6 -- --

14 4.0 2.8 2.3 1.9 -- --

30 4.8 3.3 2.7 2.2 -- --

60 5.8 3.9 3.2 2.7 -- --

90 6.2 4.4 3.8 3.3 -- --

120 6.9 5.0 4.3 3.8 -- --

183 7.9 5.7 4.9 4.3 -- --

Magnitude and probability of seasonal low flow from

March-June based on 25 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 4.3 2.8 2.0 1.5 1.1 --

3 4.6 3.2 2.6 2.1 1.7 --

7 5.3 3.9 3.3 2.8 2.3 --

14 6.2 4.6 3.8 3.2 2.5 --

30 9.3 6.0 4.7 3.8 2.9 --

Magnitude and probability of seasonal low flow from

November-February based on 25 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 3.3 1.8 1.2 0.77 0.46 --

3 3.6 2.1 1.6 1.2 .80 --

7 4.0 2.6 2.1 1.7 1.4 --

14 4.4 3.0 2.5 2.1 1.7 --

30 5.0 3.4 2.8 2.3 1.9 --

Duration of daily mean flows based on 25 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

2.0 2.3 3.1 4.4 5.8 7.2 8.8 11

40% 30% 20% 15% 10% 5% 2% 1%

14 21 40 57 82 118 171 211

Magnitude and probability of annual high flow

based on 25 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 187 303 395 529 643 --

3 169 269 348 463 559 --

7 152 234 294 378 446 --

15 132 197 242 302 348 --

30 114 167 202 246 279 --

60 95 133 157 185 204 --

90 77 108 127 150 166 --

Magnitude and probability of seasonal low flow from

July-October based on 25 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 6.2 3.4 2.3 1.5 0.94 --

3 6.5 3.7 2.5 1.7 1.1 --

7 6.8 3.9 2.7 1.9 1.2 --

14 7.3 4.2 2.9 2.0 1.3 --

30 8.1 4.8 3.3 2.3 1.5 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 24 4.2 10 4.5 25

November 20 2.1 9.5 4.4 25

December 18 2.4 7.8 4.1 25

January 16 2.5 6.6 3.2 25

February 17 2.6 6.7 3.3 25

March 22 2.6 10 4.9 25

April 105 14 46 26 27

May 230 15 102 51 27

June 214 12 77 42 27

July 64 5.6 28 15 27

August 31 1.7 11 6.6 27

September 16 2.1 9.8 3.8 27

Annual 55 9.3 28 10 25
170 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06195600 Shields River near Livingston, Mont.

Site Number 149

LOCATION.--Lat 45°44'18", long 110°28'45" (NAD 27), in NE1⁄4SE1⁄4NW1⁄4 sec.22, T.1 S., R.10 E., Park County, Hydrologic Unit 10070003, on right bank 0.2 mi 

downstream from private road bridge, 6.5 mi northeast of Livingston, and at river mile 2.0.

DRAINAGE AREA.--852 mi2.

PERIOD OF RECORD.--October 1978 to current year (2002).

GAGE.--Water-stage recorder. Altitude of gage is 4,420 ft (NGVD 29). Oct. 1, 1978, to Aug. 12, 1980, water-stage recorder at site 0.2 mi upstream at datum 

7.89 ft higher.

REMARKS.--Diversions for irrigation of about 32,000 acres upstream from station. National Weather Service satellite telemeter at station. 

Magnitude and probability of annual low flow

based on 23 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 50 37 30 25 -- --

3 53 39 32 26 -- --

7 60 43 35 29 -- --

14 68 48 39 31 -- --

30 75 53 42 34 -- --

60 84 58 46 37 -- --

90 93 66 53 43 -- --

120 104 76 62 51 -- --

183 114 85 71 61 -- --

Magnitude and probability of seasonal low flow from

March-June based on 24 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 85 63 54 47 -- --

3 91 67 56 49 -- --

7 99 72 61 53 -- --

14 120 86 72 62 -- --

30 149 103 87 76 -- --

Magnitude and probability of seasonal low flow from

November-February based on 23 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 56 46 42 39 -- --

3 61 50 45 42 -- --

7 67 57 52 48 -- --

14 76 64 58 54 -- --

30 85 71 64 59 -- --

Duration of daily mean flows based on 24 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

35 43 56 70 87 104 121 143

40% 30% 20% 15% 10% 5% 2% 1%

172 222 353 488 705 1,080 1,610 2,050

Magnitude and probability of annual high flow

based on 24 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 1,640 2,610 3,340 4,360 -- --

3 1,520 2,400 3,020 3,820 -- --

7 1,350 2,090 2,570 3,160 -- --

15 1,140 1,740 2,130 2,600 -- --

30 950 1,480 1,830 2,240 -- --

60 735 1,170 1,460 1,850 -- --

90 619 987 1,240 1,570 -- --

Magnitude and probability of seasonal low flow from

July-October based on 23 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 74 44 33 25 -- --

3 77 46 34 27 -- --

7 80 49 37 29 -- --

14 85 52 39 32 -- --

30 94 57 43 34 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 275 52 150 59 24

November 195 74 134 33 24

December 145 74 109 23 24

January 224 56 103 38 24

February 363 60 125 75 24

March 461 77 177 95 24

April 627 145 370 154 24

May 1,960 198 815 457 24

June 2,260 152 772 514 24

July 1,140 54 323 270 24

August 677 26 134 129 24

September 388 31 134 76 24

Annual 610 114 279 128 24
Statistical Summaries of Streamflow 171

06197000 Big Timber Creek near Big Timber, Mont.

Site Number 150

LOCATION.--Lat 45°57'15", long 110°01'45"' (NAD 27), in SW1⁄4 NE1⁄4 sec.6, T.2 N., R.14 E., Sweet Grass County, 3 mi downstream from confluence of North 

and South Forks and 9 mi northeast of Big Timber.

DRAINAGE AREA.--74.9 mi2.

PERIOD OF RECORD.--11 years (1912-16, 1917-24).

GAGE.--Staff gage Altitude of gage is 4,680 ft (NGVD 29, from topographic map). Prior to Apr. 5, 1918, wire-weight gages at sites 1.5 mi downstream at different 

datum. Apr. 5, 1918, to Apr. 15, 1921, wire-weight gages at sites within 500 ft downstream at different datum.

REMARKS.--Diversions for irrigation of about 5,000 acres upstream from station.

Magnitude and probability of annual low flow

based on 9 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 -- -- -- -- -- --

3 -- -- -- -- -- --

7 -- -- -- -- -- --

14 -- -- -- -- -- --

30 -- -- -- -- -- --

60 -- -- -- -- -- --

90 -- -- -- -- -- --

120 -- -- -- -- -- --

183 -- -- -- -- -- --

Magnitude and probability of seasonal low flow from

March-June based on 11 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 14 7.5 5.2 3.7 -- --

3 15 9.4 7.4 6.0 -- --

7 17 12 9.6 8.4 -- --

14 18 13 11 9.2 -- --

30 20 14 11 9.8 -- --

Magnitude and probability of seasonal low flow from

November-February based on 11 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 13 9.9 8.8 7.9 -- --

3 13 11 9.3 8.1 -- --

7 14 11 9.3 8.2 -- --

14 15 11 9.4 8.3 -- --

30 15 11 9.5 8.4 -- --

Duration of daily mean flows based on 11 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

8.4 8.8 9.8 12 17 21 26 32

40% 30% 20% 15% 10% 5% 2% 1%

43 60 103 151 223 323 443 530

Magnitude and probability of annual high flow

based on 11 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 612 885 1,060 -- -- --

3 529 752 900 -- -- --

7 456 637 763 -- -- --

15 398 544 638 -- -- --

30 356 461 507 -- -- --

60 287 357 380 -- -- --

90 230 288 308 -- -- --

Magnitude and probability of seasonal low flow from

July-October based on 11 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 15 8.8 4.6 0.00 -- --

3 16 9.4 5.3 .00 -- --

7 17 10 7.8 6.0 -- --

14 19 12 10 8.4 -- --

30 23 16 13 12 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 59 12 31 14 12

November 32 10 24 7.2 12

December 43 10 20 9.3 11

January 34 10 17 7.4 11

February 25 9.0 17 5.8 11

March 48 10 23 11 11

April 69 19 48 15 12

May 226 88 145 46 12

June 529 56 310 119 12

July 329 37 176 87 12

August 97 25 56 23 13

September 83 16 35 18 13

Annual 108 40 77 22 11
172 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06197500 Boulder River near Contact, Mont.

Site Number 151

LOCATION.--Lat 45°33'17", long 110°12'00" (NAD 27), in NW1⁄4SE1⁄4SE1⁄4 sec.23, T.3 S., R.12 E., Sweet Grass County, Hydrologic Unit 10070002, on left bank 

0.5 mi downstream from Natural Bridge and Falls, 3.4 mi north of Contact, 9.5 mi southeast of McLeod, 9.7 mi upstream from East Boulder River, and at river 

mile 32.4. 

DRAINAGE AREA.--226 mi2. 

PERIOD OF RECORD.--May 1910 to October 1912, April 1913 to September 1916 (no winter records), April to August 1929, October 1950 to September 1969, 

September 1970 to September 1974, August 1981 to September 1983 (discontinued). Monthly discharge only January to March 1912, published in WSP 1309, 

and February, March 1955, published in WSP 1729. 

REVISED RECORDS.--WSP 1509: 1910-11, 1915 (M). WSP 1916: 1955. 

GAGE.--Water-stage recorder. Altitude of gage is 4,930 ft (NGVD 29, from topographic map). Prior to July 15, 1951, non-recording gages at site 2.7 mi 

downstream at different datum. 

REMARKS.--Diversions for irrigation of about 10 acres. 

Magnitude and probability of annual low flow

based on 24 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 42 34 30 26 -- --

3 44 39 36 34 -- --

7 48 43 40 38 -- --

14 50 45 42 40 -- --

30 52 48 45 44 -- --

60 57 52 49 48 -- --

90 64 57 54 52 -- --

120 70 62 58 56 -- --

183 91 78 72 68 -- --

Magnitude and probability of seasonal low flow from

March-June based on 27 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 47 38 32 28 23 --

3 49 42 39 36 33 --

7 51 45 42 40 37 --

14 53 47 44 42 39 --

30 55 50 47 45 42 --

Magnitude and probability of seasonal low flow from

November-February based on 27 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 43 37 34 32 30 --

3 48 41 38 35 31 --

7 53 46 41 38 32 --

14 56 49 44 41 33 --

30 58 51 46 44 34 --

Duration of daily mean flows based on 27 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

36 44 48 53 62 75 90 121

40% 30% 20% 15% 10% 5% 2% 1%

168 257 590 892 1,340 2,040 2,810 3,170

Magnitude and probability of annual high flow

based on 27 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 3,220 3,850 4,260 4,790 5,180 --

3 3,010 3,630 4,050 4,580 4,990 --

7 2,780 3,380 3,760 4,240 4,590 --

15 2,460 3,000 3,340 3,750 4,060 --

30 2,080 2,490 2,750 3,060 3,280 --

60 1,580 1,850 2,010 2,200 2,320 --

90 1,220 1,430 1,540 1,660 1,740 --

Magnitude and probability of seasonal low flow from

July-October based on 29 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 96 72 61 54 46 --

3 99 76 66 58 51 --

7 102 80 71 64 57 --

14 106 85 76 70 64 --

30 115 92 84 78 72 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 222 83 133 43 31

November 137 67 94 21 29

December 94 42 73 13 27

January 80 30 61 9.8 27

February 73 35 57 7.5 27

March 70 42 56 7.2 27

April 248 53 101 50 29

May 1,240 288 679 256 32

June 3,120 1,250 1,930 463 33

July 2,000 282 994 397 33

August 542 131 277 104 33

September 301 103 158 43 31

Annual 484 258 383 64 27
Statistical Summaries of Streamflow 173

06200000 Boulder River at Big Timber, Mont.

Site Number 152

LOCATION.--Lat 45°50'03", long 109°56'17" (NAD 27), in SE1⁄4NE1⁄4SE1⁄4 sec.14, T.1 N., R.14 E., Sweet Grass County, Hydrologic Unit 10070002, on left bank 

150 ft upstream from Old Boulder Bridge, 1 mi east of Big Timber, and at river mile 1.6.

DRAINAGE AREA.--523 mi2.

PERIOD OF RECORD.--April 1947 to December 1953, March 1955 to current year (2002). Monthly discharge only for April 1947, published in WSP 1309.

GAGE.--Water-stage recorder. Altitude of gage is 4,056.39 ft (NGVD 29, levels by U.S. Army Corps of Engineers).

REMARKS.--Diversions for irrigation of about 13,300 acres, of which about 250 acres lie downstream from station. U.S. Geological Survey satellite telemeter at 

station.

Magnitude and probability of annual low flow

based on 51 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 63 40 30 22 16 12

3 70 46 34 25 17 13

7 81 52 38 28 19 14

14 92 59 43 32 21 15

30 107 71 52 38 25 19

60 126 89 68 51 35 27

90 144 110 87 68 48 37

120 155 121 101 85 67 57

183 167 129 111 98 83 75

Magnitude and probability of seasonal low flow from

March-June based on 53 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 96 76 66 58 49 44

3 104 84 72 63 54 48

7 114 93 81 71 60 53

14 122 102 90 81 70 63

30 129 109 99 90 80 73

Magnitude and probability of seasonal low flow from

November-February based on 53 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 70 50 41 34 28 24

3 79 58 48 40 32 28

7 93 71 59 49 39 34

14 109 85 71 59 47 40

30 124 100 84 70 56 47

Duration of daily mean flows based on 53 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

38 54 78 98 121 143 164 186

40% 30% 20% 15% 10% 5% 2% 1%

232 315 644 1,130 1,820 2,850 4,010 4,860

Magnitude and probability of annual high flow

based on 53 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 4,890 6,060 6,730 7,470 7,970 8,420

3 4,510 5,690 6,370 7,120 7,630 8,100

7 4,060 5,240 5,920 6,700 7,230 7,730

15 3,530 4,560 5,160 5,840 6,300 6,720

30 2,990 3,800 4,280 4,840 5,230 5,590

60 2,250 2,840 3,190 3,600 3,890 4,160

90 1,710 2,150 2,410 2,730 2,940 3,150

Magnitude and probability of seasonal low flow from

July-October based on 54 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 102 56 38 27 18 13

3 104 57 39 28 19 14

7 109 60 41 30 20 15

14 115 63 44 32 22 17

30 131 73 53 39 26 20

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 417 75 220 84 54

November 282 108 191 45 54

December 214 72 154 29 54

January 214 55 136 28 53

February 197 55 128 25 53

March 179 93 128 19 53

April 390 67 212 73 55

May 2,240 429 1,150 419 55

June 4,640 894 2,770 845 55

July 4,310 193 1,270 764 55

August 709 22 244 155 55

September 534 28 193 104 55

Annual 906 310 566 140 53
174 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06200500 Sweet Grass Creek above Melville, Mont.

Site Number 153

LOCATION.--Lat 46°90'15", long 110°05'15" (NAD 27), in NW1⁄4 sec.27, T.5 N., R.13 E., Sweet Grass County, on right bank 7.5 mi northwest of Melville.

DRAINAGE AREA.--63.8 mi2.

PERIOD OF RECORD.--43 years. August 1913 to December 1924, April 1937 to September 1969 (discontinued). May 1907 to September 1911, April to 

September 1912 at site 5 mi upstream published as "Sweetgrass Creek above Melville," records not equivalent owing to diversion and tributary flow. Monthly 

discharge only for some periods, published in WSP 1309.

REVISED RECORDS.--WSP 1509: 1914-15, 1918, 1937. WSP 1729: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 5,490 ft (NGVD 29, by barometer). Aug. 21, 1913, to Dec. 31, 1924, nonrecording gage at site 1,500 ft 

downstream at different datum. Apr. 17, 1937, to Sept. 25, 1951, water-stage recorder at site 1,000 ft downstream at different datum. 

REMARKS.--Diversions for irrigation of 200 acres upstream from station. Diversions in T.5 N., R.12 E. from headwaters of American Fork in Musselshell River 

basin to irrigate an additional 300 acres upstream from station.

Magnitude and probability of annual low flow

based on 41 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 6.8 4.3 3.2 2.4 1.7 --

3 7.2 4.9 3.8 3.0 2.2 --

7 7.5 5.4 4.5 3.8 3.1 --

14 8.0 6.3 5.5 4.9 4.3 --

30 9.2 7.5 6.7 6.0 5.4 --

60 11 8.7 7.8 7.1 6.3 --

90 14 11 9.6 8.5 7.5 --

120 18 14 12 11 9.2 --

183 25 20 17 16 14 --

Magnitude and probability of seasonal low flow from

March-June based on 43 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 7.8 5.4 4.3 3.5 2.8 --

3 8.2 5.7 4.6 3.8 3.0 --

7 8.6 6.3 5.3 4.5 3.7 --

14 9.1 7.0 6.1 5.4 4.8 --

30 11 8.3 7.3 6.6 5.8 --

Magnitude and probability of seasonal low flow from

November-February based on 43 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 8.4 5.1 3.7 2.7 1.8 --

3 8.8 5.7 4.3 3.3 2.4 --

7 9.1 6.2 5.0 4.1 3.2 --

14 9.6 7.2 6.1 5.4 4.7 --

30 11 8.4 7.4 6.7 5.9 --

Duration of daily mean flows based on 43 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

5.8 6.3 7.7 9.7 13 16 21 29

40% 30% 20% 15% 10% 5% 2% 1%

41 63 125 181 261 401 549 691

Magnitude and probability of annual high flow

based on 43 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 782 1,020 1,180 1,360 1,500 --

3 678 863 976 1,110 1,200 --

7 584 731 817 915 983 --

15 498 615 680 751 798 --

30 426 524 577 634 670 --

60 338 406 441 477 499 --

90 269 318 341 364 378 --

Magnitude and probability of seasonal low flow from

July-October based on 43 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 26 19 17 15 14 --

3 26 20 18 16 15 --

7 27 21 18 17 15 --

14 28 22 19 17 16 --

30 31 23 20 18 17 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 97 16 41 22 44

November 51 14 29 10 44

December 33 7.2 19 6.4 44

January 26 5.2 14 4.6 43

February 22 6.0 12 3.8 43

March 20 5.7 11 3.2 43

April 71 6.5 16 10 44

May 318 78 178 66 44

June 585 131 385 106 44

July 360 64 204 75 44

August 147 31 74 26 45

September 110 20 46 20 45

Annual 118 51 86 17 43
Statistical Summaries of Streamflow 175

06201000 Sweet Grass Creek below Melville, Mont.

Site Number 154

LOCATION.--Lat 46°03'41", long 109°50'43" (NAD 27), near middle of south line of sec.27, T.4 N., R.15 E., Sweet Grass County, on left bank 6 mi southeast of 

Melville and 19 mi upstream from East Fork

DRAINAGE AREA.--143 mi2 (revised). 

PERIOD OF RECORD.--11 years (1910-11, 1937-40, 1941-42, 1946-52).

GAGE.--Water-stage recorder. Altitude of gage is 4,740 ft (NGVD 29, by barometer). May 1907 to November 1908, staff gage at site 2.5 mi downstream at 

different datum. Apr. 1, 1909, to Sept. 30, 1924, and Apr. 11, 1937, to Apr. 14, 1941, staff or wire-weight gages at various sites within 150 ft of present site 

at present datum.

REMARKS.--Diversions upstream from station for irrigation of 12,800 acres, of which 100 acres lie downstream from station. 

Magnitude and probability of annual low flow

based on 7 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 -- -- -- -- -- --

3 -- -- -- -- -- --

7 -- -- -- -- -- --

14 -- -- -- -- -- --

30 -- -- -- -- -- --

60 -- -- -- -- -- --

90 -- -- -- -- -- --

120 -- -- -- -- -- --

183 -- -- -- -- -- --

Magnitude and probability of seasonal low flow from

March-June based on 12 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 16 12 10 8.9 -- --

3 17 13 11 9.6 -- --

7 18 13 12 10 -- --

14 19 15 14 13 -- --

30 24 18 16 14 -- --

Magnitude and probability of seasonal low flow from

November-February based on 11 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 15 11 9.5 8.2 -- --

3 16 12 10 8.8 -- --

7 17 14 12 11 -- --

14 19 16 14 13 -- --

30 22 18 16 14 -- --

Duration of daily mean flows based on 11 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

12 14 17 20 27 34 43 54

40% 30% 20% 15% 10% 5% 2% 1%

66 88 153 213 296 434 615 743

Magnitude and probability of annual high flow

based on 11 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 780 1,220 1,550 -- -- --

3 668 1,010 1,260 -- -- --

7 520 795 989 -- -- --

15 426 646 794 -- -- --

30 359 527 638 -- -- --

60 289 405 478 -- -- --

90 233 315 363 -- -- --

Magnitude and probability of seasonal low flow from

July-October based on 24 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 20 10 6.8 4.8 -- --

3 21 11 7.7 5.7 -- --

7 24 13 9.9 7.6 -- --

14 27 16 12 9.3 -- --

30 31 20 16 14 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 136 22 63 30 25

November 87 21 52 19 20

December 67 19 42 14 11

January 44 19 28 8.1 11

February 38 15 24 7.4 11

March 66 16 30 14 12

April 100 16 42 24 24

May 336 73 172 63 28

June 681 50 361 155 30

July 434 35 170 99 30

August 164 16 56 36 30

September 107 18 47 25 30

Annual 128 47 90 27 11
176 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06202510 Stillwater River above Nye Creek, near Nye, Mont.

Site Number 155

LOCATION.--Lat 45°23'46", long 109°52'14" (NAD 27), in SW1⁄4NE1⁄4SW1⁄4 sec.15, T.5 S., R.15 E., Stillwater County, Hydrologic Unit 10007005, at private 

bridge 200 ft above Nye Creek, 1.0 mi below Mountain View Creek, 4.3 mi southwest of Nye, and at river mile 41.3. 

DRAINAGE AREA.--193 mi2. 

PERIOD OF RECORD.--November 1979 to September 1991 (discontinued). 

GAGE.--Nonrecording gage and crest-stage gage. Altitude of gage is 4,880 ft (NGVD 29, from topographic map). 

REMARKS.--Diversions or regulation upstream from gage have not been identified. 

Magnitude and probability of annual low flow

based on 11 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 27 23 22 21 -- --

3 32 27 25 23 -- --

7 37 33 31 29 -- --

14 42 38 36 34 -- --

30 46 41 39 37 -- --

60 53 46 42 39 -- --

90 58 49 45 42 -- --

120 65 54 49 46 -- --

183 92 75 67 61 -- --

Magnitude and probability of seasonal low flow from

March-June based on 12 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 36 29 27 24 -- --

3 38 32 29 26 -- --

7 41 36 34 32 -- --

14 46 40 38 36 -- --

30 49 44 41 39 -- --

Magnitude and probability of seasonal low flow from

November-February based on 11 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 29 24 22 21 -- --

3 34 28 26 24 -- --

7 39 33 31 30 -- --

14 44 38 36 35 -- --

30 49 42 40 37 -- --

Duration of daily mean flows based on 11 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

33 34 39 46 55 65 82 110

40% 30% 20% 15% 10% 5% 2% 1%

162 263 482 743 1,210 1,940 2,740 3,060

Magnitude and probability of annual high flow

based on 11 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 3,740 4,230 4,370 -- -- --

3 3,350 3,630 3,670 -- -- --

7 2,900 3,280 3,380 -- -- --

15 2,540 2,940 3,070 -- -- --

30 2,140 2,460 2,570 -- -- --

60 1,550 1,830 1,950 -- -- --

90 1,200 1,420 1,520 -- -- --

Magnitude and probability of seasonal low flow from

July-October based on 11 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 83 65 57 50 -- --

3 92 75 66 60 -- --

7 98 78 68 60 -- --

14 103 81 71 63 -- --

30 115 90 79 71 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 243 82 127 44 11

November 156 58 88 27 12

December 77 46 63 12 12

January 73 42 56 10 12

February 67 39 52 8.6 12

March 70 41 51 8.4 12

April 238 67 138 61 12

May 1,080 440 781 228 12

June 2,380 896 1,810 433 12

July 1,620 303 912 466 12

August 471 113 294 93 12

September 326 76 169 62 12

Annual 437 270 373 66 11
Statistical Summaries of Streamflow 177

06204050 West Rosebud Creek near Roscoe, Mont.

Site Number 156

LOCATION.--Lat 45°14'35", long 109°43'50" (NAD 27), in NE1⁄4 sec.10, T.7 S., R.16 E., Stillwater County, Hydrologic Unit 10070005, on left bank at Mystic 

Lake powerplant, 2.0 mi downstream from Mystic Lake, 13.5 mi southwest of Roscoe, and at river mile 26.8.

DRAINAGE AREA.--52.1 mi2.

PERIOD OF RECORD.--September 1965 to current year (2002).

GAGE.--Water-stage recorder and rectangular weir. Altitude of gage is 6,535.60 ft (NGVD 29).

REMARKS.--Flow regulated by Mystic Lake (station number 06204000). U.S. Geological Survey satellite telemeter at station.

Magnitude and probability of annual low flow

based on 36 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 17 9.2 6.2 4.3 2.7 --

3 22 12 8.2 5.7 3.5 --

7 26 16 11 7.3 4.4 --

14 30 19 13 9.0 5.5 --

30 35 23 17 11 7.0 --

60 40 29 23 19 14 --

90 50 40 35 31 27 --

120 68 54 47 41 34 --

183 84 77 73 69 66 --

Magnitude and probability of seasonal low flow from

March-June based on 37 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 23 12 7.8 5.2 3.1 --

3 25 14 9.0 6.1 3.7 --

7 28 16 11 7.4 4.5 --

14 32 19 13 9.1 5.6 --

30 36 24 17 12 7.1 --

Magnitude and probability of seasonal low flow from

November-February based on 37 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 34 20 14 9.6 6.1 --

3 37 24 18 14 9.9 --

7 40 31 26 23 20 --

14 44 34 29 25 22 --

30 50 39 34 30 25 --

Duration of daily mean flows based on 37 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

16 20 27 34 44 58 72 83

40% 30% 20% 15% 10% 5% 2% 1%

98 134 172 195 247 366 541 682

Magnitude and probability of annual high flow

based on 37 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 632 929 1,110 1,310 1,440 --

3 589 856 1,020 1,200 1,320 --

7 530 751 882 1,030 1,130 --

15 468 650 759 885 971 --

30 398 541 630 737 812 --

60 308 398 457 528 581 --

90 261 325 364 412 446 --

Magnitude and probability of seasonal low flow from

July-October based on 36 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 40 21 14 9.9 6.5 --

3 49 31 25 20 16 --

7 61 40 31 26 20 --

14 70 45 35 28 21 --

30 84 58 47 38 30 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 167 33 94 34 37

November 178 31 82 37 37

December 118 28 74 21 37

January 148 26 67 21 37

February 92 29 60 15 37

March 124 22 55 24 37

April 108 3.6 43 19 37

May 134 16 74 29 37

June 558 76 221 97 37

July 712 158 367 129 37

August 277 103 197 38 37

September 183 38 122 37 38

Annual 164 82 122 19 37
178 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06204500 Rosebud Creek near Absarokee, Mont.

Site Number 157

LOCATION.--Lat 45°29'12", long 109°27'19" (NAD 27), in SW1⁄4NW1⁄4 sec.13, T.4 S., R.8 E., Stillwater County, on right bank 80 ft downstream from Smith 

Bridge, 0.2 mi downstream from confluence of East and West Rosebud Creeks, and 2.5 mi south of Absarokee.

DRAINAGE AREA.--394 mi2 .

PERIOD OF RECORD.--34 years. April 1935 to September 1969 (discontinued).

REVISED RECORDS.--WSP 1036: 1944. WSP 1309: 1935-36(M). WSP 1729: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 4,160 ft (NGVD 29, by barometer). Prior to July 14, 1942, nonrecording gage at present site and datum.

REMARKS.--Flow partly regulated by Mystic Lake (station number 06204000). Diversions for irrigation of about 16,000 acres upstream from station.

Magnitude and probability of annual low flow

based on 33 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 86 66 56 47 38 --

3 94 74 63 54 44 --

7 105 83 71 60 49 --

14 116 91 77 65 53 --

30 129 101 84 70 56 --

60 143 115 97 83 67 --

90 156 132 117 105 91 --

120 166 144 133 123 113 --

183 202 173 160 150 140 --

Magnitude and probability of seasonal low flow from

March-June based on 34 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 107 78 63 52 40 --

3 116 86 70 58 45 --

7 124 94 78 66 53 --

14 134 104 88 75 62 --

30 154 116 98 84 70 --

Magnitude and probability of seasonal low flow from

November-February based on 34 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 91 70 59 51 42 --

3 101 78 65 55 45 --

7 114 86 71 61 51 --

14 125 94 78 66 53 --

30 139 106 86 71 58 --

Duration of daily mean flows based on 34 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

66 81 103 125 151 174 202 239

40% 30% 20% 15% 10% 5% 2% 1%

283 373 590 759 1,010 1,390 1,940 2,180

Magnitude and probability of annual high flow

based on 34 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 2,110 2,880 3,410 4,090 4,610 --

3 1,950 2,590 3,010 3,510 3,890 --

7 1,760 2,320 2,650 3,040 3,310 --

15 1,530 2,010 2,310 2,660 2,910 --

30 1,360 1,790 2,050 2,370 2,590 --

60 1,140 1,480 1,690 1,940 2,110 --

90 958 1,230 1,390 1,580 1,710 --

Magnitude and probability of seasonal low flow from

July-October based on 34 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 175 136 118 105 91 --

3 187 145 126 111 95 --

7 199 156 136 120 103 --

14 214 171 149 133 115 --

30 232 186 165 149 133 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 449 149 246 61 34

November 274 130 200 33 34

December 214 113 166 26 34

January 201 47 148 34 34

February 226 51 144 37 34

March 278 91 165 43 34

April 544 66 212 86 35

May 892 223 526 194 35

June 2,250 598 1,200 407 35

July 1,910 383 1,060 404 35

August 741 226 464 147 35

September 605 125 310 96 35

Annual 634 241 407 97 34
Statistical Summaries of Streamflow 179

06205000 Stillwater River near Absarokee, Mont.

Site Number 158

LOCATION.--Lat 45°33'04", long 109°23'12" (NAD 27), in NE1⁄4NE1⁄4NW1⁄4 sec.28, T.3 S., R.19 E., Stillwater County, Hydrologic Unit 10070005, on right bank 

3 mi downstream from Rosebud Creek, 3.5 mi northeast of Absarokee, 9 mi southwest of Columbus, and at river mile 9.4.

DRAINAGE AREA.--975 mi2.

PERIOD OF RECORD.--July 1910 to September 1914 (no winter records), March 1935 to September 1995, October 1995 to current year (2002; seasonal records 

only).

REVISED RECORDS.--WSP 1309: 1911(M). WSP 1729: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 3,873.8 ft (NGVD 29, levels by U.S. Army Corps of Engineers). Prior to Oct. 1, 1914, nonrecording gage, 

and Mar. 26, 1935, to Sept. 30, 1942, nonrecording gage, at bridge 2 mi upstream at different datums.

REMARKS.--Flow partly regulated by Mystic Lake (station number 06204000). Diversions for irrigation of about 24,300 acres, of which 400 acres lie downstream 

from station. U.S. Geological Survey satellite telemeter at station.

Magnitude and probability of annual low flow

based on 60 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 154 115 95 80 65 56

3 170 130 109 92 74 63

7 192 152 130 112 93 81

14 210 172 151 134 115 103

30 231 193 172 154 135 123

60 262 221 199 181 162 149

90 291 249 227 209 189 176

120 321 278 255 236 215 201

183 399 333 301 275 248 231

Magnitude and probability of seasonal low flow from

March-June based on 63 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 205 152 122 98 67 58

3 218 164 132 106 77 67

7 226 175 148 126 95 85

14 241 192 167 145 116 106

30 262 209 185 165 136 126

Magnitude and probability of seasonal low flow from

November-February based on 63 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 160 116 96 83 67 59

3 176 131 111 93 76 67

7 198 154 132 115 94 84

14 218 174 153 136 117 106

30 245 194 175 156 138 126

Duration of daily mean flows based on 63 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

121 149 197 226 284 336 394 481

40% 30% 20% 15% 10% 5% 2% 1%

609 836 1,410 1,960 2,700 3,820 5,240 5,970

Magnitude and probability of annual high flow

based on 63 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 5,910 7,520 8,480 9,620 10,400 11,200

3 5,390 6,880 7,800 8,900 9,690 10,400

7 4,840 6,280 7,180 8,270 9,060 9,820

15 4,230 5,500 6,290 7,240 7,920 8,580

30 3,730 4,790 5,430 6,180 6,690 7,180

60 3,040 3,860 4,330 4,870 5,220 5,550

90 2,470 3,110 3,470 3,870 4,140 4,380

Magnitude and probability of seasonal low flow from

July-October based on 69 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 389 287 237 199 161 138

3 402 299 249 211 172 149

7 417 317 269 233 196 173

14 438 336 288 252 214 191

30 477 369 319 281 243 219

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 852 0.00 509 147 71

November 574 227 403 73 65

December 430 184 317 54 63

January 413 .00 273 66 63

February 449 .00 260 69 63

March 565 .00 280 85 63

April 1,180 144 410 146 70

May 2,880 660 1,510 480 71

June 5,780 1,560 3,510 1,020 72

July 6,370 626 2,360 1,010 72

August 1,960 280 903 330 73

September 1,100 275 618 202 73

Annual 1,470 507 940 214 63
180 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06207500 Clarks Fork Yellowstone River near Belfry, Mont.

Site Number 159

LOCATION.--Lat 45°00'37", long 109°03'53" (NAD 27), in NW1⁄4SW1⁄4NW1⁄4 sec.32, T.9 S., R.22 E., Carbon County, Hydrologic Unit 10070006, on left bank 

0.2 mi upstream from county road bridge and Big Sand Coulee, 0.8 mi north of Wyoming-Montana State line, 9.5 mi southwest of Belfry, and at river mile 71.2.

DRAINAGE AREA.--1,154 mi2.

PERIOD OF RECORD.--July 1921 to current year (2002). Monthly discharge only for some periods, published in WSP 1309. Published as "Clarks Fork at 

Chance" prior to October 1956 and as "Clarks Fork Yellowstone River at Chance" October 1956 to September 1968.

REVISED RECORDS.--WSP 1309: 1922 (M). WSP 1729: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 3,986.24 ft (NGVD 29, levels by U.S. Army Corps of Engineers). Prior to Nov. 15, 1934, nonrecording gage, 

and Nov. 15, 1934, to July 26, 1951, water-stage recorder at bridge 0.4 mi downstream from different datum. July 27, 1951, to Sept. 30, 1953, water-stage 

recorder at present site at datum 0.98 ft higher.

REMARKS.--Diversions for irrigation of about 11,100 acres upstream from station. U.S. Geological Survey satellite telemeter at station. 

Magnitude and probability of annual low flow

based on 80 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 121 85 67 54 41 34

3 130 91 71 57 42 34

7 143 99 77 60 44 35

14 155 107 83 65 48 38

30 171 119 94 75 56 45

60 202 146 116 92 69 55

90 232 174 140 114 86 70

120 249 192 159 133 106 89

183 263 207 181 161 141 128

Magnitude and probability of seasonal low flow from

March-June based on 81 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 171 128 104 84 64 52

3 181 139 113 92 69 56

7 195 153 125 101 76 61

14 209 166 138 114 89 73

30 223 178 153 131 108 94

Magnitude and probability of seasonal low flow from

November-February based on 81 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 145 107 88 74 60 51

3 157 117 96 80 64 54

7 173 134 114 97 80 69

14 190 151 130 113 94 82

30 209 174 155 139 122 111

Duration of daily mean flows based on 81 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

74 102 137 164 205 234 263 315

40% 30% 20% 15% 10% 5% 2% 1%

375 575 1,300 2,010 2,900 4,250 5,900 7,290

Magnitude and probability of annual high flow

based on 81 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 7,030 8,640 9,620 10,800 11,600 12,400

3 6,590 8,110 9,040 10,100 10,900 11,600

7 5,940 7,450 8,380 9,510 10,300 11,100

15 5,170 6,560 7,430 8,480 9,250 9,990

30 4,460 5,550 6,210 6,980 7,530 8,050

60 3,530 4,340 4,810 5,360 5,750 6,110

90 2,780 3,420 3,800 4,240 4,550 4,840

Magnitude and probability of seasonal low flow from

July-October based on 80 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 170 104 78 61 45 36

3 175 108 81 63 47 38

7 182 112 84 65 48 38

14 193 118 88 68 50 41

30 217 132 99 77 57 46

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 725 46 280 145 81

November 648 115 295 88 81

December 379 110 263 54 81

January 359 110 231 47 81

February 328 100 222 43 81

March 364 96 222 42 81

April 1,170 110 425 204 81

May 5,700 839 2,040 801 81

June 7,220 1,610 4,110 1,200 81

July 5,740 349 2,190 1,090 81

August 1,450 66 616 313 82

September 834 50 314 164 82

Annual 1,480 547 936 214 81
Statistical Summaries of Streamflow 181

06208500 Clarks Fork Yellowstone River at Edgar, Mont.

Site Number 160

LOCATION.--Lat 45°27'58", long 108°50'35" (NAD 27), in SE1⁄4SE1⁄4SE1⁄4 sec.23, T.4 S., R.23 E., Carbon County, Hydrologic Unit 10070006, on right bank 

400 ft downstream from county bridge, 0.5 mi east of Edgar, 6 mi upstream from Rock Creek, and at river mile 22.1.

DRAINAGE AREA.--2,022 mi2.

PERIOD OF RECORD.--July 1921 to September 1969, October 1986 to current year (2002).

REVISED RECORDS.--WSP 1509: 1924, 1932(M). WSP 1729: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 3,460 ft (NGVD 29). Prior to Aug. 31, 1953, nonrecording gage at same site and datum.

REMARKS.--Diversions for irrigation of about 41,500 acres, of which about 840 acres lie downstream from the station. In addition, about 6,300 acres of land 

upstream from the station are irrigated by diversions from the adjoining Rock Creek basin. U.S. Geological Survey satellite telemeter at station. Flows of 

White Horse Canal subtracted from discharge values at station. 

Magnitude and probability of annual low flow

based on 63 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 195 130 96 71 47 35

3 211 143 106 78 52 39

7 234 157 116 85 56 41

14 256 173 128 95 64 47

30 288 197 146 109 73 54

60 337 252 200 157 113 89

90 370 297 252 215 175 150

120 402 332 293 260 224 200

183 428 356 322 296 269 252

Magnitude and probability of seasonal low flow from

March-June based on 64 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 270 198 152 115 79 59

3 290 224 174 133 90 67

7 375 297 238 186 132 101

14 375 297 238 186 132 101

30 375 297 238 186 132 101

Magnitude and probability of seasonal low flow from

November-February based on 64 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 221 177 155 138 120 109

3 239 194 171 153 133 121

7 262 216 194 177 159 147

14 287 242 220 202 184 172

30 315 263 237 216 193 178

Duration of daily mean flows based on 64 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

135 175 219 272 322 373 429 486

40% 30% 20% 15% 10% 5% 2% 1%

566 730 1,310 2,020 2,880 4,150 5,820 7,160

Magnitude and probability of annual high flow

based on 64 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 6,890 8,400 9,270 10,300 11,000 11,600

3 6,380 7,880 8,750 9,760 10,500 11,100

7 5,740 7,260 8,180 9,280 10,100 10,800

15 5,000 6,390 7,280 8,370 9,170 9,950

30 4,330 5,450 6,180 7,080 7,750 8,410

60 3,420 4,220 4,730 5,350 5,810 6,260

90 2,710 3,350 3,760 4,240 4,600 4,940

Magnitude and probability of seasonal low flow from

July-October based on 63 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 272 159 113 82 55 41

3 282 167 119 88 59 45

7 300 180 129 95 64 49

14 323 195 140 103 70 53

30 371 228 165 122 84 63

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 1,010 298 534 167 64

November 777 310 501 98 64

December 592 217 409 76 64

January 512 200 351 69 64

February 584 180 349 76 64

March 554 220 364 75 64

April 1,400 123 558 213 64

May 5,580 757 2,110 803 64

June 7,260 1,770 4,070 1,220 64

July 4,770 290 2,030 1,030 64

August 1,540 50 616 343 65

September 1,400 156 477 208 65

Annual 1,620 644 1,030 224 64
182 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06208800 Clarks Fork Yellowstone River near Silesia, Mont.

Site Number 161

LOCATION.--Lat 45°30'48", long 108°49'42" (NAD 27), in NW1⁄4SE1⁄4 sec.l, T.4 S., R.23 E., Carbon County, Hydrologic Unit 10070006 on left bank 0.5 mi 

downstream from Whitehorse Canal intake, 1 mi upstream from Rock Creek, 3 mi south of Silesia, and at river mile 16.3. 

DRAINAGE AREA.--2,093 mi2. 

PERIOD OF RECORD.--October 1969 to November 1986 (discontinued). Records for July 1921 to September 1969 published as "Clarks Fork Yellowstone River 

at Edgar" at site 5.8 mi upstream not equivalent because of diversion into Whitehorse Canal during irrigation season. 

GAGE.--Water-stage recorder. Altitude of gage is 3,405.79 ft (NGVD 29, levels by U.S. Corps of Army Engineers). 

REMARKS.--Diversion for irrigation of about 45,900 acres of which about 2,180 acres lie downstream from station. In addition, about 56,200 acres of land 

upstream from station are irrigated by diversions from the adjoining Rock Creek basin. 

Magnitude and probability of annual low flow

based on 16 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 192 134 106 85 -- --

3 207 158 135 116 -- --

7 252 195 166 144 -- --

14 281 227 202 183 -- --

30 350 299 272 251 -- --

60 398 345 314 287 -- --

90 431 389 368 352 -- --

120 466 425 405 390 -- --

183 533 465 431 404 -- --

Magnitude and probability of seasonal low flow from

March-June based on 17 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 302 202 148 109 -- --

3 312 234 191 158 -- --

7 338 295 273 255 -- --

14 375 335 312 293 -- --

30 398 358 337 321 -- --

Magnitude and probability of seasonal low flow from

November-February based on 16 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 207 168 150 136 -- --

3 223 189 175 164 -- --

7 269 227 208 193 -- --

14 310 261 236 217 -- --

30 367 325 304 288 -- --

Duration of daily mean flows based on 17 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

200 224 280 328 403 453 503 579

40% 30% 20% 15% 10% 5% 2% 1%

682 843 1,300 1,980 3,030 4,630 6,070 7,740

Magnitude and probability of annual high flow

based on 17 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 7,720 9,460 10,500 11,700 -- --

3 7,280 9,040 10,100 11,200 -- --

7 6,450 8,260 9,350 10,600 -- --

15 5,630 7,300 8,270 9,350 -- --

30 4,830 6,050 6,660 7,260 -- --

60 3,910 4,800 5,170 5,490 -- --

90 3,060 3,780 4,090 4,350 -- --

Magnitude and probability of seasonal low flow from

July-October based on 17 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 336 218 166 129 -- --

3 346 226 173 136 -- --

7 368 244 190 152 -- --

14 399 278 226 190 -- --

30 475 347 293 254 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 950 484 657 141 18

November 669 416 567 71 18

December 680 397 478 75 17

January 514 292 423 62 17

February 499 350 424 44 17

March 596 334 428 77 17

April 761 337 521 131 17

May 3,230 1,020 1,890 607 17

June 6,660 2,220 4,450 1,290 17

July 5,600 422 2,430 1,300 17

August 1,250 333 766 301 17

September 1,020 263 671 226 17

Annual 1,510 661 1,140 235 17
Statistical Summaries of Streamflow 183

06209500 Rock Creek near Red Lodge, Mont.

Site Number 162

LOCATION (REVISED).--Lat 45°05'11", long 109°19'46" (NAD 27), in NW1⁄4NE1⁄4SW1⁄4 sec.36, T.8 S., R.19 E., Carbon County, Hydrologic Unit 10070006, on 

left bank 40 ft downstream from county bridge, 6.7 mi south of Red Lodge, and at river mile 49.1.

DRAINAGE AREA.--105 mi2 .

PERIOD OF RECORD.--April to December 1932, May 1934 to September 1982, May 1985 to September 1986, January 2000 to current year (2002). Monthly 

discharge only for May 1934, published in WSP 1309.

REVISED RECORDS.--WSP 1729: Drainage area. WDR MT-00-1: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 6,400 ft (NGVD 29). Prior to October 1986, water-stage recorder at datum 6,099.42 ft, levels by U.S. Army 

Corps of Engineers, at previous site 3.1 mi downstream. Streamflows are equivalent.

REMARKS.--Flow partly regulated by Glacier Lake. No diversions upstream from station. U.S. Geological Survey satellite telemeter at station. 

Magnitude and probability of annual low flow

based on 49 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 23 19 17 16 14 --

3 24 20 19 17 16 --

7 25 22 21 20 18 --

14 26 24 22 21 20 --

30 28 26 24 23 21 --

60 31 28 26 24 22 --

90 36 32 29 27 25 --

120 41 36 33 31 29 --

183 66 57 53 49 46 --

Magnitude and probability of seasonal low flow from

March-June based on 52 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 25 21 20 18 16 15

3 26 22 20 19 17 16

7 27 23 22 20 19 18

14 28 24 23 22 20 19

30 29 26 24 23 22 20

Magnitude and probability of seasonal low flow from

November-February based on 51 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 25 20 18 16 14 12

3 26 22 20 18 16 15

7 27 24 22 20 18 17

14 29 26 24 22 21 19

30 31 27 25 24 22 20

Duration of daily mean flows based on 51 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

20 23 25 28 34 40 48 67

40% 30% 20% 15% 10% 5% 2% 1%

105 176 286 368 490 685 934 1,060

Magnitude and probability of annual high flow

based on 51 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 1,070 1,430 1,650 1,910 2,090 2,260

3 986 1,300 1,480 1,690 1,840 1,980

7 887 1,170 1,340 1,530 1,670 1,790

15 773 1,000 1,130 1,280 1,380 1,470

30 683 872 975 1,090 1,160 1,220

60 576 724 806 895 953 1,010

90 483 597 658 724 766 804

Magnitude and probability of seasonal low flow from

July-October based on 52 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 63 54 50 48 45 43

3 64 56 52 49 46 44

7 67 58 53 50 47 45

14 70 60 55 52 48 46

30 80 67 61 57 52 49

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 124 50 83 18 52

November 78 40 55 10 52

December 56 27 42 6.4 52

January 45 21 34 5.5 52

February 42 20 31 4.6 52

March 40 20 30 3.8 52

April 99 24 40 12 52

May 460 88 220 87 54

June 1,130 273 596 187 55

July 1,090 220 494 182 55

August 427 153 258 64 55

September 219 89 141 31 55

Annual 252 97 172 35 51
184 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06212500 Red Lodge Creek below Cooney Reservoir, near Boyd, Mont.

Site Number 163

LOCATION.--Lat 45°26'59", long 109°11'06" (NAD 27), in NE1⁄4NW1⁄4NW1⁄4 sec.31, T.4 S., R.21 E., Carbon County, Hydrologic Unit 10070006, on right bank 

250 ft upstream from Cottonwood Creek, 1.5 mi downstream from Cooney Dam, 6 mi west of Boyd, and at river mile 10.5.

DRAINAGE AREA.--210 mi2.

PERIOD OF RECORD.--September 1937 to current year (2002); seasonal records water years 1997-99.

REVISED RECORDS.--WSP 1309: 1942(M), 1944(M). WSP 2116: 1957(M).

GAGE.--Water-stage recorder. Altitude of gage is 4,139.12 ft (NGVD 29).

REMARKS.--Some return flow from lands irrigated by water diverted from Rock Creek and East Rosebud Creek basins. Flow completely regulated by Cooney 

Reservoir (station number 06212000). Diversions for irrigation of about 6,900 acres upstream from station. 

Magnitude and probability of annual low flow

based on 60 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 5.6 2.0 0.89 0.39 0.05 0.00

3 5.9 2.5 1.6 1.0 .61 .42

7 7.5 3.5 2.3 1.6 .98 .71

14 9.4 4.5 2.9 2.0 1.2 .86

30 12 5.9 4.0 2.9 2.0 1.6

60 17 8.4 5.6 3.9 2.6 1.9

90 24 12 7.9 5.4 3.5 2.5

120 33 17 11 8.0 5.3 3.9

183 57 36 27 21 16 12

Magnitude and probability of seasonal low flow from

March-June based on 62 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 11 4.7 2.4 1.2 0.54 0.29

3 11 5.5 3.8 2.7 1.9 1.5

7 12 6.2 4.2 3.0 2.1 1.6

14 15 7.1 4.8 3.4 2.3 1.8

30 19 8.5 5.6 3.9 2.6 2.0

Magnitude and probability of seasonal low flow from

November-February based on 61 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 9.8 4.2 2.6 1.8 1.1 0.79

3 10 4.6 2.9 2.0 1.3 .95

7 11 5.4 3.6 2.6 1.7 1.3

14 14 7.0 4.8 3.5 2.4 1.9

30 16 8.1 5.5 3.9 2.6 2.0

Duration of daily mean flows based on 62 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

2.8 4.1 5.9 9.9 19 31 47 67

40% 30% 20% 15% 10% 5% 2% 1%

94 125 165 186 231 308 455 567

Magnitude and probability of annual high flow

based on 62 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 389 691 985 1,500 2,020 2,680

3 380 639 864 1,220 1,540 1,930

7 360 574 739 972 1,160 1,370

15 320 498 630 810 954 1,110

30 267 409 515 664 785 915

60 218 323 401 508 594 686

90 194 281 341 421 483 546

Magnitude and probability of seasonal low flow from

July-October based on 64 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 29 7.7 2.9 1.0 0.09 0.04

3 31 9.0 3.9 1.7 .62 .47

7 41 15 7.3 3.6 1.5 .76

14 48 19 9.6 4.9 2.1 1.1

30 64 32 19 12 6.4 4.0

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 234 2.4 79 49 65

November 212 3.5 65 51 63

December 120 3.5 37 28 62

January 95 2.0 28 20 62

February 139 2.2 29 25 62

March 232 2.4 43 46 62

April 253 3.2 81 65 65

May 801 5.1 177 148 65

June 685 49 225 144 65

July 383 57 172 70 65

August 220 60 141 39 65

September 197 20 112 42 65

Annual 226 24 100 37 62
Statistical Summaries of Streamflow 185

06214500 Yellowstone River at Billings, Mont.

Site Number 164

LOCATION.--Lat 45°48'00", long 108°28'00" (NAD 27), in SE1⁄4SE1⁄4SE1⁄4 sec.27, T.1 N., R.26 E., Yellowstone County, Hydrologic Unit 10070007, on right 

bank 0.3 mi downstream from bridge on U.S. Highway 87, 1 mi northeast of Billings, 10 mi upstream from Pryor Creek, and at river mile 360.3.

DRAINAGE AREA.--11,805 mi2.

PERIOD OF RECORD.--May 1904 to December 1905 (gage heights only January to March, December 1905), August 1928 to current year (2002). Monthly 

discharge only for some periods, published in WSP 1309. Published as "near Billings" 1904-05.

REVISED RECORDS.--WDR MT-68: 1967 (M). WSP 1729: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 3,080 ft (NGVD 29). May 1904 to December 1905, nonrecording gage at bridge 0.3 ft upstream at different 

datum. Aug. 24, 1928, to June 30, 1932, nonrecording gage at bridge 0.3 mi upstream at datum 2.0 ft higher. July 1, 1932, to Oct. 12, 1937, water-stage recorder 

at old diversion dam 3.3 mi upstream at different datum. Oct. 13, 1937, to Jan. 9, 1963, and Dec. 2, 1967, to Sept. 12, 1990, water-stage recorder 0.3 mi upstream 

at datum 3,081.36 ft. Jan. 10, 1963, to Dec. 2, 1967, water-stage recorder 2.1 mi upstream at datum 3,069.9 ft.

REMARKS.--Diversions for irrigation of about 350,000 acres upstream from station. U.S. Army Corps of Engineers satellite telemeter at station. 

Magnitude and probability of annual low flow

based on 73 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1,270 949 794 676 555 483

3 1,370 1,050 897 778 656 581

7 1,570 1,260 1,110 998 879 805

14 1,870 1,530 1,360 1,230 1,090 997

30 2,170 1,780 1,590 1,430 1,270 1,160

60 2,390 1,990 1,790 1,640 1,470 1,360

90 2,590 2,190 1,990 1,840 1,670 1,570

120 2,830 2,400 2,200 2,030 1,860 1,750

183 3,210 2,640 2,380 2,170 1,960 1,820

Magnitude and probability of seasonal low flow from

March-June based on 74 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 2,200 1,690 1,430 1,230 1,020 885

3 2,270 1,770 1,510 1,300 1,090 952

7 2,410 1,930 1,690 1,500 1,290 1,160

14 2,590 2,120 1,900 1,720 1,530 1,410

30 2,820 2,310 2,080 1,900 1,720 1,610

Magnitude and probability of seasonal low flow from

November-February based on 74 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1,290 958 799 680 558 485

3 1,400 1,060 906 785 660 585

7 1,600 1,280 1,130 1,010 894 820

14 1,890 1,550 1,390 1,260 1,120 1,040

30 2,220 1,840 1,650 1,490 1,330 1,220

Duration of daily mean flows based on 74 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

1,280 1,510 1,760 2,160 2,560 2,930 3,370 3,850

40% 30% 20% 15% 10% 5% 2% 1%

4,400 5,740 8,860 12,700 18,100 25,900 34,500 43,100

Magnitude and probability of annual high flow

based on 74 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 38,700 49,400 55,600 62,500 67,000 71,300

3 36,500 47,200 53,400 60,500 65,400 69,900

7 33,400 43,900 50,300 57,800 63,000 68,000

15 29,900 39,300 45,000 51,900 56,700 61,300

30 26,300 34,300 39,100 44,800 48,700 52,400

60 21,100 27,300 31,000 35,300 38,300 41,200

90 17,000 21,900 24,800 28,100 30,400 32,500

Magnitude and probability of seasonal low flow from

July-October based on 75 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 2,980 2,200 1,840 1,580 1,310 1,150

3 3,010 2,230 1,880 1,610 1,350 1,190

7 3,080 2,290 1,930 1,660 1,390 1,230

14 3,210 2,380 2,000 1,720 1,440 1,270

30 3,430 2,540 2,140 1,840 1,540 1,360

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 6,800 2,130 4,020 1,050 76

November 5,160 2,280 3,560 683 76

December 4,450 1,580 2,800 534 75

January 3,830 1,360 2,480 511 74

February 4,380 1,560 2,650 654 74

March 5,480 1,770 3,020 726 74

April 8,800 1,440 4,110 1,290 75

May 24,100 5,640 12,600 4,030 75

June 53,900 9,850 25,300 8,350 76

July 37,200 3,410 13,700 6,570 76

August 9,780 1,460 5,230 2,120 76

September 7,300 1,530 4,090 1,360 77

Annual 12,100 3,760 6,970 1,720 74
186 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06216000 Pryor Creek at Pryor, Mont.

Site Number 165

LOCATION.--Lat 45°26'06", long 108°32'01" (NAD 27), in NE1⁄4NW1⁄4NE1⁄4 sec.5, T.5 S., R.26 E., Big Horn County, Hydrologic Unit 10070008, on left bank 

60 ft upstream from county bridge, 0.5 mi north of Pryor, 1.4 mi downstream from Lost Creek, and at river mile 82.7.

DRAINAGE AREA.--117 mi2.

PERIOD OF RECORD.--June 1921 to September 1924 (no winter records), November 1966 to current year (2002). Monthly discharge only for some periods, 

published in WSP 1309.

REVISED RECORDS.--WSP 1729: Drainage area. WDR MT-87-1: 1982-83 (M), 1986 (M).

GAGE.--Water-stage recorder. Altitude of gage is 4,007.35 ft (NGVD 29, levels by U.S. Army Corps of Engineers). Prior to Oct. 14, 1966, nonrecording gage at 

approximately same site at different datum.

REMARKS.--Diversions for irrigation of about 1,100 acres upstream from station. 

Magnitude and probability of annual low flow

based on 35 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 12 7.5 5.9 4.9 3.9 --

3 12 8.3 6.8 5.9 5.0 --

7 13 9.0 7.6 6.6 5.7 --

14 14 9.8 8.2 7.1 6.2 --

30 16 11 9.3 8.1 7.0 --

60 19 13 11 10 8.7 --

90 21 15 13 12 10 --

120 23 17 15 13 12 --

183 25 19 17 16 15 --

Magnitude and probability of seasonal low flow from

March-June based on 36 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 16 11 9.7 8.6 7.5 --

3 17 12 10 8.9 7.8 --

7 18 13 11 9.8 8.6 --

14 20 15 13 11 9.7 --

30 23 18 16 14 13 --

Magnitude and probability of seasonal low flow from

November-February based on 35 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 23 18 17 16 15 --

3 24 19 17 16 15 --

7 24 20 18 17 16 --

14 25 21 19 18 17 --

30 26 22 20 19 18 --

Duration of daily mean flows based on 35 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

7.9 9.4 12 16 20 24 26 28

40% 30% 20% 15% 10% 5% 2% 1%

31 34 41 44 52 64 93 135

Magnitude and probability of annual high flow

based on 35 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 91 214 360 667 1,030 --

3 77 171 278 494 738 --

7 65 134 207 345 493 --

15 57 110 162 256 350 --

30 50 89 126 188 248 --

60 43 71 96 136 174 --

90 39 61 79 108 134 --

Magnitude and probability of seasonal low flow from

July-October based on 37 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 12 7.6 6.0 4.9 4.0 --

3 12 8.3 6.9 5.9 5.0 --

7 13 9.1 7.6 6.6 5.7 --

14 14 9.8 8.2 7.2 6.2 --

30 16 11 9.3 8.2 7.1 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 63 18 32 10 37

November 62 19 32 9.8 37

December 70 19 31 10 37

January 54 19 29 8.3 36

February 56 19 30 9.1 36

March 71 18 32 11 36

April 59 18 33 11 39

May 251 18 55 47 39

June 158 14 41 30 39

July 69 6.8 23 13 40

August 50 7.7 21 9.4 40

September 61 12 26 10 40

Annual 66 16 32 12 35
Statistical Summaries of Streamflow 187

06216500 Pryor Creek near Billings, Mont.

Site Number 166

LOCATION.--Lat 45°42'54", long 108°18'51" (NAD 27), in sec.30, T.1 S., R.28 E., Yellowstone County, on bridge on U.S. Highway 87, 11 mi southeast of 

Billings and 14 mi upstream from mouth.

DRAINAGE AREA.--440 mi2 (revised). At site used 1911-24, 430 mi2 (revised).

PERIOD OF RECORD.--15 years (1938-53).

GAGE.--Crest-stage gage after May 26, 1955. Altitude of gage is 3,310 ft (NGVD 29, by barometer). Prior to Sept. 30, 1924, wire-weight gage at site 2 mi 

upstream at different datum. Mar. 30, 1938, to Dec. 31, 1953, wire-weight gage at same site and datum.

REMARKS.--Diversions for irrigation of 1,500 acres upstream from station. 

Magnitude and probability of annual low flow

based on 14 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1.9 0.07 0.00 0.00 -- --

3 2.2 .09 .00 .00 -- --

7 2.5 .28 .04 .00 -- --

14 3.6 .58 .18 .02 -- --

30 6.3 1.6 .74 .38 -- --

60 9.5 3.0 1.5 .84 -- --

90 14 6.0 3.7 2.5 -- --

120 19 9.5 6.4 4.5 -- --

183 26 16 12 8.9 -- --

Magnitude and probability of seasonal low flow from

March-June based on 17 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 14 3.3 1.0 0.00 -- --

3 15 3.7 1.2 .00 -- --

7 18 4.7 1.6 .00 -- --

14 26 11 6.0 .02 -- --

30 39 20 12 .39 -- --

Magnitude and probability of seasonal low flow from

November-February based on 16 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 17 9.3 6.0 0.00 -- --

3 17 9.5 6.2 .00 -- --

7 19 10 6.7 .00 -- --

14 21 12 8.0 .02 -- --

30 24 14 9.2 .39 -- --

Duration of daily mean flows based on 16 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

0.29 0.58 3.1 9.4 17 25 32 39

40% 30% 20% 15% 10% 5% 2% 1%

45 57 74 88 119 188 294 418

Magnitude and probability of annual high flow

based on 16 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 486 837 1,080 1,400 -- --

3 380 673 891 1,190 -- --

7 267 469 626 848 -- --

15 192 322 421 558 -- --

30 144 239 309 404 -- --

60 108 176 226 295 -- --

90 91 146 184 235 -- --

Magnitude and probability of seasonal low flow from

July-October based on 28 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 5.5 0.24 0.00 0.00 0.00 --

3 6.5 .30 .00 .00 .00 --

7 6.8 .53 .04 .00 .00 --

14 7.9 .95 .19 .02 .00 --

30 11 2.4 .94 .39 .13 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 207 9.3 46 36 29

November 80 15 43 18 27

December 66 18 36 15 19

January 77 .00 32 18 16

February 145 .00 51 40 16

March 233 .00 98 61 17

April 290 25 95 73 28

May 324 16 100 73 29

June 297 9.7 91 68 29

July 152 .28 38 36 29

August 59 .76 22 16 29

September 119 1.7 35 28 30

Annual 92 22 52 24 16
188 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06216900 Pryor Creek near Huntley, Mont.

