science 

USGS

for a changing world '13/of

In cooperation with the

MONTANA DEPARTMENT OF NATURAL RESOURCES AND CONSERVATION

and LEWIS AND CLARK COUNTY

Streamflow and Water-Quality Characteristics in the 

Upper Tenmile Creek Watershed, Lewis and Clark 

County, West-Central Montana

Water-Resources Investigations Report 00-4129

U.S. Department of the Interior 

U.S. Geological Survey
COVER: Staff gage on Ruby Creek at mouth near Rimini, Montana.
U.S. Department of the Interior 

U.S. Geological Survey

Streamflow and Water-Quality Characteristics in the 

Upper Tenmile Creek Watershed, Lewis and Clark 

County, West-Central Montana

By Charles Parrett and Patricia S. Hettinger

Water-Resources Investigations Report 00-4129

In cooperation with the

MONTANA DEPARTMENT OF NATURAL RESOURCES AND CONSERVATION and

LEWIS AND CLARK COUNTY
U.S. Department of the Interior

BRUCE BABBITT, Secretary

U.S. Geological Survey

Charles G. Groat, Director

Any use of trade, product, or firm name in this publication is for 

descriptive purposes only and does not imply endorsement by the 

U.S. Government

Helena, Montana 

September 2000

For additional information write to:

District Chief 

U.S. Geological Survey 

3162 Bozeman Avenue 

Helena, MT 59601-6456

Copies of this report may be purchased from:

U.S. Geological Survey 

Branch of Information Services 

Box 25286 

Denver, CO 80225-0286
CONTENTS

Page

Abstract ..............................................................................................................................................................^ 1

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

Purpose and scope......................................................................................................................................... 3

Acknowledgments......................................................................................................................................... 3

Study area description and historical land and water use.......................................................................................... 3

Streamflow.............................................................................................................................................................. 4

Historical Streamflow and hydrologic data.................................................................................................... 4

Additional hydrologic collection in 1997 ...................................................................................................... 6

Techniques for estimation of long-term monthly and daily discharge............................................................ 6

Estimation of long-term monthly natural flows for Tenmile Creek near Rimini.................................. 8

Estimation of daily natural discharge for May-October 1997 for Tenmile Creek near Rimini............. 9

Estimation of long-term monthly natural discharge for selected sites ................................................. 11

Reliability of long-term monthly discharge estimates ......................................................................... 16

Determination of gaining and losing stream reaches on Tenmile Creek......................................................... 17

Water-quality ......................................................................................................................................................^ 21

Strategy for sample collection and analysis................................................................................................... 21

Methods of sample collection and analysis.................................................................................................... 22

Water sampling................................................................................................................................... 22

Bottom-sediment sampling................................................................................................................. 22

Quality assurance.......................................................................................................................................... 23

Sampling sites and potential sources of water-quality degradation................................................................ 24

Headwaters sampling sites.................................................................................................................. 24

Sampling sites near Rimini................................................................................................................. 24

Sampling sites in the Beaver Creek drainage...................................................................................... 24

Sampling sites between Rimini and the Tenmile Water Treatment Plant............................................. 25

Bottom-sediment sites in and near Chessman Reservoir..................................................................... 25

Results of water-quality analyses .................................................................................................................. 25

Field-measured parameters, major ions, and nutrients ........................................................................ 25

Trace elements.................................................................................................................................... 26

Aluminum................................................................................................................................ 27

Arsenic.................................................................................................................................... 27

Cadmium................................................................................................................................. 27

Copper..................................................................................................................................... 27

Iron.......................................................................................................................................... 30

Lead......................................................................................................................................... 31

Manganese............................................................................................................................... 32

Chromium, mercury, nickel, selenium, and silver .................................................................... 32

Zinc......................................................................................................................................... 32

Suspended sediment........................................................................................................................... 32

Bottom sediment................................................................................................................................. 33

Exceedances of water-quality standards ........................................................................................................ 33

Human health..................................................................................................................................... 34

Aquatic life......................................................................................................................................... 34

Constituent transport in streams .................................................................................................................... 35

Summary .............................................................................................................................................................^ 39

Selected references .................................................................................................................................................. 42

CONTENTS iii
ILLUSTRATIONS

Page

Figure 1. Map showing upper Tenmile Creek watershed and location of data-collection sites and inactive mines..... 2

2. Schematic diagram showing water sources, reservoirs, diversions, and conveyance system for the

Tenmile Water Treatment Plant near Rimini, Montana................................................................................ 5

Figures 3-7. Graphs showing:

3. Stage-discharge relationships for two sites in the upper Tenmile Creek watershed near

Rimini, Montana............................................................................................................................... 7

4. Recorded and estimated average monthly natural discharge for Tenmile Creek near

Rimini, Montana, water years 1961-90............................................................................................ 10

5. Recorded daily discharge and estimated natural flow accretion and natural daily discharge

for Tenmile Creek near Rimini, Montana, May-October 1997........................................................ 11

6. Monthly and seasonal average diversions from Beaver Creek, Tenmile Creek, and

Minnehaha Creek near Rimini, Montana, May-October 1997......................................................... 12

7. Regression lines relating measured and observed discharge data for Moore's Spring Creek, 

Bear Gulch, and Tenmile Creek above Ruby Creek to concurrent estimated daily 

natural discharge for Tenmile Creek near Rimini, Montana............................................................ 13

Figures 8-12. Graphs showing estimated long-term monthly natural discharge for streams, upper Tenmile 

Creek watershed near Rimini, Montana:

8. Small tributary streams........................................................................................................................ 14

9. Mid-size tributary streams................................................................................................................... 14

10. Beaver Creek tributaries...................................................................................................................... 15

11. Large tributary streams........................................................................................................................ 15

12. Mainstem Tenmile Creek..................................................................................................................... 16

Figures 13-17. Graphs showing:

13. Estimated long-term annual natural discharge for streams in the upper Tenmile Creek

watershed near Rimini, Montana..................................................................................................... 17

14. Estimated long-term annual unit natural discharge for streams in the upper Tenmile Creek

watershed near Rimini, Montana ..................................................................................................... 18

15. Regression relationship between selected daily mean discharge for Prickly Pear Creek and

estimated daily mean natural discharge for Tenmile Creek near Rimini, Montana......................... 19

16. Comparison between estimated and recorded long-term mean monthly discharge for Prickly

Pear Creek, Montana........................................................................................................................ 19

17. Measured discharge and estimated error, September 6, 1998 and July 14, 1999,

Tenmile Creek, upper Tenmile Creek watershed near Rimini, Montana......................................... 20

Figures 18-21. Graphs showing total-recoverable concentrations in 1997 for selected sites in the upper Tenmile 

Creek watershed near Rimini, Montana:

18. Arsenic................................................................................................................................................. 28

19. Cadmium............................................................................................................................................. 29

20. Copper................................................................................................................................................. 30

21. Lead ................................................................. 31

Figures 22-25. Graphs showing instantaneous total-recoverable loads in 1997 for selected sites in the upper 

Tenmile Creek watershed near Rimini, Montana:

22. Arsenic................................................................^ 36

23. Cadmium............................................................................................................................................. 37

24. Copper ........................................... 38

25. Lead..................................................................................................................................................... 39

iv Streamflow and Water-Quality Characteristics in the Upper Tenmile Creek Watershed, Lewis and Clark County, West-Central Montana
TABLES

Page

Table 1. Streamflow data-collection sites and purposes, upper Tenmile Creek watershed, Montana......................... 44

2. Discharge measurement sites, drainage area sizes, measurement dates, measured stage, and

discharge, upper Tenmile Creek watershed, Montana................................................................................ 45

3. Net monthly discharges into Scott and Chessman Reservoirs calculated from daily water-use

data at Tenmile Water Treatment Plant, Montana....................................................................................... 49

4. Monthly mean discharge diverted to Tenmile Water Treatment Plant, Montana .......................................... 50

5. Natural flow accretions for Tenmile Creek near Rimini, Montana................................................................ 51

6. Estimated average monthly and annual natural discharges for Tenmile Creek near Rimini,

Montana, for water years 1961-90 based on monthly recorded discharge plus natural flow accretion ..... 52

7. Regression results for flow estimation sites, upper Tenmile Creek watershed, Montana ............................. 53

8. Estimated long-term mean monthly and mean annual natural discharge for selected sites in the

upper Tenmile Creek watershed, Montana................................................................................................. 54

9. Streamflow sampling sites and months of water-quality sample collection during 1997, upper

Tenmile Creek watershed, Montana........................................................................................................... 55

10. Laboratory methods, minimum reporting levels, and water-quality standards for constituents

analyzed in water samples from upper Tenmile Creek watershed, Montana ............................................. 56

11. Bottom-sediment sampling sites and depths, Chessman Reservoir, upper Tenmile Creek watershed,

Montana...................................................................................................................................................... 57

12. Field-measured parameters and concentrations of major ions and nutrients in streams in the

upper Tenmile Creek watershed, Montana................................................................................................. 58

13. Concentrations of trace elements and suspended sediment in streams in the upper Tenmile

Creek watershed, Montana......................................................................................................................... 62

14. Trace-element concentrations in bottom sediment from Chessman Reservoir and an adjacent

wetland in the upper Tenmile Creek watershed, compared to concentrations in bottom sediment

from Lake Helena, Montana....................................................................................................................... 68

15. Equations for calculating hardness-dependent aquatic-life criteria for trace elements................................. 69

16. Calculated instantaneous loads of selected trace elements and suspended sediment in streams

in the upper Tenmile Creek watershed, Montana....................................................................................... 70

CONTENTS
CONVERSION FACTORS AND ABBREVIATED WATER QUALITY UNITS

Multiply

cubic foot per second (ft3/s)

cubic foot per second per day (ft3/s-day)

foot (ft)

inch (in.)

mile (mi)

pound (Ib)

By

0.028317

2.447

0.3048

25.4

1.609

0.4536

To obtain

cubic meter per second

cubic meter

meter (m)

millimeter (mm)

kilometer

kilogram

Temperature can be converted from degrees Celsius (°C) to degrees Fahrenheit (°F) by the equation:

°F = 9/5 (°C) + 32

Abbreviated water-quality units used in this report:

fig/L micrograms per liter

p,S/cm microsiemens per centimeter at 25 degrees Celsius

mg/L milligrams per liter

Water-year definition:

A water year is the 12-month period from October 1 through September 30. It is designated by the calendar year in which it ends.

Acronyms used in this report:

DNRC Montana Department of Natural Resources and Conservation

EPA U.S. Environmental Protection Agency

NWQL National Water Quality Laboratory

USGS U.S. Geological Survey

vi Streamflow and Water-Quality Characteristics in the Upper Tenmile Creek Watershed, Lewis and Clark County, West-Central Montana
Streamflow and Water-Quality Characteristics in the 

Upper Tenmile Creek Watershed, Lewis and Clark County, 

West-Central Montana

/?/Charles Parrett1 and Patricia S. Hettinger2

Abstract

A cooperative hydrologic investigation of the 

Upper Tenmile Creek watershed was initiated in May 

1997 to obtain information for long-range watershed 

planning. Thirty-two stream-stage gages were established throughout the upper Tenmile Creek watershed. 

One new continuous-record streamflow-gaging station 

was established, and one discontinued continuousrecord streamflow-gaging station (Tenmile Creek near 

Rimini) was re-established.

Long-term monthly discharge for the 1961-90 

base period was estimated at 19 of the stream-stage 

gages by regressing measured and observed discharge 

at each site in 1997 with concurrent, daily natural discharge at Tenmile Creek near Rimini. The regression 

relationship at each site then was used to estimate longterm monthly discharge from long-term monthly natural discharge at Tenmile Creek near Rimini.

Stream water was sampled and analyzed for 

water-quality constituents at 19 sites. The water-quality 

constituents of most concern were trace elements-such 

as arsenic, cadmium, copper, lead, and zinc-associated 

with past hard-rock mining and the naturally high 

trace-element content of the local rock formations. 

Water-quality analyses indicated that trace-element 

concentrations were greater than human-health standards at several sites. For example, Poison Creek, a 

Beaver Creek tributary, and Tenmile Creek below 

Spring Creek had one or more samples that exceeded 

the human-health standards for arsenic, cadmium, or 

lead. Analyses also indicated that many samples at 

many sites had concentrations of trace elements, particularly copper, greater than aquatic-life standards for 

acute toxicity. A likely source of copper at some sites 

was mine-waste rock or mine-adit discharge. At other

sites, a likely source of copper was copper sulfate used 

as an algicide in Chessman Reservoir.

INTRODUCTION

Tenmile Creek is a perennial stream that is a tributary to the Missouri River and drains about 200 square 

miles of mountainous and valley terrain near the City of 

Helena in west-central Montana. Upper Tenmile 

Creek, defined as the reach above the Tenmile Water 

Treatment Plant (fig. 1), drains about 50 square miles 

of mostly forested, steep mountainous terrain. The 

headwaters are on the Continental Divide, where the 

maximum elevation is more than 8,000 ft. The stream 

flows in a generally northeasterly direction to the water 

treatment plant, where the elevation is about 4,400 ft.

Upper Tenmile Creek is the major source of 

municipal water supply for the growing community of 

Helena (population about 30,000). Because the drainage basin is small and located in a relatively dry mountain setting, annual and seasonal runoff is variable. 

Water volumes withdrawn for municipal demands 

often are sufficient to de-water portions of the stream in 

late summer, thereby rendering the aquatic habitat as 

unsuitable for a year-round fishery. The basin also has 

been impacted by substantial mining activity over the 

past 100 years, resulting in drainage from inactive 

mines entering the stream at various locations. Other 

land-use activities that may affect water quality in Tenmile Creek, such as logging, recreation, streamside residential development, and road traffic, are increasing.

The Upper Tenmile Watershed Steering Group, 

comprised of landowners and various private and public entities, was formed in 1996 to develop a watershedmanagement plan for maintaining and enhancing

^.S. Geological Survey 

2Lewis and Clark County

INTRODUCTION
R«W.

T.10N

17

R1

%^nmi,e MONTANA 

^vCreek /~i /""£" R»w 

r watershed.

EXPLANATION

(06062750) U.S. GEOLOGICAL SURVEY STREAMFLOWGAGING STATION NUMBER

RedWate

PURPOSE OF SITE

A STREAMFLOW-ESTIMATION OR GAGING SITE AND 

NUMBER

V WATER-QUALITY ANALYSIS SITE AND NUMBER

BOTTOM-SEDIMENT ANALYSIS SITE AND NUMBER 

INACTIVE MINE AND NAME

R2A, R2B

2 MILES

2 KILOMETERS

Peerless Jenny/King

 !/ Bas,n Creek

Base map modified from U.S. Geological Survey digital data, 1 :24,000, 

1961-89 (streams); U.S. Census Bureau tiger-line digital data, 1 :100,000, 

1992 (roads). Albers Equal Area Conic Projection Standard, parallels 46°00' 

and 48°00', central meridian 109°30'.

Figure 1. Upper Tenmile Creek watershed and location of data-collection sites and inactive mines.

2 Streamflow and Water-Quality Characteristics in the Upper Tenmile Creek Watershed, Lewis and Clark County, West-Centrai Montana
existing water quantity and quality within the upper 

watershed. Private and public entities represented on 

the Watershed Steering Group include Pegasus Gold 

Corporation; Lewis and Clark County Conservation 

District; City of Helena; Lewis and Clark County; 

Montana Department of Environmental Quality; 

Montana Department of Fish, Wildlife and Parks; 

Montana Department of Natural Resources and 

Conservation; U.S. Environmental Protection Agency; 

U.S. Forest Service; U.S. Geological Survey; and U.S. 

Natural Resources Conservation Service.

The Steering Group was unable to evaluate the 

hydrologic impacts of various watershed management 

alternatives because hydrologic data were available at 

only one location in the upper watershed. In order to 

meet its objective of maintaining and enhancing water 

quantity and quality, the Upper Tenmile Watershed 

Steering Group needed information about current 

streamflow and water-quality conditions at multiple 

locations in the upper Tenmile Creek watershed. Estimates of long-term natural (unaffected by human activity) monthly flows were also needed because flows in 

the watershed are affected by storage and withdrawals 

for municipal use.

Purpose and Scope

A cooperative study among the Montana Department of Natural Resources and Conservation (DNRC), 

Lewis and Clark County, and the U.S. Geological Survey (USGS) was initiated in 1997 to obtain hydrologic 

information for long-range planning in the upper Tenmile Creek watershed. The purpose of this report is to 

describe the methods and results of the cooperative 

study. The study area includes only the upper Tenmile 

Creek watershed, although a similar cooperative 

hydrologic study of the lower portion of the Tenmile 

Creek watershed also has been initiated.

Specific objectives established for the cooperative study were:

Objective 1: Estimate long-term, natural

monthly flows at selected sites in 

the upper Tenmile Creek 

watershed.

Objective 2: Determine where Tenmile Creek 

gains flow from and loses flow to 

ground water in the 8-mile channel 

reach between the city's stream

diversion at Rimini and the Tenmile 

Water Treatment Plant.

Objective 3: Characterize current water quality 

over a range of flow conditions and 

calculate instantaneous loads of 

selected constituents at selected 

sites to help identify potential 

sources of metal inputs.

Acknowledgments

A special word of thanks is owed to the residents 

and property owners of the Tenmile Creek watershed 

who participated in this project. Many volunteers collected staff-gage readings during May through October 

1997. Their time and effort greatly assisted in the 

refinement of stage-discharge relationships used to 

estimate long-term monthly streamflow. Additional 

thanks go to the members of the Upper Tenmile Watershed Steering Group for their assistance in developing 

the grant application to fund the study and in developing the work plan. Special thanks also go to Montana 

Tunnels, Inc. for their generous contribution of analytical services at their laboratory. The laboratory analyzed approximately 80 water-quality samples and 

reruns and provided timely results and assistance to the 

authors. Their efforts on behalf of the Upper Tenmile 

Watershed Steering Group are greatly appreciated. 

Finally, the authors thank Robert L. Tortorelli, USGS 

hydrologist in Oklahoma, whose careful and thorough 

review materially aided this report.

STUDY AREA DESCRIPTION AND HISTORICAL 

LAND AND WATER USE

The upper Tenmile Creek watershed is located in 

the Rocky Mountains near Helena in Lewis and Clark 

County. The study area lies within the Northern Rocky 

Mountains physiographic province, which is characterized by a succession of distinct mountain ranges and 

valleys. Glaciation has been the predominant factor in 

shaping the basin's landforms and in the development 

of soils. Glacial features cover more than half of the 

basin and include cirque basins and moraine deposits, 

colluvial deposits, terraces and floodplains. Unglaciated terrain forms mountain slopes and ridges. Bedrock 

underlying the glacial materials consists mainly of CreSTUDY AREA DESCRIPTION AND HISTORICAL LAND AND WATER USE
taceous age intrusive rocks (U.S. Department of Agriculture, 1989).

The upper Tenmile Creek watershed has a continental climate modified by Pacific Ocean air masses. 

Winters tend to be cold and moist, and summers are 

warm and dry. The nearest weather station, Frohner 

Meadows, is located 1-mi southeast of the study area at 

an elevation of 6,480 ft. Based on data for 1979-98, the 

average annual precipitation at this location is 24.6 in. 

(U.S. Department of Agriculture, unpub. data, 1998). 

Monthly average precipitation ranges from 1.3 in. in 

February to 3.5 in. in May. Air temperature data at this 

station are available only for the period 1989-98. For 

this period, mean monthly temperatures range from 

19.6 °F in January to 55.8 °F in August (Roy Kaiser, 

U.S. Department of Agriculture, Natural Resources 

Conservation Service, written commun., 1998).

The upper Tenmile Creek watershed has been the 

focus of numerous, generally small, hard-rock mining 

operations since the discovery of gold in Helena in 

1864. Gold, silver, lead, and zinc mines were scattered 

throughout the watershed and formed the economic 

basis for the small community of Rimini, located about 

8 miles upstream from the Tenmile Water Treatment 

Plant. Although all known mines are currently inactive, 

exposed waste-rock piles and mine spoils from the earlier mining ventures are located throughout the upper 

basin. These mine wastes typically contain trace metals 

known to be hazardous to human health and aquatic 

biota and constitute a potential threat to the water quality of Tenmile Creek. Inactive mine sites which have 

impacted or are considered to be a potential threat to 

streams in the watershed are shown on figure 1.

The early mining activities in the watershed 

required water; therefore, the first diversions and water 

withdrawals from Tenmile Creek were for mining purposes. In the late 1800s, Chessman Reservoir was constructed to provide water for hydraulic mining in a 

small adjacent basin east of the upper watershed. 

Chessman Reservoir is located at the headwaters of 

Beaver Creek, a tributary to Tenmile Creek, and 

receives most of its water transported by a flume from 

Banner Creek, another tributary to Tenmile Creek

(fig- 1).

The City of Helena began management of Chessman Reservoir in the early 1900s to serve the municipal 

water needs of its growing population. Today, Helena 

still receives about 70 percent of its municipal water 

supply from the upper Tenmile Creek watershed. In 

addition to Chessman Reservoir, with a current storage

capacity of 350 million gallons, the water collection 

system for the Tenmile Water Treatment Plant also 

includes Scott Reservoir. Scott Reservoir, with a capacity of 195 million gallons, was constructed in 1962 near 

the headwaters of Ruby Creek, a tributary to Tenmile 

Creek. Diversion structures are located on Banner 

Creek, Beaver Creek, Tenmile Creek, Minnehaha 

Creek, Moose Creek, and Walker Creek. Except for the 

Banner Creek diversion, which is used to transport 

water from Banner Creek to Chessman Reservoir via a 

metal flume, each diversion collects water into an 

underground pipe for conveyance to the Tenmile Water 

Treatment Plant. The treatment plant, built in 1989-90, 

has a maximum treatment capacity of 9 million gallons 

per day. Figure 2 is a schematic diagram of the water 

sources, reservoirs, diversions, and conveyance system 

for the Tenmile Water Treatment Plant.

STREAMFLOW

Streamflow in Tenmile Creek is highly variable, 

both on a seasonal and an annual basis, throughout the 

upper watershed and understanding the spatial and 

temporal distribution of streamflow is crucial to effective long-term watershed management. The next sections of this report describe historical streamflow, 

recent hydrologic data, and methods for estimation of 

long-term monthly flows throughout the watershed.

Historical Streamflow and Hydrologic Data

A streamflow-gaging station (station 06062500) 

was established by the USGS on Tenmile Creek just 

upstream from Moose Creek near the town of Rimini in 

1914. Daily discharge data were collected from July 

1914 to July 1995, when the station was discontinued. 

The station was re-established in May 1997 to provide 

information for this study. A new streamflow-gaging 

station (06062750) was simultaneously established at 

the Tenmile Water Treatment Plant (figs. 1 and 2). The 

mean annual streamflow of Tenmile Creek for water 

years 1915-94 at the USGS streamflow-gaging station 

near Rimini was 17.3 ft3/s. The maximum instantaneous discharge for the 1915-94 period was 3,290 ft3/s 

on May 22, 1981, and the minimum daily discharge 

was zero ft /s on 45 different days over the period of 

record.

4 Streamflow and Water-Quality Characteristics in the Upper Tenmile Creek Watershed, Lewis and Clark County, West-Central Montana
06062750

Tenmile Water 

Treatment Plant

06062750

15

EXPLANATION

DIVERSION FOR TENMILE WATER 

TREATMENT PLANT

U.S. GEOLOGICAL SURVEY STREAMFLOW GAGING STATION AND NUMBER

" STREAMFLOW ESTIMATION 

SITE AND NUMBER

 BURIED PIPE CONVEYING DIVERTED 

FLOW TO TREATMENT PLANT

 FLUME FROM BANNER CREEK TO 

CHESSMAN RESERVOIR

Figure 2. Water sources, reservoirs, diversions, and conveyance system for the Tenmile Water Treatment Plant near Rimini, Montana.

FIGURE 2 5
Discharge data for the streamflow-gaging station on Tenmile Creek near Rimini are affected by 

upstream water storage and releases at Chessman and 

Scott Reservoirs and diversions from Banner Creek, 

Tenmile Creek at Rimini, Beaver Creek at Rimini, and 

Minnehaha Creek near Rimini (figs. 1 and 2). Diversions for the Tenmile Water Treatment Plant that are 

located on tributaries downstream from the streamflow-gaging station near Rimini (Moose Creek and 

Walker Creek) only affect recorded discharges at the 

new gaging station at the water treatment plant.

Additional Hydrologic Data Collection in 1997

Gages for measuring stream stage were installed 

at 32 locations in May 1997 to obtain additional 

Streamflow information for the upper Tenmile Creek 

watershed. These sites, plus the two continuousrecording streamflow-gaging stations, are listed in 

downstream station order in table 1. These sites were 

installed for one or more of the following three purposes: (1) estimation of long-term monthly discharge, 

(2) water-quality sampling and analysis, and (3) estimation of natural flow for Tenmile Creek near Rimini. 

Twenty-one of these 34 sites were intended for the estimation of long-term monthly natural flows throughout 

the basin, but two (sites 9 and 27) subsequently were 

dropped from further analysis because of very small 

flows. Twenty-one sites, most of which also were used 

for estimation of long-term monthly flows, were established for water-quality sampling and analysis. Sites 

were selected to ensure that Streamflow and waterquality characteristics would be determined for all 

major tributaries as well as mainstem locations where 

flow or water-quality characteristics were expected to 

change as a result of diversions, inflow, or land use.

Nineteen of the 34 sites were established to help 

estimate the natural flow at Tenmile Creek near Rimini 

during 1997 that would have occurred in the absence of 

diversions and storage. These streamflow-estimation 

sites were located upstream and downstream from 

Chessman and Scott Reservoirs, at the Banner Creek 

flume, and upstream and downstream from all streamflow diversions for the Tenmile Water Treatment Plant 

(fig. 1). Ultimately, however, municipal water-use data 

compiled by the Tenmile Water Treatment Plant staff 

were used to determine diversion volumes and calculate natural flows for Tenmile Creek near Rimini. Thus, 

data from nine sites that were established solely for the

purpose of 1997 natural flow estimation (table 1) were 

subsequently used only for verification purposes or not 

used at all.

