U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2009–5059

Prepared in cooperation with South Dakota Game, Fish and Parks

Hydrologic Characterization for Spring Creek and 

Hydrologic Budget and Model Scenarios for Sheridan Lake, 

South Dakota, 1962–2007

Scientific Investigations Report 2009–5059
Front cover. Photograph of Spring Creek, looking downstream during extremely low flow condition on July 19, 2007, 

by Ron Koth, South Dakota Game, Fish and Parks.

Back cover. Upper left: Photograph of fisherman on Sheridan Lake, courtesy of South Dakota Game, Fish, and Parks.

Lower right: Photograph of marina on Sheridan Lake, courtesy of South Dakota Game, Fish, and Parks.
Hydrologic Characterization for Spring 

Creek and Hydrologic Budget and Model 

Scenarios for Sheridan Lake, South Dakota, 

1962–2007

By Daniel G. Driscoll and Parker A. Norton

Prepared in cooperation with South Dakota Game, Fish and Parks

Scientific Investigations Report 2009–5059

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2009

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reproduce any copyrighted materials contained within this report.

Suggested citation:

Driscoll, D.G., and Norton, P.A., 2009, Hydrologic characterization for Spring Creek and hydrologic budget and 

model scenarios for Sheridan Lake, South Dakota, 1962–2007: U.S. Geological Survey Scientific Investigations 

Report 2009–5059, 80 p.
iii

Contents

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

Introduction.....................................................................................................................................................2

Description of Study Area ............................................................................................................................2

Sheridan Lake and Dam.......................................................................................................................2

Hydrogeology and Climate ..................................................................................................................4

Hydrologic Budget Concepts and Characterization of Hydrologic Data..............................................5

Hydrologic Budget Concepts..............................................................................................................5

Availability of Hydrologic Data and Timeframes Considered........................................................6

Estimation and Characterization of Hydrologic Data......................................................................8

Streamflow....................................................................................................................................8

Extrapolation of Streamflow Data....................................................................................8

Characterization of Historical Streamflow Data for Spring Creek ...........................10

Monthly Flow Conditions ........................................................................................10

Low-Flow Conditions...............................................................................................10

Precipitation................................................................................................................................12

Evaporation.................................................................................................................................18

Hydrologic Budget for Sheridan Lake ......................................................................................................18

Long-Term Monthly Budget...............................................................................................................19

Short-Term Daily Budget ...................................................................................................................26

Hydrologic Model and Scenarios for Sheridan Lake.............................................................................29

Modeling Approach and Model Scenarios ....................................................................................29

Model Limitations................................................................................................................................32

Summary........................................................................................................................................................33

References Cited..........................................................................................................................................34

Appendix........................................................................................................................................................37

Figures

1. Map showing study area and locations of hydrologic data sites ........................................3

2. Graph showing annual mean streamflow for selected streamflowgaging stations..............................................................................................................................8

3. Boxplots for monthly and annual streamflow for Spring Creek above 

Sheridan Lake (station 06406920) for the actual period of record 

(water years 1991–2004) and extrapolated period (water years 1962–2006)....................12

4. Regression plots of monthly and annual streamflow for Spring Creek 

near Keystone (downstream station, 06407500) against Spring Creek 

above Sheridan Lake (upstream station, 06406920), water years 1991–2004 ...................13

5. Regression plot of monthly streamflow difference for Spring Creek stations 

(06407500 minus 06406920) against flow at upstream station (06406920), 

water years 1991–2004...............................................................................................................14

6. Graphs showing relations between computed reservoir outflow for 

Sheridan Lake and area-adjusted flow of Spring Creek for station 06407500, 

1986–2006 .....................................................................................................................................25
iv

7. Quantile plots showing distribution of monthly values of computed 

reservoir outflow from Sheridan Lake for pass-through operating system, 

1962–2006 .....................................................................................................................................27

8. Graph showing maximum drawdown by year for hypothetical release 

scenarios, 1962–2006 .................................................................................................................32

Tables

1. Site information for selected hydrologic data sites................................................................7

2. Annual mean streamflow and rank for selected streamflow-gaging stations...................9

3. Pearson’s correlation coefficients (r) for monthly and annual flows 

(water years 1991–2004) at Spring Creek above Sheridan Lake 

(station 06406920) and flows at three longer term gaging stations....................................11

4. Selected statistics for actual and extrapolated streamflow for Spring 

Creek above Sheridan Lake (station 06406920) .....................................................................11

5. Computed differences in monthly and annual streamflow for Spring Creek 

stations (06407500 minus 06406920), water years 1991–2004 ..............................................15

6. Low-flow statistics for Spring Creek near Keystone (station 06407500), 

water years 1987–2006...............................................................................................................16

7. Comparison of monthly mean and minimum daily flow values for Spring 

Creek near Keystone (station 06407500), water years 1987–2006 ......................................17

8. Results of linear least-squares regression between monthly pan evaporation 

at Pactola Dam and estimated monthly precipitation for Sheridan Lake for 

May and October, 1962–2006 ....................................................................................................18

9. Summary statistics for monthly pan evaporation data at Pactola Dam, 

1962–2006 .....................................................................................................................................19

10. Moving average maximum values and ranks for 1- through 7-day intervals 

for pan evaporation at Pactola Dam, 1962–2006 ...................................................................20

11. Summary of selected hydrologic budget components for Sheridan Lake, 

1962–2006 .....................................................................................................................................22

12. Monthly coefficients for effective precipitation and pan evaporation 

for Sheridan Lake........................................................................................................................22

13. Comparison of ranges in monthly lake evaporation for Sheridan Lake for 

selected pan coefficients..........................................................................................................23

14. Monthly differences between computed reservoir outflows and 

area-adjusted flow values for Spring Creek near Keystone 

(station 06407500), 1986–2006 ...................................................................................................24

15. Ranked monthly values of computed reservoir outflows from Sheridan 

Lake for pass-through operating system, 1962–2006............................................................26

16. Computations of lake evaporation for two low-flow periods during 2007 ........................28
v

17. Summary of selected output from hydrologic model for various release 

scenarios, 1962–2006 .................................................................................................................30

18. Monthly and annual streamflow data for Battle Creek near Keystone 

(station 06404000), water years 1962–2006.............................................................................38

19. Monthly and annual streamflow data for Spring Creek above Sheridan 

Lake (station 06406920), water years 1991–2004 ...................................................................39

20. Monthly and annual streamflow data for Spring Creek near Keystone 

(station 06407500), water years 1987–2006.............................................................................40

21. Monthly and annual streamflow data for Boxelder Creek near Nemo 

(station 06422500), water years 1967–2006.............................................................................40

22. Actual and extrapolated monthly and annual streamflow values for 

Spring Creek above Sheridan Lake (station 06406920), water 

years 1962–2006 ..........................................................................................................................42

23. Monthly and annual precipitation for Sheridan Lake, 1962–2006.......................................44

24. Pan evaporation data for Pactola Dam and other selected stations, 

1962–2006 .....................................................................................................................................46

25. Total monthly stream inflow to Sheridan Lake, 1962–2006 ..................................................55

26. Effective monthly precipitation on Sheridan Lake, 1962–2006............................................57

27. Monthly (May through October) evaporation from Sheridan Lake, 

1962–2006 .....................................................................................................................................59

28. Computed monthly net inflow to Sheridan Lake, 1962–2006 ...............................................61

29. Computed values of accumulated end-of-month storage change for 

zero-release scenario for Sheridan Lake,1962–2006............................................................63

30. Computed monthly values of reservoir outflow from Sheridan Lake for 

pass-through operating system, 1962–2006 ...........................................................................65

31. Computed values of accumulated end-of-month storage change for 

release scenario of 1.0 cubic foot per second, 1962–2006 ..................................................67

32. Computed values of accumulated end-of-month storage change for 

release scenario of 2.0 cubic feet per second, 1962–2006 ..................................................69

33. Computed values of accumulated end-of-month storage change for 

release scenario of 3.0 cubic feet per second, 1962–2006 ..................................................71

34. Computed values of accumulated end-of-month storage change for 

release scenario of 4.0 cubic feet per second, 1962–2006 ..................................................73

35. Computed values of accumulated end-of-month storage change for 

release scenario of 5.0 cubic feet per second, 1962–2006 ..................................................75

36. Computed values of accumulated end-of-month storage change for 

release scenario of 6.0 cubic feet per second, 1962–2006 ..................................................77

37. Computed values of accumulated end-of-month storage change for 

release scenario of 7.0 cubic feet per second, 1962–2006 ..................................................79
vi

Conversion Factors and Datums

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

inch (in.) 25.4 millimeter (mm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

acre 4,047 square meter (m2)

acre 0.4047 hectare (ha)

acre 0.4047 square hectometer (hm2) 

acre 0.004047 square kilometer (km2)

square foot (ft2) 929.0 square centimeter (cm2)

square foot (ft2) 0.09290 square meter (m2)

square mile (mi2) 259.0 hectare (ha)

square mile (mi2) 2.590 square kilometer (km2) 

Volume

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

acre-foot (acre-ft) 0.001233 cubic hectometer (hm3) 

cubic yard (yd3) 0.7646 cubic meter (m3)

Flow rate

acre-foot per day (acre-ft/d) 0.01427 cubic meter per second (m3/s)

acre-foot per year (acre-ft/yr) 1,233 cubic meter per year (m3/yr)

acre-foot per year (acre-ft/yr) 0.001233 cubic hectometer per year (hm3/yr)

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

inch per day (in/d) 0.6096 meter per hour (m/h)

Temperature in degrees Fahrenheit (°F) may be converted to degrees Celsius (°C) as follows:

°C=(°F-32)/1.8

Vertical coordinate information is referenced to the National Geodetic Vertical Datum of 1929 

(NGVD 29).

Horizontal coordinate information is referenced to the North American Datum of 1927 (NAD 27).

Altitude, as used in this report, refers to distance above the vertical datum.

Water year (WY) is the 12-month period, October 1 through September 30, and is designated by 

the calendar year in which it ends. Thus, the water year ending September 30, 2006, is called the 

“2006” water year.

Under the downstream order system for streamflow-gaging stations, station numbers increase 

in the downstream direction.
vii

Abbreviations and Acronyms

MOVE.1 maintenance of variance type I

NWS National Weather Service

r Pearson’s correlation coefficient

r

2 coefficient of determination

SDGF&P South Dakota Game, Fish and Parks

USFS U.S. Forest Service

USGS U.S. Geological Survey

WY water year

Hydrologic Characterization for Spring Creek and 

Hydrologic Budget and Model Scenarios for Sheridan 

Lake, South Dakota, 1962–2007

By Daniel G. Driscoll and Parker A. Norton

Abstract

The U.S. Geological Survey cooperated with South 

Dakota Game, Fish and Parks to characterize hydrologic 

information relevant to management of water resources 

associated with Sheridan Lake, which is formed by a dam on 

Spring Creek. This effort consisted primarily of characterization of hydrologic data for a base period of 1962 through 

2006, development of a hydrologic budget for Sheridan Lake 

for this timeframe, and development of an associated model 

for simulation of storage deficits and drawdown in Sheridan 

Lake for hypothetical release scenarios from the lake. Historically, the dam has been operated primarily as a “pass-through” 

system, in which unregulated outflows pass over the spillway; 

however, the dam recently was retrofitted with an improved 

control valve system that would allow controlled releases of 

about 7 cubic feet per second (ft3

/s) or less from a fixed depth 

of about 60 feet (ft). 

Development of a hydrologic budget for Sheridan Lake 

involved compilation, estimation, and characterization of data 

sets for streamflow, precipitation, and evaporation. The most 

critical data need was for extrapolation of available short-term 

streamflow records for Spring Creek to be used as the longterm inflow to Sheridan Lake. Available short-term records for 

water years (WY) 1991–2004 for a gaging station upstream 

from Sheridan Lake were extrapolated to WY 1962–2006 on 

the basis of correlations with streamflow records for a downstream station and for stations located along two adjacent 

streams. Comparisons of data for the two streamflow-gaging 

stations along Spring Creek indicated that tributary inflow is 

approximately proportional to the intervening drainage area, 

which was used as a means of estimating tributary inflow for 

the hydrologic budget. Analysis of evaporation data shows that 

sustained daily rates may exceed maximum monthly rates by a 

factor of about two.

A long-term (1962–2006) hydrologic budget was developed for computation of reservoir outflow from Sheridan Lake 

for the historical pass-through operating system. Two inflow 

components (stream inflow and precipitation) and one outflow 

component (evaporation) were considered. The hydrologic 

budget uses monthly time steps within a computational year 

that includes two 6-month periods—May through October, 

for which evaporation is accounted for, and November 

through April, when evaporation is considered negligible. 

Results indicate that monthly evaporation rates can substantially exceed inflow during low-flow periods, and potential 

exists for outflows to begin approaching zero-flow conditions 

substantially prior to the onset of zero-inflow conditions, 

especially when daily inflow and evaporation are considered. 

Results also indicate that September may be the month for 

greatest potential benefit for enhancing fish habitat and other 

ecosystem values in downstream reaches of Spring Creek with 

managed releases of cool water. Computed monthly outflows 

from Sheridan Lake for September are less than 1.0 ft3

/s for 8 

of the 44 years (18 percent) and are less than 2.0 ft3

/s for 14 of 

the 44 years (32 percent). Conversely, none of the computed 

outflows for May are less than 2.0 ft3

/s.

A short-term (July through September 2007) data set 

was used to calculate daily evaporation from Sheridan Lake 

and to evaluate the applicability of published pan coefficients. 

Computed values of pan coefficients of approximately 1.0 and 

1.1 for two low-flow periods are larger than the mean annual 

pan coefficient of 0.74 for the area that is reported in the 

literature; however, the computed values are consistent with 

pan coefficients reported elsewhere for similar late summer 

and early fall periods. Thus, these results supported the use of 

variable monthly pan coefficients for the long-term hydrologic 

budget.

A hydrologic model was developed using the primary 

components of the hydrologic budget and was used to simulate 

monthly storage deficits and drawdown for Sheridan Lake 

using hypothetical release scenarios of 1, 2, 3, 4, 5, 6, and 

7 ft3/s for the months May through October for 1962–2006. 

Five computational years (3 years that include 1987–90 and 

2 years that include 2004–06) tend to be “defining” years for 

purposes of drawdown considerations for Sheridan Lake. 

These 5 years include the only years with storage deficits for 

the historical pass-through operating condition (zero-release 

scenario). Computed drawdowns for 1987–90 approach 

or exceed 1 ft for many months for a prescribed release of 

1 ft3/s and approach or exceed 2 ft during many months for a 

prescribed release of 2 ft3

/s. For prescribed releases of 1 and 
2 Hydrologic Characterization for Spring Creek and Hydrologic Budget and Model Scenarios for Sheridan Lake, S. Dak.

2 ft3/s, the maximum computed drawdowns of 1.6 and 2.4 ft, 

respectively, occur in February of the 1988–89 computational 

year. For a prescribed release of 7 ft3/s, computed drawdown 

exceeds 12 ft for one-half of the months of the 1989–90 

computational year. During the 2004–05 and 2005–06 

computational years, storage deficits were computed for 16 of 

24 months for a prescribed release of 2 ft3/s. 

Computed storage deficits occur for 25 of 36 months 

during the 1987–90 computational years for a prescribed 

release of 1 ft3/s, as opposed to a combined total of only 

13 months with storage deficits for the other 41 years. For a 

prescribed release of 2 ft3/s, storage deficits are computed for 

60 months during 15 of the 44 years, and deficits exist for 22 

of the 24 months during the 1988–90 computational years. 

Computed storage deficits become progressively larger and 

more frequent for each of the progressively larger release 

scenarios.

for various recreational purposes, including fishing, boating, 

swimming, camping, and picnicking. Drawdown of Sheridan Lake below the spillway crest historically has occurred 

only when evaporation has exceeded inflows, and the limited 

occurrences of drawdown usually have not exceeded a few 

inches (Ron Koth, South Dakota Game, Fish and Parks, oral 

commun., 2008). Thus, most of the existing recreational 

infrastructure is not designed to accommodate large waterlevel fluctuations, which would provide a constraint for future 

potential management alternatives. 

In cooperation with SDGF&P, the U.S. Geological 

Survey (USGS) compiled and characterized hydrologic information relevant to management of water resources associated 

with Sheridan Lake. This effort included the development of 

a hydrologic model for use in simulating storage deficits and 

drawdown in Sheridan Lake for various release scenarios. 

The hydrologic model consists of a long-term (1962–2006) 

monthly hydrologic budget for Sheridan Lake that allows for 

optional release scenarios. The model output can be used in 

(1) evaluating the feasibility of management plans that would 

include alternatives for limited releases from Sheridan Lake, 

and (2) potential development of operating criteria.

The purposes of this report are to (1) characterize hydrologic data for Spring Creek and Sheridan Lake that are critical 

components of the hydrologic budget for Sheridan Lake (and 

downstream reaches of Spring Creek), (2) present a hydrologic budget for Sheridan Lake, and (3) present a summary 

of output from the hydrologic model of Sheridan Lake for 

various hypothetical release scenarios. Efforts consisted 

primarily of compilation and analysis of existing hydrologic 

data for 1962 through 2006; however, a short-term data set 

was collected during 2007 to facilitate computation of a daily 

hydrologic budget during a low inflow period. Inflow data for 

Sheridan Lake consist of measured streamflow records for 

1991–2004 and extrapolated monthly streamflow values for 

1962–90, which are based on correlations with records for 

other streamflow-gaging stations.