Site Number 167

LOCATION.--Lat 45°49'19", long 108°17'23" (NAD 27), in NE1⁄4SE1⁄4NW1⁄4 sec.19, T.1 N., R.28 E., Yellowstone County, Hydrologic Unit 10070008, on left 

bank 250 ft upstream from county bridge on Indian Creek road, 1.9 mi downstream from Indian Creek, 4.9 mi south of Huntley, and at river mile 11.2. 

DRAINAGE AREA.--582 mi2. 

PERIOD OF RECORD.--October 1978 to September 2001. 

GAGE.--Water-stage recorder. Altitude of gage is 3,140 ft (NGVD 29, from topographic map.) Prior to Nov. 12, 1996, water-stage recorder at site 450 ft 

downstream at different datum. 

REMARKS.--Diversions for irrigation of about 3,200 acres upstream from station. 

Magnitude and probability of annual low flow

based on 21 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 4.7 1.1 0.40 0.04 -- --

3 5.6 1.3 .54 .24 -- --

7 6.5 1.8 .86 .44 -- --

14 8.4 2.8 1.6 .92 -- --

30 11 4.4 2.6 1.7 -- --

60 16 7.4 4.8 3.3 -- --

90 22 13 10 7.9 -- --

120 28 19 15 13 -- --

183 34 26 22 19 -- --

Magnitude and probability of seasonal low flow from

March-June based on 21 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 21 9.2 5.6 3.6 -- --

3 22 11 6.7 4.4 -- --

7 25 16 13 11 -- --

14 34 22 18 15 -- --

30 44 33 29 26 -- --

Magnitude and probability of seasonal low flow from

November-February based on 21 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 20 13 11 9.2 -- --

3 23 15 13 11 -- --

7 26 19 17 15 -- --

14 30 23 20 18 -- --

30 36 27 24 21 -- --

Duration of daily mean flows based on 21 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

1.5 3.1 8.0 16 27 34 40 46

40% 30% 20% 15% 10% 5% 2% 1%

54 62 78 89 112 166 260 366

Magnitude and probability of annual high flow

based on 21 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 580 1,010 1,340 1,800 -- --

3 459 792 1,040 1,390 -- --

7 317 547 726 979 -- --

15 213 365 494 691 -- --

30 160 262 347 478 -- --

60 121 188 243 327 -- --

90 104 154 194 253 -- --

Magnitude and probability of seasonal low flow from

July-October based on 21 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 4.7 1.2 0.56 0.19 -- --

3 5.7 1.4 .77 .38 -- --

7 6.7 2.0 .98 .58 -- --

14 8.5 3.0 1.8 .97 -- --

30 11 4.6 2.8 1.7 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 117 25 50 19 22

November 112 24 50 18 22

December 95 26 49 17 22

January 126 27 51 23 22

February 116 22 66 28 22

March 453 43 103 92 21

April 218 30 86 46 22

May 403 33 126 108 22

June 184 29 74 45 22

July 107 3.0 31 29 22

August 61 2.5 22 17 22

September 51 11 32 11 22

Annual 136 39 63 24 21
Statistical Summaries of Streamflow 189

06217750 Fly Creek at Pompeys Pillar, Mont.

Site Number 168

LOCATION.--Lat 45°59'33", long 107°57'07" (NAD 27), in SW1⁄4NW1⁄4SE1⁄4 sec.23, T.3 N., R.30 E., Yellowstone County, Hydrologic Unit 10070007, on 

downstream side of county bridge near right bank at Pompeys Pillar, 300 ft downstream from Lost Boy Creek, and 0.5 mi upstream from mouth. 

DRAINAGE AREA.--285 mi2. 

PERIOD OF RECORD.--October 1968 to September 1981 (discontinued). 

GAGE.--Nonrecording gage and crest-stage gage. Altitude of gage is 2,852.84 ft (NGVD 29, Montana State Highway Commission bridge reference mark). Oct. 1, 

1968, to May 1974, nonrecording gage at present site but different datum. May 1974 to July 16, 1978, nonrecording gage at bridge 3 mi upstream at different 

datum. 

REMARKS.--Flow affected by waste water from irrigation ditches and by return flow from irrigated areas upstream. 

Magnitude and probability of annual low flow

based on 12 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 3.2 2.3 1.9 1.7 -- --

3 3.8 3.1 2.7 2.4 -- --

7 4.2 3.4 3.1 2.8 -- --

14 4.7 3.8 3.4 3.1 -- --

30 5.2 4.2 3.8 3.5 -- --

60 5.8 4.9 4.5 4.2 -- --

90 6.6 5.5 5.0 4.7 -- --

120 7.9 6.4 5.7 5.2 -- --

183 20 16 14 13 -- --

Magnitude and probability of seasonal low flow from

March-June based on 13 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 4.9 3.5 3.0 2.6 -- --

3 5.7 4.3 3.8 3.5 -- --

7 5.9 4.5 4.1 3.9 -- --

14 6.3 4.9 4.5 4.3 -- --

30 8.2 5.7 5.0 4.5 -- --

Magnitude and probability of seasonal low flow from

November-February based on 12 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 3.2 2.3 2.0 1.7 -- --

3 3.9 3.1 2.8 2.5 -- --

7 4.2 3.5 3.1 2.8 -- --

14 4.7 3.9 3.4 3.1 -- --

30 5.3 4.3 3.8 3.5 -- --

Duration of daily mean flows based on 13 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

3.0 3.6 4.4 5.2 6.7 8.1 11 15

40% 30% 20% 15% 10% 5% 2% 1%

26 39 53 61 72 89 132 282

Magnitude and probability of annual high flow

based on 13 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 368 1,420 3,120 7,660 -- --

3 316 1,080 2,180 4,850 -- --

7 233 669 1,230 2,450 -- --

15 165 396 661 1,190 -- --

30 118 244 373 609 -- --

60 80 141 200 302 -- --

90 65 108 147 213 -- --

Magnitude and probability of seasonal low flow from

July-October based on 12 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 8.4 6.1 4.9 3.9 -- --

3 9.1 7.4 6.6 5.9 -- --

7 10 8.1 7.2 6.4 -- --

14 11 8.6 7.6 6.8 -- --

30 13 9.8 8.8 8.2 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 54 7.9 19 12 13

November 10 5.9 8.8 1.5 13

December 9.8 3.7 6.6 1.6 13

January 32 3.6 9.3 8.0 13

February 238 4.8 39 69 13

March 437 4.3 75 122 13

April 53 6.9 18 14 13

May 514 23 76 132 13

June 115 35 60 21 13

July 74 18 39 14 13

August 77 25 44 15 13

September 97 45 61 14 13

Annual 69 21 38 16 13
190 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06287000 Bighorn River near St. Xavier, Mont.

Site Number 169

LOCATION.--Lat 45°19'00", long 107°55'05" (NAD 27), in NW1⁄4NW1⁄4NE1⁄4 sec.16, T.6 S., R.31 E., Big Horn County, Hydrologic Unit 10080015, on right bank 

800 ft downstream from Yellowtail Dam, 1,500 ft downstream from Lime Kiln Creek, 14 mi southwest of St. Xavier, and at river mile 83.9.

DRAINAGE AREA.--19,667 mi2. Area at site used prior to Apr. 16, 1963, 19,626 mi2.

PERIOD OF RECORD.--October 1934 to current year (2002).

GAGE.--Water-stage recorder. Altitude of gage is 3,158.38 ft (NGVD 29, levels by U.S. Army Corps of Engineers). Prior to Apr. 16, 1963, and June 13, 1964, 

to Mar. 31, 1965, water-stage recorder at site 1.2 mi upstream at different datum. Apr. 1, 1965, to July 31, 1966, water-stage recorder at site 1,300 ft downstream 

at present datum.

REMARKS.--Recorded discharge values. Some regulation by 14 reservoirs in Wyoming with combined capacity of 1,400,000 acre-ft and complete regulation by 

Bighorn Lake since Nov. 3, 1965. Diversions for irrigation of about 375,000 acres upstream from station. Bureau of Reclamation satellite telemeter at station.

Unregulated streamflow period

Magnitude and probability of annual low flow

based on 29 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 882 604 483 396 311 --

3 981 741 638 563 488 --

7 1,150 929 836 768 701 --

14 1,340 1,090 977 891 802 --

30 1,540 1,260 1,130 1,030 914 --

60 1,730 1,390 1,230 1,100 971 --

90 1,920 1,540 1,370 1,230 1,090 --

120 2,110 1,710 1,520 1,370 1,210 --

183 2,250 1,830 1,640 1,490 1,330 --

Magnitude and probability of seasonal low flow from

March-June based on 30 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1,390 1,090 945 838 729 --

3 1,520 1,180 1,020 897 767 --

7 1,670 1,320 1,150 1,020 879 --

14 1,920 1,490 1,290 1,130 972 --

30 2,170 1,680 1,470 1,310 1,140 --

Magnitude and probability of seasonal low flow from

November-February based on 29 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 889 613 489 401 316 --

3 991 747 647 573 496 --

7 1,170 936 843 780 709 --

14 1,400 1,100 983 896 811 --

30 1,630 1,290 1,140 1,040 923 --

Duration of daily mean flows based on 30 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

850 998 1,190 1,390 1,710 1,990 2,280 2,580

40% 30% 20% 15% 10% 5% 2% 1%

2,880 3,300 4,120 5,030 6,690 10,500 15,400 18,800

Magnitude and probability of annual high flow

based on 30 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 14,500 21,100 25,600 31,600 36,100 --

3 13,300 20,000 24,600 30,600 35,300 --

7 12,200 18,600 23,100 29,000 33,500 --

15 10,900 16,700 20,600 25,500 29,200 --

30 9,630 14,700 17,900 21,700 24,500 --

60 7,730 11,500 13,900 16,600 18,600 --

90 6,420 9,260 11,000 13,000 14,300 --

Magnitude and probability of seasonal low flow from

July-October based on 29 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1,430 1,130 999 903 807 --

3 1,470 1,160 1,030 930 830 --

7 1,550 1,230 1,090 986 880 --

14 1,690 1,330 1,160 1,040 918 --

30 1,860 1,460 1,290 1,160 1,030 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 4,030 1,570 2,770 685 30

November 4,000 1,360 2,580 630 30

December 3,310 1,100 2,140 615 30

January 3,500 1,090 1,930 590 30

February 3,760 888 2,110 717 30

March 4,540 1,400 2,630 764 30

April 4,800 1,230 2,610 850 30

May 8,740 1,630 4,530 1,770 30

June 17,900 2,750 9,570 4,400 30

July 14,000 1,140 5,740 3,590 30

August 4,990 1,300 2,430 991 30

September 3,930 1,330 2,560 711 30

Annual 5,060 1,710 3,470 843 30
Statistical Summaries of Streamflow 191

06287000 Bighorn River near St. Xavier, Mont.—Continued

Site Number 169

Regulated streamflow period

Magnitude and probability of annual low flow

based on 37 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1,260 658 411 259 142 --

3 1,630 859 537 338 184 --

7 1,870 1,050 693 458 267 --

14 1,970 1,160 782 529 316 --

30 2,180 1,370 946 650 393 --

60 2,360 1,660 1,280 994 714 --

90 2,590 1,880 1,500 1,200 899 --

120 2,870 2,090 1,670 1,340 1,010 --

183 3,100 2,300 1,870 1,530 1,180 --

Magnitude and probability of seasonal low flow from

March-June based on 38 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 2,220 1,180 691 395 184 --

3 2,260 1,250 769 465 235 --

7 2,370 1,400 926 607 345 --

14 2,500 1,510 1,020 685 404 --

30 2,720 1,630 1,100 740 439 --

Magnitude and probability of seasonal low flow from

November-February based on 37 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 2,120 1,210 808 544 324 --

3 2,280 1,390 961 668 415 --

7 2,520 1,640 1,160 824 519 --

14 2,700 1,850 1,370 1,000 657 --

30 2,820 2,040 1,620 1,290 954 --

Duration of daily mean flows based on 38 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

626 1,130 1,550 1,760 2,180 2,510 2,840 3,180

40% 30% 20% 15% 10% 5% 2% 1%

3,570 3,950 4,450 5,120 5,800 7,340 8,700 11,500

Magnitude and probability of annual high flow

based on 38 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 7,400 12,000 15,400 20,200 24,100 --

3 7,260 11,600 14,900 19,500 23,200 --

7 7,060 11,200 14,300 18,600 22,100 --

15 6,750 10,600 13,400 17,200 20,300 --

30 6,220 9,430 11,800 14,900 17,400 --

60 5,440 7,800 9,390 11,400 12,900 --

90 4,960 6,810 8,000 9,450 10,500 --

Magnitude and probability of seasonal low flow from

July-October based on 37 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1,390 963 785 660 539 --

3 1,970 1,410 1,140 944 749 --

7 2,260 1,650 1,360 1,130 911 --

14 2,370 1,760 1,470 1,250 1,030 --

30 2,550 1,890 1,580 1,350 1,120 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 5,140 1,220 3,100 1,060 38

November 5,150 856 3,170 1,150 38

December 5,000 1,540 3,180 797 38

January 5,270 1,540 3,110 755 38

February 4,380 1,400 3,090 751 38

March 4,810 328 3,130 1,080 38

April 6,680 678 3,120 1,480 38

May 6,980 900 3,280 1,460 38

June 11,800 1,080 5,070 2,730 38

July 18,900 1,390 5,340 3,680 38

August 6,780 1,260 3,230 1,290 38

September 4,540 1,070 2,850 940 38

Annual 4,950 1,470 3,480 928 38
192 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06287500 Soap Creek near St. Xavier, Mont.

Site Number 170

LOCATION.--Lat 45°19'38", long 107°46'10" (NAD 27), in NE1⁄4 sec.10, T.6 S., R.32 E., Big Horn County, on left bank 6 mi upstream from mouth and 9.5 mi 

southwest of St. Xavier.

DRAINAGE AREA.--98.3 mi2 . 

PERIOD OF RECORD.--19 years. September 1911 to June 1912 (fragmentary daily discharge only), May to November 1913, March 1939 to September 1953, 

October 1967 to September 1972 (discontinued). April 1914 to September 1924, at sites about 5 mi downstream; records not equivalent owing to diversions.

REVISED RECORDS (WATER YEARS)--WSP 1309: 1940(M). WSP 1729: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 3,250 ft (NGVD 29, from topographic map). Prior to Mar. 26, 1939, nonrecording gage at site 0.5 mi 

downstream at different datum. 

REMARKS.--Diversions for irrigation of about 1,100 acres upstream from station.

Magnitude and probability of annual low flow

based on 18 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 12 6.7 4.1 2.4 -- --

3 12 6.9 4.4 2.8 -- --

7 12 8.0 6.0 4.5 -- --

14 13 9.2 7.2 5.8 -- --

30 15 11 8.6 7.1 -- --

60 17 12 9.8 8.2 -- --

90 18 13 11 9.7 -- --

120 19 15 13 11 -- --

183 20 16 13 12 -- --

Magnitude and probability of seasonal low flow from

March-June based on 19 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 19 12 9.2 7.0 -- --

3 19 13 11 8.8 -- --

7 21 15 12 10 -- --

14 24 16 13 11 -- --

30 27 19 16 13 -- --

Magnitude and probability of seasonal low flow from

November-February based on 19 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 12 6.8 4.1 2.5 -- --

3 13 7.0 4.5 2.9 -- --

7 13 8.1 6.0 4.6 -- --

14 14 9.3 7.3 5.8 -- --

30 16 11 8.9 7.3 -- --

Duration of daily mean flows based on 19 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

7.0 8.6 11 13 15 18 21 24

40% 30% 20% 15% 10% 5% 2% 1%

27 31 36 42 52 76 121 166

Magnitude and probability of annual high flow

based on 19 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 263 480 642 859 -- --

3 185 312 393 488 -- --

7 133 218 272 335 -- --

15 99 160 201 253 -- --

30 74 121 154 197 -- --

60 57 88 108 134 -- --

90 51 76 91 109 -- --

Magnitude and probability of seasonal low flow from

July-October based on 20 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 14 10 8.5 7.3 -- --

3 15 11 8.9 7.6 -- --

7 15 11 9.3 8.0 -- --

14 16 12 9.8 8.3 -- --

30 17 13 11 9.4 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 38 13 24 6.9 20

November 32 11 22 6.2 20

December 26 12 19 4.3 19

January 54 8.0 21 9.8 19

February 96 6.0 31 24 19

March 104 13 45 25 19

April 82 16 41 17 20

May 187 16 48 43 20

June 162 15 46 35 21

July 52 9.3 25 12 21

August 32 9.3 19 6.7 21

September 32 9.9 21 7.0 21

Annual 52 14 31 11 19
Statistical Summaries of Streamflow 193

06288500 Bighorn River near Hardin, Mont.

Site Number 171

LOCATION.--Lat 45°44' 20", long 107°34' 20" (NAD 27), in NW1⁄4 sec.19, T.1 S., R.34 E., Big Horn County, at highway bridge, 0.5 mi upstream from Little 

Bighorn River, and 2 mi east of Hardin.

DRAINAGE AREA.--20,722 mi2.

PERIOD OF RECORD.--25 years (1904-25, 1928-32).

GAGE.--Chain gage. Altitude of gage is 2,900 ft (NGVD 29, from topographic map). Prior to Dec. 1, 1917, chain or staff gage at railroad bridge 100 ft upstream 

at different datums.

REMARKS.--Diversion for irrigation of about 35,000 acres upstream from station. 

Magnitude and probability of annual low flow

based on 24 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1,050 719 566 453 -- --

3 1,100 769 609 491 -- --

7 1,140 813 654 534 -- --

14 1,210 892 735 615 -- --

30 1,320 1,020 867 751 -- --

60 1,470 1,190 1,060 945 -- --

90 1,620 1,300 1,150 1,030 -- --

120 1,750 1,410 1,260 1,150 -- --

183 2,010 1,620 1,480 1,380 -- --

Magnitude and probability of seasonal low flow from

March-June based on 26 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1,670 1,230 1,030 887 744 --

3 1,700 1,240 1,040 897 751 --

7 1,760 1,320 1,120 980 837 --

14 1,880 1,500 1,340 1,220 1,100 --

30 2,320 1,830 1,610 1,450 1,290 --

Magnitude and probability of seasonal low flow from

November-February based on 26 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1,130 811 652 532 410 --

3 1,170 860 700 577 450 --

7 1,200 899 745 625 501 --

14 1,240 951 807 695 579 --

30 1,330 1,090 974 886 792 --

Duration of daily mean flows based on 25 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

761 854 1,120 1,380 1,690 1,920 2,160 2,620

40% 30% 20% 15% 10% 5% 2% 1%

3,170 4,210 6,370 8,910 12,400 17,900 23,800 28,000

Magnitude and probability of annual high flow

based on 25 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 30,100 35,700 36,900 37,400 37,600 --

3 27,900 32,700 33,700 34,100 34,200 --

7 25,300 30,000 31,100 31,600 31,700 --

15 21,800 26,400 27,800 28,600 28,900 --

30 19,000 22,500 23,300 23,700 23,800 --

60 15,200 17,800 18,400 18,700 18,800 --

90 12,300 14,600 15,200 15,500 15,600 --

Magnitude and probability of seasonal low flow from

July-October based on 25 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1,770 1,160 878 672 478 --

3 1,800 1,190 900 692 496 --

7 1,850 1,230 940 731 533 --

14 1,930 1,310 1,020 808 605 --

30 2,130 1,480 1,190 973 763 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 9,500 1,490 2,790 1,660 26

November 4,890 1,210 2,280 838 26

December 3,400 1,000 1,880 556 26

January 2,720 941 1,520 409 26

February 2,550 814 1,680 389 26

March 10,700 1,690 3,420 2,030 26

April 13,800 1,440 3,500 2,430 26

May 15,800 3,060 6,760 2,750 26

June 24,900 2,530 16,100 4,680 26

July 22,300 607 10,200 4,940 26

August 8,920 1,120 4,280 1,860 26

September 5,380 1,270 2,870 1,110 27

Annual 8,020 1,870 4,790 1,180 25
194 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06289000 Little Bighorn River at State line, near Wyola, Mont.

Site Number 172

LOCATION.--Lat 45°00'25", long 107°36'52" (NAD 27), in SW1⁄4NW1⁄4 sec.36, T.9 S., R.33 E., Bighorn County, Hydrologic Unit 10080016, on right bank 20 ft 

downstream from county bridge, 0.5 mi north of Wyoming-Montana State line, 1 mi downstream from West Fork, 13 mi southwest of Wyola, and at river mile 

115.2.

DRAINAGE AREA.--182 mi2.

PERIOD OF RECORD.--March 1939 to current year (2002). Prior to October 1940, published as "Little Horn River at State line, near Wyola."

REVISED RECORDS.--WSP 1729: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 4,350 ft (NGVD 29).

REMARKS.--Diversions for irrigation of 163 acres upstream from station.

Magnitude and probability of annual low flow

based on 62 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 38 30 26 23 19 18

3 42 34 29 26 22 20

7 49 41 36 33 29 26

14 54 47 43 40 36 34

30 57 51 49 46 44 43

60 60 55 52 49 47 45

90 64 57 53 51 48 46

120 67 59 55 53 50 48

183 75 66 61 58 54 52

Magnitude and probability of seasonal low flow from

March-June based on 63 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 51 43 39 36 33 31

3 54 47 43 40 37 35

7 57 50 46 44 40 38

14 59 52 49 47 44 42

30 60 55 52 50 48 47

Magnitude and probability of seasonal low flow from

November-February based on 63 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 38 30 26 23 20 18

3 43 34 29 26 23 20

7 50 41 37 33 29 26

14 55 48 44 40 37 34

30 59 52 49 47 44 43

Duration of daily mean flows based on 63 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

38 46 49 53 62 70 79 87

40% 30% 20% 15% 10% 5% 2% 1%

99 123 179 240 342 516 784 985

Magnitude and probability of annual high flow

based on 63 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 831 1,180 1,410 1,710 1,920 2,140

3 771 1,080 1,280 1,520 1,690 1,860

7 711 992 1,170 1,380 1,530 1,670

15 631 879 1,040 1,230 1,370 1,500

30 552 764 899 1,060 1,180 1,300

60 428 578 673 788 870 949

90 345 458 527 610 668 725

Magnitude and probability of seasonal low flow from

July-October based on 63 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 76 64 58 53 48 45

3 79 68 63 59 54 51

7 80 70 65 61 57 54

14 82 71 66 62 58 56

30 85 74 68 64 60 57

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 120 61 87 15 63

November 104 55 76 12 63

December 91 47 68 10 63

January 85 44 63 8.7 63

February 88 48 62 8.1 63

March 86 49 62 7.9 63

April 172 51 85 25 64

May 533 126 324 97 64

June 1,120 145 515 242 64

July 689 95 219 96 64

August 228 70 123 31 64

September 151 64 98 20 64

Annual 253 79 149 37 63
Statistical Summaries of Streamflow 195

06290000 Pass Creek near Wyola, Mont.

Site Number 173

LOCATION.--Lat 45°03'23", long 107°21'19" (NAD 27), in NE1⁄4NE1⁄4SE1⁄4 sec.13, T.9 S., R.35 E., Big Horn County, Hydrologic Unit 10080016, on right bank 

125 ft downstream from bridge on U.S. Highway 87, 2.0 mi downstream from Twin Creek, 5.5 mi south of Wyola, and at river mile 10.2.

DRAINAGE AREA.--111 mi2. Drainage area at site used prior to Sept. 30, 1956, 119 mi2.

PERIOD OF RECORD.--June 1935 to September 1956 (no winter records prior to 1939), October 1982 to current year (2002).

GAGE.--Water-stage recorder. Altitude of gage is 3,920 ft (NGVD 29). Dec. 21, 1950, to Sept. 30, 1956, water-stage recorder, and June 4, 1935, to Dec. 20, 1950, 

nonrecording gage at site 0.3 mi upstream at different datum. Flow is equivalent.

REMARKS.--Diversions for irrigation of about 2,500 acres upstream from station. 

Magnitude and probability of annual low flow

based on 38 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 4.5 1.9 1.1 0.71 0.41 --

3 5.1 2.2 1.3 .81 .47 --

7 5.9 2.5 1.5 .95 .54 --

14 6.7 3.0 1.9 1.2 .73 --

30 8.1 4.2 2.9 2.0 1.3 --

60 10 5.6 3.9 2.8 1.9 --

90 12 7.5 5.7 4.4 3.3 --

120 14 9.4 7.6 6.3 5.0 --

183 15 11 9.4 8.1 6.8 --

Magnitude and probability of seasonal low flow from

March-June based on 39 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 16 11 9.4 8.0 6.8 --

3 17 12 10 8.5 7.2 --

7 19 14 11 9.6 8.0 --

14 23 16 13 11 9.5 --

30 29 20 16 13 11 --

Magnitude and probability of seasonal low flow from

November-February based on 38 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 7.7 4.9 3.8 3.0 2.2 --

3 8.6 5.5 4.3 3.4 2.6 --

7 9.6 6.4 5.1 4.2 3.3 --

14 11 7.7 6.2 5.1 4.1 --

30 14 9.7 7.9 6.6 5.2 --

Duration of daily mean flows based on 38 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

1.0 1.9 4.4 7.2 12 15 18 21

40% 30% 20% 15% 10% 5% 2% 1%

26 32 46 59 79 116 175 232

Magnitude and probability of annual high flow

based on 38 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 233 445 647 992 1,330 --

3 187 340 486 739 988 --

7 149 262 369 557 743 --

15 127 212 289 414 532 --

30 106 171 226 310 385 --

60 86 134 173 231 280 --

90 73 111 140 182 218 --

Magnitude and probability of seasonal low flow from

July-October based on 41 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 4.9 2.1 1.2 0.84 0.46 --

3 5.3 2.3 1.4 .91 .56 --

7 6.1 2.6 1.6 1.0 .60 --

14 6.8 3.1 2.0 1.3 .80 --

30 8.3 4.3 3.0 2.1 1.4 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 28 5.7 17 5.9 41

November 28 9.6 18 4.8 41

December 34 5.7 16 5.3 41

January 32 6.6 18 6.6 38

February 58 9.9 25 12 38

March 115 8.8 39 20 39

April 106 20 51 22 41

May 324 20 97 64 41

June 375 3.8 85 68 41

July 93 1.0 28 21 42

August 38 1.1 12 9.6 42

September 29 1.6 13 7.2 42

Annual 77 14 36 15 38
196 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06290500 Little Bighorn River below Pass Creek, near Wyola, Mont.

Site Number 174

LOCATION.--Lat 45°10'38", long 107°23'36" (NAD 27), in W1⁄2SW1⁄4 sec.35, T.7 S., R.35 E., Big Horn County, Hydrologic Unit 10080016, on right bank 3.5 mi 

north of Wyola, 6 mi downstream from Pass Creek, and at river mile 92.3.

DRAINAGE AREA.--428 mi2.

PERIOD OF RECORD.--March 1939 to December 1958, August 1959 to September 1975, October 1976 to current year (2002). Prior to October 1940, published 

as "Little Horn River below Pass Creek, near Wyola."

REVISED RECORDS.--WSP 1729: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 3,600 ft (NGVD 29).

REMARKS.--Diversions for irrigation of about 8,300 acres upstream from station. U.S. Geological Survey satellite telemeter at station.

Magnitude and probability of annual low flow

based on 58 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 57 38 30 24 18 15

3 63 43 33 27 20 16

7 71 49 39 31 23 18

14 78 56 45 36 27 22

30 87 63 51 41 31 26

60 94 71 60 51 42 36

90 100 79 68 60 51 46

120 105 86 76 69 61 56

183 108 90 81 74 67 62

Magnitude and probability of seasonal low flow from

March-June based on 61 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 99 75 60 48 35 28

3 100 78 65 55 44 37

7 104 83 71 61 50 44

14 111 88 76 67 57 51

30 128 99 86 75 64 58

Magnitude and probability of seasonal low flow from

November-February based on 61 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 61 44 36 30 24 21

3 67 50 42 36 30 26

7 76 59 50 44 38 34

14 85 68 60 53 46 41

30 94 78 69 63 56 51

Duration of daily mean flows based on 61 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

42 50 65 76 94 105 116 127

40% 30% 20% 15% 10% 5% 2% 1%

148 174 235 310 440 695 1,030 1,290

Magnitude and probability of annual high flow

based on 61 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 1,010 1,620 2,150 2,970 3,730 4,610

3 939 1,450 1,850 2,450 2,960 3,530

7 868 1,300 1,610 2,030 2,360 2,700

15 778 1,150 1,410 1,730 1,980 2,230

30 676 1,000 1,220 1,480 1,680 1,870

60 525 773 939 1,150 1,300 1,460

90 427 618 744 903 1,020 1,140

Magnitude and probability of seasonal low flow from

July-October based on 60 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 79 51 38 29 21 16

3 82 52 39 30 21 17

7 85 56 42 32 23 18

14 89 60 46 37 28 23

30 95 66 52 42 32 26

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 163 74 122 24 62

November 153 77 119 19 62

December 162 59 106 19 62

January 165 55 105 23 61

February 232 58 115 33 61

March 282 62 139 43 61

April 327 63 183 62 62

May 1,320 146 463 209 62

June 1,400 168 636 349 62

July 758 57 232 132 62

August 236 24 112 46 63

September 186 40 108 35 63

Annual 381 89 204 66 61
Statistical Summaries of Streamflow 197

06291000 Owl Creek near Lodge Grass, Mont.

Site Number 175

LOCATION.--Lat 45°16'05", long 107°18'03" (NAD 27), in NW1⁄4NE1⁄4SE1⁄4, sec.33, T.6 S., R.36 E., Big Horn County, Hydrologic Unit 10080016, on right bank 

1.4 mi downstream from Sioux Pass Creek, 5.0 mi southeast of Lodge Grass, and at river mile 7.0. 

DRAINAGE AREA.--163 mi2. 

PERIOD OF RECORD.--April 1939 to September 1945, October 1979 to September 1992 (discontinued). 

GAGE.--Water-stage recorder. Altitude of gage is 3,460 ft (NGVD 29, from topographic map). April 1939 to September 1945, recording gage at same site and 

datum. 

REMARKS.--Numerous diversions for irrigation upstream from station. 

Magnitude and probability of annual low flow

based on 18 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.46 0.05 0.00 0.00 -- --

3 .49 .05 .00 .00 -- --

7 .59 .06 .00 .00 -- --

14 .71 .06 .00 .00 -- --

30 .98 .15 .00 .00 -- --

60 1.3 .29 .09 .00 -- --

90 2.1 .57 .22 .08 -- --

120 2.3 1.1 .71 .48 -- --

183 2.9 1.4 .89 .58 -- --

Magnitude and probability of seasonal low flow from

March-June based on 19 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 3.0 0.87 0.37 0.17 -- --

3 3.4 .97 .41 .18 -- --

7 4.0 1.2 .52 .23 -- --

14 5.6 1.8 .76 .33 -- --

30 7.5 4.0 2.7 1.9 -- --

Magnitude and probability of seasonal low flow from

November-February based on 19 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1.1 0.32 0.15 0.08 -- --

3 1.2 .34 .16 .08 -- --

7 1.4 .38 .17 .09 -- --

14 1.7 .46 .21 .10 -- --

30 2.2 .73 .37 .20 -- --

Duration of daily mean flows based on 19 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

0.07 0.13 0.33 0.65 1.6 2.6 3.8 4.9

40% 30% 20% 15% 10% 5% 2% 1%

6.1 7.9 11 15 20 33 60 93

Magnitude and probability of annual high flow

based on 19 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 145 280 392 558 -- --

3 108 200 272 372 -- --

7 77 137 180 235 -- --

15 52 92 119 154 -- --

30 35 61 78 100 -- --

60 25 40 51 65 -- --

90 21 34 43 53 -- --

Magnitude and probability of seasonal low flow from

July-October based on 19 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.60 0.16 0.00 0.00 -- --

3 .63 .17 .00 .00 -- --

7 .72 .18 .00 .00 -- --

14 .82 .21 .00 .00 -- --

30 .99 .23 .00 .00 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 12 1.2 3.7 2.6 19

November 14 .38 4.6 3.1 19

December 18 .45 4.9 4.0 19

January 12 .28 4.7 3.2 19

February 48 .29 11 12 19

March 80 7.3 24 19 19

April 48 6.2 17 11 20

May 93 1.4 20 20 20

June 95 1.1 16 20 20

July 19 .13 4.7 4.3 20

August 7.5 .00 2.0 2.0 20

September 5.0 .00 2.1 1.6 20

Annual 23 2.5 9.7 5.2 19
198 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06291500 Lodge Grass Creek above Willow Creek Diversion, near Wyola, Mont.

Site Number 176

LOCATION.--Lat 45°07'39", long 107°36'01" (NAD 27), in SE1⁄4NE1⁄4NE1⁄4 sec.24, T.8 S., R.33 E., Big Horn County, Hydrologic Unit 10080016, on left bank 

0.2 mi upstream from Willow Creek diversion canal, 1.1 mi downstream from Spring Creek, 10 mi west of Wyola, 17 mi southwest of Lodge Grass, and at 

river mile 43.0.

DRAINAGE AREA.--80.7 mi2.

PERIOD OF RECORD.--March 1939 to September 1974, October 1982 to current year (2002).

REVISED RECORDS.--WSP 1559: 1944-47. WSP 1629: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 4,170 ft (NGVD 29). March 1939 to September 1974 recording gage 0.1 mi upstream at different datum. Flows 

are equivalent.

REMARKS.--Diversions for irrigation of about 400 acres upstream from station. 

Magnitude and probability of annual low flow

based on 53 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 8.4 5.7 4.5 3.7 2.9 2.5

3 9.2 6.4 5.1 4.2 3.3 2.8

7 10 7.3 5.9 4.8 3.8 3.2

14 12 8.5 7.1 6.0 5.0 4.3

30 14 10 8.6 7.3 6.0 5.2

60 15 12 10 8.8 7.4 6.6

90 16 13 11 9.9 8.6 7.8

120 17 13 12 11 9.5 8.7

183 18 15 13 12 10 9.3

Magnitude and probability of seasonal low flow from

March-June based on 55 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 13 9.5 7.5 6.0 4.6 3.8

3 14 10 8.1 6.5 5.0 4.1

7 15 11 8.9 7.2 5.5 4.5

14 16 12 10 9.0 7.6 6.8

30 18 14 12 11 9.8 9.0

Magnitude and probability of seasonal low flow from

November-February based on 55 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 8.9 6.1 4.9 4.0 3.2 2.7

3 9.7 6.8 5.5 4.6 3.7 3.1

7 11 7.8 6.4 5.4 4.4 3.8

14 12 8.9 7.5 6.3 5.2 4.6

30 14 10 8.7 7.4 6.1 5.3

Duration of daily mean flows based on 55 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

6.6 8.1 11 13 16 18 20 23

40% 30% 20% 15% 10% 5% 2% 1%

28 34 56 79 118 189 309 379

Magnitude and probability of annual high flow

based on 55 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 333 495 606 751 861 973

3 303 444 538 657 746 834

7 276 404 488 592 667 741

15 244 355 427 514 577 638

30 207 298 357 430 482 534

60 155 217 257 305 340 374

90 121 169 198 234 259 283

Magnitude and probability of seasonal low flow from

July-October based on 54 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 17 12 9.9 8.2 6.6 5.6

3 17 13 11 8.9 7.2 6.2

7 18 13 11 9.5 7.8 6.7

14 19 14 12 9.9 8.1 6.9

30 20 15 13 11 9.3 8.2

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 36 12 21 5.4 55

November 28 11 19 4.5 55

December 25 8.6 17 4.1 55

January 30 4.9 17 5.4 55

February 32 9.0 17 5.0 55

March 37 10 20 6.1 55

April 71 11 32 13 56

May 257 36 119 47 56

June 445 53 195 101 56

July 176 20 63 31 56

August 51 10 28 10 56

September 40 6.8 22 7.6 56

Annual 86 22 48 15 55
Statistical Summaries of Streamflow 199

06293500 Little Bighorn River near Crow Agency, Mont.

Site Number 177

LOCATION.--Lat 45°34'02", long 107°27'12" (NAD 27), in E1⁄2SE1⁄4 sec.13, T.3 S., R.34 E., Big Horn County, on right bank at Chicago, Burlington & Quincy 

Railroad bridge, 2 mi south of Crow Agency, and 17 mi upstream from mouth.

DRAINAGE AREA.--1,181 mi2 (revised).

PERIOD OF RECORD.--25 years (1928-29, 1930-32, 1938-60).

GAGE.--Water-stage recorder. Altitude of gage is 3,045 ft (NGVD 29). Apr. 11, 1912, to Sept. 30, 1918, staff or chain gage; Oct. 1, 1918, to Sept. 30, 1924, and 

Aug. 26, 1928, to Sept. 30, 1930, water-stage recorder; Oct. 1, 1930, to Dec. 5, 1932, and Apr. 1, 1938, to May 6, 1947, wire-weight or chain gage; all at same 

site and datum.

REMARKS.--Diversions for irrigation of 13,700 acres upstream from station. Flow partly regulated since about 1940 by Willow Creek Reservoir (capacity, 

23,000 acre-ft).

Magnitude and probability of annual low flow

based on 22 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 43 16 8.1 4.2 -- --

3 47 17 8.6 4.4 -- --

7 53 22 12 6.9 -- --

14 58 30 20 14 -- --

30 70 40 29 21 -- --

60 83 52 39 30 -- --

90 96 64 50 41 -- --

120 108 78 65 56 -- --

183 115 91 80 72 -- --

Magnitude and probability of seasonal low flow from

March-June based on 25 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 111 88 78 72 65 --

3 115 93 83 77 70 --

7 118 100 96 94 93 --

14 137 114 108 106 104 --

30 185 134 117 106 97 --

Magnitude and probability of seasonal low flow from

November-February based on 25 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 79 42 26 16 8.3 --

3 79 46 32 22 14 --

7 88 55 40 29 19 --

14 94 68 56 47 38 --

30 102 81 72 66 59 --

Duration of daily mean flows based on 25 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

24 33 51 73 101 121 144 168

40% 30% 20% 15% 10% 5% 2% 1%

196 261 407 518 701 1,020 1,420 1,840

Magnitude and probability of annual high flow

based on 25 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 1,480 2,500 3,280 4,380 5,290 --

3 1,280 2,080 2,690 3,540 4,230 --

7 1,080 1,660 2,080 2,640 3,090 --

15 887 1,330 1,660 2,100 2,460 --

30 732 1,100 1,380 1,780 2,110 --

60 571 853 1,070 1,370 1,610 --

90 492 717 878 1,100 1,270 --

Magnitude and probability of seasonal low flow from

July-October based on 36 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 57 20 8.9 4.8 0.00 --

3 62 22 9.5 5.0 .00 --

7 67 27 13 7.9 .00 --

14 75 34 21 15 5.5 --

30 81 46 32 24 16 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 861 58 167 127 37

November 566 96 163 79 32

December 202 74 132 30 25

January 337 66 123 54 25

February 362 83 159 70 25

March 946 115 326 195 25

April 1,800 114 347 299 38

May 1,080 155 555 249 40

June 2,030 125 782 407 40

July 680 50 271 172 40

August 275 24 113 66 39

September 382 20 121 73 40

Annual 436 144 248 93 25
200 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06294000 Little Bighorn River near Hardin, Mont.

Site Number 178

LOCATION.--Lat 45°44'09", long 107°33'24" (NAD 27), in SE1⁄4NE1⁄4NE1⁄4 sec.19, T.1 S., R.34 E., Big Horn County, Hydrologic Unit 10080016, on left bank 

50 ft downstream from bridge on Sarpy Road, 0.2 mi upstream from terminal wasteway of Agency Canal, 0.6 mi upstream from mouth, and 2.3 mi east of 

Hardin.

DRAINAGE AREA.--1,294 mi2.

PERIOD OF RECORD.--June 1953 to current year (2002).

REVISED RECORDS.--WDR MT-86-1: 1978.

GAGE.--Water-stage recorder. Altitude of gage is 2,882.29 ft (NGVD 29, levels by U.S. Army Corps of Engineers). Prior to Oct. 7, 1953, nonrecording gage at 

site 0.4 mi downstream. Oct. 7, 1953, to May 6, 1963, water-stage recorder at site 0.3 mi downstream. May 6, 1963, to Nov. 6, 1963, nonrecording gage at 

site 0.4 mi downstream. All at different datums. Nov. 7, 1963, to Aug. 15, 1976, water-stage recorder at site 35 ft downstream at present datum. Aug. 15, 

1976, to Sept. 30, 1979, water-stage recorders were located on each bank downstream from Sarpy Road bridge and were used depending on control conditions.

REMARKS.--Flow partly regulated by Willow Creek Reservoir (capacity, 23,000 acre-ft). Diversions for irrigation of 20,980 acres upstream from station. Figures 

of discharge given herein include flow of terminal wasteway of Agency Canal. U.S. Geological Survey satellite telemeter at station. Unpublished records of 

instantaneous water temperature and specific conductance are available in files of the U.S. Geological Survey Montana District Office.

Magnitude and probability of annual low flow

based on 48 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 55 22 10 4.6 1.6 --

3 63 27 12 5.5 1.8 --

7 74 33 16 7.2 2.4 --

14 79 37 20 11 4.5 --

30 94 46 26 14 6.6 --

60 107 57 35 21 11 --

90 119 67 44 29 17 --

120 124 81 61 47 34 --

183 131 93 76 63 50 --

Magnitude and probability of seasonal low flow from

March-June based on 49 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 130 72 49 34 21 --

3 139 79 54 37 23 --

7 152 88 61 43 28 --

14 182 108 75 53 34 --

30 213 130 95 71 50 --

Magnitude and probability of seasonal low flow from

November-February based on 49 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 64 41 30 22 15 --

3 74 48 35 26 18 --

7 88 60 46 35 25 --

14 99 72 60 50 40 --

30 112 86 74 65 55 --

Duration of daily mean flows based on 49 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

14 24 50 73 103 127 148 169

40% 30% 20% 15% 10% 5% 2% 1%

191 244 343 446 629 1,010 1,540 1,970

Magnitude and probability of annual high flow

based on 49 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 1,510 2,750 3,850 5,630 7,280 --

3 1,380 2,420 3,290 4,630 5,810 --

7 1,200 2,010 2,620 3,470 4,150 --

15 1,040 1,710 2,170 2,760 3,200 --

30 863 1,400 1,770 2,240 2,580 --

60 679 1,100 1,380 1,720 1,970 --

90 570 894 1,110 1,370 1,550 --

Magnitude and probability of seasonal low flow from

July-October based on 49 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 68 23 11 5.1 2.0 --

3 75 27 13 6.2 2.3 --

7 84 34 17 7.7 3.1 --

14 86 38 21 11 5.1 --

30 101 47 27 15 7.2 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 276 61 155 50 49

November 248 83 154 37 49

December 223 66 136 37 49

January 366 72 142 57 49

February 610 70 202 104 49

March 987 71 313 211 49

April 748 55 316 174 49

May 2,850 72 614 450 49

June 1,980 117 824 532 50

July 1,330 8.5 263 232 50

August 382 2.5 119 74 50

September 267 19 127 65 50

Annual 676 70 281 125 49
Statistical Summaries of Streamflow 201

06294500 Bighorn River above Tullock Creek, near Bighorn, Mont.

Site Number 179

LOCATION.--Lat 46°07'29", long 107°28'06" (NAD 27), in SE1⁄4SE1⁄4NE1⁄4 sec.3, T.4 N., R.34 E., Treasure County, Hydrologic Unit 10080015, on right bank 

1.9 mi upstream from Tullock Creek, 3.6 mi southwest of Bighorn, 4.5 mi southeast of Custer, and at river mile 3.0.

DRAINAGE AREA.--22,414 mi2. Area at site used Oct. 7, 1955, to Sept. 30, 1981, 22,885 mi2.

PERIOD OF RECORD.--October 1981 to current year (2002). Previously published as "06294700 Bighorn River at Bighorn, MT" 1956-81, and as "near Custer" 

1945-55. Flows are equivalent at all sites.

GAGE.--Water-stage recorder. Altitude of gage is 2,700 ft (NGVD 29). May 11, 1945 to Dec. 6, 1945, nonrecording gage, and Dec. 7, 1945, to Oct. 6, 1955, 

water-stage recorder 1.7 mi upstream at different datum. Oct. 7, 1955, to Sept. 30, 1981, at site 2.3 mi downstream at different datum.

REMARKS.--Flow regulated by Bighorn Lake beginning November 1965 (usable capacity, 1,312,000 acre-ft). Major regulation prior to November 1965 by 

14 reservoirs in Wyoming and 1 in Montana with combined usable capacity of about 1,400,000 acre-ft. Diversion for irrigation of about 445,200 acres upstream 

from station. U.S. Army Corps of Engineers satellite telemeter at station.

Unregulated streamflow period

Magnitude and probability of annual low flow

based on 18 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 988 717 600 514 -- --

3 1,120 828 690 586 -- --

7 1,310 951 768 627 -- --

14 1,510 1,080 857 689 -- --

30 1,680 1,220 997 824 -- --

60 1,970 1,470 1,210 1,010 -- --

90 2,160 1,660 1,410 1,210 -- --

120 2,360 1,890 1,660 1,470 -- --

183 2,560 2,020 1,730 1,500 -- --

Magnitude and probability of seasonal low flow from

March-June based on 19 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1,890 1,300 977 737 -- --

3 1,970 1,390 1,070 823 -- --

7 2,190 1,580 1,200 907 -- --

14 2,500 1,820 1,390 1,050 -- --

30 2,760 2,000 1,600 1,290 -- --

Magnitude and probability of seasonal low flow from

November-February based on 19 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1,190 874 752 668 -- --

3 1,280 1,000 896 825 -- --

7 1,480 1,230 1,140 1,080 -- --

14 1,740 1,490 1,400 1,330 -- --

30 2,050 1,720 1,560 1,440 -- --

Duration of daily mean flows based on 19 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

806 968 1,260 1,580 2,030 2,370 2,640 2,910

40% 30% 20% 15% 10% 5% 2% 1%

3,260 3,800 4,440 5,470 7,080 10,500 14,800 16,600

Magnitude and probability of annual high flow

based on 19 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 13,400 18,900 22,600 27,300 -- --

3 12,200 17,900 21,800 26,800 -- --

7 10,900 16,600 20,500 25,600 -- --

15 9,920 15,100 18,600 23,000 -- --

30 8,790 13,400 16,500 20,300 -- --

60 7,160 10,800 13,000 15,500 -- --

90 6,180 9,020 10,700 12,600 -- --

Magnitude and probability of seasonal low flow from

July-October based on 19 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1,330 898 712 579 -- --

3 1,370 931 742 607 -- --

7 1,450 999 805 666 -- --

14 1,630 1,120 894 730 -- --

30 1,840 1,250 1,000 836 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 4,060 1,760 3,130 618 19

November 4,180 1,360 3,030 648 19

December 3,690 1,280 2,600 560 19

January 3,890 1,380 2,380 595 19

February 4,450 1,950 2,720 738 19

March 5,380 1,540 3,520 1,180 19

April 5,230 1,220 3,200 982 19

May 9,100 1,600 4,650 1,870 19

June 15,200 2,380 9,070 4,320 20

July 12,600 707 5,290 3,580 20

August 4,860 868 2,330 1,050 20

September 4,110 1,630 2,750 725 20

Annual 5,500 1,620 3,670 999 19
202 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06294500 Bighorn River above Tullock Creek, near Bighorn, Mont.—Continued

Site Number 179

Regulated streamflow period

Magnitude and probability of annual low flow

based on 37 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1,390 910 703 556 418 --

3 1,650 1,080 830 656 493 --

7 1,860 1,240 971 779 596 --

14 1,980 1,350 1,070 874 679 --

30 2,160 1,560 1,280 1,080 876 --

60 2,450 1,830 1,530 1,310 1,070 --

90 2,730 2,020 1,660 1,390 1,120 --

120 2,950 2,140 1,740 1,440 1,140 --

183 3,210 2,340 1,890 1,550 1,200 --

Magnitude and probability of seasonal low flow from

March-June based on 38 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 2,370 1,460 1,050 770 519 --

3 2,460 1,560 1,160 876 616 --

7 2,590 1,700 1,300 1,020 760 --

14 2,740 1,840 1,450 1,180 913 --

30 2,970 2,000 1,590 1,300 1,030 --

Magnitude and probability of seasonal low flow from

November-February based on 37 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 2,060 1,310 988 760 548 --

3 2,280 1,490 1,120 863 619 --

7 2,530 1,710 1,310 1,020 733 --

14 2,730 1,900 1,480 1,170 860 --

30 2,910 2,140 1,750 1,440 1,130 --

Duration of daily mean flows based on 38 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

907 1,130 1,530 1,800 2,300 2,670 3,050 3,450

40% 30% 20% 15% 10% 5% 2% 1%

3,840 4,240 5,170 5,680 6,390 8,150 10,700 12,600

Magnitude and probability of annual high flow

based on 38 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 8,330 14,500 19,900 28,400 36,100 --

3 8,240 13,800 18,100 24,300 29,500 --

7 7,850 12,600 16,000 20,500 24,000 --

15 7,370 11,600 14,500 18,300 21,200 --

30 6,810 10,300 12,700 15,700 18,000 --

60 5,990 8,730 10,500 12,500 14,000 --

90 5,480 7,710 9,050 10,600 11,600 --

Magnitude and probability of seasonal low flow from

July-October based on 37 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1,580 1,120 927 788 652 --

3 1,970 1,410 1,160 978 798 --

7 2,180 1,590 1,320 1,110 911 --

14 2,320 1,680 1,380 1,160 939 --

30 2,490 1,790 1,470 1,240 1,000 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 5,550 1,260 3,310 1,170 38

November 5,600 1,220 3,460 1,230 38

December 4,910 1,590 3,440 831 38

January 5,480 1,620 3,380 808 38

February 5,310 1,790 3,460 904 38

March 6,580 908 3,810 1,360 38

April 7,880 1,060 3,750 1,670 38

May 8,890 1,300 4,290 1,980 38

June 12,700 1,050 5,900 3,200 38

July 19,100 951 5,390 3,820 38

August 6,970 930 3,150 1,350 38

September 4,950 1,010 2,910 965 38

Annual 5,590 1,530 3,860 1,080 38
Statistical Summaries of Streamflow 203

06294940 Sarpy Creek near Hysham, Mont.

Site Number 180

LOCATION.--Lat 46°14'19", long 107°08'12" (NAD 27), in NW1⁄4SE1⁄4SE1⁄4 sec.30, T.6 N., R.37 E., Treasure County, Hydrologic Unit 10100001, on left bank 

100 ft upstream from bridge on FAS Route 415, 1.3 mi upstream from Hysham Canal, 5.5 mi southeast of Hysham, and at river mile 11.0. 

DRAINAGE AREA.--453 mi2. 

PERIOD OF RECORD.--September 1973 to September 30, 1984 (discontinued). 

GAGE.--Water-stage recorder. Altitude of gage is 2,677.5 ft (NGVD 29). 

REMARKS.--Diversions for irrigation of about 970 acres upstream from station. 

Magnitude and probability of annual low flow

based on 10 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.00 0.00 0.00 0.00 -- --

3 .00 .00 .00 .00 -- --

7 .00 .00 .00 .00 -- --

14 .00 .00 .00 .00 -- --

30 .00 .00 .00 .00 -- --

60 .00 .00 .00 .00 -- --

90 .00 .00 .00 .00 -- --

120 .04 .00 .00 .00 -- --

183 .20 .02 .00 .00 -- --

Magnitude and probability of seasonal low flow from

March-June based on 11 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.22 0.01 0.00 0.00 -- --

3 .31 .06 .01 .00 -- --

7 .68 .26 .17 .12 -- --

14 1.3 .46 .27 .18 -- --

30 2.0 .79 .48 .31 -- --

Magnitude and probability of seasonal low flow from

November-February based on 11 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.00 0.00 0.00 0.00 -- --

3 .00 .00 .00 .00 -- --

7 .00 .00 .00 .00 -- --

14 .01 .00 .00 .00 -- --

30 .22 .00 .00 .00 -- --

Duration of daily mean flows based on 11 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

0.02 0.04 0.10 0.20 0.40 0.60 0.79 0.99

40% 30% 20% 15% 10% 5% 2% 1%

1.9 2.7 4.8 6.6 11 24 61 123

Magnitude and probability of annual high flow

based on 11 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 76 238 430 -- -- --

3 57 196 386 -- -- --

7 40 137 275 -- -- --

15 27 85 167 -- -- --

30 18 54 101 -- -- --

60 13 35 62 -- -- --

90 11 29 52 -- -- --

Magnitude and probability of seasonal low flow from

July-October based on 10 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.00 0.00 0.00 0.00 -- --

3 .00 .00 .00 .00 -- --

7 .00 .00 .00 .00 -- --

14 .00 .00 .00 .00 -- --

30 .00 .00 .00 .00 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 2.4 0.00 0.43 0.76 11

November 2.5 .00 .68 .95 11

December 3.4 .00 .91 1.1 11

January 46 .00 7.4 13 11

February 49 1.3 11 14 11

March 111 1.1 29 44 11

April 38 1.5 9.3 11 11

May 59 1.2 13 18 11

June 14 .25 5.2 4.3 11

July 2.9 .00 .79 1.1 11

August 1.2 .00 .21 .41 11

September 19 .00 1.6 5.4 12

Annual 20 1.5 6.6 6.9 11
204 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06294995 Armells Creek near Forsyth, Mont.

Site Number 181

LOCATION.--Lat 46°14'59", long 106°48'22" (NAD 27), in SE1⁄4NW1⁄4NE1⁄4 sec.26, T.6 N., R.39 E., Rosebud County, Hydrologic Unit 10100001, on right bank 

300 ft upstream from bridge on Interstate Highway 94, 2.2 mi upstream from mouth, and 6 mi southwest of Forsyth. 

DRAINAGE AREA.--370 mi2 . 

PERIOD OF RECORD.--July 1974 to September 1984, October 1987 to September 1995 (discontinued). 

GAGE.-- Water-stage recorder. Altitude of gage is 2,557.11 ft (NGVD 29). 

REMARKS.--Diversions for irrigation of about 200 acres upstream from station.

Magnitude and probability of annual low flow

based on 17 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.00 0.00 0.00 0.00 -- --

3 .00 .00 .00 .00 -- --

7 .00 .00 .00 .00 -- --

14 .00 .00 .00 .00 -- --

30 .01 .00 .00 .00 -- --

60 .05 .01 .00 .00 -- --

90 .09 .02 .01 .01 -- --

120 .13 .03 .01 .01 -- --

183 .38 .08 .04 .02 -- --

Magnitude and probability of seasonal low flow from

March-June based on 18 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.11 0.01 0.00 0.00 -- --

3 .17 .02 .00 .00 -- --

7 .40 .09 .04 .02 -- --

14 .77 .17 .06 .03 -- --

30 1.2 .33 .15 .07 -- --

Magnitude and probability of seasonal low flow from

November-February based on 18 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.02 0.00 0.00 0.00 -- --

3 .03 .00 .00 .00 -- --

7 .04 .00 .00 .00 -- --

14 .06 .00 .00 .00 -- --

30 .08 .01 .00 .00 -- --

Duration of daily mean flows based on 18 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

0.02 0.03 0.08 0.17 0.34 0.51 0.68 0.85

40% 30% 20% 15% 10% 5% 2% 1%

1.1 1.9 3.3 4.7 7.5 16 44 91

Magnitude and probability of annual high flow

based on 18 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 87 439 981 2,250 -- --

3 62 291 627 1,380 -- --

7 41 175 363 772 -- --

15 26 101 197 394 -- --

30 17 58 105 196 -- --

60 12 36 63 111 -- --

90 9.0 27 48 84 -- --

Magnitude and probability of seasonal low flow from

July-October based on 18 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.00 0.00 0.00 0.00 -- --

3 .00 .00 .00 .00 -- --

7 .01 .00 .00 .00 -- --

14 .02 .00 .00 .00 -- --

30 .05 .01 .00 .00 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 4.4 0.02 0.81 1.3 18

November 2.4 .00 .65 .77 18

December 2.6 .01 .53 .77 18

January 48 .00 4.3 11 18

February 52 .00 7.0 15 18

March 175 .04 27 49 18

April 25 .29 6.1 6.9 18

May 58 .27 9.6 16 18

June 23 .12 6.0 6.7 18

July 37 .01 2.9 8.4 19

August 5.7 .02 .98 1.5 19

September 26 .01 2.3 5.9 19

Annual 17 .38 5.8 6.0 18
Statistical Summaries of Streamflow 205

06295000 Yellowstone River at Forsyth, Mont.

Site Number 182

LOCATION.--Lat 46°15'58", long 106°41'24" (NAD 27), in NE1⁄4NW1⁄4NW1⁄4 sec.23, T.6 N., R.40 E., Rosebud County, Hydrologic Unit 10100001, on right bank 

0.3 mi downstream from U.S. Highway 12 bridge, at Forsyth, and at river mile 238.2.

DRAINAGE AREA.--40,146 mi2.

PERIOD OF RECORD.--July 16, 1921, to September 30, 1923 (no winter records), October 1977 to current year (2002). Miscellaneous discharge measurements 

were made in 1974 to 1976 and are available in files of U.S. Geological Survey Montana District Office.

GAGE.--Water-stage recorder. Altitude of gage is 2,504.62 ft (NGVD 29), from nearby elevation determined by City of Forsyth. July 1921 to March 1922, 

nonrecording gage on discontinued highway bridge 10 ft downstream from gage at different datum. March 1922 to September 1923, nonrecording gage on 

discontinued highway bridge 10 ft downstream from gage at datum 2 ft higher.

REMARKS.--Diversions for irrigation of about 838,000 acres upstream from station. Flow regulated to some extent by Bighorn Lake, usable capacity, 

1,312,000 acre-ft, on Bighorn River. Small diversion dam about 4,200 ft downstream from station. Bureau of Reclamation satellite telemeter at station.

Magnitude and probability of annual low flow

based on 24 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 3,230 2,320 1,920 1,640 -- --

3 3,460 2,520 2,100 1,800 -- --

7 3,880 2,970 2,560 2,260 -- --

14 4,630 3,620 3,090 2,670 -- --

30 5,150 4,100 3,520 3,050 -- --

60 5,460 4,400 3,820 3,340 -- --

90 5,890 4,780 4,170 3,670 -- --

120 6,200 5,040 4,420 3,910 -- --

183 6,610 5,240 4,530 3,980 -- --

Magnitude and probability of seasonal low flow from

March-June based on 25 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 5,200 3,600 2,830 2,250 1,690 --

3 5,320 3,760 3,000 2,440 1,880 --

7 5,460 4,060 3,400 2,900 2,390 --

14 5,900 4,610 4,030 3,590 3,150 --

30 6,260 4,850 4,240 3,790 3,340 --

Magnitude and probability of seasonal low flow from

November-February based on 25 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 3,350 2,360 1,930 1,650 1,320 --

3 3,630 2,600 2,140 1,820 1,450 --

7 4,080 3,200 2,790 2,480 2,160 --

14 4,650 3,760 3,330 2,990 2,630 --

30 5,250 4,410 3,970 3,610 3,230 --

Duration of daily mean flows based on 25 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

2,560 3,110 3,660 4,420 5,190 5,970 6,780 7,610

40% 30% 20% 15% 10% 5% 2% 1%

8,440 10,300 13,500 16,700 23,200 32,000 43,200 48,800

Magnitude and probability of annual high flow

based on 25 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 41,500 57,300 69,100 85,500 99,000 --

3 39,600 54,000 64,000 77,200 87,400 --

7 36,100 49,500 58,900 71,400 81,300 --

15 33,300 45,500 53,900 65,000 73,600 --

30 30,000 40,500 47,500 56,400 63,100 --

60 25,300 33,800 39,300 46,100 51,100 --

90 21,100 28,000 32,300 37,600 41,500 --

Magnitude and probability of seasonal low flow from

July-October based on 24 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 5,520 4,030 3,300 2,740 -- --

3 5,630 4,080 3,330 2,760 -- --

7 5,790 4,180 3,410 2,830 -- --

14 5,970 4,280 3,480 2,880 -- --

30 6,230 4,450 3,650 3,060 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 10,700 3,520 7,490 2,120 25

November 10,500 4,190 6,990 1,700 25

December 8,930 3,620 6,110 1,190 25

January 7,800 3,240 5,720 1,120 25

February 10,200 3,510 6,140 1,590 25

March 15,100 3,220 7,060 2,530 25

April 13,300 4,220 7,720 2,340 25

May 27,800 10,000 17,300 4,270 25

June 63,700 10,000 29,800 12,000 25

July 34,400 6,140 18,300 8,680 25

August 17,600 2,740 8,150 3,590 25

September 11,300 2,720 6,960 2,370 25

Annual 17,600 6,030 10,600 2,630 25
206 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06295113 Rosebud Creek at reservation boundary, near Kirby, Mont.