Several current-meter discharge measurements 

were made at most of the Streamflow data-collection 

sites using standard techniques of the USGS (Rantz and 

others, 1982). The measured discharges were used with 

concurrent water-level (stage) readings to develop 

stage-discharge relationships for each site, as indicated 

by the example graphs in figure 3. Interested basin residents volunteered to periodically record stage at most 

sites throughout the May through October period. The 

stage-discharge relations then were used to determine 

discharge for each stage reading. Discharges determined from the stage-discharge relations are herein 

referred to as observed discharges to differentiate them 

from measured discharges. Discharges determined 

from stage readings in flumes operated by personnel at 

the Tenmile Water Treatment Plant also are referred to 

as observed discharges. Measurement-site description, 

drainage basin size, measurement dates, and measured 

stage and discharge for each site are shown in table 2.

Techniques for Estimation of Long-Term Monthly and Daily 

Discharge

To estimate long-term monthly natural discharges at locations throughout the upper basin, a 

multi-step correlation procedure was used.

Step 1: Water-use data based on metered usage 

and observed discharges for the Tenmile Water Treatment Plant for water years 1991-98 and October 1998 

(first month of water year 1999) and measured discharge data from May through October 1997 for this 

study were used to estimate long-term monthly natural 

discharges for 1961-90, a commonly used base period 

for meteorologic and hydrologic analyses, for Tenmile 

Creek near Rimini.

Step 2: Metered water-use data and observed 

discharges for the Tenmile Water Treatment Plant and 

measured discharge for the current study were used to 

estimate daily natural flows for May through October 

1997 for Tenmile Creek near Rimini.

Step 3: Measured and observed discharges during May through September 1997 at 19 monthly 

flow-estimation sites were regressed with concurrent 

estimated daily natural discharges for Tenmile Creek 

near Rimini. The regression relation then was used to 

estimate long-term monthly natural flows at each of

6 Streamflow and Water-Quality Characteristics in the Upper Tenmile Creek Watershed, Lewis and Clark County, West-Central Montana
A. RUBY CREEK AT MOUTH (site 6)

2.5

in 

O 1.5

 Stage-discharge regression line

 Measured

0.2 0.5 12 5 10 

DISCHARGE, IN CUBIC FEET PER SECOND

20 50

B. WALKER CREEK ABOVE CITY DIVERSION (site 32)

2.5

1.5

u- 0.9 

- 0.8

0.6 

0.5

0.4

0.3 

0.25

1

 Stage-discharge regression line

 Measured

3 4 5 7 10 20 

DISCHARGE, IN CUBIC FEET PER SECOND

30 40 50

Figure 3. Stage-discharge relationships for two sites in the upper Tenmile Creek watershed near Rimini, Montana.

FIGURE 3
the 19 sites from the long-term monthly natural flows 

for Tenmile Creek near Rimini. Each step in the 

correlation procedure is described in detail in the 

following sections of the report.

Estimation of Long-Term Monthly Natural Flows for Tenmile Creek 

near Rimini

As previously described, recorded daily discharges for station 06062500 on Tenmile Creek near 

Rimini are affected by flow diversions for municipal 

water supply on Banner Creek, Tenmile Creek at 

Rimini, Beaver Creek, and Minnehaha Creek (figure 

2). Storage and releases from Scott and Chessman Reservoirs also affect recorded discharges. As shown on 

the schematic diagram in figure 2, diversions from 

Moose and Walker Creeks are downstream from station 

06062500 and do not affect recorded discharges at that 

station.

Total water diverted to the Tenmile Water Treatment Plant is metered daily at the inflow pipe to the 

plant. Personnel at the plant also periodically observe 

discharge at measuring flumes upstream and downstream from Scott Reservoir (sites 4 and 5, respectively), at the Banner Creek diversion (site 8), and 

downstream from Chessman Reservoir (site 15). Net 

daily discharge at each of these sites is estimated by 

interpolating between periodically observed discharges. Net daily discharge into Scott Reservoir is 

computed by subtracting daily discharge at measurement site 5 from daily discharge at site 4. Similarly, net 

daily discharge into Chessman Reservoir is computed 

by subtracting daily discharge at measurement site 15 

from daily discharge at measurement site 8. Net daily 

discharge into either reservoir is negative whenever 

outflow exceeds inflow. Computed net daily discharges are averaged for each month to produce estimates of net monthly mean discharge into each 

reservoir. Daily water-use data for the Tenmile Water 

Treatment Plant for water years 1991-98 and October 

1998 (Jack Williams, Tenmile Water Treatment Plant, 

written commun., 1998) were used to calculate monthly 

mean data shown in table 3.

Access to Scott Reservoir is difficult during early 

runoff conditions in May; consequently, daily discharge into the reservoir probably is often underestimated during runoff periods when site 4 is not 

observed. Likewise, the method used to compute net 

daily discharge into Chessman Reservoir does not 

include Beaver Creek inflows (site 14) or inflows to the

Banner Creek flume from Beaver Creek tributaries 2 

and 3 (sites 16 and 18). Thus, the method also tends to 

underestimate the true net discharge into Chessman 

Reservoir.

To estimate the additional discharge into Scott 

and Chessman Reservoirs, monthly mean water-use 

data for the 1991-98 water years and October 1998 

were used to calculate the average net monthly discharge into each reservoir. As shown in table 3, the 

average monthly net flow into Scott Reservoir was 

-0.71ft3/s, and the average monthly net flow into 

Chessman Reservoir was -0.46 ft3/s. Because both reservoirs are relatively small, it was assumed that they 

would empty and fill annually. On that basis, the true 

average net annual discharge from the reservoirs over 

the 1991-98 period was assumed to be zero. The additional average monthly flow into Scott and Chessman 

Reservoirs necessary to balance the negative inflows 

calculated from water-use data was assumed to be 0.71 

and 0.46 ft /s, respectively. Loss from evaporation was 

assumed to be negligible, due to the small surface areas 

of the two reservoirs. The additional inflow to the reservoirs was considered to occur only during the spring 

runoff period of May and June; therefore, the actual 

distribution of the underestimated annual discharge 

into each reservoir was weighted to the two months of 

May and June. For Scott Reservoir, the average additional May and June inflow required to ensure a true 

average net annual discharge of zero is (0.71 ft3/s x!2 

months)/(2 months), or 4.3 ft3/s. For Chessman Reservoir, the average additional May and June inflow 

required to ensure a true average net annual discharge 

of zero is (0.46 ft /s x 12 months)/(2 months), or 

2.8 ft3/s.

To estimate monthly natural discharge for Tenmile Creek near Rimini (site 28), the combined net 

monthly discharge into the reservoirs is added to 

recorded monthly discharge at the streamflow-gaging 

station. Streamflow losses resulting from natural seepage to ground water between the reservoirs and site 28 

were assumed to be negligible. In addition, discharge 

diverted to the treatment plant, minus that portion 

below the gage that comes from Moose Creek and 

Walker Creek, is added to recorded discharge at the 

streamflow-gaging station. Table 4 shows total 

monthly mean discharge diverted to the treatment plant 

for water years 1991-98 and October 1998; discharge 

from individual diversions is unknown.

Discharges measured during 1997 were used to 

estimate the average diversion from Moose Creek and

8 Streamflow and Water-Quality Characteristics in the Upper Tenmile Creek Watershed, Lewis and Clark County, West-Central Montana
Walker Creek compared to the average diversion from 

Tenmile, Beaver, and Minnehaha Creeks . Based on 

information from operators at the Tenmile Water Treatment Plant (Leonard Willett, oral commun., 1998), 

diversions from each stream are roughly proportional 

to their discharges. Based on four approximately concurrent measurements of discharge at the measurement 

site above each diversion in mid-May, early June, early 

August, and late August, the combined discharges for 

Moose andWalker Creeks were about 0.20 times (20 

percent) the combined discharges for Tenmile, Beaver, 

and Minnehaha Creeks. Thus, the average annual 

diversion from Moose and Walker Creeks was assumed 

to be 20 percent of the average annual diversion from 

Tenmile, Beaver, and Minnehaha Creeks. On this 

basis, total average annual diversion to the Tenmile 

Water Treatment Plant would equal the average annual 

diversion to the Tenmile, Beaver, and Minnehaha 

Creeks plus 0.20 times the average annual diversion 

from Tenmile, Beaver, and Minnehaha Creeks. Stated 

another way, the average annual diversion from Tenmile, Beaver, and Minnehaha Creeks equals the total 

average annual diversion to the treatment plant divided 

by 1.20, or 83 percent of the total average annual diversion. Estimated monthly discharges diverted from Tenmile, Beaver, and Minnehaha Creeks for water years 

1991-98 and October 1998 were estimated to be 83 percent of the total monthly discharges diverted to the Tenmile Water Treatment Plant (table 4).

Estimated monthly discharges diverted to the 

Tenmile Water Treatment Plant from Tenmile, Beaver, 

and Minnehaha Creeks then were added to the combined estimated net monthly discharges into Scott and 

Chessman Reservoirs. The results, termed natural flow 

accretions, represent the difference between recorded 

monthly discharges and natural monthly discharges for 

Tenmile Creek near Rimini. These natural flow accretions and their averages for water years 1991-98 and 

October 1998 are listed in table 5.

Although no data for natural flow accretions are 

available before water year 1991, estimated water-use 

data compiled by the City of Helena for 1978-97 

(Leonard Willett, written commun., 1998) indicate that 

the average annual municipal water supply from the 

Tenmile Creek basin for water years 1978-97 (5.4 ft3/s) 

was about the same as that for water years 1991-98 and 

October 1998 (5.6 ft3/s). On this basis, the average natural flow accretions for water years 1991-98 and October 1998 are assumed to be the same as for the longer 

1978-97 period. The 1978-97 base period, because of

its short length, is not considered a suitable base period 

for the estimation of long-term mean flows for the 

upper Tenmile Creek basin. Accordingly, a 30-year 

base period including water years 1961-90, which is a 

common length of record used for long-term climatic 

comparisons, was used for the estimation of long-term 

flows in the Tenmile Creek basin. The average natural 

flow accretions for the 1991-98 period also were 

assumed to be the same as those for 1961 -90. Although 

municipal water use in Helena has likely increased over 

the years due to increasing population, efficiency of the 

Tenmile water delivery system also has improved as 

leaky wooden supply lines have been replaced by steel 

pipes. Increasing municipal demands for water in Helena also have partially been met since 1959 by water 

supplied from the Missouri River. For these reasons, 

the assumption that natural flow accretions for Tenmile 

Creek have remained relatively constant since 1961 

seemed reasonable.

Estimated average monthly natural discharges 

for the 1961-90 base period for Tenmile Creek near 

Rimini were calculated by adding average natural flow 

accretions to average monthly recorded discharges for 

the 1961-90 base period (table 6). Estimated average 

monthly natural discharges are graphically compared 

to monthly recorded discharges in figure 4. As shown 

in table 6 and figure 4, differences between natural and 

recorded discharges are greatest in May and June when 

streamflows are naturally high from snowmelt runoff 

and Scott and Chessman Reservoirs are being filled. 

Differences between natural and recorded discharges 

are least in December, January, and February when 

streamflows are naturally low, and diversions to the 

Tenmile Water Treatment Plant are largely supplied 

from Chessman and Scott Reservoir releases.

Estimation of Daily Natural Discharge for May-October 1997 for 

Tenmile Creek near Rimini

To estimate daily natural discharge for Tenmile 

Creek near Rimini for the May-October 1997 period, 

daily water-use data supplied by personnel at the Tenmile Water Treatment Plant were used. The procedure 

for estimation of daily natural discharge was similar to 

that for the estimation of long-term monthly natural 

flows. Daily discharges diverted to the Tenmile Water 

Treatment Plant from Tenmile, Beaver, and Minnehaha 

Creeks were added to the combined net daily discharges into Scott and Chessman Reservoirs to produce 

estimated daily natural flow accretions for the gage at

STREAMFLOW
120

100

80

LU 

UO 60

CD 

O 

? 40

LU

O

EC

20

Recorded 

Natural

Oct Nov Dec Jan Feb Mar Apr May June July Aug Sept

Figure 4. Recorded and estimated average monthly natural discharge for Tenmile Creek near Rimini, Montana (site 28), 

water years 1961 -90.

Tenmile Creek near Rimini. The estimated natural 

flow accretions were added to the recorded discharges 

for Tenmile Creek near Rimini to produce estimates of 

daily natural flow for the May through October 1997 

period. Calculations were simpler than those required 

for estimation of long-term monthly natural discharges, 

because no diversions to the Tenmile Water Treatment 

Plant were made from Moose Creek or Walker Creek 

during May through October 1997.

As previously described, data for discharge into 

Scott and Chessman Reservoirs do not account for 

early-season inflows to Scott Reservoir or for inflows 

to Chessman Reservoir from Beaver Creek or its tributaries. To estimate the additional daily discharge into 

Scott and Chessman Reservoirs during May through 

October 1997, the previously calculated average values 

for May and June were used together with the distribution of daily recorded discharge for Tenmile Creek near 

Rimini for May and June. The total discharge volume 

for May and June 1997 for Tenmile Creek near Rimini 

was the sum of all daily discharges over the 61-day 

period, or 6,248 ft3/s-days. For that same 61-day 

period, the total additional inflow volume to Scott Reservoir was 4.3 ft3/s x 61 days, or 262 ft3/s-days, and the 

total additional inflow volume to Chessman Reservoir 

was 2.8 ft3/s x 61 days, or 171 ft3/days. The additional 

inflow volume for Scott Reservoir was (262/6,248), or 

4.2 percent of the discharge volume for Tenmile Creek 

near Rimini. Similarly, the additional inflow volume 

for Chessman Reservoir was (171/6,248), or 2.7 percent of the discharge volume for Tenmile Creek near 

Rimini. Thus, for example, the estimated additional 

inflow for Scott Reservoir on May 1, when the 

recorded daily discharge for Tenmile Creek near 

Rimini was 25 ft3/s, was 4.2 percent of 25 ft3/s, or 1.0 

ft3/s. Similarly, the estimated additional inflow to 

Chessman Reservoir on May was 2.7 percent of 

25 ft3/s, or 0.68 ft3/s.

Recorded daily discharge, estimated daily natural flow accretions, and estimated daily natural discharge for Tenmile Creek near Rimini for May 1 

through October 31, 1997 are displayed graphically in 

figure 5. Figure 5 indicates that the largest daily natural 

flow accretions occurred in May and June, and the 

smallest occurred in October.

Measured and observed discharges at sites above 

and below the diversion structures on Tenmile Creek at 

Rimini, Beaver Creek at Rimini, and Minnehaha Creek 

near Rimini were used to estimate the proportion of 

flow diverted to the Tenmile Water Treatment Plant 

from each diversion during May 1 through October 31, 

1997. Monthly average discharge diverted and the total 

May through October average discharge diverted at the 

three diversions are shown in figure 6. As indicated by 

the average values for the period (figure 6), the greatest 

amount of flow (about 48 percent) was provided by the 

Beaver Creek diversion, while about equal amounts 

(about 26 percent each) were supplied by the Tenmile 

Creek and Minnehaha Creek diversions.

10 Streamflow and Water-Quality Characteristics in the Upper Tenmile Creek Watershed, Lewis and Clark County, West-Central Montana
240

220

200

il80

UJ

to 160 

cc Hi 

a. 

K 140

UJ 

HI 

U.

9 120 

CO

o

z 100

uj 

<D 

CC 80

§

40

20

0

Estimated natural flow accretion 

Recorded discharge 

Estimated natural discharge

May June July

1997

August September October

Figure 5. Recorded daily discharge and estimated natural flow accretion and natural daily discharge for Tenmile Creek near Rimini, 

Montana (site 28), May-October 1997.

Estimation of Long-Term Monthly Natural Discharge for Selected Sites

In addition to the previously described techniques used to estimate long-term monthly natural discharge for Tenmile Creek near Rimini, regression 

analysis was used to estimate long-term monthly natural discharge at each of the other 18 flow-estimation 

sites. Each measured and observed discharge (Y value) 

was paired with the concurrent estimated daily natural 

discharge for Tenmile Creek near Rimini (X value). An 

Ordinary Least Squares (OLS) regression line was fit to 

the base 10 logarithms of the paired data. The relation 

of daily values was assumed to also represent the relation of monthly discharges and, therefore, was subsequently used to estimate long-term monthly discharge. 

The resultant equations for the regression lines may be 

expressed in the following log-linear form,

Y = a1 XL (1)

where

Y is the daily or monthly discharge for the 

estimation site, in cubic feet per second;

X is the daily or monthly natural discharge 

for Tenmile Creek near Rimini, in cubic 

feet per second;

a' is the anti-log of the linear regression constant (a1 =10a), and;

b is the linear regression coefficient.

The a' and b values for the regression equations and 

two measures of regression reliability, the coefficient 

of determination (R2), and the standard error of 

estimate (SE), for all estimation sites are shown in 

table 7. The coefficient of determination is a measure 

of the percentage of the variation in Y that is 

accounted for by the regression equation. The 

standard error of estimate is a measure of the 

dispersion of the data around the regression line.

In general, the larger the value of R and the 

smaller the value of SE, the more reliable is the regression equation. The regressions for all sites but one had

FIGURE 5 11

:&,.
6.5 

6.0

5.5

Q 

£5.0 8

4.5 £D.

UJ 4.0

B

O 

5 3.5

£2.5

UJ

£2.0

I iu 1.5

1.0 -

0.5 -

0

I I Beaver Creek

^^H Tenmile Creek

I I Minnehaha Creek

I

May June July Aug Sept Oct May-Oct

Figure 6. Monthly and seasonal average diversions from Beaver Creek, Tenmile Creek, and Minnehaha Creek near Rimini, Montana, 

May-October 1997.

relatively large values for R (0.70 or greater) and for 

all had small values of SE (0.06-0.21) (table 7). 

Moore's Spring Creek (site 24), where measured and 

observed discharges were very small and relatively 

constant throughout the May through October 

measurement period, was the only site that lacked a 

significant correlation to flow at Tenmile Creek near 

Rimini. The regression equation for Moore's Spring 

Creek, with a p-value of 0.78, was the only one that 

was not statistically significant. The p-value 

represents the probability that the regression equation 

is not significant. All other regression equations had 

p values less than 0.01 and thus were statistically 

significant.

Two of the "worst" (sites 24 and 31) and one of 

the "best" (site 3) regressions in terms of the values of 

R2 and SE in table 7 are shown graphically in figure 7. 

The logarithms of estimated natural discharge for Tenmile Creek near Rimini are only very weakly correlated 

with measured and observed discharges for Moore's

Spring Creek (fig. 7A) but are more strongly correlated 

with measured and observed discharges for Bear Gulch 

(fig. 7B). In contrast, estimated natural discharges for 

Tenmile Creek near Rimini are very strongly correlated 

with measured and observed discharges for Tenmile 

Creek above Ruby Creek (fig. 7C). Similarly strong 

correlations exist for most of the streamflow-estimation sites.

To calculate long-term monthly natural discharge for an estimation site, each monthly value of 

long-term natural discharge for Tenmile Creek near 

Rimini (table 6) was entered as the X value in equation 

1, together with appropriate values of a' and b from 

table 7. For example, the long-term October discharge 

for Monitor Creek (site 1), Y, was estimated from the 

long-term October natural discharge for Tenmile Creek 

near Rimini (6.1 ft3/s) as follows:

Y = a'Xb,

12 Streamnow and Water-Quality Characteristics in the Upper Tenmile Creek Watershed, Lewis and Clark County, West-Central Montana
A. Moore's Spring Creek (site 24) B. Bear Gulch (site 31)

IU

7

5

Q . 

z 4

8 3

(_> O

HI

OT

OC 2

01

Q.

in

K 1

o

5 0.7

1 «

- 0.4

UJ

0 0.2

w

Q

0.1

0.07

DOR

. i i i ' ' i i .

_ _

: R 2 = 0.01 ;SE = 0.18 log units :

 _

- -

 

_ _

.

-

-

l -

'- * -

- * '-

A. :

i - " " :

- * * 

- -

'- -_

~ i i i i 1 i 1 , ,!,..,! , 1 i

10 20 50 100 200 500

NATURAL DISCHARGE FOR TENMILE CREEK 

NEAR RIMINI, IN CUBIC FEET PER SECOND

1 

0.7

0.5 

0.4

0.3 

0.2

0.1 

0.07

0.05

10

R 2 = 0.70; SE = 0.21 log units

20 50 100 200 500

NATURAL DISCHARGE FOR TENMILE CREEK 

NEAR RIMINI, IN CUBIC FEET PER SECOND

C. Tenmile Creek above Ruby Creek (site 3)

100

70

50

40

30

0.7 

0.5

R 2 = 0.98 ;SE = 0.07 log units

10 20 50 100 200

NATURAL DISCHARGE FOR TENMILE CREEK 

NEAR RIMINI, IN CUBIC FEET PER SECOND

500

EXPLANATION 

REGRESSION LINE

MEASURED OR OBSERVED 

DISCHARGE

Figure 7. Regression lines relating measured and observed discharge data for Moore's Spring Creek, Bear Gulch, and Tenmile Creek 

above Ruby Creek to concurrent estimated daily natural discharge for Tenmile Creek near Rimini, Montana (site 28).

FIGURE 7 13
where:

a' and b from table 7 are 0.026 and 1.12,

respectively; and 

X is6.1ft3/s.

Thus,

Y = (0.026) (6.1) 1 ' 12 ,

Y = (0.026) (7.6),

Y = 0.20 ft3/s.

In a similar manner, long-term mean monthly 

natural discharges for all months and all estimation 

sites were calculated and are shown in table 8. Also 

shown in table 8 are estimates of long-term mean

annual natural discharge for each site. Long-term mean 

annual natural discharge was calculated by multiplying 

each long-term mean monthly natural discharge by the 

number of days in the month, summing the 12 resultant 

values, and dividing the sum by 365 days.

Results in table 8 are displayed graphically in 

figures 8 through 12. Figure 8 shows the long-term 

monthly natural discharge estimates for smaller 

streams in the watershed and indicates that Moore's 

Spring Creek (site 24) flows generally had less variation than flows for other small tributaries. Figure 9 

shows long-term monthly natural discharge estimates

Poison Creek at mouth (site 11) 

Moore's Spring Creek at mouth (site 24) 

D Bear Gulch at mouth (site 31)

Oct Nov Dec Jan July Aug Sept

Figure 8. Estimated long-term monthly natural discharge for small tributary streams, upper Tenmile Creek watershed near Rimini, 

Montana.

10

 Monitor Creek at mouth (site 1)

H Ruby Creek at mouth (site 6)

D Spring Creek at mouth (site 22)

D Moose Creek above city diversion (site 29)

=DL =0.

Oct Nov Dec Jan Feb Mar May June July Aug Sept

Figure 9. Estimated long-term monthly natural discharge for mid-size tributary streams, upper Tenmile Creek watershed near Rimini, 

Montana.

14 Streamflow and Water-Quality Characteristics in the Upper Tenmile Creek Watershed, Lewis and Clark County, West-Central Montana
for mid-sized Tenmile Creek tributaries and indicates 

that Moose Creek (site 29) flows generally had less 

variation than other mid-sized tributaries. Figure 10 

shows long-term monthly natural discharge estimates 

for the three Beaver Creek tributaries and indicates 

that tributaries 1 and 2 have similar flows with less 

variation than those of tributary 3. Long-term monthly 

natural discharge estimates for the largest Tenmile 

Creek tributaries are compared in figure 11. Figure 11 

shows that estimated long-term monthly natural 

discharges for Beaver Creek (site 20) and Minnehaha 

Creek (site 25) are similar in magnitude and

variability, and that monthly natural discharges for 

Walker Creek (site 32), the tributary with the largest 

drainage area (table 2), are less than those for the other 

large tributaries. Finally, figure 12 shows long-term 

monthly natural discharge estimates for the mainstem 

sites on Tenmile Creek. Figure 12 shows that monthly 

natural discharge for Tenmile Creek increases in the 

downstream direction, as a result of tributary inflows.

Long-term annual natural discharges for all estimation sites are compared in figure 13. Figure 13 

shows the pattern of natural discharge increases in Tenmile Creek in the downstream direction and the relative

 Beaver Creek tributary 3 (site 16)

9 Beaver Creek tributary 2 (site 18)

D Beaver Creek tributary 1 (site 19)

Oct Nov Dec Jan Feb Mar Apr Sept

Figure 10. Estimated long-term monthly natural discharge for Beaver Creek tributaries, upper Tenmile Creek watershed near Rimini, 

Montana.

 Banner Creek above city diversion (site 7)

 Beaver Creek above city diversion (site 20)

D Minnehaha Creek above city diversion (site 25)

D Walker Creek above city diversion (site 32)

Nov Dec Jan Feb Mar Apr May June July Aug Sept

Figure 11. Estimated long-term monthly natural discharge for large tributary streams, upper Tenmile Creek watershed near Rimini, 

Montana.

STREAMFLOW IS
140

120

CO

DC 100

Ul Q.

O 

55

O 60

Ul

g 40

<

O

2°

 Below Monitor Creek (site 2)

B Above Ruby Creek (site 3)

D Above city diversion (site 12)

Q Near Rimini (site 28)

 At Tenmile Water Treatment Plant (site 34) 

(06062750)

July Aug Sept

Figure 12. Estimated long-term monthly natural discharge for mainstem Tenmile Creek, upper Tenmile Creek watershed near Rimini, 

Montana.

flow contribution from each tributary. Figure 14 shows 

the annual natural discharge for each site divided by 

drainage area and provides an indication of which 

streams produce the most estimated natural runoff per 

square mile. Figure 14 shows that Spring Creek (site 

22) produces the most natural runoff per square mile, 

and Bear Gulch (site 31) produces the least natural runoff per square mile. Of the streams that currently supply water to the Tenmile Water Treatment Plant, 

Banner Creek (site 7) produces the most natural runoff 

per square mile, and Walker Creek (site 32) produces 

the least natural runoff per square mile.

Reliability of Long-Term Monthly Discharge Estimates

Gaged data from a nearby stream (Prickly Pear 

Creek) were used to test the reliability of the long-term 

monthly discharge estimates. Prickly Pear Creek arises 

in the Northern Rocky Mountains south of the Tenmile 

Creek basin and has a streamflow-gaging station 

(06061500) near Clancy, Montana. Although the 

drainage area for the streamflow-gaging station on 

Prickly Pear Creek (192 square miles) is larger than 

that for Tenmile Creek near Rimini, the two watersheds 

were considered to be hydrologically similar based on 

similarity of recorded flow statistics.