Description of Study Area

The study area includes the Spring Creek Basin and 

surrounding areas (fig. 1) in the Black Hills of western South 

Dakota. The primary focus is on Sheridan Lake and Spring 

Creek in the reach between streamflow-gaging stations 

06406920 and 06407500; however, available hydrologic data 

for various sites located considerable distances from Sheridan 

Lake were used for analyses described in this report.

Sheridan Lake and Dam

Sheridan Lake is formed by an earthen dam (575,000 cubic yards) on Spring Creek that was constructed in 1938–40 

by the Civilian Conservation Corps for recreational purposes, which remains the primary use today. An account 

Introduction

Sheridan Lake is located in the central Black Hills of 

western South Dakota (fig. 1) and is formed by a dam on 

Spring Creek. The dam was constructed in 1938–40 by the 

Civilian Conservation Corps for recreational purposes, which 

remains the primary use today. The dam, lake, and associated 

recreational facilities are on Federal lands managed by the 

U.S. Forest Service (USFS). Sheridan Lake has a surface area 

of about 383 acres and has a maximum depth of about 96 feet 

(ft) near the dam. Historically, the dam has been operated 

primarily as a “pass-through” system, in which unregulated 

outflows pass over the spillway. The dam recently was retrofitted with an improved control valve system that would allow 

controlled releases from a fixed depth of about 60 ft (South 

Dakota Game, Fish and Parks, 2005).

The fishery resource in Sheridan Lake and in Spring 

Creek downstream from the lake is managed by South Dakota 

Game, Fish and Parks (SDGF&P). SDGF&P has proposed 

collaborating with the USFS to manage future releases from 

Sheridan Lake to enhance fish habitat and other ecosystem values in downstream reaches of Spring Creek. Spring 

Creek is essentially perennial upstream from Sheridan Lake; 

however, low-flow conditions occasionally can approach 

zero flow (U.S. Geological Survey, 2008). Evaporation from 

Sheridan Lake can approach or exceed inflows during lowflow periods; thus, extended periods of zero-flow or extremely 

low-flow conditions can occur downstream from the dam, 

especially during prolonged drought periods. Warm water 

temperatures during low-flow conditions are detrimental to 

trout and other aquatic organisms in reaches of Spring Creek 

downstream from Sheridan Lake; thus, augmentation of downstream flow rates with relatively small quantities of cool water 

released at depth could benefit cold-water aquatic ecosystems.

Sheridan Lake is located very close to several population centers in the Black Hills area and is used extensively 
396170

396574

397567

391972 396427

Study area

SOUTH DAKOTA

390217

396304

Black Hills

0 4 20 4 8 MILES 2

8 KILOMETERS

Sheridan Lake drainage boundary

Continuous-record streamflow-gaging station  and number

Partial-record streamflow-gaging station and  number

Lake stage-measurement station and number

U.S. Geological Survey temporary precipitation  station and numberNational Weather Service precipitation station  and numberNational Weather Service pan evaporation  station and number

06407500

06407500

Rockerville

Keystone

06422500

Blackhawk

Rapid

Creek

MEADE COUNTY

LAWRENCE COUNTY

PENNINGTON COUNTY

CUSTER COUNTY

Piedmont

Nemo

Hill City

Custer

06404000

06406920

06406980

393868

06406950

06406960

440001103300200

06406960

396427

0640698006406980

396427396427

396427

395870

EXPLANATION

06406980

06406960

Creek

Fork

Rapid

North

Creek

Boxelder

PactolaReservoir

Sheridan Lake

Spring

Creek

Creek

Battle

Creek

Iron

Creek

Grace Cool di ge

 Deerfield Reservoir

a C ts Cel er ke

French

Creek

Spring

Creek

90

40

385

385

16

16

87

16

385

40

36

89

244

16

River

Missouri

River

Chey ne en

Base from U.S. Geological Survey digital dataUniversal Transverse Mercator projection,Zone 13

Harney

Peak x

Figure 1. Study area and locations of hydrologic data sites.

Introduction 3
The primary spillway is located just north of the dam on Sheridan Lake. 

Photograph by Ron Koth, South Dakota Game, Fish and Parks.

Sheridan Lake is formed by an earthen dam on Spring Creek. The secondary 

spillway is visible on the far side of the dam. Photograph by Ron Koth, South 

Dakota Game, Fish and Parks.

4 Hydrologic Characterization for Spring Creek and Hydrologic Budget and Model Scenarios for Sheridan Lake, S. Dak.

of construction details and history was provided by Powell 

(1940). The primary outlet consists of a concrete spillway 40 ft 

wide that is situated within a cut excavated through a bedrock 

slope located just north of the dam. A secondary spillway is 

located just south of the dam at an elevation slightly above 

the crest of the primary spillway. A 24-inch diameter pipe was 

emplaced in a tunnel about 60 ft below the primary spillway 

that was constructed by drilling and blasting through bedrock. 

The tunnel was used to divert the flow of Spring Creek during 

construction of the dam. During 2004, the pipe was retrofitted 

with a new valve system (South Dakota Game, Fish and Parks, 

2005) that would allow improved capability for low-flow 

releases of about 7 cubic feet per second (ft3/s) or less.

The dam, lake, and associated recreational facilities are 

on Federal lands managed by the USFS. Sheridan Lake has a 

surface area of about 383 acres at an altitude of about 4,624 ft, 

with a maximum depth of about 96 ft near the dam and a mean 

depth of about 30 ft (South Dakota Game, Fish and Parks, 

2005). The total storage volume of Sheridan Lake at full pool 

is about 11,500 acre-feet (acre-ft).

Historically, the dam has been operated primarily as a 

simple pass-through system, in which unregulated outflows 

are allowed to pass over the spillway. The primary spillway 

is fitted with a tainter gate that can provide 1.0 ft of additional storage above the spillway crest when closed. In 1961, 

the USFS made application to the State of South Dakota for 

(and subsequently was granted) a water right (No. 731–2) 

for storage of 1.0 ft of water above the spillway crest. Stored 

water occasionally was released by lifting the gate, which was 

used as a means of providing a single slug of water to downstream agricultural users. The water right was last exercised 

in 1991 and was cancelled in 2004 because of abandonment 

(Mark Rath, South Dakota Department of Environment and 

Natural Resources, written commun., 2008).

Releases of water from Sheridan Lake would obviously 

benefit downstream ecosystems during periods when zerooutflow conditions are approached. Benefits also could be 

derived from augmentation of downstream flow rates with 

relatively small quantities of cool water released at depth. 

Erickson (2002) provided a summary of available information 

regarding water temperatures and potential effects of releasing cool water. Cool water released from below a thermocline 

that typically develops (South Dakota Game, Fish and Parks, 

2005) could potentially affect in-lake water-quality dynamics. 

Water-quality information is available from various sources, 

including South Dakota Game, Fish and Parks (2005) and 

from total maximum daily load studies of Sheridan Lake and 

Spring Creek (South Dakota Department of Environment and 

Natural Resources, 2008).

Hydrogeology and Climate

Sheridan Lake is situated primarily on metamorphic rocks 

of Precambrian age (DeWitt and others, 1989), with schists 

being the most common rock type in the immediate vicinity of 

the lake. The majority of the Spring Creek drainage upstream 

from gaging station 06407500 (Spring Creek near Keystone) 

is within the “crystalline core” hydrogeologic setting identified 

by Driscoll and Carter (2001). Within this setting, streamflow 

generally is very responsive to precipitation and other climatic 

variables. However, a very small part of the headwater of the 

drainage is within the “limestone headwater” hydrogeologic 

setting. Within this setting, direct runoff is uncommon and 

streamflow is dominated by relatively stable springflow that 

originates from ground-water discharge.

Land-surface altitudes in the Spring Creek drainage 

range from 7,242 ft at Harney Peak to about 3,885 ft at gaging 
A 24-inch diameter pipe was emplaced in a tunnel about 60 feet below the primary spillway of Sheridan Lake. The pipe was retrofitted with a new valve system in 

2004 that would allow improved capability for low-flow releases of about 7 cubic feet per second or less. Photograph at left by Ron Koth, South Dakota Game, Fish 

and Parks; photograph at right courtesy of South Dakota Game, Fish and Parks.

The primary spillway is fitted with a tainter gate that can provide 1 foot of 

additional storage above the spillway crest when closed. Photograph by Ron 

Koth, South Dakota Game, Fish and Parks.

Hydrologic Budget Concepts and Characterization of Hydrologic Data 5

station 06407500 (Spring Creek near Keystone). Most of the 

drainage area is forested with ponderosa pine and is managed 

by the USFS (South Dakota Game, Fish and Parks, 2005). 

Mean annual precipitation generally increases with increasing 

altitude and from south to north (Driscoll and Carter, 2001) 

and ranges from about 19 to 23 inches in the study area. The 

mean annual temperature at Hill City is 41.9 degrees Fahrenheit (°F), and monthly means range from 21.5°F in January 

to 64.3°F in July (1971–2000; South Dakota State University, 

2008a). Ice generally forms on Sheridan Lake during November or December and is remains through most of March or into 

April.

Hydrologic Budget Concepts and 

Characterization of Hydrologic Data

Development of a long-term hydrologic budget was 

prerequisite to development of a hydrologic model for use 

in simulating potential release scenarios for management 

of Sheridan Lake. Concepts used in developing hydrologic 

budgets are described in this section. Characterizations of 

relevant hydrologic data sets, including streamflow, precipitation, and evaporation, also are provided.

Hydrologic Budget Concepts

All of the hydrologic budget applications presented in 

this report are based on the hydrologic continuity equation, 

which states that the sum of all inflows to a “control volume” 

is equal to the sum of all outflows, plus any changes in storage 

(Streeter and Wylie, 1979). The primary hydrologic budget 

application within this report was the development of a longterm monthly hydrologic budget for Sheridan Lake, for which 

the most basic equation is

	 Stream inflow + Precipitation = Evaporation + 

Reservoir outflow + ΔStorage, (1)

where

ΔStorage is change in storage, with a positive value 

indicating increased storage.

The largest variables in equation 1 are stream inflow and 

reservoir outflow, which generally are very similar because 

the reservoir is operated as a pass-through system. Stream 

inflow includes Spring Creek and several small tributaries that 
6 Hydrologic Characterization for Spring Creek and Hydrologic Budget and Model Scenarios for Sheridan Lake, S. Dak.

contribute directly to Sheridan Lake. Precipitation that falls 

directly on Sheridan Lake and evaporation also were considered, but these variables usually are relatively small, except 

during periods of low streamflow that are critical for potential 

management considerations.

Ground-water inflow and outflow (including seepage 

from the dam) were neglected in equation 1 because these 

variables generally are very small relative to other variables 

in the equation and also tend to be offsetting. Powell (1940) 

described extensive grouting efforts and noted that following construction of Sheridan Dam there was “... no apparent 

loss of water from the basin either by seepage to the tunnel 

or under the dam.” This general absence of seepage was 

confirmed by Dan Driscoll (USGS) and Ron Koth (SDGF&P) 

during a field inspection on July 19, 2007, when the lake 

elevation was just below the spillway crest, such that there 

was no discharge through the spillway. On that date, streamflow in the reach about one-half mile downstream from the 

dam was estimated as about 0.01 ft3/s. Farther downstream, 

zero-flow conditions were noted in many riffle sections, 

with several other riffle sections having minor flow of about 

0.01 ft3/s, or less. 

Several hydrologic budget applications involved comparisons of streamflow for two locations along Spring Creek. 

These comparisons were based on computations of downstream flow minus upstream flow, which provides a positive 

result for gaining flow. Similarly, all computations involving 

reservoir storage were done such that positive storage changes 

reflect an increase in storage.

Potential alternatives for reservoir operations would 

be restricted to a narrow range of water-level fluctuations. 

During discussions in public settings, SDGF&P has proposed 

that the maximum allowable drawdown would be limited to 

no more than about 2 ft below the spillway crest (Ron Koth, 

South Dakota Game, Fish and Parks, written commun., 2008). 

An existing bathymetric map (South Dakota Game, Fish and 

Parks, 2005) indicates extremely steep relief in the lakebed 

along almost all of the shoreline of Sheridan Lake. Thus, 

volumetric computations for Sheridan Lake were performed 

using a constant area of 383 acres, which neglected the 

minor changes in surface area associated with water-level 

fluctuations.

An initial hydrologic budget application involved development of a “historical” hydrologic budget using monthly 

time steps. Because a pass-through operating system typically 

has been used at Sheridan Lake, monthly changes in lake 

storage generally are very small, relative to other variables. 

Historically, several factors have potentially contributed to 

very minor variations in end-of-month lake storage, including (1) differences in hydraulic head above the spillway crest, 

(2) minor drawdown of the lake below the spillway crest 

during infrequent (and generally undocumented) periods when 

lake evaporation has exceeded inflows, and (3) occasional 

operation of the tainter gate, for which records of operations are not available. All changes in storage associated with 

these factors were considered negligible for the purpose of 

characterizing the long-term hydrologic budget for Sheridan 

Lake; however, for subsequent hydrologic budget applications 

involving simulation of release scenarios, changes in lake 

storage were accounted for.

Computations presented in this report commonly involve 

a volumetric unit of an acre-foot (acre-ft), which is 1 ft of 

water over an area of 1 acre (43,560 square ft). Flow rates 

(in cubic feet per second) averaged over time also commonly 

are used. An average flow rate of 1 ft3/s is equivalent to about 

1.98 acre-ft per day, 59.5 acre-ft per 30-day month, and 

724 acre-ft per year.

Availability of Hydrologic Data and Timeframes 

Considered

Development of a hydrologic budget for Sheridan Lake 

involved compilation and estimation of data sets for streamflow, precipitation, and evaporation. Table 1 provides selected 

information for all hydrologic data sites considered within this 

report, and locations of sites are shown in figure 1. Most of the 

data sets were collected prior to 2007; however, a short-term 

data set was collected during 2007 to facilitate computation of 

a daily hydrologic budget during a low-inflow period.

Selection of an appropriate timeframe for hydrologic 

budgeting was based primarily on availability of applicable 

streamflow data for estimation of stream inflow to Sheridan 

Lake. Streamflow records are available for two continuousrecord streamflow-gaging stations along Spring Creek—

above Sheridan Lake (station 06406920) and near Keystone 

(station 06407500). The downstream gaging station is 

located about 5 miles east (downstream) from Sheridan Lake 

(fig. 1). Periods of record for both stations are relatively short 

(table 1), and streamflow during these periods is not representative of long-term conditions, as indicated by comparisons 

with annual flow data (fig. 2 and table 2) for two nearby longer 

term continuous-record gaging stations (table 1, fig. 1) located 

along Battle Creek (station 06404000) and Boxelder Creek 

(station 06422500). Figure 2 shows that the available streamflow records for Spring Creek are primarily within periods 

of hydrologic extremes that have occurred over the substantially longer periods of record that are available for the two 

longer term stations. Table 2 includes the ranks (smallest to 

largest) of annual flows for each gaging station. Figure 2 and 

table 2 show that for the two longer term stations (1) many of 

the driest years of record occurred during water years (WY) 

1988–89 and 2002–06 and (2) many of the wettest years of 

record occurred during WY 1993–99.

For development of a long-term hydrologic budget for 

Sheridan Lake, monthly streamflow records for Spring Creek 

above Sheridan Lake (station 06406920) were extrapolated 

to a base period of WY 1962–2006. This corresponds with 

the period of available record for Battle Creek near Keystone 

(station 06404000), which is the longest viable period for 

which streamflow could be extrapolated. Methods used in 

extrapolating streamflow records for Spring Creek above 

Sheridan Lake are described in the following section.
Table 1. Site information for selected hydrologic data sites.

[Locations of sites are shown on figure 1. NGVD 29, National Geodetic Vertical Datum of 1929; ND, not determined; NA, not applicable]

Station number Station name

Latitude Longitude Period of 

record used

Drainage area 

(square miles)

Altitude (in feet 

above NGVD 29) (degrees, minutes, seconds)

Continuous-record streamflow-gaging stations

06404000 Battle Creek near Keystone 435221 1032010 1962–2006 58.5 NA

06406920 Spring Creek above Sheridan Lake 435739 1032918 1991–2004,

2007

127 NA

06407500 Spring Creek near Keystone 435843 1032048 1987–2006 163 NA

06422500 Boxelder Creek near Nemo 440838 1032716 1967–2006 96.0 NA

Partial-record streamflow-gaging stations

06406950 Horse Creek at Highway 385 near 

Hill City

435905 1032913 2007 ND NA

06406960 Sheridan Lake tributary near 

Calumet Ridge near Keystone

435751 1032735 2007 ND NA

Lake stage gage

06406980 Sheridan Lake near Hill City 435852 1032827 2007 NA NA

National Weather Service precipitation stations

393868 Hill City 435600 1033400 1962–2006 NA 4,980

395870 Mt. Rushmore National Memorial 435300 1032700 1962–2006 NA 5,250

396427 Pactola Dam 440400 1032900 1962–2006 NA 4,720

Short-term U.S. Geological Survey precipitation stations

06406960 Sheridan Lake tributary near 

Calumet Ridge near Keystone

435751 1032735 2007 NA 4,635

06406980 Sheridan Lake near Hill City 435852 1032827 2007 NA 4,624

440001103300200 Precipitation near Sheridan Lake 

near Hill City

440001 1033002 2007 NA 4,790

National Weather Service pan evaporation stations

396427 Pactola Dam 440400 1032900 1962–1974, 

1976,

1978–2006

NA 4,720

390217 Angostura Dam 432100 1032600 1962–2006 NA 3,140

396304 Oral 432400 1031600 1971–2006 NA 2,960

NA Angostura Dam/Oral (combined) NA NA 1962–2006 NA NA

391972 Cottonwood 435800 1015200 1962–2006 NA 2,414

397567 Shadehill Dam 454600 1021200 1966–76 NA 2,230

396170 Oahe Dam 442700 1002500 1962–2006 NA 1,660

396574 Pickstown 430400 983200 1962–2006 NA 1,490

Hydrologic Budget Concepts and Characterization of Hydrologic Data 7
Figure 2. Annual mean streamflow for selected streamflow-gaging stations.