Site Number 183

LOCATION.--Lat 45°21'40", long 106°59'23" (NAD 27), in NE1⁄4NE1⁄4SW1⁄4 sec.36, T.5 S., R.38 E., Big Horn County, Hydrologic Unit 10100003, on right bank, 

0.2 mi upstream from Dry Creek, 0.5 mi north of reservation boundary, 1.9 mi downstream from Cache Creek, 2.0 mi north of Kirby, and at river mile 179.6.

DRAINAGE AREA.-- 123 mi2.

PERIOD OF RECORD.--October 1979 to current year (2002).

GAGE.--Water-stage recorder. Altitude of gage is 3,780 ft (NGVD 29).

REMARKS.--Numerous small diversions for irrigation upstream from station. 

Magnitude and probability of annual low flow

based on 22 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.51 0.07 0.00 0.00 -- --

3 .52 .08 .02 .00 -- --

7 .63 .12 .03 .00 -- --

14 .71 .22 .10 .05 -- --

30 1.1 .40 .21 .11 -- --

60 1.4 .67 .41 .26 -- --

90 1.7 .87 .58 .39 -- --

120 2.0 1.1 .73 .51 -- --

183 2.3 1.3 .90 .63 -- --

Magnitude and probability of seasonal low flow from

March-June based on 23 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 2.9 1.4 0.87 0.54 -- --

3 3.1 1.6 .99 .63 -- --

7 3.4 1.8 1.3 .89 -- --

14 4.2 2.5 1.8 1.3 -- --

30 5.9 3.4 2.4 1.8 -- --

Magnitude and probability of seasonal low flow from

November-February based on 22 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1.4 0.56 0.31 0.18 -- --

3 1.6 .67 .39 .23 -- --

7 1.8 .82 .49 .31 -- --

14 2.0 .97 .61 .40 -- --

30 2.4 1.3 .87 .61 -- --

Duration of daily mean flows based on 23 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

0.10 0.20 0.49 0.98 1.6 2.2 2.9 3.6

40% 30% 20% 15% 10% 5% 2% 1%

4.6 6.0 9.5 12 15 21 32 42

Magnitude and probability of annual high flow

based on 23 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 44 81 105 133 -- --

3 38 70 92 117 -- --

7 31 56 74 95 -- --

15 25 42 52 62 -- --

30 21 32 37 42 -- --

60 17 25 28 31 -- --

90 15 21 24 26 -- --

Magnitude and probability of seasonal low flow from

July-October based on 22 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.53 0.09 0.00 0.00 -- --

3 .57 .10 .03 .00 -- --

7 .67 .13 .04 .01 -- --

14 .74 .23 .11 .06 -- --

30 1.1 .42 .22 .12 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 8.0 0.33 2.9 1.6 23

November 12 .37 3.3 2.3 23

December 13 .34 3.3 2.4 23

January 10 1.0 3.4 1.9 23

February 29 1.0 6.3 6.0 23

March 42 1.0 13 10 23

April 41 2.3 15 9.6 23

May 24 1.8 12 6.2 23

June 20 1.0 8.5 5.0 23

July 11 .03 3.6 2.8 23

August 4.6 .01 1.6 1.3 23

September 3.2 .00 1.6 .93 23

Annual 12 .77 6.3 2.7 23
Statistical Summaries of Streamflow 207

06295250 Rosebud Creek near Colstrip, Mont.

Site Number 184

LOCATION.--Lat 45°46'03", long 106°34'10" (NAD 27), in SE1⁄4SW1⁄4NE1⁄4 sec.8, T.1 S., R.42 E., Rosebud County, Hydrologic Unit 10100003, on left bank 10 ft 

downstream from bridge on FAS Route 315, 1.5 mi downstream from Lee Coulee, 8.4 mi southeast of Colstrip, and at river mile 85.6.

DRAINAGE AREA.--799 mi2.

PERIOD OF RECORD.--October 1974 to current year (2002).

GAGE.--Water-stage recorder. Altitude of gage is 3,000 ft (NGVD 29).

REMARKS.--Diversions for irrigation of about 800 acres upstream from station. 

Magnitude and probability of annual low flow

based on 27 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.51 0.00 0.00 0.00 0.00 --

3 .62 .00 .00 .00 .00 --

7 .94 .00 .00 .00 .00 --

14 1.2 .00 .00 .00 .00 --

30 1.3 .00 .00 .00 .00 --

60 2.0 .00 .00 .00 .00 --

90 2.8 .35 .05 .00 .00 --

120 5.3 1.0 .31 .10 .02 --

183 6.2 2.3 1.3 .79 .44 --

Magnitude and probability of seasonal low flow from

March-June based on 28 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 9.7 4.7 3.1 1.9 0.00 --

3 10 4.9 3.3 2.1 .00 --

7 17 5.7 3.5 2.1 .14 --

14 18 6.1 3.7 2.3 .14 --

30 19 7.6 4.4 2.7 1.5 --

Magnitude and probability of seasonal low flow from

November-February based on 27 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 6.0 1.4 0.35 0.04 0.00 --

3 6.8 1.6 .41 .06 .00 --

7 7.1 1.8 .62 .21 .05 --

14 8.9 2.8 1.1 .38 .09 --

30 11 3.6 1.4 .49 .12 --

Duration of daily mean flows based on 28 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

0.10 0.19 0.49 0.97 4.2 6.3 8.9 13

40% 30% 20% 15% 10% 5% 2% 1%

17 23 32 40 53 84 158 229

Magnitude and probability of annual high flow

based on 28 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 98 232 367 603 832 --

3 85 204 328 549 772 --

7 73 174 280 474 671 --

15 60 138 219 366 516 --

30 49 107 167 276 388 --

60 40 85 130 212 295 --

90 35 73 110 176 241 --

Magnitude and probability of seasonal low flow from

July-October based on 27 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.61 0.00 0.00 0.00 0.00 --

3 .70 .00 .00 .00 .00 --

7 1.1 .00 .00 .00 .00 --

14 1.3 .00 .00 .00 .00 --

30 1.4 .00 .00 .00 .00 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 48 0.00 9.6 12 28

November 46 .03 12 11 28

December 46 .41 13 11 28

January 70 3.0 15 14 28

February 105 5.0 27 24 28

March 164 7.4 46 38 28

April 185 8.9 41 38 28

May 306 4.2 52 72 28

June 212 .78 36 52 28

July 104 .00 19 26 28

August 57 .00 9.2 15 28

September 56 .00 6.8 13 28

Annual 96 3.0 24 23 28
208 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06296003 Rosebud Creek at mouth, near Rosebud, Mont.

Site Number 185

LOCATION.--Lat 46°15'53", long 106°28'30" (NAD 27), in SW1⁄4NW1⁄4NE1⁄4 sec.21, T.6 N., R.42 E., Rosebud County, Hydrologic Unit 10100003, on left bank 

0.4 mi upstream from bridge on Interstate Highway 94, 0.8 mi upstream from mouth, and 1.6 mi southwest of Rosebud.

DRAINAGE AREA.--1,302 mi2.

PERIOD OF RECORD.--October 1974 to current year (2002).

GAGE.--Water-stage recorder. Altitude of gage is 2,480 ft (NGVD 29).

REMARKS.--Diversions for irrigation of about 2,000 acres upstream from station.

Magnitude and probability of annual low flow

based on 27 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.18 0.00 0.00 0.00 0.00 --

3 .20 .00 .00 .00 .00 --

7 .25 .01 .00 .00 .00 --

14 .29 .01 .00 .00 .00 --

30 .42 .01 .00 .00 .00 --

60 .69 .06 .01 .00 .00 --

90 1.5 .15 .04 .01 .00 --

120 2.3 .37 .12 .05 .01 --

183 4.0 .75 .26 .10 .03 --

Magnitude and probability of seasonal low flow from

March-June based on 28 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 2.0 0.30 0.07 0.00 0.00 --

3 2.6 .38 .08 .00 .00 --

7 3.6 .54 .18 .07 .02 --

14 6.0 .93 .31 .11 .03 --

30 10 1.7 .60 .22 .07 --

Magnitude and probability of seasonal low flow from

November-February based on 27 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1.7 0.14 0.00 0.00 0.00 --

3 2.1 .15 .01 .00 .00 --

7 2.2 .22 .04 .00 .00 --

14 2.6 .27 .05 .00 .00 --

30 3.8 .50 .13 .04 .01 --

Duration of daily mean flows based on 28 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

0.04 0.08 0.20 0.41 0.81 2.0 4.5 8.0

40% 30% 20% 15% 10% 5% 2% 1%

14 23 36 45 63 115 213 319

Magnitude and probability of annual high flow

based on 28 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 216 580 1,020 1,930 2,980 --

3 161 455 818 1,580 2,480 --

7 115 322 579 1,120 1,760 --

15 88 237 409 746 1,110 --

30 70 178 286 472 649 --

60 54 131 200 307 400 --

90 46 109 165 251 324 --

Magnitude and probability of seasonal low flow from

July-October based on 27 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.18 0.00 0.00 0.00 0.00 --

3 .22 .00 .00 .00 .00 --

7 .31 .01 .00 .00 .00 --

14 .35 .02 .00 .00 .00 --

30 .47 .03 .00 .00 .00 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 46 0.00 8.4 11 28

November 48 .01 9.4 12 28

December 48 .03 10 12 28

January 159 .03 19 31 28

February 187 .07 38 51 28

March 428 .04 72 93 28

April 180 5.0 44 42 28

May 478 .39 61 104 28

June 286 .48 41 62 28

July 133 .00 18 33 28

August 48 .00 8.2 12 28

September 77 .00 8.6 19 28

Annual 112 1.0 28 29 28
Statistical Summaries of Streamflow 209

06306300 Tongue River at State line, near Decker, Mont.

Site Number 186

LOCATION.--Lat 45°00'32", long 106°50'08" (NAD 27), in NW1⁄4NW1⁄4NE1⁄4 sec.33, T.9 S., R.40 E., Big Horn County, Hydrologic Unit 10090101, on left bank 

1 mi north of Wyoming-Montana State line, 1.4 mi southeast of Decker, 1.6 mi upstream from Badger Creek, and at river mile 200.9.

DRAINAGE AREA.--1,453 mi2.

PERIOD OF RECORD.--August 1960 to current year (2002). Records published as "near Decker" May 1928 to September 1938, not equivalent owing to 

intervening drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 3,429.14 ft (NGVD 29, levels by U.S. Army Corps of Engineers).

REMARKS.--Flow regulated by many small reservoirs in Wyoming (combined capacity, about 15,000 acre-ft). Diversions for irrigation of about 64,300 acres 

upstream from station. U.S. Geological Survey satellite telemeter at station.

Magnitude and probability of annual low flow

based on 41 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 88 50 30 18 9.0 --

3 94 53 33 20 10 --

7 102 57 35 21 11 --

14 113 63 40 25 13 --

30 127 74 48 31 18 --

60 147 91 64 46 29 --

90 164 115 91 73 55 --

120 184 139 116 98 79 --

183 197 153 131 115 97 --

Magnitude and probability of seasonal low flow from

March-June based on 42 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 165 118 97 82 67 --

3 174 126 105 88 72 --

7 187 139 118 102 86 --

14 213 163 140 122 104 --

30 247 183 154 133 112 --

Magnitude and probability of seasonal low flow from

November-February based on 42 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 93 69 58 51 42 --

3 102 77 65 57 48 --

7 117 89 76 66 56 --

14 135 103 87 75 63 --

30 154 118 100 86 71 --

Duration of daily mean flows based on 42 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

45 64 86 114 153 185 214 242

40% 30% 20% 15% 10% 5% 2% 1%

270 343 486 680 1,070 1,830 2,760 3,380

Magnitude and probability of annual high flow

based on 42 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 2,820 4,680 5,960 7,570 8,750 --

3 2,610 4,140 5,090 6,190 6,940 --

7 2,350 3,600 4,310 5,070 5,560 --

15 2,100 3,170 3,750 4,350 4,710 --

30 1,830 2,780 3,290 3,810 4,120 --

60 1,370 2,070 2,450 2,860 3,110 --

90 1,080 1,580 1,860 2,150 2,330 --

Magnitude and probability of seasonal low flow from

July-October based on 41 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 116 57 32 19 9.4 --

3 118 58 34 21 11 --

7 124 61 36 22 12 --

14 132 67 41 26 14 --

30 148 78 49 32 18 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 402 116 253 67 42

November 324 126 224 47 42

December 271 102 179 44 42

January 330 79 177 54 42

February 672 80 229 101 42

March 855 88 303 148 42

April 676 124 355 129 42

May 3,280 268 1,140 549 42

June 3,570 176 1,640 945 42

July 1,670 55 461 329 42

August 475 13 176 102 42

September 615 47 214 107 43

Annual 862 138 446 156 42
210 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06307500 Tongue River at Tongue River Dam, near Decker, Mont.

Site Number 187

LOCATION.--Lat 45°08'29", long 106°46'15" (NAD 27), in SW1⁄4SE1⁄4SE1⁄4 sec.12, T.8 S., R.40 E., Big Horn County, Hydrologic Unit 10090101, on left bank 

0.5 mi downstream from Tongue River Dam, 4 mi upstream from Post Creek, 8 mi northeast of Decker, 16 mi southeast of Kirby, and at river mile 188.4.

DRAINAGE AREA.--1,770 mi2.

PERIOD OF RECORD.--May 1939 to current year (2002).

REVISED RECORDS.--WSP 1729: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 3,344.40 ft (NGVD 29, levels by Bureau of Reclamation). Prior to Aug. 5, 1975, at datum 10.00 ft lower.

REMARKS.--Flow regulated by Tongue River Reservoir (station number 06307000) and many small reservoirs (combined capacity, about 15,000 acre-ft). 

Diversion for irrigation of about 64,800 acres upstream from station. U.S. Geological Survey satellite telemeter at station. 

Magnitude and probability of annual low flow

based on 62 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 67 25 12 5.8 2.2 1.1

3 82 33 16 7.4 2.6 1.2

7 104 48 23 10 3.4 1.4

14 127 74 45 15 4.3 2.6

30 128 75 49 32 19 12

60 150 99 73 53 36 26

90 171 128 105 86 68 56

120 194 143 117 97 77 65

183 232 174 145 123 100 87

Magnitude and probability of seasonal low flow from

March-June based on 63 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 118 42 19 8.1 2.7 1.1

3 136 53 23 10 3.2 1.3

7 169 75 34 15 4.4 1.7

14 185 82 47 16 4.7 2.8

30 198 100 61 38 21 13

Magnitude and probability of seasonal low flow from

November-February based on 63 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 114 59 36 23 12 7.7

3 128 73 47 30 17 11

7 140 86 56 36 20 13

14 141 92 69 53 37 29

30 146 103 82 66 50 41

Duration of daily mean flows based on 63 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

46 59 83 115 153 183 220 260

40% 30% 20% 15% 10% 5% 2% 1%

327 412 524 669 930 1,530 2,420 3,000

Magnitude and probability of annual high flow

based on 63 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 2,210 3,660 4,550 5,530 6,160 6,720

3 2,130 3,440 4,190 4,980 5,460 5,870

7 1,990 3,170 3,840 4,540 4,960 5,320

15 1,770 2,810 3,410 4,060 4,470 4,820

30 1,480 2,380 2,930 3,570 4,000 4,380

60 1,130 1,790 2,200 2,700 3,040 3,360

90 936 1,410 1,710 2,060 2,300 2,530

Magnitude and probability of seasonal low flow from

July-October based on 63 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 108 63 46 36 27 22

3 118 71 54 43 33 28

7 132 85 68 57 47 42

14 156 101 80 67 54 47

30 196 132 106 88 71 61

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 665 71 274 127 63

November 554 41 254 133 63

December 369 62 188 57 63

January 287 80 173 42 63

February 592 57 180 74 63

March 676 23 224 128 63

April 958 15 362 217 63

May 2,710 157 903 493 63

June 3,820 183 1,430 892 64

July 2,080 169 571 327 64

August 768 103 361 156 64

September 775 107 308 132 64

Annual 853 133 437 152 63
Statistical Summaries of Streamflow 211

06307600 Hanging Woman Creek near Birney, Mont.

Site Number 188

LOCATION.--Lat 45°17’57", long 106°30'28" (NAD 27), in N1⁄2NW1⁄4SE1⁄4 sec.19, T.6 S., R.43 E., Rosebud County, Hydrologic Unit 10090101, on right bank 

0.5 mi downstream from bridge on Birney-Otter road, 1.2 mi south of Birney, 1.2 mi downstream from East Fork, and at river mile 3.3. 

DRAINAGE AREA.--470 mi2. 

PERIOD OF RECORD.--September 1973 to September 1984, October 1985 to September 1995. 

REVISED RECORDS.--WDR MT-82-1: 1980 (M). 

GAGE.--Water-stage recorder. Altitude of gage is 3,150 ft (NGVD 29, from topographic map). 

REMARKS.-- Diversions for irrigation of about 1,240 acres upstream from station. 

Magnitude and probability of annual low flow

based on 20 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.03 0.00 0.00 0.00 -- --

3 .03 .00 .00 .00 -- --

7 .06 .00 .00 .00 -- --

14 .07 .00 .00 .00 -- --

30 .15 .00 .00 .00 -- --

60 .18 .01 .00 .00 -- --

90 .33 .03 .00 .00 -- --

120 .39 .04 .00 .00 -- --

183 .46 .14 .07 .04 -- --

Magnitude and probability of seasonal low flow from

March-June based on 21 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.35 0.10 0.02 0.00 -- --

3 .48 .11 .04 .01 -- --

7 .56 .17 .08 .04 -- --

14 .71 .26 .15 .09 -- --

30 .94 .44 .30 .22 -- --

Magnitude and probability of seasonal low flow from

November-February based on 21 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.35 0.02 0.00 0.00 -- --

3 .42 .03 .00 .00 -- --

7 .42 .05 .01 .00 -- --

14 .46 .11 .04 .00 -- --

30 .54 .18 .09 .01 -- --

Duration of daily mean flows based on 21 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

0.02 0.04 0.09 0.18 0.37 0.55 0.74 0.92

40% 30% 20% 15% 10% 5% 2% 1%

1.2 1.7 2.4 3.1 4.3 8.7 23 44

Magnitude and probability of annual high flow

based on 21 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 116 430 772 1,340 -- --

3 74 257 448 760 -- --

7 44 138 232 380 -- --

15 26 73 116 181 -- --

30 16 41 65 103 -- --

60 9.4 23 36 56 -- --

90 7.0 17 25 39 -- --

Magnitude and probability of seasonal low flow from

July-October based on 20 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.06 0.00 0.00 0.00 -- --

3 .06 .00 .00 .00 -- --

7 .09 .00 .00 .00 -- --

14 .10 .00 .00 .00 -- --

30 .16 .00 .00 .00 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 3.0 0.00 0.68 0.72 21

November 3.0 .00 .88 .76 21

December 3.1 .06 .95 .79 21

January 21 .30 2.6 5.2 21

February 71 .36 10 17 21

March 93 .57 9.8 20 21

April 17 .50 2.9 3.6 21

May 98 .41 6.6 21 21

June 13 .20 3.7 4.1 21

July 19 .00 2.8 4.4 21

August 7.2 .00 1.0 1.6 21

September 2.3 .00 .48 .61 22

Annual 14 .35 3.5 3.4 21
212 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06307616 Tongue River at Birney Day School Bridge, near Birney, Mont.

Site Number 189

LOCATION.--Lat 45°24'42", long 106°27'26" (NAD 27), in SE1⁄4SW1⁄4SW1⁄4 sec.8, T.5 S., R.43 E., Rosebud County, Hydrologic Unit 10090102, on left bank, 

60 ft upstream from Bureau of Indian Affairs bridge, 0.2 mi east of Birney Day School, 5.5 mi downstream from Cook Creek, 6.5 mi northeast of Birney, and 

at river mile 144.3.

DRAINAGE AREA.--2,621 mi2.

PERIOD OF RECORD.--October 1979 to current year (2002).

GAGE.--Water-stage recorder. Altitude of gage is 3,060 ft (NGVD 29).

REMARKS.--Flow regulated by Tongue River Reservoir (station number 06307000), and many small reservoirs in Wyoming (combined capacity, about 

15,000 acre-ft). Numerous diversions for irrigation upstream from station. 

Magnitude and probability of annual low flow

based on 22 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 74 49 39 31 -- --

3 85 56 44 35 -- --

7 96 64 49 38 -- --

14 108 74 59 48 -- --

30 130 92 74 61 -- --

60 149 108 88 73 -- --

90 179 131 105 84 -- --

120 194 143 116 94 -- --

183 230 172 142 119 -- --

Magnitude and probability of seasonal low flow from

March-June based on 23 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 123 74 54 41 -- --

3 132 80 58 43 -- --

7 144 88 63 46 -- --

14 159 95 71 54 -- --

30 183 113 86 68 -- --

Magnitude and probability of seasonal low flow from

November-February based on 22 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 101 65 50 39 -- --

3 112 77 61 49 -- --

7 125 88 70 57 -- --

14 141 101 81 66 -- --

30 161 120 97 78 -- --

Duration of daily mean flows based on 23 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

64 71 87 120 162 197 230 262

40% 30% 20% 15% 10% 5% 2% 1%

313 370 467 520 710 1,230 2,020 2,570

Magnitude and probability of annual high flow

based on 23 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 1,810 2,850 3,430 4,030 -- --

3 1,700 2,750 3,340 3,950 -- --

7 1,590 2,600 3,180 3,790 -- --

15 1,410 2,320 2,830 3,380 -- --

30 1,170 1,940 2,430 3,000 -- --

60 889 1,420 1,760 2,160 -- --

90 747 1,140 1,380 1,680 -- --

Magnitude and probability of seasonal low flow from

July-October based on 22 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 142 89 69 56 -- --

3 157 97 75 60 -- --

7 172 110 85 68 -- --

14 196 129 100 80 -- --

30 233 161 128 104 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 381 85 246 83 23

November 347 66 219 77 23

December 260 64 179 49 23

January 287 91 179 45 23

February 350 90 197 60 23

March 434 78 226 94 23

April 583 66 275 157 23

May 1,770 144 654 397 23

June 2,920 225 1,120 745 23

July 1,270 234 556 257 23

August 676 159 399 136 23

September 694 113 320 137 23

Annual 644 133 381 127 23
Statistical Summaries of Streamflow 213

06307740 Otter Creek at Ashland, Mont.

Site Number 190

LOCATI0N.--Lat 45°35'18", long 106°15'17" (NAD 27), in NE1⁄4NE1⁄4SE1⁄4 sec.11, T.3 S., R.44 E., Rosebud County, Hydrologic Unit 10090102, on left bank 

200 ft downstream from bridge on U.S. Highway 212, 0.3 mi southeast of Ashland, and at river mile 2.7.

DRAINAGE AREA.--707 mi2. 

PERIOD OF RECORD.--October 1972 to November 1985, October 1987 to September 1995. 

GAGE.--Water-stage recorder. Altitude of gage is 2,916.57 ft (NGVD 29). 

REMARKS.--Diversion for irrigation of about 4,200 acres upstream from station.

Magnitude and probability of annual low flow

based on 19 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.00 0.00 0.00 0.00 -- --

3 .04 .00 .00 .00 -- --

7 .06 .00 .00 .00 -- --

14 .12 .00 .00 .00 -- --

30 .27 .00 .00 .00 -- --

60 .41 .08 .02 .00 -- --

90 .70 .14 .04 .01 -- --

120 .75 .32 .20 .14 -- --

183 1.2 .60 .41 .31 -- --

Magnitude and probability of seasonal low flow from

March-June based on 21 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.91 0.21 0.04 0.00 -- --

3 1.3 .23 .05 .00 -- --

7 1.4 .38 .14 .01 -- --

14 1.9 .81 .49 .31 -- --

30 2.4 1.1 .67 .45 -- --

Magnitude and probability of seasonal low flow from

November-February based on 20 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.88 0.23 0.00 0.00 -- --

3 1.0 .25 .08 .00 -- --

7 1.1 .38 .17 .02 -- --

14 1.4 .43 .19 .09 -- --

30 1.7 .64 .34 .19 -- --

Duration of daily mean flows based on 21 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

0.03 0.07 0.16 0.33 0.66 0.99 1.5 2.2

40% 30% 20% 15% 10% 5% 2% 1%

2.9 3.9 5.4 6.6 8.1 14 28 56

Magnitude and probability of annual high flow

based on 21 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 34 112 207 397 -- --

3 26 88 168 337 -- --

7 20 64 118 229 -- --

15 15 44 78 144 -- --

30 11 30 52 95 -- --

60 8.2 21 34 58 -- --

90 7.3 17 27 45 -- --

Magnitude and probability of seasonal low flow from

July-October based on 20 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.01 0.00 0.00 0.00 -- --

3 .05 .00 .00 .00 -- --

7 .07 .00 .00 .00 -- --

14 .13 .00 .00 .00 -- --

30 .28 .00 .00 .00 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 4.4 0.18 1.4 1.3 22

November 6.1 .71 2.5 1.5 22

December 7.0 .57 2.5 1.8 21

January 30 .10 4.9 7.7 21

February 35 .35 7.1 8.4 21

March 106 1.3 15 24 21

April 28 .99 6.5 6.6 21

May 53 .71 7.3 11 21

June 16 .36 4.4 3.9 21

July 8.9 .28 2.3 2.2 21

August 5.5 .00 1.4 1.7 21

September 4.1 .00 .89 1.0 21

Annual 19 .60 4.7 4.3 21
214 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06307830 Tongue River below Brandenberg Bridge, near Ashland, Mont.

Site Number 191

LOCATION.--Lat 45°50'24", long 106°13'22" (NAD 27), in SE1⁄4SW1⁄4NE1⁄4 sec.14, T.1N., R.44E., Rosebud County, Hydrologic Unit 10090102, on right bank 

downstream from county bridge, 22 mi north of Ashland, and at river mile 81.3.

DRAINAGE AREA.--3,948 mi2. Area at site used prior to Sept. 20, 1984, 4,062 mi2.

PERIOD OF RECORD.--October 1973 to September 20, 1984, July 2000 to current year (2002).

GAGE.--Water-stage recorder. Altitude of gage is 2,760 ft (NGVD 29), from topographic map. October 1973 to Sept. 20, 1984, water-stage recorder at site 6.5 mi 

downstream at different datum.

REMARKS.--Flow regulated by Tongue River Reservoir (station number 06307000), and many small reservoirs in Wyoming (combined capacity, about 

15,000 acre-ft). Diversions for irrigation for about 73,000 acres upstream from station. U.S. Geological Survey satellite telemeter at station.

Magnitude and probability of annual low flow

based on 11 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 80 62 54 48 -- --

3 88 69 60 54 -- --

7 105 80 68 59 -- --

14 119 89 74 63 -- --

30 134 102 87 75 -- --

60 161 126 109 97 -- --

90 189 144 121 104 -- --

120 208 155 129 108 -- --

183 249 187 152 123 -- --

Magnitude and probability of seasonal low flow from

March-June based on 13 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 161 113 92 76 -- --

3 172 120 95 77 -- --

7 188 126 98 79 -- --

14 199 129 100 81 -- --

30 232 142 107 84 -- --

Magnitude and probability of seasonal low flow from

November-February based on 12 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 81 63 55 49 -- --

3 89 70 61 55 -- --

7 107 82 69 59 -- --

14 122 92 77 66 -- --

30 141 110 94 81 -- --

Duration of daily mean flows based on 13 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

71 79 100 125 168 209 249 297

40% 30% 20% 15% 10% 5% 2% 1%

353 422 504 615 904 1,450 2,580 3,410

Magnitude and probability of annual high flow

based on 13 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 1,860 3,450 4,760 6,730 -- --

3 1,840 3,350 4,470 5,950 -- --

7 1,750 3,170 4,100 5,170 -- --

15 1,590 2,930 3,790 4,790 -- --

30 1,320 2,500 3,330 4,390 -- --

60 1,000 1,880 2,530 3,390 -- --

90 831 1,510 2,000 2,640 -- --

Magnitude and probability of seasonal low flow from

July-October based on 12 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 220 167 137 112 -- --

3 228 169 137 112 -- --

7 233 172 139 113 -- --

14 239 176 143 117 -- --

30 262 196 158 127 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 511 104 276 96 13

November 388 84 216 89 13

December 389 96 194 76 13

January 334 93 219 83 13

February 406 90 229 84 13

March 705 81 289 161 13

April 594 98 323 160 13

May 2,500 111 821 710 13

June 3,450 224 1,420 1,020 13

July 2,260 182 668 527 14

August 916 126 425 198 14

September 436 120 309 94 14

Annual 886 120 452 221 13
Statistical Summaries of Streamflow 215

06308400 Pumpkin Creek near Miles City, Mont.

Site Number 192

LOCATION.--Lat 46°13'42", long 105°41'24" (NAD 27), in SW1⁄4NE1⁄4SW1⁄4 sec.35, T.6 N., R.48 E., Custer County, Hydrologic Unit 10090102, on right bank 

12 ft upstream from bridge on U.S. Highway 312, 7.5 mi upstream from mouth, and 16 mi southeast of Miles City. 

DRAINAGE AREA.--697 mi2. 

PERIOD OF RECORD.--October 1972 to September 1985 (discontinued). 

GAGE.--Water-stage recorder. Altitude of gage is 2,475.86 ft (NGVD 29). 

REMARKS.--Diversions for irrigation of about 3,600 acres upstream from station. 

Magnitude and probability of annual low flow

based on 12 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.00 0.00 0.00 0.00 -- --

3 .00 .00 .00 .00 -- --

7 .00 .00 .00 .00 -- --

14 .00 .00 .00 .00 -- --

30 .00 .00 .00 .00 -- --

60 .00 .00 .00 .00 -- --

90 .00 .00 .00 .00 -- --

120 .07 .00 .00 .00 -- --

183 .32 .00 .00 .00 -- --

Magnitude and probability of seasonal low flow from

March-June based on 13 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.00 0.00 0.00 0.00 -- --

3 .00 .00 .00 .00 -- --

7 .00 .00 .00 .00 -- --

14 .01 .00 .00 .00 -- --

30 .10 .00 .00 .00 -- --

Magnitude and probability of seasonal low flow from

November-February based on 12 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.00 0.00 0.00 0.00 -- --

3 .00 .00 .00 .00 -- --

7 .00 .00 .00 .00 -- --

14 .00 .00 .00 .00 -- --

30 .00 .00 .00 .00 -- --

Duration of daily mean flows based on 13 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

0.01 0.03 0.07 0.14 0.27 0.41 0.55 0.68

40% 30% 20% 15% 10% 5% 2% 1%

0.82 0.95 2.8 7.2 17 61 160 265

Magnitude and probability of annual high flow

based on 13 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 319 977 1,620 2,640 -- --

3 236 768 1,290 2,090 -- --

7 157 496 822 1,320 -- --

15 94 306 513 829 -- --

30 58 182 293 448 -- --

60 34 108 173 261 -- --

90 26 85 141 221 -- --

Magnitude and probability of seasonal low flow from

July-October based on 13 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.00 0.00 0.00 0.00 -- --

3 .00 .00 .00 .00 -- --

7 .00 .00 .00 .00 -- --

14 .00 .00 .00 .00 -- --

30 .00 .00 .00 .00 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 9.7 0.00 1.4 2.6 14

November 2.7 .00 .33 .70 14

December .74 .00 .17 .24 13

January 29 .00 4.7 9.0 13

February 134 .00 30 48 13

March 299 .01 54 96 13

April 84 .00 17 25 13

May 205 .00 36 69 13

June 64 .00 17 21 13

July 18 .00 3.8 5.9 13

August 16 .00 2.0 4.5 13

September 60 .00 6.6 17 13

Annual 50 .22 14 15 13
216 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06308500 Tongue River at Miles City, Mont.

Site Number 193

LOCATION.--Lat 46°23'05", long 105°50'41" (NAD 27), in SE1⁄4SE1⁄4SE1⁄4 sec.4, T.7 N., R.47 E., Custer County, Hydrologic Unit 10090102, on right bank 1.5 mi 

south of Miles City and at river mile 2.3.

DRAINAGE AREA.--5,397 mi2. Area at site used prior to Oct. 4, 1995, 5,379 mi2.

PERIOD OF RECORD.--April 1938 to April 1942, April 1946 to current year (2002). Published as "near Miles City" April 1938 to April 1942. Not equivalent 

to records published as "near Miles City" May 1929 to October 1932. April 1946 to Oct. 4, 1995, at site 2.5 mi upstream. Flows at present site are equivalent 

with site operated from 1946. Monthly discharge only for some periods, published in WSP 1309.

REVISED RECORDS.--WSP 1729: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 2,360 ft (NGVD 29). April 1938 to April 1942, nonrecording gage at site 8 mi upstream at different datum. 

April 1946 to Sept. 30, 1963, at datum 1.00 ft higher. Oct. 4, 1995, gage was moved 2.5 mi downstream.

REMARKS.--Flow regulation by Tongue River Reservoir (station number 0630700; capacity, 79,100 acre-ft), and many small reservoirs in Wyoming (combined 

capacity, about 15,000 acre-ft). Diversions for irrigation of about 100,800 acres upstream from station. U.S. Army Corps of Engineers satellite telemeter at 

station.

Magnitude and probability of annual low flow

based on 58 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 33 9.1 3.7 1.5 0.12 0.00

3 38 11 4.3 1.7 .13 .00

7 46 14 5.7 2.3 .19 .00

14 58 18 8.0 3.8 1.5 .73

30 80 31 17 9.3 4.5 2.7

60 111 51 30 19 9.9 6.3

90 142 74 48 31 18 12

120 179 100 66 43 25 17

183 204 124 87 61 38 27

Magnitude and probability of seasonal low flow from

March-June based on 59 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 103 26 10 4.3 1.4 0.65

3 116 33 14 6.7 2.5 1.3

7 133 43 21 11 4.7 2.6

14 169 61 32 17 8.1 4.7

30 243 93 49 27 13 7.5

Magnitude and probability of seasonal low flow from

November-February based on 60 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 86 52 38 27 19 14

3 95 60 45 34 23 18

7 107 72 56 45 34 28

14 120 85 68 56 44 37

30 140 103 84 71 57 48

Duration of daily mean flows based on 59 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

5.1 9.0 28 68 122 160 196 235

40% 30% 20% 15% 10% 5% 2% 1%

278 365 523 686 964 1,510 2,400 3,040

Magnitude and probability of annual high flow

based on 59 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 2,870 5,010 6,450 8,200 9,430 10,600

3 2,540 4,290 5,300 6,370 7,020 7,560

7 2,160 3,530 4,230 4,880 5,240 5,510

15 1,790 2,880 3,440 3,970 4,260 4,480

30 1,420 2,310 2,780 3,250 3,510 3,720

60 1,030 1,690 2,070 2,460 2,700 2,900

90 846 1,370 1,660 1,980 2,170 2,330

Magnitude and probability of seasonal low flow from

July-October based on 60 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 48 12 4.7 1.8 0.16 0.00

3 50 13 4.9 1.9 .16 .00

7 57 15 6.0 2.7 .18 .00

14 69 19 8.3 4.2 1.8 .91

30 98 32 17 9.8 4.9 2.9

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 694 10 247 148 60

November 585 61 256 128 60

December 423 68 191 72 60

January 529 77 196 92 60

February 1,790 84 281 250 60

March 1,780 74 532 428 60

April 1,690 12 441 318 62

May 2,980 29 692 520 61

June 3,820 42 1,270 894 61

July 2,210 13 467 413 61

August 700 6.1 182 146 61

September 599 2.4 200 138 61

Annual 986 57 409 190 59
Statistical Summaries of Streamflow 217

06309000 Yellowstone River at Miles City, Mont.

Site Number 194

LOCATION.--Lat 46°25'18", long 105°51'38" (NAD 27), in NE1⁄4SW1⁄4NW1⁄4 sec.28, T.8 N., R.47 E., Custer County, Hydrologic Unit 10100001, on left bank at 

upstream side of bridge on State Highway 22 at Miles City, 0.8 mi downstream from Tongue River, and at river mile 184.2.

DRAINAGE AREA.--48,253 mi2.

PERIOD OF RECORD.--September 1922 to September 1923, August 1928 to current year (2002). Monthly discharge only for some periods, published in WSP 

1309.

REVISED RECORDS.--WSP 1729: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 2,333.3 ft (NGVD 29, levels by U.S. Army Corps of Engineers). Prior to May 6, 1929, nonrecording gages 

1.2 mi downstream at different datums. May 6, 1929, to Sept. 30, 1931, nonrecording gage, and Oct. 1, 1931, to Nov. 10, 1937, water-stage recorder 300 ft 

upstream from present site at same datum. Nov. 11, 1937, to Sept. 30, 1946, water-stage recorder 1.2 mi downstream at different datum. Oct. 1, 1946, to 

Mar. 15, 1979, water-stage recorder at site 300 ft upstream at present datum. Mar. 16, 1979, to Sept. 21, 1979, nonrecording gage at present site and datum. 

Sept. 22, 1979, recording gage established at same site and datum.

REMARKS.--Some regulation by reservoirs on tributary streams. Diversions for irrigation of about 1,100,000 acres upstream from station (does not include flood 

irrigation). U.S. Army Corps of Engineers satellite telemeter at station.

Unregulated streamflow period

Magnitude and probability of annual low flow

based on 36 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1,840 1,440 1,280 1,170 1,060 --

3 2,010 1,570 1,380 1,250 1,120 --

7 2,310 1,820 1,620 1,460 1,310 --

14 2,800 2,200 1,940 1,740 1,550 --

30 3,450 2,690 2,350 2,090 1,830 --

60 4,070 3,230 2,840 2,530 2,220 --

90 4,570 3,710 3,280 2,940 2,580 --

120 5,110 4,210 3,750 3,390 3,010 --

183 5,590 4,550 4,060 3,670 3,260 --

Magnitude and probability of seasonal low flow from

March-June based on 38 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 4,270 3,100 2,540 2,110 1,690 --

3 4,400 3,310 2,770 2,360 1,950 --

7 4,770 3,700 3,180 2,770 2,350 --

14 5,330 4,210 3,630 3,170 2,690 --

30 6,420 4,810 4,080 3,530 2,970 --

Magnitude and probability of seasonal low flow from

November-February based on 38 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1,860 1,460 1,300 1,190 1,080 --

3 2,040 1,590 1,400 1,260 1,130 --

7 2,380 1,870 1,650 1,490 1,320 --

14 2,950 2,320 2,030 1,810 1,590 --

30 3,680 2,930 2,560 2,280 1,980 --

Duration of daily mean flows based on 38 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

1,840 2,220 2,840 3,520 4,540 5,290 6,040 7,020

40% 30% 20% 15% 10% 5% 2% 1%

8,030 9,770 14,300 19,000 26,000 38,300 49,700 60,700

Magnitude and probability of annual high flow

based on 38 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 54,400 69,000 76,400 84,100 88,700 --

3 52,300 65,300 71,500 77,600 81,200 --

7 48,900 61,100 67,000 72,700 76,000 --

15 44,500 55,400 60,800 66,000 69,000 --

30 39,000 49,100 54,200 59,200 62,100 --

60 30,600 38,900 43,400 48,100 51,100 --

90 24,800 31,400 34,800 38,300 40,400 --

Magnitude and probability of seasonal low flow from

July-October based on 36 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 4,230 3,010 2,460 2,060 1,670 --

3 4,290 3,050 2,490 2,080 1,680 --

7 4,450 3,180 2,610 2,200 1,790 --

14 4,710 3,360 2,760 2,320 1,880 --

30 5,140 3,690 3,040 2,570 2,100 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 12,900 4,120 7,090 1,820 38

November 9,160 3,980 6,500 1,320 38

December 7,070 2,920 4,920 1,170 38

January 7,180 2,030 4,390 1,150 38

February 9,610 2,340 5,140 1,760 38

March 18,600 4,100 7,940 2,820 38

April 15,200 2,730 7,800 2,580 38

May 27,000 7,330 16,800 4,820 38

June 58,600 10,000 36,800 10,400 38

July 42,300 3,990 19,900 9,750 38

August 16,000 2,620 7,550 3,320 38

September 13,700 2,960 6,670 2,320 40

Annual 16,700 6,140 11,000 2,530 38
218 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06309000 Yellowstone River at Miles City, Mont.—Continued

Site Number 194

Regulated streamflow period

Magnitude and probability of annual low flow

based on 36 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 2,990 2,290 2,010 1,810 1,610 --

3 3,220 2,480 2,170 1,950 1,730 --

7 3,680 2,950 2,640 2,430 2,210 --

14 4,480 3,630 3,230 2,920 2,600 --

30 5,390 4,400 3,870 3,440 2,980 --

60 5,920 4,870 4,320 3,880 3,390 --

90 6,410 5,280 4,690 4,220 3,700 --

120 6,800 5,600 4,960 4,450 3,890 --

183 7,280 5,870 5,140 4,560 3,940 --

Magnitude and probability of seasonal low flow from

March-June based on 37 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 5,920 4,160 3,330 2,720 2,110 --

3 6,130 4,350 3,490 2,850 2,220 --

7 6,310 4,630 3,840 3,260 2,670 --

14 6,840 5,230 4,500 3,970 3,420 --

30 7,390 5,610 4,810 4,220 3,620 --

Magnitude and probability of seasonal low flow from

November-February based on 36 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 3,110 2,380 2,080 1,870 1,650 --

3 3,360 2,580 2,250 2,010 1,780 --

7 3,930 3,110 2,760 2,500 2,240 --

14 4,650 3,810 3,420 3,130 2,830 --

30 5,490 4,710 4,340 4,050 3,740 --

Duration of daily mean flows based on 37 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

2,920 3,310 4,130 4,770 5,840 6,710 7,520 8,330

40% 30% 20% 15% 10% 5% 2% 1%

9,620 11,300 15,000 18,300 25,300 34,800 47,000 55,200

Magnitude and probability of annual high flow

based on 37 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 45,200 60,000 69,300 80,300 88,200 --

3 43,500 58,400 67,800 79,100 87,200 --

7 40,200 54,500 63,600 74,600 82,500 --

15 37,000 50,400 58,700 68,900 76,100 --

30 33,300 45,200 52,600 61,300 67,500 --

60 27,900 37,700 43,500 50,200 54,900 --

90 23,300 31,000 35,600 40,800 44,300 --

Magnitude and probability of seasonal low flow from

July-October based on 36 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 5,970 4,450 3,730 3,170 2,610 --

3 6,100 4,520 3,770 3,210 2,630 --

7 6,240 4,620 3,850 3,270 2,670 --

14 6,480 4,750 3,940 3,330 2,750 --

30 6,860 5,010 4,150 3,500 3,000 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 13,000 4,220 8,420 2,170 37

November 10,800 4,730 7,790 1,800 37

December 9,340 4,070 6,610 1,190 37

January 8,900 3,780 6,260 1,250 37

February 16,200 3,900 7,270 2,390 37

March 17,700 3,030 8,630 3,220 37

April 14,700 4,250 8,730 2,640 37

May 29,100 10,000 17,800 5,070 37

June 61,900 10,000 32,700 12,300 37

July 46,300 6,060 20,600 10,400 37

August 16,500 3,030 8,830 3,530 37

September 13,100 3,660 7,800 2,500 37

Annual 17,500 6,180 11,800 2,890 37
Statistical Summaries of Streamflow 219

06324500 Powder River at Moorhead, Mont.

Site Number 195

LOCATION.--Lat 45°03'25", long 105°52'39" (NAD 27), in NE1⁄4NE1⁄4NW1⁄4 sec.18, T.9 S., R.48 E., Powder River County, Hydrologic Unit 10090207, on left 

bank 25 ft downstream from bridge on Powder River, 7.3 mi upstream from Buffalo Creek, and at river mile 183.7.

DRAINAGE AREA.--8,086 mi2; Sept. 13, 1956 to Aug. 27, 2001 published as 8,088 mi2.

PERIOD OF RECORD.--May 1929 to September 1972, October 1974 to current year (2002). Monthly discharge only for some periods, published in WSP 1309.

REVISED RECORDS.--WSP 1309: 1932(M). WSP 1729: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 3,334.63 ft (NGVD 29, levels by U.S. Army Corps of Engineers). Prior to Aug. 28, 1931, nonrecording gage 

at site 0.3 mi upstream at different datum. Aug. 28, 1931, to Mar. 21, 1956, water-stage recorder at site 1.2 mi upstream at different datum. Mar. 22 to July 24, 

1956, nonrecording gage at site 0.3 mi downstream at different datum. July 25 to Sept. 12, 1956, nonrecording gage at present site and datum. Sept. 13, 1956, 

to Aug. 27, 2001, water-stage recorder during period of gage operation 1.1 mi downstream at different datum.

REMARKS.--Some regulation by three reservoirs in Wyoming (combined usable capacity, 36,800 acre-ft). Diversions for irrigation of about 66,300 acres 

upstream from station. U.S. Geological Survey satellite telemeter at station.

Magnitude and probability of annual low flow

based on 70 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 16 2.5 0.00 0.00 0.00 0.00

3 19 3.1 .00 .00 .00 .00

7 22 3.8 .90 .05 .00 .00

14 28 7.1 2.6 .37 .00 .00

30 43 13 5.9 2.8 1.1 .57

60 67 28 17 11 5.9 3.9

90 99 51 34 23 14 10

120 128 75 54 40 28 22

183 148 98 79 66 53 46

Magnitude and probability of seasonal low flow from

March-June based on 71 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 123 42 21 11 4.6 2.5

3 133 47 24 13 5.6 3.1

7 160 62 33 18 8.7 5.0

14 230 99 54 30 14 8.1

30 329 175 115 77 47 33

Magnitude and probability of seasonal low flow from

November-February based on 71 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 66 34 21 13 7.0 4.4

3 76 44 29 20 12 8.3

7 94 56 38 26 16 11

14 108 64 44 31 19 13

30 125 81 60 45 31 23

Duration of daily mean flows based on 71 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

3.5 7.3 20 46 93 132 174 224

40% 30% 20% 15% 10% 5% 2% 1%

284 372 557 734 1,080 1,840 2,920 3,930

Magnitude and probability of annual high flow

based on 71 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 4,190 7,540 10,300 14,300 17,700 21,500

3 3,300 5,800 7,800 10,700 13,100 15,700

7 2,530 4,330 5,680 7,540 9,020 10,600

15 1,960 3,320 4,280 5,540 6,490 7,450

30 1,530 2,600 3,350 4,320 5,050 5,770

60 1,170 1,950 2,500 3,220 3,750 4,280

90 976 1,560 1,950 2,440 2,800 3,140

Magnitude and probability of seasonal low flow from

July-October based on 71 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 18 2.6 0.00 0.00 0.00 0.00

3 20 3.7 .00 .00 .00 .00

7 23 4.9 1.2 .06 .00 .00

14 30 8.3 3.3 .70 .00 .00

30 46 15 6.3 3.4 1.1 .75

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 897 16 226 159 71

November 660 80 225 96 71

December 326 56 159 56 71

January 445 27 154 64 71

February 1,200 21 288 206 71

March 2,290 185 612 385 71

April 1,310 117 508 237 71

May 5,550 83 1,090 881 72

June 4,130 40 1,400 1,070 72

July 2,500 34 471 431 72

August 1,220 .60 176 194 72

September 686 1.3 147 143 72

Annual 1,090 110 448 193 71
220 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06325500 Little Powder River near Broadus, Mont.

Site Number 196

LOCATION.--Lat 45°23'25", long 105°18'15" (NAD 27), in NW1⁄4NE1⁄4 sec.21, T.5 S., R.52 E., Powder River County, on left bank 1.5 mi downstream from East 

Fork, 5.5 mi southeast of Broadus, and 8 mi upstream from mouth.

DRAINAGE AREA.--1,974 mi2 . 

PERIOD OF RECORD.--20 years. May 1947 to September 1953, water year 1956, March 1957 to September 1972, discontinued. Monthly discharge only for 

May 1947, published in WSP 1309.

REVISED RECORDS (WATER YEARS).--WSP 1116: 1947. WSP 1729: Drainage area.

GAGE.--Water-stage recorder and crest-stage gage. Altitude of gage is 3,020 ft (NGVD 29, by barometer). Prior to Dec. 10, 1962, water-stage recorder at site 

0.8 mi upstream at different datum. 

REMARKS.--Minor diversions upstream from station.

Magnitude and probability of annual low flow

based on 18 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.24 0.00 0.00 0.00 -- --

3 .25 .00 .00 .00 -- --

7 .51 .03 .00 .00 -- --

14 .83 .09 .00 .00 -- --

30 1.3 .46 .22 .00 -- --

60 2.1 1.0 .63 .42 -- --

90 2.7 1.5 1.1 .87 -- --

120 3.0 1.9 1.5 1.2 -- --

183 3.7 2.3 1.8 1.6 -- --

Magnitude and probability of seasonal low flow from

March-June based on 20 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 4.6 2.4 1.8 0.00 -- --

3 5.2 2.6 1.8 .00 -- --

7 5.9 2.8 1.8 .00 -- --

14 8.2 3.3 2.0 1.3 -- --

30 12 5.1 3.3 2.2 -- --

Magnitude and probability of seasonal low flow from

November-February based on 21 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1.2 0.00 0.00 0.00 -- --

3 1.3 .02 .00 .00 -- --

7 1.4 .42 .06 .00 -- --

14 1.7 .62 .12 .00 -- --

30 2.2 1.0 .61 .38 -- --

Duration of daily mean flows based on 20 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

0.16 0.33 0.82 1.5 2.4 3.2 4.2 5.6

40% 30% 20% 15% 10% 5% 2% 1%

8.4 16 33 47 69 150 417 708

Magnitude and probability of annual high flow

based on 20 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 943 1,530 1,920 2,390 -- --

3 737 1,340 1,740 2,240 -- --

7 520 976 1,270 1,610 -- --

15 349 642 807 970 -- --

30 230 420 521 614 -- --

60 147 269 332 391 -- --

90 108 196 241 284 -- --

Magnitude and probability of seasonal low flow from

July-October based on 20 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.83 0.13 0.00 0.00 -- --

3 .87 .16 .00 .00 -- --

7 1.1 .24 .06 .00 -- --

14 1.4 .44 .16 .00 -- --

30 1.9 .78 .40 .00 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 70 1.5 6.6 15 21

November 16 1.8 4.4 3.1 21

December 8.7 .87 3.8 2.1 21

January 8.2 .35 3.7 2.0 21

February 340 3.2 48 83 21

March 558 5.3 160 190 21

April 238 2.3 63 74 21

May 190 3.1 51 50 22

June 305 2.0 81 72 22

July 110 1.5 28 27 22

August 69 .00 14 20 22

September 54 .39 7.3 11 22

Annual 110 3.0 40 27 20
Statistical Summaries of Streamflow 221

06326300 Mizpah Creek near Mizpah, Mont.

Site Number 197

LOCATION.--Lat 46°15'39", long 105°17'34" (NAD 27), in NW1⁄4NE1⁄4SW1⁄4 sec.24, T.6 N., R.51 E., Custer County, Hydrologic Unit 10090210, on left bank 

20 ft downstream from county bridge, 1.0 mi upstream from mouth, and 1.6 mi northwest of Mizpah.

DRAINAGE AREA.--797 mi2. 

PERIOD OF RECORD.--October 1974 to September 1986 (discontinued). 

GAGE.--Water-stage recorder and crest-stage gage. Altitude of gage is 2,490 ft (NGVD 29, from topographic map). 

Magnitude and probability of annual low flow

based on 11 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.00 0.00 0.00 0.00 -- --

3 .00 .00 .00 .00 -- --

7 .00 .00 .00 .00 -- --

14 .00 .00 .00 .00 -- --

30 .00 .00 .00 .00 -- --

60 .01 .00 .00 .00 -- --

90 .03 .01 .00 .00 -- --

120 .08 .01 .00 .00 -- --

183 .31 .04 .01 .00 -- --

Magnitude and probability of seasonal low flow from

March-June based on 12 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.00 0.00 0.00 0.00 -- --

3 .02 .00 .00 .00 -- --

7 .06 .00 .00 .00 -- --

14 .12 .02 .01 .00 -- --

30 .31 .05 .02 .01 -- --

Magnitude and probability of seasonal low flow from

November-February based on 11 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.00 0.00 0.00 0.00 -- --

3 .00 .00 .00 .00 -- --

7 .00 .00 .00 .00 -- --

14 .00 .00 .00 .00 -- --

30 .00 .00 .00 .00 -- --

Duration of daily mean flows based on 12 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

0.01 0.03 0.07 0.14 0.29 0.43 0.58 0.72

40% 30% 20% 15% 10% 5% 2% 1%

0.86 1.1 4.9 12 23 69 175 350

Magnitude and probability of annual high flow

based on 12 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 346 955 1,600 -- -- --

3 236 741 1,330 -- -- --

7 164 486 852 -- -- --

15 92 283 508 -- -- --

30 58 169 292 -- -- --

60 36 102 171 -- -- --

90 27 80 137 -- -- --

Magnitude and probability of seasonal low flow from

July-October based on 11 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.01 0.00 0.00 0.00 -- --

3 .01 .00 .00 .00 -- --

7 .01 .00 .00 .00 -- --

14 .01 .00 .00 .00 -- --

30 .01 .00 .00 .00 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 25 0.00 4.8 8.8 12

November 1.6 .00 .33 .46 12

December 2.1 .01 .26 .58 12

January 18 .00 1.9 5.1 12

February 110 .00 29 40 12

March 319 .13 60 96 12

April 126 .07 17 36 12

May 196 .06 39 60 12

June 71 .10 19 22 12

July 28 .00 5.9 8.0 12

August 14 .00 2.1 3.8 12

September 166 .00 16 47 12

Annual 46 1.1 16 16 12
222 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06326500 Powder River near Locate, Mont.

Site Number 198

LOCATION.--Lat 46°25'48", long 105°18'34" (NAD 27), in SW1⁄4SW1⁄4SE1⁄4 sec.23, T.8 N., R.51 E., Custer County, Hydrologic Unit 10090209, on left bank at 

downstream side of bridge on U.S. Highway 12, 0.1 mi west of Locate, and 25 mi east of Miles City, and at river mile 29.4.

DRAINAGE AREA.--13,068 mi2. 

PERIOD OF RECORD.--March 1938 to current year (2002).

REVISED RECORDS.--WSP 926: 1939. WSP 1309: 1938-39 (M). WSP 1729: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 2,384.79 ft (NGVD 29, levels by U.S. Army Corps of Engineers). Prior to July 11, 1947, nonrecording gage 

at bridge 1.5 mi upstream, and July 11, 1947, to Sept. 30, 1965, water-stage recorder at site near upstream bridge at different datum. Oct. 1, 1965, to Oct. 4, 

1966, nonrecording gage, and Oct. 5, 1966, to Mar. 21, 1978, water-stage recorder at present site and datum. Mar. 22, 1978, to Apr. 23, 1981, water-stage 

recorder 1.5 mi upstream at different datum, Apr. 24 to Aug. 20, 1981, water-stage recorder at present site and datum, and Aug. 21, 1981, to Sept. 30, 1981, 

water-stage recorder 1.5 mi upstream at different datum. Oct. 1, 1981, to Apr. 5, 1995, water-stage recorder at site 1.5 mi downstream at different datum. 

Apr. 7, 1995, to present (2002), water-stage recorders located on each bank and used depending on control conditions.

REMARKS.--Some regulation by three reservoirs in Wyoming (combined usable capacity, 36,800 acre-ft). Diversions for irrigation of about 101,800 acres 

upstream from station. U.S. Army Corps of Engineers satellite telemeter at station.

Magnitude and probability of annual low flow

based on 63 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 15 3.7 1.2 0.00 0.00 0.00

3 17 4.6 1.7 .00 .00 .00

7 21 5.3 1.9 .12 .00 .00

14 38 6.6 2.3 .22 .00 .00

30 47 9.1 2.6 .74 .14 .04

60 74 24 11 5.0 1.9 .90

90 111 47 25 13 5.9 3.2

120 143 67 39 22 11 6.5

183 163 85 55 37 22 16

Magnitude and probability of seasonal low flow from

March-June based on 64 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 147 55 30 17 8.3 5.0

3 158 63 35 21 11 7.0

7 188 81 48 30 17 11

14 267 122 75 47 27 18

30 427 203 125 80 45 30

Magnitude and probability of seasonal low flow from

November-February based on 64 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 46 22 13 7.6 2.4 0.00

3 55 27 17 10 3.2 .00

7 64 35 23 15 5.9 .00

14 80 45 30 20 8.0 .00

30 111 62 44 31 11 .00

Duration of daily mean flows based on 64 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

2.6 5.8 16 41 85 124 174 241

40% 30% 20% 15% 10% 5% 2% 1%

337 485 755 1,000 1,380 2,150 3,680 5,340

Magnitude and probability of annual high flow

based on 64 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 5,530 11,000 15,700 22,900 29,100 36,000

3 4,520 9,090 13,100 19,200 24,600 30,700

7 3,440 6,700 9,430 13,500 17,000 20,900

15 2,590 4,720 6,350 8,590 10,400 12,200

30 2,010 3,510 4,560 5,930 6,950 7,960

60 1,520 2,570 3,280 4,160 4,780 5,380

90 1,260 2,080 2,610 3,250 3,700 4,130

Magnitude and probability of seasonal low flow from

July-October based on 64 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 18 4.1 1.5 0.17 0.00 0.00

3 20 5.0 2.0 .29 .00 .00

7 24 5.8 2.3 .76 .00 .00

14 43 7.4 2.4 .84 .08 .02

30 49 10 3.9 1.5 .49 .21

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 921 1.8 252 225 64

November 790 12 220 127 64

December 417 12 150 78 64

January 476 9.4 143 84 64

February 3,850 6.1 434 601 64

March 4,630 80 1,240 1,090 64

April 3,060 109 739 486 65

May 5,970 114 1,150 913 65

June 8,040 48 1,610 1,390 65

July 2,020 10 581 500 65

August 1,100 1.4 215 208 65

September 898 .24 174 198 65

Annual 1,620 81 576 300 64
Statistical Summaries of Streamflow 223

06326600 O’Fallon Creek near Ismay, Mont.

Site Number 199

LOCATION.--Lat 46°25'17", long 104°45'40" (NAD 27), in NE1⁄4SE1⁄4 sec.30, T.8 N., R.56 E., Fallon County, Hydrologic Unit 10100005, on left bank, about 

350 ft upstream from U.S. Highway 12, 1 mi east of road to Ismay, 6.5 mi southeast of Ismay, 11.5 mi west of Plevna, and at river mile 58.3. 

DRAINAGE AREA.--669 mi2. 

PERIOD OF RECORD.--October 1977 to September 1992 (discontinued). Crest-stage partial-record data collected July 1962 to September 1977. 

GAGE.--Water-stage recorder. Altitude of gage is 2,590 ft (NGVD 29, from topographic map). 

Magnitude and probability of annual low flow

based on 14 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.00 0.00 0.00 0.00 -- --

3 .00 .00 .00 .00 -- --

7 .00 .00 .00 .00 -- --

14 .00 .00 .00 .00 -- --

30 .00 .00 .00 .00 -- --

60 .03 .00 .00 .00 -- --

90 .08 .00 .00 .00 -- --

120 .08 .00 .00 .00 -- --

183 .23 .00 .00 .00 -- --

Magnitude and probability of seasonal low flow from

March-June based on 15 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.00 0.00 0.00 0.00 -- --

3 .00 .00 .00 .00 -- --

7 .08 .00 .00 .00 -- --

14 .24 .00 .00 .00 -- --

30 .91 .00 .00 .00 -- --

Magnitude and probability of seasonal low flow from

November-February based on 15 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.00 0.00 0.00 0.00 -- --

3 .00 .00 .00 .00 -- --

7 .01 .00 .00 .00 -- --

14 .03 .00 .00 .00 -- --

30 .10 .00 .00 .00 -- --

Duration of daily mean flows based on 15 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

0.02 0.03 0.08 0.17 0.34 0.51 0.68 0.84

40% 30% 20% 15% 10% 5% 2% 1%

1.0 2.2 5.7 9.2 17 43 125 248

Magnitude and probability of annual high flow

based on 15 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 310 876 1,510 2,690 -- --

3 224 677 1,190 2,160 -- --

7 146 469 867 1,670 -- --

15 86 270 506 1,010 -- --

30 53 163 303 600 -- --

60 31 94 168 316 -- --

90 23 68 123 235 -- --

Magnitude and probability of seasonal low flow from

July-October based on 14 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.00 0.00 0.00 0.00 -- --

3 .00 .00 .00 .00 -- --

7 .00 .00 .00 .00 -- --

14 .00 .00 .00 .00 -- --

30 .00 .00 .00 .00 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 13 0.00 2.0 4.3 15

November 5.8 .00 .83 1.5 15

December 1.7 .00 .60 .62 15

January 14 .00 1.6 3.6 15

February 172 .00 37 63 15

March 568 .00 62 144 15

April 120 .14 19 31 15

May 81 .03 20 29 15

June 160 .00 20 41 15

July 21 .00 5.4 7.0 15

August 58 .00 5.1 15 15

September 5.6 .00 .49 1.5 15

Annual 64 1.2 14 18 15
224 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06327500 Yellowstone River at Glendive, Mont.