Twenty dates between May 1 and October 31, 

1997 were randomly selected for the test of reliability 

of monthly natural discharge estimates. For each randomly selected date, the daily mean discharge from the 

record at the streamflow-gaging station on Prickly Pear 

Creek was considered to be the measured or observed 

discharge used for regression with concurrent estimated natural daily discharge for Tenmile Creek near 

Rimini. The results of the regression indicate a strong 

relation between daily flows for the two sites (figure 

15), especially for lower flows. The equation for the 

regression line shown in figure 15 then was used to calculate long-term mean monthly discharges for Prickly 

Pear Creek from the long-term mean monthly natural 

discharges for Tenmile Creek near Rimini. The calculated monthly means were compared with monthly 

means from the actual record for the period 1961-90 in 

figure 16. Estimation errors (percent differences 

between actual means and estimated means) ranged 

from -6.6 percent in February to 14.2 percent in 

August. Overall, the average error for estimated mean 

annual discharge at the Prickly Pear Creek site was 3.9 

percent. Based on the test results of the streamflow 

correlation method, estimation errors for most flowestimation sites in the upper Tenmile Creek basin may 

be considered to be about the same or slightly larger 

then those for Prickly Pear Creek. Flow-estimation 

sites having small R2 and large SE are likely to have 

larger estimation errors than the test site. However, 

most sites having poor R2 and SE also had small 

monthly discharges; consequently, larger percent errors 

do not necessarily represent large flow volumes.

16 Streamflow and Water-Quality Characteristics in the Upper Tenmile Creek Watershed, Lewis and Clark County, West-Central Montana
26

26

24

22

20

iti

to 18 

o: LU

CL

H 16

y 14

CD

o

Z 12

iif 

CD

cc 10 

o

£ 8

Upstream Downstream

Streams and locations on Tenmile Creek that do not supply water

to Tenmile Water Treatment Plant 

Streams and locations on Tenmile Creek that supply water

to Tenmile Water Treatment Plant

Figure 13. Estimated long-term annual natural discharge for streams in the upper Tenmile Creek watershed near Rimini, Montana.

Determination of Gaining and Losing Stream Reaches on 

Tenmile Creek

Diversions for the Tenmile Water Treatment 

Plant often dewater Tenmile Creek, particularly in 

Rimini from the Tenmile Creek diversion to the mouth 

of Spring Creek, a distance of about 0.5 mile. The 

elimination of existing diversion structures and

replacement with a single mainstem diversion at the 

Tenmile Water Treatment Plant has been suggested to . minimize mainstem dewatering caused by diversions. 

Although this kind of change in water management 

would alleviate dewatering problems, it might result in 

a loss of water available to the Tenmile Water Treatment Plant if significant flow losses occur in the channel between Rimini and the plant.

FIGURE 13 11
 v:-^*

:

: *-

1.4

^ 1-2

5

ui

Upstream Downstream

I I Streams and locations on Tenmile Creek that do not supply water

to Tenmile Water Treatment Plant 

H Streams and locations on Tenmile Creek that supply water

to Tenmile Water Treatment Plant

Figure 14. Estimated long-term annual unit natural discharge for streams in the upper Tenmile Creek watershed near Rimini, Montana.

To help determine whether such flow losses are 

evident, two series of synoptic discharge measurements at selected locations on Tenmile Creek were 

made during very low-flow conditions on September 6, 

1998 and during slightly greater flow conditions on 

July 14, 1999. All measurements during each series 

were made over the course of a single day when flows 

at the gaging stations near Rimini (06062500) and the

Tenmile Water Treatment Plant (06062750) were relatively steady. For example, discharge at station 

06062500 varied by only 0.1 cubic feet per second 

throughout the day on September 6,1998 and by only 

0.2 cubic foot per second on July 14, 1999. Likewise, 

discharge at station 06062750 varied by 0.1 cubic foot 

per second throughout the day on September 6, 1998 

and by about 0.4 cubic foot per second on July 14,

18 Streamflow and Water-Quality Characteristics in the Upper Tenmile Creek Watershed, Lewis and Clark County, West-Central Montana
Q

0

HI

£

LU

500

400

3°°

250

200

150

CO

O 100 

S 90 

£ 80

g 70 

O

oc 60

LU

CL 50

O 40

Lr

DL

S 30

LU

| 25 

O 20

5

15

10

Regression line, R 2 = 0.95, SE = 0.06 log units 

Daily discharge

12 5 10 20 50 100 200 500 

ESTIMATED DAILY MEAN NATURAL DISCHARGE IN TENMILE CREEK NEAR RIMINI (06062500), 

IN CUBIC FEET PER SECOND

Figure 15. Regression relationship between selected daily mean discharge for Prickly Pear Creek (station 06061500) and estimated 

daily mean natural discharge for Tenmile Creek near Rimini (site 28), Montana.

HI 

UL

o 100

m Q 

8 O 80

 LU

LU 60

J °" 40 

Q 20 

n

- D

n

Estimated

Recorded 1961-90

m m

PI

[

 i

._

-

i i -

Oct Nov Dec Jan Feb Mar Apr May June July Aug Sept

Figure 16. Comparison between estimated and recorded long-term mean monthly discharge for Prickly Pear Creek (station 06061500), 

Montana.

FIGURES IS AND 16 19
1999. Except for Minnehaha Creek, which had an 

estimated discharge of less than 0.1 cubic foot per 

second, all tributary streams were dry on September 6, 

1998. On July 14, 1999, Minnehaha Creek was dry, 

but Moose Creek and Walker Creek had small 

discharges. Steady flow conditions and minimal 

tributary inflows help to ensure that site-to-site 

differences in measured discharge are attributable to 

gains from or losses to the shallow ground water 

system and not to the transient effects of upstream 

flow changes.

Measured discharges at selected mainstem locations are plotted on figure 17. Discharge generally

increased gradually downstream from the city diversion in Rimini to the mouth ofWalker Creek. From 

Walker Creek to the Tenmile Water Treatment Plant, 

discharge decreased during both series of measurements.

Estimates of the measurement error at each site 

also are plotted on figure 17. Measurement error was 

based on a subjective evaluation of the measuring conditions (channel and flow irregularities) at each site as 

noted on the hydrographer's discharge measurement 

note. For most measurements, the error was conservatively selected as ±10 percent. Because of the measurement error, apparent small gains or losses in discharge

Estimated 10 percent error bar 

Discharge, Septembers, 1998 

Discharge, July 14,1999

34567 

DISTANCE, IN MILES FROM CITY DIVERSION IN RIMINI

Figure 17. Measured discharge and estimated error, September 6,1998, and July 14,1999, Tenmile Creek, upper Tenmile Creek 

watershed near Rimini, Montana.

20 Streamflow and Water-Quality Characteristics in the Upper Tenmile Creek Watershed, Lewis and Clark County, West-Central Montana
between adjacent sites shown in figure 17 may not be 

real if the value lies within the range of the adjacent 

error bar. However, the overall increase in discharge 

from the upstream end of the measurement reach at 

Rimini to the mouth of Walker Creek was greater than 

the error range during both series of measurements and 

signifies an actual gain in streamflow. Because this 

increase in discharge is greater than the inflows from 

tributaries, the gains are probably from ground water 

inflow. Therefore, the reach of Tenmile Creek from 

Rimini to Walker Creek can be characterized as a gaining reach. The overall decrease in discharge from 

Walker Creek to the Tenmile Water Treatment Plant 

also was greater than the error range during both series 

of measurements and indicates streamflow losses to the 

ground-water system (losing reach).

Overall, the difference in discharge between the 

uppermost site at Rimini and the Tenmile Water Treatment Plant was relatively small (0.4 ft3/s) on September 6,1998, although this difference represents a threefold increase. On July 14, 1999 streamflow increased 

significantly (2.1 ft3/s) from the diversion in Rimini to 

the Tenmile Water Treatment Plant. This increase was 

substantially greater than the tributary inflows, indicating that streamflow gains in the reach between Rimini 

and Walker Creek generally are sufficient to offset 

losses in the reach between Walker Creek and the treatment plant. A tracer-injection study using sodium 

chloride, a conservative chemical tracer, provided general confirmation of gaining and losing reaches as 

described by the current meter discharge measurements 

(Thomas E. Cleasby, U.S. Geological Survey, oral 

cornmun., 2000).

WATER-QUALITY

Stream water was sampled over a wide range of 

flows and analyzed for various chemical constituents to 

gain an understanding of current water-quality conditions throughout the upper Tenmile Creek watershed. 

In addition, samples of bottom sediment from Chessman Reservoir, a major source of municipal water supply, were analyzed for trace-metal concentrations. A 

description of sampling sites and potential sources of 

water-quality degradation, the strategy for sample collection and analysis, methods of sampling and analysis, 

quality assurance procedures, and a general discussion 

of results are presented in the following sections of the 

report.

Strategy for Sample Collection and Analysis

Stream water was sampled during May through 

October 1997 at 21 locations in the upper Tenmile 

Creek watershed. Samples were collected at multiple 

locations on Beaver Creek and Tenmile Creek, streams 

that provide most of the municipal water supply to the 

Tenmile Water Treatment Plant. In addition, sampling 

sites were selected at the mouths of major tributaries to 

Tenmile Creek (table 9). Most sites were sampled 

twice during high-flow conditions in May and June and 

twice during near base-flow conditions in August and 

October.

However, not all sites were sampled four times 

(table 9). Monitor Creek at mouth (site 1) could not be 

sampled in May and June because of difficult site 

access. Sampling at Tenmile Creek below Monitor 

Creek (site 2) was discontinued after June because preliminary laboratory analyses indicated that water quality was nearly identical to that just downstream at 

Tenmile Creek above Ruby Creek (site 3). Banner 

Creek above city diversion (site 7) could not be sampled in May because snow conditions prevented access. 

Banner Creek tributary (site 9) could not be sampled in 

May because of difficult site access and was sampled 

the only time it was found flowing during base-flow 

conditions in August. Tenmile Creek above city diversion (site 12) also could not be sampled in May because 

the stream could not safely be waded during the high 

flow. Nearby sites on Banner Creek (site 10) and Tenmile Creek (site 13) were substituted for sites 7 and 12 

respectively during the May high flow because the 

magnitude of intervening diversions relative to the 

instream flows are negligible. Beaver Creek above 

tributary 3 (site 15) at the outlet of Chessman Reservoir 

was sampled only in August and October because no 

water from the reservoir was being released during 

sampling times in May and June.

During each of the four sampling episodes in 

May, June, August, and October, samples were collected within a 2- or 3-day period to minimize changes 

in water-quality resulting from changing weather and 

streamflow. Streamflow was determined at the time of 

sampling either by direct measurement or from a previously established stage-discharge relationship.

Water samples were analyzed for concentrations 

of major ions, nutrients, trace elements, and suspended 

sediment. Concentrations of trace elements likely to be 

associated with hard-rock mining and the naturally 

high metal content of the local rock formations were of

WATER-QUALITY 21
special concern in this study. Thus, concentrations of 

the trace elements arsenic, cadmium, copper, lead, and 

zinc were analyzed both for the dissolved and totalrecoverable phases. Laboratory methods, minimum 

reporting levels, and water-quality standards for human 

health and aquatic life for the sampled constituents are 

presented in table 10.

Copper sulfate, a chemical commonly added to 

water in Chessman Reservoir to retard algae growth in 

late summer, was considered a potential source of elevated copper concentrations in water released from 

Chessman Reservoir. Samples of bottom sediment 

from selected sites in and near the reservoir were analyzed for concentrations of arsenic, cadmium, chromium, copper, lead, and zinc to help determine whether 

the copper sulfate was accumulating in bottom sediments of Chessman Reservoir and whether trace elements other than copper might be present. One bottomsediment sampling site was located just upstream from 

the reservoir in a natural wetland area. This site, which 

is outside the area of copper sulfate application, was 

sampled to help determine if copper concentrations in 

bottom sediment in Chessman Reservoir were attributable to copper sulfate application to the reservoir or 

from natural sources upstream from the reservoir. The 

reporting limits for all trace elements was 0.001 mg/L, 

with the exception of lead, which was 0.01 mg/L.

Methods of Sample Collection and Analysis

Water and bottom-sediment samples were collected and analyzed using standard methods. Those 

methods are explained in the following sections.

Water Sampling

Water samples were collected by either depth 

integration at multiple stream verticals using methods 

described by Knapton (1985), Edwards and Glysson 

(1988), and Ward and Harr (1990), or by grab sampling 

at sites where streamflow was very small. Water temperature, pH, and specific conductance were measured 

in the field according to standard methods described by 

the U.S. Geological Survey (1977) and Knapton 

(1985).

Depth-integrated samples were collected with a 

polyethylene DH-81 hand-held sampler with a nylon 

nozzle and composited in a polyethylene churn-splitter.

Suspended-sediment samples were collected in glass 

bottles using a DH-48 hand-held sediment sampler. 

Pre-processed samples were protected from atmospheric contamination by using a churn-splitter modified with a cappable funnel. The churn's exterior was 

protected using a large plastic container. Samples were 

handled using vinyl gloves that were frequently 

changed between sample collection, sample processing, and equipment decontamination. Bottles and 

equipment were prepared in the laboratory and samples 

were processed, filtered, and preserved in the field as 

described by Horowitz and others (1994).

Sample processing was completed using a processing chamber to reduce and eliminate potentially 

derived atmospheric inputs. All samples for dissolved 

trace metal analysis were passed through a 0.45-micron 

filter to remove suspended material. Samples were 

processed and preserved using procedures described by 

Horowitz and others (1994).

Chemical analyses of water-quality samples 

were completed by Montana Tunnels, Inc. Aluminum, 

chromium, iron, manganese, nickel, silver, and zinc 

were analyzed by inductively coupled plasma spectroscopy. Arsenic, cadmium, copper, lead, and selenium 

were analyzed by graphite furnace atomic absorption. 

Mercury was analyzed by flow injection cold vapor/ 

hydride. Both graphite furnace atomic absorption and 

flow injection cold vapor/hydride were used to determine concentrations of arsenic in bottom sediment 

(U.S. Environmental Protection Agency, 1983). The 

Montana Tunnels Laboratory participated in a standard 

reference program and was certified by the USGS 

National Water Quality Laboratory (NWQL), Denver, 

Colo., for this project. The quality control and assurance methods used by the Montana Tunnels Laboratory 

are described in a Quality Assurance Manual (Montana 

Tunnels Mining, Inc., 1997).

Suspended-sediment samples were analyzed for 

concentration and particle-size distribution (percent 

finer than 0.062 mm diameter) by the USGS sediment 

laboratory in Helena, Montana. Methods and qualityassurance procedures used to analyze suspended sediment are described by Lambing and Dodge (1993).

Bottom-sediment sampling

Bottom-sediment samples were collected in 

varying water depths not exceeding 4 ft. Samples were 

collected using a BMH-53 hand-held, stainless steel

22 Streamflow and Water-Quality Characteristics in the Upper Tenmile Creek Watershed, Lewis and Clark County, West-Central Montana
coring device. To provide a composite sample at each 

site, several samples of bottom sediment were collected 

at locations several feet apart and added together. Two 

composited samples from different depths were 

obtained from one location (sites R2A and R2B) to 

determine whether trace-metal concentrations varied 

with depth. Samples were collected from the upper 9 

in. of the bottom sediments and were composited using 

new, plastic kitchenware including a plastic spatula, a 

plastic spoon, and a rinsed white dishpan. Equipment 

was rinsed between samples using deionized water. 

Composited bottom-sediment samples were stored and 

shipped in plastic freezer bags. Samples were submitted to the NWQL for the determination of total traceelement concentrations in sediment.

Samples for trace-element analyses were air 

dried in the laboratory and then crushed and sieved 

through a 230-mesh (0.063-mm) nonmetal screen. The 

fraction of particles smaller than 0.063 mm was 

retained and analyzed using methods described in Severson and others (1987).

Quality Assurance

The effectiveness of quality-assurance practices 

is measured by quality-control data that document possible sample contamination and reproducibility of analytical results. These data were provided by test 

samples that consisted of a field-blank sample of deionized water or a replicate environmental sample incorporated into the routine sample sets submitted to the 

laboratory. A field-blank sample of deionized water is 

treated as an environmental sample in all aspects, 

including exposure to sampling equipment, sample 

containers, filtration apparatus, chemical preservatives 

in the field, holding times, and laboratory processing. 

A replicate environmental sample is a volume of sampled material split into subsamples in such a manner 

that the physical and chemical characteristics of each 

subsample are considered essentially identical in composition.

Quality-control samples comprised approximately 10 percent of the total number of water samples 

submitted for analysis. Quality-control samples for 

water-quality analyses consisted of two deionized 

water blanks and two replicates per sampling trip. Two 

replicate samples were analyzed by the NWQL to provide some comparison of analytical results from two 

independent laboratories.

Deionized water blanks should contain no detectable concentrations of analytes. If detectable concentrations occur, then the magnitude and persistence of 

the values need to be examined in order to evaluate the 

possible source of contamination and subsequent effect 

of bias in the overall database. When detection of an 

analyte occurs in a sample blank, it is necessary to evaluate the potential effect on the corresponding environmental sample results. In general, sample-blank 

concentrations that are twice the minimum reporting 

level or less are considered acceptable due to the limits 

of precision at the minimum range of the analytical 

method. Results for blank samples that are greater than 

twice the minimum reporting level indicate possible 

contamination introduced during either the sampling or 

analytical process. A one-time detectable, small concentration of an analyte is too random to isolate the 

source of contamination and will likely have little 

effect on the overall bias of the database. However, 

persistent occurrence of detectable concentrations in 

blanks for the same constituent indicates that bias may 

be widespread and the environmental data for that constituent may be questionable. If the detectable concentrations are both large and persistent, all data for that 

constituent are probably unreliable.

Measurable concentrations of some analytes 

were detected in deionized water blanks during the 

study. Zinc contamination of the field blanks was especially large and persistent. The concentration of dissolved zinc was 40 (ig/L in the June field blank, and the 

concentration of total recoverable zinc was 100 |ig/L in 

the August field blank. Complicating this occurrence of 

contamination indicated by high zinc concentrations in 

field blanks was the fact that several environmental 

samples had zinc concentrations below detection levels. Thus, the contamination occurred in a very irregular pattern.

A suite of blank samples was prepared and analyzed in October 1997 to determine whether the sporadic zinc contamination could be associated with the 

sample collection bottles or the acid used to preserve 

water-quality samples. Five blank samples were prepared using a combination of sample bottles and preservatives from both the routine supplier used during 

the study and from the NWQL. Two samples preserved 

with nitric acid preservative from the routine supplier 

had zinc concentrations of 10 and 70 |ig/L, while samples preserved with nitric acid preservative provided by 

the NWQL were free of detectable concentrations of 

zinc.

WATER-QUALITY 23
Based on these tests, it was determined that the 

vials of nitric acid preservative contained variable, but 

consistently measurable quantities of zinc and were 

responsible for the contamination of the blanks. The 

persistent and variable magnitude of contamination in 

field blanks makes the zinc concentrations in environmental samples questionable. In particular, zinc concentrations in environmental samples that were less 

than the maximum concentration found in any field 

blank (100 |ig/L) may be unreliable. Therefore, the 

minimum reporting level for zinc concentration for this 

study was revised upward from 10 (ig/L to 100 Jig/L to 

reflect the loss of resolution in the range affected by 

contamination. Zinc concentration data were not used 

to calculate zinc loads, or to make comparisons 

between sites.

Copper, sodium, potassium, and magnesium 

were sporadically found in field blank samples at concentrations slightly greater than twice the minimum 

reporting level. Each constituent was found in only one 

monthly sampling; therefore, the low concentration 

and single occurrence of each was considered to have 

no significant effect on the environmental data.

Sampling Sites and Potential Sources of Water-Quality 

Degradation

Sampling sites were selected to provide broad 

spatial coverage of streams throughout the upper Tenmile Creek watershed (table 9). Sites for localized 

characterization were also selected downstream from 

inactive mines and waste-rock piles that were potential 

sources of trace elements in water. The sites and potential sources of water-quality degradation are described 

in the next section.

Headwaters Sampling Sites

Six sampling sites in the headwaters of Tenmile 

Creek were located on Monitor Creek at mouth (site 1), 

Tenmile Creek below Monitor Creek (site 2), Tenmile 

Creek above Ruby Creek (site 3), Ruby Creek at mouth 

(site 6), Banner Creek above city diversion (site 7), and 

Banner Creek below city diversion (site 10). Most of 

this part of the basin is public land managed by the U.S. 

Forest Service, Helena National Forest. Under the current forest plan, commercial logging activity is 

restricted because the basin supplies municipal water 

for Helena. Mine wastes associated with the Monitor

Creek Tailings, the SE SE S13 Mine, the Monte Cristo 

Mine, the Peter Mine, the Woodrow Wilson Mine, the 

Peerless Jenny/King Mine, and the Queensbury Mine 

(fig. 1), are potential sources of trace elements in water 

in the headwaters area.

Sampling Sites near Rimini

Six sampling sites were located near the historic 

mining town of Rimini in the central portion of the 

upper watershed. A substantial amount of mining took 

place near Rimini at the Lee Mountain Mine, the Red 

Water Mine, the Tenmile Mine, the Red Mountain 

Mine, the Upper Valley Forge Mine, and the Valley 

Forge/Susie Mine (fig. 1).

Poison Creek (site 11), a small, perennial tributary to Tenmile Creek, originates from a spring on the 

west flank of Red Mountain. It was considered a likely 

source of trace elements to Tenmile Creek because the 

stream flows through waste rock piles at the Red 

Mountain Mine site.

Tenmile Creek above city diversion (site 12) is 

located at Rimini and is downstream from the Red 

Water and Tenmile Mine sites. Water-quality conditions at site 12 indicate the quality of water withdrawn 

from Tenmile Creek for municipal use as a drinkingwater supply for Helena. Water-quality conditions for 

Tenmile Creek below city diversion (site 13) were presumed to be identical to those for site 12. Water quality 

was sampled once from the bridge at site 13 rather than 

at site 12 because site 12, which has no bridge, could 

not be waded during high flow.

Spring Creek (site 22) is a small perennial stream 

that provides a relatively constant source of inflow to 

Tenmile Creek in the town of Rimini. Site 22 is below 

several small, unnamed mine sites. Tenmile Creek 

below Spring Creek (site 23) is in the middle of the residential area of Rimini and below discharges emanating from mine adits (entrances) at the Lee Mountain 

Mine andValley Forge/Susie Mine.

Sampling Sites in the Beaver Creek Drainage

Three sampling sites were located in the Beaver 

Creek drainage. Beaver Creek above tributary 3 (site 

15) is just below Chessman Reservoir and provides an 

indication of the quality of water released from the reservoir. Beaver Creek tributary 2 (site 18) drains the 

basin that includes the National Extension Mine site. 

Beaver Creek above city diversion (site 20) is several

24 Streamflow and Water-Quality Characteristics in the Upper Tenmile Creek Watershed, Lewis and Clark County, West-Central Montana
hundred feet upstream from the municipal diversion 

near the mouth of Beaver Creek and provides an indication of the quality of water withdrawn from Beaver 

Creek for municipal use.

Sampling Sites between Rimini and the Tenmile Water 

Treatment Plant

Six sampling sites were located between Rimini 

and the Tenmile Water Treatment Plant. Minnehaha 

Creek was sampled above the municipal diversion near 

the mouth (site 25). This site, which is downstream 

from the Beatrice, Justice, and Armstrong Mines, provides an indication of the quality of water withdrawn 

from Minnehaha Creek for municipal use.

Tenmile Creek near Rimini (site 28), the location 

of the long-term USGS streamflow-gaging station, was 

sampled to provide water-quality information for Tenmile Creek near the center of the upper Tenmile Creek 

watershed. From Rimini to site 28 just below Moose 

Creek, Tenmile Creek closely parallels the main county 

road to Rimini, a potential source of sediment runoff to 

the stream.

Moose Creek above city diversion (site 29) 

drains an area with no historical mining activity and, 

thus, probably represents background water-quality 

conditions. Moose Creek also supplies some municipal 

water for Helena.

Bear Gulch was sampled at its mouth (site 31). 

Although this tributary stream is small and flows intermittently, it drains the basin that includes the Bear 

Gulch mine site.

The sampling site Walker Creek above city 

diversion (site 32) provides an indication of the quality 

of water withdrawn from this tributary stream for 

municipal use. Walker Creek is the only sampled 

stream that drains primarily agricultural and rural residential land at lower elevations of the watershed.

The sampling site Tenmile Creek at Tenmile 

Water Treatment Plant (site 34) is the watershed outlet. 

Water-quality conditions at this site represent the 

cumulative, integrated effects of all land uses in the 

watershed.

Bottom-Sediment Sites in and near Chessman Reservoir

Five composited samples of bottom sediment 

were collected from three locations in Chessman Reservoir and one location just upstream from the reservoir 

on September 8,1997. Sites were located where variations in trace-metal concentrations might be expected 

from different reservoir inflow conditions or from reservoir dredging associated with dam rehabilitation in 

1986. Sampling locations are listed in Table 11 and 

shown in figure 1.

The sampling site Chessman Reservoir Southwest (site Rl) was located in a dredged area about 10- 

15 feet offshore near the inlet of the Banner Creek 

flume. The sampling location Chessman Reservoir 

Northeast (sites R2A and R2B) was about 10-15 feet 

offshore and outside the area dredged in 1986. The 

sampling site Wetland above Chessman Reservoir (site 

R3) was upstream from the high-water mark of the reservoir in a wetland area drained by the headwaters of 

Beaver Creek. Bottom-sediment samples at site R3 

were collected from the banks and bottom of Beaver 

Creek at a site close to streamflow-estimation site 14. 

The sampling site Chessman Reservoir Southeast (site 

R4) was located about 10-15 feet offshore and about 

40-50 feet from the confluence of Beaver Creek and the 

reservoir.

Results of Water-Quality Analyses

Diverse land uses, geology, stream basin size, 

and seasonal climatic fluctuations play a role in determining current water-quality characteristics in the 

upper Tenmile Creek watershed. Water quality generally varies from the relatively pristine water in Moose 

Creek to water having relatively high concentrations of 

trace elements downstream from mines or mine wastes. 

Table 12, at the back of the report, contains water-quality results for field-measured parameters, major ions, 

and nutrients. Table 13, at the back of the report, presents results for trace elements and suspended sediment. Quality-control data (results for replicates and 

blanks) are presented with environmental sample 

results in tables 12 and 13. The results are described in 

more detail in the following sections of the report.

Field-Measured Parameters, Major Ions, and Nutrients

Specific conductance, a field-measured parameter that generally indicates the relative abundance of 

dissolved minerals in water, ranged from 3.0 |xS/cm in 

Banner Creek below city diversion (site 10) to 231 

^iS/cm in Poison Creek (site 11). Values for pH, a fieldmeasured parameter that indicates relative acidity of 

water, ranged from 3.8 (highly acidic) in Poison Creek 

(site 11) to 8.2 (slightly basic) in Walker Creek (site 

32).