1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010

WATER YEAR

0

10

20

30

40

50

60

70

06404000

06406920

06407500

06422500

STATION

ANNUAL MEAN STREAMFLOW, IN CUBIC FEET PER SECOND 

8 Hydrologic Characterization for Spring Creek and Hydrologic Budget and Model Scenarios for Sheridan Lake, S. Dak.

Estimation and Characterization of Hydrologic 

Data

Most of the available hydrologic data sets by themselves 

were not directly applicable for development of a hydrologic 

budget for Sheridan Lake because (1) the data-collection 

sites were not located at the exact locations where data were 

required or (2) the hydrologic records were incomplete during 

the WY 1962–2006 base period. Thus, it was necessary to estimate some of the hydrologic variables. This section provides 

details regarding approaches used in estimating hydrologic 

data sets and also provides characterizations of relevant data 

for streamflow, precipitation, and evaporation.

Streamflow

Hydrologic budget and model applications involved 

extensive consideration of streamflow records for the two 

gaging stations along Spring Creek (06406920 and 06407500). 

This section of the report describes approaches used to 

extrapolate monthly streamflow records for station 06406920 

and provides selected characterizations of historical streamflow data for both stations. Extrapolation of records for 

station 06406920 also involved utilization of streamflow 

data for Battle Creek (station 06404000) and Boxelder Creek 

(station 06422500). Monthly records for all four of these 

stations (table 1) are presented in tables 18–21 in the Appendix. Available streamflow data were compiled from the USGS 

National Water Information System database (U.S. Geological 

Survey, 2008).

Extrapolation of Streamflow Data

Extrapolation of the monthly flow record for Spring 

Creek above Sheridan Lake (station 06406920) to a timeframe 

of WY 1962–2006 was based on relations with records for the 

three other continuous-record gaging stations listed in table 1. 

Pearson’s correlation coefficients (r) (Helsel and Hirsch, 1992) 

for linear correlation of monthly flows (WY 1991–2004) 

between Spring Creek above Sheridan Lake and the other 

three stations are strong, with r values generally greater than 

0.90 and always 0.80 or greater (table 3). Thus, the three other 

stations are suitable for use as index stations for extrapolation of monthly flow records for Spring Creek above Sheridan 

Lake. Correlations with the other Spring Creek station that is 

downstream from Sheridan Lake (06407500) are especially 

strong (r = 0.98–0.99). Correlations with annual flows are 

greater than or equal to 0.96 for all three stations.

Extrapolation of the monthly flow record for Spring 

Creek above Sheridan Lake was accomplished using a 

“mixed-station” procedure described by Alley and Burns 

(1983). This procedure is based on the use of multiple potential index stations and the use of a maintenance of variance 

type I (MOVE.1) straight-line fitting procedure rather than 

an ordinary least-squares straight-line fitting procedure. The 

MOVE.1 procedure is analogous to ordinary least-squares 

regression, but results in an extended record with a variance 

comparable to that of the unextended record (Cary and Parrett, 

1996).

The extrapolated monthly and annual values for 

station 06406920 are shown in table 22 in the Appendix. The 

mean standard error of prediction for the MOVE.1 procedure 
Table 2. Annual mean streamflow and rank for selected streamflow-gaging stations.—Continued

[ft3/s, cubic feet per second; --, no data or not applicable]

Water year

06404000 06406920 06407500 06422500

Battle Creek near Keystone Spring Creek above Sheridan 

Lake Spring Creek near Keystone Boxelder Creek near Nemo

Annual mean 

(ft3/s) Rank Annual mean (ft3/s) Rank Annual mean (ft3/s) Rank Annual mean (ft3/s) Rank

1962 14.20 34 -- -- -- -- -- --

1963 15.00 36 -- -- -- -- -- --

1964 7.90 27 -- -- -- -- -- --

1965 19.50 41 -- -- -- -- -- --

1966 3.79 12 -- -- -- -- -- --

1967 15.30 38 -- -- -- -- 27.70 33

1968 4.01 14 -- -- -- -- 8.70 15

1969 5.80 20 -- -- -- -- 8.55 14

1970 6.83 23 -- -- -- -- 22.10 29

1971 15.80 39 -- -- -- -- 27.90 34

1972 21.10 42 -- -- -- -- 55.10 38

1973 8.61 29 -- -- -- -- 17.90 23

1974 1.65 5 -- -- -- -- 5.98 9

1975 4.58 16 -- -- -- -- 15.20 22

1976 13.20 33 -- -- -- -- 20.70 26

1977 2.78 9 -- -- -- -- 18.70 25

1978 11.90 31 -- -- -- -- 22.00 28

1979 6.00 21 -- -- -- -- 7.99 12

1980 2.48 8 -- -- -- -- 5.40 6

1981 5.79 19 -- -- -- -- 4.14 4

1982 6.38 22 -- -- -- -- 10.80 18

1983 3.98 13 -- -- -- -- 24.50 32

1984 8.65 30 -- -- -- -- 23.20 30

1985 1.11 4 -- -- -- -- 6.61 10

1986 5.05 18 -- -- -- -- 12.30 19

1987 6.84 24 -- -- 12.40 10 10.20 17

1988 .69 1 -- -- 1.80 2 4.61 5

1989 1.02 2 -- -- .98 1 3.81 3

1990 8.32 28 -- -- 8.69 8 5.62 7

1991 16.70 40 22.50 8 28.00 14 13.50 21

1992 3.50 11 6.06 2 7.46 7 6.88 11

1993 15.10 37 24.90 9 34.40 15 24.00 31

1994 5.03 17 11.70 6 13.30 11 18.50 24

1995 27.70 45 38.70 12 58.30 18 51.40 37

1996 14.40 35 30.10 10 40.90 17 42.90 36

1997 23.70 43 45.20 13 59.50 19 63.10 40

1998 12.90 32 30.30 11 35.00 16 34.90 35

1999 26.80 44 50.70 14 64.70 20 56.30 39

2000 7.29 25 13.00 7 16.50 13 21.70 27

Hydrologic Budget Concepts and Characterization of Hydrologic Data 9
Table 2. Annual mean streamflow and rank for selected streamflow-gaging stations.—Continued

[ft3/s, cubic feet per second; --, no data or not applicable]

Water year

06404000 06406920 06407500 06422500

Battle Creek near Keystone Spring Creek above Sheridan 

Lake Spring Creek near Keystone Boxelder Creek near Nemo

Annual mean 

(ft3/s) Rank Annual mean (ft3/s) Rank Annual mean (ft3/s) Rank Annual mean (ft3/s) Rank

2001 7.58 26 10.80 5 13.70 12 12.60 20

2002 3.04 10 6.81 3 7.45 6 5.77 8

2003 4.24 15 8.92 4 10.40 9 8.90 16

2004 1.06 3 2.80 1 2.87 5 3.74 2

2005 2.45 7 -- -- 2.73 3 3.46 1

2006 1.95 6 -- -- 2.85 4 8.43 13

Count 45 -- 14 -- 20 -- 40 --

10 Hydrologic Characterization for Spring Creek and Hydrologic Budget and Model Scenarios for Sheridan Lake, S. Dak.

applied to Spring Creek above Sheridan Lake was small 

(35.8 percent), which indicates generally reliable estimates 

for the extrapolated monthly flow records. A comparison 

of selected statistics for monthly and annual flows for the 

actual period of record (WY 1991–2004) and extrapolated 

period (WY 1962–2006) is presented in table 4, and a graphical comparison is shown in figure 3. The mean monthly and 

annual values and all of the percentile values are larger for the 

actual period of record than for the extrapolated period, which 

indicates that the short-term record is biased by especially 

large streamflow that occurred during the 1990s.

Characterization of Historical Streamflow Data for Spring 

Creek

This section provides a characterization of historical streamflow data for Spring Creek above Sheridan Lake 

(station 06406920) and near Keystone (station 06407500). 

This characterization provides useful insights regarding hydrologic conditions in the reach between the two stations and is 

used in development of approaches for the hydrologic budget.

Monthly Flow Conditions

Primary hydrologic influences in the reach along Spring 

Creek between stations 06406920 and 06407500 are evaporation from Sheridan Lake, evapotranspiration along Spring 

Creek, and ungaged tributary inflows. Tributary inflows in 

this reach can be characterized by examination of monthly 

flow data. Graphs showing flow at the downstream station 

(06407500) as a function of the upstream station (06406920) 

for monthly values and for annual values for WY 1991–2004 

are presented in figure 4. The slopes of the regression lines 

for monthly and annual flow are 1.39 and 1.36, respectively, 

which correspond closely with the ratio (1.28) of the drainage areas for the downstream and upstream stations (163 

and 127 square miles (mi2), respectively). This indicates that 

tributary inflows to the intervening reach (which includes 

Sheridan Lake) are approximately proportional to drainage 

area. The y-intercepts for both graphs are slightly negative, 

which is consistent with evaporation from Sheridan Lake and 

evapotranspiration along the reach from Sheridan Lake to the 

downstream station during low-flow conditions.

Figure 5 shows a regression plot of monthly streamflow 

differences between the two Spring Creek gaging stations as a 

function of flow at the upstream station. The monthly differences were computed as downstream minus upstream; thus, 

positive values indicate a gain, and negative values indicate a 

loss in the intervening reach. The graph shows that combined 

effects of lake evaporation and evapotranspiration along the 

stream reach can exceed tributary inflows during low-flow 

periods. The negative y-intercept (-2.05) is again consistent 

with effects of evaporation and evapotranspiration during 

low-flow conditions. Computed monthly differences between 

the two gaging stations are provided in table 5. The majority 

of the negative values for summer and fall months occurred 

during WY 2002–04, which were dominated by especially 

dry climatic conditions. Streamflow records for both gaging 

stations can be highly affected by substantial channel icing; 

thus, uncertainties regarding streamflow records are greater for 

winter months than for other months.

Low-Flow Conditions

Low-flow statistics (that is, the lowest mean streamflow 

that occurred during each year for selected numbers of consecutive days) for Spring Creek near Keystone (station 06407500) 

are presented in table 6. These statistics indicate that many 

short and extended periods of flow conditions that could be 

detrimental to trout and other aquatic organisms have occurred 

during the period of record (WY 1987–2006), especially 

during the particularly dry conditions of the late 1980s and 

early to mid-2000s. These data are not necessarily representative of long-term conditions, however, because of the shortterm nature of the data set.
Table 3. Pearson’s correlation coefficients (r) for monthly and annual flows (water years 1991–2004) at Spring Creek above Sheridan 

Lake (station 06406920) and flows at three longer term gaging stations.

Station

Month

Annual

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

Battle Creek 

near Keystone 

(06404000)

0.89 0.97 0.97 0.85 0.81 0.84 0.93 0.93 0.93 0.88 0.89 0.96 0.96

Spring Creek 

near Keystone 

(06407500)

.99 .99 .99 .99 .99 .98 .99 .99 .99 .98 .99 .99 .99

Boxelder Creek 

near Nemo 

(06422500)

.95 .97 .94 .93 .94 .82 .80 .91 .95 .95 .96 .94 .96

Table 4. Selected statistics for actual and extrapolated streamflow for Spring Creek above Sheridan Lake (station 06406920).

Statistic

Streamflow, in cubic feet per second

Month

Annual

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

Water years 1991–2004 (actual period of record)

Mean 10.90 11.30 8.19 5.74 6.20 11.60 20.96 55.23 72.04 28.46 17.33 10.77 21.61

Maximum 35.80 51.20 34.80 21.90 19.20 21.80 64.20 144.50 184.70 63.30 50.10 26.20 50.72

75th percentile 15.75 12.00 9.49 6.01 8.47 15.93 23.13 86.23 121.28 50.23 22.80 16.50 30.25

50th percentile 6.86 6.51 4.50 3.42 3.63 9.07 16.75 34.40 58.10 26.95 12.65 6.79 17.75

25th percentile 4.42 3.86 2.62 1.99 2.36 7.24 11.23 21.03 15.10 6.62 4.37 3.55 9.40

Minimum 2.59 2.37 1.62 1.01 1.21 4.66 5.38 4.12 2.21 2.92 2.19 1.32 2.80

Standard 

deviation

9.32 12.94 9.05 6.06 5.32 6.14 15.85 44.51 64.54 22.60 15.42 8.96 15.48

Water years 1962–2006 (extrapolated period)

Mean 7.55 6.35 4.16 2.98 3.31 8.65 16.33 37.64 64.15 23.21 12.92 7.15 16.23

Maximum 35.80 51.20 34.80 21.90 19.20 21.80 64.20 144.50 363.03 95.81 50.10 26.20 50.72

75th percentile 8.94 6.46 4.05 3.08 3.22 10.66 19.73 53.49 110.35 31.50 15.05 8.88 24.90

50th percentile 5.92 4.99 2.83 2.00 2.39 7.91 12.69 27.30 27.52 12.52 11.77 5.91 11.69

25th percentile 3.00 3.32 1.62 1.20 1.60 5.43 8.94 7.98 8.94 5.75 5.01 2.82 6.95

Minimum .00 .02 .07 .00 .02 1.08 2.83 3.01 1.45 .14 .04 .07 1.55

Standard 

deviation

6.57 8.17 5.86 3.94 3.67 5.04 12.09 36.85 76.41 21.51 10.57 6.29 12.65

Hydrologic Budget Concepts and Characterization of Hydrologic Data 11
0.01

0.1

1

10

100

1,000

14 45 14 45 14 45 14 45 14 45 14 45 14 45 14 45 14 45 14 45 14 45 14 45 14 45

45 Number of values 

Extrapolated

Actual

Streamflow

EXPLANATION 

90th percentile

10th percentile

75th percentile

Median

25th percentile

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

STREAMFLO

W, IN CUBIC FEET PER SECOND

Figure 3. Boxplots for monthly and annual streamflow for Spring Creek above Sheridan Lake (station 06406920) for the actual 

period of record (water years 1991–2004) and extrapolated period (water years 1962–2006).

12 Hydrologic Characterization for Spring Creek and Hydrologic Budget and Model Scenarios for Sheridan Lake, S. Dak.

Table 7 provides a comparison between the monthly 

mean flow and minimum daily flow for each month for Spring 

Creek near Keystone (station 06407500) for WY 1987–2006. 

This table shows that the monthly means are not necessarily indicative of when short-term, low-flow conditions can 

develop that might be critical to maintaining fish populations. 

The months of July through September for WY 2002–05 

provide several excellent examples.

Precipitation

Monthly precipitation for the WY 1962–2006 base 

period for Sheridan Lake was estimated primarily by averaging monthly precipitation values for three National Weather 

Service (NWS) stations (table 1) located approximately 

equidistant from Sheridan Lake (fig. 1). The monthly precipitation data for these three NWS “source” stations were 

obtained from South Dakota State University (2008b). The 

estimated monthly values for Sheridan Lake and a statistical 

summary are provided in table 23 in the Appendix. Monthly 

values were missing for 20 months of the base period for 

one of the NWS source stations. For 18 of the 20 months, 

precipitation estimates for the missing source station were 

obtained from estimated data tabulated by Driscoll and others 

(2000), and values for Sheridan Lake could then be derived by 

averaging the precipitation for all three stations. For 2 of the 

20 months, estimates for the missing source station were not 

available from Driscoll and others (2000), and the values for 

Sheridan Lake were derived by averaging the data available 

for the other two source stations.
Figure 4. Regression plots of monthly and annual streamflow for Spring Creek near Keystone 

(downstream station, 06407500) against Spring Creek above Sheridan Lake (upstream station, 

06406920), water years 1991–2004.

B Annual streamflow

A Monthly streamflow

0

0

y = 1.36x – 1.33

r

2

 = 0.98

–50

0

50

100

150

200

250

300

350

0 20 40 60 80 100 120 140 160 180 200

STREAMFLOW AT DOWNSTREAM STATION, IN CUBIC FEET PER SECOND

10

20

30

40

50

60

70

80

10 20 30 40 50 60

STREAMFLOW AT DOWNSTREAM STATION, IN CUBIC FEET PER SECOND

STREAMFLOW AT UPSTREAM STATION, IN CUBIC FEET PER SECOND

STREAMFLOW AT UPSTREAM STATION, IN CUBIC FEET PER SECOND

y = 1.39x – 2.05

r

2

 = 0.98

Hydrologic Budget Concepts and Characterization of Hydrologic Data 13
Figure 5. Regression plot of monthly streamflow difference for Spring Creek stations (06407500 minus 06406920) against flow at 

upstream station (06406920), water years 1991–2004.

–10

0

10

20

30

40

50

60

70

80

90

100

110

120

0 20 40 60 80 100 120 140 160 180 200

DIFFERENCE IN STREAMFLOW BETWEEN THE DOWNSTREAM AND 

UPSTREAM STATIONS, IN CUBIC FEET PER SECOND 

FLOW AT UPSTREAM STATION, IN CUBIC FEET PER SECOND 

y = 0.39x – 2.05

r

2

 = 0.81

14 Hydrologic Characterization for Spring Creek and Hydrologic Budget and Model Scenarios for Sheridan Lake, S. Dak.
Table 5. Computed differences in monthly and annual streamflow for Spring Creek stations (06407500 minus 06406920), water 

years 1991–2004.