Site Number 200

LOCATION.--Lat 47°06'00", long 104°43'00" (NAD 27), in N1⁄2 sec.35, T.16 N, R.55 E., Dawson County, at highway bridge at Glendive.

DRAINAGE AREA.--66,788 mi2.

PERIOD OF RECORD.--16 years (1897-1910, 1931-34).

GAGE.--Chain gage. Altitude of gage is 2,040 ft (NGVD 29, from topographic map). 

REMARKS.--Diversions for irrigation of about 1,200,000 acres upstream from station. Some regulation on tributary streams. Records for this station are 

considered equivalent to records for Yellowstone River at Sidney (station number 06329500) except during periods of operation of Lower Yellowstone Canal 

at Lower Yellowstone Dam at Intake.

Magnitude and probability of annual low flow

based on 10 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 3,120 2,040 1,530 1,160 -- --

3 3,170 2,100 1,590 1,220 -- --

7 3,300 2,320 1,830 1,450 -- --

14 3,680 2,810 2,330 1,940 -- --

30 4,180 3,500 3,110 2,780 -- --

60 4,470 3,930 3,590 3,300 -- --

90 4,680 4,170 3,850 3,570 -- --

120 4,930 4,480 4,240 4,040 -- --

183 5,860 5,290 5,020 4,820 -- --

Magnitude and probability of seasonal low flow from

March-June based on 13 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 5,090 3,430 2,710 2,200 -- --

3 5,130 4,030 3,650 3,400 -- --

7 5,330 4,380 4,070 3,880 -- --

14 5,580 4,640 4,330 4,130 -- --

30 6,610 5,340 4,820 4,460 -- --

Magnitude and probability of seasonal low flow from

November-February based on 12 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 3,190 2,110 1,600 1,240 -- --

3 3,240 2,170 1,670 1,300 -- --

7 3,340 2,340 1,860 1,510 -- --

14 3,700 2,840 2,360 1,970 -- --

30 4,210 3,540 3,160 2,840 -- --

Duration of daily mean flows based on 13 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

2,060 2,500 3,360 4,240 4,850 5,410 5,970 7,120

40% 30% 20% 15% 10% 5% 2% 1%

8,450 11,500 17,900 24,400 36,400 49,800 65,800 71,900

Magnitude and probability of annual high flow

based on 13 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 65,500 86,600 96,100 105,000 -- --

3 62,800 81,900 90,100 97,200 -- --

7 60,600 76,500 82,300 86,500 -- --

15 57,000 69,500 73,100 75,200 -- --

30 53,400 65,000 68,100 69,900 -- --

60 42,600 53,600 57,800 61,000 -- --

90 34,700 43,300 46,500 48,900 -- --

Magnitude and probability of seasonal low flow from

July-October based on 12 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 5,780 4,860 4,440 4,120 -- --

3 5,840 4,960 4,570 4,270 -- --

7 5,970 5,130 4,760 4,470 -- --

14 6,130 5,350 5,010 4,760 -- --

30 6,470 5,660 5,300 5,040 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 9,500 4,880 6,640 1,310 14

November 7,390 4,200 5,560 812 14

December 5,700 2,920 4,530 805 14

January 5,700 3,270 4,570 686 13

February 5,940 3,360 4,690 744 13

March 18,800 5,660 9,300 3,710 13

April 13,900 4,370 8,550 2,560 14

May 44,700 9,660 21,900 9,260 14

June 74,200 10,000 46,100 14,000 14

July 64,000 4,050 27,700 16,100 14

August 24,100 2,780 11,600 5,510 14

September 12,100 2,860 7,840 2,270 14

Annual 17,700 6,060 13,300 3,120 13
Statistical Summaries of Streamflow 225

06329200 Burns Creek near Savage, Mont.

Site Number 201

LOCATION.--Lat 47°22'20", long 104°25'46" (NAD 27), in NE1⁄4SE1⁄4SE1⁄4 sec.27, T.19 N., R.57 E., Richland County, Hydrologic Unit 10100004, on right bank 

1,000 ft upstream from bridge on State Highway 16, 7 mi southwest of Savage, and at river mile 2.1. 

DRAINAGE AREA.--233 mi2. 

PERIOD OF RECORD.--October 1957 to September 1967, September 1975 to September 1984, October 1985 to September 1986 (discontinued). 

GAGE.--Water-stage recorder. Altitude of gage is 2,000 ft (NGVD 29, from topographic map). 

REMARKS.--Minor diversions for irrigation upstream. 

Magnitude and probability of annual low flow

based on 12 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.00 0.00 0.00 0.00 -- --

3 .00 .00 .00 .00 -- --

7 .00 .00 .00 .00 -- --

14 .00 .00 .00 .00 -- --

30 .00 .00 .00 .00 -- --

60 .08 .00 .00 .00 -- --

90 .24 .07 .00 .00 -- --

120 .39 .19 .11 .00 -- --

183 .51 .26 .17 .00 -- --

Magnitude and probability of seasonal low flow from

March-June based on 19 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.28 0.00 0.00 0.00 -- --

3 .30 .00 .00 .00 -- --

7 .38 .00 .00 .00 -- --

14 .85 .14 .00 .00 -- --

30 1.6 .64 .35 .00 -- --

Magnitude and probability of seasonal low flow from

November-February based on 15 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.05 0.00 0.00 0.00 -- --

3 .06 .00 .00 .00 -- --

7 .08 .00 .00 .00 -- --

14 .11 .00 .00 .00 -- --

30 .29 .00 .00 .00 -- --

Duration of daily mean flows based on 20 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

0.02 0.04 0.10 0.19 0.39 0.58 0.78 0.97

40% 30% 20% 15% 10% 5% 2% 1%

1.4 2.0 3.5 5.2 8.8 21 56 106

Magnitude and probability of annual high flow

based on 20 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 153 605 1,190 2,370 -- --

3 100 399 797 1,630 -- --

7 62 231 442 860 -- --

15 39 134 247 458 -- --

30 25 84 155 290 -- --

60 16 50 89 160 -- --

90 12 36 63 109 -- --

Magnitude and probability of seasonal low flow from

July-October based on 13 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.00 0.00 0.00 0.00 -- --

3 .00 .00 .00 .00 -- --

7 .00 .00 .00 .00 -- --

14 .00 .00 .00 .00 -- --

30 .01 .00 .00 .00 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 2.7 0.19 1.2 0.80 19

November 2.1 .45 1.0 .47 19

December 2.1 .23 .78 .44 19

January 5.0 .20 .89 1.1 18

February 103 .10 16 27 17

March 183 1.2 42 52 19

April 118 1.8 12 26 20

May 15 .68 4.4 3.8 20

June 15 .28 6.1 4.8 20

July 25 .18 4.6 6.7 19

August 1.6 .10 .72 .56 17

September 9.8 .11 1.6 2.7 14

Annual 21 .83 7.9 6.7 20
226 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06329500 Yellowstone River near Sidney, Mont.

Site Number 202

LOCATION.--Lat 47°40'42", long 104°09'22" (NAD 27), in SW1⁄4NE1⁄4SW1⁄4 sec.9, T.22 N., R.59 E., Richland County, Hydrologic Unit 10100004, on left bank 

at Montana-Dakota Utilities Company powerplant, 0.2 mi downstream from bridge on State Highway 23, 2.5 mi south of Sidney, 3.0 mi downstream from Fox 

Creek, and at river mile 29.2.

DRAINAGE AREA.--69,083 mi2. Area at site 4.5 mi upstream, 68,812 mi2.

PERIOD OF RECORD.--October 1910 to September 1931 published as "at Intake", October 1933 to current year (2002). If monthly figures of diversions to Lower 

Yellowstone Canal at Intake are added to records at this site, records equivalent to those published as "Yellowstone River at Glendive" (1898-1910, 1931-34) 

can be obtained. Monthly discharge only for some periods, published in WSP 1309. Monthly figures of diversions into Lower Yellowstone Canal prior to 

1951 published in WSP 1309, 1951-60 published in WSP 1729, 1961-65 published in WSP 1916, 1966-70 published in WSP 2116, and 1971 to current year 

(2002) are published in annual reports.

GAGE.--Water-stage recorder. Altitude of gage is 1,881.3 ft (NGVD 29, levels by U.S. Army Corps of Engineers). Jan. 1, 1911, to Sept. 30, 1931, nonrecording 

gage at site 32 mi upstream at different datum. Apr. 9, 1934, water-stage recorder at two sites within 500 ft of highway bridge 0.2 mi upstream and May 17, 

1945, to Apr. 3, 1952, nonrecording gage on same bridge at datum 1.36 ft higher. Apr. 4, 1952, to Nov. 19, 1967, water-stage recorder at site 4.5 mi upstream 

at different datum.

REMARKS.--Flow regulated to some extent by Bighorn Lake, usable capacity, 1,312,000 acre-ft, on the Bighorn River and on other tributary streams in Wyoming 

and Montana. Diversion for irrigation of about 1,250,000 acres upstream from station. Lower Yellowstone Project Main Canal diverts from left bank in NW1⁄4 

sec.36, T.18 N., R.56 E., at Lower Yellowstone diversion dam at Intake about 36.6 mi upstream for irrigation of about 52,000 acres of which about one-third 

lie upstream from station. U.S. Army Corps of Engineers satellite telemeter at station.

Unregulated streamflow period

Magnitude and probability of annual low flow

based on 51 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 2,020 1,290 1,020 842 677 585

3 2,120 1,400 1,140 956 789 696

7 2,440 1,660 1,360 1,160 963 853

14 3,000 2,100 1,730 1,470 1,210 1,060

30 3,910 2,830 2,330 1,970 1,600 1,380

60 4,430 3,410 2,950 2,620 2,270 2,070

90 4,940 3,940 3,490 3,160 2,830 2,620

120 5,450 4,440 4,000 3,670 3,330 3,120

183 6,020 4,790 4,260 3,880 3,490 3,250

Magnitude and probability of seasonal low flow from

March-June based on 53 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 5,200 3,480 2,540 1,850 1,210 880

3 5,290 3,690 2,830 2,180 1,550 1,200

7 5,660 4,100 3,270 2,620 1,970 1,600

14 6,420 4,710 3,830 3,160 2,470 2,070

30 7,980 5,770 4,750 3,990 3,240 2,790

Magnitude and probability of seasonal low flow from

November-February based on 52 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 2,110 1,330 1,050 871 707 617

3 2,230 1,450 1,160 979 809 714

7 2,560 1,710 1,390 1,180 981 869

14 3,190 2,280 1,910 1,650 1,400 1,250

30 4,030 3,170 2,800 2,540 2,270 2,110

Duration of daily mean flows based on 53 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

1,650 2,050 2,910 3,720 4,850 5,770 6,760 7,780

40% 30% 20% 15% 10% 5% 2% 1%

8,960 11,600 17,100 22,600 30,500 45,100 63,100 71,000

Magnitude and probability of annual high flow

based on 53 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 68,600 94,300 109,000 124,000 134,000 142,000

3 64,800 87,700 100,000 113,000 121,000 128,000

7 58,500 78,200 88,600 99,400 106,000 112,000

15 51,700 69,400 79,000 89,200 95,600 101,000

30 45,100 60,000 67,800 75,800 80,700 84,900

60 35,700 47,000 52,800 58,600 62,100 65,000

90 28,900 37,900 42,500 47,200 50,000 52,400

Magnitude and probability of seasonal low flow from

July-October based on 52 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 4,310 2,600 1,890 1,410 978 752

3 4,390 2,670 1,950 1,470 1,030 797

7 4,530 2,820 2,100 1,620 1,170 928

14 4,800 3,000 2,260 1,740 1,270 1,010

30 5,400 3,410 2,590 2,020 1,500 1,210

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 29,100 3,730 7,950 3,690 54

November 12,200 3,700 6,910 1,630 54

December 8,710 3,020 5,380 1,420 54

January 13,100 2,090 5,060 1,860 53

February 15,400 2,700 6,110 2,870 53

March 21,200 5,190 10,900 4,420 53

April 39,200 2,820 10,900 6,120 53

May 38,100 5,410 18,600 6,490 53

June 77,300 10,000 42,200 14,400 53

July 55,000 3,310 24,400 12,600 53

August 20,500 1,600 9,080 4,660 53

September 16,000 2,390 6,960 3,000 53

Annual 21,200 5,810 12,900 3,630 53
Statistical Summaries of Streamflow 227

06329500 Yellowstone River near Sidney, Mont.—Continued

Site Number 202

Regulated streamflow period

Magnitude and probability of annual low flow

based on 36 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 3,280 2,210 1,720 1,380 1,050 --

3 3,430 2,350 1,870 1,520 1,180 --

7 3,790 2,730 2,260 1,910 1,560 --

14 4,660 3,380 2,740 2,260 1,770 --

30 5,630 4,090 3,260 2,610 1,960 --

60 6,360 4,810 3,940 3,230 2,500 --

90 6,810 5,380 4,580 3,920 3,220 --

120 7,220 5,780 4,990 4,350 3,660 --

183 7,590 6,020 5,210 4,570 3,880 --

Magnitude and probability of seasonal low flow from

March-June based on 37 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 6,370 4,570 3,750 3,140 2,540 --

3 6,610 4,810 3,980 3,350 2,730 --

7 7,010 5,230 4,380 3,750 3,100 --

14 7,530 5,670 4,810 4,170 3,520 --

30 8,360 6,210 5,250 4,530 3,810 --

Magnitude and probability of seasonal low flow from

November-February based on 36 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 3,440 2,310 1,800 1,430 1,070 --

3 3,620 2,470 1,950 1,570 1,210 --

7 4,010 2,900 2,390 2,020 1,640 --

14 4,900 3,820 3,290 2,870 2,430 --

30 5,860 4,770 4,200 3,730 3,230 --

Duration of daily mean flows based on 37 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

2,460 3,140 3,990 4,770 5,960 6,890 7,790 8,680

40% 30% 20% 15% 10% 5% 2% 1%

10,200 11,800 15,800 20,000 27,000 38,300 49,700 61,500

Magnitude and probability of annual high flow

based on 37 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 50,400 67,600 78,100 90,600 99,300 --

3 48,400 64,700 74,600 86,200 94,300 --

7 44,300 59,600 69,100 80,300 88,200 --

15 39,900 54,300 63,300 74,000 81,600 --

30 35,300 48,500 56,800 66,800 73,800 --

60 29,100 39,800 46,400 54,200 59,600 --

90 24,200 32,800 37,900 43,900 48,100 --

Magnitude and probability of seasonal low flow from

July-October based on 36 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 5,420 3,600 2,780 2,200 1,640 --

3 5,500 3,650 2,820 2,230 1,670 --

7 5,650 3,780 2,940 2,330 1,760 --

14 5,940 3,960 3,060 2,420 1,810 --

30 6,520 4,340 3,340 2,630 1,990 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 15,400 4,090 8,820 2,490 37

November 11,400 3,970 7,990 2,040 37

December 9,590 3,970 6,800 1,280 37

January 9,670 3,820 6,700 1,380 37

February 17,800 4,180 7,950 2,690 37

March 26,000 3,240 11,000 5,190 37

April 15,400 4,230 9,450 2,980 37

May 34,600 9,820 17,800 5,870 37

June 65,300 10,000 34,000 13,500 37

July 49,700 4,810 21,100 11,600 37

August 18,200 1,600 8,220 3,960 37

September 12,900 2,990 7,430 2,850 37

Annual 19,200 6,390 12,300 3,330 37
228 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06334000 Little Missouri River near Alzada, Mont.

Site Number 203

LOCATION.--Lat 45°05', long 104°24' (NAD 27), NE1⁄4SW1⁄4 sec.6, T.9 S., R.60 E., Carter County, on right bank 1.9 mi downstream from Thompson Creek and 

4 mi north of Alzada.

DRAINAGE AREA.--904 mi2 . 

PERIOD OF RECORD.--June 1911 to December 1914 (no winter records in most years), March 1915 to September 1925, August 1928 to September 1932, March 

1935 to September 1969. Records collected at station of same name in 1904 at site 8 mi upstream are not equivalent (published as "at Alzada" in WSP 1309). 

Monthly discharge only for some periods, published in WSP 1309.

GAGE.--Water-stage recorder. Altitude of gage is 3,367 ft (NGVD 29, from river-profile survey). Prior to Apr. 4, 1912, staff gage at site about 150 ft upstream 

at datum about 2.0 ft higher. Apr. 4, 1912, to June 13, 1947, chain or staff gage at site 300 ft upstream at datum 2.07 ft higher.

REMARKS.--Several diversions for irrigation upstream from station. Some storage in coulees. Records of chemical analyses for the periods May to September 

1949, December 1949 to July 1950, and October 1950 to July 1951, suspended-sediment loads for the period March 1949 to December 1951, and water 

temperatures for the period of June 1949 to December 1951, are published in reports of U.S. Geological Survey (published as "Little Missouri River at Alzada, 

MT"). 

Magnitude and probability of annual low flow

based on 45 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.00 0.00 0.00 0.00 0.00 --

3 .00 .00 .00 .00 .00 --

7 .00 .00 .00 .00 .00 --

14 .00 .00 .00 .00 .00 --

30 .04 .00 .00 .00 .00 --

60 .09 .00 .00 .00 .00 --

90 .19 .01 .00 .00 .00 --

120 .41 .05 .00 .00 .00 --

183 2.1 .19 .04 .01 .00 --

Magnitude and probability of seasonal low flow from

March-June based on 49 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.51 0.00 0.00 0.00 0.00 --

3 .63 .00 .00 .00 .00 --

7 .79 .05 .00 .00 .00 --

14 1.3 .12 .01 .00 .00 --

30 4.8 .53 .13 .03 .00 --

Magnitude and probability of seasonal low flow from

November-February based on 49 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.04 0.00 0.00 0.00 0.00 --

3 .04 .00 .00 .00 .00 --

7 .05 .00 .00 .00 .00 --

14 .10 .00 .00 .00 .00 --

30 .16 .00 .00 .00 .00 --

Duration of daily mean flows based on 49 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

0.02 0.04 0.11 0.22 0.45 0.67 0.89 1.7

40% 30% 20% 15% 10% 5% 2% 1%

5.1 13 32 62 143 428 1,020 1,630

Magnitude and probability of annual high flow

based on 49 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 1,680 3,010 3,810 4,650 5,170 --

3 1,430 2,610 3,310 4,030 4,460 --

7 939 1,800 2,340 2,940 3,320 --

15 592 1,180 1,580 2,050 2,360 --

30 373 771 1,050 1,380 1,610 --

60 239 511 705 942 1,110 --

90 176 388 548 755 906 --

Magnitude and probability of seasonal low flow from

July-October based on 51 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.00 0.00 0.00 0.00 0.00 0.00

3 .00 .00 .00 .00 .00 .00

7 .00 .00 .00 .00 .00 .00

14 .02 .00 .00 .00 .00 .00

30 .10 .00 .00 .00 .00 .00

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 493 0.00 23 75 52

November 97 .00 6.4 19 52

December 22 .00 2.3 4.4 52

January 10 .00 1.6 2.5 49

February 663 .00 63 136 49

March 1,050 .11 197 219 49

April 1,450 .11 206 331 53

May 905 .04 126 194 53

June 2,160 .00 215 337 54

July 314 .00 50 68 54

August 442 .00 39 74 54

September 358 .00 30 69 55

Annual 324 1.9 77 67 49
Statistical Summaries of Streamflow 229

06334630 Box Elder Creek at Webster, Mont.

Site Number 204

LOCATION.--Lat 45°54'25", long 104°03'30" (NAD 27), NE1⁄4 sec.30, T.2 N., R.62 E., Fallon County, on left bank at Wayne Cox Ranch, 0.5 mi west of MontanaSouth Dakota State line, 2 mi upstream from Coal Bank Creek, 17 mi southeast of Webster, and 33 mi southeast of Baker.

DRAINAGE AREA.--1,092 mi2 . 

PERIOD OF RECORD.--14 years. September 1959 to September 1973 (discontinued).

REVISED RECORDS.--WSP 1729: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 2,950 ft (NGVD 29, from topographic map). Prior to Nov. 8, 1960, nonrecording gage at site 300 ft upstream 

at different datum.

REMARKS.--Diversions for irrigation of about 14,000 acres upstream from station.

Magnitude and probability of annual low flow

based on 12 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.69 0.18 0.04 0.00 -- --

3 .87 .31 .10 .00 -- --

7 1.2 .46 .15 .00 -- --

14 1.4 .54 .19 .00 -- --

30 2.3 .70 .29 .12 -- --

60 3.0 1.7 1.2 .96 -- --

90 3.4 2.2 1.8 1.6 -- --

120 4.3 2.7 2.3 2.0 -- --

183 6.3 3.7 3.2 2.9 -- --

Magnitude and probability of seasonal low flow from

March-June based on 13 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 3.9 0.91 0.28 0.00 -- --

3 4.9 .96 .31 .10 -- --

7 5.7 1.4 .60 .28 -- --

14 7.5 2.4 1.3 .72 -- --

30 19 6.3 3.6 2.3 -- --

Magnitude and probability of seasonal low flow from

November-February based on 12 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.85 0.28 0.09 0.00 -- --

3 1.0 .40 .17 .00 -- --

7 1.3 .49 .19 .00 -- --

14 1.5 .57 .23 .00 -- --

30 2.4 .99 .61 .40 -- --

Duration of daily mean flows based on 13 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

0.19 0.38 0.95 1.8 3.1 4.3 5.3 7.3

40% 30% 20% 15% 10% 5% 2% 1%

13 28 65 108 197 432 964 1,690

Magnitude and probability of annual high flow

based on 13 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 1,400 3,450 5,230 7,840 -- --

3 1,300 3,140 4,520 6,210 -- --

7 1,130 2,590 3,480 4,370 -- --

15 779 1,730 2,270 2,770 -- --

30 521 1,040 1,290 1,480 -- --

60 320 660 836 990 -- --

90 250 524 669 798 -- --

Magnitude and probability of seasonal low flow from

July-October based on 12 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1.6 0.31 0.07 0.00 -- --

3 1.7 .47 .13 .00 -- --

7 2.2 .81 .20 .00 -- --

14 2.6 1.0 .30 .00 -- --

30 3.5 1.1 .43 .16 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 452 0.82 42 124 13

November 66 2.6 9.9 17 13

December 27 1.3 5.3 6.6 13

January 10 1.0 4.2 3.2 13

February 425 4.2 63 117 13

March 1,050 8.4 249 310 13

April 860 3.8 215 272 13

May 1,050 6.2 222 299 13

June 658 2.4 199 201 13

July 122 .67 44 39 13

August 46 .82 15 15 13

September 90 2.5 20 24 13

Annual 186 4.3 91 65 13
230 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

06336500 Beaver Creek at Wibaux, Mont.

Site Number 205

LOCATION.--Lat 46°59'24", long 104°11'00" (NAD 27), NE1⁄4NE1⁄4 sec.12, T.14 N., R.59 E., Wibaux County, Hydrologic Unit 10110204, on left bank 20 ft 

upstream from bridge on old U.S. Highway 10, at Wibaux, 12 mi upstream from Little Beaver Creek, and at river mile 62.5.

DRAINAGE AREA.--351 mi2 . 

PERIOD OF RECORD.--April 1938 to June 1969, October 1978 to September 1984.

REVISED RECORDS.--WSP 1309: 1943, 1947-48. WSP 1509: 1942(M), 1944-45, 1946(M).

GAGE.--Water-stage recorder. Altitude of gage is 2,650 ft (NGVD 29, by barometer). Prior to Sept. 21, 1940, nonrecording gages at site about 500 ft upstream 

at different datums.

REMARKS.--Several known diversions for irrigation upstream from station.

Magnitude and probability of annual low flow

based on 34 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.00 0.00 0.00 0.00 0.00 --

3 .00 .00 .00 .00 .00 --

7 .00 .00 .00 .00 .00 --

14 .00 .00 .00 .00 .00 --

30 .01 .00 .00 .00 .00 --

60 .11 .00 .00 .00 .00 --

90 .20 .03 .00 .00 .00 --

120 .34 .05 .01 .00 .00 --

183 .61 .16 .06 .00 .00 --

Magnitude and probability of seasonal low flow from

March-June based on 36 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.50 0.00 0.00 0.00 0.00 --

3 .55 .00 .00 .00 .00 --

7 .67 .01 .00 .00 .00 --

14 1.0 .09 .00 .00 .00 --

30 2.0 .54 .23 .11 .04 --

Magnitude and probability of seasonal low flow from

November-February based on 36 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.00 0.00 0.00 0.00 0.00 --

3 .00 .00 .00 .00 .00 --

7 .00 .00 .00 .00 .00 --

14 .07 .00 .00 .00 .00 --

30 .28 .00 .00 .00 .00 --

Duration of daily mean flows based on 35 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

0.02 0.04 0.11 0.22 0.44 0.66 0.88 1.2

40% 30% 20% 15% 10% 5% 2% 1%

1.8 3.1 6.1 9.4 18 52 243 589

Magnitude and probability of annual high flow

based on 35 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 594 1,790 2,850 4,350 5,490 --

3 444 1,400 2,300 3,610 4,660 --

7 295 948 1,570 2,500 3,240 --

15 175 575 970 1,580 2,090 --

30 102 324 539 868 1,140 --

60 58 179 295 473 623 --

90 43 126 204 322 420 --

Magnitude and probability of seasonal low flow from

July-October based on 35 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.00 0.00 0.00 0.00 0.00 --

3 .00 .00 .00 .00 .00 --

7 .00 .00 .00 .00 .00 --

14 .01 .00 .00 .00 .00 --

30 .06 .00 .00 .00 .00 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 5.4 0.00 1.0 1.3 36

November 38 .00 2.3 6.2 36

December 2.8 .00 .95 .80 36

January 8.8 .00 .96 1.6 36

February 241 .00 20 45 36

March 456 1.2 117 134 36

April 566 .62 79 138 37

May 33 .37 7.3 7.9 37

June 136 .02 21 35 37

July 109 .00 11 21 36

August 10 .00 1.5 2.4 36

September 34 .00 1.7 5.7 36

Annual 62 .25 21 19 35
Statistical Summaries of Streamflow 231

12300000 Kootenay River at Newgate, British Columbia

Site Number 206

LOCATION.--Lat 49°00’52", long 115°10’24" (NAD 27), on left bank at old highway bridge site, 1.1 mi north of international boundary, 2 mi southeast of 

Newgate, and at river mile 272.1.

DRAINAGE AREA.--7,660 mi2 approximately . 

PERIOD OF RECORD.--41 years (1930-71).

GAGE.--Water-stage recorder. Altitude of gage is 2,310.23 ft (NGVD 29, datum of Geodetic Survey of Canada). Prior to Oct. 1, 1940, nonrecording gage at same 

site at datum 1.00 ft higher. Oct. 1, 1940, to Apr. 30, 1947, nonrecording gage at present site and datum.

REMARKS.--Diversions for irrigation of about 8,500 acres upstream from station. Records give total flow of main channel and slough.

Magnitude and probability of annual low flow

based on 41 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1,700 1,420 1,280 1,180 1,060 --

3 1,750 1,470 1,330 1,220 1,100 --

7 1,890 1,600 1,450 1,330 1,200 --

14 2,050 1,760 1,600 1,470 1,330 --

30 2,220 1,930 1,790 1,670 1,540 --

60 2,440 2,090 1,940 1,830 1,720 --

90 2,640 2,250 2,080 1,970 1,860 --

120 2,990 2,500 2,290 2,140 1,990 --

183 3,810 3,200 2,960 2,790 2,630 --

Magnitude and probability of seasonal low flow from

March-June based on 41 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 2,190 1,900 1,770 1,660 1,550 --

3 2,240 1,950 1,820 1,710 1,590 --

7 2,300 2,020 1,890 1,790 1,670 --

14 2,390 2,100 1,960 1,850 1,730 --

30 2,630 2,270 2,110 1,990 1,870 --

Magnitude and probability of seasonal low flow from

November-February based on 41 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1,710 1,420 1,290 1,190 1,070 --

3 1,780 1,480 1,340 1,230 1,120 --

7 1,920 1,600 1,460 1,340 1,220 --

14 2,070 1,780 1,610 1,490 1,370 --

30 2,230 1,940 1,800 1,690 1,590 --

Duration of daily mean flows based on 41 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

1,560 1,640 1,900 2,270 2,710 3,180 3,960 4,990

40% 30% 20% 15% 10% 5% 2% 1%

6,390 9,200 15,600 21,600 29,700 41,200 52,200 63,300

Magnitude and probability of annual high flow

based on 41 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 57,900 72,500 79,900 87,400 91,900 --

3 55,800 69,900 77,100 84,300 88,600 --

7 51,100 64,600 71,700 79,100 83,600 --

15 45,800 58,600 65,700 73,400 78,400 --

30 41,200 51,600 57,200 63,200 67,000 --

60 34,700 42,300 46,000 49,600 51,800 --

90 28,700 34,500 37,300 39,900 41,400 --

Magnitude and probability of seasonal low flow from

July-October based on 41 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 3,970 3,320 3,070 2,900 2,740 --

3 4,020 3,390 3,150 2,990 2,840 --

7 4,130 3,480 3,230 3,060 2,910 --

14 4,290 3,590 3,330 3,150 2,990 --

30 4,600 3,840 3,560 3,370 3,200 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 11,600 2,880 5,290 1,900 42

November 7,370 2,100 4,150 1,250 42

December 5,760 1,910 3,080 904 42

January 4,490 1,570 2,580 570 42

February 4,710 1,540 2,560 569 42

March 5,190 1,760 2,790 638 42

April 24,100 2,540 7,180 4,000 41

May 41,400 10,000 26,500 7,900 41

June 60,800 10,000 37,200 11,000 41

July 40,200 8,320 20,000 7,210 41

August 14,600 5,350 8,620 2,070 41

September 14,500 3,880 6,090 1,820 41

Annual 14,300 6,110 10,500 2,150 41
232 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

12301300 Tobacco River near Eureka, Mont.

Site Number 207

LOCATION.--Lat 48°53'37", long 115°05'13" (NAD 27), in NW1⁄4SE1⁄4SE1⁄4 sec.9, T.36 N., R.27 W., Lincoln County, Hydrologic Unit 17010101, on right bank 

0.2 mi upstream from Indian Creek, 1.8 mi northwest of Eureka, and 2.8 mi upstream from Lake Koocanusa flow line.

DRAINAGE AREA.--440 mi2.

PERIOD OF RECORD.--September 1958 to current year (2002).

GAGE.--Water-stage recorder. Altitude of gage is 2,518.85 ft (NGVD 29).

REMARKS.--Diversions for irrigation of about 4,500 acres upstream from station. U.S. Geological Survey satellite telemeter at station.

Magnitude and probability of annual low flow

based on 43 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 50 37 31 26 22 --

3 55 41 34 29 24 --

7 61 45 38 32 26 --

14 68 50 42 35 28 --

30 77 57 47 39 31 --

60 85 63 52 44 36 --

90 89 67 57 49 41 --

120 94 72 62 55 48 --

183 101 76 67 60 54 --

Magnitude and probability of seasonal low flow from

March-June based on 44 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 87 63 54 48 43 --

3 92 68 60 54 48 --

7 99 75 65 59 53 --

14 107 81 72 65 60 --

30 133 95 82 73 64 --

Magnitude and probability of seasonal low flow from

November-February based on 43 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 51 38 33 30 26 --

3 56 43 38 35 31 --

7 63 50 45 42 38 --

14 70 56 51 47 44 --

30 80 63 57 53 49 --

Duration of daily mean flows based on 44 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

39 47 55 68 84 100 116 135

40% 30% 20% 15% 10% 5% 2% 1%

172 246 426 552 713 975 1,270 1,440

Magnitude and probability of annual high flow

based on 44 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 1,380 1,850 2,120 2,410 2,600 --

3 1,280 1,690 1,920 2,170 2,330 --

7 1,140 1,500 1,700 1,910 2,060 --

15 1,010 1,320 1,490 1,680 1,800 --

30 908 1,180 1,330 1,480 1,590 --

60 779 1,000 1,120 1,250 1,330 --

90 669 867 971 1,080 1,150 --

Magnitude and probability of seasonal low flow from

July-October based on 43 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 80 54 41 32 24 --

3 81 54 42 33 24 --

7 83 56 43 34 25 --

14 87 59 46 36 27 --

30 94 65 50 40 30 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 342 51 113 49 44

November 368 56 132 71 44

December 415 60 115 64 44

January 248 54 102 42 44

February 492 50 111 68 44

March 422 67 157 80 44

April 883 140 424 192 44

May 1,470 371 777 239 44

June 1,500 196 741 300 44

July 576 80 311 136 44

August 235 37 127 49 44

September 239 29 108 40 44

Annual 496 109 268 84 44
Statistical Summaries of Streamflow 233

12301500 Kootenai River near Rexford, Mont.

Site Number 208

LOCATION.--Lat 48°52'28", long 115°13'37" (NAD 27), in SE1⁄4NE1⁄4NW1⁄4 sec.21, T.36 N., R.28 W., Lincoln County, near right bank on downstream side of 

bridge on State Highway 37, 300 ft downstream from Sullivan Creek, 1.1 mi southwest of Rexford, 3.5 mi downstream from Tobacco River, and at river mile 

260.5.

DRAINAGE AREA.--8,420 mi2, approximately . 

PERIOD OF RECORD.--15 years. March 1929 to November 1940, October 1967 to September 1971 (discontinued).

REVISED RECORDS--WSP 1042: 1933.

GAGE.--Nonrecording gage read once or twice daily. Altitude of gage is 2,244.10 ft (NGVD 29, U.S. Army Corps of Engineers bench mark). Mar. 24, 1929, to 

Oct. 15, 1931, nonrecording gage, Oct. 16, 1931, to June 4, 1932, water-stage recorder, June 5, 1932, to Nov. 18, 1940, nonrecording gages, all at present site 

at datum 13.14 ft higher. 

REMARKS.--Diversions for irrigation of about 13,900 acres upstream from station. 

Magnitude and probability of annual low flow

based on 14 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1,490 1,230 1,130 1,070 -- --

3 1,560 1,300 1,200 1,130 -- --

7 1,680 1,400 1,290 1,210 -- --

14 1,860 1,580 1,460 1,360 -- --

30 2,100 1,820 1,680 1,580 -- --

60 2,350 2,010 1,890 1,810 -- --

90 2,570 2,160 2,010 1,910 -- --

120 2,920 2,370 2,160 2,010 -- --

183 3,580 3,010 2,790 2,640 -- --

Magnitude and probability of seasonal low flow from

March-June based on 15 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 2,420 2,040 1,870 1,740 -- --

3 2,450 2,080 1,910 1,790 -- --

7 2,500 2,110 1,950 1,820 -- --

14 2,560 2,170 1,990 1,870 -- --

30 2,780 2,340 2,160 2,040 -- --

Magnitude and probability of seasonal low flow from

November-February based on 15 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1,530 1,270 1,160 1,090 -- --

3 1,620 1,340 1,230 1,150 -- --

7 1,740 1,440 1,320 1,230 -- --

14 1,920 1,610 1,480 1,390 -- --

30 2,140 1,830 1,720 1,650 -- --

Duration of daily mean flows based on 15 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

1,540 1,620 1,890 2,270 2,730 3,250 3,950 4,900

40% 30% 20% 15% 10% 5% 2% 1%

6,140 9,180 16,200 21,500 28,400 39,400 49,000 58,700

Magnitude and probability of annual high flow

based on 15 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 53,500 65,900 73,300 81,800 -- --

3 51,700 64,300 71,700 80,200 -- --

7 47,600 59,400 66,000 73,400 -- --

15 42,400 53,300 59,400 66,000 -- --

30 38,100 47,200 52,200 57,700 -- --

60 32,100 40,000 44,600 50,000 -- --

90 26,600 32,800 36,600 40,900 -- --

Magnitude and probability of seasonal low flow from

July-October based on 15 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 3,550 3,060 2,880 2,760 -- --

3 3,590 3,100 2,920 2,800 -- --

7 3,690 3,160 2,960 2,830 -- --

14 3,790 3,240 3,040 2,900 -- --

30 4,100 3,440 3,180 3,010 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 8,540 2,920 4,620 1,420 15

November 7,840 2,170 4,030 1,450 15

December 5,530 1,990 2,970 828 15

January 5,020 1,620 2,680 786 15

February 3,860 1,670 2,620 637 15

March 4,910 1,880 2,960 707 15

April 24,500 3,110 7,850 5,370 16

May 42,000 10,000 26,100 8,090 16

June 49,600 10,000 34,800 10,300 16

July 27,400 9,780 17,600 5,920 16

August 11,800 5,740 8,000 1,900 16

September 7,820 4,090 5,490 1,050 16

Annual 13,800 6,630 10,100 2,270 15
234 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

12301933 Kootenai River below Libby Dam, near Libby, Mont.

Site Number 209

LOCATION.--Lat 48°24'03", long 115°19'11" (NAD 27), in SW1⁄4SW1⁄4SW1⁄4 sec.33, T.31 N., R.29 W., Lincoln County, Hydrologic Unit 17010101, Kootenai 

National Forest, on right bank 0.7 mi downstream from Libby Dam, 2.8 mi upstream from Fisher River, 11 mi east of Libby, and at river mile 221.4.

DRAINAGE AREA.--8,985 mi2, approximately.

PERIOD OF RECORD.--October 1971 to current year (2002).

GAGE.--Water-stage recorder. Altitude of gage is 2,100 ft (NGVD 29, U.S. Army Corps of Engineers bench mark). Prior to Feb. 13, 1974, nonrecording gage at 

site 0.4 mi upstream at same datum.

REMARKS.--Flow completely regulated by Lake Koocanusa after Mar. 21, 1972 . Diversions for irrigation of about 13,000 acres, revised, from tributaries 

upstream from station in Canada and the United States. U.S. Army Corps of Engineers satellite telemetry at station.

Magnitude and probability of annual low flow

based on 29 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 3,280 2,790 2,530 2,320 2,090 --

3 3,350 2,860 2,600 2,390 2,170 --

7 3,360 2,870 2,640 2,470 2,290 --

14 3,390 2,900 2,680 2,520 2,360 --

30 3,490 2,950 2,750 2,610 2,450 --

60 3,660 3,040 2,830 2,660 2,480 --

90 4,410 3,310 2,950 2,720 2,520 --

120 5,720 3,970 3,300 2,850 2,600 --

183 7,300 5,250 4,410 3,810 3,230 --

Magnitude and probability of seasonal low flow from

March-June based on 30 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 3,350 2,860 2,610 2,410 2,190 --

3 3,380 2,910 2,680 2,490 2,300 --

7 3,390 2,930 2,720 2,570 2,410 --

14 3,450 2,970 2,780 2,640 2,510 --

30 3,600 3,030 2,840 2,710 2,610 --

Magnitude and probability of seasonal low flow from

November-February based on 29 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 3,820 3,130 2,920 2,500 2,310 --

3 3,870 3,160 2,950 2,520 2,330 --

7 4,500 3,380 2,990 2,600 2,340 --

14 5,110 3,570 3,030 2,670 2,360 --

30 7,200 4,660 3,710 3,080 2,500 --

Duration of daily mean flows based on 30 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

2,300 2,400 2,710 3,160 3,660 4,150 6,240 8,700

40% 30% 20% 15% 10% 5% 2% 1%

12,200 15,400 18,800 20,700 22,600 24,500 29,800 32,700

Magnitude and probability of annual high flow

based on 30 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 25,600 30,500 34,000 38,600 42,200 --

3 24,800 29,700 33,200 37,800 41,400 --

7 24,300 29,000 31,900 35,500 38,100 --

15 23,300 27,100 29,200 31,400 32,900 --

30 22,000 25,600 27,400 29,200 30,400 --

60 20,300 23,400 24,500 25,500 25,900 --

90 18,600 20,600 21,200 21,600 21,700 --

Magnitude and probability of seasonal low flow from

July-October based on 29 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 3,760 2,990 2,700 2,500 2,230 --

3 4,190 3,190 2,780 2,510 2,250 --

7 4,780 3,440 2,900 2,530 2,290 --

14 5,340 3,770 3,130 2,680 2,390 --

30 6,450 4,480 3,630 3,010 2,580 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 32,100 5,940 14,200 5,730 30

November 24,900 5,720 15,500 4,720 30

December 24,300 2,640 15,000 5,820 30

January 24,700 3,080 14,500 6,410 30

February 22,300 3,090 11,600 5,820 30

March 12,900 3,280 6,260 2,890 30

April 16,400 2,930 5,240 3,030 30

May 16,200 2,820 6,190 3,980 30

June 25,800 3,020 10,700 7,140 30

July 27,300 3,160 10,700 6,280 30

August 18,500 2,820 10,500 4,440 30

September 19,300 5,200 10,200 3,460 30

Annual 15,700 6,210 10,900 2,100 30
Statistical Summaries of Streamflow 235

12302000 Fisher River near Jennings, Mont.

Site Number 210

LOCATION.--Lat 48°14'33", long 115°17'30" (NAD 27), in NW1⁄4NE1⁄4SW1⁄4 sec.27, T.29 N., R.29 W., Lincoln County, on left bank 0.4 mi downstream from 

bridge, 2.3 mi downstream from Wolf Creek, 8.5 mi southeast of Jennings, and 8.6 mi upstream from mouth. Prior to Dec. 17, 1965, at site 0.4 mi upstream.

DRAINAGE AREA.--780 mi2.

PERIOD OF RECORD.--18 years (1951-69).

GAGE.--Water-stage recorder. Altitude of gage is 2,433.94 ft (NGVD 29, U.S. Army Corps of Engineers bench mark). Dec. 15, 1950, to Dec. 16, 1965, at site 

0.4 mi upstream at datum 9.29 ft higher.

REMARKS.--Diversions for irrigation of about 700 acres upstream from station. Water-quality records for the water years 1966-69 are published in reports of the 

U.S. Geological Survey.

Magnitude and probability of annual low flow

based on 18 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 90 72 63 57 -- --

3 92 77 70 65 -- --

7 95 81 75 71 -- --

14 99 86 80 76 -- --

30 107 91 85 80 -- --

60 117 97 88 82 -- --

90 130 105 94 86 -- --

120 142 112 100 91 -- --

183 169 131 116 106 -- --

Magnitude and probability of seasonal low flow from

March-June based on 19 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 204 140 113 94 -- --

3 209 146 121 102 -- --

7 218 154 129 110 -- --

14 240 169 141 120 -- --

30 344 237 188 153 -- --

Magnitude and probability of seasonal low flow from

November-February based on 18 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 103 79 67 59 -- --

3 109 86 76 68 -- --

7 121 97 86 78 -- --

14 133 104 91 82 -- --

30 152 115 101 90 -- --

Duration of daily mean flows based on 18 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

73 80 96 109 134 162 189 247

40% 30% 20% 15% 10% 5% 2% 1%

327 464 821 1,090 1,510 2,130 2,890 3,450

Magnitude and probability of annual high flow

based on 18 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 3,370 4,480 5,020 5,560 -- --

3 3,150 4,230 4,780 5,350 -- --

7 2,810 3,800 4,350 4,940 -- --

15 2,460 3,310 3,810 4,370 -- --

30 2,100 2,740 3,100 3,500 -- --

60 1,720 2,230 2,530 2,890 -- --

90 1,400 1,790 2,040 2,340 -- --

Magnitude and probability of seasonal low flow from

July-October based on 18 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 99 82 75 69 -- --

3 100 84 76 71 -- --

7 102 85 78 72 -- --

14 105 88 81 77 -- --

30 111 93 86 81 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 337 84 166 77 18

November 468 83 218 105 18

December 502 93 243 115 18

January 487 123 237 104 19

February 956 112 338 207 19

March 700 128 370 144 19

April 3,260 496 1,480 731 19

May 3,240 960 1,890 623 19

June 1,650 460 942 329 19

July 572 184 301 92 19

August 206 91 139 27 19

September 236 82 128 41 19

Annual 859 369 531 128 18
236 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

12302055 Fisher River near Libby, Mont.

Site Number 211

LOCATION.--Lat 48°21'20", long 115°18'50" (NAD 27), in NW1⁄4 NE1⁄4NW1⁄4 sec.21, T.30 N., R.29 W., Lincoln County, Hydrologic Unit 17010102, on left bank 

0.8 mi upstream from mouth and 11.4 mi east of Libby.

DRAINAGE AREA.--838 mi2.

PERIOD OF RECORD.--September 1967 to current year (2002).

GAGE.--Water-stage recorder. Altitude of gage is 2,134.10 ft (NGVD 29, U.S. Army Corps of Engineers bench mark).

REMARKS.--Diversions of about 700 acres upstream from station. U.S. Army Corps of Engineers satellite telemeter at station.

Magnitude and probability of annual low flow

based on 34 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 74 56 48 42 36 --

3 80 62 54 48 42 --

7 86 67 60 54 48 --

14 92 73 64 57 50 --

30 102 80 69 61 53 --

60 110 86 74 65 56 --

90 117 91 79 70 61 --

120 126 99 87 79 70 --

183 149 112 98 89 81 --

Magnitude and probability of seasonal low flow from

March-June based on 35 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 220 138 110 93 77 --

3 230 146 118 100 84 --

7 249 160 129 110 92 --

14 284 181 145 122 101 --

30 402 246 192 157 126 --

Magnitude and probability of seasonal low flow from

November-February based on 34 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 83 59 50 43 37 --

3 92 67 58 51 44 --

7 105 78 67 60 53 --

14 114 85 76 70 66 --

30 133 98 88 81 76 --

Duration of daily mean flows based on 35 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

58 68 82 98 119 143 173 219

40% 30% 20% 15% 10% 5% 2% 1%

297 462 762 995 1,310 1,880 2,590 3,010

Magnitude and probability of annual high flow

based on 35 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 2,690 4,230 5,340 6,850 8,040 --

3 2,470 3,770 4,680 5,860 6,760 --

7 2,160 3,140 3,750 4,480 4,990 --

15 1,830 2,640 3,140 3,730 4,140 --

30 1,570 2,260 2,700 3,250 3,640 --

60 1,350 1,920 2,260 2,660 2,930 --

90 1,160 1,670 1,970 2,330 2,570 --

Magnitude and probability of seasonal low flow from

July-October based on 34 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 96 74 64 56 47 --

3 98 75 64 56 48 --

7 99 76 65 57 49 --

14 102 78 67 58 50 --

30 107 82 71 62 52 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 305 76 136 51 35

November 819 87 231 184 35

December 1,170 90 244 218 35

January 1,270 78 258 224 35

February 1,960 95 353 360 35

March 2,400 134 594 478 35

April 2,750 318 1,230 637 35

May 3,300 482 1,420 646 35

June 1,800 221 834 415 35

July 532 93 296 133 35

August 244 56 140 48 35

September 204 55 120 34 35

Annual 938 169 488 202 35
Statistical Summaries of Streamflow 237

12302500 Granite Creek near Libby, Mont.

Site Number 212

LOCATION.--Lat 48°18'07", long 115°35'29" (NAD 27), in SE1⁄4NE1⁄4SW1⁄4 sec.5, T.29 N., R.31 W., Lincoln County, at Glacier Silver Lead Mine, 2.5 mi upstream 

from mouth and 6.3 mi southwest of Libby.

DRAINAGE AREA.--23.6 mi2.

PERIOD OF RECORD.--16 years (1936-43, 1960-69).

REVISED RECORDS.--WSP 1246: 1933.

GAGE.--Water-stage recorder. Concrete control since Sept. 9, 1938. Altitude of gage is 2,780 ft (NGVD 29, from topographic map). Prior to Sept. 16, 1960, 

nonrecording gages at present datum within 25 ft of site. Crest-stage gage July 2, 1959, to Sept. 15, 1960.

Magnitude and probability of annual low flow

based on 14 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 6.8 5.2 4.6 4.2 -- --

3 7.1 5.4 4.7 4.2 -- --

7 7.6 5.8 5.1 4.6 -- --

14 8.2 6.4 5.7 5.2 -- --

30 9.9 7.7 6.7 6.1 -- --

60 13 9.0 7.6 6.7 -- --

90 16 11 9.1 7.9 -- --

120 19 13 11 9.4 -- --

183 21 15 13 11 -- --

Magnitude and probability of seasonal low flow from

March-June based on 17 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 13 9.6 8.3 7.5 -- --

3 14 10 8.6 7.7 -- --

7 15 10 8.9 7.9 -- --

14 17 12 10 8.7 -- --

30 26 17 13 11 -- --

Magnitude and probability of seasonal low flow from

November-February based on 16 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 9.7 6.8 5.3 4.2 -- --

3 10 7.2 5.6 4.4 -- --

7 11 7.5 5.8 4.6 -- --

14 12 8.3 6.4 5.3 -- --

30 15 10 7.6 6.1 -- --

Duration of daily mean flows based on 16 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

4.7 5.4 7.2 9.6 14 18 22 30

40% 30% 20% 15% 10% 5% 2% 1%

41 62 109 148 202 286 379 469

Magnitude and probability of annual high flow

based on 16 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 466 668 893 1,330 -- --

3 396 516 633 832 -- --

7 362 448 505 579 -- --

15 316 385 428 480 -- --

30 290 343 372 403 -- --

60 238 281 304 327 -- --

90 198 228 242 255 -- --

Magnitude and probability of seasonal low flow from

July-October based on 16 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 7.6 5.3 4.6 4.2 -- --

3 7.8 5.5 4.7 4.3 -- --

7 8.3 5.9 5.1 4.6 -- --

14 9.1 6.5 5.8 5.3 -- --

30 11 7.7 6.8 6.1 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 74 7.2 27 20 18

November 92 5.3 33 24 18

December 158 8.7 39 41 17

January 27 3.9 20 6.7 17

February 75 4.5 25 21 17

March 71 9.0 30 15 17

April 258 44 116 55 17

May 283 161 234 38 17

June 434 97 224 88 17

July 139 24 72 32 17

August 38 8.6 22 9.0 19

September 57 7.3 18 13 19

Annual 84 44 70 12 16
238 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

12303000 Kootenai River at Libby, Mont.

Site Number 213

LOCATION.--Lat 48°24'03", long 115°33'08" (NAD 27), in SW1⁄4SE1⁄4SW1⁄4 sec.34, T.31 N., R.31 W., Lincoln County, Hydrologic Unit 17010101, on right bank 

1,800 ft downstream from highway bridge at Libby, 0.8 mi downstream from Libby Creek, and at river mile 204.3. 

DRAINAGE AREA.--10,240 mi2, approximately. 

PERIOD OF RECORD.--October 1910 to September 1991 (discontinued). Monthly discharge only for some periods, published in WSP 1316. 

REVISED RECORDS.--WSP 1042: 1933. WSP 1246: 1912(M), 1915(M), 1916, 1918-19(M), 1924-27(M). 

GAGE.--Water-stage recorder. Altitude of gage is 2,041.54 ft (NGVD 29). Prior to Apr. 28, 1931, nonrecording gages at site 1,800 ft upstream at different datum. 

REMARKS.--Flow regulated by Lake Koocanusa (station number 12301920) after Mar. 21, 1972. Diversions for irrigation of about 14,500 acres from tributaries 

upstream from station in Canada and the United States.

Unregulated streamflow period

Magnitude and probability of annual low flow

based on 61 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 2,000 1,620 1,440 1,290 1,130 1,030

3 2,090 1,700 1,500 1,340 1,160 1,060

7 2,260 1,850 1,630 1,460 1,260 1,140

14 2,450 2,050 1,850 1,690 1,510 1,400

30 2,690 2,300 2,110 1,970 1,820 1,730

60 3,020 2,540 2,340 2,200 2,060 1,980

90 3,270 2,720 2,520 2,380 2,260 2,190

120 3,670 3,020 2,770 2,590 2,420 2,320

183 4,550 3,770 3,470 3,270 3,070 2,960

Magnitude and probability of seasonal low flow from

March-June based on 62 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 2,880 2,440 2,240 2,090 1,940 1,850

3 2,930 2,490 2,310 2,170 2,040 1,960

7 3,020 2,610 2,440 2,320 2,200 2,130

14 3,180 2,720 2,540 2,410 2,280 2,210

30 3,590 2,970 2,740 2,580 2,430 2,350

Magnitude and probability of seasonal low flow from

November-February based on 61 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 2,020 1,640 1,450 1,310 1,190 1,110

3 2,100 1,720 1,520 1,350 1,220 1,140

7 2,290 1,880 1,650 1,470 1,320 1,230

14 2,480 2,080 1,880 1,700 1,560 1,480

30 2,730 2,330 2,130 1,980 1,860 1,790

Duration of daily mean flows based on 62 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

1,800 2,170 2,410 2,760 3,460 4,150 5,070 6,070

40% 30% 20% 15% 10% 5% 2% 1%

8,110 11,400 18,700 24,400 32,400 44,700 59,100 67,600

Magnitude and probability of annual high flow

based on 62 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 63,500 80,200 88,600 97,100 102,000 106,000

3 61,500 77,900 86,300 94,800 100,000 104,000

7 56,700 72,200 80,200 88,400 93,500 97,800

15 51,000 64,900 72,100 79,400 83,900 87,700

30 45,200 56,600 62,300 68,000 71,400 74,300

60 38,000 46,100 49,900 53,500 55,500 57,100

90 31,800 38,100 41,000 43,800 45,300 46,500

Magnitude and probability of seasonal low flow from

July-October based on 61 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 4,570 3,810 3,530 3,350 3,180 3,090

3 4,630 3,860 3,570 3,380 3,210 3,110

7 4,740 3,930 3,630 3,430 3,240 3,140

14 4,880 4,040 3,740 3,530 3,340 3,240

30 5,210 4,320 4,000 3,790 3,600 3,500

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 13,700 3,180 6,140 2,260 62

November 9,630 2,410 5,050 1,660 62

December 11,500 2,260 3,930 1,510 62

January 7,760 1,760 3,330 1,030 62

February 7,340 1,730 3,420 1,050 62

March 7,800 2,420 3,910 1,160 62

April 31,100 3,470 10,300 4,900 62

May 49,000 10,000 30,100 9,130 62

June 68,200 10,000 40,100 12,000 62

July 45,800 9,180 21,800 7,780 62

August 15,500 5,110 9,790 2,270 62

September 21,100 4,150 7,180 2,820 62

Annual 16,600 6,510 12,100 2,520 62
Statistical Summaries of Streamflow 239

12303000 Kootenai River at Libby, Mont.—Continued

Site Number 213

Regulated streamflow period

Magnitude and probability of annual low flow

based on 18 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 3,450 2,970 2,720 2,520 -- --

3 3,630 3,100 2,840 2,640 -- --

7 3,820 3,210 2,910 2,680 -- --

14 3,960 3,290 2,990 2,760 -- --

30 4,240 3,410 3,100 2,890 -- --

60 4,790 3,940 3,670 3,510 -- --

90 5,310 4,310 3,990 3,800 -- --

120 6,160 4,740 4,250 3,930 -- --

183 7,680 5,810 5,070 4,550 -- --

Magnitude and probability of seasonal low flow from

March-June based on 19 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 3,870 3,260 3,010 2,820 -- --

3 3,960 3,350 3,090 2,900 -- --

7 4,150 3,490 3,210 3,000 -- --

14 4,330 3,640 3,390 3,230 -- --

30 4,730 3,880 3,580 3,390 -- --

Magnitude and probability of seasonal low flow from

November-February based on 18 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 4,050 3,190 2,930 2,750 -- --

3 4,300 3,270 2,940 2,770 -- --

7 5,010 3,530 3,020 2,800 -- --

14 5,590 3,760 3,130 2,880 -- --

30 8,170 5,260 4,130 3,370 -- --

Duration of daily mean flows based on 19 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

2,840 3,170 3,510 4,070 4,990 5,850 7,480 9,820

40% 30% 20% 15% 10% 5% 2% 1%

12,800 16,000 19,400 21,100 22,800 24,600 30,000 32,900

Magnitude and probability of annual high flow

based on 19 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 26,800 32,300 36,100 41,100 -- --

3 25,500 30,700 34,700 40,100 -- --

7 24,700 29,500 32,900 37,500 -- --

15 23,500 27,300 29,700 32,700 -- --

30 22,100 25,700 28,000 30,800 -- --

60 20,400 23,500 25,300 27,200 -- --

90 18,800 20,900 21,800 22,600 -- --

Magnitude and probability of seasonal low flow from

July-October based on 18 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 3,690 3,040 2,730 2,540 -- --

3 4,060 3,270 2,900 2,670 -- --

7 4,610 3,440 2,940 2,700 -- --

14 5,320 3,820 3,200 2,780 -- --

30 6,840 4,770 3,820 3,130 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 32,300 10,000 16,500 5,610 19

November 25,000 8,210 16,800 3,990 19

December 25,200 3,040 15,200 6,340 19

January 26,000 3,550 15,500 6,050 19

February 22,600 3,380 12,500 6,200 19

March 13,700 3,660 7,610 3,410 19

April 14,400 3,890 6,910 2,800 19

May 19,800 3,910 7,480 4,100 19

June 22,000 4,010 8,970 5,540 19

July 28,100 3,460 11,400 6,530 19

August 19,300 3,170 10,200 4,040 19

September 19,400 6,930 11,100 3,360 19

Annual 16,400 9,510 11,700 2,040 19
240 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

12303100 Flower Creek near Libby, Mont.

Site Number 214

LOCATION.--Lat 48°20'41", long 115°36'20" (NAD 27), in NW1⁄4SE1⁄4SE1⁄4 sec.19, T.30 N., R.31 W., Lincoln County, Hydrologic Unit 17010101, Kootenai 

National Forest, on left bank 30 ft downstream from road bridge, 0.3 mi upstream from South Fork, 1.0 mi upstream from reservoir, 4.0 mi southwest of Libby, 

and at river mile 4.5. 

DRAINAGE AREA.--11.1 mi2. 

PERIOD OF RECORD.--September 1960 to September 1992 (discontinued). 

REVISED RECORDS.--WDR MT-1972: Drainage area. 

GAGE.--Water-stage recorder. Altitude of gage is 2,866 ft (NGVD 29, from topographic map). 

REMARKS.--No known regulation or diversion upstream from station. 

Magnitude and probability of annual low flow

based on 31 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 4.4 3.8 3.6 3.4 3.2 --

3 4.5 3.9 3.7 3.5 3.3 --

7 4.7 4.1 3.8 3.6 3.4 --

14 4.9 4.3 4.0 3.8 3.6 --

30 5.3 4.6 4.2 4.0 3.8 --

60 6.3 5.1 4.6 4.2 3.8 --

90 7.0 5.6 5.0 4.6 4.1 --

120 7.7 6.0 5.3 4.8 4.3 --

183 8.6 6.6 5.8 5.2 4.6 --

Magnitude and probability of seasonal low flow from

March-June based on 32 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 6.4 4.7 4.1 3.7 3.3 --

3 6.6 4.9 4.2 3.8 3.4 --

7 7.0 5.1 4.4 3.9 3.5 --

14 7.6 5.5 4.7 4.1 3.6 --

30 9.1 6.4 5.3 4.6 3.9 --

Magnitude and probability of seasonal low flow from

November-February based on 32 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 4.8 4.0 3.6 3.4 3.2 --

3 5.0 4.1 3.8 3.5 3.3 --

7 5.3 4.3 3.9 3.7 3.5 --

14 5.6 4.5 4.0 3.8 3.6 --

30 6.1 4.8 4.3 4.0 3.8 --

Duration of daily mean flows based on 32 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

4.0 4.2 4.6 5.2 6.4 7.5 9.0 11

40% 30% 20% 15% 10% 5% 2% 1%

14 20 37 52 76 113 154 178

Magnitude and probability of annual high flow

based on 32 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 195 251 284 321 347 --

3 175 210 227 242 250 --

7 153 183 196 208 214 --

15 129 158 172 186 194 --

30 112 138 150 163 170 --

60 90 110 119 128 133 --

90 73 88 95 101 105 --

Magnitude and probability of seasonal low flow from

July-October based on 31 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 5.6 4.6 4.1 3.7 3.4 --

3 5.7 4.6 4.2 3.8 3.4 --

7 5.9 4.7 4.3 3.9 3.5 --

14 6.1 4.9 4.4 4.0 3.6 --

30 6.6 5.3 4.8 4.3 3.9 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 21 4.6 9.1 3.8 32

November 33 4.0 13 7.3 32

December 41 5.2 10 7.4 32

January 42 4.1 9.1 7.0 32

February 30 4.1 9.3 6.2 32

March 29 4.4 11 6.0 32

April 70 9.4 31 14 32

May 132 43 84 19 32

June 166 25 88 34 32

July 56 7.7 29 15 32

August 18 5.5 10 3.1 32

September 20 4.5 8.4 2.8 33

Annual 40 13 26 6.0 32
Statistical Summaries of Streamflow 241

12303500 Lake Creek at Troy, Mont.

Site Number 215

LOCATION.--Lat 48°26'49", long 115°52'34" (NAD 27), in SE1⁄4NW1⁄4SW1⁄4 sec.18. T.31 N., R.33 W., Lincoln County, Hydrologic Unit 17010101, Kootenai 

National Forest, on right bank 1,000 ft upstream from bridge on U.S. Highway 2, 0.5 mi upstream from mouth, 0.6 mi downstream from Stimson Lumber 

Company-owned dam, and 1.3 mi southeast of Troy. 