WATER-QUALITY 25
Surface water in the upper Tenmile Creek watershed generally is a calcium bicarbonate type. Hardness, as CaCC>3 ranged from 9 mg/L in Ruby Creek 

(site 6) to 82 mg/L in Bear Gulch (site 31).

Concentrations of the major ions calcium, magnesium, sodium, potassium, chloride, fluoride, and 

bicarbonate plus carbonate (alkalinity) generally were 

low throughout the upper watershed. Calcium concentrations ranged from 2.3 mg/L in Spring Creek at 

mouth (site 22) to 26 mg/L in Bear Gulch (site 31). 

Magnesium concentrations ranged from <0.1 mg/L in 

Ruby Creek (site 6) and Spring Creek (site 22) to 6.3 

mg/L in Tenmile Creek below Spring Creek (site 23). 

Sodium concentrations ranged from 0.7 mg/L in Ruby 

Creek (site 6) to 8.4 mg/L in Walker Creek (site 32). 

Potassium concentrations ranged from <0.1 mg/L in 

Ruby Creek (site 6) to 2.8 mg/L in Moose Creek (site 

29). Chloride concentrations ranged from 0.5 mg/L at 

Tenmile Creek at Tenmile Water Treatment Plant (site 

34) to 7.7 mg/L in Walker Creek (site 32), with 19 

of the 21 sites having chloride concentrations of 

<1.0 mg/L. The lowest chloride concentration was for 

a replicate sample analyzed by the NWQL; this laboratory analyzes for a lower detection limit for chloride 

than does the Montana Tunnels Laboratory. Fluoride 

concentrations ranged from <0.10 to 0.68 mg/L, with 

detectable concentrations reported from Monitor, 

Ruby, Banner, Poison, Beaver, Tenmile and Walker 

Creeks (sites 1,3,6,9,11,18,20,23,28, 32). Alkalinity, which primarily represents the combined acidneutralizing capacity of bicarbonate plus carbonate 

ions, ranged from 6 mg/L in several streams to 

71 mg/L in Moose Creek (site 29).

Concentrations of another major ion, sulfate, 

reflect the presence of oxidizing sulfide minerals associated with mined, metalliferous ore deposits. Several 

sites in the upper Tenmile Creek watershed had sulfate 

concentrations greater than 25 mg/L. Samples from 

Poison Creek (site 11) had sulfate concentrations 

between 55 and 94 mg/L, with the highest value 

occurring during low-flow conditions in August. The 

highest sulfate concentration, 99 mg/L, was for the 

August sample from Tenmile Creek below Spring 

Creek (site 23). Sulfate concentrations in Tenmile 

Creek in August decreased downstream from site 23 to 

32 mg/L at Tenmile Creek near Rimini (site 28) and 26 

mg/L at Tenmile Creek at the Tenmile Water Treatment 

Plant (site 34). Bear Gulch (site 31) had sulfate concentrations of 30 mg/L and 36 mg/L in August and 

October, respectively. Other sites in the watershed had

measurable concentrations of sulfate ranging from 2.1 

to 17 mg/L.

Concentrations of the nutrients (nitrite, nitrate, 

ammonia, total phosphorus, and dissolved orthophosphate) were very low in all samples collected in the 

upper Tenmile Creek watershed. Dissolved nitrite was 

detected in only one sample, Tenmile Creek below 

Spring Creek (site 23), at a concentration of 0.02 mg/L 

in October. Nitrate concentrations ranged from <0.01 

to 0.12 mg/L for all samples but one from Banner 

Creek tributary (site 9) that had a concentration of 0.36 

mg/L. Ammonia concentrations were less than or near 

the reporting limit of 0.05 mg/L for all samples. The 

concentration of total phosphorus ranged from <0.01 to 

0.16 mg/L, and the concentration of dissolved orthophosphate ranged from <0.01 to 0.05 mg/L.

Trace Elements

Trace-element concentrations varied widely 

throughout the upper Tenmile Creek watershed. Very 

low trace-element concentrations generally were found 

in the headwaters streams Monitor Creek (site 1), Ruby 

Creek (site 6), Banner Creek (sites 7 and 10), and in 

Tenmile Creek above city diversion (site 12). Several 

Tenmile Creek tributaries, including Moose Creek (site 

29), Bear Gulch (site 31), and Walker Cree,k (site 32), 

also had generally low concentrations of trace elements.

Trace-element concentrations were consistently 

high at sampling sites located downstream from mines 

or mine waste rock. Specifically, Poison Creek (site 

11), located below the Red Mountain Mine; Beaver 

Creek tributary 2 (site 18), located below the National 

Extension Mine; and Tenmile Creek below Spring 

Creek (site 23), located below discharges from the Valley Forge/Susie Mine adit, all had high trace-element 

concentrations. These mines and their waste rock 

appear to provide a continuous source of trace elements 

to streams in the upper Tenmile Creek watershed. Analytical results for selected trace elements are described 

in detail below. Unless stated otherwise, results are for 

total-recoverable concentrations. Spatial and seasonal 

variations in concentrations are shown graphically for 

arsenic, cadmium, copper, and lead. Concentrations of 

these trace elements exceeded aquatic life and humanhealth standards for some samples (indicated in table 

13). Concentrations of iron and manganese also 

exceeded drinking-water aesthetic standards for some 

samples. Graphs for these trace elements are not

26 Streamflow and Water-Quality Characteristics in the Upper Tenmile Creek Watershed, Lewis and Clark County, West-Central Montana
shown. For plotting purposes, concentrations of trace 

elements that were less than the analytical detection 

limits were shown as one-half the detection limits. 

Also for plotting purposes, concentrations for replicate 

samples were averaged.

Aluminum

The highest concentrations of total-recoverable 

aluminum were analyzed in samples from Poison 

Creek (site 11), ranging from 1,700 |ig/L in October to 

2,400 M-g/L in June. Large concentrations of aluminum, ranging from 310 |ig/L in October to 1,200 |Llg/L 

in August, also were found in samples from Tenmile 

below Spring Creek (site 23). Aluminum concentrations were greater during runoff conditions than during 

low-flow conditions at most sites. Natural erosion during runoff probably accounts for the greater concentrations in May and June because aluminum is common in 

soils and rocks. Because water-quality standards exist 

only for dissolved aluminum, an evaluation of exceedances is not possible for this element.

Arsenic

The spatial and seasonal variations in arsenic 

concentration for selected sites representing a diverse 

spatial distribution are depicted graphically in figure 

18. Sites shown in figure 18 are Tenmile Creek above 

Ruby Creek (site 3); Poison Creek at mouth (site 11); 

Tenmile Creek above city diversion (site 12); Beaver 

Creek tributary 2 (site 18); Beaver Creek above city 

diversion (site 20); Tenmile Creek below Spring Creek 

(site 23); Minnehaha Creek above city diversion (site 

25); Tenmile Creek near Rimini (site 28); Moose Creek 

above city diversion (site 29), and Tenmile Creek at 

Tenmile Water Treatment Plant (site 34). These sites 

are also included in figures 19-21 for other selected 

trace elements.

As shown in figure 18, concentrations of totalrecoverable arsenic were significantly greater during 

the May and June high-flow conditions than during 

low-flow conditions at Beaver Creek tributary 2 (site 

18), and, for May, Poison Creek (site 11) and Beaver 

Creek above city diversion (site 20). Greater concentrations of arsenic during high-flow conditions probably indicate that the arsenic sources are mine-waste 

sediments that are mobilized by runoff. The largest 

concentration of arsenic during runoff conditions, 180 

|lg/L, was in the May sample from Poison Creek.

Arsenic concentrations were significantly larger 

during low-flow conditions than during runoff conditions at several sites. Most notably, large concentrations of arsenic were found in August and October at 

Tenmile Creek below Spring Creek (site 23) (170 and 

63 ^ig/L, respectively). The large arsenic concentrations at this site presumably resulted from inputs below 

the city diversion at Rimini (site 12), because concentrations were not elevated at site 12. The effect of those 

arsenic inputs persisted downstream in Tenmile Creek 

where concentrations, although progressively diluted, 

remained relatively large in both August and October at 

Tenmile Creek near Rimini (site 28) (30 and 27 |ig/L, 

respectively), and at Tenmile Creek at the Tenmile 

Water Treatment Plant (site 34) (19 and 19 p,g/L, 

respectively). The sources of arsenic for these large 

measured concentrations probably are discharges from 

the adits at Lee Mountain andValley Forge/Susie 

Mines in Rimini. Because the mine-adit discharges are 

relatively constant year-round, concentrations of 

arsenic in Tenmile Creek presumably increase as 

streamflow, and hence dilution, decreases.

Cadmium

The spatial and seasonal variation in cadmium 

concentration for selected sites is depicted graphically 

in figure 19. As indicated in figure 19, Poison Creek 

(site 11) had uniformly high concentrations of totalrecoverable cadmium, ranging from 25 to 30 [ig/L for 

the four samples. Tenmile Creek below Spring Creek 

(site 23) had concentrations of total-recoverable cadmium ranging from 1.0 |Hg/L in May to 30 (ig/L in 

August. As was the case for arsenic, the large cadmium 

concentration in August represents the limited flow 

available in Tenmile Creek to dilute the relatively constant discharge from the mine adits. Beaver Creek tributary 2 (site 18) had a total-recoverable cadmium 

concentration of 6 (ig/L in June, probably representing 

runoff-associated transport of mine wastes. Totalrecoverable cadmium values for all other sites ranged 

from <0.1 |ig/L, the detection limit, to 2.8 |ig/L during 

the study period.

Copper

The spatial and seasonal variation in copper concentration for selected sites is shown graphically in figure 20. Figure 20 shows that copper concentrations 

were consistently high in Poison Creek (site 11) during 

both runoff and low-flow conditions. Concentrations

WATER-QUALITY 27
200

Figure 18. Total-recoverable arsenic concentrations in 1997 for selected sites in the upper Tenmile Creek watershed near Rimini, 

Montana.

were variably elevated in Tenmile Creek below Spring 

Creek (site 23) in May and October, and in Beaver 

Creek above city diversion (site 20) in October. Copper concentrations were less variable and generally low 

in Tenmile Creek above Ruby Creek (site 3) and above 

city diversion (site 12), Minnehaha Creek, and Moose 

Creek (site 29).

Consistently high copper concentrations, presumably associated with mine wastes, were found in 

Poison Creek (site 11), where concentrations ranged

from 240 to 420 Lig/L. Total-recoverable concentrations at Tenmile below Spring Creek (site 23) were seasonally variable and ranged from 11 to 200 p,g/L. The 

elevated concentration of copper in Tenmile Creek 

below Spring Creek in August probably was not the 

result of tributary inflow from Beaver Creek because 

all flow in Beaver Creek was diverted for municipal 

use, but rather from inputs downstream from Beaver 

Creek. High concentrations of copper at Tenmile 

Creek below Spring Creek (site 23) also resulted in ele28 Streamflow and Water-Quality Characteristics in the Upper Tenmile Creek Watershed, Lewis and Clark County, West-Central Montana
Figure 19. Total-recoverable cadmium concentrations in 1997 for selected sites in the upper Tenmile Creek watershed near Rimini, 

Montana.

vated mainstem concentrations downstream as far as 

the Tenmile Water Treatment Plant. Concentrations of 

total-recoverable copper ranged from 17 to 88 JJ.g/L at 

Tenmile Creek near Rimini (site 28) and from 8 to 51 

|j,g/L at Tenmile Creek at the Tenmile Water Treatment 

Plant (site 34). Relatively large total-recoverable copper concentrations at Beaver Creek tributary 2 (site 18) 

in May and June (53 and 49 |J.g/L, respectively) are 

likely related to runoff from mine waste areas.

High total-recoverable copper concentrations, 

ranging from 150 Lig/L in August to 430 Lig/L in October, also were found in Beaver Creek above tributary 3 

(site 15, not plotted). As previously described, these 

high concentrations may be the result of the annual 

summer application of copper sulfate to Chessman 

Reservoir for algae-control purposes. Total-recoverable copper concentration in Beaver Creek above city 

diversion (site 20) also was high in October (240 (J-g/L).

FIGURE 19 29
450

Figure 20. Total-recoverable copper concentrations in 1997 for selected sites in the upper Tenmile Creek watershed near Rimini, 

Montana.

This high value is attributable to water releases from 

Chessman Reservoir and not Beaver Creek tributary 2 

(site 18), which had a total-recoverable copper concentration of only 6 (J-g/L in October.

Iron

Iron concentrations varied dramatically from 

high-flow to low-flow conditions. During spring runoff in May, concentrations were highest in samples 

from Poison Creek (site 11), 1,600 (ig/L, and Banner

Creek below city diversion (site 10), 1,100 (J,g/L. The 

next largest iron concentration during May was 680 

|j.g/L for Bear Gulch at mouth (site 31). During lowflow conditions in August, large iron concentrations 

were found in samples from Beaver Creek above tributary 3 (site 15; 3,100 |ig/L), Tenmile Creek below 

Spring Creek (site 23; 3,800 V-g/L), and Walker Creek 

above city diversion (site 32; 1,500 |J.g/L). At these 

same sites, iron concentrations in October were 730 

Hg/L, 1,300 ng/L, and 1,800 pig/L, respectively.

30 Streamflow and Water-Quality Characteristics in the Upper Tenmile Creek Watershed, Lewis and Clark County, West-Central Montana
Spatial and seasonal variations in lead concentration for selected sites are shown graphically in figure 

21. As shown in figure 21, total-recoverable lead concentrations generally were highest in Poison Creek 

(site 11), ranging from 52 Lig/L in June to 140 |o,g/L in 

May. Beaver Creek tributary 2 (site 18) had concentrations which ranged from the detection limit (<3 M-g/L) 

in October to 33 Lig/L in May. Tenmile Creek below

Spring Creek (site 23) had high total-recoverable lead 

concentrations ranging from 8 Lig/L in October to 71 

|a,g/L in June. The high concentration in June may be 

anomalous because it is substantially greater than any 

other measured value at this site, and substantially 

greater than the June value at the next downstream 

mainstem site on Tenmile Creek (site 28). Although 

concentration of lead might be expected to decrease in 

the downstream direction if intervening tributary flows 

are sufficient to provide a dilution, streamfiow in June

160

Figure 21. Total-recoverable lead concentrations in 1997 for selected sites in the upper Tenmile Creek watershed near Rimini, Montana.

WATER-QUALITY 31
was similar at sites 23 and 28. Downstream, totalrecoverable lead concentrations in October were 6 

|Hg/L at Tenmile Creek near Rimini (site 28) and 3 

jig/L in Tenmile Creek at the Tenmile Water Treatment 

Plant (site 34). Total-recoverable lead concentrations 

in May at these sites were 13 |ig/L and 12 |ig/L, respectively. Lead concentrations generally were close to or 

at the detection limit for most other sampling sites.

Manganese

Manganese concentrations generally were high 

at sampling sites associated with mine wastes. The 

highest concentrations, ranging from 1,500 to 1,800 

fig/L, were found in samples from Poison Creek (site 

11). Tenmile Creek below Spring Creek (site 23) had a 

large manganese concentration of 1,100 |ig/L in 

August. Beaver Creek above tributary 3 (site 15) also 

had a large concentration of manganese (370 Jig/L) in 

the August sample. All other sites had concentrations 

of 280 |ig/L or less during the study.

Chromium, Mercury, Nickel, Selenium, and Silver

Minnehaha Creek above city diversion (site 25) 

was the only site having a detectable level of chromium 

(1.0 (Xg/L). Only one sample, perhaps an anomaly, had 

a mercury concentration (5.8 |ig/L) above the detection 

limit. No samples had detectable levels of nickel. One 

sample from Poison Creek (site 11) had a detectable 

selenium concentration of 3 |ig/L and one sample each 

from Tenmile Creek below Spring Creek (site 23) and 

Tenmile Creek near Rimini (site 28) had a detectable 

selenium concentration of 1.0 (ig/L. One sample from 

Walker Creek above city diversion (site 32) had a 

detectable concentration of silver of 10 |J-g/L.

Zinc

As previously described, site to site comparisons 

of zinc concentrations cannot be made because of zinc 

contamination of the sample preservative. Nevertheless, results in table 13 indicate that all samples from 

Poison Creek (site 11) had total-recoverable zinc concentrations greatly in excess of the revised minimum 

reporting level of 100 (ig/L with a high of 3,700 |ig/L 

(site 18). In addition, total-recoverable zinc concentrations in all samples from Tenmile Creek above and 

below city diversion (sites 12 and 13), Beaver Creek 

tributary 2 (site 18), Spring Creek (site 22), Tenmile

Creek below Spring Creek (site 23), Minnehaha Creek 

above city diversion (site 25), Tenmile Creek near 

Rimini (site 28), and Tenmile Creek at the Tenmile 

Water Treatment Plant (site 34) were greater than 100 

[Lg/L.

Suspended Sediment

Erosion of streambanks or unvegetated and disturbed areas, such as roads and mined areas, potentially 

can be a major source of suspended sediment in 

streams of the upper Tenmile Creek watershed. In 

addition, erosion of natural soils that consist of glacial 

tills and erosive granitic material and high-flow scour 

of streambed sediment deposits contribute to the suspended-sediment load in streams in the upper Tenmile 

Creek watershed. Factors influencing erosion of material into streams include cohesiveness of geologic parent materials, steepness of terrain, and proximity of 

sediments to streams (Hettinger, 1996).

Suspended-sediment concentrations generally 

were greatest in May during the early phases of spring 

runoff. Concentrations in May ranged from 6 mg/L in 

the sample from Beaver Creek above city diversion 

(site 20) to 150 mg/L in the sample from Poison Creek 

(site 11). The concentration of suspended sediment in 

Tenmile Creek was similar at all five mainstem sites 

(3,13,23,28,34) in the May sampling (range of 20-34 

mg/L). The small differences in suspended-sediment 

concentrations in May between sites on Tenmile Creek 

indicates that sediment contributions from tributaries 

are minor.

Runoff samples collected in June from sites on 

Tenmile Creek were low and showed little variability in 

suspended-sediment concentration, with values ranging from 6 mg/L to 9 mg/L. The highest suspendedsediment concentration in any June sample was 18 

mg/L from Bear Gulch at mouth (site 31).

Suspended-sediment concentrations during lowflow conditions generally were low. Suspended-sediment concentrations in samples from Tenmile Creek 

ranged from 2 mg/L to 12 mg/L. The largest concentration (56 mg/L) was measured in the October sample 

from Moose Creek (site 29). This value may be anomalous because it is significantly larger than from any 

other sample from Moose Creek. The next largest suspended-sediment concentration during low-flow conditions was 21 mg/L from the October sample from 

Walker Creek (site 32).

32 Streamflow and Water-Quality Characteristics in the Upper Tenmile Creek Watershed, Lewis and Clark County, West-Central Montana
Bottom Sediment

Results of analyses of concentrations of trace 

elements in bottom sediment collected from Chessman 

Reservoir are shown in table 14.

The bottom-sediment sample from the wetland 

above Chessman Reservoir (site R3) had the highest 

concentrations of arsenic, cadmium, chromium, lead 

and zinc. This wetland receives runoff from the headwaters of Beaver Creek. Wetland soils are known for 

their ability to remove trace elements from surface 

water by adsorption, and constructed wetlands have 

been used extensively in the cleanup of mine-adit discharge (Klusman and Machemer, 1991).

The highest copper concentrations in bottomsediment samples were from the undredged portion of 

the reservoir at Chessman Reservoir Northeast (sites 

R2A and R2B). The surficial sediment sample taken 

from 0-7 in. (site R2A) had a copper concentration of 

264 fig/L, whereas the deeper sample taken from 7-9 

in. (site R2B) had a copper concentration of 617 |ig/L. 

The larger concentration at greater sediment depth may 

reflect either a downward migration and accumulation 

of copper as a result of geochemical mobility, or it may 

represent a historical profile of greater copper applications in earlier years.

Sources for trace elements detected in the wetland and for trace elements other than copper in the reservoir are most likely eroded sediments from areas of 

naturally high mineralization. The transport of mine 

wastes may contribute some trace elements, particularly at Chessman Reservoir Southwest (site Rl). This 

site is near the Banner Creek flume outfall. The Banner 

Creek flume passes through mine-waste rock piles at 

the Red Mountain Mine and downstream from the 

National Extension Mine. However, concentrations of 

trace elements at site Rl are not significantly larger 

than those at the other reservoir sites.

A comparison of trace-element concentrations in 

bottom sediment in Chessman Reservoir with concentrations in bottom sediment in Lake Helena (Kendy and 

others, 1998) is provided in table 14. Lake Helena is 

located just downstream from the mouth of Tenmile 

Creek, northeast of Helena. With the exception of 

chromium, trace-element concentrations in Chessman 

Reservoir and adjacent wetland bottom sediment generally equal or exceed the concentrations detected in 

Lake Helena sediments. Kendy and others (1998) also 

found that concentrations of arsenic, chromium, copper, lead, and zinc in bottom sediments in Lake Helena

were comparable to concentrations in bottom sediments in seven mining-impaired wetlands and significantly greater than concentrations in 73 unimpaired 

wetlands throughout Montana. Kendy and others 

(1998) also report arsenic, copper, lead, and zinc concentrations in Lake Helena bottom sediment greatly 

exceed mean values and are near the upper end of 

ranges reported for more than 700 soil samples from 

the western United States. These comparisons indicate 

that trace elements from mining areas and areas of naturally high mineralization may accumulate in reservoir 

and wetland bottom sediments.

Exceedances of Water-Quality Standards

As previously described, concentrations of many 

inorganic constituents in several streams in the upper 

Tenmile Creek watershed were higher than those found 

in the relatively pristine headwaters streams or in 

Moose Creek. The relative degree of the amount of 

contamination in a stream can be assessed by comparing measured constituent concentrations with waterquality standards established for human health and 

aquatic life.

Water-quality standards for inorganic constituents (table 10) have been developed by the U.S. Environmental Protection Agency (EPA) and adopted by 

the State of Montana for the purpose of protecting life 

(Montana Department of Environmental Quality, 

1995). These standards generally are different for 

human health and aquatic life. The water-quality standards discussed hereafter are those pertaining to trace 

elements, the constituents associated with past mining 

activities and of most concern in the upper Tenmile 

Creek watershed.

Published water-quality standards for trace elements are for the total-recoverable phase rather than the 

dissolved phase, unless otherwise noted. However, all 

water-quality samples that had total-recoverable or dissolved concentrations greater than the standards are 

noted in this report. This comparison of dissolved constituents to the standards is provided for general reference because of some uncertainty in the scientific 

community as to the predominant form of metal that 

may cause biological impairment.

WATER-QUALITY 33
Human Health

Montana has adopted water-quality standards for 

chemical constituents that pose a risk to human health. 

In addition, two constituents, iron and manganese, have 

standards for aesthetic purposes such as taste, odor, and 

staining (Montana Department of Environmental Quality, 1995). Concentrations of three trace elements in 

the water-quality samples collected in the watershed 

exceeded human-health standards established for 

arsenic, cadmium, and lead. Although iron and manganese concentrations also exceeded human-health standards, these trace elements are not discussed because 

they pose no risk to health.

The current human-health standard in Montana 

for arsenic is 18 jig/L. This standard was exceeded 

during runoff in May at Poison Creek (site 11), and 

Beaver Creek tributary 2 (site 18) in May and June. 

During low flows in August and October, the arsenic 

standard was exceeded at Tenmile Creek below Spring 

Creek (site 23), Tenmile Creek near Rimini (site 28), 

and Tenmile Creek at Tenmile Water Treatment Plant 

(site 34). Arsenic concentration also slightly exceeded 

the standard in August at Beaver Creek above tributary 

3 (site 15). Arsenic concentrations were less than the 

human-health standard at all sites just above the city 

diversions to the water treatment plant (Banner Creek, 

Tenmile Creek, Beaver Creek, Minnehaha Creek, 

Moose Creek, and Walker Creek; sites 7,12,20,25,29, 

and 32). Arsenic is classified as a known human carcinogen, and chronic exposure is associated with symptoms such as pain, nausea, vomiting, and diarrhea (U.S. 

Department of Health and Human Services, 1993a).

The current human-health standard in Montana 

for cadmium is 5 |ig/L. The standard was exceeded in 

all samples collected from Poison Creek (site 11), Beaver Creek tributary 2 (site 18) in June, and Tenmile 

below Spring Creek (site 23) in August. The humanhealth standard for cadmium was not exceeded at any 

of the five sites just above the city diversions. Cadmium is a probable human carcinogen and cumulative 

toxin. The primary exposure for humans is cadmium 

dust on hands and cadmium uptake in garden vegetables. Ingestion of high cadmium levels irritates the 

stomach (U.S. Department of Health and Human Services, 1993b).

The current human-health standard in Montana 

for lead is 15 |ig/L. This standard was exceeded in all 

samples from Poison Creek (site 11), the May sample 

from Beaver Creek tributary 2 (site 18), and samples

from Tenmile Creek below Spring Creek (site 23) in 

May, June, and August. The lead concentration in the 

May sample from Tenmile Creek collected below the 

city diversion (site 13) equaled the standard. The lead 

concentration at this site is presumed to be the same as 

the site above city diversion. Lead concentrations 

were less than the human-health standard for all samples from the five other sites just above the city diversions (sites 7,20,25,29, and 32). High concentrations 

of lead have been shown to affect virtually every 

human organ. The most sensitive organs are the brain 

and kidneys. Low-level lead exposure may cause 

increased blood pressure, anemia and loss of memory 

in adults, and can impact the physical and mental 

development of children. The EPA considers lead 

compounds to be a possible human carcinogen (U.S. 

Department of Health and Human Services, 1993c). In 

the early part of this century, lead mining in the upper 

Tenmile Creek watershed was prohibited to protect the 

Helena water supply.

Aquatic Life

Different standards were developed for protection of aquatic-life from acute and chronic toxicity 

resulting from exposure to trace elements. Although 

most trace elements have both an acute and chronic 

standard, iron has only a chronic standard, and silver 

has only an acute standard. The acute standard indicates the maximum concentration that aquatic life generally can withstand for short periods (U.S. Environmental Protection Agency, 1986). The chronic standard is a lower concentration that, when exceeded over 

a long period, may result in suppression or impairment 

of normal biological functions (U.S. Environmental 

Protection Agency, 1986). Impairments can result in 

reduced growth rates or breeding activity. Fish, particularly trout, are the species considered most vulnerable 

to high concentrations of trace elements in the streams 

in the upper Tenmile Creek watershed.