[Computed difference is downstream minus upstream. Thus, positive values indicate a gain in the intervening reach, and negative values indicate a loss]

Water year/

statistic

Streamflow, in cubic feet per second

Month

Annual

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

1991 -0.74 -0.04 -0.34 -0.84 1.18 0.97 4.70 10.70 25.50 17.10 7.40 0.13 5.50

1992 .90 .71 .91 2.07 2.18 3.78 1.47 .85 2.16 2.50 .20 -.89 1.40

1993 -1.51 .82 1.07 1.33 1.34 1.82 4.30 25.90 38.30 25.50 9.70 4.80 9.50

1994 3.80 -1.10 -2.77 1.02 .40 3.00 3.80 6.80 4.00 .06 -.13 .16 1.60

1995 2.81 3.31 1.91 1.28 .71 4.05 1.61 66.10 107.70 36.80 7.20 1.90 19.60

1996 3.50 7.01 4.35 2.47 2.41 5.40 7.10 16.20 69.20 7.50 2.10 2.70 10.80

1997 4.90 6.20 1.90 3.70 1.80 2.50 3.90 55.80 55.20 11.90 16.90 6.30 14.30

1998 8.70 1.40 1.32 .90 .43 1.90 4.70 4.30 8.60 15.80 6.60 1.10 4.70

1999 6.30 12.60 8.80 7.80 3.40 3.40 12.70 29.10 37.70 29.00 13.30 3.40 14.00

2000 1.10 1.50 1.49 1.01 1.30 2.90 9.00 14.20 6.80 4.19 .06 -1.48 3.50

2001 .78 2.42 1.72 1.34 1.37 2.59 4.40 4.60 6.90 5.30 1.80 .92 2.90

2002 -1.00 -.49 .58 .88 .97 1.29 3.70 4.30 1.10 -.54 -2.17 -.79 .64

2003 .01 .17 .47 1.09 1.47 4.96 -.90 7.40 4.90 1.35 -2.17 -1.76 1.48

2004 -1.08 -.55 .16 .96 1.54 2.76 .76 .98 .10 -1.70 -1.72 -1.29 .07

Statistical summary

Mean 2.03 2.43 1.54 1.79 1.46 2.95 4.37 17.66 26.30 11.05 4.22 1.09 6.43

Maximum 8.70 12.60 8.80 7.80 3.40 5.40 12.70 66.10 107.70 36.80 16.90 6.30 19.60

75th percentile 3.73 3.09 1.86 1.89 1.74 3.69 4.70 23.48 38.15 16.78 7.35 2.50 10.48

50th percentile 1.00 1.11 1.20 1.19 1.36 2.83 4.10 9.05 7.75 6.40 1.95 .54 4.10

25th percentile -.55 .01 .50 .97 1.02 2.05 2.13 4.38 4.23 1.64 -.08 -.87 1.51

Minimum -1.51 -1.10 -2.77 -.84 .40 .97 -.90 .85 .10 -1.70 -2.17 -1.76 .07

Standard 

deviation

3.08 3.80 2.60 2.00 .80 1.29 3.47 20.33 32.23 12.19 6.06 2.47 6.16

Hydrologic Budget Concepts and Characterization of Hydrologic Data 15
Table 6. Low-flow statistics for Spring Creek near Keystone (station 06407500), water years 1987–2006.

[ft3/s, cubic feet per second]

Water 

year

Number of consecutive days

1 3 7 14 30 60 90 120 183

Flow 

(ft3/s) Rank Flow (ft3/s) Rank Flow (ft3/s) Rank Flow (ft3/s) Rank Flow (ft3/s) Rank Flow (ft3/s) Rank Flow (ft3/s) Rank Flow (ft3/s) Rank Flow (ft3/s) Rank

1987 0.06 6 0.06 6 0.08 6 0.11 6 0.74 7 2.03 8 3.88 12 5.15 11 10.30 141988 .00 1 .00 1 .00 1 .00 1 .00 1 .01 3 .02 1 .25 3 1.07 31989 .00 2 .00 2 .00 2 .00 2 .00 2 .00 2 .03 2 .04 1 .17 11990 .27 7 .27 7 .29 7 .30 7 .36 6 .68 6 .86 6 .93 5 1.33 41991 .51 9 .58 10 .83 11 1.16 10 1.56 11 1.75 7 2.00 7 2.17 7 3.10 71992 .76 12 .86 12 1.02 12 1.30 12 2.81 14 4.71 15 5.22 15 5.67 14 6.70 121993 .55 10 .56 9 .60 9 .97 9 1.45 9 2.34 12 2.44 8 2.61 8 4.31 81994 .97 13 .99 13 1.12 13 1.40 13 1.53 10 2.18 9 3.41 11 6.88 15 11.50 151995 1.60 15 1.73 15 2.80 15 3.75 16 4.16 15 4.58 14 5.03 13 5.58 13 7.38 131996 3.10 17 3.37 17 4.03 18 4.60 18 6.69 18 8.32 18 9.53 18 11.00 18 13.60 171997 8.60 19 9.00 19 10.30 19 13.10 19 15.10 19 16.40 19 17.80 19 19.90 19 22.70 191998 3.10 18 3.40 18 3.73 17 3.83 17 5.89 17 6.87 17 7.85 17 7.99 16 15.00 181999 17.00 20 17.70 20 18.40 20 19.60 20 20.70 20 23.30 20 25.60 20 28.50 20 37.70 202000 1.20 14 1.37 14 1.40 14 1.49 14 1.71 12 2.92 13 6.27 16 10.20 17 12.40 162001 1.90 16 2.33 16 2.99 16 3.70 15 4.42 16 4.78 16 5.06 14 5.39 12 6.62 112002 .35 8 .39 8 .50 8 .67 8 1.07 8 2.27 10 3.22 10 3.86 10 4.88 92003 .58 11 .60 11 .74 10 1.20 11 1.74 13 2.32 11 2.90 9 3.16 9 5.13 102004 .00 3 .00 3 .00 3 .00 3 .01 4 .25 5 .57 5 .94 6 2.54 62005 .01 5 .01 5 .01 5 .02 5 .03 5 .04 4 .12 4 .18 2 .83 22006 .00 4 .00 4 .00 4 .00 4 .00 3 .00 1 .05 3 .26 4 1.44 5

16 Hydrologic Characterization for Spring Creek and Hydrologic Budget and Model Scenarios for Sheridan Lake, S. Dak.
Table 7. Comparison of monthly mean and minimum daily flow values for Spring Creek near Keystone (station 06407500), water years 

1987–2006.

Water 

year

Statistic Streamflow, in cubic feet per second

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

1987 Mean 15.70 8.10 5.00 4.15 4.04 24.00 24.00 31.00 19.90 7.89 3.33 0.74

Minimum 8.20 6.80 3.50 2.80 3.30 3.00 8.00 8.70 10.00 3.30 2.80 .06

1988 Mean .30 .35 .22 .17 .80 4.54 5.29 8.18 1.58 .05 .02 .00

Minimum .06 .20 .12 .05 .32 1.10 3.80 5.20 .20 .00 .00 .00

1989 Mean .00 .01 .08 .10 .01 .74 3.47 5.11 1.61 .16 .00 .49

Minimum .00 .00 .00 .07 .00 .00 .81 .82 .39 .00 .00 .00

1990 Mean .37 1.01 1.23 1.08 1.13 3.17 11.40 26.90 35.80 13.00 7.41 1.58

Minimum .27 .79 .80 .50 .40 .60 .79 2.30 6.60 4.10 2.50 .59

1991 Mean 1.87 3.28 1.94 1.58 3.34 6.53 15.10 84.40 147.00 44.00 20.40 6.25

Minimum .51 2.00 1.50 1.10 1.80 3.50 6.20 17.00 82.00 18.00 8.40 4.10

1992 Mean 6.25 7.31 5.85 4.57 5.40 10.80 8.67 6.49 10.00 13.70 7.25 2.81

Minimum 4.60 4.30 4.50 4.10 4.00 7.80 7.00 4.30 3.40 9.70 2.90 .76

1993 Mean 1.49 3.19 2.69 3.13 3.64 11.30 21.90 97.20 146.00 70.70 32.50 17.50

Minimum .55 1.90 1.60 2.70 1.80 4.00 13.00 35.00 81.00 50.00 6.00 14.00

1994 Mean 17.60 11.10 6.65 7.03 6.64 19.90 19.70 41.20 18.70 5.81 2.65 1.70

Minimum 13.00 4.00 4.00 5.00 5.00 9.50 15.00 24.00 3.10 2.50 .97 1.40

1995 Mean 8.73 7.84 5.96 4.75 4.40 12.70 8.90 211.00 292.00 95.80 30.00 15.70

Minimum 1.60 5.50 5.50 4.00 3.40 5.10 5.40 16.00 146.00 43.00 18.00 13.00

1996 Mean 16.40 16.90 11.20 7.57 11.40 18.40 30.50 107.00 190.00 39.00 23.00 20.10

Minimum 12.00 14.00 6.80 3.90 3.10 5.70 16.00 25.00 94.00 24.00 15.00 15.00

1997 Mean 22.90 31.20 21.40 19.70 16.30 24.00 45.70 177.00 190.00 63.80 67.00 32.50

Minimum 15.00 24.00 11.00 13.00 8.60 15.00 17.00 90.00 77.00 33.00 43.00 26.00

1998 Mean 28.00 12.80 11.30 6.89 7.34 22.30 35.50 37.00 104.00 79.10 46.60 27.10

Minimum 27.00 3.10 9.50 4.80 5.90 8.50 26.00 24.00 27.00 53.00 25.00 18.00

1999 Mean 42.10 63.80 43.60 29.70 22.60 25.20 76.90 125.00 189.00 83.90 48.90 25.40

Minimum 21.00 47.00 27.00 25.00 20.00 17.00 26.00 95.00 93.00 50.00 22.00 19.00

2000 Mean 17.50 14.30 11.00 8.86 11.30 14.60 31.30 46.70 23.10 13.40 4.21 1.71

Minimum 15.00 12.00 9.10 7.90 9.50 13.00 12.00 37.00 17.00 6.70 1.20 1.30

2001 Mean 5.61 8.16 5.62 4.71 4.93 10.50 21.60 20.20 27.50 32.30 14.10 8.37

Minimum 1.90 4.00 4.30 4.10 4.20 5.90 9.70 12.00 14.00 18.00 7.10 5.30

2002 Mean 6.80 5.93 4.23 2.72 3.24 5.95 17.40 21.50 11.40 3.40 1.70 5.12

Minimum 4.60 5.10 2.00 1.70 2.90 3.40 10.00 15.00 5.90 .35 .36 .44

2003 Mean 4.29 3.80 2.75 2.25 4.01 13.30 15.40 41.80 24.50 7.10 2.84 1.74

Minimum 3.20 3.20 1.10 1.30 3.40 3.20 11.00 22.00 18.00 1.10 .58 .67

2004 Mean 1.51 2.58 2.05 1.97 2.75 8.26 6.14 5.10 2.31 1.22 .47 .03

Minimum .96 1.80 1.70 .70 1.60 3.60 4.10 3.30 .93 .08 .00 .00

2005 Mean .03 .06 .29 .46 1.59 2.51 4.97 9.26 8.94 2.35 2.30 .04

Minimum .01 .05 .05 .07 1.10 1.30 2.20 1.90 3.50 .22 .20 .01

2006 Mean .02 .06 .09 .93 1.16 5.73 10.90 7.87 6.57 .97 .00 .00

Minimum .01 .01 .02 .16 .48 2.00 6.40 3.90 1.50 .00 .00 .00

Hydrologic Budget Concepts and Characterization of Hydrologic Data 17
Table 8. Results of linear least-squares regression between 

monthly pan evaporation at Pactola Dam and estimated monthly 

precipitation for Sheridan Lake for May and October, 1962–2006.

[r, Pearson’s correlation coefficient]

Parameter May October

Slope -0.14 -0.08

y-intercept 4.96 2.68

r -.40 -.18

18 Hydrologic Characterization for Spring Creek and Hydrologic Budget and Model Scenarios for Sheridan Lake, S. Dak.

Estimated annual precipitation for Sheridan Lake ranged 

from 13.17 inches in 1985 to 30.58 inches in 1962 (table 23). 

Precipitation was substantially above average for many years 

during the 1990s and substantially below average for many 

years during the late 1980s and the 2000s, which is consistent 

with streamflow conditions during these periods (table 2).

Evaporation

Variability in daily and monthly evaporation generally is 

much smaller than for streamflow or precipitation. However, 

evaporation is shown in subsequent sections of this report 

to be a critical variable in the hydrologic budget, relative to 

potential management options for Sheridan Lake during lowflow conditions. Thus, a thorough characterization of evaporation characteristics is useful.

Estimates of monthly evaporation for Sheridan Lake 

during the WY 1962–2006 base period were based primarily 

on measurements of pan evaporation (table 24 in the Appendix) that are available for the NWS station 396427 at Pactola 

Dam (table 1; fig. 1). Months of missing evaporation record 

are common for Pactola Dam, especially for May and October, 

when freezing temperatures (or other factors) commonly have 

precluded collection of complete records for these months. 

When possible, missing data were estimated using the same 

mixed-station (MOVE.1) procedure that was used for extrapolation of streamflow records for gaging station 06406920. 

NWS index stations from table 1 (Angostura Dam/Oral, 

Cottonwood, Shadehill Dam, Oahe Dam, and Pickstown) 

that were used in estimating pan evaporation (table 24) are 

located at considerable distances from Pactola Dam because 

the available network of evaporation pans is very sparse 

(fig. 1). Data for all stations were obtained from South Dakota 

State University (2008b). The evaporation measurements at 

Angostura Dam (station 390217) were discontinued after 1970 

and resumed nearby at Oral (station 396304) during 1971; 

however, these stations were treated as a single station. The 

index stations generally have substantially larger monthly 

evaporation than the station at Pactola Dam because of 

substantially lower altitudes; however, this general relation is 

consistent among stations, and resulting estimates are adequate 

for hydrologic budget purposes.

Compilation of summary statistics for comparisons 

among Pactola Dam and other evaporation stations was 

precluded by the sporadic nature of available data (table 24). 

For example, data sets for 1968 are complete, with the exception of one missing month at Cottonwood, and examination 

of the data indicates that for each month (1) evaporation is 

quite similar for all of the index stations and (2) evaporation 

for Pactola Dam is consistently smaller than evaporation for 

the index stations. As another example, all months for 1977 

required estimation of evaporation for Pactola Dam, and many 

months also were missing for some of the index stations.

During the entire period (1962–2006), evaporation 

data were missing for all of the evaporation stations for 

8 months (2 months for May and 6 months for October). 

Linear least-squares regression analyses (table 8) were applied 

for these individual months to estimate pan evaporation at 

Pactola Dam (table 24) as a function of estimated precipitation at Sheridan Lake (using data from table 23). Although 

the relations are weak (r values of -0.40 for May and -0.18 

for October), the negative correlations are logical (inverse 

relation to monthly precipitation). The resulting estimates for 

the missing months (table 24) are very similar to the long-term 

means for May and October (table 9).

Although monthly evaporation data were used as input 

for hydrologic budgeting purposes, consideration of maximum 

daily evaporation values could be critical for development of 

possible operating criteria for Sheridan Lake. Monthly pan 

evaporation for July averaged about 6.45 inches at Pactola 

Dam (table 9), or about 0.2 inch per day, and only 3 months 

(June of 1988 and July of 2002 and 2003) had recorded 

evaporation that exceeded 8.0 inches (table 24). A summary 

of maximum daily pan evaporation values for Pactola Dam 

for July (obtained from South Dakota State University, 2008b) 

is provided in table 10. This table provides moving average 

maximum values for 1- through 7-day intervals and ranks 

(largest to smallest) for all months with at least 7 consecutive 

days of data. The reliability of data for some of the largest 

maximum evaporation values for individual days is unknown. 

The six largest 1-day maxima range from 0.67 to 0.87 inch 

(1965, 1970, 1976, 1984, 1993, and 1994); however, the next 

largest value is 0.59 inch in 1980. Nonetheless, examination 

of the collective data set indicates that pan evaporation rates 

approaching 0.4 inch per day probably have been sustained 

for periods of several days or longer. Thus, sustained daily 

evaporation rates may exceed maximum monthly values by a 

factor of about two.

Hydrologic Budget for Sheridan Lake

The hydrologic budget for Sheridan Lake primarily 

involved long-term computations for monthly time steps, as 

described in the following section. However, a short-term 

daily budget also was developed and used for evaluation of 

monthly pan evaporation coefficients, as described in a subsequent section.
Table 9. Summary statistics for monthly pan evaporation data at Pactola Dam, 1962–2006.

[The number of observations for May and October excludes values derived using regression analysis (from table 8)]

Period/number 

of observations

Pan evaporation, in inches

Mean Standard 

deviation Maximum 75th percentile

50th percentile 

(median)

25th 

percentile Minimum

May/43 4.48 0.74 6.67 4.90 4.35 3.93 3.20

June/45 5.38 .91 8.14 6.01 5.35 4.76 3.73

July/45 6.45 .99 8.45 7.25 6.40 5.86 3.99

August/45 5.55 .70 7.24 6.00 5.59 4.96 4.43

September/45 3.88 .59 5.34 4.23 3.90 3.64 2.45

October/39 2.57 .53 3.73 2.92 2.51 2.21 1.49

Annual/45 28.29 2.57 35.35 29.68 28.31 25.85 20.56

Hydrologic Budget for Sheridan Lake 19

Long-Term Monthly Budget

A long-term (1962–2006) historical hydrologic budget 

was developed for Sheridan Lake using monthly time steps 

within an annual period running from May through April, 

referred to as a computational year. The computational year 

includes a 6-month period (May through October) for which 

evaporation is accounted for and another 6-month period 

(November through April) when evaporation is considered 

negligible due to ice cover on Sheridan Lake or minimal 

evaporation potential.