DRAINAGE AREA.--210 mi2. 

PERIOD OF RECORD.--January 1945 to September 1957, October 1982 to February 1996 (discontinued). 

REVISED RECORDS.--WSP 1216: Drainage area. 

GAGE.--Water-stage recorder and crest-stage gage. Altitude of gage is 1,900 ft (NGVD 29, from topographic map). Prior to Nov. 1, 1946, wire-weight gage at 

site 0.2 mi upstream at different datum. Jan. 11, 1945, to Sept. 30, 1957, water-stage recorder at same site at different datum. 

REMARKS.--Diurnal fluctuation caused by small hydroelectric plant 0.6 mi upstream. 

Magnitude and probability of annual low flow

based on 26 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 90 70 61 55 48 --

3 101 80 71 65 58 --

7 106 85 76 69 62 --

14 111 90 80 73 66 --

30 119 96 85 77 68 --

60 130 103 91 83 73 --

90 145 113 100 90 81 --

120 162 122 106 94 82 --

183 191 137 115 100 86 --

Magnitude and probability of seasonal low flow from

March-June based on 26 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 189 123 98 81 65 --

3 201 133 106 87 70 --

7 215 142 113 93 75 --

14 228 152 122 102 82 --

30 264 180 147 124 103 --

Magnitude and probability of seasonal low flow from

November-February based on 26 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 113 81 68 60 51 --

3 121 90 78 70 62 --

7 128 94 81 72 64 --

14 141 98 83 74 66 --

30 156 106 88 77 69 --

Duration of daily mean flows based on 25 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

73 82 99 115 145 172 207 256

40% 30% 20% 15% 10% 5% 2% 1%

331 452 668 826 1,050 1,410 1,930 2,150

Magnitude and probability of annual high flow

based on 25 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 1,900 2,490 2,840 3,270 3,570 --

3 1,800 2,360 2,710 3,140 3,440 --

7 1,650 2,200 2,540 2,970 3,270 --

15 1,500 2,000 2,320 2,720 3,000 --

30 1,340 1,780 2,050 2,380 2,620 --

60 1,130 1,490 1,700 1,950 2,120 --

90 970 1,260 1,420 1,600 1,720 --

Magnitude and probability of seasonal low flow from

July-October based on 26 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 104 81 70 62 54 --

3 114 92 82 74 66 --

7 119 98 89 82 74 --

14 123 102 93 86 79 --

30 130 107 97 89 81 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 401 92 177 85 26

November 692 89 270 164 26

December 984 96 280 197 26

January 534 76 232 126 27

February 1,090 86 286 229 27

March 626 120 305 147 26

April 1,020 184 611 224 26

May 1,900 642 1,190 371 26

June 2,120 316 1,030 469 26

July 1,000 162 438 223 26

August 339 110 206 59 26

September 215 92 148 30 26

Annual 639 207 428 123 25
242 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

12304500 Yaak River near Troy, Mont.

Site Number 216

LOCATION.--Lat 48°33'43", long 115°58'09" (NAD 27), in NE1⁄4SE1⁄4SE1⁄4 sec.5, T.32 N., R.34 W., Lincoln County, Hydrologic Unit 17010103, Kootenai 

National Forest, on right bank 500 ft upstream from bridge on U.S. Highway 2, 0.3 mi upstream from mouth, and 7.7 mi northwest of Troy.

DRAINAGE AREA.--766 mi2.

PERIOD OF RECORD.--October 1910 to September 1916 (fragmentary record), March 1956 to current year (2002).

GAGE.--Water-stage recorder. Altitude of gage is 1,839.2 ft (NGVD 29). Oct. 15, 1910, to Sept. 30, 1916, nonrecording gage at several sites within 11 mi of 

present site at various datums.

REMARKS.--Minor diversions for irrigation upstream from station. U.S. Army Corps of Engineers satellite telemeter at station.

Magnitude and probability of annual low flow

based on 46 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 93 72 62 55 47 --

3 99 76 66 59 51 --

7 105 81 70 63 55 --

14 113 88 77 69 60 --

30 125 98 85 75 65 --

60 140 109 95 84 73 --

90 151 117 103 94 84 --

120 166 129 115 106 98 --

183 197 146 129 119 109 --

Magnitude and probability of seasonal low flow from

March-June based on 47 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 254 159 126 104 85 --

3 264 168 134 111 91 --

7 289 184 146 121 98 --

14 320 202 161 134 110 --

30 474 286 216 171 130 --

Magnitude and probability of seasonal low flow from

November-February based on 46 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 105 76 64 56 49 --

3 115 83 70 61 53 --

7 129 92 78 68 59 --

14 144 103 88 79 71 --

30 168 118 101 91 81 --

Duration of daily mean flows based on 46 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

72 83 102 122 154 184 232 297

40% 30% 20% 15% 10% 5% 2% 1%

419 698 1,320 1,890 2,680 3,930 5,490 6,300

Magnitude and probability of annual high flow

based on 46 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 6,170 8,040 8,960 9,850 10,400 --

3 5,800 7,590 8,460 9,310 9,790 --

7 5,270 6,860 7,610 8,300 8,690 --

15 4,560 5,880 6,500 7,100 7,430 --

30 3,910 5,000 5,500 5,970 6,240 --

60 3,160 4,040 4,430 4,770 4,950 --

90 2,570 3,290 3,610 3,890 4,030 --

Magnitude and probability of seasonal low flow from

July-October based on 46 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 115 90 77 68 58 --

3 117 91 78 69 59 --

7 120 93 80 70 60 --

14 125 97 84 73 62 --

30 136 105 90 78 66 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 832 84 200 125 46

November 1,190 93 323 249 46

December 1,630 97 325 305 46

January 1,550 95 296 249 46

February 1,630 83 358 275 46

March 1,870 134 596 383 47

April 3,750 421 1,970 828 47

May 6,460 1,030 3,590 1,210 47

June 4,990 377 1,950 959 47

July 970 151 500 218 47

August 373 81 198 67 47

September 506 53 163 70 47

Annual 1,560 278 866 284 46
Statistical Summaries of Streamflow 243

12305000 Kootenai River at Leonia, Idaho

Site Number 217

LOCATION.--Lat 48°37'04", long 116°02'47" (NAD 27), in NW1⁄4NW1⁄4NW1⁄4 sec.20, T.33 N., R.34 W., Principal meridian, Lincoln County, Mont. Hydrologic 

Unit 17010104, on right bank at Leonia, 450 ft west of Montana-Idaho State line, 0.5 mi upstream from Boulder Creek, and at mile 171.6. 

DRAINAGE AREA.--11,740 mi2, approximately. 

PERIOD OF RECORD.--March 1928 to September 1983.

GAGE.--Water-stage recorder. Altitude of gage is 1,790.25 ft (NGVD 29). Prior to Oct. 1, 1970, at datum 90 ft lower. Prior to Nov. 13, 1928, nonrecording gage 

on bridge 250 ft upstream at datum 90.41 ft lower. 

REMARKS.--Diversions upstream from station for irrigation of about 14,600 acres. Flow regulated by Lake Koocanusa after Mar. 21, 1972.

Magnitude and probability of annual low flow

based on 42 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 2,220 1,670 1,390 900 0.00 --

3 2,310 1,820 1,590 1,430 1,260 --

7 2,540 2,010 1,760 1,570 1,380 --

14 2,810 2,260 2,010 1,830 1,630 --

30 3,150 2,600 2,360 2,180 1,990 --

60 3,550 2,900 2,650 2,480 2,320 --

90 3,880 3,110 2,820 2,630 2,450 --

120 4,300 3,420 3,070 2,830 2,590 --

183 5,060 4,110 3,750 3,500 3,270 --

Magnitude and probability of seasonal low flow from

March-June based on 43 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 3,400 2,710 2,370 1,880 0.00 --

3 3,570 2,920 2,650 2,450 2,260 --

7 3,680 3,040 2,770 2,580 2,390 --

14 3,890 3,210 2,920 2,720 2,510 --

30 4,510 3,620 3,250 2,990 2,740 --

Magnitude and probability of seasonal low flow from

November-February based on 42 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 2,240 1,710 1,510 1,370 1,230 --

3 2,320 1,850 1,600 1,460 1,330 --

7 2,560 2,040 1,770 1,610 1,460 --

14 2,840 2,280 2,020 1,860 1,710 --

30 3,170 2,610 2,370 2,240 2,110 --

Duration of daily mean flows based on 43 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

2,140 2,320 2,710 3,250 4,050 4,870 5,710 6,980

40% 30% 20% 15% 10% 5% 2% 1%

8,640 12,900 22,300 29,300 38,100 51,200 66,900 76,800

Magnitude and probability of annual high flow

based on 43 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 71,300 88,300 96,700 105,000 110,000 --

3 69,100 86,100 94,900 104,000 109,000 --

7 63,600 80,500 89,500 99,100 105,000 --

15 57,900 73,600 82,100 91,200 96,900 --

30 51,700 64,800 71,900 79,500 84,400 --

60 44,000 53,800 58,800 63,700 66,700 --

90 37,100 45,000 48,800 52,500 54,700 --

Magnitude and probability of seasonal low flow from

July-October based on 42 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 4,840 3,950 3,450 3,060 2,650 --

3 4,910 4,160 3,870 3,670 3,480 --

7 5,010 4,240 3,940 3,740 3,540 --

14 5,150 4,340 4,040 3,830 3,640 --

30 5,460 4,590 4,280 4,070 3,880 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 15,500 3,530 6,510 2,570 43

November 11,300 2,750 5,700 2,020 43

December 13,700 2,480 4,760 2,250 43

January 11,300 1,920 4,020 1,530 43

February 10,600 1,990 4,340 1,740 43

March 10,400 2,690 4,900 1,520 43

April 39,900 4,330 14,500 7,260 43

May 61,800 10,000 38,700 11,100 43

June 74,300 10,000 45,100 13,800 43

July 47,500 9,820 22,800 8,190 43

August 16,900 6,140 9,930 2,380 43

September 16,600 4,740 7,020 2,060 43

Annual 19,200 7,420 14,000 3,180 43
244 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

12323240 Blacktail Creek at Butte, Mont.

Site Number 218

LOCATION.--Lat 45°54'38", long 112°31'38" (NAD 27), in SW1⁄4NE1⁄4SE1⁄4 sec.24, T.3 N., R.8 W., Silver Bow County, Hydrologic Unit 17010201, on left bank, 

70 feet upstream from George Street culvert in Butte, and 0.2 mi upstream from Silver Bow Creek.

DRAINAGE AREA.--95.4 mi2.

PERIOD OF RECORD.--October 1988 to current year (2002).

REVISED RECORDS.--WDR-MT.-93-1: 1989-92 (M).

GAGE.--Water-stage recorder. Altitude of gage is 5,430 ft (NGVD 29).

REMARKS.--Slight regulation by Basin Creek Reservoir. Diversions for irrigation of about 1,400 acres upstream from station. U.S. Geological Survey satellite 

telemeter at station.

Magnitude and probability of annual low flow

based on 13 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 6.4 5.1 4.5 4.0 -- --

3 6.6 5.2 4.6 4.1 -- --

7 6.9 5.5 4.8 4.3 -- --

14 7.2 5.8 5.1 4.6 -- --

30 7.7 6.2 5.5 5.0 -- --

60 8.2 6.7 6.1 5.5 -- --

90 8.6 7.1 6.5 6.0 -- --

120 8.9 7.4 6.8 6.3 -- --

183 9.2 7.7 7.0 6.5 -- --

Magnitude and probability of seasonal low flow from

March-June based on 14 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 7.7 6.2 5.6 5.2 -- --

3 7.9 6.4 5.8 5.4 -- --

7 8.4 6.9 6.3 5.8 -- --

14 9.3 7.5 6.8 6.2 -- --

30 12 8.5 7.4 6.6 -- --

Magnitude and probability of seasonal low flow from

November-February based on 13 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 7.5 6.4 5.9 5.5 -- --

3 7.6 6.4 5.9 5.6 -- --

7 7.8 6.6 6.1 5.7 -- --

14 8.0 6.7 6.2 5.9 -- --

30 8.2 7.0 6.5 6.1 -- --

Duration of daily mean flows based on 14 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

4.8 5.6 6.0 6.5 7.5 8.5 9.6 11

40% 30% 20% 15% 10% 5% 2% 1%

12 14 16 18 22 30 42 55

Magnitude and probability of annual high flow

based on 14 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 44 87 134 221 -- --

3 34 63 91 142 -- --

7 28 48 67 100 -- --

15 23 38 52 75 -- --

30 21 33 43 59 -- --

60 19 29 38 51 -- --

90 18 27 34 44 -- --

Magnitude and probability of seasonal low flow from

July-October based on 13 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 6.5 5.1 4.5 4.1 -- --

3 6.8 5.3 4.6 4.2 -- --

7 7.1 5.5 4.8 4.3 -- --

14 7.4 5.8 5.1 4.6 -- --

30 8.0 6.3 5.5 5.0 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 15 7.0 10 2.3 14

November 14 6.9 10 2.2 14

December 13 7.1 9.2 1.8 14

January 13 7.0 9.0 2.0 14

February 26 6.3 11 5.7 14

March 30 7.4 14 6.1 14

April 29 9.4 17 6.0 14

May 42 7.3 20 10 14

June 62 8.1 21 15 14

July 26 6.2 12 6.5 14

August 18 5.3 9.9 3.6 14

September 14 6.0 9.2 2.5 14

Annual 20 8.2 13 4.3 14
Statistical Summaries of Streamflow 245

12323250 Silver Bow Creek below Blacktail Creek, at Butte, Mont.

Site Number 219

LOCATION.--Lat 45°59'47", long 112°33'45" (NAD 27), in SW1⁄4SE1⁄4NW1⁄4 sec.23, T.3 N., R.8 W., Silver Bow County, Hydrologic Unit 17010201, on right 

bank at Interstate 90 overpass in Butte, 0.8 mi upstream from Whiskey Gulch, 1.3 mi downstream from Blacktail Creek, and at river mile 20.2.

DRAINAGE AREA.--103 mi2.

PERIOD OF RECORD.--October 1983 to current year (2002).

REVISED RECORDS.--WDR-MT-92-1: 1984-90 (M). WDR-MT-98-1: Drainage area. WDR-MT-2000-1: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 5,409.47 ft (NGVD 29). October 1983 to Sept. 14, 1997, water-stage recorder 150 ft upstream at datum 1.40 ft 

higher. Sept. 15, 1997, to Dec. 3, 1997, no gage in operation due to channel reconstruction during U.S. Environmental Protection Agency Superfund cleanup 

operations. Dec. 3, 1997, to Aug. 16, 1999, water-stage recorder 0.8 mi downstream at different datum. Aug. 16, 1999, to May 10, 2000, water-stage recorder 

2.1 mi downstream at different datum.

REMARKS.--Flow slightly regulated by Silver Bow County sewage treatment plant. U.S. Geological Survey satellite telemeter at station.

Magnitude and probability of annual low flow

based on 18 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 15 12 11 9.7 -- --

3 15 13 12 11 -- --

7 15 13 12 11 -- --

14 16 14 13 12 -- --

30 16 14 13 12 -- --

60 17 15 14 13 -- --

90 17 16 15 14 -- --

120 18 16 15 15 -- --

183 19 17 16 15 -- --

Magnitude and probability of seasonal low flow from

March-June based on 19 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 17 14 12 11 -- --

3 17 15 13 12 -- --

7 18 15 14 13 -- --

14 19 16 14 13 -- --

30 22 17 15 14 -- --

Magnitude and probability of seasonal low flow from

November-February based on 18 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 16 14 13 12 -- --

3 16 14 13 13 -- --

7 16 14 14 13 -- --

14 17 15 14 13 -- --

30 17 15 14 13 -- --

Duration of daily mean flows based on 19 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

11 12 13 15 17 18 19 21

40% 30% 20% 15% 10% 5% 2% 1%

22 24 29 31 34 44 59 66

Magnitude and probability of annual high flow

based on 19 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 80 127 165 219 -- --

3 60 91 114 147 -- --

7 48 68 84 104 -- --

15 40 55 66 82 -- --

30 35 47 55 67 -- --

60 31 42 49 59 -- --

90 30 39 45 53 -- --

Magnitude and probability of seasonal low flow from

July-October based on 18 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 15 13 12 11 -- --

3 16 13 12 11 -- --

7 16 14 12 11 -- --

14 17 14 13 12 -- --

30 18 15 14 13 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 27 16 20 3.2 19

November 26 16 20 2.9 19

December 24 15 19 2.8 19

January 26 13 18 3.2 19

February 38 14 20 5.9 19

March 41 17 25 6.0 19

April 42 15 28 7.8 19

May 54 13 30 11 19

June 75 16 30 15 19

July 37 13 22 7.5 19

August 29 14 21 4.8 19

September 26 14 19 3.5 19

Annual 31 16 23 4.7 19
246 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

12323500 German Gulch Creek near Ramsay, Mont.

Site Number 220

LOCATION.--Lat 46°00'57", long 112°47'30" (NAD 27), in SE1⁄4NW1⁄4 sec.13, T.3 N., R.10 W., Silver Bow County, on left bank 0.5 mi upstream from mouth 

and 5.2 mi west of Ramsay.

DRAINAGE AREA.--40.6 mi2.

PERIOD OF RECORD.--14 years. April 1955 to September 1969 (discontinued). Monthly discharge for some periods, published in WSP 1736.

REVISED RECORDS.--WSP 1736: 1955-56. WSP 1933: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 5,200 ft (NGVD 29, by barometer). Prior to July 13, 1956, nonrecording gage at site 300 ft upstream from 

mouth at different datum.

REMARKS.--Minor diversions for irrigation upstream from station.

Magnitude and probability of annual low flow

based on 13 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 3.8 3.2 2.9 2.7 -- --

3 4.2 3.6 3.2 3.0 -- --

7 4.7 4.1 3.7 3.5 -- --

14 5.0 4.4 4.1 3.9 -- --

30 5.5 4.8 4.4 4.2 -- --

60 6.2 5.2 4.7 4.3 -- --

90 6.6 5.5 5.0 4.5 -- --

120 7.0 5.9 5.3 4.9 -- --

183 7.7 6.6 6.2 5.8 -- --

Magnitude and probability of seasonal low flow from

March-June based on 14 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 4.9 4.3 4.0 3.8 -- --

3 5.1 4.5 4.2 4.0 -- --

7 5.4 4.8 4.5 4.2 -- --

14 5.8 5.0 4.7 4.4 -- --

30 7.2 5.8 5.2 4.8 -- --

Magnitude and probability of seasonal low flow from

November-February based on 14 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 3.8 3.2 3.0 2.7 -- --

3 4.2 3.6 3.3 3.0 -- --

7 4.8 4.1 3.8 3.5 -- --

14 5.3 4.6 4.2 4.0 -- --

30 5.7 4.9 4.5 4.2 -- --

Duration of daily mean flows based on 14 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

4.0 4.2 4.7 5.4 6.4 7.3 8.4 9.9

40% 30% 20% 15% 10% 5% 2% 1%

12 16 29 41 57 87 129 163

Magnitude and probability of annual high flow

based on 14 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 152 209 245 287 -- --

3 141 187 213 243 -- --

7 129 169 191 214 -- --

15 117 152 171 191 -- --

30 96 128 147 170 -- --

60 71 94 108 124 -- --

90 56 73 83 95 -- --

Magnitude and probability of seasonal low flow from

July-October based on 14 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 7.6 6.5 6.0 5.7 -- --

3 7.6 6.6 6.1 5.8 -- --

7 7.7 6.7 6.3 5.9 -- --

14 7.9 6.9 6.4 6.1 -- --

30 8.3 7.1 6.6 6.3 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 13 6.8 9.2 2.0 14

November 11 5.7 8.0 1.4 14

December 10 4.7 7.3 1.6 14

January 8.4 4.2 6.3 1.3 14

February 11 3.9 6.6 1.9 14

March 15 4.9 8.1 2.8 14

April 39 9.1 18 8.0 15

May 108 40 66 22 15

June 154 27 77 36 15

July 45 9.3 24 11 15

August 16 6.3 11 3.0 15

September 16 7.4 9.6 2.1 15

Annual 30 13 21 5.2 14
Statistical Summaries of Streamflow 247

12323600 Silver Bow Creek at Opportunity, Mont.

Site Number 221

LOCATION.--Lat 46°06'28", long 112°48'17" (NAD 27), in SE1⁄4SW1⁄4SE1⁄4 sec.11, T.4 N., R.10 W., Deer Lodge County, Hydrologic Unit 17010201, on left bank 

200 ft downstream from Stuart Street bridge, 0.5 mi east of Opportunity, and 1.0 mi upstream from Mill Creek.

DRAINAGE AREA.--363 mi2. Prior to water year 2001, drainage area published as 284 mi2.

PERIOD OF RECORD.--July 1988 to current year (2002). Prior to October 1991, seasonal records only.

REVISED RECORDS.--WDR MT-2001-01: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 4,912.37 ft (NGVD 29).

REMARKS.--Numerous diversions upstream from station. U.S. Geological Survey satellite telemeter at station.

Magnitude and probability of annual low flow

based on 11 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 19 15 13 11 -- --

3 20 15 13 12 -- --

7 21 16 14 12 -- --

14 22 16 14 12 -- --

30 24 17 15 13 -- --

60 27 20 17 15 -- --

90 29 22 19 17 -- --

120 31 24 21 19 -- --

183 34 27 23 21 -- --

Magnitude and probability of seasonal low flow from

March-June based on 14 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 32 24 19 16 -- --

3 33 24 20 17 -- --

7 36 27 22 18 -- --

14 40 28 23 19 -- --

30 47 33 27 22 -- --

Magnitude and probability of seasonal low flow from

November-February based on 11 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 26 20 17 15 -- --

3 27 21 19 17 -- --

7 28 22 20 18 -- --

14 29 23 21 19 -- --

30 30 24 21 19 -- --

Duration of daily mean flows based on 11 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

13 16 18 22 27 32 36 41

40% 30% 20% 15% 10% 5% 2% 1%

46 56 66 80 95 127 198 289

Magnitude and probability of annual high flow

based on 11 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 165 379 643 -- -- --

3 144 328 550 -- -- --

7 130 271 418 -- -- --

15 118 222 317 -- -- --

30 102 180 249 -- -- --

60 89 152 207 -- -- --

90 81 133 175 -- -- --

Magnitude and probability of seasonal low flow from

July-October based on 14 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 19 15 13 11 -- --

3 20 15 13 12 -- --

7 21 16 14 12 -- --

14 22 17 14 13 -- --

30 24 18 15 13 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 56 26 38 8.9 14

November 50 26 38 8.0 12

December 49 23 35 10 11

January 69 22 37 14 11

February 184 22 54 47 11

March 87 32 54 17 14

April 120 41 65 23 14

May 260 31 97 61 14

June 281 24 101 76 14

July 107 18 48 30 15

August 70 14 31 16 15

September 60 21 33 12 15

Annual 99 30 55 24 11
248 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

12323750 Silver Bow Creek at Warm Springs, Mont.

Site Number 222

LOCATION.--Lat 46°10'50", long 112°46'46" (NAD 27), in SW1⁄4SE1⁄4SW1⁄4 sec.18, T.5 N., R.9 W., Deer Lodge County, Hydrologic Unit 17010201, on left bank 

1.0 mi upstream from confluence with Warm Springs Creek, 1.1 mi upstream from county highway bridge, and 0.5 mi east of Warm Springs.

DRAINAGE AREA.--473 mi2; area at site used prior to May 24, 1994, 483 mi2.

PERIOD OF RECORD.--March 1972 to September 1979, April 1993 to current year (2002).

GAGE.--Water-stage recorder. Altitude of gage is 4,800.31 ft (NGVD 29). Prior to May 24, 1994, gage located at sites 0.8 mi downstream at different datum.

REMARKS.--Flow is regulated by dam on tailing ponds about 0.2 mi upstream from gage. Diversions for irrigation of about 4,650 acres upstream from station. 

U.S. Geological Survey satellite telemeter at station.

Magnitude and probability of annual low flow

based on 14 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 32 20 16 13 -- --

3 34 21 17 14 -- --

7 38 24 19 15 -- --

14 41 25 20 16 -- --

30 45 28 21 17 -- --

60 50 30 23 18 -- --

90 53 33 26 21 -- --

120 57 37 29 24 -- --

183 62 41 33 27 -- --

Magnitude and probability of seasonal low flow from

March-June based on 16 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 58 41 34 29 -- --

3 61 44 37 32 -- --

7 69 49 41 35 -- --

14 81 55 45 37 -- --

30 94 64 51 43 -- --

Magnitude and probability of seasonal low flow from

November-February based on 16 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 43 31 26 23 -- --

3 45 33 28 25 -- --

7 49 36 30 26 -- --

14 52 38 32 28 -- --

30 59 42 35 29 -- --

Duration of daily mean flows based on 16 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

18 21 27 34 47 58 69 82

40% 30% 20% 15% 10% 5% 2% 1%

96 120 160 187 240 340 514 652

Magnitude and probability of annual high flow

based on 16 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 370 668 898 1,220 -- --

3 346 606 802 1,070 -- --

7 325 559 730 958 -- --

15 291 498 652 862 -- --

30 267 459 603 803 -- --

60 220 377 498 669 -- --

90 191 320 417 551 -- --

Magnitude and probability of seasonal low flow from

July-October based on 16 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 33 21 16 13 -- --

3 35 22 17 14 -- --

7 39 24 19 15 -- --

14 43 26 20 16 -- --

30 47 28 21 17 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 193 28 73 41 16

November 161 32 80 34 16

December 156 31 74 30 16

January 152 37 78 33 16

February 130 37 82 30 16

March 207 46 110 46 16

April 281 54 131 59 18

May 586 70 246 144 18

June 770 57 279 189 18

July 356 29 121 82 18

August 201 17 69 47 18

September 137 20 64 36 18

Annual 228 43 117 57 16
Statistical Summaries of Streamflow 249

12323770 Warm Springs Creek at Warm Springs, Mont.

Site Number 223

LOCATION.--Lat 46°10'50", long 112°47'04" (NAD 27), in SW1⁄4SW1⁄4SW1⁄4 sec.18, T.5 N., R.9 W., Deer Lodge County, Hydrologic Unit 17010201, on left 

bank at county road bridge 0.2 mi southeast of Warm Springs Post Office, and at river mile 0.9.

DRAINAGE AREA.--163 mi2.

PERIOD OF RECORD.--October 1983 to current year (2002). October 1983 to June 26, 2002, at site 200 ft upstream.

GAGE.--Water-stage recorder. Altitude of gage is 4,810 ft (NGVD 29).

REMARKS.--Numerous diversions upstream from station. U.S. Geological Survey satellite telemeter at station.

Magnitude and probability of annual low flow

based on 18 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 4.1 0.44 0.07 0.00 -- --

3 4.8 .54 .12 .03 -- --

7 5.4 .98 .33 .12 -- --

14 6.7 1.4 .55 .23 -- --

30 8.2 2.0 .87 .40 -- --

60 12 3.8 1.9 .99 -- --

90 17 6.3 3.4 2.0 -- --

120 24 11 6.5 4.2 -- --

183 29 15 10 7.4 -- --

Magnitude and probability of seasonal low flow from

March-June based on 19 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 17 4.8 2.0 0.87 -- --

3 18 5.4 2.4 1.1 -- --

7 21 7.6 3.8 2.0 -- --

14 25 11 6.1 3.6 -- --

30 33 19 13 9.3 -- --

Magnitude and probability of seasonal low flow from

November-February based on 18 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 14 7.3 5.0 3.7 -- --

3 16 8.2 5.6 4.1 -- --

7 20 9.9 6.6 4.5 -- --

14 23 11 7.5 5.1 -- --

30 27 14 9.1 6.1 -- --

Duration of daily mean flows based on 19 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

0.69 1.6 3.6 6.7 17 25 31 38

40% 30% 20% 15% 10% 5% 2% 1%

45 55 66 81 101 160 241 300

Magnitude and probability of annual high flow

based on 19 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 206 342 434 548 -- --

3 190 322 415 533 -- --

7 174 297 385 500 -- --

15 155 271 354 461 -- --

30 136 231 296 378 -- --

60 106 178 229 297 -- --

90 87 142 182 235 -- --

Magnitude and probability of seasonal low flow from

July-October based on 18 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 4.8 0.50 0.12 0.00 -- --

3 5.6 .62 .14 .06 -- --

7 5.8 1.0 .42 .18 -- --

14 7.1 1.5 .65 .26 -- --

30 8.7 2.1 .92 .45 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 95 11 45 24 19

November 84 13 45 21 19

December 78 5.9 34 18 19

January 82 4.2 37 21 19

February 63 4.5 36 17 19

March 54 19 36 12 19

April 63 13 42 14 19

May 196 19 83 44 19

June 362 7.1 136 100 19

July 170 .41 54 53 19

August 125 .46 25 33 19

September 82 2.6 32 23 19

Annual 108 17 50 24 19
250 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

12323800 Clark Fork near Galen, Mont.

Site Number 224

LOCATION.--Lat 46°12'30", long 112°45'59" (NAD 27), in NE1⁄4NE1⁄4NE1⁄4 sec.7, T.5 N., R.9 W., Deer Lodge County, Hydrologic Unit 17010201, on right bank 

at upstream side of bridge on county road, 2.6 mi downstream from Silver Bow Creek and Warm Springs Creek, 2 mi south of Galen, and at river mile 482.7.

DRAINAGE AREA.--651 mi2, area at site used prior to Oct. 1, 1994, 793 mi2.

PERIOD OF RECORD.--July 1988 to current year (2002).

GAGE.--Water-stage recorder. Altitude of gage is 4,749.24 ft (NGVD 29).

REMARKS.--Some regulation by settling ponds on Silver Bow Creek near Warm Springs. Numerous diversions upstream from station. U.S. Geological Survey 

satellite telemeter at station.

Magnitude and probability of annual low flow

based on 13 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 30 18 13 11 -- --

3 31 18 14 11 -- --

7 33 19 15 12 -- --

14 37 21 16 13 -- --

30 43 25 19 15 -- --

60 53 33 26 21 -- --

90 60 39 32 27 -- --

120 68 47 39 33 -- --

183 75 53 44 38 -- --

Magnitude and probability of seasonal low flow from

March-June based on 14 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 68 43 32 24 -- --

3 71 46 34 26 -- --

7 80 52 40 30 -- --

14 93 61 46 35 -- --

30 110 75 58 46 -- --

Magnitude and probability of seasonal low flow from

November-February based on 14 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 51 37 32 28 -- --

3 53 39 33 29 -- --

7 57 42 36 32 -- --

14 64 47 40 36 -- --

30 70 51 43 38 -- --

Duration of daily mean flows based on 14 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

14 18 29 39 56 70 81 91

40% 30% 20% 15% 10% 5% 2% 1%

110 132 172 201 283 390 609 818

Magnitude and probability of annual high flow

based on 14 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 479 816 1,050 1,340 -- --

3 454 783 1,010 1,300 -- --

7 401 708 933 1,230 -- --

15 372 658 872 1,160 -- --

30 334 586 773 1,030 -- --

60 273 468 615 819 -- --

90 232 385 501 664 -- --

Magnitude and probability of seasonal low flow from

July-October based on 14 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 31 18 14 11 -- --

3 32 19 14 11 -- --

7 33 20 15 12 -- --

14 38 22 16 13 -- --

30 44 26 20 16 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 170 41 92 40 14

November 158 51 97 32 14

December 132 41 84 30 14

January 169 42 85 35 14

February 174 44 93 36 14

March 167 77 114 32 14

April 257 80 137 53 14

May 668 69 253 156 14

June 974 51 360 262 14

July 381 21 143 117 15

August 233 10 73 68 15

September 184 20 72 47 15

Annual 288 60 135 63 14
Statistical Summaries of Streamflow 251

12324100 Racetrack Creek below Granite Creek, near Anaconda, Mont.

Site Number 225

LOCATION.--Lat 46°16'44", long 112°55'07" (NAD 27), near center of NW1⁄4NE1⁄4 sec.13, T.6 N., R.11 W., Powell County, Deer Lodge National Forest, on right 

bank 30 ft upstream from bridge, 1.6 mi downstream from Granite Creek, 9.5 mi upstream from mouth, and 10.3 mi north of Anaconda.

DRAINAGE AREA.--39.5 mi2. 

PERIOD OF RECORD.--16 years. April 1914 to September 1917 (gage heights only, published as "near Anaconda"). July 1957 to September 1973 (discontinued). 

Records for July 1911 to November 1912 at site 3 mi upstream, published as "near Anaconda" not equivalent owing to inflow.

REVISED RECORDS.--WSP 1316: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 5,420 ft (NGVD 29, from topographic map). Prior to September 1917, nonrecording gage at site 0.3 mi 

downstream at different datum.

REMARKS.--Some regulation by Racetrack and Fisher Lakes.

Magnitude and probability of annual low flow

based on 15 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 12 9.9 8.8 7.9 -- --

3 14 12 10 9.4 -- --

7 17 14 13 12 -- --

14 17 16 15 15 -- --

30 18 17 16 16 -- --

60 20 18 17 17 -- --

90 21 19 18 17 -- --

120 22 19 18 18 -- --

183 27 24 22 22 -- --

Magnitude and probability of seasonal low flow from

March-June based on 16 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 17 15 13 12 -- --

3 17 16 15 14 -- --

7 18 16 16 15 -- --

14 18 17 16 15 -- --

30 19 17 16 16 -- --

Magnitude and probability of seasonal low flow from

November-February based on 16 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 13 10 8.9 8.0 -- --

3 14 12 10 9.5 -- --

7 17 14 13 12 -- --

14 18 16 15 15 -- --

30 19 17 16 16 -- --

Duration of daily mean flows based on 16 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

14 16 17 18 20 22 26 31

40% 30% 20% 15% 10% 5% 2% 1%

40 58 85 107 142 221 283 344

Magnitude and probability of annual high flow

based on 16 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 324 413 463 516 -- --

3 303 386 430 477 -- --

7 285 358 395 432 -- --

15 262 326 357 387 -- --

30 235 290 316 340 -- --

60 179 220 241 262 -- --

90 149 180 196 212 -- --

Magnitude and probability of seasonal low flow from

July-October based on 15 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 25 21 19 17 -- --

3 26 22 21 20 -- --

7 27 23 22 21 -- --

14 28 24 23 22 -- --

30 31 26 25 24 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 56 25 33 9.5 16

November 37 18 25 5.5 16

December 30 16 22 3.9 16

January 26 16 20 3.0 16

February 24 17 20 2.1 16

March 26 16 20 2.9 16

April 42 18 26 7.3 16

May 168 67 101 30 16

June 340 94 221 68 16

July 167 60 105 30 16

August 98 34 69 18 17

September 78 28 43 12 17

Annual 79 37 59 11 16
252 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

12324200 Clark Fork at Deer Lodge, Mont.

Site Number 226

LOCATION.--Lat 46°23'52", long 112°44'31" (NAD 27), in SW1⁄4SW1⁄4SW1⁄4 sec.33, T.8 N., R.9 W., Powell County, Hydrologic Unit 17010201, on left bank 

35 ft upstream from Milwaukee Avenue Bridge in Deer Lodge, 0.05 mi upstream from Taylor Creek, 0.24 mi downstream from Tin Cup Joe Creek, and at river 

mile 461.2.

DRAINAGE AREA.--995 mi2, area at site used prior to Oct. 1, 1994, 1,005 mi2. Area used October 1994 to September 2000, 916 mi2.

PERIOD OF RECORD.--October 1978 to current year (2002).

GAGE.--Water-stage recorder. Altitude of gage is 4,502.24 ft (NGVD 29).

REMARKS.--Diversions upstream from station for irrigation of about 31,000 acres. Some regulation by settling ponds on Silver Bow Creek near Warm Springs. 

U.S. Geological Survey satellite telemeter at station.

Magnitude and probability of annual low flow

based on 23 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 50 30 23 19 -- --

3 52 31 24 19 -- --

7 55 32 24 20 -- --

14 60 34 26 20 -- --

30 69 38 28 22 -- --

60 99 57 42 32 -- --

90 124 74 56 44 -- --

120 148 93 72 58 -- --

183 177 124 102 86 -- --

Magnitude and probability of seasonal low flow from

March-June based on 24 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 138 73 49 35 -- --

3 144 76 52 36 -- --

7 161 87 59 41 -- --

14 191 109 75 52 -- --

30 242 151 105 72 -- --

Magnitude and probability of seasonal low flow from

November-February based on 23 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 135 106 93 83 -- --

3 143 114 101 91 -- --

7 157 127 113 103 -- --

14 175 142 127 116 -- --

30 196 157 140 127 -- --

Duration of daily mean flows based on 24 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

27 32 54 93 139 169 199 229

40% 30% 20% 15% 10% 5% 2% 1%

259 299 345 368 436 602 945 1,170

Magnitude and probability of annual high flow

based on 24 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 758 1,320 1,750 2,380 -- --

3 698 1,210 1,600 2,170 -- --

7 618 1,070 1,440 1,980 -- --

15 547 950 1,290 1,790 -- --

30 485 812 1,080 1,480 -- --

60 415 664 864 1,160 -- --

90 373 571 723 940 -- --

Magnitude and probability of seasonal low flow from

July-October based on 23 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 52 30 23 19 -- --

3 53 31 24 19 -- --

7 57 33 25 20 -- --

14 62 35 26 21 -- --

30 70 38 29 22 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 420 115 243 84 24

November 384 156 252 69 24

December 353 122 224 61 24

January 342 140 224 62 24

February 481 137 247 83 24

March 387 185 267 61 24

April 422 161 281 76 24

May 971 80 392 231 24

June 1,450 58 499 372 24

July 592 30 222 173 24

August 337 28 107 80 24

September 315 58 176 81 24

Annual 464 130 261 96 24
Statistical Summaries of Streamflow 253

12324590 Little Blackfoot River near Garrison, Mont.

Site Number 227

LOCATION.--Lat 46°31'11", long 112°47'33" (NAD 27), in NE1⁄4NW1⁄4SE1⁄4 sec.24, T.9 N., R.10 W., Powell County, Hydrologic Unit 17010201, on right bank 

20 ft upstream from bridge on frontage road, 0.7 mi southeast of Garrison, and at river mile 0.5.

DRAINAGE AREA.--407 mi2.

PERIOD OF RECORD.--October 1972 to current year (2002).

GAGE.--Water-stage recorder. Altitude of gage is 4,343.97 ft (NGVD 29). Prior to Oct. 1, 1992, at site 3.5 mi upstream at different datum.

REMARKS.--A few minor irrigation holding reservoirs in upper reaches of drainage. Diversions for irrigation of about 11,000 acres upstream from station. U.S. 

Geological Survey satellite telemeter at station.

Magnitude and probability of annual low flow

based on 29 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 25 15 11 8.2 5.9 --

3 26 16 11 8.6 6.1 --

7 29 17 12 9.2 6.5 --

14 32 19 14 10 7.0 --

30 38 23 17 13 9.4 --

60 44 28 22 17 13 --

90 49 34 27 23 19 --

120 54 38 32 28 23 --

183 57 42 36 32 29 --

Magnitude and probability of seasonal low flow from

March-June based on 30 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 53 39 33 29 25 --

3 56 41 35 31 27 --

7 61 46 40 35 31 --

14 72 55 48 43 38 --

30 101 71 59 51 43 --

Magnitude and probability of seasonal low flow from

November-February based on 30 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 33 25 22 20 18 --

3 34 28 25 24 22 --

7 37 31 30 29 28 --

14 41 35 33 32 31 --

30 47 39 37 35 33 --

Duration of daily mean flows based on 30 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

15 19 30 37 47 56 64 78

40% 30% 20% 15% 10% 5% 2% 1%

93 122 185 257 371 569 874 1,090

Magnitude and probability of annual high flow

based on 30 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 877 1,740 2,450 3,470 4,330 --

3 774 1,460 2,000 2,750 3,340 --

7 674 1,240 1,660 2,250 2,710 --

15 594 1,060 1,410 1,860 2,210 --

30 513 896 1,160 1,500 1,750 --

60 406 687 883 1,130 1,320 --

90 338 555 703 888 1,020 --

Magnitude and probability of seasonal low flow from

July-October based on 29 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 28 15 11 8.4 6.0 --

3 29 16 12 8.9 6.2 --

7 32 17 13 9.4 6.6 --

14 35 19 14 10 7.2 --

30 40 24 17 14 9.6 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 129 35 72 26 30

November 122 40 71 21 30

December 199 33 64 34 30

January 135 36 61 25 30

February 262 36 84 55 30

March 271 55 117 51 30

April 486 89 224 105 30

May 1,460 77 489 323 30

June 1,800 60 389 336 30

July 410 24 136 92 30

August 190 12 62 42 30

September 184 20 57 34 30

Annual 322 58 152 69 30
254 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

12324680 Clark Fork at Goldcreek, Mont.

Site Number 228

LOCATION.--Lat 46°35'26", long 112°55'40" (NAD 27), in SE1⁄4NW1⁄4SW1⁄4 sec.25, T.10 N., R.11 W., Powell County, Hydrologic Unit 17010201, on right bank 

at county road bridge, 0.4 mi north of the town of Goldcreek, 1.1 mi downstream from Gold Creek, and at river mile 434.7.

DRAINAGE AREA.--1,760 mi2.

PERIOD OF RECORD.--October 1977 to current year (2002).

GAGE.--Water-stage recorder. Altitude of gage is 4,172.80 ft (NGVD 29). June 13 to Oct. 21, 1982, nonrecording gage at site 350 ft downstream at same datum.

REMARKS.-- Some regulation by settling ponds on Silver Bow Creek near Warm Springs. Diversion for irrigation of about 40,100 acres upstream from station. 

U.S. Geological Survey satellite telemeter at station.

Magnitude and probability of annual low flow

based on 24 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 139 91 71 57 -- --

3 145 93 72 58 -- --

7 153 97 75 60 -- --

14 165 103 79 63 -- --

30 185 115 88 69 -- --

60 221 139 106 83 -- --

90 254 166 130 105 -- --

120 286 194 156 129 -- --

183 311 227 191 165 -- --

Magnitude and probability of seasonal low flow from

March-June based on 25 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 271 177 137 109 83 --

3 290 191 147 116 86 --

7 327 216 164 127 92 --

14 372 247 188 145 105 --

30 455 310 239 186 136 --

Magnitude and probability of seasonal low flow from

November-February based on 25 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 191 151 133 119 105 --

3 206 166 146 132 116 --

7 230 189 170 155 140 --

14 264 215 193 177 160 --

30 300 240 213 192 171 --

Duration of daily mean flows based on 25 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

78 95 142 192 246 296 341 389

40% 30% 20% 15% 10% 5% 2% 1%

456 522 672 753 982 1,420 2,100 2,690

Magnitude and probability of annual high flow

based on 25 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 2,040 3,760 5,100 6,980 8,490 --

3 1,860 3,270 4,300 5,680 6,750 --

7 1,590 2,730 3,580 4,730 5,630 --

15 1,380 2,370 3,100 4,110 4,900 --

30 1,220 2,030 2,620 3,410 4,020 --

60 1,010 1,610 2,040 2,630 3,090 --

90 881 1,350 1,690 2,130 2,480 --

Magnitude and probability of seasonal low flow from

July-October based on 24 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 144 92 72 58 -- --

3 147 94 73 59 -- --

7 154 98 76 60 -- --

14 166 105 80 64 -- --

30 187 117 89 69 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 699 198 400 136 25

November 651 244 404 111 25

December 622 193 350 102 25

January 596 199 348 108 25

February 860 208 420 174 25

March 721 306 488 133 25

April 918 360 601 183 25

May 2,910 198 1,040 621 25

June 3,000 138 1,120 776 25

July 1,200 86 494 348 25

August 646 68 236 143 25

September 707 100 306 151 25

Annual 860 243 518 191 25
Statistical Summaries of Streamflow 255

12325500 Flint Creek near Southern Cross, Mont.

Site Number 229

LOCATION.--Lat 46°13'59", long 113°17'56" (NAD 27), in SE1⁄4NW1⁄4 sec.36, T.6 N., R.14 W., Granite County, Hydrologic Unit 17010202, on right wing wall 

of weir, 0.5 mi downstream from power plant, 2.0 mi downstream from Georgetown Dam, 3.5 mi northwest of Southern Cross, 6.8 mi south of Philipsburg, 

and at river mile 36.8.

DRAINAGE AREA.--52.6 mi2.

PERIOD OF RECORD.--October 1940 to September 1998, August 2000 to current year (2002, seasonal records only).

REVISED RECORDS.--WSP 1216: 1942(M). WSP 1246: Drainage area.

GAGE.--Water-stage recorder and sharp-crested, contracted, rectangular weir. Altitude of gage is 5,630 ft (NGVD 29). Prior to June 3, 1982, nonrecording gage 

at same site and datum. Prior to Nov. 27, 1973, gage at same site and datum 0.20 ft higher.

REMARKS.--Flow regulated by Georgetown Lake (station number 12325000). Flow may be augmented by interbasin diversion from Silver Lake to Georgetown 

Lake or reduced by pumping from Georgetown Lake to Silver Lake. U.S. Geological Survey satellite telemeter at station.

Magnitude and probability of annual low flow

based on 58 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 9.0 4.6 3.1 2.2 0.90 0.00

3 9.6 4.9 3.4 2.5 1.7 1.3

7 9.9 5.2 3.6 2.7 1.9 1.5

14 10 5.3 3.7 2.7 1.9 1.5

30 11 5.6 3.9 2.9 2.0 1.5

60 12 6.1 4.2 3.1 2.1 1.6

90 13 7.4 5.4 4.0 2.9 2.3

120 17 9.3 6.5 4.8 3.2 2.5

183 21 14 11 9.1 7.1 6.0

Magnitude and probability of seasonal low flow from

March-June based on 60 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 13 6.7 4.5 3.2 2.2 1.6

3 14 7.1 4.9 3.5 2.3 1.8

7 14 7.3 5.0 3.6 2.4 1.8

14 15 7.6 5.2 3.7 2.4 1.8

30 16 8.3 5.6 3.9 2.6 1.9

Magnitude and probability of seasonal low flow from

November-February based on 59 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 13 6.3 4.1 2.7 1.0 0.00

3 14 6.8 4.5 3.1 2.0 1.5

7 14 7.1 4.8 3.4 2.3 1.7

14 14 7.4 5.0 3.5 2.4 1.8

30 15 7.6 5.2 3.7 2.4 1.8

Duration of daily mean flows based on 60 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

3.3 4.1 4.9 7.0 13 19 24 27

40% 30% 20% 15% 10% 5% 2% 1%

29 31 36 42 51 77 113 128

Magnitude and probability of annual high flow

based on 60 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 79 130 166 213 249 285

3 77 126 161 207 243 279

7 72 118 151 196 231 268

15 65 106 137 181 216 254

30 58 93 119 157 188 221

60 50 74 93 120 142 166

90 45 64 78 99 116 135

Magnitude and probability of seasonal low flow from

July-October based on 58 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 18 9.4 6.3 4.3 2.8 2.0

3 18 9.6 6.4 4.4 2.8 2.0

7 19 9.8 6.5 4.5 2.8 2.0

14 19 10 6.9 4.8 3.1 2.2

30 24 15 11 7.9 5.4 4.0

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 59 3.9 26 12 60

November 62 3.9 22 13 60

December 50 2.7 20 11 60

January 38 2.9 19 10 60

February 54 3.4 20 12 60

March 80 4.1 22 17 60

April 121 1.6 25 23 60

May 106 7.8 32 21 60

June 142 26 57 33 60

July 131 26 46 21 60

August 78 22 33 9.0 61

September 74 13 31 9.2 61

Annual 58 13 30 11 60
256 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

12329500 Flint Creek at Maxville, Mont.

Site Number 230

LOCATION.--Lat 46°27'50", long 113°14'20" (NAD 27), in NE1⁄4SW1⁄4NW1⁄4 sec.9, T.8 N., R.13 W., Granite County, Hydrologic Unit 17010202, on right bank 

0.4 mi west of Maxville and 1.0 mi upstream from Boulder Creek.

DRAINAGE AREA.--208 mi2.

PERIOD OF RECORD.--August 1941 to current year (2002). April 1939 to September 1941 at site 0.5 mi upstream; records not equivalent owing to diversions.

REVISED RECORDS.--WSP 1216: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 4,828.38 ft (NGVD 29).

REMARKS.--Some regulation by Georgetown Lake (station number 12325000). Diversions for irrigation of about 8,200 acres upstream from station. During 

irrigation season, flow is supplemented by water from East Fork Rock Creek which is diverted in sec.5, T.4 N., R.14 W., 500 ft downstream from Rock Creek 

Dam, through a canal into Trout Creek, and then into Flint Creek. U.S. Geological Survey satellite telemeter at station.

Magnitude and probability of annual low flow

based on 60 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 31 24 21 19 16 15

3 33 26 22 20 17 16

7 36 28 25 22 20 18

14 40 32 28 25 23 21

30 45 36 32 29 25 23

60 51 40 35 31 27 24

90 55 43 38 33 29 26

120 60 47 41 37 32 29

183 69 55 48 43 38 34

Magnitude and probability of seasonal low flow from

March-June based on 61 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 44 33 29 25 22 20

3 47 35 30 26 23 21

7 51 39 34 30 26 24

14 56 43 38 34 30 27

30 67 51 45 40 35 33

Magnitude and probability of seasonal low flow from

November-February based on 61 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 33 25 22 19 17 15

3 35 27 23 20 18 16

7 38 29 26 23 20 19

14 42 33 28 25 22 21

30 47 37 32 29 25 23

Duration of daily mean flows based on 61 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

26 30 36 44 54 63 72 82

40% 30% 20% 15% 10% 5% 2% 1%

91 108 127 147 175 232 320 374

Magnitude and probability of annual high flow

based on 61 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 348 520 638 790 905 1,020

3 296 438 539 673 777 884

7 251 364 442 547 628 712

15 219 318 388 481 553 629

30 190 277 341 428 498 572

60 162 230 279 343 394 447

90 147 206 247 302 345 389

Magnitude and probability of seasonal low flow from

July-October based on 60 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 61 44 36 31 25 21

3 62 46 38 32 26 23

7 65 48 41 35 29 25

14 70 52 44 38 31 27

30 78 57 48 40 33 28

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 148 50 85 22 61

November 121 41 73 19 61

December 120 28 60 18 61

January 88 27 54 16 61

February 141 27 62 23 61

March 186 34 76 27 61

April 310 49 106 55 61

May 353 51 137 62 61

June 455 71 188 90 61

July 324 48 127 56 61

August 217 30 107 32 61

September 151 34 92 30 62

Annual 165 53 97 27 61
Statistical Summaries of Streamflow 257

12330000 Boulder Creek at Maxville, Mont.

Site Number 231

LOCATION.--Lat 46°28'20", 1ong 113°13'59" (NAD 27), in SE1⁄4NE1⁄4SW1⁄4 sec.4, T.8 N., R.13 W., Granite County, Hydrologic Unit 17010202, on right bank 

0.2 mi upstream from mouth and 0.7 mi north of Maxville.

DRAINAGE AREA.--71.3 mi2.

PERIOD OF RECORD.--April 1939 to current year (2002). Monthly discharge only for some periods, published in WSP 1316. 

GAGE.--Water-stage recorder. Altitude of gage is 4,750 ft (NGVD 29). Apr. 15, 1939, to July 7, 1941, nonrecording gage at site 75 ft upstream at different datum. 

July 8-20, 1941, nonrecording gage at site 175 ft upstream at datum 1.03 ft higher.

REMARKS.--Diversions upstream for irrigation of about 240 acres near the station. U.S. Geological Survey satellite telemeter at station. 

Magnitude and probability of annual low flow

based on 62 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 8.2 5.6 4.6 3.8 3.1 2.7

3 8.5 5.9 4.8 4.1 3.4 2.9

7 9.1 6.3 5.2 4.3 3.6 3.1

14 10 7.1 5.8 4.8 3.9 3.4

30 12 8.6 7.0 5.8 4.7 4.0

60 15 11 9.1 7.7 6.3 5.4

90 17 13 11 9.5 8.0 7.1

120 18 14 12 11 9.3 8.4

183 19 15 13 12 11 9.9

Magnitude and probability of seasonal low flow from

March-June based on 63 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 15 12 9.9 8.5 7.1 6.2

3 16 12 10 8.7 7.3 6.3

7 16 13 11 9.5 8.0 7.1

14 17 14 12 11 9.6 8.8

30 18 15 13 12 11 10

Magnitude and probability of seasonal low flow from

November-February based on 63 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 12 9.3 7.9 6.8 5.6 4.9

3 13 9.9 8.4 7.3 6.1 5.4

7 14 11 9.7 8.5 7.4 6.6

14 16 12 11 9.6 8.3 7.5

30 17 14 12 11 9.4 8.5

Duration of daily mean flows based on 63 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

6.0 7.3 10 12 16 18 20 22

40% 30% 20% 15% 10% 5% 2% 1%

26 32 50 72 112 185 274 347

Magnitude and probability of annual high flow

based on 63 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 316 481 602 767 898 1,040

3 294 428 513 617 692 763

7 263 377 446 525 579 629

15 230 329 388 456 503 546

30 196 276 322 375 410 442

60 148 205 238 276 301 325

90 115 157 181 209 228 245

Magnitude and probability of seasonal low flow from

July-October based on 63 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 8.9 5.7 4.6 3.9 3.2 2.8

3 9.1 5.9 4.9 4.2 3.4 3.0

7 9.6 6.4 5.2 4.4 3.6 3.2

14 10 7.1 5.8 4.9 4.0 3.6

30 12 8.7 7.1 5.9 4.8 4.3

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 51 3.6 23 9.4 63

November 45 12 23 6.4 63

December 39 11 21 5.0 63

January 32 8.5 19 4.2 63

February 30 10 18 3.8 63

March 29 12 18 3.5 63

April 56 10 29 10 63

May 261 55 115 45 64

June 376 35 174 83 64

July 244 13 59 38 64

August 68 8.1 21 11 64

September 54 6.6 18 9.4 64

Annual 82 20 45 13 63
258 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

12331500 Flint Creek near Drummond, Mont.

Site Number 232

LOCATION.--Lat 46°37'44", long 113°09'02" (NAD 27), in NE1⁄4NW1⁄4NE1⁄4 sec.18, T.10 N., R.12 W., Granite County, Hydrologic Unit 17010202, on left bank 

10 ft downstream from county bridge, 2.0 mi upstream from mouth, and 2.7 mi south of Drummond.

DRAINAGE AREA.--490 mi2.

PERIOD OF RECORD.--August 1990 to September 2002 (discontinued).

GAGE.--Water-stage recorder. Altitude of gage is 4,017.27 ft (NGVD 29). June 1948 to September 1949 at same site with different datum.

REMARKS.--Some regulation by Georgetown Lake (station number 12325000). Diversions for irrigation of about 25,000 acres of which 1,000 acres lie 

downstream from station. During irrigation season, flow is supplemented by water from East Fork Rock Creek which is diverted in sec.5, T.4 N., R.14 W., 

500 ft downstream from Rock Creek Dam, through a canal into Trout Creek, and then into Flint Creek.

Magnitude and probability of annual low flow

based on 11 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 11 3.0 1.4 0.74 -- --

3 13 3.7 1.8 1.0 -- --

7 16 5.2 2.8 1.6 -- --

14 20 7.4 4.2 2.6 -- --

30 27 11 6.7 4.3 -- --

60 39 17 10 6.7 -- --

90 53 26 17 12 -- --

120 65 33 21 14 -- --

183 79 48 36 27 -- --

Magnitude and probability of seasonal low flow from

March-June based on 13 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 30 6.1 2.2 0.90 -- --

3 38 9.9 4.3 2.0 -- --

7 51 16 7.5 3.7 -- --

14 65 22 11 5.3 -- --

30 84 36 21 13 -- --

Magnitude and probability of seasonal low flow from

November-February based on 13 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 58 45 40 36 -- --

3 61 48 42 38 -- --

7 66 52 46 42 -- --

14 71 56 50 45 -- --

30 78 61 54 49 -- --

Duration of daily mean flows based on 13 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

4.2 6.0 15 32 56 73 87 102

40% 30% 20% 15% 10% 5% 2% 1%

117 135 167 183 227 323 527 723

Magnitude and probability of annual high flow

based on 13 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 422 700 897 1,150 -- --

3 364 604 782 1,020 -- --

7 312 519 679 908 -- --

15 268 457 615 858 -- --

30 232 387 517 716 -- --

60 195 310 406 551 -- --

90 176 273 352 469 -- --

Magnitude and probability of seasonal low flow from

July-October based on 12 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 16 4.4 2.2 1.2 -- --

3 17 4.8 2.3 1.2 -- --

7 19 6.2 3.2 1.9 -- --

14 23 8.3 4.6 2.8 -- --

30 31 12 7.2 4.6 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 186 81 133 35 13

November 168 91 128 28 13

December 144 64 100 26 13

January 156 57 97 29 13

February 232 57 115 46 13

March 256 80 131 46 13

April 372 87 170 98 13

May 459 14 159 134 13

June 955 15 280 259 14

July 412 13 130 131 14

August 167 6.7 49 49 15

September 196 18 72 50 15

Annual 234 60 125 54 13
Statistical Summaries of Streamflow 259

12331600 Clark Fork at Drummond, Mont.

Site Number 233

LOCATION.--Lat 46°39'45", long 113°08'57" (NAD 27), in SE1⁄4NW1⁄4SE1⁄4 sec.31, T.11 N., R.12 W., Granite County, Hydrologic Unit 17010201, at bridge on 

old U.S. Highway l0A, 0.4 mi southwest of Drummond, 0.9 mi downstream from Flint Creek, and at mile 417.0. 

DRAINAGE AREA.--2,378 mi2. 

PERIOD OF RECORD.--March 1967 to June 1968, October 1970, June 1971 to September 1972 (occasional discharge measurements and gage heights only). 

October 1972 to Sept. 30, 1983 (discontinued). 

GAGE.--Nonrecording gage read once or twice daily and crest-stage gage since Aug. 12, 1977. Altitude of gage is 3,937.95 ft (NGVD 29). 

REMARKS.--Some regulation by settling ponds on Silver Bow Creek near Anaconda and by Georgetown Lake (station number 12325000) on Flint Creek. 

Diversions for irrigation of about 86,500 acres upstream from station. 

Magnitude and probability of annual low flow

based on 10 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 175 93 66 50 -- --

3 203 115 84 64 -- --

7 222 124 88 65 -- --

14 243 136 96 70 -- --

30 284 165 118 87 -- --

60 363 210 149 108 -- --

90 428 253 187 143 -- --

120 485 304 232 183 -- --

183 527 359 291 243 -- --

Magnitude and probability of seasonal low flow from

March-June based on 11 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 411 203 126 80 -- --

3 436 259 187 140 -- --

7 510 326 244 185 -- --

14 590 405 317 252 -- --

30 668 458 361 290 -- --

Magnitude and probability of seasonal low flow from

November-February based on 10 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 284 199 165 142 -- --

3 311 221 186 162 -- --

7 345 249 212 187 -- --

14 389 305 275 256 -- --

30 448 383 362 351 -- --

Duration of daily mean flows based on 11 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

101 136 226 304 412 496 583 672

40% 30% 20% 15% 10% 5% 2% 1%

761 924 1,090 1,340 1,790 2,700 3,850 4,400

Magnitude and probability of annual high flow

based on 11 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 3,580 6,880 9,300 -- -- --

3 3,230 5,820 7,590 -- -- --

7 2,860 5,000 6,440 -- -- --

15 2,490 4,270 5,460 -- -- --

30 2,230 3,720 4,690 -- -- --

60 1,840 2,980 3,730 -- -- --

90 1,600 2,480 3,060 -- -- --

Magnitude and probability of seasonal low flow from

July-October based on 10 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 215 111 80 61 -- --

3 219 119 86 66 -- --

7 228 129 91 67 -- --

14 248 141 100 74 -- --

30 291 167 121 91 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 1,180 384 710 243 11

November 1,090 492 681 181 11

December 1,190 416 621 224 11

January 980 399 581 190 11

February 1,140 415 652 216 11

March 1,060 567 751 173 11

April 1,800 509 920 352 11

May 3,460 330 1,820 1,070 11

June 4,570 280 1,980 1,370 11

July 2,490 118 950 701 11

August 1,240 84 430 336 11

September 961 262 567 238 11

Annual 1,390 400 889 320 11
260 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

12331900 Clark Fork near Clinton, Mont.

Site Number 234

LOCATION.--Lat 46°43'05", long 113°35'17" (NAD 27), in SE1⁄4SW1⁄4SE1⁄4 sec.10, T11 N., R.16 W., Missoula County, Hydrologic Unit 17010201, on 

downstream side of county road bridge, 4.5 mi upstream from Rock Creek, 6.5 mi southeast of Clinton, and at river mile 386.6. 