The aquatic-life standards for cadmium, copper, 

lead, nickel, silver, and zinc are hardness-dependent. 

Equations for calculating the aquatic-life standard 

using measured hardness (CaCO3 concentration) at the 

time of sampling are presented in table 15. The equations in table 15 were used to calculate acute and 

chronic aquatic-life standards for cadmium, copper, 

lead, nickel, and silver for each water-quality sample. 

The measured concentrations of cadmium, copper, 

lead, nickel, and silver in individual samples then were

34 Streamflow and Water-Quality Characteristics in the Upper Tenmile Creek Watershed, Lewis and Clark County, West-Central Montana
compared to the calculated standards to identify which 

samples had exceeded the standards.

Sample concentrations that exceeded the humanhealth standard are shaded in table 13 at the back of the 

report. Concentrations that exceeded the acute and 

chronic aquatic-life standards are highlighted in italicized bold and bold type, respectively, in table 13.

Results in table 13 indicate that acute and 

chronic aquatic-life standards for cadmium, copper, 

lead, and zinc in both the dissolved and total-recoverable phases were exceeded for many samples. Many 

samples also exceeded acute and chronic standards for 

dissolved aluminum, although only concentrations of 

total-recoverable aluminum were analyzed. The 

chronic standard for iron was exceeded for several 

samples from several streams. The acute standard for 

silver was exceeded one time at Walker Creek above 

city diversion (site 32), and the acute and chronic standards for mercury were exceeded one time at Banner 

Creek above city diversion (site 7).

Constituent Transport in Streams

The downstream transport of a constituent is 

commonly expressed as a mass of constituent (load) 

transported past a measuring location in a given period 

of time. Calculation of constituent load transport is a 

useful way to compare the relative contribution of constituent mass from streams having widely varying concentrations and flows. This allows identification of 

important sources introducing large quantities of a constituent that can substantially affect downstream water 

quality. For example, a tributary having a very high 

concentration of a constituent, but a very small discharge, will have little effect on a receiving stream that 

has a sufficiently large discharge to dilute the incoming 

constituent concentration. Conversely, a tributary having a very high concentration of a constituent may significantly increase the constituent concentration in the 

receiving stream if the discharge in the tributary is relatively large.

Instantaneous loads were calculated for selected 

total-recoverable trace-elements and suspended sediment for sampling sites in the upper Tenmile Creek 

watershed. Loads were compared among sites to indicate where the greatest inputs occurred during the prevailing hydrologic conditions at the time of sampling. 

Trace-element loads were calculated using concentrations analyzed in environmental samples and discharge

measured at the time of sampling using the following 

equation:

Lr = 0.0054 (Q)(C) (2)

where

LT is the trace element load, in pounds,

per day;

0.0054 is a units conversion factor; 

Q is stream discharge, in cubic feet per

second; and 

C is the trace-element concentration, in

micrograms per liter.

Suspended-sediment loads were calculated using the 

following equation:

LS = 5.4(Q)(C) (3)

where

Ls is the suspended-sediment load, in 

pounds, per day;

5.4 is a units conversion factor;

Q is the stream discharge, in cubic feet 

per second; and

C is the suspended-sediment concentration, in milligrams per liter.

Table 16 presents calculated instantaneous loads 

for selected trace elements and suspended sediment on 

individual sampling dates. Figures 22 through 25 

depict the seasonal variations of chemical loads 

observed during May through October 1997 for 

arsenic, cadmium, copper, and lead. Values in table 16 

with less-than symbols represent calculated loads 

based on the analytical detection limits for concentration of those constituents. For plotting purposes, calculated loads with less-than symbols were divided by two 

to indicate that loads were less than those shown in 

table 16. As indicated in table 16 and figures 22 

through 25, the impacts on downstream water quality 

from high concentrations of trace elements in small 

streams like Poison Creek are significant, but not as 

great as the constituent concentrations might indicate.

Table 16 and figure 22 indicate that arsenic loads 

in Tenmile Creek generally increased in the downstream direction during runoff in May and June and 

generally remained about the same or increased 

slightly during low-flow periods in August and October. The large increased arsenic loads in May at successive downstream locations evidently were from

WATER-QUALITY 35
18

ai

D.

14

cc 10

UJ

O

UJ I'

§ 6

O

ai

I

o

z

UJ 

CO

cc

cf

/

/

f

/

cf /

Figure 22. Instantaneous total-recoverable arsenic loads in 1997 for selected sites in the upperlenmile Creek watershed near Rimini, 

Montana.

unsampled tributaries such as Moore's Spring Creek, 

runoff from diffuse sources, or from resuspension of 

fine materials in the mainstem itself, because sampled 

tributary inputs, except from Poison Creek (site 11), 

were relatively small. Arsenic loads from the early 

runoff in May were substantially greater then loads 

from the later runoff in June and many times greater 

than loads from the low-flow periods in August and 

October. Arsenic load in Tenmile Creek decreased in

October from below Spring Creek (site 23) to the gage 

site near Rimini (site 28), but the decrease was relatively small and probably not significant.

As shown in figure 23, cadmium loads in Tenmile Creek also generally increased in the downstream 

direction during runoff in May and June and remained 

about the same from above the city diversion (site 12) 

to the Tenmile Water Treatment Plant (site 34) during 

the low-flow periods in August and October. Tributary

36 Streamflow and Water-Quality Characteristics in the Upper Tenmile Creek Watershed, Lewis and Clark County, West-Central Montana
Figure 23. Instantaneous total-recoverable cadmium loads in 1997 for selected sites in the upper Tenmile Creek watershed near Rimini, 

Montana.

inputs of cadmium from Poison Creek (site 11) and 

Minnehaha Creek (site 25) were significant in May and 

June. As was the case with arsenic, cadmium loads in 

Tenmile Creek were significantly greater during the 

early runoff in May than during the later runoff in June, 

and loads during the low-flow periods in August and 

October were much less than during the runoff period. 

Cadmium load in Tenmile Creek decreased slightly in 

May from above the city diversion (site 12) to below

Spring Creek (site 23). Cadmium load in Tenmile 

Creek also decreased slightly in October from below 

Spring Creek to the gage site near Rimini (site 28) and 

from the gage site near Rimini to the Tenmile Water 

Treatment Plant (site 34). All decreases were relatively 

small and probably not significant.

Figure 24 shows that copper loads in Tenmile 

Creek also generally increased in the downstream 

direction during runoff conditions in May. Copper load

FIGURE 23 37
120

Figure 24. Instantaneous total-recoverable copper loads in 1997 for selected sites in the upperTenmile Creek watershed near Rimini, 

Montana.

in May was particularly high at Tenmile Creek below 

Spring Creek (site 23). The high May value at this site 

may be somewhat anomalous, however, given that it 

was twice as large as any other calculated value for 

May. Significant copper load was input to Tenmile 

Creek in May from all tributaries except Moose Creek 

(site 29). Copper loads in Tenmile Creek were substantially smaller in June than in May at most sites. Copper 

loads were relatively small at all sites in August and at

sites upstream from Beaver Creek (site 20) in October. 

Beaver Creek had a relatively large copper load in 

October, presumably the result of copper-laden flow 

releases from Chessman Reservoir, and copper loads 

were elevated at all mainstem sites downstream from 

Beaver Creek (sites 23, 28, and 34).

As shown in figure 25, all sites had their largest 

lead loads in May, except for Tenmile Creek below 

Spring Creek (site 23), which had a large load in June.

38 Streamflow and Water-Quality Characteristics in the Upper Tenmile Creek Watershed, Lewis and Clark County, West-Central Montana
40

1

a.

CO

a

030

2

25

g 20

UJ 

Of

(5 15

CO

OHI

I

I

10

* 5

| May 

 June

Q August 

D October

«^

.^>

V jt V

* 

cf

Figure 25. Instantaneous total-recoverable lead loads in 1997 for selected sites in the upper Tenmile Creek watershed near Rimini, 

Montana.

Except for the notably large and perhaps anomalous 

June value, lead loads did not increase appreciably 

downstream from Tenmile Creek above city diversion 

(site 12). Thus, lead inputs from tributaries were relatively minor for all months.

SUMMARY

Tenmile Creek is a small mountain stream in 

Lewis and Clark County, Montana. Upper Tenmile 

Creek provides most of the drinking water for the City

of Helena and also has been the focus of numerous 

small hard-rock mining operations since 1864. 

Because of the municipal water demands, portions of 

the stream are dewatered every year. In addition, contaminated drainage from inactive mines periodically 

enters the stream. Because of these impacts on water 

quantity and quality, the Upper Tenmile Watershed 

Steering Group was formed and initiated a cooperative 

hydrologic investigation of the Upper Tenmile Creek 

watershed by the Montana Department of Natural

SUMMARY 39
Resources and Conservation, Lewis and Clark County, 

and the USGS.

In May 1997, the USGS installed 32 streamstage gages throughout the upper Tenmile Creek watershed. In addition, one continuous-record streamflowgaging station was established, and one discontinued, 

long-term continuous-record streamflow-gaging station (Tenmile Creek near Rimini, station 06062500) 

was re-established. Nineteen of these 34 data-collection sites subsequently were used for the estimation of 

long-term monthly natural Streamflow, and 21 were 

used for the collection of water-quality information. 

Nineteen sites were intended for possible use to estimate daily natural discharge for Tenmile Creek near 

Rimini, but most ultimately were used only for verification purposes.

To estimate long-term monthly natural flows at 

locations throughout the upper basin, a multi-step correlation procedure was used.

Step 1: Historical metered and observed wateruse data for the Tenmile Water Treatment Plant for 

water years 1991-98 and October 1998 (first month of 

water year 1999) and measured discharge data from 

May through October 1997 for the current study were 

used to estimate long-term monthly natural flows for 

1961-90 for Tenmile Creek near Rimini.

Step 2: Metered and observed water-use data for 

the Tenmile Water Treatment Plant and measured discharge for the current study were used to estimate daily 

natural flows during May through October 1997 for 

Tenmile Creek near Rimini.

Step 3: Measured and observed discharges during May through September 1997 at 19 monthly 

flow-estimation sites were regressed with concurrent 

estimated daily natural discharges for Tenmile Creek 

near Rimini. The regression relation then was used to 

estimate long-term monthly natural flows at each of the 

19 sites from the long-term monthly natural flows for 

Tenmile Creek near Rimini.

To test the reliability of the regression equations, 

a test using a nearby, long-term streamflow-gaging station was used. The station, Prickly Pear Creek near 

Clancy, was considered to be an estimation site, and the 

logarithms of 20 randomly selected daily mean discharges from May through October 1997 were 

regressed against logarithms of concurrent daily natural discharges for Tenmile Creek near Rimini. The 

resultant regression equation was used to calculate 

long-term mean monthly discharge for Prickly Pear 

Creek, and the calculated values were compared to

actual, recorded values of mean monthly discharge. 

Estimation errors ranged from -6.6 percent in February 

to 14.2 percent in August. Based on the test results, 

estimation errors for most sites in the upper Tenmile 

Creek watershed are believed to be about the same or 

slightly larger than those for the test.

Two series of gain-loss discharge measurements 

were conducted in September 1998 and July 1999 to 

help determine whether Tenmile Creek gains flow from 

or loses flow to ground water between the city diversion in Rimini and the Tenmile Water Treatment Plant. 

Both series of measurements indicated that gains in 

flow occur between the city diversion and the mouth of 

Walker" Creek and that losses in flow occur from the 

mouth of Walker Creek to the treatment plant. These 

results indicate that Streamflow gains in the upper part 

of the watershed generally offset losses in the lower 

part.

Stream water from 21 sites in the upper Tenmile 

Creek watershed was sampled and analyzed for various 

chemical constituents over a wide range of flows. 

Sampling sites included locations near the mouths of 

major Tenmile Creek tributaries and key locations on 

Beaver Creek and Tenmile Creek. Most sites were 

sampled in May, June, August, and October, although 

some sites were sampled fewer than four times because 

of access problems or lack of flow. Samples were analyzed for concentrations of major ions, nutrients, trace 

elements, and suspended sediment.

Because of the application of copper sulfate to 

water in Chessman Reservoir to retard algae growth, 

five samples of bottom sediment in the reservoir and an 

adjacent wetland were collected September 8, 1997 

from four selected locations. The bottom sediment 

samples were analyzed for concentrations of arsenic, 

cadmium, chromium, copper, lead, and zinc.

Water and sediment samples were collected in 

accordance with USGS standard methods. Water samples were analyzed by Montana Tunnels, Inc. Suspended-sediment samples were analyzed by the USGS 

sediment laboratory in Helena, Montana, and reservoir 

bed-sediment samples were analyzed by the NWQL.

Quality-assurance data included field-blank 

samples of deionized water and replicate environmental samples incorporated into routine sample sets submitted to the laboratory. Quality-control samples 

comprised about 10 percent of the total number of 

water samples and consisted of two deionized water 

blanks and two replicates per sampling trip.

40 Streamflow and Water-Quality Characteristics in the Upper Tenmile Creek Watershed, Lewis and Clark County, West-Central Montana
Zinc contamination of field blanks was large and 

persistent. Based on a test of five blank samples in 

October 1997, it was determined that vials of nitric acid 

preservative from the routine supplier used during the 

study had consistently measurable concentrations of 

zinc. Thus, zinc concentrations in any environmental 

sample less than the maximum concentration found in 

any field blank (100 |J,g/L) may be unreliable.

Surface water in the upper Tenmile Creek watershed generally is a calcium bicarbonate type. Hardness 

ranged from 9 mg/L to 82 mg/L. Sulfate concentrations tended to be largest in areas associated with mining activity. The largest sulfate concentration in any 

sample was 99 mg/L for the August sample from Tenmile Creek below Spring Creek, at Rimini. Nutrient 

concentrations were very low in all samples collected.

Trace-element concentrations varied widely 

throughout the upper Tenmile Creek watershed. Very 

low concentrations generally were found in the headwater streams Monitor Creek, Ruby Creek, Banner 

Creek, and Tenmile Creek above city diversion and in 

the tributary streams Moose Creek, Bear Gulch, and 

Walker Creek. Consistently high concentrations of 

trace elements were found in samples from Poison 

Creek, Beaver Creek tributary 2, and Tenmile Creek 

below Spring Creek-all sites downstream from mines 

or mine waste rock. Samples from Poison Creek had 

the highest concentrations of aluminum (2,400 |ig/L), 

arsenic (180 |ig/L), cadmium (30 |ig/L), lead 

(140 |ig/L), manganese (1,800 jig/L), and zinc (3,700 

)ig/L) found in the study. The highest concentration of 

copper attributable to mining activity also was found in 

Poison Creek (420 fig/L). The highest concentration of 

copper, which is probably attributable to copper sulfate 

addition to Chessman Reservoir, was found in Beaver 

Creek above tributary 3 (430 |ig/L). The highest concentration of cadmium (30 Hg/L) was found in samples 

from Poison Creek and Tenmile Creek below Spring 

Creek and the highest concentration of iron (3,800 

jig/L) was found in samples from Tenmile Creek below 

Spring Creek.

Suspended-sediment concentrations generally 

were greatest in May during spring runoff. Concentrations in May ranged from 6 mg/L in Beaver Creek 

above city diversion to 150 mg/L in Poison Creek. 

Concentrations of suspended sediment in May did not 

vary significantly in Tenmile Creek (20 mg/L to 34 

mg/L). Suspended-sediment concentrations generally 

were low during low-flow conditions, ranging from 2 

mg/L to 21 mg/L.

Copper concentrations in bottom sediment from 

Chessman Reservoir were greater than concentrations 

found in bed sediment from Lake Helena. Concentrations of other trace elements in bed sediment from 

Chessman Reservoir were about the same as those 

found in bed sediment from Lake Helena, except for 

chromium. The concentration of chromium was less in 

bed sediment from Chessman Reservoir than in bed 

sediment from Lake Helena.

Water-quality standards for chemical constituents that pose a risk to human health were exceeded for 

arsenic, cadmium, and lead. The human-health standard for arsenic, 18 (ig/L, was exceeded in May at Poison Creek, in May and June at Beaver Creek tributary 

2, and in August and October at Tenmile Creek below 

Spring Creek, Tenmile Creek near Rimini, and Tenmile 

Creek at Tenmile Water Treatment Plant. Arsenic concentrations were less than the human-health standard at 

all sites just above the city diversions. The humanhealth standard for cadmium, 5 |ig/L, was exceeded in 

all samples from Poison Creek, Beaver Creek tributary 

2 in June, and Tenmile Creek below Spring Creek in 

August. Cadmium concentrations were less than the 

human-health standard at all sites just above the city 

diversions. Concentrations of lead were greater than 

the human-health standard (15 |ig/L) in all samples 

from Poison Creek, the May sample from Beaver Creek 

tributary 2, and samples from Tenmile Creek below 

Spring Creek in May, June, and August. The May sample from Tenmile Creek below the city diversion, 

which is presumed equivalent to a sample from above 

the city diversion, had a lead concentration equal to the 

human-health standard. No samples from five other 

sites just above city diversions had lead concentrations 

that exceeded human-health standards.

Acute and chronic aquatic-life standards for cadmium, copper, and lead were exceeded for many samples throughout the watershed. The chronic standard 

for iron was exceeded for several samples from several 

streams.

Constituent loads were calculated for selected 

trace elements and suspended sediment. Loads varied 

seasonally, with the largest values occurring during 

high-flow conditions in May and June. Due to lower 

streamflow, loads in Poison Creek, the most highly 

contaminated stream in the watershed in terms of traceelement concentrations, generally were not as large as 

loads in several other tributaries and in the Tenmile 

Creek mainstem.

SUMMARY 41
SELECTED REFERENCES

Edwards, T.K., and Glysson, G.D., 1988, Field methods for 

measurement of fluvial sediment: U.S. Geological 

Survey Techniques of Water-Resources Investigations, 

book 3, chap. C2, 80 p.

Guy, H.P., and Norman, V.W., 1970, Field methods for 

measurement of fluvial sediment: U.S. Geological 

Survey Techniques of Water-Resources Investigations, 

book 3, chapter C2, 59 p.

Hettinger, P.S., 1996, Integrating social assessment and 

biophysical characterization for watershed protection 

of upper Tenmile Creek near Helena, Montana: 

Missoula, Mont., University of Montana, M.S. thesis, 

170 p.

Horowitz, A.J., Demas, C.R., Fitzgerald, K.K., Miller, T.L., 

and Rickert, D.A., 1994, U.S. Geological Survey 

protocol for the collection and processing of surfacewater samples for the subsequent determination of 

inorganic constituents in filtered water: U.S. 

Geological Survey Open-File Report 94-539, 57 p.

Kendy, Eloise, Olsen, Bill, and Malloy, J.C., 1998, Field 

screening of water quality, bottom sediment, and biota 

associated with irrigation drainage in the Helena Valley, 

west-central Montana, 1995: U.S. Geological Survey 

Water-Resources Investigations Report 97-4214, 62 p.

Klusman, R.W., and Machemer, S.D., 1991, Natural

processes of acidity reduction and metal removal from 

acid mine drainage, in Peters, D.C., ed., Geology in coal 

resource utilization: Fairfax, Va., Tech Books, p. 513- 

540.

Knapton, J.R., 1985, Field guidelines for collection, 

treatment, and analysis of water samples, Montana 

District: U.S. Geological Survey Open-File Report 85- 

409, 86 p.

Knapton, J.R., andNimick, D.A., 1991, Quality assurance 

for water-quality activities of the U.S. Geological 

Survey in Montana: U.S. Geological Survey Open-File 

Report 91-216, 41 p.

Lambing, J.H., 1991, Water-quality and transport 

characteristics of suspended sediment and trace 

elements in Streamflow of the upper Clark Fork basin 

from Galen to Missoula, Montana, 1985-90: U.S. 

Geological Survey Water-Resources Investigations 

Report 91-4139, 73 p.

Lambing, J.H., and Dodge, K.A., 1993, Quality assurance 

for laboratory analysis of suspended-sediment samples 

by the U.S. Geological Survey in Montana: U.S. 

Geological Survey Open-File Report 93-131, 34 p.

Lambing, J.H., Jones, WE., Sutphin, J.W, 1988,

Reconnaissance investigation of water quality, bottom 

sediment, and biota associated with irrigation drainage 

in the Bowdoin National Wildlife Refuge and adjacent 

areas of the Milk River basin, northeastern Montana, 

1986-87: U.S. Geological Survey Water-Resources 

Investigations Report 87-4243, 71 p.

Montana Department of Environmental Quality, 1995, 

Montana numeric water quality standards: Helena, 

Mont., Water Quality Division, Circular WQB-7, 39 p.

Montana Department of Environmental Quality, 1996, 

Abandoned hardrock mine priority sites, 1996, 

supplemental summary report: Prepared by Pioneer 

Technical Services, Inc., Butte, Mont., for the 

Abandoned Mine Reclamation Bureau [variously 

paged].

Montana Department of Environmental Quality, 1998,

Abandoned and inactive mine scoring system (AIMSS) 

list: Helena, Mont., Mine Waste Cleanup Bureau, 

Remediation Division [variously paged].

Montana Department of State Lands, 1995, Abandoned 

hardrock mine priority sites, 1995, summary report: 

Prepared by Pioneer Technical Services, Inc., Butte, 

Mont., for the Abandoned Mine Reclamation Bureau 

[variously paged].

Montana Tunnels Mining, Inc., 1997, Quality assurance 

manual: Jefferson City, Mont., Water Quality 

Laboratory, revised May 10, 1997 [variously paged].

Moreland, J.A., 1995, Quality-assurance plan for waterresources activities of the U.S. Geological Survey in 

Montana--1995, Revised: U.S. Geological Survey 

Open-File Report 91-194, Revised, 23 p.

Parrett, Charles, Johnson, D.R., and Hull, J.A., 1989, 

Estimates of monthly Streamflow characteristics at 

selected sites in the upper Missouri River basin, 

Montana, base period water years 1937-86: U. S. 

Geological Survey Water-Resources Investigations 

Report 89-4082, 103 p.

Parrett, Charles, and Carder, Kenn D., 1990, Methods for 

estimating monthly Streamflow characteristics at 

ungaged sites in western Montana: U. S. Geological 

Survey Water-Supply Paper 2365, 30 p.

Rantz, S.E., and others, 1982, Measurement and

computation of streamflow Volume 1, Measurement 

of stage and discharge: U.S. Geological Survey WaterSupply Paper 2175, 273 p.

Severson, R.C., Wilson, S.A., and McNeal, J.M., 1987, 

Analyses of bottom material collected at nine areas in 

the western United States for the DOI irrigation 

drainage task group: U.S. Geological Survey Open-File 

Report 87-490,24 p.

42 Streamflow and Water-Quality Characteristics in the Upper Tenmile Creek Watershed, Lewis and Clark County, West-Central Montana
U.S. Department of Agriculture, 1989, Soil survey of the 

Helena National Forest Area, Montana: Helena, Mont., 

U.S. Forest Service, in cooperation with the Soil 

Conservation Service and Montana Agricultural 

Experiment Station, 266 p.

U.S. Department of Health and Human Services, 1993a, 

Toxicological profile for arsenic: Life Systems, Inc., 

for Clement International Corporation for the Agency 

for Toxic Substances and Disease Registry, TP-92/02, 

unpaged.

U.S. Department of Health and Human Services, 1993b, 

Toxicological profile for cadmium: Life Systems, Inc., 

for Clement International Corporation for the Agency 

for Toxic Substances and Disease Registry, TP-92/06, 

unpaged.

U.S. Department of Health and Human Services, 1993c, 

Toxicological profile for lead: Clement International 

Corporation, for the Agency for Toxic Substances and 

Disease Registry, TP-92/12, unpaged.

U.S. Environmental Protection Agency, 1983, Methods for 

chemical analysis of water and wastes: Cincinnati, 

Ohio, Environmental Monitoring and Support 

Laboratory, EPA-600/4-79-020, unpaged.

U.S. Environmental Protection Agency, 1986, Quality 

criteria for water 1986: Washington, D.C., Office of 

Water Regulations and Standards, EPA 440/5-86-001, 

unpaged.

U.S. Environmental Protection Agency, 1991, Methods for 

the determination of organic compounds in drinking 

water: Washington, D.C., EPA Office of Research and 

Development, EPA/600/4-88/-39, method 515.1, p. 

222. (July 1991 revision of Dec. 1988 report.)

U.S. Geological Survey, 1977, National handbook of 

recommended methods for water-data acquisition-- 

Chapter 5, Chemical and physical quality of water and 

sediment: U.S. Geological Survey Office of Water Data 

Coordination, 193 p.

Ward, J.R., and Harr, C.A., eds., 1990, Methods for

collection and processing of surface-water and bedmaterial samples for physical and chemical analyses: 

U.S. Geological Survey Open-File Report 90-140,71 p.

SELECTED REFERENCES 43
Table 1. Streamflow data-collection sites and purposes, upper Tenmile Creek watershed, Montana 

[Symbols: x, signifies site used for indicated purpose; --, signifies site not used for indicated purpose]

Intended station use

Site 

number

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 

30

31

32 

33

34

Station name 

(USGS streamflow-gaging station number in parentheses)

Monitor Creek at mouth, near Rimini

Tenmile Creek below Monitor Creek, near Rimini

Tenmile Creek above Ruby Creek, near Rimini 

Ruby Creek above Scott Reservoir, near Rimini2 

Ruby Creek below Scott Reservoir, near Rimini2

Ruby Creek at mouth, near Rimini

Banner Creek above city diversion, near Rimini 

Banner Creek flume below city diversion, near Rimini2 

Banner Creek tributary near Rimini'

Banner Creek below city diversion, near Rimini

Poison Creek at mouth, near Rimini

Tenmile Creek above city diversion, near Rimini

Tenmile Creek below city diversion, near Rimini 

Beaver Creek above Chessman Reservoir, near Rimini2

Beaver Creek above tributary 3, near Rimini

Beaver Creek tributary 3 near Rimini 

Beaver Creek below tributary 3, near Rimini2

Beaver Creek tributary 2 near Rimini

Beaver Creek tributary 1 near Rimini

Beaver Creek above city diversion, near Rimini

Beaver Creek below city diversion, at Rimini

Spring Creek at mouth, at Rimini

Tenmile Creek below Spring Creek, at Rimini

Moore's Spring Creek at mouth, at Rimini

Minnehaha Creek above city diversion, near Rimini

Minnehaha Creek below city diversion, near Rimini2 

Deer Creek at mouth, near Rimini 1

Tenmile Creek near Rimini (06062500)

Moose Creek above city diversion, near Rimini 

Moose Creek below city diversion, near Rimini2

Bear Gulch at mouth, near Rimini

Walker Creek above city diversion, near Rimini 

Walker Creek below city diversion, near Rimini

Tenmile Creek at Tenmile Water Treatment Plant, near Rimini (06062750)

Estimation of longterm monthly 

natural discharge

X

X

X

X

X 

X

--

X

X

--

--

X

X

X

X

X

-

X

X

X

X

X

X

X

X

Water-quality 

sampling and 

analysis

X

X

X

X

X 

X

X

X

X

X

X

-

X

~

X

X

X

"

X

~

X

X

X

X

X

Estimation of 1997 

daily natural flow 

for Tenmile Creek 

near Rimini

~

-

X 

X

X 

X

X

_

X

X 

X

X

X

--

~

X

X

-

"

-

X

X

X

X 

X

_

X 

X

"

'Dropped from analysis due to very small flows.