The long-term historical budget is based on equation 1 

that assumes a pass-through operating system, which typically 

has been used for Sheridan Lake. The historical budget was 

used as the basis for a hydrologic model for simulating release 

scenarios and also is useful for long-term characterization 

of estimated natural outflows for the historical pass-through 

operating system. Selected input and output data sets for the 

long-term budget are presented as tables 25–30 in the Appendix. All computations are shown to two decimal places for the 

sake of consistency; however, this is not intended to imply 

that this level of accuracy is appropriate for reporting of all 

individual values.

Stream inflow and precipitation were considered as 

inflow components (equation 1). Stream inflow was computed 

as the flow of Spring Creek at gaging station 06406920 (above 

Sheridan Lake) plus inflow from ungaged tributary areas 

between the gaging station and the spillway of Sheridan Lake 

Dam. Ungaged tributary inflow was assumed to be proportional to the flow of Spring Creek, relative to drainage area, 

as characterized in a previous section titled “Characterization 

of Historical Streamflow Data for Spring Creek.” Thus, total 

monthly stream inflow was computed by multiplying flow at 

the gaging station (table 22) by the ratio (1.146) of the total 

area at the dam (145.5 mi2) to the area at the gaging station 

(127 mi2). Monthly values of total stream inflow in units of 

acre-feet are shown in table 25, and a summary of monthly 

values in cubic feet per second is shown in table 11.

Inflow resulting from precipitation on Sheridan Lake 

was treated as “effective precipitation” that was computed by 

multiplying monthly precipitation (in inches) by an “effective precipitation coefficient.” Coefficients of 1.0 were used 

for May through October (table 12), and coefficients of 0.5 

were chosen for December through February, when ice cover 

typically prevails and potential exists for reduction of water 

content in snow pack through sublimation. Coefficients of 0.7, 

0.6, and 0.8 were chosen for November, March, and April, 

respectively, to reflect assumed conditions during transition 

periods. Monthly values of effective precipitation in units of 

acre-feet are shown in table 26. A summary of monthly values 

in cubic feet per second is provided in table 11, which shows 

that precipitation generally is a small component of the overall 

hydrologic budget, relative to stream inflow.

Evaporation from Sheridan Lake was estimated by multiplying monthly pan evaporation data (table 24) for Pactola 

Dam (NWS station 396427) by the monthly pan coefficients 

shown in table 12. Resulting monthly evaporation estimates 

in units of acre-feet are shown in table 27 in the Appendix. 

A summary of monthly values in cubic feet per second is 

provided in table 11, which shows that variability in evaporation for any given month tends to be relatively small. This 

table also shows that lake evaporation can substantially exceed 

minimum values of precipitation for all months when evaporation is considered (May through October). Similarly, lake 

evaporation can potentially approach or exceed total stream 

inflow during low-flow conditions for most months, with the 

general exception of May. Short-term evaporation rates can 

substantially exceed monthly evaporation rates, as previously 

described regarding data from table 10. Thus, evaporation is 

a particularly critical variable during low-flow periods, and 

potential exists for outflows to begin approaching zero-flow 

conditions substantially prior to the onset of zero-inflow 

conditions, especially when daily inflow and evaporation are 

considered. 

The mean of the monthly pan coefficients that were 

selected (table 12) is 0.75, which is consistent with an annual 

pan coefficient of 0.74 for the area (Farnsworth and others, 
Table 10. Moving average maximum values and ranks for 1- through 7-day intervals for pan evaporation at Pactola Dam, 1962–2006.—Continued

[--, available data not sufficient to perform computation]

Year

Number of consecutive days

1 2 3 4 5 6 7

Maximum 

evaporation 

(inches)

Rank

Maximum 

evaporation 

(inches)

Rank

Maximum 

evaporation 

(inches)

Rank

Maximum 

evaporation 

(inches)

Rank

Maximum 

evaporation 

(inches)

Rank

Maximum 

evaporation 

(inches)

Rank

Maximum 

evaporation 

(inches)

Rank

1962 0.25 42 0.24 41 0.23 41 0.21 42 0.21 42 0.21 40 0.21 401963 .28 40 .24 41 .23 41 .22 40 .23 39 .22 38 .22 351964 .37 25 .32 24 .30 26 .28 24 .27 21 .26 21 .26 201965 .67 6 .40 10 .36 10 .32 13 .31 12 .29 14 .28 141966 .43 12 .42 8 .37 7 .34 10 .33 7 .32 8 .31 81967 .29 38 .28 35 .26 34 .26 33 .25 33 .24 31 .23 321968 .30 33 .28 35 .25 38 .26 33 .26 28 .24 31 .23 321969 .36 26 .32 24 .31 21 .29 22 .27 21 .26 21 .26 201970 .80 2 .52 2 .42 1 .38 2 .32 9 .34 1 .33 21971 .30 33 .29 30 .29 27 .27 27 .27 21 .26 21 .26 201972 .30 33 .26 38 .26 34 .25 37 .25 33 .24 31 .24 301973 .40 16 .32 24 .31 21 .26 33 .23 39 .24 31 .22 351974 .39 19 .34 20 .32 19 .30 18 .30 14 .30 10 .28 141975 .32 32 .32 24 .29 27 .27 27 .27 21 .26 21 .25 261976 .68 5 .45 6 .39 4 .35 6 .31 12 -- -- -- --

1977 -- -- -- -- -- -- -- -- -- -- -- -- -- --

1978 .51 9 .32 24 .29 27 .28 24 .27 21 .26 21 .26 201979 .35 27 .30 29 .28 31 .27 27 .26 28 .26 21 .25 261980 .59 7 .43 7 .41 3 .38 2 .36 1 .30 10 .30 101981 .51 9 .48 4 .42 1 .39 1 .36 1 .34 1 .32 61982 .48 11 .37 15 .34 15 .30 18 .29 20 .27 19 .26 201983 .35 27 .34 20 .31 21 .30 18 .30 14 .30 10 .29 121984 .75 4 .50 3 .39 4 .35 6 .32 9 .28 18 .27 17

20 Hydrologic Characterization for Spring Creek and Hydrologic Budget and Model Scenarios for Sheridan Lake, S. Dak.
Table 10. Moving average maximum values and ranks for 1- through 7-day intervals for pan evaporation at Pactola Dam, 1962–2006.—Continued

[--, available data not sufficient to perform computation]

Year

Number of consecutive days

1 2 3 4 5 6 7

Maximum 

evaporation 

(inches)

Rank

Maximum 

evaporation 

(inches)

Rank

Maximum 

evaporation 

(inches)

Rank

Maximum 

evaporation 

(inches)

Rank

Maximum 

evaporation 

(inches)

Rank

Maximum 

evaporation 

(inches)

Rank

Maximum 

evaporation 

(inches)

Rank

1985 0.38 20 0.36 16 0.35 11 0.35 6 0.35 3 0.34 1 0.34 11986 .33 31 .28 35 .26 34 .24 39 .24 37 .23 36 .22 351987 .38 20 .35 18 .31 21 .27 27 .26 28 .26 21 .26 201988 .38 20 .36 16 .33 18 .33 11 .32 9 .33 7 .31 81989 .42 13 .41 9 .34 15 .33 11 .34 5 .34 1 .33 21990 .41 14 .38 13 .37 7 .36 4 .33 7 .32 8 .33 21991 .56 8 .40 10 .35 11 .32 13 .30 14 .29 14 .28 141992 .23 43 .20 43 .20 43 .19 44 .18 44 .18 43 .17 431993 .78 3 .46 5 .35 11 .29 22 .26 28 .24 31 .23 321994 .87 1 .55 1 .37 7 .30 18 .27 21 .26 21 .25 261995 .30 33 .26 38 .25 38 .25 37 .24 37 .22 38 .22 351996 .38 20 .34 20 .32 19 .31 16 .30 14 .29 14 .27 171997 .35 27 .29 30 .28 31 .26 33 .25 33 .25 29 .24 301998 .27 41 .25 40 .25 38 .22 40 .22 41 .21 40 .20 411999 .30 33 .29 30 .27 33 .27 27 .27 21 .27 19 .27 172000 .29 38 .29 30 .29 27 .28 24 .25 33 .23 36 .22 352001 .34 30 .29 30 .26 34 .27 27 .26 28 .25 29 .25 262002 .40 16 .40 10 .38 6 .36 4 .35 3 .34 1 .32 62003 .40 16 .35 18 .34 15 .32 13 .30 14 .30 10 .30 102004 .23 43 .20 43 .20 43 .20 43 .20 43 .19 42 .18 422005 .38 20 .34 20 .31 21 .31 16 .30 14 .29 14 .29 122006 .41 14 .38 13 .35 11 .35 6 .34 5 .34 1 .33 2

Hydrologic Budget for Sheridan Lake 21
Table 11. Summary of selected hydrologic budget components for Sheridan Lake, 1962–2006.

[NA, not applicable; NC, not computed]

Statistic

Monthly and annual values, in cubic feet per second, for hydrologic budget components

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

Total stream inflow

Maximum 166 416 110 57.0 30.0 41.0 59.0 39.9 25.1 22.0 24.98 74.0 NC

Mean 43.9 75.0 27.2 15.1 8.28 8.85 7.44 4.87 3.50 3.88 10.1 19.0 19.0

Minimum 3.45 1.66 .16 .05 .08 .72 .02 .15 .18 .02 1.79 3.24 NC

Effective precipitation

Maximum 5.26 5.75 4.45 2.55 3.30 2.51 0.67 0.44 0.24 0.47 1.07 2.57 NC

Mean 1.95 2.09 1.70 1.10 .84 .69 .22 .11 .09 .15 .33 1.00 0.86

Minimum .07 .34 .19 .35 .04 .02 .02 .00 .01 .02 .07 .08 NC

Lake evaporation

Maximum 1.73 2.62 3.07 3.01 2.58 1.94 NA NA NA NA NA NA NA

Mean 1.16 1.73 2.34 2.30 1.87 1.34 NA NA NA NA NA NA NA

Minimum .83 1.20 1.45 1.84 1.19 .77 NA NA NA NA NA NA NA

Table 12. Monthly coefficients for effective precipitation and pan evaporation for Sheridan Lake.

[--, evaporation not computed for November through April]

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

Effective precipitation 1.0 1.0 1.0 1.0 1.0 1.0 0.7 0.5 0.5 0.5 0.6 0.8

Pan coefficient .5 .6 .7 .8 .9 1.0 -- -- -- -- -- --

22 Hydrologic Characterization for Spring Creek and Hydrologic Budget and Model Scenarios for Sheridan Lake, S. Dak.

1982) that also is based on data for May through October. 

Farnsworth’s coefficients commonly are used for estimating 

annual evaporation from lakes or reservoirs and generally are 

suitable for estimating monthly evaporation from relatively 

shallow water bodies. However, evaporation rates from deep 

water bodies are affected by seasonal trends in surface-water 

temperatures (Kohler, 1954), which tend to lag trends in mean 

daily air temperatures and associated trends in water temperatures for evaporation pans. Kohler (1954) reported pan coefficients (computed for Lake Hefner in Oklahoma) larger than 

1.0 for 2 months (November and December) and smaller than 

0.60 for several months (late winter through early summer). 

Sacks and others (1994) reported similar results in comparing computed pan coefficients for two lakes in Florida with 

substantially different mean depths, with larger deviations 

from mean values for the deeper lake.

A short-term data set was collected during late July 

through September 2007 to facilitate development of a daily 

hydrologic budget for calculating evaporation from Sheridan Lake. Results are reported in the following section titled 

“Short-Term Daily Water Budget” and support the use of variable monthly pan coefficients.

Variability in calculated lake evaporation resulting from 

selection of monthly pan coefficients is relatively small, as 

indicated by a sensitivity analysis that is provided in table 13. 

Each incremental change of 0.1 in monthly pan coefficients 

results in an incremental change of about 13 percent in lake 

evaporation, relative to use of a constant pan coefficient of 

0.75. However, lake evaporation can substantially exceed 

inflows during low-flow periods; thus, relatively small differences in evaporation rates could substantially affect rates of 

reservoir drawdown during periods when the lake level drops 

below the spillway elevation.

Monthly values of “net inflow” (in units of cubic feet per 

second) are shown in table 28. These values were computed as

Net inflow = Stream inflow + Precipitation – Evaporation. (2)

Net inflow is equivalent to the variable reservoir outflow from 

equation 1, with the exception of months with negative values, 
Table 13. Comparison of ranges in monthly lake evaporation for Sheridan Lake for selected pan coefficients.

Pan coefficient Statistic Computed monthly lake evaporation, in inches

May June July August September October

0.65 Maximum 4.34 5.29 5.49 4.71 3.47 2.42

Mean 2.90 3.48 4.18 3.61 2.52 1.68

Minimum 2.08 2.42 2.59 2.88 1.59 .97

.75 Maximum 5.00 6.11 6.34 5.43 4.01 2.80

Mean 3.35 4.02 4.82 4.16 2.91 1.93

Minimum 2.40 2.80 2.99 3.32 1.84 1.12

1.0 Maximum 6.67 8.14 8.45 7.24 5.34 3.73

Mean 4.46 5.35 6.43 5.55 3.88 2.58

Minimum 3.20 3.73 3.99 4.43 2.45 1.49

Hydrologic Budget for Sheridan Lake 23

which occur only for the months of July through October and 

during four of the computational years, including the 3 years 

from 1987 through 1990 and 2005–06 (table 28). During such 

months, the reservoir pool would drop below the crest of the 

spillway and would result in a condition of reduced storage 

and zero outflow through the spillway.

Monthly values of end-of-month storage change for Sheridan Lake then were computed from the net inflow deficits 

(table 28), and accumulated storage deficits (in units of acrefeet) are shown by negative values in table 29. Consideration 

of the accumulated deficits allowed computation of monthly 

values (table 30) for the variable reservoir outflow (equation 1) for the pass-through operating system that historically 

has been used. A good example of the overall computational 

approach is provided by the 1987–88 computational year. 

A deficit value for net inflow (-0.46 ft3/s) was computed for 

September (table 28), which resulted in an equivalent volumetric storage deficit of -27.50 acre-ft (table 29) and an assigned 

value of 0.00 ft3/s for reservoir outflow (table 30). The storage 

deficit increased slightly for October because of continued 

deficit net inflow; however, the storage deficit decreased for 

November and was eliminated during December, for which 

a positive value of 1.82 acre-ft is shown (table 29). The only 

months for which positive values of end-of-month storage are 

shown in table 29 are when deficits are eliminated, and these 

values then could be used to compute the monthly values for 

reservoir outflow, which is 0.03 ft3/s for the example December (table 30). Values of reservoir outflow for the remaining 

months of the 1987–88 computational year are identical to the 

computed values of net inflow (table 28).

Monthly differences between computed values of reservoir outflow (table 30) and the area-adjusted flow values (for 

the period of available record) at gaging station 06407500 

(located about 5 miles downstream from Sheridan Lake, fig. 1) 

are shown in table 14. The area-adjusted flows were obtained 

by multiplying measured flows by 0.893, which is the ratio 

of the drainage areas at the dam (145.5 mi2) and at the gaging 

station (163 mi2). The area-adjusted flows were subtracted 

from the computed reservoir outflows, which result in positive 

values for months when computed outflows exceed the areaadjusted flows. There are slightly more positive (136) than 

negative (96) values, which indicates a slight bias towards 

more frequent overestimation of reservoir outflows than underestimation, relative to the area-adjusted flows. The largest 

potential source of error for this computation probably is the 

adjustment of measured values relative to tributary inflows 

from the intervening drainage area between the dam and the 

downstream gaging area, which is inconsequential relative 

to hydrologic budget applications. The mean of the differences between the computed outflows and area-adjusted flows 

is very small (-0.03) and opposite in sign to the slight bias 

towards more frequent overestimation. Figure 6A shows that 

the computed values for reservoir outflow plot closely along a 

one-to-one line for the area-adjusted flows. Figure 6B shows 

that differences between computed reservoir outflows and 

area-adjusted flows generally are quite small for the smaller 

flow values (less than 10 ft3/s), which is the flow regime of 

particular interest for the hydrologic budget purposes.

Table 15 provides a ranked list of the monthly values of 

reservoir outflow that are provided in table 30, and examination of these values provides a useful perspective on longterm streamflow conditions downstream from Sheridan Lake. 

Table 15 shows that September may be the month for greatest 

potential benefit associated with potential release scenarios 

for purposes of enhancing fish habitat and other ecosystem 

values in downstream reaches of Spring Creek. Computed 

monthly outflows for September are less than 1.0 ft3/s for 8 of 

the 44 years (18 percent) and are less than 2.0 ft3/s for 14 of 

the 44 years (32 percent). Conversely, none of the computed 

outflows for May are less than 2.0 ft3/s. A graphical representation of computed outflows over the full range of values is 

provided by the quantile plots that are presented in figure 7.
Table 14. Monthly differences between computed reservoir outflows and area-adjusted flow values for Spring Creek near Keystone (station 06407500), 1986–2006.