DRAINAGE AREA.--2,629 mi2. 

PERIOD OF RECORD.--June 1979 to September 1990, October 1991 to September 1994 (discontinued). 

REVISED RECORDS.--WDR MT-81-2: Drainage area. 

GAGE.--Nonrecording gage and crest-stage gage. Altitude of gage is 3,580 ft (NGVD 29, from topographic map). 

REMARKS.--Some regulation by settling ponds on Silver Bow Creek near Anaconda and by Georgetown Lake (station number 12325000) on Flint Creek. 

Diversions for irrigation of about 88,400 acres upstream from station. 

Magnitude and probability of annual low flow

based on 12 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 226 143 110 86 -- --

3 235 149 113 89 -- --

7 248 156 117 91 -- --

14 271 167 125 96 -- --

30 310 190 142 109 -- --

60 374 231 172 133 -- --

90 444 284 219 173 -- --

120 502 328 254 201 -- --

183 554 386 312 257 -- --

Magnitude and probability of seasonal low flow from

March-June based on 14 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 402 256 199 160 -- --

3 418 266 206 165 -- --

7 446 285 219 174 -- --

14 531 340 256 197 -- --

30 662 441 329 248 -- --

Magnitude and probability of seasonal low flow from

November-February based on 14 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 307 248 221 201 -- --

3 332 269 239 216 -- --

7 375 302 267 239 -- --

14 414 337 302 275 -- --

30 463 375 335 305 -- --

Duration of daily mean flows based on 14 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

123 149 212 285 385 454 524 615

40% 30% 20% 15% 10% 5% 2% 1%

709 838 1,010 1,090 1,370 1,990 3,030 3,880

Magnitude and probability of annual high flow

based on 14 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 2,690 5,250 7,530 11,200 -- --

3 2,450 4,640 6,530 9,490 -- --

7 2,080 3,770 5,230 7,510 -- --

15 1,760 3,180 4,400 6,290 -- --

30 1,520 2,660 3,630 5,120 -- --

60 1,360 2,230 2,910 3,910 -- --

90 1,220 1,910 2,420 3,130 -- --

Magnitude and probability of seasonal low flow from

July-October based on 13 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 244 144 112 87 -- --

3 251 151 114 89 -- --

7 260 159 119 92 -- --

14 277 169 127 96 -- --

30 314 192 143 111 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 1,070 392 680 229 14

November 1,040 428 659 184 14

December 935 323 572 166 14

January 1,190 306 567 229 14

February 1,320 309 641 303 14

March 1,170 490 746 211 14

April 1,330 492 919 282 14

May 3,620 257 1,420 903 14

June 3,910 206 1,450 1,130 15

July 1,800 162 705 504 15

August 948 111 369 213 15

September 1,070 184 528 259 15

Annual 1,240 376 777 284 14
Statistical Summaries of Streamflow 261

12332000 Middle Fork Rock Creek near Philipsburg, Mont.

Site Number 235

LOCATION.--Lat 46°11'03", long 113°30'05" (NAD 27), in SW1⁄4NW1⁄4SE1⁄4 sec.17, T.5 N., R.15 W., Granite County, Hydrologic Unit 17010202, on left bank 

40 ft downstream from bridge on county highway, 1.2 mi upstream from East Fork, 3.4 mi upstream from West Fork, and 15 mi southwest of Philipsburg.

DRAINAGE AREA.--123 mi2.

PERIOD OF RECORD.--September 1937 to current year (2002). Monthly discharges only January to March 1938, published in WSP 1316.

GAGE.--Water-stage recorder. Altitude of gage is 5,444.08 ft (NGVD 29). Prior to Oct. 25, 1990, gage located at several sites 0.8 to 1.0 mi downstream. See 

WSP 1736 or 1933 for history of changes prior to Oct. 1, 1955.

REMARKS.--A few small diversions for irrigation upstream from station. U.S. Geological Survey satellite telemeter at station.

Magnitude and probability of annual low flow

based on 64 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 17 11 9.3 7.7 6.1 5.2

3 18 14 12 10 8.4 7.5

7 21 17 15 13 12 11

14 24 19 18 16 15 14

30 27 23 21 20 18 18

60 30 26 24 23 22 21

90 32 28 26 25 24 23

120 34 30 28 27 26 26

183 39 34 32 31 30 30

Magnitude and probability of seasonal low flow from

March-June based on 65 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 24 17 14 12 9.5 8.2

3 26 19 16 14 11 10

7 28 22 19 17 15 14

14 30 25 22 21 19 18

30 34 28 26 24 23 22

Magnitude and probability of seasonal low flow from

November-February based on 64 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 17 12 9.7 8.0 6.4 5.4

3 19 14 12 10 8.9 7.9

7 22 17 15 13 12 11

14 24 20 18 17 15 14

30 27 23 21 20 19 18

Duration of daily mean flows based on 65 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

16 19 24 27 33 38 43 49

40% 30% 20% 15% 10% 5% 2% 1%

61 83 151 223 333 509 743 939

Magnitude and probability of annual high flow

based on 65 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 825 1,120 1,290 1,480 1,600 1,700

3 773 1,060 1,220 1,400 1,520 1,630

7 704 970 1,120 1,300 1,410 1,520

15 625 857 994 1,150 1,250 1,350

30 542 728 836 956 1,040 1,110

60 423 556 630 710 763 809

90 333 433 487 546 584 618

Magnitude and probability of seasonal low flow from

July-October based on 64 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 38 32 29 26 24 22

3 39 33 29 27 24 23

7 40 34 30 28 25 23

14 42 35 31 29 26 24

30 44 36 33 30 27 25

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 202 27 50 22 65

November 104 26 43 12 65

December 64 24 36 9.4 65

January 61 22 32 7.8 65

February 60 16 33 8.6 65

March 71 23 36 9.6 65

April 190 28 75 35 65

May 650 137 334 123 65

June 914 141 482 198 65

July 496 49 179 84 65

August 141 26 71 22 65

September 98 30 52 13 65

Annual 183 62 119 31 65
262 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

12334510 Rock Creek near Clinton, Mont.

Site Number 236

LOCATION.--Lat 46°43'21", long 113°40'56" (NAD 27), in NW1⁄4NE1⁄4SW1⁄4 sec.12, T.11 N., R.17 W., Missoula County, Hydrologic Unit 17010202, on left 

bank 100 ft downstream from private road bridge, 0.2 mi upstream from mouth, and 3.7 mi southeast of Clinton.

DRAINAGE AREA.--885 mi2.

PERIOD OF RECORD.--October 1972 to current year (2002).

GAGE.--Water-stage recorder. Altitude of gage is 3,519.46 ft (NGVD 29).

REMARKS.--Some regulation by East Fork Rock Creek Reservoir (station number 12332500). During irrigation season water is diverted from East Fork Rock 

Creek in sec.5, T.4 N., R.14 W., 500 ft downstream from Rock Creek Dam, through a canal into Trout Creek, and then into Flint Creek. Diversions for irrigation 

of about 16,100 acres. U.S. Geological Survey satellite telemeter at station.

Magnitude and probability of annual low flow

based on 29 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 88 62 51 43 34 --

3 95 69 57 49 40 --

7 109 85 74 65 57 --

14 127 102 91 82 73 --

30 150 125 113 104 94 --

60 164 136 123 113 103 --

90 172 142 131 123 116 --

120 184 153 141 133 126 --

183 208 171 156 145 134 --

Magnitude and probability of seasonal low flow from

March-June based on 30 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 164 135 123 115 106 --

3 172 143 131 122 114 --

7 179 151 140 132 124 --

14 192 163 152 144 137 --

30 223 181 165 154 144 --

Magnitude and probability of seasonal low flow from

November-February based on 29 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 89 63 52 43 35 --

3 96 70 58 50 41 --

7 110 85 74 66 57 --

14 128 103 92 83 75 --

30 153 126 114 105 96 --

Duration of daily mean flows based on 30 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

94 104 131 146 175 205 236 267

40% 30% 20% 15% 10% 5% 2% 1%

326 407 667 913 1,280 2,030 2,960 3,720

Magnitude and probability of annual high flow

based on 30 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 2,820 4,150 4,930 5,810 6,400 --

3 2,670 3,930 4,680 5,520 6,090 --

7 2,450 3,640 4,370 5,220 5,800 --

15 2,160 3,250 3,940 4,800 5,400 --

30 1,880 2,840 3,470 4,250 4,820 --

60 1,520 2,260 2,740 3,340 3,770 --

90 1,240 1,810 2,190 2,650 2,980 --

Magnitude and probability of seasonal low flow from

July-October based on 29 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 198 151 130 114 97 --

3 202 155 133 116 99 --

7 206 158 136 119 102 --

14 212 163 140 123 105 --

30 223 173 150 133 116 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 474 157 253 65 30

November 430 149 227 58 30

December 460 119 197 79 30

January 329 106 185 59 30

February 426 109 192 62 30

March 428 158 243 73 30

April 1,020 236 500 212 30

May 3,680 544 1,460 682 30

June 3,760 407 1,720 936 30

July 1,910 267 683 366 30

August 635 156 313 116 30

September 389 148 262 71 30

Annual 966 258 521 188 30
Statistical Summaries of Streamflow 263

12334550 Clark Fork at Turah Bridge, near Bonner, Mont.

Site Number 237

LOCATION.--Lat 46°49'34", long 113°48'48" (NAD 27), in SW1⁄4NW1⁄4SW1⁄4 sec.1, T.12 N., R.18 W., Missoula County, Hydrologic Unit 17010201, on left bank 

0.8 mi southeast of Turah, 4 mi southeast of Bonner, and at river mile 370.2. 

DRAINAGE AREA.--3,641 mi2.

PERIOD OF RECORD.--October 1985 to current year (2002). Water-discharge records for the period March 1985 to September 1985 are available in files of the 

USGS Montana District Office.

GAGE.--Water-stage recorder. Altitude of gage is 3,320 ft (NGVD 29, from topographic map). Prior to May 9, 1986, non-recording gage at same site at datum 

2.00 ft higher.

REMARKS.--Some regulation by settling ponds on Silver Bow Creek near Anaconda and by Georgetown Lake (station number 12325000) on Flint Creek. 

Diversions for irrigation of about 100,000 acres upstream from station. U.S. Geological Survey satellite telemeter at station.

Magnitude and probability of annual low flow

based on 17 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 332 252 216 189 -- --

3 352 274 238 211 -- --

7 398 303 259 227 -- --

14 444 322 269 231 -- --

30 496 357 296 252 -- --

60 570 415 345 294 -- --

90 630 484 416 364 -- --

120 686 550 487 438 -- --

183 712 571 508 460 -- --

Magnitude and probability of seasonal low flow from

March-June based on 18 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 650 527 478 443 -- --

3 672 547 496 461 -- --

7 701 583 538 507 -- --

14 792 668 624 595 -- --

30 944 754 679 627 -- --

Magnitude and probability of seasonal low flow from

November-February based on 17 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 388 288 241 206 -- --

3 414 321 278 245 -- --

7 482 392 349 316 -- --

14 557 469 427 394 -- --

30 635 538 492 455 -- --

Duration of daily mean flows based on 18 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

274 314 406 498 605 695 790 895

40% 30% 20% 15% 10% 5% 2% 1%

1,000 1,120 1,470 1,870 2,380 3,220 4,860 6,330

Magnitude and probability of annual high flow

based on 18 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 4,380 6,870 8,490 10,500 -- --

3 4,130 6,360 7,750 9,390 -- --

7 3,780 5,870 7,240 8,900 -- --

15 3,330 5,240 6,570 8,300 -- --

30 2,970 4,660 5,860 7,440 -- --

60 2,490 3,740 4,620 5,790 -- --

90 2,120 3,150 3,890 4,890 -- --

Magnitude and probability of seasonal low flow from

July-October based on 17 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 420 294 247 216 -- --

3 427 298 250 218 -- --

7 441 305 261 231 -- --

14 457 326 273 236 -- --

30 505 359 298 256 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 1,290 592 871 218 18

November 1,170 616 857 169 18

December 1,230 492 739 183 18

January 1,150 474 724 175 18

February 2,120 472 846 400 18

March 1,660 712 1,030 303 18

April 3,070 828 1,490 600 18

May 6,340 915 2,480 1,250 18

June 7,090 639 2,770 1,680 18

July 2,920 435 1,230 690 18

August 1,420 271 639 300 18

September 1,420 356 706 299 18

Annual 2,220 686 1,200 413 18
264 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

12335000 Blackfoot River near Helmville, Mont.

Site Number 238

LOCATION.--Lat 46°56'10", long 112°56'30" (NAD 27), in NW1⁄4SW1⁄4 sec.25, T.14 N., R.11 W., Powell County, on right bank 50 ft downstream from highway 

bridge, 2 mi downstream from Arrastre Creek, and 5 mi northeast of Helmville.

DRAINAGE AREA.--481 mi2.

PERIOD OF RECORD.--13 years (1940-53). 

GAGE.--Water-stage recorder. Altitude of gage is 4,301.29 ft (NGVD 29, U.S. Army Corps of Engineers bench mark). 

REMARKS.--Flow includes natural overflow channel on left bank, but does not include unnamed diversions past station. Diversions upstream from station for 

irrigation of about 2,000 acres, of which 500 acres lie downstream from station.

Magnitude and probability of annual low flow

based on 12 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 96 77 66 57 -- --

3 98 79 68 60 -- --

7 102 82 72 63 -- --

14 105 86 75 66 -- --

30 112 91 80 70 -- --

60 123 100 86 75 -- --

90 128 105 92 82 -- --

120 133 112 101 93 -- --

183 144 122 111 102 -- --

Magnitude and probability of seasonal low flow from

March-June based on 13 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 101 86 80 75 -- --

3 104 88 81 76 -- --

7 108 92 84 79 -- --

14 112 96 88 82 -- --

30 116 98 92 88 -- --

Magnitude and probability of seasonal low flow from

November-February based on 12 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 105 83 70 60 -- --

3 106 85 73 62 -- --

7 109 87 75 65 -- --

14 111 90 78 68 -- --

30 116 94 82 72 -- --

Duration of daily mean flows based on 13 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

68 74 93 100 116 131 149 168

40% 30% 20% 15% 10% 5% 2% 1%

186 247 416 598 937 1,420 2,120 2,630

Magnitude and probability of annual high flow

based on 13 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 2,110 3,350 4,080 4,860 -- --

3 2,030 3,210 3,880 4,610 -- --

7 1,890 2,900 3,440 3,970 -- --

15 1,730 2,620 3,060 3,480 -- --

30 1,510 2,230 2,550 2,820 -- --

60 1,210 1,730 1,940 2,100 -- --

90 959 1,360 1,530 1,660 -- --

Magnitude and probability of seasonal low flow from

July-October based on 13 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 152 126 112 101 -- --

3 153 127 113 102 -- --

7 154 127 114 103 -- --

14 156 129 115 105 -- --

30 159 132 119 108 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 212 111 159 33 14

November 191 104 149 29 13

December 180 84 132 28 13

January 156 63 119 25 13

February 168 85 121 26 13

March 212 96 125 31 13

April 604 92 271 168 13

May 1,860 84 970 550 13

June 2,730 267 1,260 703 13

July 904 135 500 243 13

August 338 108 235 73 13

September 236 115 173 35 13

Annual 512 116 352 124 13
Statistical Summaries of Streamflow 265

12335500 Nevada Creek above reservoir, near Helmville, Mont.

Site Number 239

LOCATION.--Lat 46°46'42", long 112°46'00" (NAD 27), in SW1⁄4NW1⁄4SW1⁄4 sec.20, T.12 N., R.9 W., Powell County, Hydrologic Unit 17010203, on right bank 

0.7 mi upstream from Nevada Lake, 1.1 mi downstream from Gallagher Creek, 11 mi southeast of Helmville, and at river mile 34.5.

DRAINAGE AREA.--116 mi2.

PERIOD OF RECORD.--April 1939 to current year (2002). Prior to October 2001, published as "near Finn."

GAGE.--Water-stage recorder. Altitude of gage is 4,640 ft (NGVD 29). Prior to Apr. 30, 1942, nonrecording gage at site 0.1 mi downstream at different datum. 

Apr. 30, 1942, to July 26, 1953, water-stage recorder at site 0.2 mi downstream at different datum. July 26, 1953, to Nov. 6, 1978, water-stage recorder at site 

0.8 mi upstream at different datum.

REMARKS.--Diversions for irrigation of about 2,900 acres upstream from station. U.S. Geological Survey satellite telemeter at station.

Magnitude and probability of annual low flow

based on 62 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 4.3 3.0 2.5 2.2 1.8 1.6

3 4.6 3.3 2.8 2.4 2.0 1.8

7 5.2 3.7 3.1 2.6 2.1 1.9

14 6.0 4.2 3.5 3.0 2.5 2.2

30 6.9 4.9 4.1 3.6 3.0 2.7

60 8.2 5.8 4.8 4.1 3.5 3.1

90 9.4 6.8 5.7 4.9 4.2 3.8

120 11 7.8 6.6 5.8 4.9 4.4

183 11 8.4 7.2 6.3 5.4 4.8

Magnitude and probability of seasonal low flow from

March-June based on 63 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 8.3 6.0 5.1 4.6 4.0 3.7

3 8.8 6.3 5.4 4.8 4.2 3.8

7 9.7 6.9 5.8 5.1 4.4 4.0

14 12 8.5 7.4 6.6 6.0 5.6

30 21 13 11 8.9 7.3 6.4

Magnitude and probability of seasonal low flow from

November-February based on 63 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 5.0 3.4 2.7 2.3 1.9 1.6

3 5.5 3.8 3.0 2.6 2.1 1.8

7 6.3 4.3 3.4 2.8 2.3 2.0

14 7.2 4.9 4.0 3.3 2.7 2.3

30 8.3 5.8 4.7 3.9 3.2 2.7

Duration of daily mean flows based on 63 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

3.6 4.2 5.1 6.3 8.6 11 13 16

40% 30% 20% 15% 10% 5% 2% 1%

20 26 44 61 89 147 237 311

Magnitude and probability of annual high flow

based on 63 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 338 566 721 914 1,050 1,190

3 286 466 577 706 792 870

7 228 361 439 524 579 627

15 177 281 341 407 448 484

30 138 221 272 331 369 404

60 107 166 202 240 265 287

90 90 138 165 195 215 232

Magnitude and probability of seasonal low flow from

July-October based on 63 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 6.1 4.0 3.3 2.7 2.3 2.0

3 6.4 4.2 3.4 2.9 2.4 2.1

7 6.8 4.6 3.7 3.1 2.6 2.3

14 7.3 5.0 4.1 3.5 2.9 2.6

30 8.2 5.7 4.7 4.1 3.5 3.1

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 32 5.5 14 5.6 63

November 29 5.7 15 4.5 63

December 47 3.7 12 6.4 63

January 54 3.8 12 8.4 63

February 85 4.2 16 15 63

March 114 7.6 34 25 63

April 196 10 67 44 63

May 356 16 112 67 64

June 429 12 90 70 64

July 96 6.2 28 18 64

August 40 3.9 14 7.1 64

September 28 3.7 10 4.9 64

Annual 77 12 36 14 63
266 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

12338500 Blackfoot River near Ovando, Mont.

Site Number 240

LOCATION.--Lat 47°01'10", long 113°13'40" (NAD 27), in SE1⁄4NW1⁄4 sec.34, T.15 N., R.13 W., Powell County, on left bank 0.25 mi upstream from Monture 

Creek and 5 mi west of Ovando.

DRAINAGE AREA.--1,274 mi2.

PERIOD OF RECORD.--23 years (1940-63).

REVISED RECORDS.--WSP 1216: Drainage area. WSP 1246: 1941.

GAGE.--Water-stage recorder. Altitude of gage is 3,917.27 ft (NGVD 29, U.S. Army Corps of Engineers bench mark).

REMARKS.--Diversions for irrigation of about 15,000 acres upstream from station.

Magnitude and probability of annual low flow

based on 22 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 180 143 126 113 -- --

3 187 153 138 126 -- --

7 204 170 154 142 -- --

14 221 190 175 164 -- --

30 246 215 202 193 -- --

60 267 232 217 207 -- --

90 283 248 234 224 -- --

120 302 263 249 239 -- --

183 333 287 269 256 -- --

Magnitude and probability of seasonal low flow from

March-June based on 23 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 232 191 171 156 -- --

3 240 198 177 162 -- --

7 250 210 191 176 -- --

14 263 226 209 196 -- --

30 307 256 238 227 -- --

Magnitude and probability of seasonal low flow from

November-February based on 23 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 189 148 129 114 -- --

3 195 157 140 128 -- --

7 210 173 156 143 -- --

14 225 190 175 164 -- --

30 247 215 202 193 -- --

Duration of daily mean flows based on 23 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

178 194 211 238 285 321 357 408

40% 30% 20% 15% 10% 5% 2% 1%

487 643 1,060 1,460 2,260 3,530 4,970 5,790

Magnitude and probability of annual high flow

based on 23 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 5,230 7,290 8,330 9,350 -- --

3 5,090 7,040 7,980 8,870 -- --

7 4,760 6,490 7,290 8,010 -- --

15 4,310 5,880 6,590 7,200 -- --

30 3,810 4,980 5,420 5,740 -- --

60 3,000 3,830 4,120 4,320 -- --

90 2,360 3,020 3,270 3,450 -- --

Magnitude and probability of seasonal low flow from

July-October based on 22 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 351 298 275 258 -- --

3 353 300 276 259 -- --

7 357 302 279 261 -- --

14 361 306 283 265 -- --

30 367 312 288 271 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 785 259 395 116 23

November 760 255 377 109 23

December 573 225 324 86 23

January 364 194 274 54 23

February 514 216 287 70 23

March 671 227 341 103 23

April 1,710 222 721 397 23

May 4,370 426 2,460 1,050 23

June 6,600 738 3,000 1,330 23

July 2,170 371 1,140 527 23

August 837 254 526 148 23

September 585 262 397 82 24

Annual 1,230 315 855 239 23
Statistical Summaries of Streamflow 267

12339450 Clearwater River near Clearwater, Mont.

Site Number 241

LOCATION.--Lat 47°01'09", long 113°23'12" (NAD 27), in NW1⁄4NW1⁄4NW1⁄4 sec.33, T.15 N., R.14 W., Missoula County, Hydrologic Unit 17010203, Clearwater 

State Forest, on left bank 700 ft upstream from Blanchard Lake, 1.3 mi northwest of Clearwater, and at river mile 5.2. 

DRAINAGE AREA.--345 mi2. 

PERIOD OF RECORD.--October 1974 to September 1992 (discontinued). 

GAGE.--Water-stage recorder. Altitude of gage is 3,814.23 ft (NGVD 29). 

REMARKS.--A few minor diversions for irrigation upstream from station. During summer months Elbow Lake, 1.5 mi upstream, may be regulated for recreational 

purposes.

Magnitude and probability of annual low flow

based on 17 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 42 30 25 20 -- --

3 43 30 25 20 -- --

7 44 31 25 21 -- --

14 46 32 26 21 -- --

30 49 35 28 22 -- --

60 56 39 31 25 -- --

90 62 44 36 31 -- --

120 68 52 45 41 -- --

183 76 58 51 47 -- --

Magnitude and probability of seasonal low flow from

March-June based on 18 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 83 60 51 45 -- --

3 84 60 52 45 -- --

7 87 62 52 46 -- --

14 95 67 56 49 -- --

30 122 79 65 56 -- --

Magnitude and probability of seasonal low flow from

November-February based on 17 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 59 44 38 33 -- --

3 60 45 38 34 -- --

7 62 46 39 34 -- --

14 64 49 43 40 -- --

30 67 53 49 45 -- --

Duration of daily mean flows based on 18 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

25 29 39 49 61 73 85 102

40% 30% 20% 15% 10% 5% 2% 1%

141 211 461 644 858 1,150 1,480 1,880

Magnitude and probability of annual high flow

based on 18 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 1,530 2,020 2,360 2,810 -- --

3 1,490 1,970 2,300 2,730 -- --

7 1,390 1,840 2,150 2,540 -- --

15 1,210 1,610 1,890 2,240 -- --

30 1,080 1,440 1,690 2,000 -- --

60 942 1,240 1,420 1,640 -- --

90 800 1,040 1,180 1,330 -- --

Magnitude and probability of seasonal low flow from

July-October based on 17 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 42 31 25 20 -- --

3 43 31 25 21 -- --

7 44 31 25 21 -- --

14 46 33 26 21 -- --

30 51 35 28 22 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 164 25 80 35 18

November 197 44 101 50 18

December 288 54 105 63 18

January 192 44 92 40 18

February 149 49 86 30 18

March 602 55 160 124 18

April 1,230 165 648 303 18

May 1,610 552 1,010 372 18

June 1,390 219 701 311 18

July 499 75 233 129 18

August 154 27 76 36 18

September 180 18 65 38 18

Annual 424 162 281 81 18
268 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

12340000 Blackfoot River near Bonner, Mont.

Site Number 242

LOCATION.--Lat 46°53'59", long 113°45'20" (NAD 27), in SE1⁄4SE1⁄4NW1⁄4 sec.9, T.13 N., R.17 W., Missoula County, Hydrologic Unit 17010203, Lolo National 

Forest, on right bank 5.0 mi downstream from Union Creek, 5.6 mi northeast of Bonner, and at river mile 7.9.

DRAINAGE AREA.--2,290 mi2.

PERIOD OF RECORD.--July to November 1898, March 1899 to September 1901, May 1903 to January 1905, March to October 1905, October 1939 to current 

year (2002). Monthly discharge only for some periods, published in WSP 1316. Published as "at Bonner" 1898-99 and as "Big Blackfoot near Bonner" 

1903-05.

REVISED RECORDS.--WSP 1216: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 3,344.76 ft (NGVD 29). July 7, 1898, to June 30, 1901, and May 15, 1903, to Oct. 31, 1905, nonrecording gage 

at site 7 mi downstream at different datum. Oct. 4, 1939, to Sept. 30, 1955, nonrecording gage at site 1.3 mi downstream at datum 21.82 ft lower.

REMARKS.--Flow slightly regulated by Nevada Creek Reservoir (station number 12336500). Diversions for irrigation of about 20,000 acres upstream from 

station. U.S. Geological Survey satellite telemeter at station.

Magnitude and probability of annual low flow

based on 63 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 322 258 228 205 181 166

3 346 278 246 221 195 178

7 384 316 283 257 230 213

14 422 354 322 296 268 251

30 465 402 373 351 328 314

60 505 430 396 369 341 323

90 524 445 413 390 367 354

120 546 463 430 406 384 371

183 589 492 450 419 389 370

Magnitude and probability of seasonal low flow from

March-June based on 67 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 487 391 355 331 308 296

3 503 412 379 357 337 326

7 530 439 407 386 367 357

14 561 465 434 415 400 393

30 671 529 481 452 426 413

Magnitude and probability of seasonal low flow from

November-February based on 65 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 328 260 230 207 182 168

3 351 280 248 222 197 180

7 391 317 286 260 232 215

14 431 356 325 298 270 252

30 475 404 374 353 332 320

Duration of daily mean flows based on 66 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

298 339 396 437 519 594 669 744

40% 30% 20% 15% 10% 5% 2% 1%

932 1,240 2,140 3,020 4,160 6,030 8,420 10,200

Magnitude and probability of annual high flow

based on 66 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 8,580 12,000 13,800 15,800 17,000 18,100

3 8,340 11,500 13,200 14,900 15,900 16,700

7 7,780 10,700 12,100 13,600 14,500 15,200

15 6,960 9,550 10,900 12,200 13,000 13,600

30 6,150 8,410 9,550 10,700 11,300 11,900

60 5,040 6,730 7,560 8,350 8,790 9,150

90 4,150 5,520 6,170 6,790 7,140 7,420

Magnitude and probability of seasonal low flow from

July-October based on 66 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 566 459 408 368 326 300

3 571 465 414 374 332 306

7 579 472 420 379 337 311

14 589 478 425 384 341 314

30 604 489 436 394 351 324

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 1,550 370 654 192 68

November 1,480 369 650 183 67

December 1,560 332 611 228 67

January 1,070 348 556 146 67

February 1,670 359 601 229 66

March 2,350 435 778 335 67

April 4,730 463 2,030 1,040 67

May 9,800 1,100 4,880 1,930 68

June 10,500 1,160 4,820 2,240 68

July 4,110 533 1,780 787 68

August 1,460 365 821 236 68

September 1,100 363 662 163 68

Annual 2,480 558 1,580 460 66
Statistical Summaries of Streamflow 269

12340500 Clark Fork above Missoula, Mont.

Site Number 243

LOCATION.--Lat 46°52'38", long 113°55'53" (NAD 27), in NW1⁄4NW1⁄4NW1⁄4 sec.19, T.13 N., R.18 W., Missoula County, Hydrologic Unit 17010204, on right 

bank 0.2 mi downstream from county road bridge, 2.8 mi east of Missoula, 2.8 mi downstream from Milltown Dam, 3.0 mi downstream from Blackfoot River, 

and at river mile 361.6.

DRAINAGE AREA.--5,999 mi2.

PERIOD OF RECORD.--March 1929 to current year (2002). Monthly discharge only for some periods, published in WSP 1316.

REVISED RECORDS.--WSP 1042: 1936. WSP 1152: 1942. WSP 1246: 1929-30, 1935, drainage area. WSP 1316: 1932-33.

GAGE.--Water-stage recorder. Altitude of gage is 3,198.30 ft (NGVD 29, levels by U.S. Army Corps of Engineers). Prior to May 27, 1929, nonrecording gage.

REMARKS.--Diurnal fluctuation caused by powerplant at Milltown. Diversions for irrigation of about 120,000 acres upstream from station. U.S. Geological 

Survey satellite telemeter at station.

Magnitude and probability of annual low flow

based on 73 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 641 503 443 398 353 326

3 699 555 491 443 395 366

7 818 651 574 515 454 417

14 940 747 656 585 512 467

30 1,070 853 747 664 576 521

60 1,170 944 835 750 660 605

90 1,240 1,010 912 836 758 710

120 1,310 1,080 974 895 815 766

183 1,370 1,120 1,000 915 826 772

Magnitude and probability of seasonal low flow from

March-June based on 74 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1,200 959 853 775 697 650

3 1,260 1,020 916 840 763 716

7 1,320 1,100 1,010 949 888 852

14 1,430 1,210 1,130 1,070 1,020 995

30 1,690 1,370 1,250 1,170 1,100 1,060

Magnitude and probability of seasonal low flow from

November-February based on 73 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 657 511 451 409 367 343

3 714 557 493 448 404 377

7 843 663 588 534 480 448

14 984 783 695 631 566 526

30 1,130 922 828 757 684 640

Duration of daily mean flows based on 73 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

598 691 828 978 1,190 1,350 1,500 1,760

40% 30% 20% 15% 10% 5% 2% 1%

2,020 2,510 3,900 5,200 7,090 10,300 14,400 16,700

Magnitude and probability of annual high flow

based on 73 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 13,700 19,900 23,600 27,700 30,400 32,900

3 13,300 19,200 22,600 26,500 29,000 31,300

7 12,400 17,800 20,900 24,300 26,500 28,500

15 11,200 16,000 18,800 21,900 23,900 25,700

30 9,900 14,100 16,400 19,100 20,800 22,300

60 8,180 11,300 13,000 14,900 16,000 17,100

90 6,790 9,320 10,700 12,200 13,100 14,000

Magnitude and probability of seasonal low flow from

July-October based on 73 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1,040 739 606 509 412 356

3 1,080 800 673 579 485 429

7 1,120 838 710 616 521 465

14 1,160 869 741 646 550 493

30 1,220 919 783 682 580 519

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 2,990 854 1,560 422 73

November 2,850 882 1,560 366 73

December 3,320 874 1,420 437 73

January 2,550 606 1,330 386 73

February 3,430 674 1,480 519 73

March 4,120 1,040 1,860 606 74

April 10,100 1,190 3,710 1,800 74

May 17,200 2,000 7,900 3,170 74

June 19,300 2,120 8,290 4,060 74

July 8,760 868 3,180 1,570 74

August 3,450 627 1,490 536 74

September 2,870 653 1,400 446 74

Annual 5,070 1,340 2,940 888 73
270 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

12342500 West Fork Bitterroot River near Conner, Mont.

Site Number 244

LOCATION.--Lat 45°43'30", long 114°16'50" (NAD 27), in SE1⁄4NE1⁄4NW1⁄4 sec.26, T.1 S., R.22 W., Ravalli County, Hydrologic Unit 17010205, on right bank 

0.6 mi downstream from Painted Rocks Lake, 6.4 mi upstream from Nez Perce Creek, 16.1 mi southwest of Conner, and at river mile 19.2.

DRAINAGE AREA.--317 mi2.

PERIOD OF RECORD.--April 1941 to current year (2002).

REVISED RECORDS.--WSP 1246: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 4,581.36 ft (NGVD 29, U.S. Forest Service bench mark).

REMARKS.--Flow regulated by Painted Rocks Lake (station number 12342000). Diversions for irrigation of about 200 acres upstream from station. U.S. 

Geological Survey satellite telemeter at station.

Magnitude and probability of annual low flow

based on 60 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 39 12 5.0 2.2 0.76 0.35

3 43 14 6.1 2.8 .97 .44

7 50 17 7.4 3.2 1.1 .47

14 61 29 16 8.2 3.3 1.7

30 61 35 24 16 10 6.9

60 72 47 34 25 16 12

90 73 56 49 44 39 36

120 83 64 56 50 45 41

183 113 94 85 78 72 68

Magnitude and probability of seasonal low flow from

March-June based on 61 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 66 22 9.5 4.0 1.2 0.51

3 68 24 10 4.3 1.3 .54

7 74 27 12 5.0 1.5 .62

14 85 44 23 11 4.2 1.9

30 91 47 32 22 14 9.7

Magnitude and probability of seasonal low flow from

November-February based on 61 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 60 29 17 10 5.0 2.9

3 63 32 19 11 5.4 3.1

7 67 35 21 12 5.8 3.3

14 69 40 28 20 12 8.8

30 72 47 34 24 16 11

Duration of daily mean flows based on 61 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

11 23 48 55 69 86 103 120

40% 30% 20% 15% 10% 5% 2% 1%

154 226 336 438 661 1,130 1,800 2,110

Magnitude and probability of annual high flow

based on 61 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 1,830 2,640 3,070 3,510 3,770 3,990

3 1,750 2,510 2,920 3,320 3,560 3,760

7 1,590 2,310 2,690 3,070 3,310 3,500

15 1,400 2,030 2,370 2,720 2,930 3,110

30 1,200 1,730 2,020 2,320 2,500 2,650

60 864 1,270 1,500 1,760 1,930 2,090

90 675 965 1,130 1,320 1,450 1,560

Magnitude and probability of seasonal low flow from

July-October based on 61 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 87 42 21 9.6 3.3 1.4

3 87 62 53 45 35 31

7 89 65 54 46 38 33

14 90 67 55 47 40 34

30 95 73 64 57 51 47

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 484 52 157 101 61

November 416 53 113 67 61

December 270 28 91 49 61

January 243 21 84 37 61

February 215 6.8 80 33 61

March 278 7.8 94 49 61

April 719 8.6 203 158 61

May 2,010 118 807 452 62

June 1,960 118 917 468 62

July 633 127 267 104 62

August 439 84 200 87 62

September 384 62 178 75 62

Annual 457 120 268 83 61
Statistical Summaries of Streamflow 271

12343400 East Fork Bitterroot River near Conner, Mont.

Site Number 245

LOCATION.--Lat 45°53'00", long 114°03'53" (NAD 27), in NE1⁄4SW1⁄4NE1⁄4 sec.34, T.2 N., R.20 W., Ravalli County, Hydrologic Unit 17010205, on right bank 

10 ft downstream from private bridge, 4.3 mi southwest of Conner, and at river mile 6.1.

DRAINAGE AREA.--381 mi2.

PERIOD OF RECORD.--April 1956 to September 1972, October 2000 to current year (2002).

GAGE.--Water-stage recorder. Altitude of gage is 4,191.81 ft (NGVD 29).

REMARKS.--Diversions for irrigation of about 2,200 acres upstream from station. U.S. Geological Survey satellite telemeter at station.

Magnitude and probability of annual low flow

based on 16 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 40 32 29 26 -- --

3 47 37 32 28 -- --

7 60 48 40 34 -- --

14 69 55 47 39 -- --

30 77 64 55 47 -- --

60 84 70 62 55 -- --

90 86 74 67 62 -- --

120 91 78 72 67 -- --

183 98 85 78 73 -- --

Magnitude and probability of seasonal low flow from

March-June based on 18 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 65 52 48 44 -- --

3 71 59 55 52 -- --

7 80 66 61 57 -- --

14 84 69 64 60 -- --

30 95 79 74 70 -- --

Magnitude and probability of seasonal low flow from

November-February based on 18 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 41 33 29 26 -- --

3 48 38 33 29 -- --

7 60 48 41 35 -- --

14 69 56 47 39 -- --

30 78 65 56 48 -- --

Duration of daily mean flows based on 18 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

43 50 65 71 82 94 108 122

40% 30% 20% 15% 10% 5% 2% 1%

149 194 357 525 840 1,330 1,870 2,110

Magnitude and probability of annual high flow

based on 18 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 1,950 2,580 2,940 3,320 -- --

3 1,860 2,450 2,770 3,130 -- --

7 1,740 2,250 2,520 2,780 -- --

15 1,590 2,040 2,250 2,460 -- --

30 1,360 1,730 1,910 2,080 -- --

60 1,040 1,310 1,450 1,580 -- --

90 808 1,010 1,110 1,210 -- --

Magnitude and probability of seasonal low flow from

July-October based on 17 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 82 69 64 60 -- --

3 84 72 67 63 -- --

7 88 75 69 65 -- --

14 92 78 72 68 -- --

30 97 82 76 72 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 206 83 117 32 18

November 137 78 104 18 18

December 168 39 90 27 18

January 116 57 84 16 18

February 170 52 90 27 18

March 215 74 108 38 18

April 476 109 244 109 19

May 1,480 520 945 279 19

June 1,960 355 1,110 442 19

July 520 126 304 109 19

August 203 73 129 32 19

September 187 81 113 27 19

Annual 400 170 284 65 18
272 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

12343500 East Fork Bitterroot River at Conner, Mont.

Site Number 246

LOCATION.--Lat 45°56'00", long 114°07'30" (NAD 27), in SE1⁄4SE1⁄4 sec.7, T.2 N., R.20 W., Ravalli County, on right bank 200 ft downstream from highway 

bridge at Conner, and 0.5 mi upstream from confluence with West Fork.

DRAINAGE AREA.--405 mi2.

PERIOD OF RECORD.--20 years (1937-57). 

GAGE.--Wire-weight gage. Altitude of gage is 4,014.29 ft (NGVD 29). Sept. 20, 1910, to Sept. 17, 1916, staff gage at site 2.5 mi upstream at different datum. 

Apr. 4, 1937, to Sept. 30, 1953, wire-weight gages at several sites in immediate vicinity, all at datum 1.00 ft higher. 

REMARKS.--Diversions for irrigation of about 3,000 acres upstream from station.

Magnitude and probability of annual low flow

based on 19 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 30 19 13 9.6 -- --

3 34 22 16 12 -- --

7 41 26 19 14 -- --

14 46 29 22 16 -- --

30 55 37 29 22 -- --

60 66 47 37 29 -- --

90 70 53 45 38 -- --

120 71 58 52 49 -- --

183 74 61 56 53 -- --

Magnitude and probability of seasonal low flow from

March-June based on 21 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 58 45 39 34 -- --

3 64 49 42 37 -- --

7 69 54 47 41 -- --

14 74 60 53 48 -- --

30 84 70 65 62 -- --

Magnitude and probability of seasonal low flow from

November-February based on 20 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 32 22 18 15 -- --

3 38 27 22 18 -- --

7 46 35 31 27 -- --

14 52 43 39 37 -- --

30 60 50 46 43 -- --

Duration of daily mean flows based on 19 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

22 28 39 50 66 77 87 104

40% 30% 20% 15% 10% 5% 2% 1%

127 199 377 547 783 1,210 1,770 2,090

Magnitude and probability of annual high flow

based on 19 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 1,770 2,600 3,130 3,770 -- --

3 1,690 2,510 3,040 3,700 -- --

7 1,580 2,360 2,880 3,520 -- --

15 1,390 2,030 2,450 2,970 -- --

30 1,230 1,720 2,000 2,320 -- --

60 969 1,290 1,450 1,610 -- --

90 760 1,010 1,130 1,250 -- --

Magnitude and probability of seasonal low flow from

July-October based on 19 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 43 24 16 11 -- --

3 44 26 19 13 -- --

7 45 27 20 15 -- --

14 49 30 22 16 -- --

30 56 38 29 23 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 234 45 90 39 20

November 214 45 91 34 22

December 220 51 88 39 21

January 134 45 74 19 20

February 132 39 82 22 20

March 184 60 92 28 21

April 682 73 248 137 25

May 1,950 344 896 429 25

June 1,800 240 966 411 25

July 597 41 305 151 25

August 231 16 100 53 26

September 153 22 70 29 21

Annual 408 116 260 83 19
Statistical Summaries of Streamflow 273

12344000 Bitterroot River near Darby, Mont.

Site Number 247

LOCATION.--Lat 45°58'20", long 114°08'26" (NAD 27), in SW1⁄4SE1⁄4NE1⁄4 sec.36, T.3 N., R.21 W., Ravalli County, Hydrologic Unit 17010205, on left bank 

50 ft upstream from bridge on U.S. Highway 93, 0.3 mi downstream from Chaffin Creek, 4.1 mi southeast of Darby, and at river mile 77.2.

DRAINAGE AREA.--1,049 mi2.

PERIOD OF RECORD.--April 1937 to current year (2002). Monthly discharge only for April 1937, published in WSP 1316.

REVISED RECORDS.--WSP 1246: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 3,942.14 ft (NGVD 29). Prior to Oct. 1, 1987, at datum 1.00 ft higher. Prior to Aug. 2, 1939, nonrecording 

gage at highway bridge 45 ft upstream at same datum.

REMARKS.--Some regulation by Painted Rocks Lake (station number 12342000). Diversions for irrigation of about 5,000 acres upstream from station. Ditch 

bypassing station irrigates about 500 acres downstream from station. U.S. Geological Survey satellite telemeter at station.

Magnitude and probability of annual low flow

based on 61 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 147 117 103 92 80 73

3 156 125 110 99 87 80

7 175 142 126 114 100 92

14 190 157 141 128 113 104

30 204 172 156 143 129 120

60 227 187 169 155 141 132

90 241 196 178 164 151 143

120 258 210 191 178 165 158

183 293 246 228 215 203 196

Magnitude and probability of seasonal low flow from

March-June based on 62 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 226 175 153 136 120 110

3 237 185 162 145 127 117

7 248 196 173 156 140 130

14 263 209 187 172 157 148

30 315 238 209 189 170 159

Magnitude and probability of seasonal low flow from

November-February based on 61 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 151 118 104 92 81 74

3 160 126 110 100 88 80

7 181 143 127 115 101 92

14 197 158 142 129 114 105

30 213 173 157 144 130 121

Duration of daily mean flows based on 62 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

132 142 170 200 238 277 326 376

40% 30% 20% 15% 10% 5% 2% 1%

477 656 1,180 1,720 2,450 3,790 5,470 6,410

Magnitude and probability of annual high flow

based on 62 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 5,560 7,850 9,230 10,800 11,900 12,900

3 5,280 7,460 8,780 10,300 11,400 12,400

7 4,870 6,900 8,130 9,540 10,500 11,400

15 4,370 6,120 7,170 8,370 9,190 9,950

30 3,820 5,260 6,100 7,060 7,700 8,290

60 3,030 4,100 4,710 5,380 5,820 6,210

90 2,440 3,250 3,710 4,210 4,530 4,820

Magnitude and probability of seasonal low flow from

July-October based on 61 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 223 182 164 150 136 127

3 227 187 169 156 142 134

7 235 195 178 166 153 145

14 246 206 188 175 162 154

30 269 224 204 189 174 165

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 1,020 190 366 148 62

November 788 144 322 117 62

December 765 138 285 133 62

January 421 125 254 71 62

February 791 125 274 111 62

March 1,010 139 354 145 62

April 2,530 336 967 483 62

May 6,000 1,110 2,890 1,160 62

June 6,240 678 3,160 1,370 62

July 2,610 374 1,010 459 62

August 751 229 422 113 62

September 634 202 360 100 62

Annual 1,420 454 890 260 62
274 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

12346500 Skalkaho Creek near Hamilton, Mont.

Site Number 248

LOCATION (REVISED).--Lat 46°09'40", long 113°56'52" (NAD 27), in SE1⁄4SE1⁄4NE1⁄4, sec.27, T.5 N., R.19 W., Ravalli County, Hydrologic Unit 17010205, 

Bitterroot National Forest, on right bank 2 mi downstream from Daly Creek, 11.4 mi southeast of Hamilton, and at river mile 13.3.

DRAINAGE AREA.--87.8 mi2.

GAGE.--Water-stage recorder. Altitude of gage is 4,393.16 ft (NGVD 29).

PERIOD OF RECORD.--December 1948 to September 1953, August 1957 to September 1979, October 2000 to current year (2002). April 1920 to September 

1924 at site 3 mi downstream; records not equivalent owing to inflow, and minor diversions.

 REMARKS.--During irrigation season, flow is supplemented by releases from Kent and Dam Creek Lakes (combined capacity, 200 acre-ft). U.S. Geological 

Survey satellite telemeter at station.

Magnitude and probability of annual low flow

based on 26 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 17 15 14 14 13 --

3 18 16 15 14 14 --

7 19 17 17 16 15 --

14 21 19 18 17 16 --

30 22 20 19 18 17 --

60 25 22 21 21 20 --

90 26 24 23 22 21 --

120 28 25 24 24 23 --

183 33 30 28 27 27 --

Magnitude and probability of seasonal low flow from

March-June based on 29 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 21 18 17 16 15 --

3 22 19 17 16 15 --

7 22 19 18 17 16 --

14 23 20 19 18 17 --

30 25 21 20 19 18 --

Magnitude and probability of seasonal low flow from

November-February based on 28 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 18 15 14 14 13 --

3 18 16 15 15 15 --

7 20 18 17 17 16 --

14 21 19 18 18 17 --

30 23 20 20 19 19 --

Duration of daily mean flows based on 28 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

17 17 20 23 27 31 35 41

40% 30% 20% 15% 10% 5% 2% 1%

51 68 115 166 265 418 518 631

Magnitude and probability of annual high flow

based on 28 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 568 725 794 855 887 --

3 544 695 760 815 844 --

7 516 660 721 772 798 --

15 479 602 649 686 703 --

30 433 533 568 592 603 --

60 334 413 444 468 479 --

90 260 322 348 370 381 --

Magnitude and probability of seasonal low flow from

July-October based on 26 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 35 30 28 27 25 --

3 36 31 29 27 25 --

7 37 31 29 27 25 --

14 38 32 29 27 25 --

30 40 34 31 29 27 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 67 28 41 8.7 28

November 60 24 35 7.0 28

December 53 21 29 6.2 29

January 49 18 27 6.0 29

February 43 17 25 4.8 29

March 39 18 26 4.9 29

April 94 25 51 22 29

May 449 89 230 100 29

June 644 109 375 124 29

July 329 56 149 63 29

August 109 39 67 17 29

September 74 35 47 9.9 30

Annual 138 48 92 21 28
Statistical Summaries of Streamflow 275

12347500 Blodgett Creek near Corvallis, Mont.

Site Number 249

LOCATION.--Lat 46°16'10", long 114°14'12" (NAD 27), in NW1⁄4NW1⁄4 sec.21, T.6 N., R.21 W., Ravalli County, on right bank 4.5 mi upstream from mouth and 

6.6 mi (revised) southwest of Corvallis.

DRAINAGE AREA.--25.9 mi2.

PERIOD OF RECORD.--22 years (1947-69).

REVISED RECORDS.--WSP 1216: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 4,050 ft (NGVD 29, from topographic map). 

REMARKS.--Some regulation for irrigation at low flow by Blodgett Lake (capacity, 160 acre-ft).

Magnitude and probability of annual low flow

based on 22 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 4.4 2.7 2.1 1.7 -- --

3 4.6 2.9 2.2 1.7 -- --

7 5.2 3.2 2.4 1.8 -- --

14 5.8 3.6 2.7 2.1 -- --

30 6.8 4.2 3.2 2.5 -- --

60 9.3 5.5 4.1 3.1 -- --

90 12 6.8 4.9 3.6 -- --

120 14 7.8 5.5 4.1 -- --

183 17 10 7.5 5.9 -- --

Magnitude and probability of seasonal low flow from

March-June based on 23 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 10 7.5 6.4 5.6 -- --

3 11 8.0 6.9 6.2 -- --

7 11 8.3 7.2 6.5 -- --

14 12 8.9 7.7 6.9 -- --

30 16 11 9.3 7.9 -- --

Magnitude and probability of seasonal low flow from

November-February based on 22 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 7.0 4.1 2.9 2.1 -- --

3 7.5 4.6 3.3 2.4 -- --

7 8.3 5.0 3.6 2.6 -- --

14 8.8 5.3 3.8 2.8 -- --

30 9.8 5.9 4.3 3.3 -- --

Duration of daily mean flows based on 22 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

2.5 3.3 5.0 6.9 10 14 18 23

40% 30% 20% 15% 10% 5% 2% 1%

32 53 113 165 234 332 437 501

Magnitude and probability of annual high flow

based on 22 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 529 620 671 728 -- --

3 478 570 625 689 -- --

7 429 513 564 626 -- --

15 385 456 497 542 -- --

30 337 391 421 454 -- --

60 274 305 320 334 -- --

90 219 243 255 267 -- --

Magnitude and probability of seasonal low flow from

July-October based on 22 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 4.7 2.8 2.2 1.7 -- --

3 5.0 2.9 2.2 1.8 -- --

7 5.6 3.2 2.4 1.9 -- --

14 6.8 3.7 2.7 2.1 -- --

30 8.9 4.7 3.4 2.6 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 110 2.2 27 27 22

November 62 2.4 26 19 22

December 51 2.5 22 15 23

January 34 5.8 15 8.0 23

February 51 5.0 15 9.7 23

March 42 6.3 18 7.7 23

April 132 20 75 34 23

May 366 157 254 68 23

June 367 164 269 62 23

July 177 37 91 42 23

August 39 6.6 21 8.5 23

September 54 4.8 17 14 23

Annual 90 50 70 9.9 22
276 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

12350000 Bear Creek near Victor, Mont.

Site Number 250

LOCATION.--Lat 46°23', long 114°13' (NAD 27), in NW1⁄4 sec.9, T.7 N., R.21 W., Ravalli County, on left bank 4 mi upstream from mouth and 5 mi southwest 

of Victor.

DRAINAGE AREA.--26.8 mi2.

PERIOD OF RECORD.--18 years (1938-54, 1957-59). 

GAGE.--Water-stage recorder and timber control. Altitude of gage is 3,770 ft (NGVD 29, from topographic map). Apr. 15, 1938, to Aug. 26, 1941, staff gage 

and Aug. 27, 1941, to Sept. 30, 1952, water-stage recorder, at same site and datum at 1.00 ft higher. 

REMARKS.--No diversion upstream from station. Natural flow is supplemented by stored water from Bear Lake (capacity, 375 acre-ft) during irrigation season.

Magnitude and probability of annual low flow

based on 16 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 2.7 1.5 1.1 0.83 -- --

3 2.8 1.6 1.2 .91 -- --

7 3.1 1.9 1.4 1.2 -- --

14 3.5 2.2 1.8 1.5 -- --

30 4.4 2.8 2.2 1.8 -- --

60 6.3 3.8 3.0 2.4 -- --

90 8.4 4.9 3.8 3.1 -- --

120 11 6.0 4.6 3.6 -- --

183 13 7.8 5.9 4.8 -- --

Magnitude and probability of seasonal low flow from

March-June based on 18 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 10 6.2 4.4 3.1 -- --

3 10 6.6 4.7 3.3 -- --

7 11 7.1 5.2 3.7 -- --

14 11 7.9 6.3 5.1 -- --

30 14 9.5 7.6 6.2 -- --

Magnitude and probability of seasonal low flow from

November-February based on 18 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 6.0 3.1 1.9 1.3 -- --

3 6.4 3.3 2.2 1.4 -- --

7 6.9 3.9 2.7 1.9 -- --

14 7.7 4.6 3.4 2.6 -- --

30 8.7 5.5 4.2 3.3 -- --

Duration of daily mean flows based on 18 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

2.1 2.6 3.6 4.9 7.6 11 14 18

40% 30% 20% 15% 10% 5% 2% 1%

26 48 102 152 218 323 443 517

Magnitude and probability of annual high flow

based on 18 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 544 675 758 860 -- --

3 483 612 696 804 -- --

7 429 551 628 722 -- --

15 364 464 524 597 -- --

30 316 396 445 503 -- --

60 263 314 341 369 -- --

90 211 249 266 283 -- --

Magnitude and probability of seasonal low flow from

July-October based on 18 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 2.9 1.8 1.4 1.1 -- --

3 3.1 1.9 1.4 1.2 -- --

7 3.3 2.1 1.6 1.3 -- --

14 3.7 2.3 1.9 1.5 -- --

30 4.7 2.9 2.3 1.9 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 70 2.5 22 22 19

November 61 3.6 22 16 19

December 44 3.5 19 14 19

January 31 4.1 13 6.6 18

February 26 3.7 12 5.3 18

March 31 5.5 16 6.8 18

April 142 27 81 35 18

May 385 146 252 75 19

June 407 116 243 87 19

July 192 15 84 55 19

August 34 2.8 13 7.5 19

September 44 3.2 11 11 20

Annual 87 40 66 15 18
Statistical Summaries of Streamflow 277

12351000 Burnt Fork Bitterroot River near Stevensville, Mont.

Site Number 251

LOCATION.--Lat 46°27'50", long 113°56'40" (NAD 27), in NW1⁄4SW1⁄4 sec.11, T.8 N., R.19 W., Ravalli County, on right bank 150 ft upstream from county road 

bridge and 8 mi southeast of Stevensville

DRAINAGE AREA.--74.0 mi2.

PERIOD OF RECORD.--24 years (1938-62).

GAGE.--Crest-stage gage since July 20, 1959. Altitude of gage is 4,270 ft (NGVD 29, from topographic map). May 8, 1920, to Aug. 23, 1924, staff gage at site 

150 ft downstream at different datum. April 1938, to Mar. 18, 1953, staff gage and Mar. 19, 1953, to Mar. 15, 1955, wire-weight gage, at site 150 ft downstream 

at datum 2.00 ft lower.

REMARKS.--Figures of daily discharge do not include diversion by Sunset Highline ditch which diverts 0.5 mi upstream from station for irrigation of about 

2,000 acres downstream from station. During irrigation season, natural flow of stream is augmented by release from Burnt Fork Lake (capacity, 510 acre-ft).

Magnitude and probability of annual low flow

based on 23 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 9.7 6.5 4.9 3.7 -- --

3 10 7.0 5.4 4.2 -- --

7 11 8.4 7.2 6.2 -- --

14 12 10 9.2 8.5 -- --

30 14 12 11 10 -- --

60 15 14 13 12 -- --

90 17 15 14 13 -- --

120 18 15 15 14 -- --

183 19 17 16 15 -- --

Magnitude and probability of seasonal low flow from

March-June based on 24 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 14 9.1 6.5 4.5 -- --

3 14 9.6 7.0 5.0 -- --

7 14 11 8.5 6.9 -- --

14 14 12 10 9.0 -- --

30 16 13 12 11 -- --

Magnitude and probability of seasonal low flow from

November-February based on 24 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 10 7.8 6.6 5.7 -- --

3 11 8.3 7.1 6.3 -- --

7 12 9.5 8.4 7.5 -- --

14 13 11 10 9.3 -- --

30 14 13 12 11 -- --

Duration of daily mean flows based on 24 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

9.0 11 12 14 17 19 21 24

40% 30% 20% 15% 10% 5% 2% 1%

30 40 69 92 140 215 291 354

Magnitude and probability of annual high flow

based on 24 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 288 392 448 507 -- --

3 272 373 428 485 -- --

7 255 348 398 451 -- --

15 231 316 361 409 -- --

30 202 273 312 351 -- --

60 158 212 242 273 -- --

90 125 167 191 217 -- --

Magnitude and probability of seasonal low flow from

July-October based on 24 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 16 13 12 12 -- --

3 16 14 13 12 -- --

7 17 15 14 13 -- --

14 17 15 14 13 -- --

30 19 16 15 15 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 44 14 22 6.9 26

November 42 14 22 6.4 26

December 30 13 20 4.3 24

January 26 13 17 3.7 24

February 27 12 16 3.6 24

March 26 10 17 4.0 24

April 108 15 42 22 25

May 296 43 139 64 29

June 429 53 180 79 29

July 146 26 66 31 28

August 43 19 30 7.0 27

September 37 12 22 4.4 27

Annual 79 25 48 14 24
278 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

12352500 Bitterroot River near Missoula, Mont.

Site Number 252

LOCATION.--Lat 46o49’55", long 114o03’11" (NAD 27), in SW1⁄4NW1⁄4NE1⁄4 sec.1, T.12 N., R.20 W., Missoula County, Hydrologic Unit 17010205, on right 

bank 40 ft downstream from bridge on U.S. Highway 93, 0.5 mi south of Fort Missoula, and at river mile 5.7.

DRAINAGE AREA.--2,814 mi2.

PERIOD OF RECORD.--July 1898 to November 1901, May 1903 to December 1904, July 1989 to current year (2002).

GAGE.--Water-stage recorder. Altitude of gage is 3,110 ft (NGVD 29). Prior to Jan. 1, 1905, nonrecording gage at site 1.5 mi upstream at different datum.

REMARKS.--Some regulation by Painted Rocks Lake (station number 12342000). Diversions for irrigation of about 111,000 acres upstream from station. U.S. 

Geological Survey satellite telemeter at station.

Magnitude and probability of annual low flow

based on 13 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 462 363 321 290 -- --

3 487 386 342 310 -- --

7 549 440 392 356 -- --

14 620 497 442 400 -- --

30 664 533 479 439 -- --

60 697 565 511 471 -- --

90 736 602 547 507 -- --

120 798 662 607 568 -- --

183 835 696 649 620 -- --

Magnitude and probability of seasonal low flow from

March-June based on 16 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 813 638 572 526 -- --

3 838 670 608 566 -- --

7 891 714 647 601 -- --

14 967 778 706 658 -- --

30 1,170 903 793 714 -- --

Magnitude and probability of seasonal low flow from

November-February based on 15 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 493 381 333 299 -- --

3 517 404 355 320 -- --

7 586 465 411 370 -- --

14 663 532 470 423 -- --

30 722 579 519 476 -- --

Duration of daily mean flows based on 16 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

403 447 544 605 727 854 982 1,120

40% 30% 20% 15% 10% 5% 2% 1%

1,350 1,790 3,100 4,380 6,030 8,610 12,500 15,500

Magnitude and probability of annual high flow

based on 16 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 12,900 17,900 21,000 24,800 -- --

3 12,000 16,600 19,600 23,200 -- --

7 10,900 15,100 17,700 20,800 -- --

15 9,710 13,300 15,600 18,300 -- --

30 8,580 11,800 13,900 16,600 -- --

60 7,010 9,440 11,000 13,000 -- --

90 5,700 7,650 8,920 10,500 -- --

Magnitude and probability of seasonal low flow from

July-October based on 17 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 654 507 439 389 -- --

3 662 514 446 395 -- --

7 680 526 455 402 -- --

14 700 538 464 408 -- --

30 743 579 503 446 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 1,570 568 1,010 326 18

November 2,210 614 1,090 369 18

December 3,140 530 1,010 605 17

January 1,790 542 893 352 16

February 3,030 477 993 624 16

March 2,020 801 1,270 415 16

April 4,940 1,340 2,730 1,180 16

May 13,400 4,040 6,640 2,740 17

June 14,000 2,400 7,740 3,480 17

July 4,120 980 2,530 1,070 18

August 1,270 503 905 217 18

September 1,140 455 841 218 18

Annual 3,820 1,370 2,300 744 16
Statistical Summaries of Streamflow 279

12353000 Clark Fork below Missoula, Mont.

Site Number 253

LOCATION.--Lat 46°52'09", long 114°07'33" (NAD 27), in NW1⁄4NE1⁄4SE1⁄4 sec.21, T.13 N., R.20 W., Missoula County, Hydrologic Unit 17010204, on right 

bank 1.0 mi downstream from Bitterroot River, 4.5 mi west of Missoula, and at river mile 349.5.

DRAINAGE AREA.--9,003 mi2.

PERIOD OF RECORD.--October 1929 to current year (2002).

REVISED RECORDS.--WSP 1042: 1931. WSP 1246: Drainage area. WSP 1316: 1932(M), 1935(M), 1946(M).