2Ultimately not used for natural flow estimation; municipal water-use data were used instead.

44 Streamflow and Water-Quality Characteristics in the Upper Tenmile Creek Watershed, Lewis and Clark County, West-Central Montana
Table 2. Discharge measurement sites, drainage area sizes, measurement dates, measured stage, and discharge, upper Tenmile Creek 

watershed, Montana

[Abbreviations: ft, feet; mi, mile. Symbol: , no data]

Site 

No.

1

2

3

4

5

6

7

8

9

10

11

Site name 

(USGS streamflow-gaging 

station number 

in parentheses)

Monitor Creek at mouth, near Rimini

Tenmile Creek below Monitor Creek,

near Rimini

Tenmile Creek above Ruby Creek,

near Rimini

Ruby Creek above Scott Reservoir,

near Rimini

Ruby Creek below Scott Reservoir,

near Rimini

Ruby Creek at mouth, near Rimini

Banner Creek above city diversion,

near Rimini

Banner Creek flume below city

diversion, near Rimini

Banner Creek tributary near Rimini

Banner Creek below city diversion,

near Rimini

Poison Creek at mouth, near Rimini

Site description

Lat 46°27'21", long 112°16'48", in SW1/4NE1/4SW1/4 sec. 7, T. 8

N., R. 5 W., about 20 ft upstream from mouth and about 4.0 mi southwest of Rimini

Lat 46°27'22", long 112°16'46", in SE1/4NE1/4SW1/4 sec. 7, T. 8

N., R. 5 W., about 100 ft below the confluence of Monitor Creek and

Tenmile Creek and about 3 mi southwest of Rimini

Lat 46°27'21", long 112°15'40", in SE1/4NW1/4SW1/4 sec. 8, T. 8

N., R. 5 W., at timber bridge crossing about 0.1 mi upstream from

Ruby Creek and about 2.5 mi southwest of Rimini

Lat 46°25'54", long 112°15'59", inNEl/4SEl/4NEl/4 sec. 19, T. 8

N., R. 5 W., at Parshall flume about 100 ft upstream from Scott Reservoir and about 5.3 mi southwest of Rimini

Lat 46°25'57", long 112°15'40", inNEl/4SWl/4NWl/4 sec. 20, T. 8

N., R. 5 W., at Parshall flume below reservoir face and about 5.2 mi

southwest of Rimini

Lat 46°27'19", long 112°15'34", in SW1/4NE1/4SW1/4 sec. 8, T. 8

N., R. 5 W., about 300 ft upstream from mouth and about 2.5 mi southwest of Rimini

Lat 46°27'26", long 112°14'32", inNEl/4NWl/4SWl/4 sec. 9, T. 8

N., R. 5 W., about 50 ft above city diversion structure and about 2.2 mi

south of Rimini

Lat 46°27'28", long 112°14'32", inNEl/4NWl/4SWl/4 sec. 9, T. 8

N., R. 5 W., at Parshall flume about 100 ft downstream from city

diversion structure and about 2.2 mi south of Rimini

Lat 46° 27'40", long 1 12°14'35", in NW1/4SW1/4NW1/4 sec. 9, T. 8

N., R. 5 W., at culvert crossing on Rimini Road about 2.0 mi south of

Rimini

Lat 46°27'45", long 112°14'50", in NW1/4NW1/4NE1/4 sec. 8, T. 8

N., R. 5 W., at bridge crossing on Rimini Road about 2.3 mi south of

Rimini

Lat 46°28'38", long 112°14'39", in SW1/4NW1/4NW1/4 sec. 4, T. 8

N., R. 5 W., at culvert crossing on Rimini Road about 1.0 mi south of

Rimini

Drainage 

area, 

square 

miles

1.7

4.18

6.28

.85

1.03

2.09

3.76

3.76

.4

4.29

.32

Date

07/17/97

07/30/97

08/25/97

10/06/97

05/13/97

05/14/97

06/03/97

07/17/97

07/30/97

05/13/97

05/14/97

06/03/97

07/17/97

07/30/97

08/25/97

10/06/97

07/30/97

07/01/98

07/30/97

07/01/98

05/13/97

05/14/97

06/03/97

07/17/97

07/30/97

08/25/97

10/06/97

05/29/97

06/03/97

07/17/97

07/30/97

08/25/97

10/06/97

05/29/97

07/30/97

08/25/97

05/13/97

05/14/97

07/17/97

05/13/97

05/16/97

06/03/97

07/17/97

07/30/97

08/25/97

10/07/97

Stage, 

feet

0.68

.58

.55

.48

1.00

1.10

1.09

.56

.45

1.06

1.24

1.03

.50

.40

.37

.30

.07

.35

.15

.04

.74

.83

.91

.39

.29

.29

.39

1.00

.91

.36

.20

.17

.14

1.08

.29

.32

2.16

2.39

1.65

1.01

2.03

1.86

1.78

1.73

1.75

1.75

Discharge, 

cubic feet 

per 

second

1.38

.66

.53

.18

20.9

30.6

31.4

2.52

1.36

37

47.8

41.0

4.83

2.11

1.67

.91

.27

3.02

.24

0

8.89

10.9

17.4

.88

.33

.40

'.80

27.8

26.5

2.89

2.07

.91

.30

6.85

.28

.26

19.6

28.7

3.24

1.36

1.38

.92

.18

.10

.08

'.10

TABLE 2 45
Table 2. Discharge measurement sites, drainage area sizes, measurement dates, measured stage, and discharge, upper Tenmile Creek 

watershed, Montana (Continued)

Site 

No.

12

13

14

15

16

17

18

19

20

21

Site name 

(USGS streamflow-gaging 

station number 

in parentheses)

Tenmile Creek above city diversion,

near Rimini

Tenmile Creek below city diversion,

near Rimini

Beaver Creek above Chessman

Reservoir, near Rimini

Beaver Creek above tributary 3,

near Rimini

Beaver Creek tributary 3, near

Rimini

Beaver Creek below tributary 3,

near Rimini

Beaver Creek tributary 2 near

Rimini

Beaver Creek tributary 1 near

Rimini

Beaver Creek above city diversion,

near Rimini

Beaver Creek below city diversion,

near Rimini

Site description

Lat 46°28'53", long 112°14'41", in NW1/4NW1/4NW1/4 sec. 4, T. 8

N., R. 5 W., about 0.2 mi upstream from city diversion, about 100 ft

west of Rimini Road, and about 0.1 mi south of Rimini

Lat 46°29'02", long 1 12°14'44", in NW1/4NW1/4NW1/4 sec. 4, T. 8

N., R. 5 W., at bridge to residence about 200 ft west of main road

through Rimini, and about 0. 1 mi upstream from Beaver Creek crossing at the south end of Rimini

Lat 46°27'59", long 112°H'03", in NE1/4NE1/4NE1/4 sec. 11, T. 8

N., R. 5 W., about 150 ft south of causeway at south end of Chessman

Reservoir, about 100 ft upstream from highwater line of reservoir, and

about 3.5 mi southeast of Rimini

Lat 46°28'14", long 112°ir44", inNWl/4SEl/4SWl/4 sec. 2, T. 8

N., R. 5 W., about 300 ft downstream from reservoir outlet, 100 ft

upstream from Beaver Creek tributary 3, and about 3 mi southeast of

Rimini

Lat 46°28 03", long 112°11'47", in SW1/4SE1/4SW1/4 sec. 2, T. 8

N., R. 5 W., about 10 ft above Banner Creek flume, about 0.2 mi

southwest of Chessman Reservoir outlet, and about 3 mi southeast of

Rimini

Lat 46°28'14", long 112°H'46", inNWl/4SEl/4SWl/4 sec. 2, T. 8

N., R. 5 W., at Parshall flume, about 50 ft downstream from Beaver

Creek tributary 3, about 400 ft downstream from reservoir outlet, and

about 3 mi southeast of Rimini

Lat 46°27'58", long 112°12'30", in SW1/4SE1/4SE1/4 sec. 3, T. 8 N.,

R. 5 W., about 40 ft upstream from inlet structure to Banner Creek

flume, about 100 ft upstream from Banner Creek flume, and about 2.5

mi southeast of Rimini

Lat 46°29'07", long 1 12°13'04", in NW1/4NE1/4NW1/4 sec. 3, T. 8

N., R. 5 W., about 100 ft downstream from culvert crossing on Park

Lake Road, about 0.2 mi upstream from mouth and about 1.5 mi east

of Rimini

Lat 46°29'02", long 1 12°14'09", in NW1/4NW1/4NE1/4 sec. 4, T. 8

N., R. 5 W., at Parshall flume, about 20 ft south of Park Lake Road,

and about 0.5 mi upstream from mouth near Rimini

Lat 46°29'06", long 112°14'37", in NW1/4NW1/4NW1/4 sec. 4, T. 8

N., R. 5 W., about 100 ft upstream from culvert crossing on Rimini

Road, about 200 ft downstream from city diversion structure at Rimini

Drainage 

area, 

square 

miles

15.2

15.3

.75

1.33

.5

1.92

.67

.86

6.44

6.62

Date

05/07/97

05/29/97

06/03/97

08/04/97

08/25/97

10/07/97

05/06/98

05/07/97

05/14/97

07/14/97

05/06/98

05/08/97

06/27/97

08/26/97

10/07/97

10/09/97

05/08/97

06/27/97

08/01/97

-

05/08/97

05/16/97

06/04/97

06/27/97

08/01/97

08/26/97

10/07/97

05/09/97

06/27/97

08/04/97

05/09/97

05/16/97

06/04/97

08/04/97

08/26/97

10/07/97

05/29/97

06/03/97

10/06/97

Stage, 

feet

.40

.96

.91

.29

.29

.28

.84

4.20

4.63

3.75

4.42

.46

.34

3.99

4.83

4.62

.34

.41

.26

.34

.56

.43

.38

.31

.29

.29

.95

.78

.53

.68

.84

.97

.40

.32

.59

1.06

.84

.12

Discharge, 

cubic feet 

per 

second

33.5

97.2

94.2

4.68

4.11

'3.57

64.1

26.3

106

8.34

53.3

1.11

.84

.11

'3.37

2.54

.57

1.27

.25

-

.64

4.20

2.16

.92

.49

.25

'.32

1.41

.80

.29

7.56

10.1

13.7

4.02

2.16

'5.91

13.1

8.23

.05

46 Streamflow and Water-Quality Characteristics in the Upper Tenmile Creek Watershed, Lewis and Clark County, West-Central Montana
Table 2. Discharge measurement sites, drainage area sizes, measurement dates, measured stage, and discharge, upper Tenmile Creek 

watershed, Montana (Continued)

Site 

No.

22

23

24

25

26

27

28

29

30

Site name 

(USGS streamflow-gaging 

station number 

in parentheses)

Spring Creek at mouth, at Rimini

Tenmile Creek below Spring Creek,

at Rimini

Moore's Spring Creek at mouth, at

Rimini

Minnehaha Creek above city diversion, near Rimini

Minnehaha Creek below city diversion, near Rimini

Deer Creek at mouth, near Rimini

Tenmile Creek near Rimini

(06062500)

Moose Creek above city diversion,

near Rimini

Moose Creek below city diversion,

near Rimini

Site description

Lat 46°29'21", long 112°14'57", in SW1/4NW1/4SW1/4 sec. 33, T. 8

N., R. 5 W., about 100 ft upstream from Banks residence, about 0.2 mi

upstream from mouth, at Rimini

Lat 46°29'22", long 112°14'54", in NW1/4SW1/4SW1/4 sec. 33, T. 8

N., R. 5 W., at bridge crossing on road to Banks residence at Rimini

Lat46°29'32", long 112°14'58", inNWl/4NWl/4SWl/4 sec. 33, T. 8

N., R. 5 W., at culvert crossing on Rimini Road at Rimini

Lat 46°30'23", long 112°15'37", in NW1/4NW1/4SE1/4 sec. 29, T. 9

N., R. 5 W., about 75 ft upstream from city diversion structure, about

200 ft upstream from mouth, and about 3.0 mi north of Rimini

Lat 46°30'23", long 112°15'37", in NW1/4NW1/4SE1/4 sec. 29, T. 9

N., R. 5 W., about 40 ft downstream from city diversion structure,

about 90 ft upstream from mouth, and about 3.0 mi north of Rimini

Lat 46°30'48", long 112°15'41", in NE1/4NE1/4NW1/4 sec. 29, T. 8

N., R. 5 W., about 50 ft upstream from mouth, and about 2.5 mi north

of Rimini

Lat 46031'27", long 11 2° 15 '22", in NE1/4SE1/4NE1/4 sec. 20, T. 9

N., R. 5 W., on left bank at U.S. Forest Service Moose Creek picnic

grounds, 500 ft upstream from Moose Creek, and 2.5 mi north of

Rimini

Lat46°31'29", long 112°15'10", inNEl/4SEl/4NEl/4 sec. 20, T. 9

N., R. 5 W., about 75 ft upstream from city diversion structure, about

0.1 mi east of Rimini Road, and about 4.0 mi north of Rimini

Lat46°3r29", long 112°15'10", inNEl/4SEl/4NEl/4 sec. 20, T. 9

N., R. 5 W., about 10 ft downstream from city diversion structure,

Drainage

area, Date 

square

miles

.64 05/09/97

05/15/97

06/04/97

08/26/97

10/07/97

22.8 05/15/97

06/04/97

08/26/97

10/06/97

10/07/97

10/09/97

.6 05/09/97

06/27/97

08/04/97

10/09/97

5.35 05/09/97

05/15/97

06/02/97

06/27/97

08/04/97

08/27/97

10/08/97

5.35 05/09/97

06/27/97

07/14/97

08/04/97

.77 06/27/97

30.9 05/12/97

05/15/97

05/16/97

05/30/97

06/04/97

07/11/97

08/27/97

09/05/97

10/08/97

2.86 05/15/97

06/02/97

08/04/97

08/27/97

10/09/97

2.86 08/04/97

08/27/97

Stage, 

feet

.54

.85

.58

.33

.33

~

~

1.93

1.95

-

2.31

.24

.39

.29

.25

.84

2.16

.97

.71

.51

.50

.50

3.29

2.91

2.68

2.52

.66

2.54

2.84

2.93

2.93

2.65

1.92

1.43

1.23

1.64

1.36

1.33

1.16

22.06

22.14

1.69

2.03

Discharge, 

cubic feet 

per 

second

1.45

5.81

2.38

.29

'.31

103

91.7

.39

.36

4.50

3.48

.41

.65

.18

.06

12.4

27.3

17.9

7.5

2.22

1.74

'2.17

11.6

.89

.26

.09

.08

'92.0

'135

157

147

'92.3

17.6

'2.22

.88

'6.41

2.56

2.45

.84

1.03

.45

.005

.13

about 0.1 mi east of Rimini Road, and about 4.0 mi north of Rimini

TABLE 2 47
Table 2. Discharge measurement sites, drainage area sizes, measurement dates, measured stage, and discharge, upper Tenmile Creek 

watershed, Montana (Continued)

Site name 

Site (USGS streamflow-gaging 

No. station number 

in parentheses)

3 1 Bear Gulch at mouth, near Rimini

32 Walker Creek above city diversion,

near Rimini

33 Walker Creek below city diversion,

near Rimini

34 Tenmile Creek at Tenmile Water

Treatment Plant, near Rimini

(06062750)

Site description

Lat 46°32'39", long 112°14'42", in NE1/4NW1/4NW1/4 sec. 16, T. 9

N., R. 5 W, about 50 ft upstream from culvert crossing on Rimini

Road, and about 5.0 mi north of Rimini

Lat 46°33'44", long 112°14'19", in NW1/4NW1/4SE1/4 sec. 4, T. 9

N., R. 5 W, about 50 ft upstream from city diversion structure, about

0.1 mi upstream from mouth, and about 6.0 mi north of Rimini

Lat46°33'44", long 112°14'19", inNWl/4NWl/4SEl/4 sec. 4, T. 9

N., R. 5 W, at downstream end of city diversion structure, about 0.1

mi upstream from mouth, and about 6.0 mi north of Rimini

Lat 46°34'19", long 112°12'52", in SE1/4SW1/4SE1/4 sec. 34, T. 10

N., R. 5 W, on left bank at bridge to Helena Water Treatment Plant,

about 0.2 mi south of U.S. Highway 12, and about 8 mi north of

Rimini

Drainage

area, Date 

square

miles

1.06 05/09/97

05/16/97

05/29/97

06/02/97

07/14/97

08/27/97

10/08/97

11.3 05/12/97

05/16/97

06/02/97

08/04/97

08/27/97

10/08/97

11.3 05/12/97

08/04/97

51.1 05/07/97

05/15/97

06/05/97

06/11/97

06/25/97

07/08/97

08/13/97

08/27/97

08/27/97

10/07/97

Stage, 

feet

.35

.38

.38

.35

.23

.21

.22

1.66

1.96

1.64

.54

.54

.70

1.17

.51

2.26

2.80

2.54

2.86

2.06

1.76

1.44

1.52

1.68

--

Discharge, 

cubic feet 

per 

second

1.55

1.36

1.52

1.26

.28

.10 '.18

21.3

28.6

19.0

1.71

1.25

^.68

21.6

1.71

72.5

177

108

199

39.4

17.7

2.20

4.69

'5.20

3 8.10

'Estimated from instantaneous stage reading applied to stage-discharge relationship. 

2Stage-discharge relationship invalid because of backwater conditions.

3rDaily mean discharge from continuously recorded stage.

48 Streamflow and Water-Quality Characteristics in the Upper Tenmile Creek Watershed, Lewis and Clark County, West-Central Montana
Table 3. Net monthly discharges into Scott and Chessman Reservoirs calculated from daily water-use data at Tenmile Water Treatment 

Plant, Montana

[Net monthly discharge into either reservoir is negative whenever outflow exceeds inflow]

Water

year Oct

1991 0

1992 -2.55

1993 -.94

1994 -.02

1995 0

1996 -.15

1997 -.68

1998 -1.42

1999 -.78

Net monthly discharge into Scott Reservoir, in cubic feet per second

Nov.

0

-3.11

-.76

-.31

0

-.27

-.22

-1.42

Average net monthly inflow

Water

year Oct.

1991 -2.32

1992 0

1993 -.45

1994 0

1995 -.68

1996 -.80

1997 -3.50

1998 -2.68

1999 -1.40

Dec.

0

-2.34

-.39

-.31

0

-.47

-.81

-1.42

-0.71

Jan.

0

0

0

-1.03

0

-.47

-.81

-1.42

Feb.

0

0

-.78

-1.40

0

-.48

-.81

-1.42

Mar.

0

0

-.68

-.91

0

-.47

-.52

-1.42

Apr.

0

0

0

-.32

0

-.17

0

-.02

May

0

-.04

0

0

0

0

0

0

June

0

-.53

0

0

0

.64

0

0

July

0

-.74

0

-1.77

-.02

-.58

-.04

0

Aug.

-1.49

-3.76

0

-6.93

-4.24

-3.27

-.08

-1.25

Sept.

-1.78

-2.06

0

-.41

-1.48

-2.16

-1.65

-4.00

Net monthly discharge into Chessman Reservoir, in cubic feet per second

Nov. Dec. Jan.

-2.40

0

-1.21

0

-.66

-.70

-3.01

-1.96

-3.30

-1.24

-1.74

0

-1.31

-1.58

-2.38

-1.97

-2.86

-1.95

-2.95

0

-1.90

-1.36

-2.18

-1.11

Feb.

-2.21

-1.15

-2.69

0

-1.45

-2.40

-1.78

-1.15

Mar.

-1.82

-.15

-2.18

0

-.41

-2.57

-.62

-.80

Apr.

-0.03

.76

0

0

0

-.52

0

0

May

0

3.45

6.17

-.36

5.00

2.57

5.84

3.25

June

0

0

7.95

-.57

-.67

5.50

9.18

2.59

July

0

0

1.57

-.05

0

-2.25

1.55

-1.89

Aug.

0

-.31

0

0

0

-5.32

0

-1.66

Sept.

0

-2.15

0

-4.76

-.66

-4.13

-2.24

-1.85

Average net monthly inflow -0.46

TABLE 3 49
Table 4. Monthly mean discharge diverted to Tenmile Water Treatment Plant, Montana

Water 

year

1991

1992

1993

1994

1995

1996

1997

1998

1999

Discharge, in cubic feet per second

Oct.

5.6

5.9

5.5

5.0

5.5

5.2

6.0

5.6

5.8

Nov.

4.3

4.8

4.9

5.0

4.5

4.7

4.9

4.9

Dec.

4.9

4.6

4.7

4.7

4.6

4.6

4.7

4.8

Jan.

5.2

4.8

5.4

4.7

4.7

4.5

5.2

4.9

Feb.

4.8

4.8

5.6

4.7

4.9

5.3

4.9

5.1

Mar.

4.8

4.9

6.0

4.7

7.2

4.9

4.4

5.1

Apr.

4.9

5.0

5.3

5.3

6.1

4.8

5.1

5.8

May

6.5

10.4

8.3

8.1

7.2

5.7

8.0

10.1

June

7.5

8.1

8.3

11.3

8.3

10.2

8.9

7.3

July

9.4

6.0

6.7

12.7

10.3

12.7

11.2

11.1

Aug.

6.5

8.4

7.6

12.6

11.7

12.4

9.2

12.1

Sept.

6.3

7.5

5.9

9.4

7.7

9.0

8.5

10.1

50 Streamflow and Water-Quality Characteristics in the Upper Tenmile Creek Watershed, Lewis and Clark County, West-Central Montana
Table 5. Natural flow accretions forTenmile Creek near Rimini, Montana

Water 

year

1991

1992

1993

1994

1995

1996

1997

1998

1999

Average

Discharge, in cubic feet per second

Oct.

2.2

2.4

3.2

4.2

3.9

3.3

.8

.6

2.6

2.6

Nov.

1.1

.9

2.1

3.8

3.1

3.0

.9

.7

2.0

Dec.

0.8

.2

1.8

3.6

2.5

1.8

.8

.6

1.5

Jan.

1.4

2.0

1.6

2.9

2.0

1.9

1.3

1.6

1.8

Feb.

1.8

2.8

1.2

2.5

2.6

1.5

1.5

1.7

2.0

Mar.

2.2

3.9

2.2

3.0

3.7

1.0

2.5

2.0

2.6

Apr.

4.1

4.1

4.4

4.1

5.1

3.4

4.2

4.8

4.3

May

12.5

19.1

20.1

13.4

18.0

14.3

19.5

18.7

17.0

June

13.3

13.2

21.8

15.9

13.3

21.7

23.6

15.6

17.3

July

7.8

4.3

7.2

8.8

8.5

7.8

10.8

7.3

7.8

Aug.

3.9

3.0

6.3

3.5

5.5

1.7

7.6

7.2

4.9

Sept.

3.4

2.1

4.9

2.7

4.3

1.2

3.2

2.6

3.0

Annual

4.6

4.9

6.4

5.7

6.1

5.2

6.4

5.3

5.6

TABLE 5 51
Table 6. Estimated average monthly and annual natural discharges 

for Tenmile Creek near Rimini, Montana, for water years 1961-90 

based on monthly recorded discharge plus natural flow accretion

Discharge, in cubic feet per second

Month

Oct.

Nov.

Dec.

Jan.

Feb.

Mar.

Apr.

May

June

July

Aug.

Sept.

Average recorded

3.5

2.5

1.7

1.5

1.3

2.5

15.6

83.6

72.6

12.7

2.6

2.9

Average natural 

flow accretion

2.6

2.0

1.5

1.8

2.0

2.6

4.3

17.0

17.3

7.8

4.9

3.0

Average 

natural

6.1

4.6

3.3

3.3

3.3

5.1

19.9

100.6

89.9

20.5

7.5

5.9

Annual 17.0 5.6 22.6

52 Streamflow and Water-Quality Characteristics in the Upper Tenmile Creek Watershed, Lewis and Clark County, West-Central Montana
Table 7. Regression results for flow estimation sites, upper Tenmile Creek watershed, Montana 

[Abbreviations: a", regression constant; b, regression coefficient; R2 , coefficient of determination; SE, standard error in log units]

Site name 

Site No. (USGS streamflow-gaging station 

number in parentheses)

1

2

3

6

7

11

12

16

18

19

20

22

24

25

29

31

32

34

Monitor Creek at mouth, near Rimini

Tenmile Creek below Monitor Creek, near Rimini

Tenmile Creek above Ruby Creek, near Rimini

Ruby Creek at mouth, near Rimini

Banner Creek above city diversion, near Rimini

Poison Creek at mouth, near Rimini

Tenmile Creek above city diversion, near Rimini

Beaver Creek tributary 3 near Rimini

Beaver Creek tributary 2 near Rimini

Beaver Creek tributary 1 near Rimini

Beaver Creek above city diversion, near Rimini

Spring Creek at mouth, at Rimini

Moore's Spring Creek at mouth, near Rimini

Minnehaha Creek above city diversion, near Rimini

Moose Creek above city diversion, near Rimini

Bear Gulch at mouth, near Rimini

Walker Creek above city diversion, near Rimini

Tenmile Creek at Tenmile Water Treatment Plant, near Rimini (06062750)

Regression parameters

i a

0.026

.040

.135

.004

.035

.015

.203

.004

.056

.078

.346

.050

.160

.155

.242

.022

.127

1.20

b

1.12

1.30

1.15

1.67

1.31

.822

1.23

1.41

.728

.577

.868

.896

.038

1.02

.509

.838

1.04

1.00

R2

0.80

.99

.98

.97

.95

.82

.98

.94

.90

.89

.92

.90

.01

.91

.71

.70

.92

.99

SE

0.12

.06

.07

.14

.17

.20

.09

.18

.13

.10

.15

.16

.18

.15

.16

.21

.15

.09

TABLE 7 53
Table 8. Estimated long-term mean monthly and mean annual natural discharge for selected sites in the upper Tenmile Creek watershed, Montan

 o

"8

Site 

No.