[--, no data]

Year Difference, in cubic feet per second

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

1986–87 -- -- -- -- -- 1.22 1.15 0.35 -0.28 -0.08 2.04 1.271987–88 2.57 -0.87 0.74 2.03 -0.66 -.26 -.31 -.17 .22 -.22 -.31 .581988–89 .38 -.30 -.04 -.02 .00 .00 -.01 -.07 -.09 -.01 5.08 .891989–90 .16 -.23 -.14 .00 -.43 -.33 -.10 .23 -.16 -.23 -.03 1.421990–91 2.42 -.62 2.29 2.20 -.67 -.14 1.07 1.03 1.39 -.32 .74 .121991–92 11.8 0 9.19 -9.19 -4.62 .09 -.17 1.41 .44 -1.19 -1.06 -.92 1.091992–93 .34 .90 1.31 .36 -.09 .90 -.01 -.36 -.56 -.37 .97 1.871993–94 -3.18 -5.48 -11.22 -3.95 -2.02 -.24 4.22 4.98 .70 1.40 1.81 1.40 1994–95 2.35 -1.27 -.10 -.89 -1.42 .18 -1.67 -.56 -.25 .52 -1.15 1.441995–96 -19.23 -47.90 -17.61 -2.31 1.04 .42 -3.59 -2.11 -.68 .15 -1.02 .581996–97 11.18 -31.77 .02 3.44 1.64 .99 .95 3.53 .83 2.29 3.33 8.421997–98 -17.44 -15.03 3.11 -2.98 .31 -3.71 1.67 1.44 .86 1.62 4.19 4.091998–99 4.89 18.49 1.79 3.95 5.33 4.79 2.31 .99 -1.18 1.86 2.80 6.40 1999–2000 -1.35 7.23 -12.79 -3.48 1.64 2.01 2.00 1.13 1.21 1.45 .71 -.412000–2001 -3.93 -2.73 -1.97 -1.10 .45 .19 -.18 -.47 -.27 -.04 -.07 1.492001–02 .06 -.43 2.20 .39 .38 2.16 2.31 .42 -.28 -.22 .53 1.132002–03 .84 .56 .15 1.75 2.21 .34 .90 .19 -.49 -.51 -1.70 6.342003–04 2.18 .49 -2.63 2.03 1.31 .50 1.76 .43 -.51 -.76 -.92 1.362004–05 .28 -.24 2.06 .63 1.04 1.03 .13 .04 .43 -.41 -.20 .982005–06 1.87 .26 .43 1.68 -.03 .25 .15 .70 -.11 -.28 .18 1.35

24 Hydrologic Characterization for Spring Creek and Hydrologic Budget and Model Scenarios for Sheridan Lake, S. Dak.
Figure 6. Relations between computed reservoir outflow for Sheridan Lake and areaadjusted flow of Spring Creek for station 06407500 (near Keystone), 1986–2006. 

A, Computed reservoir outflow plotted against area-adjusted flow. B, Computed reservoir 

outflow minus area-adjusted flow plotted against area-adjusted flow (for values less 

than or equal to 10 cubic feet per second).

0 50 100 150 200 250 300

0

50

100

150

200

250

300

1:1 line

AREA-ADJUSTED FLOW OF SPRING CREEK FOR STATION 06407500, 

IN CUBIC FEET PER SECOND

A

AREA-ADJUSTED FLOW OF SPRING CREEK FOR STATION 06407500, 

IN CUBIC FEET PER SECOND

–6

–3

0

3

6

COMPUTED RESERVOIR OUTFLOW MINUS AREA-ADJUSTED FLOW, 

IN CUBIC FEET PER SECOND

B

COMPUTED RESERVOIR OUTFLOW, IN CUBIC FEET PER SECOND

0 2 4 6 8 10

Hydrologic Budget for Sheridan Lake 25
Table 15. Ranked monthly values of computed reservoir outflows from Sheridan Lake for pass-through operating system, 1962–2006.

Ranked monthly computed reservoir outflows, 

in cubic feet per second

May June July August September October

2.57 1.11 0.00 0.00 0.00 0.00 

4.72 1.21 .00 .00 .00 .00 

4.83 1.82 .72 .14 .00 .00 

6.13 2.37 1.41 1.05 .00 .26

6.5 2.75 2.53 1.42 .10 1.05

7.25 3.08 2.63 1.48 .60 1.53

7.34 3.44 3.15 2.66 .74 1.85

7.36 7.95 3.18 3.27 .92 2.23

7.68 8.24 3.71 3.73 1.07 2.31

8.38 10.09 4.85 4.57 1.14 2.51

10.14 10.74 5.09 5.00 1.16 2.60 

11.58 11.08 5.56 5.91 1.21 3.03

12.16 12.45 5.82 6.65 1.54 3.11

18.09 15.42 7.78 6.65 1.98 3.27

20.03 16.89 8.84 6.83 2.42 4.17

20.07 17.64 9.99 8.03 2.52 4.41

21.29 17.89 11.46 8.16 2.86 4.64

25.17 18.05 12.35 8.81 3.68 5.07

26.43 22.36 12.57 9.85 4.01 5.20 

26.57 24.12 13.54 11.60 4.41 5.41

30.24 27.86 13.59 11.69 5.36 5.80 

30.92 31.34 13.89 12.18 5.67 5.86

Ranked monthly computed reservoir outflows, 

in cubic feet per second

May June July August September October

32.23 32.15 15.50 12.98 6.23 6.50 

34.24 36.57 15.63 13.25 6.78 6.56

37.76 46.03 17.81 13.43 6.91 6.88

37.92 53.13 20.08 13.59 6.95 7.54

38.62 63.87 20.32 13.80 7.40 7.86

39.13 68.66 20.94 13.82 7.45 7.93

39.49 86.56 30.09 14.16 7.69 7.97

40.77 109.98 31.03 14.21 7.85 8.23

41.05 111.50 33.96 14.73 9.13 8.71

43.25 124.85 34.02 14.96 9.22 9.33

65.62 126.54 34.83 15.29 9.43 9.60 

75.2 138.28 44.62 15.43 11.20 10.74

80.23 139.83 51.89 17.01 11.26 12.32

83.58 140.14 55.08 23.76 12.29 14.31

87.14 153.98 56.16 23.97 12.60 15.06

106.34 154.75 60.06 24.47 13.60 15.23

107.29 175.85 62.10 25.06 15.05 15.47

109.85 182.45 65.59 31.95 15.61 17.63

110.05 193.34 67.90 33.53 19.58 21.28

133.96 213.11 72.40 40.17 24.31 21.43

140.38 278.45 106.03 45.55 29.32 21.66

168.76 420.04 111.25 56.83 29.52 42.37

26 Hydrologic Characterization for Spring Creek and Hydrologic Budget and Model Scenarios for Sheridan Lake, S. Dak.

Short-Term Daily Budget

Short-term hydroclimatic data were collected at various 

sites during late July through September of 2007, which 

facilitated development of a hydrologic budget with daily time 

steps. The daily budget was used to calculate evaporation from 

Sheridan Lake and to evaluate the applicability of published 

pan coefficients. Data collection sites that were operated 

specifically for this effort were (1) a short-term continuousrecord streamflow gage at the discontinued station (06406920) 

above Sheridan Lake, (2) two partial-record streamflow gages, 

(3) a lake stage gage on Sheridan Lake, and (4) three shortterm precipitation gages read by observers. Site information 

for all sites is provided in table 1 and locations are shown on 

figure 1.

Selected data and water-balance computations are shown 

in table 16 for two short-term periods during 2007 when 

evaporation from Sheridan Lake exceeded total inflows. The 

lake stage during these periods decreased below the crest of 

the spillway (elevation of approximately 1.74 ft, relative to 

the datum of the lake stage gage), which eliminated the stream 

outflow component of the water budget and thus simplified computation of lake evaporation. This also substantially 

increased the accuracy of evaporation estimates because the 

outflow from Sheridan Lake is not measured directly.

The first column in table 16 shows the date, and the 

second column shows daily mean streamflow (in cubic feet per 

second) for station 06406920. The third column shows total 

stream inflow, which is considered representative of additional 

contributions from ungaged areas downstream from the gage 

and is calculated by multiplying measured inflow by 1.146 and 

converting to acre-feet per day. The fourth column shows the 

same daily volume of total stream inflow expressed as feet of 

water in the lake, and is computed by dividing column 3 by 

the lake surface area of 383 acres.

Partial-record streamflow gages (table 1) were operated 

along two of the largest tributaries to Sheridan Lake (fig. 1); 

however, the resulting data sets were of minimal utility for 

estimation of tributary inflows. Measurable flow was not 

recorded at the partial-record gage south of Sheridan Lake 
Figure 7. Quantile plots showing distribution of monthly values of computed reservoir outflow from 

Sheridan Lake for pass-through operating system, 1962–2006.

May

June

July

August

September

October

SPILLWAY OUTFLOW, IN CUBIC FEET PER SECOND

CUMULATIVE FREQUENCY

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0.01 0.1 1 10 100 1,000

Hydrologic Budget for Sheridan Lake 27

(station 06406960); however, minor flow (estimated as less 

than 0.01 ft3/s) was observed a short distance upstream. Flow 

measurements of 0.083 and 0.082 ft3/s were obtained for two 

dates (July 25 and August 17, 2007, respectively) at station 

06406950 along Horse Creek (just north of Sheridan Lake), 

and observations of stage for seven other dates indicated 

minimal fluctuations in stage and associated discharge. The 

flow of Horse Creek ceased entirely just downstream from the 

gage site (about 0.3 mile upstream from Sheridan Lake); thus, 

the applicability of flow observations is somewhat dubious. 

On the basis of these considerations, it was decided that the 

most appropriate approach for estimation of ungaged tributary 

inflows was by assuming proportionality relative to the gaged 

drainage area, which is the same approach used in development of the monthly hydrologic budget.

Column 5 in table 16 shows precipitation (in inches) on 

Sheridan Lake, which was estimated by averaging measurements obtained by observers at three USGS precipitation 

stations (table 1). Column 6 shows precipitation converted to 

feet, and column 7 shows the total daily inflow (streamflow 

plus precipitation), in feet. Column 8 shows mean daily lake 

stage, in feet, and column 9 shows the associated change in 

stage, relative to the previous day. This is equivalent to change 

in storage, expressed in feet, and is consistent with the units 

for the daily inflow volumes.

Because reservoir outflow was zero for all days considered, evaporation from Sheridan Lake could be computed by 

modifying equation 1 as

Evaporation = Stream inflow + Precipitation – ΔStorage. (3)

Computed values of lake evaporation (in feet) are shown in 

column 10 of table 16, and values converted to inches are 

shown in column 11. Measured daily values of pan evaporation for the station at Pactola Dam are shown in column 12. 

Values for computed lake evaporation (column 11) and measured pan evaporation (column 12) are summed for each of the 

two individual periods. For the first period, the summed values 

for lake evaporation are approximately equal to measured pan 

evaporation and would relate to a pan coefficient of 1.0. For 

the second period, the computed pan coefficient would be 1.1.

The accuracy associated with the computed values for 

daily evaporation is difficult to evaluate because of the large 

number of hydrologic variables involved in the computations. 

The resulting values for the associated short-term pan coefficients (approximately 1.0 and 1.1) are larger than the mean 
Table 16. Computations of lake evaporation for two low-flow periods during 2007.

[Volumetric computations are based on a lake surface area of 383 acres. Gaged inflow was measured at station 06406920. Precipitation is the mean of measurements for three U.S. Geological Survey precipitation stations (table 1). Pan evaporation was measured at Pactola Dam (National Weather Service station 396427). --, not applicable]

Date

Gaged inflow Gaged inflow x 1.146 Precipitation on lake Total inflow Lake stage1 Change in stage Computed evaporation for Sheridan Lake Measured pan evaporation

(ft3/s) (acre-feet) (feet) (inches) (feet) (feet) (feet) (feet) (feet) (inches) (inches)

8/10/2007 -- -- -- -- -- -- 1.75 -- -- -- --

8/11/2007 0.72 1.64 0.0043 0.000 0.0000 0.0043 1.73 -0.02 0.0243 0.29 0.20

8/12/2007 .50 1.14 .0030 .000 .0000 .0030 1.71 -.02 .0230 .28 .238/13/2007 .44 1.00 .0026 .000 .0000 .0026 1.70 -.01 .0126 .15 .258/14/2007 .26 .59 .0015 .160 .0133 .0149 1.69 -.01 .0249 .30 .218/15/2007 .20 .45 .0012 .030 .0025 .0037 1.69 .00 .0037 .04 .158/16/2007 .24 .55 .0014 .000 .0000 .0014 1.68 -.01 .0114 .14 .15

Sum -- -- -- -- -- -- -- -- -- 1.20 1.19

9/12/2007 -- -- -- -- -- -- 1.75 -- -- -- --9/13/2007 .76 1.73 .0045 .000 .0000 .0045 1.74 -.01 .0145 .17 .089/14/2007 .74 1.68 .0044 .000 .0000 .0044 1.74 .00 .0044 .05 .119/15/2007 .71 1.61 .0042 .000 .0000 .0042 1.73 -.01 .0142 .17 .159/16/2007 .69 1.57 .0041 .000 .0000 .0041 1.72 -.01 .0141 .17 .159/17/2007 .61 1.39 .0036 .000 .0000 .0036 1.71 -.01 .0136 .16 .139/18/2007 .50 1.14 .0030 .030 .0025 .0055 1.70 -.01 .0155 .19 .099/19/2007 .60 1.36 .0036 .000 .0000 .0036 1.70 .00 .0036 .04 .099/20/2007 .54 1.23 .0032 .000 .0000 .0032 1.69 -.01 .0132 .16 .259/21/2007 .48 1.09 .0028 .000 .0000 .0028 1.69 .00 .0028 .03 .159/22/2007 .42 .95 .0025 .000 .0000 .0025 1.67 -.02 .0225 .27 .199/23/2007 .36 .82 .0021 .030 .0025 .0046 1.66 -.01 .0146 .18 .159/24/2007 .30 .68 .0018 .000 .0000 .0018 1.65 -.01 .0118 .14 .089/25/2007 .24 .55 .0014 .000 .0000 .0014 1.64 -.01 .0114 .14 .079/26/2007 .18 .41 .0011 .000 .0000 .0011 1.63 -.01 .0111 .13 .08

Sum -- -- -- -- -- -- -- -- -- 2.01 1.77

1Mean lake stage in feet above arbitrary datum. Lake spills at stage of about 1.74 feet.

28 Hydrologic Characterization for Spring Creek and Hydrologic Budget and Model Scenarios for Sheridan Lake, S. Dak.
Hydrologic Model and Scenarios for Sheridan Lake 29

pan coefficients reported by Farnsworth and others (1982); 

however, they are consistent with results reported by Kohler 

(1954) and Sacks and others (1994) for late summer and 

early fall periods. Thus, the values of monthly pan coefficients (table 12) used for hydrologic budgeting are considered 

reasonable.

If future management alternatives are implemented, lake 

evaporation could be a critical factor in management of drawdown conditions in Sheridan Lake. As such, future monitoring 

of variables involved in computation of evaporation rates and 

associated pan coefficients could have future value.

Hydrologic Model and Scenarios for 

Sheridan Lake

Within this section, the modeling approach and model 

scenarios are described. Model limitations also are described.

Modeling Approach and Model Scenarios

Numerous approaches and scenarios for hydrologic 

modeling are possible. For the sake of simplicity, however, 

a very basic approach was used to simulate storage deficits 

and drawdown in Sheridan Lake under different release 

scenarios. This approach entailed an initial assumption of a 

constant release (for various hypothetical release rates) for the 

months of May through October for all 44 years (1962–2006) 

of the historical monthly hydrologic budget. Although more 

detailed manipulation of releases probably would be expected 

under actual operating conditions, this approach has no effect 

on monthly outflow and storage conditions, when natural 

outflows exceed prescribed releases.

The hydrologic model was developed using the primary 

components of the hydrologic budget that were described in 

a previous section titled “Long-Term Monthly Budget.” The 

model was used to simulate storage deficits and drawdown for 

Sheridan Lake using prescribed hypothetical release scenarios. 

Model output consisted simply of computed monthly values 

for end-of-month storage for prescribed release scenarios.

The computational process involved consideration of 

equation 4:

Reservoir outflow = Spillway outflow + Prescribed release, (4)

where 

Reservoir outflow is from equation 1,

Spillway outflow is the portion of reservoir outflow 

 that occurs through the spillway, 

 and 

Prescribed release is the portion of reservoir outflow 

 that occurs through the control 

 valve.

Computations were performed by first calculating spillway outflow for each month, which could be done by subtracting the prescribed release for each month (May through 

October) from the matrix of monthly values of net inflow 

(table 28), because reservoir outflow was shown in equation 2 

to be essentially equivalent to net inflow for the historical 

pass-through operating condition. Negative values of spillway outflow are not physically possible, but were computed 

for months when the prescribed release exceeds net inflow. 

This condition prompted computation of a monthly value for 

the storage deficit, based on the negative value for spillway 

outflow. Monthly storage deficits then were accumulated on 

a month-by-month basis, as was done in the computational 

process that was described in a previous section titled “LongTerm Monthly Budget.” Maintaining aquatic ecosystems 

downstream from Sheridan Lake would require continuation 

of releases into November (or beyond), for cases when storage 

deficits occur for October. Thus, releases of 1 ft3/s were 

assigned for November for such cases, prior to computation of 

the storage deficit for November. This process was continued 

on a month-by-month basis through the month of April for 

each year and into the following May, if necessary.