GAGE.--Water-stage recorder. Altitude of gage is 3,083.88 ft (NGVD 29, levels by U.S. Army Corps of Engineers).

REMARKS.--Some diurnal fluctuation at low flow caused by powerplant at Milltown 14.9 mi upstream. Diversions for irrigation of about 235,000 acres upstream 

from station. U.S. Geological Survey satellite telemeter at station. 

Magnitude and probability of annual low flow

based on 72 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1,100 869 763 683 601 551

3 1,180 927 809 720 628 571

7 1,350 1,060 911 800 685 614

14 1,520 1,180 1,020 889 757 675

30 1,710 1,320 1,120 969 812 715

60 1,890 1,470 1,260 1,100 937 836

90 2,030 1,610 1,420 1,280 1,130 1,040

120 2,190 1,750 1,560 1,420 1,270 1,180

183 2,310 1,840 1,640 1,480 1,330 1,230

Magnitude and probability of seasonal low flow from

March-June based on 73 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 2,060 1,630 1,450 1,320 1,200 1,120

3 2,120 1,710 1,540 1,420 1,300 1,230

7 2,220 1,820 1,660 1,560 1,460 1,410

14 2,370 1,970 1,830 1,740 1,650 1,610

30 2,780 2,230 2,020 1,890 1,760 1,690

Magnitude and probability of seasonal low flow from

November-February based on 72 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1,110 871 779 716 656 621

3 1,210 941 835 760 688 645

7 1,430 1,100 970 874 778 721

14 1,650 1,300 1,150 1,040 929 862

30 1,900 1,520 1,350 1,220 1,090 1,010

Duration of daily mean flows based on 73 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

920 1,110 1,340 1,590 1,910 2,220 2,550 2,870

40% 30% 20% 15% 10% 5% 2% 1%

3,350 4,220 7,180 9,780 13,600 20,300 27,600 32,800

Magnitude and probability of annual high flow

based on 73 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 27,100 37,700 43,900 50,800 55,500 59,800

3 26,200 36,400 42,500 49,300 53,800 58,000

7 24,300 34,000 39,700 46,100 50,500 54,400

15 22,000 30,800 35,900 41,900 45,800 49,500

30 19,500 26,900 31,200 36,100 39,300 42,300

60 16,000 21,600 24,700 28,100 30,200 32,200

90 13,100 17,600 20,000 22,600 24,300 25,700

Magnitude and probability of seasonal low flow from

July-October based on 72 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1,610 1,180 992 855 719 638

3 1,660 1,220 1,020 876 734 649

7 1,700 1,240 1,040 895 749 663

14 1,760 1,290 1,080 929 779 690

30 1,890 1,370 1,150 982 818 721

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 6,620 1,390 2,720 876 73

November 5,110 1,470 2,740 743 73

December 6,060 1,410 2,480 912 73

January 4,400 871 2,250 702 73

February 6,700 1,110 2,490 975 73

March 7,010 1,740 3,080 1,070 73

April 16,500 2,300 6,370 3,030 73

May 30,400 5,110 14,800 5,550 73

June 34,000 4,620 16,700 7,700 73

July 16,300 1,360 5,870 3,100 73

August 5,530 810 2,300 900 73

September 5,160 909 2,290 806 73

Annual 8,830 2,580 5,350 1,600 73
280 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

12354000 St. Regis River near St. Regis, Mont.

Site Number 254

LOCATION.--Lat 47o17’49", long 115o07’18" (NAD 27) near center of NW1⁄4NE1⁄4 sec.26, T.18 N., R.28 W., Mineral County, on left bank 50 ft downstream from 

road bridge, 500 ft upstream from Little Joe Creek, 1.2 mi west of St. Regis, and at river mile 1.7.

DRAINAGE AREA.--303 mi2.

PERIOD OF RECORD.--September 1910 to September 1917 (no winter records), annual maximum, water year 1948, published in WSP 1080, September 1958 to 

September 1975, February 2002 to September 2002. Monthly discharge only for some periods, published in WSP 1316, 1736.

REVISED RECORDS.--WSP 1246: water year 1912; WSP 1316: drainage area, 1911.

GAGE.--Water-stage recorder. Altitude of gage is 2,645.00 ft (NGVD 29). September 1910 to September 1917, nonrecording gage at site 2 mi upstream at 

different datum.

REMARKS.--Minor diversions for irrigation upstream from station. U.S. Geological Survey satellite telemeter at station.

Magnitude and probability of annual low flow

based on 16 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 71 56 50 46 -- --

3 79 64 57 52 -- --

7 84 71 65 61 -- --

14 90 77 72 68 -- --

30 96 83 78 75 -- --

60 108 92 86 81 -- --

90 117 97 89 84 -- --

120 124 102 94 89 -- --

183 148 116 104 96 -- --

Magnitude and probability of seasonal low flow from

March-June based on 22 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 191 124 100 85 -- --

3 200 131 107 91 -- --

7 213 140 114 98 -- --

14 239 154 125 106 -- --

30 330 203 156 126 -- --

Magnitude and probability of seasonal low flow from

November-February based on 17 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 81 60 51 46 -- --

3 90 69 59 53 -- --

7 99 76 67 62 -- --

14 112 84 74 69 -- --

30 130 93 81 76 -- --

Duration of daily mean flows based on 17 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

69 75 91 103 124 152 183 247

40% 30% 20% 15% 10% 5% 2% 1%

355 581 1,060 1,420 1,910 2,670 3,640 4,180

Magnitude and probability of annual high flow

based on 17 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 3,780 5,270 6,170 7,190 -- --

3 3,540 4,760 5,440 6,170 -- --

7 3,140 4,100 4,590 5,090 -- --

15 2,740 3,580 4,010 4,420 -- --

30 2,430 3,180 3,550 3,910 -- --

60 2,010 2,530 2,750 2,940 -- --

90 1,660 2,050 2,210 2,340 -- --

Magnitude and probability of seasonal low flow from

July-October based on 20 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 101 86 78 71 -- --

3 102 86 78 72 -- --

7 104 88 80 73 -- --

14 108 90 82 75 -- --

30 113 95 85 78 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 350 86 143 59 23

November 590 101 235 149 20

December 555 92 214 150 18

January 1,360 89 282 300 17

February 760 87 301 183 19

March 1,370 94 408 275 22

April 2,060 349 1,250 495 25

May 4,700 671 2,210 843 25

June 3,370 388 1,570 786 25

July 1,150 155 406 214 25

August 313 83 165 47 25

September 204 77 132 31 26

Annual 938 256 580 164 17
Statistical Summaries of Streamflow 281

12354500 Clark Fork at St. Regis, Mont.

Site Number 255

LOCATION.--Lat 47°18'07", long 115°05'11" (NAD 27), in NW1⁄4SE1⁄4SW1⁄4 sec.19, T.18 N., R.27 W., Mineral County, Hydrologic Unit 17010204, on left bank 

at St. Regis, 0.4 mi downstream from St. Regis River, and at river mile 270.3.

DRAINAGE AREA.--10,709 mi2.

PERIOD OF RECORD.--October 1910 to current year (2002). Monthly discharge only for some periods, published in WSP 1316.

REVISED RECORDS.--WSP 1246: Drainage area. WSP 1316: 1916-17, 1920, 1929-31(M), 1933(M).

GAGE.--Water-stage recorder. Altitude of gage is 2,600.37 ft (NGVD 29, levels by U.S. Army Corps of Engineers). Prior to Nov. 29, 1933, nonrecording gage 

at same site and datum.

REMARKS.--Diversions for irrigation of about 244,000 acres upstream from station. U.S. Geological Survey satellite telemeter at station.

Magnitude and probability of annual low flow

based on 86 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1,640 1,290 1,140 1,020 909 839

3 1,740 1,380 1,220 1,100 982 908

7 1,940 1,570 1,400 1,270 1,140 1,050

14 2,160 1,750 1,550 1,390 1,230 1,120

30 2,390 1,930 1,710 1,520 1,330 1,210

60 2,600 2,110 1,870 1,680 1,490 1,360

90 2,740 2,240 2,020 1,850 1,670 1,560

120 2,920 2,380 2,150 1,970 1,780 1,670

183 3,090 2,490 2,230 2,040 1,860 1,750

Magnitude and probability of seasonal low flow from

March-June based on 87 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 2,850 2,190 1,950 1,780 1,620 1,530

3 2,900 2,290 2,070 1,920 1,790 1,710

7 2,990 2,400 2,190 2,060 1,930 1,870

14 3,170 2,570 2,370 2,240 2,130 2,080

30 3,760 2,960 2,670 2,490 2,320 2,230

Magnitude and probability of seasonal low flow from

November-February based on 86 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1,690 1,300 1,140 1,030 920 854

3 1,790 1,390 1,230 1,110 1,000 935

7 2,010 1,610 1,440 1,320 1,200 1,130

14 2,280 1,840 1,660 1,520 1,390 1,310

30 2,550 2,090 1,890 1,740 1,590 1,510

Duration of daily mean flows based on 86 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

1,500 1,590 1,850 2,240 2,610 2,980 3,420 3,900

40% 30% 20% 15% 10% 5% 2% 1%

4,550 6,030 10,300 13,800 18,900 27,300 36,800 44,700

Magnitude and probability of annual high flow

based on 86 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 35,500 48,600 56,000 64,000 69,200 73,900

3 34,600 47,500 54,800 62,800 68,000 72,700

7 32,500 44,900 52,000 59,900 65,100 69,800

15 29,500 40,800 47,300 54,500 59,300 63,700

30 26,300 36,000 41,600 47,800 51,900 55,600

60 21,800 29,200 33,400 37,800 40,700 43,300

90 18,000 24,000 27,300 30,800 33,000 35,000

Magnitude and probability of seasonal low flow from

July-October based on 86 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 2,400 1,860 1,610 1,430 1,240 1,120

3 2,440 1,880 1,630 1,430 1,240 1,120

7 2,480 1,910 1,640 1,450 1,250 1,130

14 2,550 1,950 1,680 1,480 1,280 1,150

30 2,680 2,040 1,760 1,550 1,330 1,200

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 8,040 1,850 3,490 1,030 86

November 7,050 1,940 3,610 1,060 87

December 10,700 1,910 3,460 1,600 87

January 10,500 1,450 3,170 1,380 87

February 10,700 1,590 3,420 1,450 87

March 11,500 2,200 4,290 1,750 87

April 24,900 3,330 9,300 4,170 87

May 42,100 7,190 20,600 7,350 87

June 42,400 6,020 22,400 9,890 87

July 25,500 2,000 8,080 4,230 87

August 6,750 1,450 3,310 1,160 87

September 6,250 1,350 3,050 931 87

Annual 11,600 3,420 7,350 2,180 86
282 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

12355000 Flathead River at Flathead, British Columbia

Site Number 256

LOCATION.--Lat 49°00'05", long 114°28'34" (NAD 27), Hydrologic Unit 17010206, on left bank 200 ft north of international boundary at Flathead, British 

Columbia, 1.6 mi upstream from Sage Creek, 6.5 mi northwest of Trail Creek, Mont., and at river mile 216.6.

DRAINAGE AREA.--427 mi2.

PERIOD OF RECORD.--March 1929 to June 1995 (no winter records prior to 1952). Prior to 1934, published as "Flathead River near Trail Creek, MT." October 

1970 to September 1972, published as "North Fork Flathead River at Flathead, British Columbia." October 1999 to current year (2002) gage reestablished and 

operated by USGS at site on left bank in British Columbia.

GAGE.--Water-stage recorder. Altitude of gage is 3,964.95 ft (NGVD 29). Prior to Sept. 1, 1949, nonrecording gage and Sept. 1, 1949, to Oct. 4, 1964, waterstage recorder at site 1,200 ft upstream at datum 11.01 ft higher. Oct. 5, 1964, to Aug. 1, 1973, water-stage recorder at site on left bank 155 ft upstream at 

datum 1.79 ft higher. Aug. 2, 1973, to June 28, 1995, operated by Water Survey Canada at site on right bank at datum 3.21 ft higher. October 1999 to current 

year (2002) at site 200 ft upstream from international border in British Columbia on left bank.

REMARKS.--U.S. Geological Survey satellite telemeter at station.

Magnitude and probability of annual low flow

based on 45 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 95 80 74 70 65 --

3 101 86 80 75 71 --

7 109 93 85 80 74 --

14 118 99 90 83 76 --

30 127 108 99 93 86 --

60 152 123 111 103 95 --

90 170 136 123 114 106 --

120 197 153 137 126 116 --

183 231 182 164 151 140 --

Magnitude and probability of seasonal low flow from

March-June based on 47 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 129 105 96 92 88 --

3 133 107 99 94 90 --

7 142 114 105 99 94 --

14 151 120 110 104 99 --

30 167 132 121 115 110 --

Magnitude and probability of seasonal low flow from

November-February based on 47 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 99 81 74 70 66 --

3 105 87 80 76 71 --

7 117 94 86 80 75 --

14 128 103 92 85 78 --

30 141 113 102 94 86 --

Duration of daily mean flows based on 46 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

94 100 120 143 182 222 263 338

40% 30% 20% 15% 10% 5% 2% 1%

460 730 1,500 2,120 3,000 4,450 5,970 7,390

Magnitude and probability of annual high flow

based on 46 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 7,260 9,380 10,600 12,000 12,900 --

3 6,850 8,630 9,550 10,500 11,100 --

7 6,090 7,600 8,350 9,100 9,540 --

15 5,280 6,640 7,340 8,040 8,470 --

30 4,550 5,670 6,230 6,800 7,140 --

60 3,560 4,370 4,750 5,110 5,310 --

90 2,810 3,420 3,700 3,960 4,100 --

Magnitude and probability of seasonal low flow from

July-October based on 68 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 195 161 147 138 128 123

3 198 163 149 139 130 124

7 203 166 152 142 132 126

14 211 171 155 144 133 127

30 224 180 163 151 139 133

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 1,280 127 327 219 68

November 1,260 124 348 235 59

December 881 97 239 133 48

January 458 87 187 78 47

February 345 83 173 61 47

March 685 98 200 102 47

April 2,960 189 913 524 67

May 5,580 1,540 3,510 874 71

June 6,690 824 3,100 1,410 71

July 2,420 279 987 461 70

August 937 188 385 136 70

September 785 132 291 114 70

Annual 1,380 377 908 217 46
Statistical Summaries of Streamflow 283

12355500 North Fork Flathead River near Columbia Falls, Mont.

Site Number 257

LOCATION.--Lat 48°29'44", long 114°07'36" (NAD 27), in NE1⁄4SW1⁄4NW1⁄4 sec.35, T.32 N., R.20 W., Flathead County, Hydrologic Unit 17010206, on right 

bank 1.5 mi downstream from Canyon Creek, 3.8 mi upstream from Middle Fork, 8.8 mi northeast of Columbia Falls, and at river mile 162.1.

DRAINAGE AREA.--1,548 mi2.

PERIOD OF RECORD.--September 1910 to September 1917 (no winter records in water years 1913, 1916, 1917), April 1929 to February 1935 (incomplete), June 

1935 to current year (2002). Monthly discharge only for some periods, published in WSP 1316. Published as "Flathead River near Columbia Falls" 1915-17, 

1929-70.

REVISED RECORDS.--WSP 1216: Drainage area. WSP 1246: 1911, 1912(M), 1915-17(M), 192(M), 1938-39(M), 1946(M).

GAGE.--Water-stage recorder. Altitude of gage is 3,145.59 ft (NGVD 29). September 1910 to September 1917 and April to August 1929, nonrecording gages, 

and May 1, 1930, to Sept. 30, 1962, water-stage recorder, all at site 2.7 mi downstream at different datums.

REMARKS.--A few small diversions from tributaries for irrigation upstream from station. Bureau of Reclamation satellite telemeter at station.

Magnitude and probability of annual low flow

based on 70 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 373 308 280 259 238 225

3 397 329 301 281 260 248

7 435 363 334 314 294 283

14 479 401 370 348 328 316

30 536 447 411 385 359 344

60 632 504 452 415 379 357

90 696 543 485 444 406 384

120 782 593 522 473 427 401

183 905 702 625 573 524 497

Magnitude and probability of seasonal low flow from

March-June based on 76 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 545 430 391 366 345 334

3 567 448 407 381 359 347

7 606 473 426 395 368 353

14 641 501 453 423 397 384

30 755 576 514 474 438 419

Magnitude and probability of seasonal low flow from

November-February based on 73 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 389 312 282 261 240 227

3 417 335 302 283 262 252

7 467 374 337 318 300 286

14 520 417 375 351 335 318

30 576 461 416 387 369 347

Duration of daily mean flows based on 72 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

360 397 463 556 687 836 1,010 1,250

40% 30% 20% 15% 10% 5% 2% 1%

1,670 2,540 4,720 6,450 8,700 12,500 16,400 20,100

Magnitude and probability of annual high flow

based on 72 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 18,500 24,900 29,000 34,100 37,800 41,400

3 17,700 23,200 26,300 29,800 32,200 34,400

7 16,100 20,600 23,100 25,700 27,300 28,800

15 14,100 18,100 20,300 22,600 24,100 25,500

30 12,500 15,700 17,300 19,100 20,200 21,100

60 10,300 12,600 13,800 14,900 15,600 16,200

90 8,420 10,300 11,200 12,000 12,500 13,000

Magnitude and probability of seasonal low flow from

July-October based on 76 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 772 636 579 538 498 474

3 782 644 586 545 505 481

7 800 657 598 556 515 490

14 826 676 615 572 529 504

30 890 720 652 603 556 528

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 3,650 517 1,170 604 78

November 3,730 420 1,210 718 76

December 3,390 394 907 503 77

January 2,130 325 752 324 75

February 2,020 342 727 302 75

March 2,600 406 880 405 76

April 6,880 833 3,250 1,380 78

May 15,200 4,990 9,790 2,470 80

June 20,800 3,350 10,100 3,930 81

July 11,000 1,440 4,060 1,820 80

August 3,230 747 1,630 515 79

September 2,650 552 1,160 402 78

Annual 4,720 1,380 2,960 693 72
284 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

12357000 Middle Fork Flathead River at Essex, Mont.

Site Number 258

LOCATION.--Lat 48°16'30", long 113°36'10" (NAD 27), in NE1⁄4SW1⁄4 sec.14, T.29 N., R.16 W., Flathead County, on right bank 0.7 mi upstream from Ole Creek, 

0.7 mi southeast of Essex, 4.4 mi downstream from Bear Creek, and at river mile 40.0.

DRAINAGE AREA.--510 mi2.

PERIOD OF RECORD.--22 years. October 1939 to September 1953, June 1956 to September 1964 (discontinued). Monthly discharge only for October 1939, 

published in WSP 1316.

REVISED RECORDS.--WSP 1216: Drainage area. WSP 1246: 1940(M).

GAGE.--Staff gage. Altitude of gage is 3,721.93 ft (NGVD 29). Prior to May 14, 1964, water-stage recorder at same site and datum.

REMARKS.--No regulation or diversion above station.

Magnitude and probability of annual low flow

based on 20 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 112 83 70 61 -- --

3 119 89 76 67 -- --

7 132 99 85 74 -- --

14 142 110 97 87 -- --

30 157 123 108 98 -- --

60 180 136 117 103 -- --

90 200 144 124 109 -- --

120 226 156 131 113 -- --

183 260 180 150 130 -- --

Magnitude and probability of seasonal low flow from

March-June based on 22 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 160 111 91 76 -- --

3 162 117 97 83 -- --

7 171 129 111 98 -- --

14 182 141 124 112 -- --

30 227 166 142 125 -- --

Magnitude and probability of seasonal low flow from

November-February based on 21 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 120 83 70 61 -- --

3 127 90 77 68 -- --

7 141 100 86 75 -- --

14 155 111 97 87 -- --

30 172 124 109 99 -- --

Duration of daily mean flows based on 22 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

95 102 125 146 183 223 263 335

40% 30% 20% 15% 10% 5% 2% 1%

447 683 1,450 2,180 3,370 5,240 7,390 8,490

Magnitude and probability of annual high flow

based on 22 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 7,950 12,300 16,200 22,500 -- --

3 7,650 11,100 13,600 17,200 -- --

7 7,130 9,570 11,000 12,500 -- --

15 6,300 8,270 9,290 10,300 -- --

30 5,510 7,010 7,720 8,390 -- --

60 4,300 5,380 5,870 6,320 -- --

90 3,360 4,200 4,580 4,930 -- --

Magnitude and probability of seasonal low flow from

July-October based on 21 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 174 142 130 121 -- --

3 176 145 132 124 -- --

7 180 148 136 128 -- --

14 185 153 141 133 -- --

30 197 163 150 142 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 1,080 137 347 237 22

November 812 108 355 223 22

December 884 103 333 224 22

January 489 93 223 103 22

February 602 100 238 133 22

March 490 128 251 98 22

April 2,850 389 1,320 656 22

May 6,720 1,970 4,350 1,110 22

June 7,540 1,000 3,790 1,930 23

July 2,590 309 1,040 628 23

August 557 164 326 103 23

September 427 148 244 71 23

Annual 1,580 465 1,070 300 22
Statistical Summaries of Streamflow 285

12357500 Middle Fork Flathead River at West Glacier, Mont.

Site Number 259

LOCATION.--Lat 48°30'00", long 113°58'30" (NAD 27), in NW1⁄4NW1⁄4 sec.36, T.32 N., R.19 W., Flathead County, on left bank at Belton, 0.5 mi upstream from 

highway bridge, and 2 mi upstream from outlet of Lake McDonald.

DRAINAGE AREA.--943 mi2 (revised).

PERIOD OF RECORD.--15 years (1910-12, 1915-16, 1918-19, 1920-21, 1929-33, 1943-47).

GAGE.--Staff gage. Altitude of gage is 3,170 ft (NGVD 29, from river profile map).

REMARKS.--No substantial diversion or regulation above station.

Magnitude and probability of annual low flow

based on 10 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 241 170 140 119 -- --

3 247 182 154 135 -- --

7 260 200 175 158 -- --

14 296 233 204 183 -- --

30 355 272 233 204 -- --

60 418 315 267 231 -- --

90 472 340 281 236 -- --

120 546 380 307 253 -- --

183 610 443 365 307 -- --

Magnitude and probability of seasonal low flow from

March-June based on 18 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 331 214 168 137 -- --

3 340 226 182 152 -- --

7 366 255 213 183 -- --

14 397 284 243 216 -- --

30 560 372 304 259 -- --

Magnitude and probability of seasonal low flow from

November-February based on 12 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 282 214 187 167 -- --

3 286 218 191 171 -- --

7 296 227 198 177 -- --

14 331 251 216 189 -- --

30 362 273 234 205 -- --

Duration of daily mean flows based on 13 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

203 231 290 353 456 568 722 950

40% 30% 20% 15% 10% 5% 2% 1%

1,270 1,950 3,900 5,460 7,450 10,500 14,500 16,700

Magnitude and probability of annual high flow

based on 13 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 15,900 23,400 29,400 38,500 -- --

3 14,600 19,800 23,600 28,600 -- --

7 12,700 17,000 20,100 24,400 -- --

15 11,300 15,000 17,500 20,700 -- --

30 9,660 12,600 14,600 17,100 -- --

60 8,120 10,300 11,500 12,900 -- --

90 6,700 8,510 9,540 10,700 -- --

Magnitude and probability of seasonal low flow from

July-October based on 18 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 452 336 291 259 -- --

3 462 342 295 263 -- --

7 475 350 301 266 -- --

14 493 361 308 272 -- --

30 548 396 334 290 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 2,120 299 828 486 21

November 1,960 240 817 459 21

December 1,200 218 618 282 17

January 892 211 476 180 14

February 862 207 483 157 14

March 1,460 257 668 358 18

April 6,240 584 2,870 1,360 22

May 11,200 4,170 8,190 1,850 22

June 15,200 3,180 8,050 3,560 22

July 6,440 1,010 2,630 1,230 22

August 1,470 547 973 278 22

September 1,920 397 744 336 23

Annual 3,380 1,260 2,290 643 13
286 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

12358500 Middle Fork Flathead River near West Glacier, Mont.

Site Number 260

LOCATION.--Lat 48°29'43", long 114°00'33" (NAD 27), in S1⁄2SW1⁄4NE1⁄4 sec.34, T.32 N., R.19 W., Flathead County, Hydrologic Unit 17010207, on left bank 

0.8 mi downstream from McDonald Creek, 1.3 mi west of West Glacier, and at river mile 3.8.

DRAINAGE AREA.--1,128 mi2.

PERIOD OF RECORD.--October 1939 to current year (2002). Prior to October 1947, published as "near Belton."

REVISED RECORDS.--WSP 1216: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 3,128.72 ft (NGVD 29). Prior to Nov. 22, 1950, nonrecording gage at present site and datum.

REMARKS.--Bureau of Reclamation satellite at station. 

Magnitude and probability of annual low flow

based on 62 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 335 266 235 213 190 176

3 350 280 249 226 203 189

7 373 301 268 244 220 204

14 398 323 290 266 241 225

30 440 352 314 286 258 241

60 529 398 346 309 273 253

90 605 436 372 329 288 265

120 686 475 396 344 295 267

183 799 572 489 434 383 354

Magnitude and probability of seasonal low flow from

March-June based on 63 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 489 363 319 292 267 254

3 502 374 331 303 278 265

7 535 392 342 309 280 263

14 576 416 360 323 290 272

30 710 495 419 368 322 296

Magnitude and probability of seasonal low flow from

November-February based on 62 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 361 272 236 214 191 177

3 381 288 250 228 205 190

7 411 312 271 245 222 205

14 442 337 295 266 243 226

30 489 368 321 289 259 243

Duration of daily mean flows based on 63 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

282 304 373 435 557 697 883 1,110

40% 30% 20% 15% 10% 5% 2% 1%

1,480 2,340 4,510 6,230 8,530 12,100 16,200 19,700

Magnitude and probability of annual high flow

based on 63 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 18,100 25,800 32,400 42,700 52,000 62,900

3 17,500 23,600 28,000 33,900 38,600 43,500

7 16,000 20,700 23,500 26,900 29,300 31,500

15 14,100 18,000 20,200 22,700 24,500 26,100

30 12,500 15,600 17,300 19,200 20,400 21,500

60 10,200 12,500 13,700 15,000 15,800 16,400

90 8,370 10,100 11,000 11,900 12,400 12,800

Magnitude and probability of seasonal low flow from

July-October based on 62 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 560 432 380 344 309 289

3 570 438 385 348 311 290

7 588 451 395 356 318 296

14 615 467 408 367 327 303

30 683 514 447 400 354 327

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 3,000 367 1,050 665 63

November 5,600 279 1,170 998 63

December 3,750 262 914 655 63

January 2,420 282 705 380 63

February 2,690 244 710 456 63

March 2,780 307 853 473 63

April 7,090 664 3,170 1,320 63

May 14,700 5,260 9,590 2,250 63

June 19,900 3,580 10,100 3,900 63

July 8,160 1,250 3,970 1,750 63

August 2,360 576 1,360 424 63

September 2,510 420 947 412 63

Annual 4,070 1,440 2,890 665 63
Statistical Summaries of Streamflow 287

12359000 South Fork Flathead River at Spotted Bear Ranger Station, near Hungry Horse, Mont.

Site Number 261

LOCATION.--Lat 47°55'19", long 113°31'27" (NAD 27), in SE1⁄4SW1⁄4 sec.17, T.25 N., R.15 W., Flathead County, Flathead National Forest, on left bank 600 ft 

south of Spotted Bear Ranger Station, 1,000 ft upstream from Spotted Bear River, 40.3 mi southeast of Hungry Horse, and at river mile 52.9.

DRAINAGE AREA.--958 mi2.

PERIOD OF RECORD.--17 years. August 1948 to September 1957 and August 1959 to September 1967 (discontinued). 

REVISED RECORDS.--WSP 1216: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 3,670 ft (NGVD 29, from river-profile map). 

Magnitude and probability of annual low flow

based on 15 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 194 156 139 126 -- --

3 203 164 145 131 -- --

7 220 179 159 145 -- --

14 235 194 176 163 -- --

30 261 217 197 182 -- --

60 300 245 227 215 -- --

90 330 260 237 222 -- --

120 359 279 251 233 -- --

183 417 323 288 264 -- --

Magnitude and probability of seasonal low flow from

March-June based on 17 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 290 225 191 164 -- --

3 298 234 200 173 -- --

7 313 249 216 189 -- --

14 330 261 225 197 -- --

30 372 280 239 209 -- --

Magnitude and probability of seasonal low flow from

November-February based on 17 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 201 164 147 134 -- --

3 213 172 152 137 -- --

7 233 186 164 147 -- --

14 253 203 181 165 -- --

30 278 223 201 185 -- --

Duration of daily mean flows based on 17 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

177 196 222 265 318 368 453 566

40% 30% 20% 15% 10% 5% 2% 1%

754 1,230 2,700 4,160 6,320 9,440 12,000 14,700

Magnitude and probability of annual high flow

based on 17 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 14,600 18,700 21,600 25,700 -- --

3 13,800 17,100 19,300 22,200 -- --

7 12,400 14,700 16,100 17,600 -- --

15 10,900 13,100 14,400 16,000 -- --

30 9,550 11,200 12,200 13,300 -- --

60 7,690 8,920 9,610 10,400 -- --

90 6,070 7,000 7,500 8,050 -- --

Magnitude and probability of seasonal low flow from

July-October based on 15 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 339 266 236 215 -- --

3 343 268 237 216 -- --

7 351 273 241 218 -- --

14 362 278 245 221 -- --

30 388 293 257 232 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 2,220 237 623 479 17

November 1,360 197 529 313 17

December 1,010 202 452 223 17

January 672 204 349 115 17

February 883 210 386 191 17

March 760 180 395 135 17

April 3,330 610 1,760 843 17

May 9,170 4,270 6,800 1,500 17

June 11,500 4,460 7,950 2,290 17

July 5,890 1,080 2,720 1,380 17

August 1,420 418 730 244 17

September 1,250 294 500 244 19

Annual 2,360 1,470 1,930 284 17
288 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

12359800 South Fork Flathead River above Twin Creek, near Hungry Horse, Mont.

Site Number 262

LOCATION.--Lat 47°58'45", long 113°33'36" (NAD 27), in NE1⁄4NW1⁄4NE1⁄4 sec.36, T.26 N., R.16 W., Flathead County, Hydrologic Unit 17010209, Flathead 

National Forest, on left bank 0.1 mi downstream from Tin Creek, 0.4 mi upstream from Twin Creek, 36.3 mi southeast of Hungry Horse, and at river mile 42.2.

DRAINAGE AREA.--1,160 mi2.

PERIOD OF RECORD.--October 1964 to September 1982, October 1984 to current year (2002, no winter records).

GAGE.--Water-stage recorder. Altitude of gage is 3,575 ft (NGVD 29, from river-profile map).

REMARKS.--No known regulation or diversions upstream from station. Bureau of Reclamation satellite telemeter at station. 

Magnitude and probability of annual low flow

based on 17 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 215 178 161 148 -- --

3 227 186 168 154 -- --

7 240 197 179 165 -- --

14 257 215 197 184 -- --

30 275 231 213 200 -- --

60 325 259 230 210 -- --

90 357 276 246 227 -- --

120 387 293 259 237 -- --

183 460 348 306 277 -- --

Magnitude and probability of seasonal low flow from

March-June based on 18 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 347 256 221 197 -- --

3 360 264 227 202 -- --

7 376 277 240 214 -- --

14 402 298 258 230 -- --

30 489 335 279 241 -- --

Magnitude and probability of seasonal low flow from

November-February based on 17 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 228 182 162 149 -- --

3 248 194 170 154 -- --

7 275 207 180 166 -- --

14 299 228 199 186 -- --

30 334 251 216 201 -- --

Duration of daily mean flows based on 18 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

199 214 256 303 387 480 608 791

40% 30% 20% 15% 10% 5% 2% 1%

1,160 2,120 4,170 5,640 7,720 11,000 15,100 16,900

Magnitude and probability of annual high flow

based on 18 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 18,500 23,000 25,200 27,400 -- --

3 17,300 21,800 24,100 26,500 -- --

7 15,500 19,500 21,600 23,700 -- --

15 13,400 16,900 18,700 20,600 -- --

30 11,800 14,300 15,500 16,600 -- --

60 9,400 11,200 12,000 12,700 -- --

90 7,490 8,820 9,370 9,820 -- --

Magnitude and probability of seasonal low flow from

July-October based on 35 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 338 269 241 220 200 --

3 344 274 245 224 203 --

7 355 281 250 228 206 --

14 368 289 257 234 211 --

30 393 305 271 248 225 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 1,880 226 575 328 36

November 3,100 204 716 601 36

December 1,320 249 514 292 18

January 1,200 207 479 276 18

February 2,280 201 520 464 18

March 1,340 252 588 305 18

April 4,490 464 2,440 1,080 35

May 12,600 4,740 7,750 1,790 36

June 15,900 2,520 8,470 3,520 36

July 5,900 844 2,760 1,330 36

August 1,330 339 790 262 36

September 1,850 245 577 348 36

Annual 2,990 1,180 2,310 504 18
Statistical Summaries of Streamflow 289

12360000 Twin Creek near Hungry Horse, Mont.

Site Number 263

LOCATION.--Lat 47°59'06", long 113°33'38" (NAD 27), in E1/2 sec.25, T.26 N., R.16 W., Flathead County, Flathead National Forest, on left bank 300 ft upstream 

from road bridge, 0.1 mi upstream from mouth, and 35.9 mi southeast of Hungry Horse.

DRAINAGE AREA.--47.0 mi2.

PERIOD OF RECORD.--11 years. August 1948 to September 1956 and October 1964 to September 1967 (discontinued). 

REVISED RECORDS.--WSP 1216: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 3,585 ft (NGVD 29, revised, from river-profile map). 

REMARKS.--Water-quality records for the water years 1966-67 are published in reports of the U.S. Geological Survey.

Magnitude and probability of annual low flow

based on 10 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 9.4 6.6 5.3 4.4 -- --

3 10 7.4 5.9 4.7 -- --

7 11 8.1 6.5 5.2 -- --

14 12 8.6 7.1 6.0 -- --

30 12 9.1 7.6 6.5 -- --

60 14 10 8.1 6.7 -- --

90 18 11 8.7 7.0 -- --

120 21 12 9.4 7.4 -- --

183 25 16 12 10 -- --

Magnitude and probability of seasonal low flow from

March-June based on 11 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 16 11 8.7 7.3 -- --

3 17 12 10 8.7 -- --

7 18 14 12 11 -- --

14 22 17 15 13 -- --

30 29 22 18 16 -- --

Magnitude and probability of seasonal low flow from

November-February based on 11 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 11 7.1 5.4 4.5 -- --

3 12 7.6 5.9 4.8 -- --

7 13 8.2 6.6 5.3 -- --

14 14 8.8 7.2 6.1 -- --

30 16 9.7 7.8 6.6 -- --

Duration of daily mean flows based on 11 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

5.9 6.9 9.5 12 16 20 25 33

40% 30% 20% 15% 10% 5% 2% 1%

43 67 170 269 409 599 809 1,010

Magnitude and probability of annual high flow

based on 11 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 1,080 1,360 1,560 -- -- --

3 977 1,220 1,400 -- -- --

7 852 1,060 1,200 -- -- --

15 697 865 984 -- -- --

30 611 721 799 -- -- --

60 493 572 624 -- -- --

90 389 443 475 -- -- --

Magnitude and probability of seasonal low flow from

July-October based on 10 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 11 8.6 7.8 7.3 -- --

3 11 8.8 7.9 7.3 -- --

7 12 8.9 8.0 7.3 -- --

14 12 9.0 8.0 7.4 -- --

30 13 9.4 8.2 7.4 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 64 8.1 29 19 11

November 76 7.0 35 22 11

December 112 6.7 36 28 11

January 44 7.1 23 11 11

February 80 7.8 27 20 11

March 45 15 31 9.6 11

April 347 82 205 79 11

May 744 430 545 98 11

June 622 139 385 157 11

July 152 30 87 37 11

August 34 13 23 6.0 11

September 63 11 18 14 12

Annual 143 91 121 18 11
290 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

12361000 Sullivan Creek near Hungry Horse, Mont.

Site Number 264

LOCATION.--Lat 48°01'45", long 113°42'12" (NAD 27), in NW1⁄4SW1⁄4 sec.12, T.26 N., R.17 W., Flathead County, Hydrologic Unit 17010209, Flathead National 

Forest, on left bank 0.3 mi downstream from Quintonkon Creek, 1.7 mi upstream from Hungry Horse Reservoir flow line, and 29.5 mi southeast of Hungry 

Horse.

DRAINAGE AREA.--71.3 mi2 . 

PERIOD OF RECORD.--25 years. September 1948 to September 1956, August 1959 to September 1976 (discontinued)

REVISED RECORDS.--WSP 1216: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 3,630 ft (NGVD 29, from topographic map). 

Magnitude and probability of annual low flow

based on 23 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 23 18 15 13 -- --

3 24 19 16 14 -- --

7 26 20 18 16 -- --

14 27 22 19 17 -- --

30 30 24 21 19 -- --

60 36 26 22 19 -- --

90 44 29 24 20 -- --

120 52 34 27 22 -- --

183 62 40 31 26 -- --

Magnitude and probability of seasonal low flow from

March-June based on 25 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 38 27 22 19 17 --

3 39 28 24 21 18 --

7 41 30 26 23 21 --

14 44 32 28 25 23 --

30 59 39 32 27 23 --

Magnitude and probability of seasonal low flow from

November-February based on 24 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 26 19 16 13 -- --

3 28 20 17 14 -- --

7 31 22 19 16 -- --

14 33 24 20 17 -- --

30 39 27 22 19 -- --

Duration of daily mean flows based on 25 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

17 19 24 29 38 47 60 80

40% 30% 20% 15% 10% 5% 2% 1%

110 172 336 490 693 1,020 1,360 1,500

Magnitude and probability of annual high flow

based on 25 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 1,680 2,150 2,440 2,800 3,060 --

3 1,530 1,900 2,120 2,380 2,570 --

7 1,360 1,640 1,810 2,000 2,140 --

15 1,200 1,440 1,580 1,740 1,860 --

30 1,050 1,240 1,350 1,480 1,560 --

60 846 982 1,050 1,130 1,180 --

90 665 761 812 866 901 --

Magnitude and probability of seasonal low flow from

July-October based on 23 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 29 23 20 18 -- --

3 30 23 20 18 -- --

7 31 24 21 18 -- --

14 33 25 21 19 -- --

30 36 27 23 20 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 406 20 89 85 25

November 224 18 96 58 25

December 236 17 80 55 25

January 234 18 64 46 25

February 250 21 69 54 25

March 263 24 75 51 25

April 537 75 272 123 25

May 1,190 612 837 146 25

June 1,480 426 797 270 25

July 423 71 197 81 25

August 110 32 60 19 25

September 216 27 59 50 26

Annual 319 162 225 36 25
Statistical Summaries of Streamflow 291

12361500 Graves Creek near Hungry Horse, Mont.

Site Number 265

LOCATION.--Lat 48°07'36", long 113°48'33" (NAD 27), in SE1⁄4 sec.1, T.27 N., R.18 W., Flathead County, Flathead National Forest, on left bank 300 ft upstream 

from bridge on west shore road, 500 ft upstream from Hungry Horse Reservoir flow line, and 21.0 mi southeast of Hungry Horse.

DRAINAGE AREA.--27.0 mi2.

PERIOD OF RECORD.--11 years. August 1948 to September 1956 and October 1964 to September 1967 (discontinued). 

GAGE.--Water-stage recorder. Altitude of gage is 3,600 ft (NGVD 29, from topographic map). Prior to Oct. 1, 1951, at site 2.5 mi downstream at different datum. 

REMARKS.--Water-quality records for the water years 1966-67 are published in reports of the U.S. Geological Survey.

Magnitude and probability of annual low flow

based on 10 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 15 9.4 6.9 5.1 -- --

3 15 9.9 7.4 5.6 -- --

7 16 11 8.1 6.3 -- --

14 17 11 8.7 7.0 -- --

30 18 12 9.8 8.0 -- --

60 21 14 11 8.7 -- --

90 27 16 12 9.4 -- --

120 36 20 14 10 -- --

183 45 27 19 14 -- --

Magnitude and probability of seasonal low flow from

March-June based on 11 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 19 15 13 12 -- --

3 19 15 14 13 -- --

7 20 16 15 15 -- --

14 21 18 17 16 -- --

30 26 20 18 17 -- --

Magnitude and probability of seasonal low flow from

November-February based on 11 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 18 11 7.9 5.7 -- --

3 19 12 8.4 6.1 -- --

7 19 12 8.9 6.8 -- --

14 20 12 9.4 7.3 -- --

30 22 14 10 8.2 -- --

Duration of daily mean flows based on 11 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

8.5 9.4 13 17 22 28 35 45

40% 30% 20% 15% 10% 5% 2% 1%

63 102 200 300 430 625 812 974

Magnitude and probability of annual high flow

based on 11 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 1,000 1,290 1,530 -- -- --

3 933 1,110 1,230 -- -- --

7 833 935 991 -- -- --

15 726 821 870 -- -- --

30 628 721 771 -- -- --

60 505 577 621 -- -- --

90 401 450 478 -- -- --

Magnitude and probability of seasonal low flow from

July-October based on 10 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 18 11 8.5 6.8 -- --

3 19 12 8.9 7.1 -- --

7 19 12 9.2 7.3 -- --

14 21 13 9.5 7.5 -- --

30 24 14 10 8.0 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 168 8.9 63 53 11

November 100 8.4 60 33 11

December 133 9.0 54 38 11

January 58 11 31 14 11

February 94 11 31 23 11

March 54 18 29 10 11

April 187 36 117 52 11

May 615 248 429 103 11

June 736 358 532 126 11

July 390 70 193 96 11

August 81 24 41 18 11

September 101 13 33 25 12

Annual 168 105 135 20 11
292 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

12362500 South Fork Flathead River near Columbia Falls, Mont.

Site Number 266

LOCATION.--Lat 48°21'24", long 114°02'12" (NAD 27), in SW1⁄4SE1⁄4SW1⁄4 sec.16, T.30 N., R.19 W., Flathead County, Hydrologic Unit 17010209, on right bank 

1.7 mi downstream from Hungry Horse Dam, 6.8 mi east of Columbia Falls, and at river mile 3.5. 

DRAINAGE AREA.--1,663 mi2.

PERIOD OF RECORD.--September 1910 to January 1911 (discharge measurements only), February 1911 to September 1913 (no winter records), October 1913 

to August 1916 (sporadic daily discharge only), water years 1917-22 (annual maximum), April 1923 to November 1924 (no winter records), July to October 

1925, May to November 1927, May 1928 to April 1999. Monthly discharge only for some periods, published in WSP 1316.

REVISED RECORDS.--WSP 1216: Drainage area. WSP 1316: 1923-24(M), 1926-27(M), 1932(M), 1935-36(M). WSP 1636: 1958 (adjusted runoff).

GAGE.--Water-stage recorder. Elevation of gage is 3,040 ft (NGVD 29, levels by the Bureau of Reclamation). September 1910 to September 1916, nonrecording 

gage, Apr. 23, 1923, to Sept. 30, 1928, water-stage recorder at site 3 mi downstream at different datum. Oct. 1, 1928, to Sept. 30, 1952, water-stage recorder 

at site 1.5 mi downstream at different datum.

REMARKS.--Flow regulated by Hungry Horse Reservoir after Sept. 21, 1951. Bureau of Reclamation satellite telemeter at station.

Magnitude and probability of annual low flow

based on 46 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 156 122 108 99 89 --

3 162 125 113 104 97 --

7 199 142 122 109 98 --

14 237 153 129 114 102 --

30 349 200 154 127 103 --

60 688 340 231 167 114 --

90 1,130 559 364 247 154 --

120 1,580 861 586 411 265 --

183 2,250 1,380 1,000 740 504 --

Magnitude and probability of seasonal low flow from

March-June based on 47 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 173 133 123 118 113 --

3 190 140 127 120 114 --

7 242 155 129 121 115 --

14 338 177 132 125 122 --

30 552 238 156 141 130 --

Magnitude and probability of seasonal low flow from

November-February based on 47 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 276 156 126 109 96 --

3 340 182 140 115 99 --

7 466 234 169 131 100 --

14 739 337 218 150 106 --

30 1,400 647 410 273 167 --

Duration of daily mean flows based on 47 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

135 141 160 192 403 753 1,650 2,450

40% 30% 20% 15% 10% 5% 2% 1%

3,280 5,200 7,130 8,110 9,300 10,800 11,700 12,800

Magnitude and probability of annual high flow

based on 47 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 11,600 14,500 16,400 18,500 20,100 --

3 11,300 13,900 15,500 17,400 18,700 --

7 10,700 13,100 14,400 15,800 16,800 --

15 10,200 12,400 13,600 14,700 15,400 --

30 9,150 11,100 12,100 13,000 13,500 --

60 7,690 9,280 10,000 10,700 11,100 --

90 6,550 8,040 8,760 9,470 9,880 --

Magnitude and probability of seasonal low flow from

July-October based on 47 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 159 126 117 107 103 --

3 191 135 119 111 104 --

7 292 173 137 115 106 --

14 487 266 193 147 108 --

30 934 493 342 249 171 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 8,800 388 3,470 1,990 49

November 9,090 204 3,180 2,170 48

December 8,980 532 4,680 2,200 48

January 10,000 525 4,840 2,640 48

February 9,450 208 4,190 2,610 48

March 14,800 205 3,990 3,470 48

April 13,300 153 4,570 3,860 48

May 6,820 181 2,230 1,530 48

June 10,300 156 3,020 2,320 48

July 6,910 189 2,970 1,730 48

August 7,940 213 2,570 2,140 47

September 9,530 355 3,400 2,470 47

Annual 5,330 1,010 3,590 901 47
Statistical Summaries of Streamflow 293

12363000 Flathead River at Columbia Falls, Mont.

Site Number 267

LOCATION.--Lat 48°21'43", long 114°11'02" (NAD 27), in NW1⁄4NW1⁄4SE1⁄4 sec.17, T.30 N., R.20 W., Flathead County, Hydrologic Unit 17010208, on right 

bank 200 ft downstream from county road bridge at Columbia Falls, 5.7 mi downstream from South Fork, and at river mile 143.0.

DRAINAGE AREA.--4,464 mi2.

PERIOD OF RECORD.--May 1922 to September 1923 (fragmentary), June 1928 to current year (2002). Monthly discharge only for some periods, published in 

WSP 1316.

REVISED RECORDS.--WSP 1092: 1923. WSP 1216: Drainage area. WSP 1636: 1958 (adjusted runoff).

GAGE.--Water-stage recorder. Altitude of gage is 2,977.67 ft (NGVD 29, levels by U.S. Army Corps of Engineers). Prior to Nov. 12, 1928, nonrecording gage 

on bridge 200 ft upstream at datum 0.19 ft higher.

REMARKS.--South Fork Flathead River, which contributes about one-third of flow, is completely regulated by Hungry Horse Reservoir 10.9 mi upstream after 

Sept. 21, 1951 (see station number 12362000). Bureau of Reclamation satellite telemeter at station.

Unregulated streamflow period

Magnitude and probability of annual low flow

based on 22 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1,190 962 869 803 -- --

3 1,230 995 901 834 -- --

7 1,280 1,040 942 874 -- --

14 1,350 1,100 992 919 -- --

30 1,490 1,180 1,050 962 -- --

60 1,790 1,340 1,160 1,030 -- --

90 1,990 1,430 1,220 1,080 -- --

120 2,210 1,510 1,270 1,100 -- --

183 2,370 1,690 1,450 1,300 -- --

Magnitude and probability of seasonal low flow from

March-June based on 23 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1,630 1,220 1,080 975 -- --

3 1,670 1,250 1,100 993 -- --

7 1,750 1,300 1,130 1,020 -- --

14 1,850 1,370 1,200 1,090 -- --

30 2,310 1,640 1,400 1,230 -- --

Magnitude and probability of seasonal low flow from

November-February based on 23 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1,280 1,000 907 847 -- --

3 1,330 1,040 944 882 -- --

7 1,410 1,100 987 916 -- --

14 1,510 1,150 1,030 956 -- --

30 1,650 1,220 1,080 984 -- --

Duration of daily mean flows based on 23 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

929 1,100 1,260 1,510 1,850 2,190 2,700 3,330

40% 30% 20% 15% 10% 5% 2% 1%

4,530 7,400 15,100 21,300 29,100 41,200 55,200 65,300

Magnitude and probability of annual high flow

based on 23 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 62,000 77,500 84,900 92,100 -- --

3 58,400 72,800 79,500 85,800 -- --

7 52,200 65,200 71,600 77,900 -- --

15 45,300 57,700 64,300 71,300 -- --

30 40,200 50,300 55,400 60,700 -- --

60 33,300 40,700 44,200 47,500 -- --

90 27,100 33,200 36,000 38,700 -- --

Magnitude and probability of seasonal low flow from

July-October based on 23 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1,770 1,520 1,420 1,350 -- --

3 1,800 1,540 1,440 1,370 -- --

7 1,840 1,570 1,470 1,400 -- --

14 1,900 1,620 1,510 1,430 -- --

30 2,030 1,710 1,580 1,490 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 8,550 1,430 3,100 2,020 23

November 11,000 1,180 3,470 2,360 23

December 9,040 1,110 3,050 2,130 23

January 7,260 928 2,330 1,380 23

February 5,960 905 2,250 1,240 23

March 6,700 1,080 2,690 1,330 23

April 32,200 3,960 13,000 6,790 23

May 46,500 10,000 34,300 8,160 24

June 61,900 10,000 30,100 12,700 25

July 25,100 4,180 10,700 5,510 26

August 6,880 1,980 3,750 1,220 26

September 5,090 1,790 2,560 710 25

Annual 12,900 4,820 9,110 2,450 23
294 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

12363000 Flathead River at Columbia Falls, Mont.—Continued

Site Number 267

Regulated streamflow period

Magnitude and probability of annual low flow

based on 50 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1,910 1,280 1,040 882 735 652

3 2,010 1,350 1,100 937 780 692

7 2,200 1,510 1,250 1,060 881 779

14 2,530 1,760 1,430 1,190 960 827

30 3,000 2,090 1,670 1,370 1,070 895

60 3,830 2,810 2,300 1,920 1,530 1,300

90 4,470 3,450 2,960 2,580 2,190 1,940

120 4,860 3,800 3,280 2,890 2,470 2,220

183 5,750 4,560 3,950 3,460 2,940 2,610

Magnitude and probability of seasonal low flow from

March-June based on 51 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 2,500 1,580 1,250 1,040 853 748

3 2,710 1,700 1,340 1,100 881 762

7 2,990 1,860 1,470 1,210 981 854

14 3,660 2,270 1,770 1,440 1,140 978

30 4,760 2,890 2,210 1,760 1,350 1,130

Magnitude and probability of seasonal low flow from

November-February based on 50 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 2,250 1,480 1,170 963 764 652

3 2,420 1,600 1,260 1,030 809 684

7 2,720 1,840 1,460 1,190 928 781

14 3,120 2,150 1,700 1,380 1,070 889

30 3,660 2,460 1,950 1,590 1,240 1,040

Duration of daily mean flows based on 51 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

1,260 1,450 1,870 2,590 3,540 4,190 5,550 7,220

40% 30% 20% 15% 10% 5% 2% 1%

9,010 10,800 14,100 17,200 22,300 29,900 38,500 45,000

Magnitude and probability of annual high flow

based on 51 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 39,900 54,300 65,600 82,300 96,600 113,000

3 39,000 50,600 58,200 67,900 75,100 82,300

7 35,900 45,100 50,200 56,000 59,900 63,400

15 32,400 40,400 44,800 49,500 52,600 55,400

30 29,100 36,100 39,800 43,800 46,300 48,500

60 24,600 29,900 32,600 35,300 37,000 38,500

90 20,800 25,200 27,500 29,800 31,300 32,500

Magnitude and probability of seasonal low flow from

July-October based on 50 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 2,500 1,820 1,530 1,330 1,120 1,000

3 2,680 1,960 1,650 1,420 1,190 1,050

7 2,940 2,130 1,770 1,500 1,240 1,090

14 3,260 2,410 2,020 1,730 1,450 1,270

30 3,960 2,870 2,380 2,030 1,670 1,460

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 11,200 1,560 5,800 2,020 51

November 11,200 1,560 5,710 2,360 51

December 15,000 2,280 6,490 2,440 51

January 11,200 1,550 6,350 2,730 51

February 11,100 1,300 5,770 2,680 51

March 17,000 1,260 5,930 3,520 51

April 21,800 3,820 11,100 5,140 51

May 33,700 10,000 22,400 5,190 51

June 45,500 9,600 24,600 8,800 51

July 24,500 4,620 11,600 4,330 51

August 12,100 2,770 5,970 2,110 51

September 12,300 2,200 5,660 2,530 51

Annual 14,100 5,340 9,790 1,970 51
Statistical Summaries of Streamflow 295

12365000 Stillwater River near Whitefish, Mont.

Site Number 268

LOCATION.--Lat 48°19'08", long 114°23'11" (NAD 27), in NE1⁄4SW1⁄4 sec.34, T.30 N., R.22 W., Flathead County, Hydrologic Unit 17010210, on right bank 

600 ft downstream from road bridge, 6.2 mi southwest of Whitefish, 14.8 mi upstream from Whitefish River, and at river mile 16.2.

DRAINAGE AREA.--524 mi2.

PERIOD OF RECORD.--October and November 1930 (monthly discharge only, published in WSP 1316), December 1930 to September 1950, October 1972 to 

September 1985, April 1986 to September 1999 (seasonal records only), October 1999 to current year (2002).

REVISED RECORDS.--WSP 1736: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 2,953.26 ft (NGVD 29).

REMARKS.--Diversions for irrigation of about 200 acres upstream from station. U.S. Geological Survey satellite telemeter at station.

Magnitude and probability of annual low flow

based on 44 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 63 46 38 32 26 --

3 64 50 45 41 37 --

7 65 52 47 43 39 --

14 69 55 50 46 41 --

30 75 60 54 49 45 --

60 81 64 57 52 47 --

90 87 68 61 56 51 --

120 93 72 64 59 54 --

183 101 78 69 64 59 --

Magnitude and probability of seasonal low flow from

March-June based on 47 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 92 70 63 59 56 --

3 94 72 65 61 58 --

7 98 75 68 64 60 --

14 106 80 73 68 65 --

30 129 94 83 76 70 --

Magnitude and probability of seasonal low flow from

November-February based on 45 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 64 51 46 43 41 --

3 66 53 49 46 44 --

7 69 56 51 48 46 --

14 74 59 54 52 49 --

30 79 64 59 57 55 --

Duration of daily mean flows based on 46 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

48 52 62 72 87 104 123 154

40% 30% 20% 15% 10% 5% 2% 1%

196 301 529 732 1,000 1,400 1,960 2,240

Magnitude and probability of annual high flow

based on 46 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 1,580 2,420 2,930 3,510 3,900 --

3 1,560 2,390 2,880 3,450 3,830 --

7 1,490 2,270 2,740 3,260 3,600 --

15 1,370 2,070 2,470 2,920 3,210 --

30 1,230 1,810 2,140 2,490 2,720 --

60 1,060 1,540 1,810 2,110 2,300 --

90 888 1,290 1,520 1,760 1,920 --

Magnitude and probability of seasonal low flow from

July-October based on 48 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 91 61 46 36 26 --

3 92 64 53 44 38 --

7 92 66 54 46 40 --

14 94 68 56 48 42 --

30 99 72 60 51 45 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 271 46 114 42 49

November 300 54 128 57 49

December 582 51 121 87 46

January 495 59 114 81 46

February 588 60 115 84 47

March 548 77 161 99 47

April 1,860 138 663 394 50

May 3,120 265 1,190 580 50

June 1,920 235 870 437 50

July 952 94 379 191 50

August 505 56 178 86 50

September 315 43 125 51 50

Annual 747 124 342 140 46
296 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

12366000 Whitefish River near Kalispell, Mont.

Site Number 269

LOCATION.--Lat 48°19'13", long 114°16'39" (NAD 27), in SW1⁄4SE1⁄4NW1⁄4 sec.34, T.30 N., R.21 W., Flathead County, Hydrologic Unit 17010210, on right bank 

160 ft upstream from road bridge, 8.0 mi north of Kalispell, and at river mile 12.8.

DRAINAGE AREA.--170 mi2.

PERIOD OF RECORD.--July to November 1928, April 1929 to September 1950, annual maximum 1964, October 1972 to September 1985, April 1986 to 

September 1995, October 1995 to September 1999 (seasonal record only), October 1999 to current year (2002). Prior to 1964, published as "Whitefish Creek 

near Kalispell."

GAGE.--Water-stage recorder. Altitude of gage is 2,969.83 ft (NGVD 29). Prior to Oct. 16, 1930, nonrecording gage at site 200 ft downstream at datum 10.00 ft 

lower. Oct. 16, 1930, to Sept. 30, 1950, water-stage recorder on left bank at same datum.

REMARKS.--Some regulation by Whitefish Lake. Diversion for irrigation of about 650 acres upstream from station. U.S. Geological Survey satellite telemeter 

at station.

Magnitude and probability of annual low flow

based on 43 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 31 18 12 8.1 5.0 --

3 33 18 12 8.5 5.3 --

7 35 20 13 9.1 5.6 --

14 38 22 15 11 6.7 --

30 43 27 20 15 10 --

60 50 34 26 21 16 --

90 53 38 32 28 23 --

120 57 43 37 33 29 --

183 64 49 43 39 35 --

Magnitude and probability of seasonal low flow from

March-June based on 47 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 58 41 34 29 25 --

3 61 44 37 32 27 --

7 65 48 41 37 32 --

14 71 54 48 43 39 --

30 84 64 55 50 44 --

Magnitude and probability of seasonal low flow from

November-February based on 46 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 36 21 15 10 6.6 --

3 38 22 15 11 7.1 --

7 39 23 16 12 7.9 --

14 44 27 20 16 11 --

30 51 34 26 21 16 --

Duration of daily mean flows based on 46 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

14 19 34 43 55 66 80 97

40% 30% 20% 15% 10% 5% 2% 1%

126 179 311 417 533 715 949 1,060

Magnitude and probability of annual high flow

based on 46 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 785 1,020 1,160 1,320 1,430 --

3 778 1,010 1,150 1,310 1,420 --

7 759 989 1,120 1,280 1,380 --

15 725 945 1,070 1,220 1,320 --

30 675 874 987 1,110 1,200 --

60 575 742 832 929 990 --

90 481 624 703 788 842 --

Magnitude and probability of seasonal low flow from

July-October based on 50 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 46 22 14 8.6 4.8 3.2

3 47 23 14 9.2 5.3 3.5

7 48 24 15 9.8 5.7 3.8

14 51 27 18 13 7.9 5.6

30 59 37 27 20 14 10

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 150 10 69 27 51

November 177 20 72 30 50

December 231 23 72 38 46

January 209 14 67 36 46

February 157 16 66 30 46

March 212 48 96 39 47

April 549 83 224 95 52

May 895 214 532 171 52

June 1,190 211 609 234 52

July 695 88 275 138 52

August 238 30 111 46 53

September 149 24 81 28 53

Annual 320 89 187 55 46
Statistical Summaries of Streamflow 297

12367500 Ashley Creek near Kalispell, Mont.

Site Number 270

LOCATION.--Lat 48°08'58", long 114°25'55" (NAD 27), near center of NW1⁄4 sec.32, T.28 N., R.22 W., Flathead County, near center of span on downstream side 

of road bridge, 1.0 mi downstream from Smith Lake, 3.0 mi upstream from headgate of Ashley Irrigation District Canal, 5.6 mi west of Kalispell, and at river 

mile 26.2.

DRAINAGE AREA.--201 mi2 . 

PERIOD OF RECORD.--19 years. April 1931 to March 1933, April 1934 to September 1950, July 1969 to January 1970 (discharge measurements only), October 

1972 to September 1974 (discontinued).

GAGE.--Nonrecording gage and crest-stage gage. Altitude of gage is 3,141.43 ft (NGVD 29). Prior to July 1969, nonrecording gages at sites 1.5 mi downstream 

at different datums.

REMARKS.--Diversions for irrigation of about 100 acres. Floodwater stored in Ashley Lake (usable capacity, 20,000 acre-ft) for release during irrigation season.