1

2

3

6

7

11

12

16

18

19

20

22

24

25

28

29

31

32

34

Site name 

(USGS streamflow-gaging 

station numbers in parentheses)

Monitor Creek at mouth, near Rimini

Tenmile Creek below Monitor Creek, near Rimini

Tenmile Creek above Ruby Creek, near Rimini

Ruby Creek at mouth, near Rimini

Banner Creek above city diversion, near Rimini

Poison Creek at mouth, near Rimini

Tenmile Creek above city diversion, near Rimini

Beaver Creek tributary 3 near Rimini

Beaver Creek tributary 2 near Rimini

Beaver Creek tributary 1 near Rimini

Beaver Creek above city diversion, near Rimini

Spring Creek at mouth, at Rimini

Moore's Spring Creek at mouth, near Rimini

Minnehaha Creek above city diversion, near Rimini

Tenmile Creek near Rimini (06062500)

Moose Creek above city diversion, near Rimini

Bear Gulch at mouth, near Rimini

Walker Creek above city diversion, near Rimini

Tenmile Creek at Tenmile Water Treatment Plant, near

Rimini (06062750)

Mean natural discharge, in cubic feet per second

Oct

0.20

.42

1.08

.08

.38

.07

1.87

.05

.21

.22

1.67

.25

.17

.98

6.12

.61

.10

.83

7.37

Nov.

0.14

.29

.77

.05

.25

.05

1.30

.03

.17

.19

1.29

.19

.17

.72

4.55

.52

.08

.61

5.47

Dec.

0.10

.19

.54

.03

.17

.04

.89

.02

.13

.16

.98

.15

.17

.53

3.33

.45

.06

.44

4.00

Jan.

0.10

.19

.52

.03

.16

.04

.86

.02

.13

.15

.96

.14

.17

.51

3.25

.44

.06

.43

3.90

Feb.

0.10

.19

.53

.03

.17

.04

.88

.02

.13

.16

.97

.15

.17

.52

3.29

.44

.06

.44

3.95

Mar.

0.16

.34

.89

.06

.30

.06

1.51

.04

.18

.20

1.43

.22

.17

.82

5.13

.56

.09

.69

6.17

Apr.

0.74

1.95

4.20

.58

1.75

.17

7.94

.27

.49

.44

4.63

.73

.18

3.24

19.9

1.11

.27

2.83

24.0

May

4.55

16.1

27.1

8.76

14.7

.66

58.2

2.63

1.61

1.12

18.9

3.11

.19

16.9

100

2.53

1.05

15.3

122

June

4.01

13.9

23.8

7.25

12.7

.61

50.6

2.24

1.48

1.05

17.2

2.81

.19

15.0

89.9

2.39

.95

13.6

109

2

2

O
Table 9. Streamflow sampling sites and months of water-quality sample collection during 1997, upper 

Tenmile Creek watershed, Montana

Site 

number

1

2

3

6

7

9

10

11

12

13

15

18

20

22

23

25

28

29

31

32

34

Site name 

(USGS streamflow-gaging station 

numbers in parenthesis)

Monitor Creek at mouth, near Rimini

Tenmile Creek below Monitor Creek near Rimini

Tenmile Creek above Ruby Creek, near Rimini

Ruby Creek at Mouth, near Rimini

Banner Creek above city diversion, near Rimini

Banner Creek tributary near Rimini

Banner Creek below city diversion, near Rimini

Poison Creek at mouth, near Rimini

Tenmile Creek above city diversion, near Rimini

Tenmile Creek below city diversion, near Rimini

Beaver Creek above tributary 3, near Rimini

Beaver Creek tributary 2 near Rimini

Beaver Creek above city diversion, near Rimini

Spring Creek at mouth, at Rimini

Tenmile Creek below Spring Creek, at Rimini

Minnehaha Creek above city diversion, near Rimini

Tenmile Creek near Rimini (06062500)

Moose Creek above city diversion, near Rimini

Bear Gulch at mouth, near Rimini

Walker Creek above city diversion, near Rimini

Tenmile Creek at Tenmile Water Treatment Plant, near Rimini

(06062750)

Month of sample collection

August, October

May, June

May, June, August, October

May, June, August, October

June, August, October

August

May

May, June, August, October

June, August, October

May

August, October

May, June, August, October

May, June, August, October

May, June, August, October

May, June, August, October

May, June, August, October

May, June, August, October

May, June, August, October

May, June, August, October

May, June, August, October

May, June, August, October

TABLE 9 55
Table 10. Laboratory methods, minimum reporting levels, and water-quality standards for constituents analyzed in water 

samples from upper Tenmile Creek watershed, Montana

[Abbreviations: ug/L, micrograms per liter; mg/L, milligrams per liter. Symbol: --, no guideline concentrations established]

Constituent

Calcium 

Magnesium 

Sodium 

Potassium

Sulfate

Chloride

Fluoride

Method1

215.1 

242.1 

273.1 

258.1

300.0

300.0

300.0

Minimum 

reporting level2

Water-quality standard3

Human health

Aquatic life

Acute toxicity Chronic toxicity

MAJOR IONS (dissolved, mg/L)

1

.1 

.1 

.1

1

1

.1

-

4

-

860

-

-

230

--

NUTRIENTS (dissolved, mg/L)

Nitrate4

Nitrite4

Ammonia

Phosphate4

Phosphorus, ortho4

300.0

300.0

350.3

365.3

365.3

.01

.01

.05

.01

.01

10

1

-

-

59.5

-

-

5 1.9

-

--

TRACE ELEMENTS (ug/L)6

Aluminum7

Arsenic

Cadmium

Chromium III8

Copper8

Iron9

Lead8

Manganese

Mercury

Nickel8

Selenium

Silver8

Zinc8

200.7

206.2

213.2

200.7

200.7

200.7

239.2

200.7

245.2

200.7

270.2

200.7

200.7

100

3

.1

1

1

10

3

5

.6

20

1

3

10 10

-

18

5

100

1,000

300

15

50

.14

100

50

..

5,000

750

360

3.9

1,700

18

-

82

~

2.4

1,400

20

4.1

120

87

190

1.1

210

12

1,000

3.2

--

.012

160

5

110

'U.S. Environmental Protection Agency (1983, 1991); Montana Tunnels Mining, Inc. (1997).

2 Minimum reporting level for major ion, nutrient, and trace element analyses by Montana Tunnels Laboratory. Minimum reporting levels for 

replicate analyses by U.S. Geological Survey (for quality control) may differ.

3 Montana Department of Environmental Quality (1995).

4 A plant nutrient, excessive amounts of which may cause violations of Administrative Rules of Montana (ARM) 16.20.633.(l)(e).

Toxicity standards for ammonia are based on a pH of 7.7 and a temperature of 11.5 degrees Celsius.

Aquatic-life standards refer to total-recoverable concentrations, except for the standard for aluminum, which refers to the dissolved

concentration.

7Montana aquatic-life standard for aluminum concentrations applicable only for pH between 6.5 and 9.0.

8Aquatic-life Standards are hardness dependent. Standards listed are based on total hardness of 100 mg/L as CaCO3 . Equations for hardnessdependent criteria are presented in table 15. 

9Human-health standard is for aesthetic purposes only. 

10Minimum reporting level revised upward to 100 ng/L as a result of zinc contamination of sample preservative.

56 Streamflow and Water-Quality Characteristics in the Upper Tenmile Creek Watershed, Lewis and Clark County, West-Central Montana
Table 11. Bottom-sediment sampling sites and depths, Chessman Reservoir, upper Tenmile Creek watershed, Montana

_. ., _,. Sample depth, in inches below Site No. Site name K .. . f

sediment surface

Rl Chessman Reservoir Southwest (M

R2A Chessman Reservoir Northeast 0-7

R2B Chessman Reservoir Northeast 7-9

R3 Wetland above Chessman Reservoir 0-9

R4 Chessman Reservoir Southeast 0-6

TABLE 11 57
Table 12. Field-measured parameters and concentrations of major ions and nutrients in streams in the upper Tenmile Creek watershed, 

Montana

[Abbreviations: °C, degrees Celsius; inst., instantaneous; uS/cm, microsiemens per centimeter at 25°C; mg/L, milligrams per liter. Symbols: <, less than; ~ 

no data. BLANKS are quality-control samples of deionized water]

Site number 

(fig- 1)

1

2

3

6

7

9

10

11

12

13

15

18

20

22

23

Date

08-25-97

10-06-97

05-14-97

06-03-97

05-14-97

06-03-97

08-25-97

10-06-97

05-14-97

06-03-97

08-25-97

10-06-97

06-03-97

08-25-97

10-06-97

08-25-97

05-14-97

05-16-97

06-03-97

08-25-97

10-07-97

06-03-97

08-25-97

10-07-97

05-14-97

08-26-97

10-07-97

05-16-97

06-04-97

08-26-97

10-07-97

05-16-97

06-04-97

08-26-97

10-07-97

05-15-97

06-04-97

08-26-97

10-07-97

05-15-97

06-04-97

08-26-97

08-26-97 '

10-07-97

Discharge, 

inst., 

(cubic feet 

per second)

0.53

.18

30.6

31.4

47.8

41

1.67

.91

10.9

17.4

.40

.80

26.5

.91

.30

.26

28.7

1.38

.92

.08

.10

94.2

4.11

3.57

106

.11

3.37

4.20

2.16

.25

.32

10.1

13.7

2.16

5.91

5.81

2.38

.29

.31

103

91.7

.39

.39

4.50

Specific 

conductance, 

field

(uS/cm)

52.0

66.5

54.0

30.0

34.0

30.0

47.9

49.2

35.0

22.0

42.1

27.8

35.0

57.7

67.8

23.4

3.0

164

212

231

228

36.0

67.4

63.8

38.0

86.0

46.8

30.0

45.0

55.0

58.4

44.0

40.1

61.0

56.4

27.0

44.8

55.0

55.8

38.0

35.2

224

224

77

pH, 

field 

(standard 

units)

7.2

7.3

6.7

7.1

6.8

7.0

7.6

7.1

7.4

7.4

7.3

7.2

6.8

7.5

7.6

7.2

7.3

4.0

3.9

3.8

3.8

7.9

7.2

7.8

7.2

6.9

7.0

7.2

7.2

7.2

7.0

7.7

7.4

7.6

7.1

7.1

7.0

7.1

6.9

7.0

7.1

5.9

5.9

6.9

Temperature, 

water

9.0

3.0

2.0

6.0

4.5

7.5

10.0

4.0

3.0

7.0

9.0

4.0

8.5

11.5

3.5

8.0

4.0

3.0

10.5

13.0

4.5

5.0

9.0

4.5

3.0

12.0

8.5

2.0

5.5

9.0

3.0

3.0

8.5

12.0

6.0

4.5

9.5

10.0

4.5

3.5

7.5

12.0

12.0

5.2

Hardness 

(mg/L as 

CaCO3)

21

20

14

10

10

10

21

15

14

9

24

9

12

40

27

13

14

29

35

50

49

16

31

23

13

36

15

<10

13

21

20

14

13

25

20

<10

13

20

12

12

12

81

81

26

Calcium 

(mg/L as 

Ca)

6.7

6.1

4.5

2.6

3.3

2.5

6.8

4.3

4.4

2.5

7.8

3.8

3.8

10

8.2

4.5

4.4

8.2

9.2

15

14

4.4

9.9

6.7

4.1

11

4.4

2.8

4.2

6.8

6.3

4.1

3.7

7.7

6.1

2.3

3.7

6.1

4.6

3.6

3.5

22

22

7.4

Magnesium 

(mg/L as 

Mg)

1.1

1.1

.7

.9

.5

.9

.9

.9

.8

.7

1.1

< !

.7

1.3

1.6

.5

.7

2.0

3.0

2.9

3.4

1.2

1.5

1.5

.7

1.9

.9

.4

.7

.9

1.0

1.0

.9

1.4

1.2

.6

1.0

1.3

< !

.8

.7

6.3

6.2

1.9

Sodium 

(mg/L as 

Na)

2.1

2.6

1.6

1.4

1.6

1.6

2.4

2.8

1.1

.8

1.1

.7

1.1

1.4

1.6

.9

.8

2.0

2.2

2.6

3.0

1.3

2.0

1.8

1.2

3.2

2.2

1.2

1.6

2.3

2.5

1.8

1.7

2.7

2.4

1.4

1.7

2.3

2.2

1.4

1.3

3.4

3.5

2.3

Sodium 

adsorption 

ratio

0.2

.3

.2

.2

.2

.2

.2

.3

.1

.1

.1

~

.1

.1

.1

.1

.1

.2

.2

.2

.2

.1

.2

.2

.1

.2

.2

.2

.2

.2

.2

.2

.2

.2

.2

.2

.2

.2

~

.2

.2

.2

.2

.2

58 Streamflow and Water-Quality Characteristics in the Upper Tenmile Creek Watershed, Lewis and Clark County, West-Central Montana
Table 12. Field-measured parameters and concentrations of major ions and nutrients in streams in the upper Tenmile Creek watershed, 

Montana (Continued)

Potassium, Bicardissolved bonate 

(mg/L as (mg/L as 

K) HC03)

1.2 

1.6

1.2 

1.0

1.2

1.0

1.0

1.1

<.l

.6

.5

.7

.7

.6

.7

.7

.8

1.8

1.5

1.6

1.7

.8

.9

1.0

.9

.1

.2

.0

.1

.2

.6

.0

.0

.2

.3

.9

.2

.2

.3

1.0

.8

1.5

1.6

1.1

13 

13

15

16

-

19

11

25

27

7

--

..

-

21

17

-

37

15

10

17

18

12

23

19

..

8

13

13

9

<5

<5

15

Alkalinity 

(mg/L as 

CaCO3

10 

11

6 

6

6

8

12

13

12

8

16

9

10

21

22

6

11

-

8

17

14

8

31

13

9

8

14

15

12

10

18

16

6

7

11

11

9

8

<5

<5

13

Sulfate, Chloride, ..,, ,, 

.. .... , . Fluonde, dissolved dissolved / n , n dissolved (mg/L as (mg/L as . ^

so4) c») (mg/LasF)

11 <1.

17 <1.

9.9 <1. 

6.8 <1.

7.0 <1.

5.9 <1.

7.3 <!.<

8.6 <!.(

2.6 <1.

2.1 <!.(

2.9 <1.

2.8 <!.(

4.5 <!.(

6.6 <!.(

9.3 <!.(

3.1 <!.(

4.4 <!.(

55 <!.(

71 <!.(

94 <!.(

92 <!.(

5.8 <!.(

13 <!.(

14 <!.(

6.9 <!.(

8.8 <!.(

8.1 <!.(

4.5 <!.(

11 <!,(

11 <!.(

11 <!.(

7.8 <!.(

7.0 <!.(

9.7 <!.(

9.9 <!.(

5.4 <!.(

13 <!.(

13 <!.(

13 <!.(

7.2 <!.(

7.1 <!.(

97 <!.(

99 <!.(

19 <!.(

3 0.14 

3 .13

3 <.10 

3 <.10

3 <.10

3 <.10

3 <.10

3 .11

3 <.10

3 .10

3 <.10

3 <.10

3 <.10

3 <.10

) <.10

3 .68

3 <.10

3 .13

3 .16

3 .17

3 .26

3 <.10

3 <.10

3 <.10

3 <.10

3 <.10

) <.10

) <.10

3 <10

3 .60

3 <.10

3 <.10

3 <.10

) .57

) <.10

3 <.10

) <.10

) <.10

) <.10

) <.10

) <.10

) .15

) .18

) <,10

Nitrate, 

dissolved 

(mg/L as

N)

0.01 

.01

.07 

.06

.05

.01

<.01

<.01

.04

<.01

.03

<.01

.01

<.01

.10

.36

.02

.06

.07

.10

.10

.01

.03

.01

.03

.05

.03

.03

.03

.04

.03

.07

.03

.05

<.01

.07

<.01

<.01

.02

.03

<.01

.12

.11

<.01

Nitrite, . 

,. , , Ammonia, dissolved ,. , . 

, _ dissolved (mg/L as . ... ^ (mg/L as N)

<0.01 <0.05 

<.01 <.05

<.01 <.05 

<.01 <.05

<.01 <.05

<.01 <.05

<01 <.05

<.01 .05

<01 <.05

<.01 <.05

<.01 <.05

<.01 <.05

<.01 <.05

<.01 <.05

<.0l <.05

<.01 <.05

<.01 <.05

<.01 <.05

<.01 <.05

<.01 <.05

<.01 <.05

<.01 <.05

<.01 <.05

<.01 <.05

<.01 <.05

<.01 .07

<.01 <.05

<.01 <.05

<,01 <.05

<.01 <.05

<.01 <.05

<.01 <.05

<.01 <.05

<.01 <.05

<.01 <.05

<.01 <.05

<.01 <.05

<.01 <.05

<.01 <.05

<.01 <.05

<.01 <.05

<.01 <.05

<.01 <.05

.02 <.05

Phosphate, 

Phosphorus, ortho, 

total dissolved 

(mg/L as P) (mg/L as 

P04)

0.01 <0.01 

.01 <.01

.03 <.01

.03 <.01

.01 <.01

.01 <.01

.01 <.01

.02 <.01

.02 <.01

.01 <.01

.01 <.01

.03 <.01

.01 <.01

<.01 <.01

.01 <.01

.05 <.01

.09 <.01

.02 <01

<.01 <01

.01 <.01

.01 <.01

.02 <.01

.01 <.01

.04 <.01

.16 .04

.04 <.01

.02 <.01

.02 .01

.01 <.01

<.01 <01

.03 <.01

.02 <.01

.02 <.01

.03 <.01

.04 <.01

.01 <01

.02 <.01

.02 <.01

.03 <.01

.02 <.01

.06 <.01

.06 <.01

.05 <.01

Site number 

(fig. 1)

1

2

3

6

7

9

10

11

12

13

15

18

20

22

23

TABLE 12 59
Table 12. Field-measured parameters and concentrations of major ions and nutrients in streams in the upper Tenmile Creek watershed, 

Montana (Continued)

Discharge, 

Site number inst, 

(fig. 1) a C (cubic feet 

per second)

25

28

29

31

32

34

05-15-97

06-02-97

08-27-97

10-08-97

05-15-97

06-04-97

08-27-97

10-08-97

05-15-97

05-15-97 1

06-02-97

08-27-97

10-08-97

05-16-97

06-02-97

08-27-97

10-08-97

05-16-97

06-02-97

08-27-97

10-08-97

05-15-97

05-1 5-97 1>2

06-05-97

06-05-97 1>2

08-27-97

08-27-97 '

10-08-97

1 0-08-97 '

05-16-97

06-05-97

08-27-97

10-09-97

10-09-97

10-09-97

10-09-97

10-09-97

27.3

17.9

1.74

2.17

135

92.3

2.22

6.41

2.56

2.56

2.45

1.03

.45

1.36

1.26

.10

.18

28.6

19.0

1.25

2.68

177

177

108

108

5.20

5.20

8.10

8.10

-

~

Specific 

conductance, 

field

(uS/cm)

46.0

54.0

71.0

76

44.0

41.8

128

98.0

115

115

173

166

165

89.0

103

192

209

68.0

85.0

175

170

50.0

50.0

52.5

52.5

158

158

130

130

2.0

3.0

2.0

-

-

~

pH, Temperafield ture, 

(standard water 

units) (°C)

7.3

7.9

7.5

7.0

7.2

7.2

7.2

6.6

8.0

8.0

8.0

7.8

7.4

7.8

7.9

7.9

7.5

7.6

7.8

8.2

7.5

7.3

7.3

7.6

7.6

7.9

7.9

7.3

7.3

5.5

5.7

6.0

-

-

6.0

10.5

10.0

3.0

8.0

11.5

12.5

4.0

9.5

9.5

13.5

10.0

4.0

10.0

11.3

12.5

5.0

8.0

12.5

18.0

5.0

10.0

10.0

14.0

14.0

17.5

17.5

5.5

5.5

BLANKS

20

..

-

Hardness 

(mg/L as 

CaC03)

14

16

26

23

15

14

50

33

46

48

48

76

69

32

35

82

80

25

29

75

63

16

18

18

18

65

68

47

47

<10

<10

<10

<10

<10

<10

<10

Calcium 

(mg/L as 

Ca)

4.1

3.9

7.9

6.3

7.5

4.0

15

9.2

13

14

13

23

21

9.6

9.8

26

25

7.1

7.7

22

18

4.5

5.5

5.1

5.4

20

20

14

13

<1.0

<1.0

<1.0

<1.0

<1.0

<1.0

<1.0

<1.0

Magnesium 

(mg/L as 

Mg)

1.0

1.6

1.5

1.7

.9

.9

3.2

2.5

3.2

3.0

3.6

4.4

4.5

1.9

2.5

4.1

4.7

1.7

2.3

4.6

4.5

1.1

1.1

1.2

1.2

3.9

4.6

3.2

3.3

<.l

<.l

<.l

.2

.2

.1

.2

.3

Sodium 

(mg/L as

Na)

2.5

2.7

3.9

3.7

1.6

1.6

3.9

3.1

3.6

3.7

4.4

5.4

5.2

5.0

5.5

7.5

8.1

3.9

4.8

7.6

8.4

2.2

2.3

2.1

2.2

5.4

5.4

4.9

4.9

<.l

<.l

.4

-

-

_.

<.l

Sodium 

adsorption 

ratio

.3

.3

.3

.3

.1

.2

.2

.2

.2

.2

.3

.3

.3

.4

.4

.4

.4

.3

.4

.4

.5

.2

.2

.2

.2

.3

.3

.3

.3

-

-

--

-

-

--

'Replicate sample.

2Replicate sample analyzed by USGS National Water Quality Laboratory.

60 Streamflow and Water-Quality Characteristics in the Upper Tenmile Creek Watershed, Lewis and Clark County, West-Central Montana
Table 12. Field-measured parameters and concentrations of major ions and nutrients in streams in upper Tenmile Creek watershed, Montana 

(Continued)

Potassium, 

dissolved 

(mg/L as

K)

1.0

1.1

1.6

1.2

1.0

.9

1.5

1.1

1.9

1.7

2.1

2.8

2.6

.2

.0

.4

.5

.0

.1

2.1

2.7

1.2

.9

1.0

.9

1.6

1.6

1.6

1.6

<.l

<.l

.2

<j

Bicarbonate 

(mg/L as 

HCO3)

..

22

23

11

28

21

86

82

_

-

74

78

-

65

71

..

~

17

-

54

53

41

40

-

<5

<5

<5

Alkalinity 

(mg/L as 

CaCO3

9

12

18

19

10

9

23

18

43

43

48

71

67

28

32

61

64

22

29

53

58

12

-

14

-

44

44

34

33

<5

<5

<5

<5

Sulfate, 

dissolved 

(mg/L as 

S04)

11

8.6

13

15

8.6

8.7

32

25

13

13

12

12

14

14

15

30

36

6.8

7.2

8.7

15

8.4

8.8

8.7

8.1

26

27

23

23

<1.0

<1.0

<.!'°

<T.o

Chloride, ..,, 

.. , ' Fluonde, dissolved ,. , . 

, dissolved (mg/L as , ._ _,. 

v * (mg/L as F)

<1.0 <.10

<1.0 <.10

<1.0 <.10

1.3 <.10

<1.0 <.10

<1.0 <.10

<1.0 .59

<1.0 <.10

<1.0 <.10

<1.0 <.10

<1.0 <.10

1.0 <.10

1.3 <.10

<1.0 <.10

<1.0 <.10

<1.0 <.10

1.7 <.10

2.5 <.10

2.7 <.10

6.2 .12

7.7 .11

1.0 <.10

1.0 <.10

<1.0 <.10

.5 <.10

2.1 <.10

2.0 <.10

2.1 <.10

2.1 <.10

<1.0 <.10

<1.0 <.10

<1.0 <.10

<1.0 <.10

Nitrate, Nitrite, 

dissolved dissolved 

(mg/L as (mg/L as

N) N)

.03 <.01

<.01 <.01

<.01 <.01

<01 <.01

.02 <.01

.01 <.01

.02 <.01

.02 <.01

<.01 <.01

<.01 <.01

.04 <.01

.01 <.01

.05 <.01

<.01 <.01

<.01 <.01

<.01 <01

.02 <.01

<.01 <.01

.09 <.01

<.01 <.01

.02 <.01

.02 <.01

<.01

.01 <.01

<.01

<.01 <.01

<.01 <.01

<.01 <.01

<.01 <.01

BLANKS

<.01 <.01

<.01 <.01

.T01 .T01

<.01 <.01

Ammonia, 

dissolved 

(mg/L as N)

<.05

<.05

<.05

<.05

<.05

<.05

<.05

<.05

<.05

<.05

<.05

<.05

<.05

<.05

<.05

<.05

<.05

<.05

<.05

<.05

<.05

<.05

<.01

<.05

<.01

<.05

<.05

<.05

<.05

<.05

<.05

<.05

<.05

Phosphorus, 

total 

(mg/L as P)

.03

.03

.02

.02

.03

.03

.02

.03

.03

.03

.03

.03

.02

.07

.07

.07

.07

.05

.05

.10

.12

.04

<.01

.02

.03

.03

.03

.03

.03

<.01

<.01

.T01

<01

Phosphate, 

ortho, 

dissolved 

(mg/L as 

P04)

<.01

.01

<.01

<.01

<.01

<.01

<.01

<.01

<.01

<.01

.01

.01

<01

.04

.04

.05

.05

.02

.03

.04

.02

<.01

-

<.01

.01

.02

.01

.01

<.01

<.01

<.01

<.01

Site number 

(fig. 1)

25

28

29

31

32

34

TABLE 12 61
Table 13. Concentrations of trace elements and suspended sediment in streams in the upperTenmile Creek 

watershed, Montana

[Samples analyzed by Montana Tunnels Laboratory unless otherwise indicated. Shaded value indicates exceedances of 

human health standard, except for iron and manganese, which are standards for aesthetic purposes. Bold type indicates 

exceedance of chronic aquatic-life standard. Bold italics indicate acute aquatic-life standard also exceeded. Standards are ' 

shown in table 10. Identical sample dates indicate replicate samples analyzed to evaluate reproducibility of results. 

Abbreviations: inst., instantaneous; ug/L, micrograms per liter; mg/L, milligrams per liter; mm, millimeter; rec., recoverable. 