Model output is shown in tables 31–37 in the Appendix 

for release scenarios of 1, 2, 3, 4, 5, 6, and 7 ft3/s and consists 

of monthly values of end-of-month storage (in acre-feet) for 

each of the seven scenarios. These scenarios cover the range 

of plausible low-flow releases for the new valve system. A 

summary of model output is provided in table 17. For each 

computational year, table 17 shows the number of months for 

which storage deficits were computed for each of the release 

scenarios, along with the maximum storage deficit (in acrefeet) and an approximate value for the associated maximum 

drawdown, in feet below the spillway crest. Figure 8 shows 

the maximum computed drawdown by year for each of the 

hypothetical release scenarios.

The drawdown values in table 17 and figure 8 were 

approximated by dividing the storage deficits in acre-feet by 

the lake surface area of 383 acres. This approach was used 

because relations between area and capacity have not been 

developed for Sheridan Lake. A lake survey was performed by 

SDGF&P during 2007 to determine the approximate configuration of the shoreline at a drawdown of 2 ft, and results 

indicated that the surface area would be reduced by about 

8 acres with 1 ft of drawdown and by about 15 acres with 2 ft 

of drawdown (Ron Koth, SDGF&P, written commun., 2008). 

Thus, within the planned potential operating range of about 

2 ft of drawdown, the effect on the computed drawdown is 

only about 3.9 percent and does not substantially affect the 

model results. For progressively larger drawdowns, actual 

results would exceed model results by progressively larger 

percentages, and would quickly reach a threshold of general 

unreliability. Computations involving storage volumes associated with depths of precipitation and evaporation also would 

be affected slightly by relations between area and capacity; 

however, effects on model results are considered negligible.
Table 17. Summary of selected output from hydrologic model for various release scenarios, 1962–2006.—Continued

[For each computational year and release scenario, this table shows the number (no.) of months with storage deficits, the maximum computed deficit (acre-feet), and the associated maximum drawdown (feet). ft3/s, cubic feet per second; <, less than; --, no storage deficit]

Year

Release = 0 ft3/s Release = 1 ft3/s Release = 2 ft3/s Release = 3 ft3/s Release = 4 ft3/s Release = 5 ft3/s Release = 6 ft3/s Release = 7 ft3/s

no.

acrefeet feet no. acre- feet feet no. acre- feet feet no. acre- feet feet no. acre- feet feet no. acre- feet feet no. acre- feet feet no. acre- feet feet

1962–63 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --1963–64 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --1964–65 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 2 71 0.2 3 192 0.5 3 313 0.81965–66 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --1966–67 -- -- -- -- -- -- -- -- -- 1 15 <0.1 2 74 0.2 2 143 .4 3 264 .7 3 385 1.01967–68 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --1968–69 -- -- -- -- -- -- -- -- -- 1 43 .1 2 123 .3 3 244 .6 5 365 1.0 7 486 1.31969–70 -- -- -- -- -- -- 1 51 0.1 1 110 .3 2 170 .4 2 230 .6 4 346 .9 5 467 1.21970–71 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 1 7 <.11971–72 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --1972–73 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --1973–74 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 2 30 .11974–75 -- -- -- -- -- -- 3 83 .2 8 264 .7 9 561 1.5 10 864 2.3 10 1,168 3.0 10 1,471 3.81975–76 -- -- -- -- -- -- -- -- -- 1 28 .1 2 88 .2 2 169 .4 3 290 .8 3 411 1.11976–77 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 1 12 <.1 2 79 .21977–78 -- -- -- -- -- -- -- -- -- -- -- -- 1 54 .1 1 114 .3 2 173 .5 4 233 .61978–79 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 2 77 .21979–80 -- -- -- -- -- -- 1 27 .1 2 87 .2 2 206 .5 2 327 .9 4 453 1.2 7 636 1.71980–81 -- -- -- 1 5 <0.1 3 64 .2 3 154 .4 4 275 .7 6 515 1.3 9 759 2.0 10 1,003 2.61981–82 -- -- -- 1 24 .1 2 83 .2 2 143 .4 4 247 .6 6 368 1.0 7 489 1.3 7 610 1.61982–83 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --1983–84 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 1 59 .2 1 119 .3 2 178 .51984–85 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --1985–86 -- -- -- 3 70 .2 6 243 .6 9 450 1.2 10 815 2.1 11 1,180 3.1 11 1,545 4.0 11 1,910 5.01986–87 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 1 22 .11987–88 3 46 0.1 7 307 .8 7 428 1.1 8 549 1.4 8 670 1.7 9 791 2.1 9 974 2.5 9 1,156 3.01988–89 8 246 .6 9 609 1.6 11 906 2.4 11 1,209 3.2 12 1,532 4.0 12 2,018 5.3 12 2,565 6.7 12 3,113 8.11989–90 4 89 .2 9 270 .7 11 704 1.8 12 1,372 3.6 12 2,059 5.4 12 2,910 7.6 12 3,823 10.0 12 4,735 12.4

30 Hydrologic Characterization for Spring Creek and Hydrologic Budget and Model Scenarios for Sheridan Lake, S. Dak.
Table 17. Summary of selected output from hydrologic model for various release scenarios, 1962–2006.—Continued

[For each computational year and release scenario, this table shows the number (no.) of months with storage deficits, the maximum computed deficit (acre-feet), and the associated maximum drawdown (feet). ft3/s, cubic feet per second; <, less than; --, no storage deficit]

Year

Release = 0 ft3/s Release = 1 ft3/s Release = 2 ft3/s Release = 3 ft3/s Release = 4 ft3/s Release = 5 ft3/s Release = 6 ft3/s Release = 7 ft3/s

no.

acrefeet feet no. acre- feet feet no. acre- feet feet no. acre- feet feet no. acre- feet feet no. acre- feet feet no. acre- feet feet no. acre- feet feet

1990–91 -- -- -- 1 15 <0.1 2 104 0.3 3 225 0.6 4 346 0.9 6 840 2.2 8 1,814 4.7 11 2,788 7.31991–92 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 2 56 .1 2 177 .51992–93 -- -- -- -- -- -- -- -- -- 2 82 .2 4 203 .5 5 324 .8 6 445 1.2 8 577 1.51993–94 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --1994–95 -- -- -- 1 53 .1 2 145 .4 2 266 .7 3 387 1.0 4 508 1.3 6 685 1.8 7 867 2.31995–96 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --1996–97 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --1997–98 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --1998–99 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --1999–2000 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --2000–2001 -- -- -- -- -- -- 1 1 <.1 2 82 .2 3 203 .5 3 324 .8 4 494 1.3 5 676 1.82001–02 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --2002–03 -- -- -- -- -- -- -- -- -- -- -- -- 2 95 .2 4 218 .6 7 408 1.1 8 652 1.72003–04 -- -- -- -- -- -- 1 9 <.1 2 79 .2 4 200 .5 8 427 1.1 9 671 1.8 9 915 2.42004–05 -- -- -- -- -- -- 9 274 .7 11 517 1.4 11 821 2.1 12 1,134 3.0 12 1,499 3.9 12 1,864 4.92005–06 1 87 .2 6 196 .5 7 317 .8 8 438 1.1 10 666 1.7 12 1,208 3.2 12 1,938 5.1 12 2,668 7.0

Hydrologic Model and Scenarios for Sheridan Lake 31
Figure 8. Maximum drawdown by year for hypothetical release scenarios, 1962–2006.

1960 1970 1980 1990 2000 2010

COMPUTATIONAL YEAR (MAY–APRIL)

0

2

4

6

8

10

12

14

No release

Release, in cubic feet per second

1

2

3

4

5

6

7

MAXIMUM END-OF-MONTH DRAWDOWN, IN FEET

32 Hydrologic Characterization for Spring Creek and Hydrologic Budget and Model Scenarios for Sheridan Lake, S. Dak.

Results of the hydrologic model show that five of the 

computational years (3 years that include 1987–90 and 2 years 

that include 2004–06) tend to be “defining” years for purposes 

of drawdown considerations for Sheridan Lake. These 

5 years include the only years that had storage deficits for 

the historical pass-through operating condition (zero-release 

scenario). Computed drawdowns for 1987–90 approach or 

exceed 1 ft (383 acre-ft) for many months for a prescribed 

release of 1 ft3/s and approach or exceed 2 ft (766 acre-ft) for 

many months for a prescribed release of 2 ft3/s (tables 31 and 

32). For prescribed releases of 1 and 2 ft3/s, the maximum 

computed drawdowns of 1.6 and 2.4 ft, respectively (table 17), 

occur in February of the 1988–89 computational year. For 

a prescribed release of 7 ft3/s, computed drawdown exceeds 

12 ft (4,596 acre-ft) for one-half of the months of the 1989–90 

computational year (table 37). During the 2004–05 and 

2005–06 computational years, 16 of 24 months have computed 

storage deficits for a prescribed release of 2 ft3/s.

The extent to which 1987–90 are defining years for 

drawdown considerations is further exemplified by examination of table 31, which provides results for a prescribed 

release of 1 ft3/s. Computed storage deficits occur for 25 of 

36 months during these 3 computational years, as opposed to a 

combined total of only 13 months with storage deficits for the 

other 41 years. Storage deficits are eliminated by April for the 

3 years during the 1987–90 period and by March or earlier for 

the other 6 years for which storage deficits are computed. 

For a prescribed release of 2 ft3/s (table 32), storage 

deficits are computed for 60 months during 15 of the 44 years. 

For this scenario, a storage deficit is computed for May of the 

1989–90 computational year. This is the only computational 

year in which a storage deficit persists from a previous year, 

and deficits exist for 22 of the 24 months for these 2 years 

(1988–90). For a prescribed release of 3 ft3/s (table 33), 

storage deficits exist at the end (April) of four computational 

years, but are eliminated during the following May for three 

of these cases. For this release scenario (3 ft3/s), a storage 

deficit also is initiated during May of the 1985–86 computational year and persists through much of that year. Net inflow 

of 2.57 ft3/s for this month (table 28) is the minimum that was 

computed for the entire 1962–2006 base period.

Examination of tables 34 through 37 shows that 

computed storage deficits become progressively larger and 

more frequent for each of the progressively larger release 

scenarios of 4 through 7 ft3/s. This observation is consistent 

with the results that are summarized in figure 8 and table 17. 

It also is informative from examination of table 17 that there 

were five consecutive years (1995–2000) for which storage 

deficits do not occur for any of the modeled release scenarios.

Model Limitations

A primary limitation of the hydrologic model is the 

uncertainty associated with development of the extrapolated 

estimates of monthly streamflow for Spring Creek above 

Sheridan Lake (table 22). Although the estimates are inexact, 

they do provide a much more realistic perspective of longterm flow conditions than what could be derived from the 

short-term streamflow records that exist for Spring Creek. 
Summary 33

The 44 year base period that is modeled (1962–2006) 

probably is reasonably representative of long-term climatic 

conditions. Driscoll and others (2000) noted severe, sustained 

drought conditions for the Black Hills area during 1931–40 

and 1948–61; however, extrapolation of streamflow records 

for these periods is not feasible. Driscoll and others (2000) 

also note that the late 1900s was the wettest recorded period 

since 1931. Thus, the wetter end of the hydrologic regime is 

well represented by this period and by conditions during 1962 

through 1986, which is noted as a period for which computed 

storage deficits did not occur for the pass-through operating system that historically has been used for Sheridan Lake 

(table 29).

The monthly time steps that were used cannot account 

for short-term (weekly and daily) variability that is commonplace for hydrologic events. However, the overall purpose of 

representing general, long-term conditions has been satisfied. Considering all factors, the hydrologic budget provides 

a reasonable representation of long-term conditions, and the 

model similarly provides a reasonable representation of drawdown for the release scenarios that were considered.

Summary

The U.S. Geological Survey cooperated with South 

Dakota Game, Fish and Parks to compile and characterize 

hydrologic information relevant to management of water 

resources associated with Sheridan Lake, which is located in 

the central Black Hills of western South Dakota and is formed 

by a dam on Spring Creek. This effort consisted primarily 

of compilation, characterization, and analysis of hydrologic 

data for a base period of 1962 through 2006, development 

of a hydrologic budget for Sheridan Lake for this timeframe, 

and development of an associated model for simulation of 

storage deficits and drawdown in Sheridan Lake for hypothetical release scenarios from the lake. Historically, the dam 

has been operated primarily as a “pass-through” system, in 

which unregulated outflows pass over the spillway. In 2004, 

the dam was retrofitted with an improved control valve system 

that would allow controlled releases of about 7 cubic feet per 

second (ft3/s) or less from a fixed depth of about 60 feet (ft). 

Such releases potentially could provide benefits to downstream fishery resources and other cold-water aquatic ecosystems; however, associated drawdowns of the reservoir pool 

would need to be very small, probably no more than about 2 ft 

below the spillway crest.

Development of a hydrologic budget for Sheridan Lake 

involved compilation, estimation, and characterization of 

data sets for streamflow, precipitation, and evaporation. 

Most available hydrologic data sets were not directly applicable for development of the hydrologic budget; thus, it was 

necessary to estimate many of the hydrologic variables. The 

most critical data need was for extrapolation of available 

short-term streamflow records for Spring Creek to be used 

as the long-term inflow to Sheridan Lake. Available shortterm records for water years (WY) 1991–2004 for gaging 

station 06406920 (above Sheridan Lake) are biased by especially large streamflow that occurred during the 1990s. These 

records were extrapolated to WY 1962–2006 on the basis of 

correlations with streamflow records (WY 1987–2006) for a 

downstream station and for stations located along two adjacent 

streams (Battle Creek, WY 1962–2006; and Boxelder Creek, 

WY 1967–2006). Comparisons of historical data for the two 

streamflow-gaging stations along Spring Creek indicate that 

contributions of streamflow from the intervening drainage 

area are approximately proportional to drainage area, which 

was used as a means of estimating tributary inflow for the 

hydrologic budget. Analysis of evaporation data shows that 

sustained daily evaporation rates may exceed maximum 

monthly rates by a factor of about two.

A long-term (1962–2006) hydrologic budget was developed for computation of reservoir outflow from Sheridan 

Lake for the historical pass-through operating system. Two 

inflow components (stream inflow and precipitation) were 

considered in the hydrologic budget, and evaporation was 

the only outflow component that was considered. The hydrologic budget uses monthly time steps within an annual period 

running from May through April, referred to as a computational year. The computational year includes a 6-month period 

(May through October) for which evaporation is accounted for 

and another 6-month period (November through April) when 

evaporation is considered negligible due to ice cover on Sheridan Lake or minimal evaporation potential. The hydrologic 

budget indicates that monthly evaporation rates can substantially exceed monthly inflow during low-flow periods. Thus, 

evaporation is a particularly critical variable during low-flow 

periods, and potential exists for outflows to begin approaching 

zero-flow conditions substantially prior to the onset of zeroinflow conditions, especially when daily inflow and evaporation are considered. Results also indicate that September may 

be the month for greatest potential benefit for enhancing fish 

habitat and other ecosystem values in downstream reaches 

of Spring Creek with managed releases. Computed monthly 

outflows for Sheridan Lake are less than 1.0 cubic feet per 

second (ft3/s) for 8 of the 44 years (18 percent) and are less 

than 2.0 ft3/s for 14 of the 44 years (32 percent). Conversely, 

none of the computed outflows for May are less than 2.0 ft3/s.

A short-term data set was collected during late July 

through September 2007 to facilitate development of a 

hydrologic budget with daily time-steps, which was used to 

calculate evaporation from Sheridan Lake and to evaluate the 

applicability of published pan coefficients. Computed values 

of pan coefficients of approximately 1.0 and 1.1 for two lowflow periods are larger than the mean annual pan coefficient of 

0.74 for the area that is reported in the literature; however, the 

computed values are consistent with pan coefficients reported 

elsewhere for late summer and early fall periods. Thus, these 

results supported the use of variable monthly pan coefficients 

for the long-term hydrologic budget.
34 Hydrologic Characterization for Spring Creek and Hydrologic Budget and Model Scenarios for Sheridan Lake, S. Dak.

A hydrologic model was developed using the primary 

components of the hydrologic budget and was used to simulate storage deficits and drawdown for Sheridan Lake using 

hypothetical release scenarios from the lake. Model output 

consisted of monthly values of storage deficits for prescribed 

constant releases for the months May through October for 

1962–2006. Release scenarios of 1, 2, 3, 4, 5, 6, and 7 ft3/s 

were considered, which covers the range of plausible low-flow 

releases for the new valve system. Although more detailed 

manipulation of releases probably would be expected, this 

approach has no effect on monthly outflow and storage 

conditions when natural outflows exceed prescribed releases. 

Maintaining aquatic ecosystems downstream from Sheridan 

Lake would require continuation of releases into November 

(or beyond), for cases when storage deficits occur in October. 

Thus, releases of 1 ft3/s were assigned for November for such 

cases, prior to computation of the storage deficit for November. This process was continued on a month-by-month basis 

through the month of April for each year and into the following May, if necessary.

Five computational years (3 years that include 1987–90 

and 2 years that include 2004–06) tend to be “defining” 

years for purposes of drawdown considerations for Sheridan 

Lake. These include the only years with storage deficits for 

the historical pass-through operating condition (zero-release 

scenario). Computed drawdowns for 1987–90 approach 

or exceed 1 ft for many months for a prescribed release of 

1 ft3/s and approach or exceed 2 ft during many months for a 

prescribed release of 2 ft3/s. For prescribed releases of 1 and 

2 ft3/s, the maximum computed drawdowns of 1.6 and 2.4 ft, 

respectively, occur in February of the 1988–89 computational 

year. For a prescribed release of 7 ft3/s, computed drawdown 

exceeds 12 ft for one-half of the months of the 1989–90 

computational year. During the 2004–05 and 2005–06 

computational years, storage deficits were computed for 16 of 

24 months for a prescribed release of 2 ft3/s.