Magnitude and probability of annual low flow

based on 17 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.35 0.00 0.00 0.00 -- --

3 .47 .00 .00 .00 -- --

7 .50 .00 .00 .00 -- --

14 .87 .00 .00 .00 -- --

30 1.6 .01 .00 .00 -- --

60 2.2 .62 .00 .00 -- --

90 2.8 .89 .00 .00 -- --

120 3.3 1.3 .00 .00 -- --

183 4.4 1.4 .30 .00 -- --

Magnitude and probability of seasonal low flow from

March-June based on 19 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 3.3 0.58 0.00 0.00 -- --

3 3.6 .76 .00 .00 -- --

7 4.1 .89 .00 .00 -- --

14 4.6 1.3 .54 .00 -- --

30 12 4.8 2.8 1.7 -- --

Magnitude and probability of seasonal low flow from

November-February based on 19 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 0.62 0.00 0.00 0.00 -- --

3 .83 .00 .00 .00 -- --

7 1.0 .00 .00 .00 -- --

14 1.3 .00 .00 .00 -- --

30 2.2 .08 .00 .00 -- --

Duration of daily mean flows based on 19 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

0.07 0.14 0.35 0.71 1.9 3.7 6.3 12

40% 30% 20% 15% 10% 5% 2% 1%

17 24 37 47 81 153 215 270

Magnitude and probability of annual high flow

based on 19 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 96 220 345 565 -- --

3 95 218 342 559 -- --

7 92 214 336 546 -- --

15 88 206 320 512 -- --

30 81 189 290 456 -- --

60 70 160 241 369 -- --

90 61 137 204 305 -- --

Magnitude and probability of seasonal low flow from

July-October based on 20 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1.3 0.00 0.00 0.00 -- --

3 1.7 .00 .00 .00 -- --

7 1.9 .00 .00 .00 -- --

14 2.3 .00 .00 .00 -- --

30 3.1 .04 .00 .00 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 19 0.00 6.3 6.0 20

November 22 .00 7.3 6.7 20

December 19 .00 5.6 5.3 20

January 29 .00 6.8 8.1 19

February 27 .00 6.7 8.3 19

March 66 1.7 17 14 19

April 171 5.7 67 56 19

May 484 3.9 109 116 20

June 368 1.3 78 85 21

July 115 .22 36 32 21

August 52 .00 14 13 21

September 27 .00 7.2 7.2 21

Annual 109 1.5 31 27 19
298 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

12369200 Swan River near Condon, Mont.

Site Number 271

LOCATION.--Lat 47°25'21", long 113°40'12" (NAD 27), NE1⁄4SW1⁄4NW1⁄4 sec.8, T.19 N., R.16 W., Missoula County, Hydrologic Unit 17010211, Flathead 

National Forest, on right bank 25 ft downstream from road bridge, 0.5 mi downstream from Beaver Creek, 4.5 mi downstream from Lindberg Lake, 8.1 mi 

southeast of Condon, and at river mile 75.5. 

DRAINAGE AREA.--69.1 mi2. 

PERIOD OF RECORD.--October 1972 to September 1992 (discontinued). 

REVISED RECORDS.--WDR MT-80-2: Drainage area. 

GAGE.--Water-stage recorder. Altitude of gage is 4,015 ft, (NGVD 29, by barometer). 

Magnitude and probability of annual low flow

based on 19 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 28 23 21 19 -- --

3 29 24 21 19 -- --

7 30 24 22 19 -- --

14 31 25 22 20 -- --

30 34 27 24 22 -- --

60 39 31 27 24 -- --

90 44 34 30 27 -- --

120 51 38 32 28 -- --

183 58 44 37 33 -- --

Magnitude and probability of seasonal low flow from

March-June based on 20 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 41 32 30 29 -- --

3 42 33 30 29 -- --

7 45 35 32 30 -- --

14 49 37 33 31 -- --

30 59 42 36 32 -- --

Magnitude and probability of seasonal low flow from

November-February based on 19 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 31 24 21 19 -- --

3 32 25 22 20 -- --

7 33 26 23 21 -- --

14 35 27 24 22 -- --

30 38 30 27 24 -- --

Duration of daily mean flows based on 20 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

22 24 29 35 43 52 62 77

40% 30% 20% 15% 10% 5% 2% 1%

101 160 269 345 437 557 733 891

Magnitude and probability of annual high flow

based on 20 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 807 1,010 1,140 1,290 -- --

3 760 955 1,080 1,240 -- --

7 697 888 1,010 1,180 -- --

15 619 785 896 1,040 -- --

30 550 671 745 835 -- --

60 471 568 626 695 -- --

90 406 489 537 592 -- --

Magnitude and probability of seasonal low flow from

July-October based on 19 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 38 28 23 19 -- --

3 39 28 23 20 -- --

7 40 29 24 20 -- --

14 42 30 24 21 -- --

30 46 32 27 22 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 104 21 58 23 20

November 158 21 69 35 20

December 158 29 62 33 20

January 122 25 52 24 20

February 87 31 49 18 20

March 207 33 72 40 20

April 373 59 209 75 20

May 626 270 414 102 20

June 876 231 486 156 20

July 454 108 269 124 20

August 157 38 100 40 20

September 177 21 69 33 20

Annual 219 106 159 35 20
Statistical Summaries of Streamflow 299

12370000 Swan River near Bigfork, Mont.

Site Number 272

LOCATION.--Lat 48°01'28", long 113°58'44" (NAD 27), near center of S1⁄2SW1⁄4 sec.11, T.26 N., R.19 W., Lake County, Hydrologic Unit 17010211, on left bank 

0.2 mi downstream from Johnson Creek, 0.4 mi downstream from Swan Lake, 5.1 mi southeast of Bigfork, and at river mile 14.0.

DRAINAGE AREA.--671 mi2.

PERIOD OF RECORD.--October 1910 to May 1911 (gage heights only), April 1922 to current year (2002). Monthly discharge only for some periods, published 

in WSP 1316.

REVISED RECORDS.--WSP 1216: Drainage area. WSP 1246: 1923-24(M), 1930. WSP 1316: 1923.

GAGE.--Water-stage recorder. Altitude of gage is 3,062.6 ft (NGVD 29, from river-profile survey). Oct. 10, 1910, to May 22, 1911, nonrecording gage at site 

10 mi upstream at different datum. Apr. 28, 1922, to Oct. 14, 1930, nonrecording gage at site 800 ft upstream at datum 1.9 ft higher.

REMARKS.--Diversions for irrigation of about 360 acres upstream from station. U.S. Geological Survey satellite telemeter at station. 

Magnitude and probability of annual low flow

based on 79 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 343 290 265 244 223 209

3 348 293 267 246 223 209

7 356 299 272 250 226 211

14 370 309 280 256 231 216

30 389 324 293 269 243 227

60 422 352 319 295 270 254

90 447 371 339 316 293 279

120 472 386 351 327 303 290

183 502 404 366 340 314 300

Magnitude and probability of seasonal low flow from

March-June based on 80 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 433 339 303 277 253 239

3 438 343 306 281 256 242

7 450 351 312 286 261 246

14 472 365 323 294 267 251

30 557 413 357 317 279 257

Magnitude and probability of seasonal low flow from

November-February based on 80 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 356 297 273 255 237 226

3 362 301 275 256 237 226

7 373 308 281 262 242 230

14 388 319 291 270 249 237

30 410 335 304 281 259 246

Duration of daily mean flows based on 80 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

274 283 312 360 427 487 561 669

40% 30% 20% 15% 10% 5% 2% 1%

806 1,130 1,850 2,320 2,910 3,810 4,820 5,660

Magnitude and probability of annual high flow

based on 80 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 4,940 6,180 6,920 7,790 8,400 8,970

3 4,810 6,010 6,730 7,570 8,150 8,710

7 4,480 5,610 6,300 7,110 7,680 8,230

15 4,060 5,110 5,760 6,550 7,110 7,660

30 3,670 4,550 5,080 5,720 6,170 6,610

60 3,170 3,830 4,210 4,620 4,910 5,160

90 2,710 3,280 3,610 3,970 4,210 4,430

Magnitude and probability of seasonal low flow from

July-October based on 80 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 414 335 300 275 249 233

3 417 338 304 279 254 239

7 423 343 309 284 259 244

14 433 351 316 291 265 250

30 450 364 329 304 279 264

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 1,680 308 551 217 80

November 1,510 290 595 238 80

December 1,800 307 569 263 80

January 1,300 271 498 171 80

February 1,630 236 499 214 80

March 1,810 244 626 268 80

April 3,230 675 1,520 569 80

May 5,470 1,670 2,840 752 81

June 5,800 1,430 3,300 1,030 81

July 3,310 609 1,640 645 81

August 1,220 322 698 215 81

September 1,100 285 536 175 81

Annual 1,860 607 1,160 266 80
300 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

12371100 Hell Roaring Creek near Polson, Mont.

Site Number 273

LOCATION.--Lat 47°42'10", long 114°02'50" (NAD 27), in NW1⁄4NW1⁄4 sec.4, T.22 N., R.19 W., Lake County, on left bank just downstream from powerplant, 

0.75 mi upstream from mouth, and 7 mi east of Polson.

DRAINAGE AREA.--6.22 mi2 (revised).

PERIOD OF RECORD.--20 years (1917-37).

GAGE.--Water-stage recorder and concrete control. Altitude of gage is 3,150 ft (NGVD 29, by barometer).

REMARKS.--Records include water diverted by the Flathead irrigation project canal for irrigation of lands downstream. Flow regulated by powerplant and two 

reservoirs with a combined capacity of about 200 acre-ft.

Magnitude and probability of annual low flow

based on 14 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 2.4 1.9 1.7 1.5 -- --

3 2.9 2.4 2.2 2.0 -- --

7 3.1 2.6 2.3 2.1 -- --

14 3.3 2.8 2.5 2.3 -- --

30 3.5 3.1 2.9 2.7 -- --

60 3.9 3.6 3.4 3.3 -- --

90 4.3 3.9 3.7 3.6 -- --

120 4.4 4.0 3.8 3.6 -- --

183 4.6 4.3 4.1 4.0 -- --

Magnitude and probability of seasonal low flow from

March-June based on 15 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 2.6 2.0 1.8 1.6 -- --

3 3.2 2.6 2.4 2.2 -- --

7 3.5 2.9 2.6 2.3 -- --

14 3.7 3.0 2.7 2.5 -- --

30 3.9 3.2 3.0 2.8 -- --

Magnitude and probability of seasonal low flow from

November-February based on 15 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 2.7 2.2 1.9 1.7 -- --

3 3.3 2.6 2.3 2.0 -- --

7 3.5 2.9 2.6 2.3 -- --

14 3.8 3.3 3.1 3.0 -- --

30 4.0 3.7 3.5 3.4 -- --

Duration of daily mean flows based on 15 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

2.4 2.8 3.0 3.4 4.0 4.4 4.8 5.2

40% 30% 20% 15% 10% 5% 2% 1%

5.6 6.4 7.5 8.1 13 21 30 36

Magnitude and probability of annual high flow

based on 15 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 29 46 55 65 -- --

3 24 39 49 63 -- --

7 21 35 45 58 -- --

15 18 29 37 48 -- --

30 15 24 31 40 -- --

60 12 19 24 31 -- --

90 10 16 20 27 -- --

Magnitude and probability of seasonal low flow from

July-October based on 15 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 2.8 2.1 1.8 1.6 -- --

3 3.3 2.7 2.5 2.3 -- --

7 3.7 3.0 2.7 2.4 -- --

14 3.9 3.2 2.9 2.7 -- --

30 4.2 3.5 3.2 3.0 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 8.5 3.0 5.0 1.5 15

November 6.8 3.9 5.2 .86 15

December 8.2 4.1 5.2 1.1 15

January 7.1 3.4 4.7 1.0 15

February 5.8 3.5 4.5 .65 15

March 6.4 3.2 4.3 .87 15

April 14 2.9 7.2 3.4 15

May 32 5.2 13 7.7 15

June 33 4.1 14 9.6 16

July 18 3.3 7.3 4.0 16

August 9.2 3.5 5.8 1.6 17

September 7.6 3.1 5.3 1.2 16

Annual 10 4.4 6.6 1.7 15
Statistical Summaries of Streamflow 301

12372000 Flathead River near Polson, Mont.

Site Number 274

LOCATION.--Lat 47°40'49", long 114°14'45" (NAD 27), in SW1⁄4NE1⁄4SE1⁄4 sec.11, T.22 N., R.21 W., Lake County, Hydrologic Unit 17010212, on left bank 

0.5 mi downstream from Kerr Dam, 4.0 mi west of Polson, 5.0 mi downstream from Flathead Lake, and at river mile 71.5.

DRAINAGE AREA.--7,096 mi2.

PERIOD OF RECORD.--July 1907 to current year (2002).

REVISED RECORDS.--WSP 652: 1926. WSP 752: 1932. WSP 1182: 1948. WSP 1216: Drainage area. WSP 1246: 1928(M). WSP 1636: 1958 (adjusted 

runoff).

GAGE.--Water-stage recorder. Altitude of gage is 2,692.70 ft (NGVD 29, levels by The Montana Power Co.). Prior to Oct. 1, 1941, nonrecording gages or waterstage recorder at several sites near highway bridge at old site of Michell's Ferry 6 mi downstream from present site, all at datum 2,629.20 ft (from river-profile 

survey).

REMARKS.--Flow regulated by Flathead Lake (Kerr Dam) after April 1938 (station number 12371500) and Hungry Horse Reservoir (station number 12362000) 

since September 1951. Diversions upstream from station for irrigation of about 10,000 acres. Flathead project pumps can divert up to 12,000 acre-ft per month 

when required for irrigation of lands downstream from station. U.S.Geological Survey satellite telemeter at station. 

Unregulated streamflow period

Magnitude and probability of annual low flow

based on 41 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 2,370 1,760 1,490 1,250 1,050 --

3 2,390 1,830 1,560 1,350 1,140 --

7 2,470 1,940 1,700 1,520 1,330 --

14 2,550 2,030 1,800 1,620 1,440 --

30 2,710 2,150 1,890 1,700 1,500 --

60 3,080 2,410 2,090 1,860 1,610 --

90 3,460 2,620 2,250 1,990 1,720 --

120 3,710 2,750 2,360 2,070 1,800 --

183 4,260 3,190 2,740 2,420 2,110 --

Magnitude and probability of seasonal low flow from

March-June based on 43 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 2,970 2,090 1,760 1,470 1,180 --

3 3,010 2,150 1,790 1,540 1,290 --

7 3,090 2,270 1,950 1,720 1,500 --

14 3,180 2,370 2,050 1,830 1,620 --

30 3,420 2,500 2,150 1,900 1,670 --

Magnitude and probability of seasonal low flow from

November-February based on 43 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 2,800 1,910 1,520 1,350 1,100 --

3 2,830 2,040 1,710 1,470 1,230 --

7 2,900 2,140 1,840 1,620 1,410 --

14 2,980 2,220 1,930 1,740 1,550 --

30 3,110 2,310 2,010 1,810 1,630 --

Duration of daily mean flows based on 43 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

1,650 1,850 2,270 2,580 3,200 3,820 4,520 5,570

40% 30% 20% 15% 10% 5% 2% 1%

7,270 10,300 16,900 23,900 32,300 43,700 55,300 65,000

Magnitude and probability of annual high flow

based on 43 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 49,700 62,600 69,000 75,400 79,100 --

3 49,500 62,600 68,900 75,000 78,500 --

7 48,800 61,900 67,900 73,400 76,300 --

15 47,100 59,900 65,700 70,800 73,500 --

30 43,800 55,200 60,000 64,000 66,000 --

60 37,400 45,800 48,700 50,800 51,700 --

90 30,800 37,600 40,000 41,800 42,500 --

Magnitude and probability of seasonal low flow from

July-October based on 43 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 3,150 2,310 1,960 1,700 1,450 --

3 3,280 2,530 2,220 1,990 1,770 --

7 3,380 2,680 2,390 2,200 2,010 --

14 3,470 2,780 2,510 2,320 2,140 --

30 3,650 2,970 2,710 2,540 2,370 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 10,900 2,280 4,560 1,830 44

November 13,400 1,900 4,660 2,310 43

December 11,600 1,670 4,860 2,690 43

January 14,800 1,560 5,090 3,450 43

February 12,000 1,600 4,290 2,520 43

March 8,960 1,520 3,920 1,740 43

April 22,300 2,630 8,180 4,590 44

May 49,200 5,960 28,400 9,820 44

June 64,400 10,000 38,700 13,400 44

July 55,600 4,760 20,200 10,600 44

August 17,500 3,350 7,920 3,150 45

September 11,100 2,690 4,990 1,620 45

Annual 17,200 5,200 11,200 2,910 43
302 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

12372000 Flathead River near Polson, Mont.—Continued

Site Number 274

Regulated streamflow period

Magnitude and probability of annual low flow

based on 50 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 2,950 1,760 1,060 623 297 167

3 3,050 2,030 1,590 1,270 966 795

7 3,420 2,390 1,930 1,600 1,270 1,080

14 3,930 2,840 2,340 1,960 1,580 1,360

30 4,750 3,580 3,000 2,560 2,100 1,820

60 5,730 4,540 3,950 3,480 2,990 2,680

90 6,740 5,370 4,680 4,140 3,570 3,220

120 7,390 5,900 5,140 4,530 3,890 3,480

183 8,410 7,010 6,250 5,630 4,950 4,510

Magnitude and probability of seasonal low flow from

March-June based on 51 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 4,990 3,200 2,510 2,050 1,620 1,380

3 5,670 3,680 2,880 2,340 1,830 1,550

7 6,080 4,000 3,180 2,610 2,080 1,780

14 6,540 4,520 3,730 3,180 2,670 2,370

30 7,440 5,240 4,360 3,760 3,170 2,840

Magnitude and probability of seasonal low flow from

November-February based on 50 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 4,380 2,940 2,300 1,830 1,390 1,140

3 5,300 3,920 3,280 2,800 2,310 2,020

7 6,000 4,500 3,800 3,280 2,750 2,430

14 6,610 5,040 4,310 3,760 3,200 2,860

30 7,550 5,830 5,000 4,360 3,710 3,300

Duration of daily mean flows based on 51 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

2,340 3,090 3,780 4,750 6,330 7,480 8,630 9,850

40% 30% 20% 15% 10% 5% 2% 1%

11,100 12,600 15,300 16,700 21,500 29,900 40,400 46,400

Magnitude and probability of annual high flow

based on 51 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 39,800 51,000 55,500 59,100 60,700 62,600

3 38,400 49,800 54,600 58,500 60,500 62,500

7 35,100 46,600 52,100 57,200 60,100 62,300

15 31,600 42,800 48,800 55,000 58,800 62,100

30 28,100 38,000 43,500 49,300 53,100 56,300

60 23,000 30,500 34,800 39,700 42,900 45,900

90 19,700 25,700 29,200 33,200 36,000 38,600

Magnitude and probability of seasonal low flow from

July-October based on 50 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 3,170 1,920 1,150 660 305 197

3 3,320 2,190 1,690 1,330 989 827

7 3,740 2,590 2,070 1,700 1,340 1,130

14 4,270 3,000 2,430 2,020 1,610 1,410

30 5,090 3,750 3,130 2,670 2,200 1,920

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 14,000 3,710 8,200 2,140 51

November 12,900 3,360 9,270 2,190 51

December 16,300 5,710 10,400 2,230 51

January 16,500 5,560 10,600 2,470 51

February 17,300 3,710 10,300 3,290 51

March 23,300 2,330 9,260 3,910 51

April 22,200 3,770 10,500 4,800 51

May 33,500 5,200 18,100 7,680 51

June 49,800 6,400 25,700 10,400 51

July 29,900 5,220 14,000 5,180 51

August 11,700 2,340 6,520 2,150 51

September 12,000 3,010 6,890 2,120 51

Annual 17,000 6,450 11,600 2,450 51
Statistical Summaries of Streamflow 303

12374250 Mill Creek above Bassoo Creek, near Niarada, Mont.

Site Number 275

LOCATION.--Lat 47°49'47", long 114°41'48" (NAD 27), in SE1⁄4NW1⁄4NE1⁄4 sec.20, T.24 N., R.24 W., Sanders County, Hydrologic Unit 17010212, Flathead 

Indian Reservation, on right bank 0.3 mi upstream from Bassoo Creek, and 4.1 mi northwest of Niarada.

DRAINAGE AREA.--19.6 mi2.

PERIOD OF RECORD.--October 1982 to current year (2002).

GAGE.--Water-stage recorder and crest-stage gage. Altitude of gage is 3,000 ft (NGVD 29). Prior to Sept. 23, 1987, at site 305 ft downstream at different datum. 

Prior to July 23, 1991, at site 275 ft downstream at different datum.

REMARKS.-- No known regulation or diversion upstream from station. 

Magnitude and probability of annual low flow

based on 19 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1.5 1.3 1.3 1.2 -- --

3 1.7 1.4 1.4 1.3 -- --

7 1.8 1.6 1.5 1.4 -- --

14 2.0 1.7 1.6 1.5 -- --

30 2.1 1.8 1.7 1.6 -- --

60 2.3 1.9 1.8 1.6 -- --

90 2.4 2.0 1.9 1.7 -- --

120 2.5 2.1 2.0 1.8 -- --

183 2.7 2.2 2.0 1.9 -- --

Magnitude and probability of seasonal low flow from

March-June based on 20 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 2.9 1.9 1.5 1.3 -- --

3 3.0 1.9 1.6 1.4 -- --

7 3.2 2.1 1.7 1.5 -- --

14 3.6 2.4 2.0 1.7 -- --

30 4.9 3.1 2.5 2.1 -- --

Magnitude and probability of seasonal low flow from

November-February based on 20 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1.7 1.4 1.3 1.2 -- --

3 1.8 1.5 1.4 1.3 -- --

7 2.0 1.7 1.5 1.4 -- --

14 2.1 1.8 1.6 1.6 -- --

30 2.3 1.9 1.8 1.7 -- --

Duration of daily mean flows based on 20 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

1.5 1.6 1.9 2.1 2.3 2.6 3.0 3.6

40% 30% 20% 15% 10% 5% 2% 1%

4.5 6.7 12 15 21 31 46 62

Magnitude and probability of annual high flow

based on 20 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 40 72 99 142 -- --

3 38 67 91 129 -- --

7 34 59 79 110 -- --

15 30 49 64 88 -- --

30 26 42 55 76 -- --

60 21 35 46 63 -- --

90 18 29 38 52 -- --

Magnitude and probability of seasonal low flow from

July-October based on 19 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 2.0 1.7 1.5 1.4 -- --

3 2.1 1.7 1.6 1.4 -- --

7 2.1 1.8 1.6 1.5 -- --

14 2.2 1.9 1.7 1.5 -- --

30 2.3 2.0 1.8 1.6 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 5.1 1.9 2.7 0.70 20

November 8.6 2.0 3.5 1.6 20

December 17 2.1 3.6 3.3 20

January 9.8 1.9 3.3 1.9 20

February 14 1.7 3.9 3.1 20

March 35 2.5 7.5 7.4 20

April 50 5.0 21 14 20

May 87 11 26 17 20

June 38 4.9 16 9.3 20

July 13 2.5 5.8 2.9 20

August 5.6 1.9 3.1 .97 21

September 3.4 1.5 2.5 .50 20

Annual 19 3.9 8.2 4.1 20
304 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

12375900 South Crow Creek near Ronan, Mont.

Site Number 276

LOCATION.--Lat 47°29'30", long 114°01'33" (NAD 27), in NW1⁄4NE1⁄4SW1⁄4 sec.16, T.20 N., R.19 W., Lake County, Hydrologic Unit 17010212, Flathead Indian 

Reservation, on right bank 200 ft upstream from Pablo Feeder Canal, 2.2 mi northeast of Kicking Horse Reservoir, 4.5 mi southeast of Ronan, and at river 

mile 2.6.

DRAINAGE AREA.--7.57 mi2.

PERIOD OF RECORD.--October 1982 to current year (2002).

GAGE.--Water-stage recorder. Altitude of gage is 3,320 ft (NGVD 29).

REMARKS.--No known regulation or diversion upstream from station. 

Magnitude and probability of annual low flow

based on 19 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 5.1 4.6 4.3 4.1 -- --

3 5.3 4.8 4.6 4.4 -- --

7 5.5 5.0 4.8 4.6 -- --

14 5.8 5.2 5.0 4.8 -- --

30 6.1 5.5 5.3 5.1 -- --

60 6.5 5.8 5.5 5.2 -- --

90 6.9 6.0 5.7 5.5 -- --

120 7.3 6.3 5.9 5.7 -- --

183 8.0 6.8 6.3 5.9 -- --

Magnitude and probability of seasonal low flow from

March-June based on 20 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 5.9 5.2 5.0 4.8 -- --

3 6.1 5.4 5.1 4.9 -- --

7 6.3 5.6 5.3 5.0 -- --

14 6.7 5.8 5.4 5.2 -- --

30 7.5 6.4 5.9 5.6 -- --

Magnitude and probability of seasonal low flow from

November-February based on 20 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 5.2 4.6 4.3 4.1 -- --

3 5.4 4.8 4.6 4.4 -- --

7 5.7 5.1 4.8 4.6 -- --

14 5.9 5.3 5.0 4.8 -- --

30 6.2 5.5 5.3 5.1 -- --

Duration of daily mean flows based on 20 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

4.4 4.7 5.7 6.1 6.9 7.6 8.7 10

40% 30% 20% 15% 10% 5% 2% 1%

12 16 29 40 55 74 93 119

Magnitude and probability of annual high flow

based on 20 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 130 193 236 294 -- --

3 111 157 189 231 -- --

7 95 127 149 177 -- --

15 83 106 122 141 -- --

30 75 93 103 116 -- --

60 62 77 85 95 -- --

90 50 62 68 76 -- --

Magnitude and probability of seasonal low flow from

July-October based on 19 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 7.4 6.3 5.8 5.4 -- --

3 7.5 6.5 6.0 5.7 -- --

7 7.7 6.7 6.2 5.8 -- --

14 7.8 6.8 6.3 5.9 -- --

30 8.1 6.9 6.4 6.0 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 14 6.1 9.2 2.3 20

November 19 6.3 9.6 3.3 20

December 15 5.8 7.9 2.2 20

January 11 5.4 7.2 1.5 20

February 10 5.0 6.7 1.3 20

March 13 4.9 7.9 1.7 20

April 25 8.8 16 4.5 20

May 69 25 45 12 20

June 104 36 68 19 20

July 74 16 37 18 20

August 22 7.9 14 4.1 20

September 20 6.9 9.6 3.0 20

Annual 27 14 20 4.1 20
Statistical Summaries of Streamflow 305

12377150 Mission Creek above reservoir, near St. Ignatius, Mont.

Site Number 277

LOCATION.--Lat 47°19'23", long 113°58'43" (NAD 27), in NW1⁄4SW1⁄4NE1⁄4 sec.14, T.18 N., R.19 W., Lake County, Hydrologic Unit 17010212, Flathead Indian 

Reservation, on right bank, 0.2 mi southwest of upper Bureau of Indian Affairs campground, 0.5 mi upstream from Mission Reservoir, and 5.3 mi east of 

St. Ignatius.

DRAINAGE AREA.--12.4 mi2.

PERIOD OF RECORD.--October 1982 to current year (2002).

GAGE.--Water-stage recorder. Altitude of gage is 3,460 ft (NGVD 29).

REMARKS.--No known regulation or diversions upstream from station. 

Magnitude and probability of annual low flow

based on 19 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 7.1 6.4 6.0 5.7 -- --

3 7.3 6.7 6.4 6.2 -- --

7 7.7 7.1 6.7 6.5 -- --

14 8.1 7.4 7.0 6.7 -- --

30 8.5 7.8 7.4 7.1 -- --

60 9.6 8.6 8.2 7.9 -- --

90 11 9.6 9.2 8.9 -- --

120 13 11 10 9.9 -- --

183 18 15 13 12 -- --

Magnitude and probability of seasonal low flow from

March-June based on 20 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 8.0 7.1 6.7 6.4 -- --

3 8.2 7.3 6.9 6.7 -- --

7 8.5 7.5 7.1 6.8 -- --

14 9.1 8.0 7.5 7.1 -- --

30 10 8.9 8.2 7.7 -- --

Magnitude and probability of seasonal low flow from

November-February based on 20 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 7.3 6.4 6.0 5.7 -- --

3 7.6 6.8 6.5 6.2 -- --

7 8.0 7.2 6.9 6.6 -- --

14 8.3 7.5 7.1 6.8 -- --

30 8.7 7.9 7.5 7.2 -- --

Duration of daily mean flows based on 20 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

6.3 6.8 8.2 9.2 11 14 17 23

40% 30% 20% 15% 10% 5% 2% 1%

30 44 77 106 139 186 254 302

Magnitude and probability of annual high flow

based on 20 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 353 417 450 483 -- --

3 301 359 389 420 -- --

7 258 311 341 374 -- --

15 222 266 291 318 -- --

30 193 224 241 259 -- --

60 163 188 201 215 -- --

90 134 156 167 180 -- --

Magnitude and probability of seasonal low flow from

July-October based on 19 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 19 15 13 12 -- --

3 19 15 14 12 -- --

7 20 16 14 12 -- --

14 21 16 14 13 -- --

30 22 17 15 13 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 37 14 25 7.7 20

November 28 12 19 4.7 20

December 21 10 13 2.6 20

January 15 8.2 11 1.7 20

February 13 6.7 9.0 1.4 20

March 15 7.2 11 1.9 20

April 44 11 26 9.7 20

May 168 54 101 29 20

June 222 104 173 33 20

July 180 53 116 41 20

August 75 25 49 15 20

September 67 16 30 11 20

Annual 61 36 49 7.6 20
306 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

12381400 South Fork Jocko River near Arlee, Mont.

Site Number 278

LOCATION.--Lat 47°11'44", long 113°50'59" (NAD 27), in NE1⁄4NW1⁄4NE1⁄4 sec.35, T.17 N., R.18 W., Lake County, Hydrologic Unit 17010212, Flathead Indian 

Reservation, on right bank 600 ft upstream from confluence with Jocko River and Twin Campground and 12 mi northeast of Arlee.

DRAINAGE AREA.--56.0 mi2.

PERIOD OF RECORD.--October 1982 to current year (2002). Records published as "near Jocko" 1912-16 and in WSP 1246, 1316 are not equivalent.

GAGE.--Water-stage recorder. Altitude of gage is 3,970 ft (NGVD 29).

REMARKS.--No known regulation or diversion upstream from station. U.S. Geological Survey telemeter at station.

Magnitude and probability of annual low flow

based on 19 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 4.2 3.0 2.5 2.1 -- --

3 4.6 3.4 2.9 2.5 -- --

7 5.6 4.1 3.5 3.0 -- --

14 7.0 5.3 4.5 3.8 -- --

30 8.4 6.1 5.1 4.3 -- --

60 10 7.3 6.1 5.2 -- --

90 11 8.6 7.8 7.2 -- --

120 13 10 9.4 8.8 -- --

183 16 13 12 11 -- --

Magnitude and probability of seasonal low flow from

March-June based on 20 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 8.1 5.9 5.2 4.8 -- --

3 8.8 6.4 5.7 5.3 -- --

7 9.5 6.9 6.1 5.6 -- --

14 10 7.9 7.3 7.0 -- --

30 12 9.4 8.9 8.6 -- --

Magnitude and probability of seasonal low flow from

November-February based on 20 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 4.5 3.1 2.5 2.2 -- --

3 5.0 3.5 2.9 2.5 -- --

7 6.2 4.4 3.6 3.0 -- --

14 7.8 5.6 4.6 3.9 -- --

30 9.0 6.3 5.2 4.4 -- --

Duration of daily mean flows based on 20 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

4.3 5.3 7.2 9.4 13 16 19 24

40% 30% 20% 15% 10% 5% 2% 1%

31 46 83 114 158 233 337 413

Magnitude and probability of annual high flow

based on 20 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 346 510 639 827 -- --

3 326 475 590 757 -- --

7 303 428 519 644 -- --

15 269 370 443 541 -- --

30 233 322 390 488 -- --

60 185 250 299 368 -- --

90 151 200 235 284 -- --

Magnitude and probability of seasonal low flow from

July-October based on 19 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 17 15 13 13 -- --

3 18 15 14 13 -- --

7 18 15 14 13 -- --

14 19 16 14 13 -- --

30 20 17 15 14 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 42 13 22 6.1 20

November 26 11 18 4.3 20

December 37 9.3 15 6.8 20

January 22 3.7 12 5.1 20

February 23 4.4 10 4.1 20

March 56 7.7 15 10 20

April 113 25 56 29 20

May 459 118 197 73 20

June 446 70 192 92 20

July 140 37 77 27 20

August 54 22 38 9.3 20

September 44 16 26 7.0 20

Annual 108 35 57 17 20
Statistical Summaries of Streamflow 307

12383500 Big Knife Creek near Arlee, Mont.

Site Number 279

LOCATION.--Lat 47°08'51", long 113°58'24" (NAD 27), in NW1⁄4SW1⁄4NW/4 sec.14, T.16 N., R.19 W., Lake County, Hydrologic Unit 17010212, Flathead 

Indian Reservation, on left bank, 150 ft upstream from S Canal, 1 mi upstream from mouth, and 5.5 mi east of Arlee.

DRAINAGE AREA.--6.88 mi2.

PERIOD OF RECORD.--August 1910 to September 1916 (no winter records), October 1982 to current year (2002). Monthly discharge only for some periods, 

published in WSP 1316. Published as "near Jocko" 1910-16 and in WSP 916, and as "above Big Knife Canal, near Jocko" in WSP 1246, 1316.

REVISED RECORDS.--WSP 1246: 1916. WSP 1316: 1910-12, 1915-16.

GAGE.--Water-stage recorder and crest-stage gage. Altitude of gage is 3,720 ft (NGVD 29). Prior to July 28, 1998, at site 38 ft upstream at different datum.

REMARKS.-- No known regulation or diversion upstream from station. 

Magnitude and probability of annual low flow

based on 19 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 3.5 2.7 2.2 1.9 -- --

3 3.6 2.9 2.5 2.2 -- --

7 3.8 3.2 2.8 2.5 -- --

14 4.0 3.5 3.2 2.9 -- --

30 4.1 3.6 3.4 3.1 -- --

60 4.5 4.0 3.7 3.5 -- --

90 5.1 4.5 4.1 3.9 -- --

120 5.5 4.8 4.4 4.1 -- --

183 6.8 5.9 5.4 5.0 -- --

Magnitude and probability of seasonal low flow from

March-June based on 20 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 3.8 3.3 3.1 3.0 -- --

3 3.9 3.4 3.2 3.0 -- --

7 4.0 3.5 3.3 3.1 -- --

14 4.1 3.6 3.4 3.2 -- --

30 4.3 3.7 3.5 3.3 -- --

Magnitude and probability of seasonal low flow from

November-February based on 20 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 3.7 2.7 2.3 1.9 -- --

3 3.8 3.0 2.6 2.2 -- --

7 4.1 3.4 2.9 2.6 -- --

14 4.3 3.7 3.4 3.1 -- --

30 4.5 3.9 3.6 3.4 -- --

Duration of daily mean flows based on 20 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

3.0 3.2 3.8 4.3 5.1 5.9 7.1 8.4

40% 30% 20% 15% 10% 5% 2% 1%

10 13 16 20 24 31 41 46

Magnitude and probability of annual high flow

based on 20 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 36 49 56 64 -- --

3 35 47 53 60 -- --

7 32 43 50 57 -- --

15 29 39 46 53 -- --

30 26 35 40 45 -- --

60 23 30 34 38 -- --

90 20 26 29 32 -- --

Magnitude and probability of seasonal low flow from

July-October based on 23 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 7.6 6.5 5.8 5.2 -- --

3 7.6 6.5 5.8 5.2 -- --

7 7.8 6.5 5.8 5.3 -- --

14 7.9 6.7 6.0 5.5 -- --

30 8.2 7.0 6.4 5.8 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 10 5.3 8.2 1.4 24

November 8.9 4.5 6.9 1.2 22

December 8.4 4.1 5.9 1.1 21

January 6.3 3.7 5.1 .79 20

February 6.5 3.0 4.5 .79 20

March 7.1 3.0 4.5 .90 20

April 8.9 3.9 6.1 1.5 22

May 28 9.0 15 4.1 25

June 48 8.5 28 9.7 26

July 55 9.6 21 8.7 26

August 28 8.1 14 3.7 27

September 18 6.6 10 2.2 27

Annual 15 6.6 10 2.0 20
308 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

12388200 Jocko River at Dixon, Mont.

Site Number 280

LOCATION.--Lat 47°18'43", long 114°17'48" (NAD 27), in NW1⁄4NW1⁄4NE1⁄4 sec.20, T.18 N., R.21 W., Sanders County, Hydrologic Unit 17010212, Flathead 

Indian Reservation, on right bank 38 ft downstream from State Highway 212 bridge, 0.8 mi east of Dixon, and at river mile 0.8.

DRAINAGE AREA.--380 mi2.

PERIOD OF RECORD.--April 1990 to current year (2002). Miscellaneous measurements made at this site 1977 and 1987 water years.

GAGE.--Water-stage recorder. Altitude of gage is 2,521.87 ft (NGVD 29).

REMARKS.--Some regulation and diversion upstream from gage for irrigation.

Magnitude and probability of annual low flow

based on 11 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 97 85 79 74 -- --

3 101 90 83 77 -- --

7 108 97 91 85 -- --

14 112 104 100 96 -- --

30 117 108 105 102 -- --

60 122 114 111 110 -- --

90 132 121 116 113 -- --

120 142 128 123 118 -- --

183 155 140 133 127 -- --

Magnitude and probability of seasonal low flow from

March-June based on 12 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 113 102 98 96 -- --

3 115 103 100 98 -- --

7 119 108 105 103 -- --

14 124 113 110 109 -- --

30 135 121 117 115 -- --

Magnitude and probability of seasonal low flow from

November-February based on 12 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 97 86 80 75 -- --

3 102 90 84 78 -- --

7 109 98 92 86 -- --

14 114 105 100 96 -- --

30 118 108 105 102 -- --

Duration of daily mean flows based on 12 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

94 97 103 115 134 147 160 173

40% 30% 20% 15% 10% 5% 2% 1%

186 220 262 315 405 633 947 1,230

Magnitude and probability of annual high flow

based on 12 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 683 1,170 1,600 -- -- --

3 649 1,100 1,500 -- -- --

7 601 1,000 1,340 -- -- --

15 540 914 1,240 -- -- --

30 495 846 1,160 -- -- --

60 420 695 936 -- -- --

90 355 565 749 -- -- --

Magnitude and probability of seasonal low flow from

July-October based on 12 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 148 132 125 120 -- --

3 149 133 126 121 -- --

7 152 134 127 122 -- --

14 157 138 130 123 -- --

30 164 143 134 127 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 227 145 184 25 12

November 227 138 175 27 12

December 265 123 158 38 12

January 188 102 133 23 12

February 208 108 131 29 12

March 246 118 149 38 12

April 390 130 222 87 13

May 1,300 203 425 283 13

June 1,540 149 562 387 13

July 512 140 271 104 13

August 228 131 174 30 13

September 225 137 181 24 13

Annual 445 157 228 82 12
Statistical Summaries of Streamflow 309

12388400 Revais Creek below West Fork, near Dixon, Mont.

Site Number 281

LOCATION.--Lat 47°15'59", long 114°24'21" (NAD 27), in SE1⁄4NE1⁄4NW1⁄4 sec.4, T.17 N., R.22 W., Sanders County, Hydrologic Unit 17010212, Flathead Indian 

Reservation, on right bank, 0.3 mi downstream from West Fork, 7.3 mi southwest of Dixon, and at river mile 5.2.

DRAINAGE AREA.--23.4 mi2.

PERIOD OF RECORD.--October 1982 to current year (2002).

GAGE.--Water-stage recorder and crest-stage gage. Altitude of gage is 3,420 ft (NGVD 29).

REMARKS.--No known regulation or diversion upstream from station. 

Magnitude and probability of annual low flow

based on 19 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 3.4 2.9 2.8 2.7 -- --

3 3.6 3.1 2.9 2.8 -- --

7 3.8 3.3 3.1 3.0 -- --

14 4.0 3.5 3.3 3.2 -- --

30 4.2 3.6 3.4 3.3 -- --

60 4.5 3.8 3.5 3.3 -- --

90 4.7 4.0 3.7 3.5 -- --

120 5.0 4.2 3.9 3.7 -- --

183 5.4 4.4 4.1 3.9 -- --

Magnitude and probability of seasonal low flow from

March-June based on 20 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 4.4 3.3 3.0 2.8 -- --

3 4.6 3.5 3.1 3.0 -- --

7 4.9 3.7 3.3 3.1 -- --

14 5.1 3.9 3.5 3.3 -- --

30 6.2 4.4 3.9 3.6 -- --

Magnitude and probability of seasonal low flow from

November-February based on 19 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 3.7 3.0 2.8 2.7 -- --

3 3.9 3.2 2.9 2.8 -- --

7 4.1 3.4 3.1 3.0 -- --

14 4.2 3.5 3.3 3.2 -- --

30 4.3 3.6 3.4 3.3 -- --

Duration of daily mean flows based on 20 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

3.0 3.1 3.6 4.2 4.8 5.4 6.2 7.5

40% 30% 20% 15% 10% 5% 2% 1%

9.5 13 23 34 48 72 117 157

Magnitude and probability of annual high flow

based on 20 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 139 195 234 287 -- --

3 128 176 209 252 -- --

7 112 155 185 226 -- --

15 92 129 157 196 -- --

30 76 107 133 173 -- --

60 58 79 97 123 -- --

90 46 63 76 96 -- --

Magnitude and probability of seasonal low flow from

July-October based on 19 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 5.1 4.2 3.8 3.5 -- --

3 5.1 4.2 3.8 3.5 -- --

7 5.2 4.3 3.8 3.5 -- --

14 5.3 4.3 3.9 3.6 -- --

30 5.5 4.5 4.1 3.8 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 12 4.0 6.4 2.2 20

November 15 4.3 6.9 2.8 20

December 28 3.8 6.7 5.3 20

January 12 3.5 5.4 2.2 20

February 20 3.5 5.7 3.7 20

March 24 4.0 8.0 5.3 20

April 56 9.1 23 12 20

May 165 45 67 26 20

June 134 19 57 32 20

July 26 10 17 5.8 20

August 11 5.5 8.1 1.5 20

September 11 4.2 6.4 1.6 20

Annual 35 12 18 6.0 20
310 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

12388700 Flathead River at Perma, Mont.

Site Number 282

LOCATION.--Lat 47°22'03", long 114°35'03" (NAD 27), in SE1⁄4NE1⁄4NE1⁄4 sec.36, T.19 N., R.24 W., Sanders County, Hydrologic Unit 17010212, Flathead Indian 

Reservation, on right bank 0.3 mi north of Perma, 0.4 mi downstream from Camas Creek, and at river mile 10.9.

DRAINAGE AREA.--8,795 mi2.

PERIOD OF RECORD.--October 1983 to current year (2002).

GAGE.--Water-stage recorder. Altitude of gage is 2,469.31 ft (NGVD 29).

REMARKS.--Flow affected by regulation from Hungry Horse Reservoir (station number 12362000) and by Flathead Lake (station number 12371500). Diversions 

for irrigation of about 160,500 acres upstream from station. U.S. Geological Survey satellite telemeter at station. 

Magnitude and probability of annual low flow

based on 18 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 4,480 3,740 3,380 3,100 -- --

3 4,590 3,800 3,430 3,150 -- --

7 4,690 3,890 3,550 3,300 -- --

14 4,990 4,230 3,900 3,660 -- --

30 5,870 4,820 4,290 3,880 -- --

60 6,750 5,420 4,730 4,190 -- --

90 7,860 6,100 5,230 4,540 -- --

120 8,700 6,800 5,780 4,960 -- --

183 9,420 7,620 6,620 5,790 -- --

Magnitude and probability of seasonal low flow from

March-June based on 19 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 5,660 4,110 3,580 3,240 -- --

3 5,970 4,290 3,700 3,310 -- --

7 6,260 4,480 3,880 3,490 -- --

14 6,600 4,940 4,400 4,060 -- --

30 7,530 5,790 5,210 4,840 -- --

Magnitude and probability of seasonal low flow from

November-February based on 18 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 6,050 4,820 4,250 3,820 -- --

3 6,590 5,120 4,440 3,920 -- --

7 7,160 5,420 4,610 4,000 -- --

14 7,540 5,670 4,790 4,130 -- --

30 8,350 6,260 5,250 4,480 -- --

Duration of daily mean flows based on 19 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

3,340 3,590 4,350 5,450 6,960 8,190 9,340 10,400

40% 30% 20% 15% 10% 5% 2% 1%

11,500 13,100 15,100 16,100 17,400 24,900 36,300 44,100

Magnitude and probability of annual high flow

based on 19 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 32,500 45,000 51,500 58,100 -- --

3 31,300 43,500 50,200 57,300 -- --

7 28,400 40,100 47,000 55,000 -- --

15 25,800 37,000 44,200 53,100 -- --

30 22,700 32,900 40,200 49,800 -- --

60 19,100 26,700 32,300 40,000 -- --

90 16,900 23,100 27,400 33,300 -- --

Magnitude and probability of seasonal low flow from

July-October based on 18 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 4,620 4,070 3,850 3,680 -- --

3 4,860 4,150 3,870 3,680 -- --

7 5,170 4,300 3,940 3,690 -- --

14 5,550 4,540 4,110 3,800 -- --

30 6,430 5,090 4,450 3,960 -- --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 12,100 4,300 8,900 2,240 19

November 13,200 4,050 10,700 1,970 19

December 17,300 6,160 11,100 2,660 19

January 15,200 6,100 10,700 2,610 19

February 18,300 4,230 9,930 3,290 19

March 23,400 4,120 9,450 4,160 19

April 23,400 4,400 10,400 4,470 19

May 36,900 5,880 15,500 7,640 19

June 45,500 9,090 23,100 10,700 19

July 22,800 6,280 13,300 4,980 19

August 12,700 4,160 8,160 2,600 19

September 13,100 4,010 8,160 2,570 19

Annual 18,000 7,040 11,600 2,860 19
Statistical Summaries of Streamflow 311

12389000 Clark Fork near Plains, Mont.

Site Number 283

LOCATION.--Lat 47°25'47", long 114°51'18" (NAD 27), in E1⁄2SW1⁄4 sec.1, T.19 N., R.26 W., Sanders County, Hydrologic Unit 17010213, on right bank 2.4 mi 

southeast of Plains, 6.0 mi downstream from Flathead River, and at river mile 239.0.

DRAINAGE AREA.--19,958 mi2.

PERIOD OF RECORD.--October 1910 to current year (2002). Monthly discharge only for some periods, published in WSP 1316.

REVISED RECORDS.--WSP 1246: Drainage area.

GAGE.--Water-stage recorder. Altitude of gage is 2,449.11 ft (NGVD 29, levels by U.S. Army Corps of Engineers). Prior to Nov. 28, 1911, nonrecording gage 

at site 50 ft upstream at same datum.

REMARKS.--Flow partly regulated by Hungry Horse Reservoir (station number 12362000) and by Flathead Lake (station number 12371500). Diversions for 

irrigation of about 335,000 acres upstream from station. U.S. Geological Survey satellite telemeter at station. 

Magnitude and probability of annual low flow

based on 91 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 5,930 4,800 4,260 3,840 3,410 3,140

3 6,190 4,990 4,430 4,000 3,560 3,280

7 6,460 5,190 4,600 4,150 3,690 3,410

14 6,750 5,370 4,750 4,270 3,790 3,490

30 7,270 5,710 5,000 4,460 3,910 3,570

60 8,140 6,290 5,440 4,800 4,140 3,740

90 8,910 6,730 5,750 5,020 4,270 3,830

120 9,510 7,120 6,040 5,240 4,420 3,930

183 10,500 7,890 6,660 5,720 4,770 4,200

Magnitude and probability of seasonal low flow from

March-June based on 92 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 8,620 6,340 5,460 4,860 4,290 3,970

3 8,940 6,530 5,600 4,960 4,350 3,990

7 9,240 6,740 5,770 5,100 4,470 4,100

14 9,650 6,990 5,960 5,240 4,550 4,150

30 10,500 7,560 6,420 5,620 4,870 4,430

Magnitude and probability of seasonal low flow from

November-February based on 91 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 7,240 5,490 4,700 4,110 3,520 3,150

3 7,680 5,750 4,880 4,230 3,570 3,290

7 8,130 6,000 5,050 4,340 3,700 3,420

14 8,560 6,210 5,180 4,420 3,800 3,500

30 9,160 6,540 5,400 4,580 3,920 3,590

Duration of daily mean flows based on 92 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

4,400 4,690 5,560 6,570 8,100 9,730 11,500 13,400

40% 30% 20% 15% 10% 5% 2% 1%

15,500 18,900 25,700 33,600 45,200 63,400 84,800 95,600

Magnitude and probability of annual high flow

based on 92 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 76,900 101,000 113,000 123,000 130,000 135,000

3 75,700 99,700 111,000 122,000 128,000 133,000

7 72,300 96,100 108,000 119,000 126,000 131,000

15 67,600 90,800 103,000 114,000 121,000 127,000

30 61,500 82,400 93,100 104,000 110,000 115,000

60 51,800 67,900 75,900 83,700 88,200 91,900

90 43,300 56,300 62,800 69,300 73,100 76,300

Magnitude and probability of seasonal low flow from

July-October based on 91 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 6,540 5,290 4,740 4,320 3,900 3,640

3 6,800 5,510 4,940 4,520 4,080 3,820

7 7,100 5,760 5,160 4,720 4,270 3,990

14 7,460 6,020 5,380 4,910 4,430 4,140

30 8,040 6,440 5,710 5,170 4,620 4,280

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 23,600 4,760 10,600 3,340 92

November 21,200 4,590 11,500 3,910 92

December 27,600 4,080 12,000 4,590 92

January 22,300 3,340 12,000 4,720 92

February 30,100 3,940 11,900 5,060 92

March 31,400 4,640 11,900 5,050 92

April 47,800 6,110 19,400 8,470 92

May 89,800 10,000 44,500 16,000 92

June 102,000 10,000 54,900 21,500 92

July 76,900 7,840 25,900 11,700 92

August 24,800 5,660 11,000 3,510 92

September 16,900 4,770 9,660 2,740 92

Annual 29,400 8,840 19,600 4,830 92
312 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

12389500 Thompson River near Thompson Falls, Mont.

Site Number 284

LOCATION.--Lat 47°35'31", long 115°13'43" (NAD 27), in NW1⁄4NE1⁄4SE1⁄4 sec.7, T.21 N., R.28 W., Sanders County, Hydrologic Unit 17010213, Lolo National 

Forest, on right bank 1.2 mi upstream from mouth and 5.5 mi east of Thompson Falls.

DRAINAGE AREA.--642 mi2.

PERIOD OF RECORD.--March to September 1911, October 1911 to September 1916 (occasional gage heights, discharges, and discharge measurements), April 

1956 to current year (2002).

REVISED RECORDS.--WSP 1246: 1911.

GAGE.--Water-stage recorder. Altitude of gage is 2,429.97 ft (NGVD 29, Bureau of Public Roads bench mark). October 1911 to September 1916, nonrecording 

gage at site 0.2 mi upstream at different datum.

REMARKS.--Minor diversions upstream from station for irrigation, acreage unknown. Diversion from headwaters of Alder Creek in SW1⁄4 sec.16, T.23 N., 

R.25 W., to supplement water supply for storage in Upper Dry Fork Reservoir in Little Bitterroot River basin. U.S. Geological Survey satellite telemeter at 

station. 

Magnitude and probability of annual low flow

based on 45 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 100 82 74 67 61 --

3 111 92 83 76 69 --

7 125 103 92 84 76 --

14 136 113 102 94 85 --

30 145 122 111 102 93 --

60 156 130 117 108 97 --

90 161 134 121 110 99 --

120 169 139 124 113 102 --

183 185 149 133 121 109 --

Magnitude and probability of seasonal low flow from

March-June based on 47 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 196 137 116 102 89 --

3 200 142 121 108 95 --

7 210 151 131 117 106 --

14 225 164 143 130 118 --

30 285 199 168 148 129 --

Magnitude and probability of seasonal low flow from

November-February based on 46 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 102 82 74 68 61 --

3 114 93 84 77 69 --

7 130 104 93 85 76 --

14 139 113 102 95 88 --

30 150 123 114 108 103 --

Duration of daily mean flows based on 46 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

96 100 113 133 160 186 218 252

40% 30% 20% 15% 10% 5% 2% 1%

308 409 658 869 1,120 1,580 2,160 2,720

Magnitude and probability of annual high flow

based on 46 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 2,160 3,270 3,980 4,840 5,450 --

3 2,050 3,030 3,630 4,340 4,820 --

7 1,850 2,670 3,150 3,680 4,040 --

15 1,610 2,320 2,750 3,240 3,570 --

30 1,420 2,050 2,430 2,890 3,200 --

60 1,190 1,700 2,000 2,340 2,560 --

90 1,020 1,440 1,680 1,950 2,120 --

Magnitude and probability of seasonal low flow from

July-October based on 46 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 163 135 121 110 98 --

3 165 137 122 110 98 --

7 167 138 123 111 99 --

14 170 140 125 113 100 --

30 175 144 128 115 102 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 343 112 183 45 46

November 501 115 200 75 46

December 880 101 209 125 46

January 719 112 208 111 46

February 1,230 103 254 183 46

March 1,340 120 354 228 47

April 1,830 238 794 396 48

May 3,150 374 1,340 602 48

June 2,370 244 1,040 519 48

July 724 140 414 148 48

August 382 113 242 64 48

September 288 105 196 45 48

Annual 804 176 447 158 46
Statistical Summaries of Streamflow 313

12390700 Prospect Creek at Thompson Falls, Mont.

Site Number 285

LOCATION.--Lat 47°35'10", long 115°21'15" (NAD 27), in lot 12, SE1⁄4SE1⁄4SE1⁄4 sec.7, T.21 N., R.29 W., Sanders County, Hydrologic Unit 17010213, on right 

bank 500 ft downstream from Dry Creek, 0.5 mi upstream from mouth, and 0.7 mi south of Thompson Falls.

DRAINAGE AREA.--182 mi2.

PERIOD OF RECORD.--April 1956 to current year (2002).

GAGE.--Water-stage recorder. Altitude of gage is 2,382.40 ft (NGVD 29).

REMARKS.--No known regulation or diversions upstream from station. U.S. Geological Survey satellite telemeter at station. 

Magnitude and probability of annual low flow

based on 45 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 40 33 29 27 24 --

3 41 33 30 27 25 --

7 42 34 31 28 25 --

14 43 35 32 29 26 --

30 45 36 33 30 27 --

60 47 38 34 31 28 --

90 50 40 35 32 29 --

120 53 42 37 34 30 --

183 67 49 42 37 33 --

Magnitude and probability of seasonal low flow from

March-June based on 46 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 107 62 46 35 25 --

3 110 64 47 35 26 --

7 114 66 48 37 27 --

14 125 72 53 40 29 --

30 173 99 71 53 37 --

Magnitude and probability of seasonal low flow from

November-February based on 46 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 42 33 29 27 25 --

3 42 33 30 28 26 --

7 44 34 31 29 26 --

14 45 35 32 30 28 --

30 50 37 33 30 28 --

Duration of daily mean flows based on 46 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

28 33 37 43 54 64 81 106

40% 30% 20% 15% 10% 5% 2% 1%

148 228 378 510 685 976 1,340 1,570

Magnitude and probability of annual high flow

based on 46 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 1,460 2,160 2,650 3,280 3,760 --

3 1,370 1,910 2,230 2,610 2,860 --

7 1,210 1,610 1,830 2,060 2,210 --

15 1,030 1,370 1,560 1,770 1,900 --

30 880 1,190 1,360 1,560 1,680 --

60 730 971 1,100 1,230 1,320 --

90 619 819 921 1,020 1,080 --

Magnitude and probability of seasonal low flow from

July-October based on 46 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 48 39 34 31 27 --

3 48 39 35 31 27 --

7 49 40 35 31 28 --

14 50 40 36 32 28 --

30 52 42 37 33 29 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 168 29 55 21 46

November 469 29 81 82 46

December 701 30 115 125 46

January 735 29 118 117 46

February 875 26 161 153 46

March 828 32 221 153 46

April 1,330 84 498 240 47

May 1,600 297 812 302 47

June 1,470 142 546 288 47

July 317 74 163 62 47

August 109 48 84 17 47

September 80 36 62 12 47

Annual 441 86 240 83 46
314 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

12391400 Clark Fork below Noxon Rapids Dam, near Noxon, Mont.

Site Number 286

LOCATION.--Lat 47°57'40", long 115°43'58" (NAD 27), in SW1⁄4 sec.33, T.26 N., R.32 W., Sanders County, Hydrologic Unit 17010213, at Noxon Rapids Dam, 

1 mi upstream from Rock Creek, 3 mi southeast of Noxon, and at river mile 169.7.

DRAINAGE AREA.--21,833 mi2.

PERIOD OF RECORD.--May 1960 to current year (2002).

GAGE.--Plant generator rating or discharge through powerplant. Water-stage recorder on reservoir determines head on taintor gates. Altitude of gage is 2,320 ft 

(NGVD 29, levels by the Washington Water Power Co.).

REMARKS.--Flow regulated by Hungry Horse Reservoir (station number 12362000) and Flathead Lake (station number 12371500). Diversions for irrigation of 

about 350,000 acres upstream from station. Some subsurface flow indicated by comparison with records for adjacent gaging stations. Figures of discharge 

given herein are combined flows through turbines and spillway. 

Magnitude and probability of annual low flow

based on 41 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1,350 395 183 90 38 --

3 6,380 4,610 3,780 3,150 2,530 --

7 6,380 4,610 3,780 3,150 2,530 --

14 7,300 5,490 4,620 3,950 3,270 --

30 8,240 6,350 5,420 4,700 3,950 --

60 9,500 7,560 6,570 5,800 4,980 --

90 10,600 8,580 7,540 6,700 5,800 --

120 11,200 9,230 8,150 7,280 6,340 --

183 12,200 10,300 9,320 8,540 7,680 --

Magnitude and probability of seasonal low flow from

March-June based on 42 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 6,290 3,340 2,310 1,680 1,150 --

3 9,770 6,520 5,230 4,340 3,500 --

7 12,200 8,530 6,970 5,850 4,750 --

14 13,300 9,460 7,770 6,530 5,320 --

30 14,700 10,700 8,970 7,760 6,570 --

Magnitude and probability of seasonal low flow from

November-February based on 42 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 3,670 1,460 734 369 149 --

3 6,540 4,760 3,850 3,260 2,600 --

7 9,020 6,860 5,780 4,940 4,080 --

14 10,000 7,930 6,900 6,090 5,240 --

30 10,900 8,790 7,820 7,080 6,320 --

Duration of daily mean flows based on 42 years of record

Discharge, in ft3/s, which was equaled or exceeded for indicated percent of time

99% 98% 95% 90% 80% 70% 60% 50%

3,180 4,140 5,610 7,270 9,750 11,800 13,600 15,300

40% 30% 20% 15% 10% 5% 2% 1%

17,200 21,400 26,400 32,300 41,800 58,900 80,200 93,300

Magnitude and probability of annual high flow

based on 42 years of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and exceedance probability, in percent

2 5 10 25 50 100

50% 20% 10% 4% 2% 1%

1 72,000 98,300 113,000 128,000 137,000 --

3 70,200 96,900 111,000 127,000 136,000 --

7 65,700 92,100 107,000 123,000 133,000 --

15 60,400 85,300 99,600 115,000 125,000 --

30 54,400 76,700 89,400 104,000 113,000 --

60 46,100 63,100 72,700 83,100 89,800 --

90 39,500 53,100 60,600 68,600 73,800 --

Magnitude and probability of seasonal low flow from

July-October based on 42 seasons of record

Period of 

consecutive 

days

Discharge, in ft3/s, for indicated recurrence interval, in years,

and non-exceedance probability, in percent

2 5 10 20 50 100

50% 20% 10% 5% 2% 1%

1 1,930 521 225 170 78 --

3 6,860 4,980 4,060 3,370 2,670 --

7 6,860 4,980 4,060 3,370 2,670 --

14 7,650 5,760 4,850 4,150 3,440 --

30 8,550 6,550 5,580 4,820 4,040 --

Monthly and annual mean discharges

Month Maximum

(ft3/s)

Minimum

(ft3/s)

Mean

(ft3/s)

Standard 

deviation

(ft3/s)

Years of 

record

October 16,200 6,170 11,800 2,430 42

November 19,900 6,830 13,200 2,820 42

December 31,500 8,610 14,200 3,920 42

January 22,200 7,620 14,400 3,150 42

February 34,600 6,180 15,100 5,260 42

March 33,700 6,920 16,400 5,780 42

April 46,400 4,870 22,600 9,050 42

May 88,200 10,000 40,600 16,100 42

June 92,600 10,000 50,800 21,800 43

July 40,700 8,330 23,300 8,660 43

August 17,700 5,350 10,600 2,900 43

September 16,400 4,840 10,300 2,840 43

Annual 31,900 10,000 20,300 5,090 42
Selected References 315

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316 Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002

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Text layout by Ella M. Decker, USGS, Huron, South Dakota.

Graphics layout by Connie J. Ross, USGS, Huron, South Dakota.

Information regarding the water resources in Montana is available at URL

 http://mt.water.usgs.gov/

This publication is available online at URL

 http://pubs.water.usgs.gov/sir20045266

Prepared by the USGS Montana District:

U.S. Geological Survey

3162 Bozeman Avenue

Helena, MT 59601
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McCarthy—Statistical Summaries of Streamflow in Montana and Adjacent Areas, Water Years 1900 through 2002—Scientific Investigations Report 2004-5266