Symbols: <, less than; , no data. BLANKS are quality-control samples of deionized water]

Site 

number 

(fig. 1)

1

2

3

6

7

9

10

11

12

13

15

18

Date

08-25-97

10-06-97

05-14-97

06-03-97

05-14-97

06-03-97

08-25-97

10-06-97

05-14-97

06-03-97

08-25-97

10-06-97

06-03-97

08-25-97

10-06-97

08-25-97

05-14-97

05-16-97

06-03-97

08-25-97

10-07-97

06-03-97

08-25-97

10-07-97

05-14-97

08-26-97

10-07-97

05-16-97

06-04-97

08-26-97

10-07-97

Discharge, 

inst., 

(cubic feet 

per 

second)

0.53

.18

30.6

31.4

47.8

41.0

1.67

.91

10.9

17.4

.40

.80

26.5

.91

.30

.26

28.7

1.38

.92

.08

.10

94.2

4.11

3.57

106

.11

3.37

4.20

2.16

.25

.32

Aluminum, 

total rec. 

(ug/L as Al)

100

<100

760

360

770

370

<100

<100

480

310

<100

150

320

<100

<100

210

730

2,000

2,400

1,900

1,700

390

<100

140

770

<100 |

140

300

190 1

<100

<100

Arsenic, 

total rec.

(ug/L as 

As)

<3

<3

<3

<3

<3

<3

<3

<3

6

<3

7

3

<3

<3

<3

<3

<3

180

1 1

14

11

<3

8

5

8

 

5

9

6

Cadmium, 

total rec. 

(ug/L as 

Cd)

0.2

.2

.6

.2

.3

.2

<.l

< !

.2

<.l

<.l

< !

.2

<.l

< '

<1

.4

25

30

30

30

.6

1.8

1.7

1.1

\ '5

.4

[ 2.5

2.4

1.8

Cad- Chromium, mium, 

dissolved total rec.

(ug/L as (ug/L as 

Cd) Cr)

0.1 <1

.2 <1

.6 <1

.2 <1

.3 <1

.2 <1

<.l <1

<.l <1

.2 <1

<.l <1

<.l <1

<.l <1

.3 <1

<.l <1

<.l <1

<.l <1

.2 <1

21 <1

30 <1

30 <1

26 <1

.6 <1

1.8 <1

1.7 <1

1.0 <1

.4 <1

.3 <1

1.6 <1

I 5 <1

2.1 <1

1.8 <1

Copper, 

total rec. 

(ug/L as 

Cu)

12

<l

19

23

11

19

4

<l

9

21

3

16

16

3

<l

<1

29

240

420

310

270

19

10

37

26

150

430

53

49

9

6

Copper, 

dissolved

(ug/L as 

Cu)

5

<l

4

5

4

5

4

<!

4

4

5

2

7

1

<!

<1

5

210

410

320

250

9

8

7

7

120

210

16

30

6

6

Iron, 

total rec.

(ug/L as 

Fe)

100

70

420

160

460

170

110

80

270

220

70

140

250

250

100

100

1,100

1,600

630

420

430

230

140

170

590

3,100

730

430

320

80

30

62 Streamflow and Water-Quality Characteristics in the Upper Tenmile Creek Watershed, Lewis and Clark County, West-Central Montana
Table 13. Concentrations of trace elements and suspended sediment in streams in the upper Tenmile Creek 

watershed, Montana (Continued)

Lead, 

rec. 

Pb)

7

<3

6

<3

6

<3

<3

<3

7

<3

<3

<3

4

<3

<3

<3

7

52

SI

66

<3

7

6

15

<3

4

' ' '#1

13

5

<3

dissolvec

(ug/L as

<3

<3

<3

<3

<3

<3

<3

<3

<3

<3

<3

<3

5

<3

<3

<3

<3

W: 46

51 Jj - jjjm

<3

<3

<3

<3

<3

<3

I <3 SH&

<3

<3

<3

Manganese, 

1 total 

rec.

Mn)

13

12

42

19

37

14

<5

<5

10

12

<5

<5

34

27

11

<5

150

1,500

1 1,800

1 1,700

1 1,600

38

10

100

82

370

90

69

75

10

<5

MerNickel, 

cury, 

, total total 

rec. 

rec. , 

. _ (ug/L as "Si" «>

<0.6 <20

<.6 <20

<6 <20

<6 <20

<.6 <20

<.6 <20

<.6 <20

<.6 <20

<.6 <20

<.6 <20

<.6 <20

<.6 <20

5.« <20

<.6 <20

<.6 <20

<.6 <20

<.6 <20

<.6 <20

<.6 <20

<.6 <20

<6 <20

<.6 <20

<.6 <20

<.6 <20

<.6 <20

<.6 <20

<.6 <20

<.6 <20

<.6 <20

<.6 <20

<.6 <20

Selenium, Silver, 

total total rec 

rec. (Ug/L ai 

(ug/L Ag) 

asSe)

<1 <3

<1 <3

<3

<1 <3

<3

<1 <3

<1 <3

<1 <3

<3

<1 <3

<1 <3

<1 <3

<1 <3

<1 <3

<1 <3

<1 <3

<3

<3

3 <3

<1 <3

<1 <3

<1 <3

<1 <3

<1 <3

<3

<3

<1 <3

<3

<1 <3

<3

<1 <3

Zinc, 

total 

rec.

<100

<100

<100

<100

<100

<100

<100

<100

<100

<100

<100

<100

<100

<100

<100

<100

<100

2,300

3,700

3,000

3,200

120

460

440

220

<100

<100

300

700

380

400

Zinc, 

dissolved

<100

<100

<100

<100

<100

<100

<100

<100

<100

<10

<100

<100

<100

<100

<100

<100

<100

2,300

3,900

3,000

3,200

120

440

420

170

<100

<100

240

690

360

400

Sediment, 

suspended 

(mg/L)

4

3

27

8

29

8

2

2

9

13

2

4

7

2

2

6

70

150

7

1

3

9

11

4

29

10

7

19

10

2

Sediment, 

suspended 

sieve 

diameter 

< 0.062 mm 

(percent)

91

64

73

68

74

61

86

74

84

51

90

90

80

93

68

89

60

28

61

75

73

60

78

84

58

90

87

40

29

--

40

Site 

number 

(fig- 1)

1

2

3

6

7

9

10

11

12

13

15

18

TABLE 13 63
Table 13. Concentrations of trace elements and suspended sediment in streams in the upper Tenmile Creek

watershed, Montana (Continued)

Site 

number Date

(fig. 1)

20 05-16-97

06-04-97

08-26-97

10-07-97

22 05-15-97

06-04-97

08-26-97

10-07-97

23 05-15-97

06-04-97

08-26-97

08-26-971

10-07-97

25 05-15-97

06-02-97

08-27-97

10-08-97

28 05-15-97

06-04-97

08-27-97

10-08-97

29 05-15-97

05-15-97

06-02-97

08-27-97

10-08-97

31 05-16-97

06-02-97

08-27-97

10-08-97

32 05-16-97

06-02-97

08-27-97

10-08-97

34 05-15-97

05- 1 5-97 '-2

06-05-97

06-05-97 '-2

08-27-97

08-27-97 '

10-08-97

1 0-08-97 '

Discharge, 

inst., 

(cubic feet 

per 

second)

10.1

13.7

2.16

5.91

5.81

2.38

.29

.31

103

91.7

.39

.39

4.50

27.3

17.9

1.74

2.17

135

92.3

2.22

6.41

2.56

2.56

2.45

1.03

.45

1.36

1.26

.10

.18

28.6

19.0

1.25

2.68

177

177

108

108

5.20

5.20

8.10

8.10

Aluminum, 

total rec. 

(ug/L as Al)

300

450

120

130

850

500

120

120

670

540

1,200

1,200

310

600

540

210

120

680

470

120

180

380

200

150

<100

<100

970

700

290

<100

590

310

240

350

680

550

480

240

<100

<100

<100

<100

Arsenic, 

total rec.

(ug/L as 

As)

10

5

4

4

14

6

8

7

10

6

, 63 jf

4

3

<3

<3

17

9

"""W """"

27

<3

<3

<3

<3

<3

<3

<3

<3

<3

<3

<3

<3

<3

17

-

10

-

 

18

 

17

Cadmium, 

otal rec.

(ug/L as 

Cd)

.2

.2

.3

.4

1.8

1.8

1.6

1.5

1

1.2

m

3.4

2

1.1

1.8

1.5

1.3

1.1

2.8

2.8

<.

<.

<.

<.

<-

.3

<.l

<.l

<!

<.l

<.l

<.l

< >

1.1

1.0

1.0

<1

.9

.9

1.3

1.3

Cadmium, 

dissolved

(ug/L as 

Cd)

.2

.2

.2

.3

1

1.5

1.4

1.2

1.1

.9

27

27

3

2.1

1.2

1.6

1.3

1.3

.9

2.7

2.6

<.,

 C.I

<.l

<.l

<- 1

<j

<.l

<.l

< '

<.l

<.l

<.l

<l

.8

<]

.7

<1

.7

.7

1.1

1.1

Chro- Copper, 

mmm, ... 

, total rec. total rec. (ug/L as (Ug/Las ^u)

<1 25

<1 20

<1 87

<1 240

<\ 46

<\ 22

<1 19

<1 39

<1 200

<1 77

<1 57

<1 52

<1 770

1 31

<1 23

<1 17

<1 31

<1 42

<1 17

<\ 17

<\ 88

<1 14

<\ 12

<1 13

<\ 6

<1 <1

<1 14

<1 10

<1 7

<1 18

<l 21

<1 75

<1 10

<1 37

<1 57

<1 12

<1 12

<\ 8

<1 10

<1 13

<1 46

<1 43

Copper, 

dissolved

(ug/L as 

Cu)

16

15

14

130

14

IS

8

8

8

8

39

39

69

14

12

7

5

11

10

<\

37

1

1

3

<1

<l

3

77

<1

<l

7

5

<1

<!

6

9

9

7

2

<1

14

14

Iron, 

total rec.

(ug/L as 

Fe)

210

250

340

600

420

170

60

70

510

310

3,800

3,800

1,300

390

310

200

140

530

330

210

630

390

380

370

390

240

680

480

320

130

630

480

1,500

1,800

630

530

330

260

260

250

430

430

64 Streamflow and Water-Quality Characteristics in the Upper Tenmile Creek Watershed, Lewis and Clark County, West-Central Montana
Table 13. Concentrations of trace elements and suspended sediment in streams in the upper Tenmile Creek 

watershed, Montana (Continued)

Lead, 

, Lead, total .. ' dissolved 

rec. 

_ (Hg/L as

^Pb)"8 Pb)

10

3

<3

6

4

<3

<3

3

 PJT""'

 77

18

19

8

6

<3

<3

6

13

<3

8

6

6

4

<3

<3

<3

8

<3

<3

4

9

<3

<3

4

12

8

10

3

<3

<3

3

3

<3

<3

<3

<3

<3

<3

<3

<3

<3 

<3

5

4

<3

<3

<3

<3

<3

7

<3

<3

<3

<3

<3

<3

<3

<3

<3

<3

<3

4

<3

<3

<3

<3

<3

<1

<3

<1

<3

<3

<3

<3

Manganese, 

total 

rec.

(Hg/L as 

Mn)

15

12

34

64

69

16

6

9

70 

58

1,100

1,100

190

38

33

280

8

60

32

53

110

28

26

29

46

21

31

23

34

15

24

26

120

220

59

46

32

25

15

12

33

31

MerNickel, 

cury, " total total 

rec. 

rec. 

, (Hg/L as "X," 

<.6 <20

<.6 <20

<.6 <20

<.6 <20

<.6 <20

<.6 <20

<.6 <20

<.6 <20

<.6 <20 

<.6 <20

<.6 <20

<.6 <20

<.6 <20

<.6 <20

<.6 <20

<.6 <20

<6 <20

<.6 <20

<.6 <20

<.6 <20

<.6 <20

<.6 <20

<.6 <20

<.6 <20

<.6 <20

<.6 <20

<.6 <20

<.6 <20

<.6 <20

<.6 <20

<.6 <20

<.6 <20

<.6 <20

<.6 <20

<.6 <20

<.l 1

<.6 <20

<1 1

<.6 <20

<.6 <20

<.6 <20

<.6 <20

Selenium, Silver, 

total total rec. 

rec. (Hg/L as 

(ug/L Ag) 

asSe)

<3

<1 <3

<3

<1 <3

<3

<1 <3

<3

<1 <3

<3 

1 <3

<3

<3

<1 <3

<3

<1 <3

<3

<1 <3

<3

1 <3

<3

<1 <3

<3

<3

<1 <3

<3

<1 <3

<3

<1 <3

<3

<1 <3

<3

<1 10

<3

<1 <3

<3

<1

<1 <3

<1

<3

<3

<1 <3

<1 <3

Zinc, 

total 

rec.

(Hg/L as 

Zn)

<100

<100

<100

<100

210

170

130

150

160 

160

3,100

3,100

560

310

210

330

340

210

170

550

640

<100

<100

<100

<100

<100

<100

<100

<100

<100

<100

<100

100

<100

180

160

140

140

160

160

320

310

Zinc, 

dissolved

(|ig/L as 

Zn)

<100

<100

<100

<100

<100

120

140

130

160

140

3,000

3,200

500

270

200

290

290

180

170

540

570

<100

<100

100

<100

<100

<100

<100

<100

<100

<100

<100

<100

<100

120

140

130

140

140

160

310

290

Sediment, 

suspended 

(mg/L )

6

3

3

5

22

6

3

2

31

7

12

12

7

10

5

5

7

20

9

12

4

8

7

7

4

56

22

18

15

17

13

12

-

21

34

-

6

7

3

4

3

3

Sediment, 

suspended, 

sieve 

diameter 

< 0.062 mm 

(percent)

91

90

85

86

66

33

51

64

50

77

96

92

89

68

71

86

77

61

66

59

80

79

76

74

75

26

76

76

81

53

63

80

42

43

-

83

68

86

81

88

69

Site 

number 

(fig. 1)

20

22

23

25

28

29

31

32

34

TABLE 13 65
Table 13. Concentrations of trace elements and suspended sediment in streams in the upper Tenmile Creek 

watershed, Montana (Continued)

Site 

number 

(fig. 1)

Date

Discharge, 

inst, 

(cubic feet 

per

second)

Aluminum, 

total rec. 

(ug/L as Al)

Arsenic, 

total rec.

(ug/Las 

As)

Cad- Cad- Chromium, mium, mium, 

total rec. dissolved total rec.

(ug/L as (Ug/L as (ug/L as 

Cd) Cd) Cr)

Copper, 

total rec.

(ug/Las 

Cu)

Copper, 

dissolved

(ug/L as 

Cu)

Iron, 

total rec.

(ug/Las 

Fe)

BLANKS

- 05-16-97

06-05-97

08-27-97

10-09-97

10-09-97

10-09-97

10-09-97

10-09-97

~

~

~

~

~

~

--

--

<100

<100

<100

<100

<100

<100

<100

<100

<3

<3

<3

<3

<3

<3

<3

<3

<.

<.

<.

<.

<.

<.

<.

< 

<.l <1

<.l <1

<.l <1

<1

<1

<1

<1

<.l <1

3

1

<1

<1

<1

<1

<1

<1

<1

1

<1

-

-

-

~

<1

<10

<10

<10

<10

<10

<10

<10

<10

'Replicate sample.

2Replicate sample analyzed at USGS NationalWater Quality Laboratory.

66 Streamflow and Water-Quality Characteristics in the Upper Tenmile Creek Watershed, Lewis and Clark County, West-Central Montana
Table 13. Concentl'ations of trace elements and suspended sediment in streams in the upper Tenmile Creek 

watershed, Montana (Continued)

Lead, 

total

rec.

(ug/L as 

Pb)

Lead, 

dissolved

(fig/Las 

Pb)

Manganese, 

total

rec.

(ug/Las 

Mn)

Mercury, 

total

rec.

(ug/Las 

Hg)

Nickel, 

total

rec.

(ug/Las 

Ni)

Selenium, 

total

rec.

(Ug/L 

asSe)

Silver, 

total rec.

(ug/L as 

Ag)

Zinc, 

total

rec.

(ug/Las 

Zn)

Zinc, 

dissolved

(ug/Las 

Zn)

Sediment,

suspended 

(mg/L)

Sediment, 

suspended,

sieve 

diameter 

< 0.062 mm 

(percent)

Site

number 

(fig- 1)

BLANKS

<3

<3

<3

<3

<3

<3

<3

. <3

<3

<3

<3

-

--

--

--

<3

<5

<5

<5

<5

<5

<5

<5

<5

<.6

<.6

<.6

--

-

--

-

<.6

<20

<20

<20

<20

<20

<20

<20

<20

--

<1

-

<1

<1

<1

<1

<1

<3

<3

<3

<3

<3

<3

<3

<3

<100

<100

100

<100

<100

<100

100

<100

<100

<100

<100

--

--

--

-

<100

--

--

-

--

--

--

-

--

--

--

--

--

--

--

-

--

--

TABLE 13 67
Table 14. Trace-element concentrations in bottom sediment from Chessman Reservoir and an adjacent 

wetland in the upper Tenmile Creek watershed, compared to concentrations in bottom sediment from 

Lake Helena, Montana

[Samples collected September 8, 1997. Analyzes conducted by U.S. Geological Survey on sediment fraction finer than 

0.062 millimeter diameter. Symbol: <, less than]

Concentration, total in micrograms per gram of dry sample weight

_ . Chessman Reservoir Trace element

Arsenic

Cadmium

Chromium

Copper

Lead

Zinc

Site Rl

48

1.7

9.6

162

49

151

Site R2A

24

1

8

264

23

66

Site R2B

31

1.8

14.9

617

44

231

SiteR3

55

1.9

25.9

219

105

448

Site R4

30

1.3

14.6

228

34

167

Lake Helena 1

18-46

<2-4

43-47

47-82

38-170

200-600

1 Range of analyses from 3 sites (Kendy and others, 1998, p. 54)

68 Streamflow and Water-Quality Characteristics in the Upper Tenmile Creek Watershed, Lewis and Clark County, West-Central Montana
Table 15. Equations for calculating hardness-dependent aquatic-life criteria for trace elements

[Equations provide numerical standards in micrograms per liter (ug/L). Hardness used in equations is total hardness 

calculated from calcium and magnesium concentrations and expressed as milligrams per liter (mg/L) of CaCX^j. For 

samples having hardness less than 25 mg/L, Montana Department of Environmental Quality (1995) uses a hardness value 

of 25 mg/L for computing the standard. Symbol: , no standard; 6, base of natural logarithms, equal to 2.718]

Freshwater aquatic-life standard1 , in (ig/L

Trace element 

Acute toxicity Chronic toxicity

Cadmium e(1.128[ln(hardness)]-3.828) e(0.7852[ln(hardness)]-3.490)

Copper e(0.9422[ln(hardness)]-1.464) e(0.8545[ln(hardness)]-1.465)

Lead e(l. 273 [In(hardness)]-1.460) e(1.273[ln(hardness)]-4.705)

Nickel e(0.8460[ln(hardness)]+3.3612) e(0.8460[ln(hardness)]+1.1645)

Silver e(1.72[ln(hardness)]-6.52)

'U.S. Environmental Protection Agency (1986).

TABLE 15 69
Table 16. Calculated instantaneous loads of selected trace elements and suspended sediment in streams in the upper Tenmile 

Creek watershed, Montana

[Symbol: <, less than. Concentrations used to calculate loads are presented in table 13. For replicate samples, calculated loads are based on 

average concentrations for the replicate samples. Trace-element loads are total recoverable]

Calculated instantaneous load for indicated constituent, in pounds per day

Site no.

1

2

3

6

7

9

10

11

12

13

15

18

20

Date

08/25/97

10/06/97

05/14/97

06/03/97

05/14/97

06/03/97

08/25/97

10/06/97

05/14/97

06/03/97

08/25/97

10/06/97

06/03/97

08/25/97

10/06/97

08/25/97

05/14/97

05/16/97

06/03/97

08/25/97

10/07/97

06/03/97

08/25/97

10/07/97

05/14/97

08/26/97

10/07/97

05/16/97

06/04/97

08/26/97

10/07/97

05/16/97

06/04/97

08/26/97

10/07/97

Discharge, 

in cubic feet 

per second

0.53

.18

30.6

31.4

47.8

41.0

1.67

.91

10.9

17.4

.40

.80

26.5

.91

.30

.26

28.7

1.38

.92

.08

.10

94.2

4.11

3.57

106

.11

3.37

4.20

2.16

.25

.32

10.1

13.7

2.16

5.91

Aluminum

0.29

<.10

130

61

200

82

<.90

<.49

28

29

<.22

.65

46

<.49

<.16

.29

110

15

12

.82

.92

200

<2.2

2.7

440

<.06

2.5

6.8

2.2

<.13

<.17

16

33

1.4

4.1

Arsenic

<0.01

<.01

<.49

<.51

<.77

<.66

<.03

<.01

.35

<.28

.02

.01

<.43

<.01

<.01

<01

<.46

1.3

.05

.01

.01

<1.5

.18

.10

4.6

.01

.09

.61

.27

.01

.01

.55

.37

.05

.13

Cadmium

<0.01

<.01

.10

.03

.08

.04

<.01

<.01

.01

<.01

<.01

<.01

.03

<.01

<.01

<.01

.06

.19

.15

.01

.02

.31

.04

.03

.63

<.01

.01

.06

.07

<.01

<.01

.01

.01

<.01

.01

Copper

0.03

<.01

3.1

3.9

2.8

4.2

.04

<.01

.53

2.0

.01

.07

2.3

.01

<.01

<.01

4.5

1.8

2.1

.13

.15

9.7

.22

.71

15

.09

7.8

1.2

.57

.01

.01

1.4

1.5

1.0

7.7

Iron

0.29

.07

69

27

120

38

.99

.39

16

21

.15

.60

36

1.2

.16

.14

170

12

3.1

.18

.23

120

3.1

3.3

340

1.8

13

9.8

3.7

.11

.05

11

18

4.0

19

Lead

0.02

<.01

.99

<.51

1.5

<.66

<.03

<.01

.41

<.28

<.01

<.01

.57

<.01

<.01

<.01

1.1

1.0

.26

.03

.04

<1.5

.16

.12

8.6

<.01

.07

.75

.15

.01

<.01

.55

.22

<.03

.19

Manganese

0.04

.01

6.9

3.2

9.6

3.1

<.04

<.02

.59

1.1

<.01

<.02

4.9

.13

.02

<.o,

23

11

8.9

.73

.86

19

.22

1.9

47

.22

1.6

1.6

.87

.01

.01

.82

.89

.40

2.0

Suspended 

sediment

11.4

2.92

4,460

1,360

7,490

1,770

18.0

9.83

530

1,220

4.32

17.3

1,000

9.83

3.24

8.42

10,800

1,120

34.8

.43

1.62

4,580

244

77.1

16,600

5.94

127

431

117

0

3.46

327

222

35.0

160

70 Streamflow and Water-Quality Characteristics in the Upper Tenmile Creek Watershed, Lewis and Clark County, West-Central Montana
Table 16. Calculated instantaneous loads of selected trace elements and suspended sediment in streams in the upper Tenmile 

Creek watershed, Montana (Continued)

Calculated instantaneous load for indicated constituent, in pounds per day

Site no. Date

22 05/15/97

06/04/97

08/26/97

10/07/97

23 05/15/97

06/04/97

08/26/97

10/07/97

25 05/15/97

06/02/97

08/27/97

10/08/97

28 05/15/97

06/04/97

08/27/97

10/08/97

29 05/15/97

06/02/97

08/27/97

10/08/97

31 05/16/97

06/02/97

08/27/97

10/08/97

32 05/16/97

06/02/97

08/27/97

10/08/97

34 05/15/97

06/05/97

08/27/97

10/08/97

Discharge, 

in cubic feet 

per second

5.81

2.38

.29

.31

103

91.7

.39

4.50

27.3

17.9

1.74

2.17

135

92.3

2.22

6.41

2.56

2.45

1.03

.45

1.36

1.26

.10

.18

28.6

19.0

1.25

2.68

177

108

5.20

8.10

Aluminum

27

6.4

.19

.20

370

270

2.5

7.5

88

52

2.0

1.4

500

230

1.4

6.2

4.0

2.0

<.56

<.24

7.1

4.8

.16

<.10

91

32

1.6

5.1

590

210

<2.8

<4.4

Arsenic

.44

.08

.01

.01

5.6

3.0

.36

1.5

.59

.29

<.03

<04

12

4.5

.36

.93

<.04

<.04

<.02

<.01

<.02

<.02

<.01

<.01

<.46

<.31

<.02

<.04

16

5.8

.52

.79

Cadmium

.06

.02

<.01

<.01

.56

.59

.06

.08

.29

.11

.02

.02

.95

.55

.03

.10

<.01

<.01

<.01

<.01

<.01

<.01

<.01

<.01

.02

.01

<.01

<.01

1.0

.58

.03

.06

Copper

1.4

.28

.03

.07

110

5.4

.11

4.1

4.6

2.2

.16

.36

31

8.5

.20

3.0

.18

.17

.03

<.01

.10

.07

<.01

.02

3.2

1.5

.07

.54

30

5.8

.31

2.0

Iron

13

2.2

.09

.12

280

150

8.0

32

57

30

1.9

1.6

390

160

2.5

22

5.3

4.9

2.2

.58

5.0

3.3

.17

.13

97

49

10

26

550

170

7.1

19

Lead

.13

<.04

<.01

<.01

8.9

35

.04

.19

.88

<.29

<.03

.07

9.5

<1.5

.10

.21

.07

.04

<.02

<.01

.06

<.02

<.01

<.01

1.4

<.31

<.02

.06

10

4.1

<.08

<.13

Manganese

2.2

.21

.01

.02

39

29

2.3

4.6

5.6

3.2

2.6

.09

44

16

.64

3.7

.37

.38

.26

.05

.23

.16

.02

.01

3.7

2.7

.81

3.2

50

16

.38

1.4

Suspended 

sediment

690

71.}

4.70

3.35

17,200

3,470

25.3

170

1,470

483

47.0

82.0

14,600

4,490

144

138

111

92.6

22.2

136

162

122

8.10

16.5

2,010

1,230

0

304

32,500

3,500

98

131

TABLE 16 71
*?f?J Paifr^titian^ CHARACTERISTICS IN THE UPPER TENMILE CREEK WATERSHED, LEWIS AND CLARK COUNTY, WEST-CENTRAL M