Computed storage deficits occur for 25 of 36 months 

during the 1987–90 computational years for a prescribed 

release of 1 ft3/s, as opposed to a combined total of only 

13 months with storage deficits for the other 41 years. All 

of the storage deficits are eliminated by April for the 3 years 

during the 1987–90 period and by March or earlier for the 

other 6 years for which storage deficits are computed. For a 

prescribed release of 2 ft3/s, storage deficits are computed for 

60 months during 15 of the 44 years, and deficits exist for 22 

of the 24 months during the 1988–90 computational years. For 

a prescribed release of 3 ft3/s, storage deficits exist at the end 

(April) of four computational years, but are eliminated during 

the following May for three of these cases. Computed storage 

deficits become progressively larger and more frequent for 

each of the progressively larger release scenarios of 4 through 

7 ft3/s.

References Cited

Alley, W.M, and Burns, A.W., 1983, Mixed station extension of monthly streamflow records: Journal of Hydraulic 

Engineering, American Society of Civil Engineers, v. 109, 

no. 10, p. 1,272–1,284.

Cary, L.E., and Parrett, Charles, 1996, Synthesis of natural 

flows at selected sites in the upper Missouri River Basin, 

Montana, 1928–89: U.S. Geological Survey WaterResources Investigations Report 95–4261, 109 p.

DeWitt, Ed, Redden, J.A., Buscher, David, and Wilson, A.B., 

1989, Geologic map of the Black Hills area, South Dakota 

and Wyoming: U.S. Geological Survey Map I–1910, 

scale 1:250,000, 1 sheet.

Driscoll, D.G., and Carter, J.M., 2001, Hydrologic conditions 

and budgets for the Black Hills of South Dakota, through 

water year 1998: U.S. Geological Survey Water-Resources 

Investigations Report 01–4226, 143 p., accessed May 30, 

2007, at http://pubs.usgs.gov/wri/wri014226/.

Driscoll, D.G., Hamade, G.R., and Kenner, S.J., 2000, Summary of precipitation data for the Black Hills of South 

Dakota, water years 1931–98: U.S. Geological Survey 

Open-File Report 00–329, 151 p., accessed May 30, 2007, 

at http://pubs.usgs.gov/wri/ofr00329/.

Erickson, J.W., 2002, Development of a temperature model for 

a reach of Spring Creek below Sheridan Lake, Pennington 

County, South Dakota: South Dakota Game, Fish and Parks, 

report on Dingell-Johnson project F–21–R–31, 48 p.

Farnsworth, R.K., Thompson, E.S., and Peck, E.L., 1982, 

Evaporation atlas for the contiguous 48 United States: 

National Oceanic and Atmospheric Administration Technical Report NWS 33, 26 p., 4 pl.

Helsel, D.R., and Hirsch, R.M., 1992, Statistical methods in 

water resources: New York, Elsevier, 529 p.

Kohler, M.A., 1954, Lake and pan evaporation, in U.S. Geological Survey, Water-loss investigations— Lake Hefner 

studies, technical report: U.S. Geological Survey Professional Paper 269, p. 127–148.

Powell, B.F., 1940, Construction history and details of the 

Sheridan Dam: Rapid City, South Dakota School of Mines 

and Technology, The Black Hills Engineer, 261 p.

Sacks, L.A., Lee, T.M., and Radell, M.J., 1994, Comparison of 

energy-budget evaporation losses from two morphometrically different Florida seepage lakes: Journal of Hydrology, 

v. 156, p. 311–334.
References Cited 35

South Dakota Department of Environment and Natural 

Resources, 2008, Nonpoint source pollution total maximum 

daily loads (TMDLs)—schedules and summaries: accessed 

December 8, 2008, at http://www.state.sd.us/denr/dfta/

watershedprotection/tmdlpage.htm#TMDL%20Project%20

Status

South Dakota Game, Fish and Parks, 2005, South Dakota 

statewide fisheries survey: accessed May 19, 2008, at

http://www.sdgfp.info/wildlife/fishing/WesternLakes/

SheridanLake04.pdf

South Dakota State University, 2008a, Temperature normals 

(1971–2000): accessed May 19, 2008, at http://climate.

sdstate.edu/archives/data/tempnormals.shtm

South Dakota State University, 2008b, Monthly coop weather 

data: accessed May 27, 2008, at http://climate.sdstate.edu/

coop/monthly.asp

Streeter, V.L., and Wylie, E.B., 1979, Fluid mechanics 

(7th ed.): New York, McGraw-Hill, 562 p.

U.S. Geological Survey, 2008, USGS surface-water data for 

South Dakota: accessed May 28, 2008, at http://waterdata.

usgs.gov/sd/nwis/sw/.

Appendix
38 Hydrologic Characterization for Spring Creek and Hydrologic Budget and Model Scenarios for Sheridan Lake, S. Dak.

Table 18. Monthly and annual streamflow data for Battle Creek near Keystone (station 06404000), water years 1962–2006.—Continued

Water year

Streamflow, in cubic feet per second

Month

Annual

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

1962 0.00 0.06 0.03 0.00 0.02 0.46 2.17 36.60 65.00 46.30 14.70 3.59 14.20

1963 5.20 3.09 2.11 1.25 2.11 7.11 19.40 22.90 85.50 21.30 3.90 6.11 15.00

1964 2.93 3.00 2.24 1.94 3.03 2.57 5.82 12.50 29.10 25.70 4.16 1.81 7.90

1965 1.25 1.32 1.32 1.29 1.01 1.13 4.64 67.60 91.10 44.30 13.00 4.87 19.50

1966 4.70 3.56 3.13 1.88 1.40 4.39 11.30 6.20 1.93 1.35 2.90 2.64 3.79

1967 4.14 2.55 1.64 1.76 1.73 2.54 4.22 9.37 131.40 19.10 4.02 2.74 15.30

1968 2.12 2.50 1.85 2.07 2.42 3.40 3.14 2.93 16.50 5.84 3.26 2.26 4.01

1969 1.10 1.34 1.34 1.05 .74 1.35 4.38 3.06 7.83 41.90 4.25 .56 5.80

1970 1.48 1.72 .93 .16 .33 1.03 9.78 17.80 40.90 3.35 3.36 1.37 6.83

1971 2.18 1.20 .63 .83 1.19 3.46 38.80 71.20 59.80 6.77 1.64 1.46 15.80

1972 2.25 2.18 1.68 .67 .66 3.54 4.93 13.40 199.20 15.80 7.61 3.78 21.10

1973 2.73 2.89 1.65 1.64 1.20 4.83 37.60 24.50 13.40 5.89 4.80 2.13 8.61

1974 1.89 2.47 1.04 .87 1.20 2.62 3.61 3.05 1.74 1.08 .10 .11 1.65

1975 .32 .86 .13 .00 .37 1.44 13.00 10.50 21.10 5.21 2.14 .00 4.58

1976 .07 .45 1.48 1.35 1.85 1.77 5.24 49.80 72.30 13.90 7.95 1.94 13.20

1977 1.84 1.53 1.54 .72 1.43 3.58 11.60 3.91 1.61 1.43 2.84 1.40 2.78

1978 1.89 1.77 1.47 .69 .96 4.25 5.20 89.80 25.40 5.45 3.07 .86 11.90

1979 .95 1.21 1.02 .53 .80 2.50 5.05 2.78 4.72 33.00 15.60 3.08 6.00

1980 1.40 2.77 2.01 .43 .96 3.29 7.49 5.19 3.87 1.28 .98 .15 2.48

1981 1.85 1.32 2.28 .95 .65 1.44 1.49 44.70 6.16 4.02 3.43 .25 5.79

1982 1.38 1.05 .76 .50 1.38 2.96 3.68 20.10 31.90 8.50 2.48 1.84 6.38

1983 4.85 2.64 1.83 1.27 1.45 2.65 5.57 16.90 8.20 1.78 .39 .00 3.98

1984 .75 1.32 1.15 1.80 1.73 1.96 5.19 22.70 51.40 12.90 2.68 .47 8.65

1985 1.46 1.22 .69 .75 .04 3.78 3.71 1.24 .22 .07 .01 .04 1.11

1986 .25 .48 .63 1.46 1.67 3.03 11.60 16.60 14.70 4.51 1.05 4.70 5.05

1987 12.70 5.24 4.25 2.64 2.91 12.80 12.70 18.10 8.50 1.77 .09 .00 6.84

1988 .21 .76 .42 .12 .28 1.47 1.90 2.25 .65 .23 .03 .00 .69

1989 .00 .00 .00 .00 .00 1.95 1.77 1.64 .64 .04 .00 6.20 1.02

1990 2.57 1.82 1.14 .69 1.52 3.83 6.46 33.40 23.80 17.00 5.45 1.45 8.32

1991 1.04 1.68 .98 .62 1.55 2.65 9.22 73.60 92.80 10.30 3.92 1.60 16.70

1992 2.16 2.47 1.78 2.17 2.72 4.90 3.37 2.71 6.20 9.86 2.95 .66 3.50

1993 .59 1.61 1.66 1.45 1.05 4.75 12.30 58.00 68.00 17.30 10.10 4.16 15.10

1994 5.89 4.62 5.69 4.54 5.64 9.99 5.34 12.60 4.53 .80 .45 .17 5.03

1995 7.09 4.04 3.21 2.06 3.29 4.40 6.06 153.30 115.10 21.40 6.94 3.68 27.70

1996 4.59 4.74 3.64 4.66 9.57 6.35 10.60 66.70 39.20 8.20 8.63 5.90 14.40

1997 7.56 22.70 9.21 12.70 6.63 8.97 19.90 112.30 48.30 15.40 12.30 7.20 23.70

1998 3.59 3.60 3.72 3.96 4.39 7.35 14.70 13.60 55.70 20.30 19.10 5.29 12.90

1999 22.50 36.00 25.80 7.34 7.52 7.63 36.60 33.20 94.80 23.70 20.50 5.78 26.80

2000 4.41 5.51 4.09 3.47 4.54 4.85 20.00 24.60 10.60 4.67 .64 .10 7.29

2001 1.03 3.23 2.03 1.77 2.20 6.52 15.20 11.20 16.10 22.50 6.86 1.91 7.58

2002 2.67 2.99 2.28 1.22 .68 1.29 7.14 12.00 3.99 1.19 .15 .76 3.04
Appendix 39

Table 18. Monthly and annual streamflow data for Battle Creek near Keystone (station 06404000), water years 1962–2006.—Continued

Water year

Streamflow, in cubic feet per second

Month

Annual

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

2003 1.04 1.55 1.03 0.83 1.33 5.65 7.50 22.50 7.79 1.16 0.15 0.07 4.24

2004 .12 .57 .86 .44 .89 2.57 1.80 2.07 1.52 1.06 .15 .67 1.06

2005 .23 .50 .42 .40 .74 1.48 2.69 7.93 6.23 6.36 2.17 .03 2.45

2006 .69 .63 .32 .57 .53 3.02 5.99 4.72 5.72 .42 .28 .56 1.95

Statistical summary

Number of values 45 45 45 45 45 45 45 45 45 45 45 45 45

Mean 2.88 3.31 2.38 1.72 1.96 3.86 9.55 27.59 35.45 11.43 4.69 2.10 8.93

Maximum 22.50 36.00 25.80 12.70 9.57 12.80 38.80 153.30 199.20 46.30 20.50 7.20 27.70

75th percentile 3.59 3.00 2.24 1.88 2.20 4.83 11.60 33.40 55.70 17.30 6.86 3.59 14.20

50th percentile 1.85 1.77 1.54 1.22 1.38 3.29 5.99 16.60 16.10 6.36 3.07 1.46 6.83

25th percentile .95 1.21 .93 .62 .74 1.96 4.22 5.19 5.72 1.43 .64 .25 3.79

Minimum .00 .00 .00 .00 .00 .46 1.49 1.24 .22 .04 .00 .00 .69

Table 19. Monthly and annual streamflow data for Spring Creek above Sheridan Lake (station 06406920), water years 1991–2004.

Water year

Streamflow, in cubic feet per second

Month

Annual

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

1991 2.61 3.32 2.28 2.42 2.16 5.56 10.40 73.70 121.20 26.90 13.00 6.12 22.50

1992 5.35 6.60 4.94 2.50 3.22 7.02 7.20 5.64 8.14 11.20 7.05 3.70 6.06

1993 3.00 2.37 1.62 1.80 2.30 9.48 17.60 71.30 107.70 45.20 22.80 12.70 24.90

1994 13.80 12.20 9.42 6.01 6.24 16.90 15.90 34.40 14.70 5.75 2.78 1.54 11.70

1995 5.92 4.53 4.05 3.47 3.69 8.65 7.29 144.50 184.70 59.00 22.80 13.80 38.70

1996 12.90 9.89 6.85 5.10 8.99 13.00 23.40 90.40 121.30 31.50 20.90 17.40 30.10

1997 18.00 25.00 19.50 16.00 14.50 21.50 41.80 121.00 135.00 51.90 50.10 26.20 45.20

1998 19.30 11.40 9.98 5.99 6.91 20.40 30.80 32.70 95.60 63.30 40.00 26.00 30.30

1999 35.80 51.20 34.80 21.90 19.20 21.80 64.20 95.70 151.20 54.90 35.60 22.00 50.70

2000 16.40 12.80 9.51 7.85 10.00 11.70 22.30 32.50 16.30 9.21 4.15 3.19 13.00

2001 4.83 5.74 3.90 3.37 3.56 7.91 17.20 15.60 20.60 27.00 12.30 7.45 10.80

2002 7.80 6.42 3.65 1.84 2.27 4.66 13.70 17.20 10.30 3.94 3.87 5.91 6.81

2003 4.28 3.63 2.28 1.16 2.54 8.34 16.30 34.40 19.60 5.75 5.01 3.50 8.92

2004 2.59 3.13 1.89 1.01 1.21 5.50 5.38 4.12 2.21 2.92 2.19 1.32 2.80

Statistical summary

Number of values 14 14 14 14 14 14 14 14 14 14 14 14 14

Mean 10.90 11.30 8.19 5.74 6.20 11.60 20.96 55.23 72.04 28.46 17.33 10.77 21.61

Maximum 35.80 51.20 34.80 21.90 19.20 21.80 64.20 144.50 184.70 63.30 50.10 26.20 50.70

75th percentile 15.75 12.00 9.49 6.01 8.47 15.93 23.13 86.23 121.28 50.23 22.80 16.50 30.25

50th percentile 6.86 6.51 4.50 3.42 3.63 9.07 16.75 34.40 58.10 26.95 12.65 6.79 17.75

25th percentile 4.42 3.86 2.62 1.99 2.36 7.24 11.23 21.03 15.10 6.62 4.37 3.55 9.39

Minimum 2.59 2.37 1.62 1.01 1.21 4.66 5.38 4.12 2.21 2.92 2.19 1.32 2.80
40 Hydrologic Characterization for Spring Creek and Hydrologic Budget and Model Scenarios for Sheridan Lake, S. Dak.

Table 20. Monthly and annual streamflow data for Spring Creek near Keystone (station 06407500), water years 1987–2006.

Water year

Streamflow, in cubic feet per second

Month

Annual

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

1987 15.70 8.10 5.00 4.15 4.04 24.00 24.00 31.00 19.90 7.89 3.33 0.74 12.40

1988 .30 .35 .22 .18 .80 4.54 5.29 8.18 1.58 .05 .02 .00 1.80

1989 .00 .01 .08 .10 .01 .74 3.47 5.11 1.61 .16 .00 .49 .98

1990 .37 1.01 1.23 1.08 1.13 3.17 11.40 26.90 35.80 13.00 7.41 1.58 8.69

1991 1.87 3.28 1.94 1.58 3.34 6.53 15.10 84.40 146.70 44.00 20.40 6.25 28.00

1992 6.25 7.31 5.85 4.57 5.40 10.80 8.67 6.49 10.30 13.70 7.25 2.81 7.46

1993 1.49 3.19 2.69 3.13 3.64 11.30 21.90 97.20 146.00 70.70 32.50 17.50 34.40

1994 17.60 11.10 6.65 7.03 6.64 19.90 19.70 41.20 18.70 5.81 2.65 1.70 13.30

1995 8.73 7.84 5.96 4.75 4.40 12.70 8.90 210.60 292.40 95.80 30.00 15.70 58.30

1996 16.40 16.90 11.20 7.57 11.40 18.40 30.50 106.60 190.50 39.00 23.00 20.10 40.90

1997 22.90 31.20 21.40 19.70 16.30 24.00 45.70 176.80 190.20 63.80 67.00 32.50 59.50

1998 28.00 12.80 11.30 6.89 7.34 22.30 35.50 37.00 104.20 79.10 46.60 27.10 35.00

1999 42.10 63.80 43.60 29.70 22.60 25.20 76.90 124.80 188.90 83.90 48.90 25.40 64.70

2000 17.50 14.30 11.00 8.86 11.30 14.60 31.30 46.70 23.10 13.40 4.21 1.71 16.50

2001 5.61 8.16 5.62 4.71 4.93 10.50 21.60 20.20 27.50 32.30 14.10 8.37 13.70

2002 6.80 5.93 4.23 2.72 3.24 5.95 17.40 21.50 11.40 3.40 1.70 5.12 7.45

2003 4.29 3.80 2.75 2.25 4.01 13.30 15.40 41.80 24.50 7.10 2.84 1.74 10.40

2004 1.51 2.58 2.05 1.97 2.75 8.26 6.14 5.10 2.31 1.22 .47 .03 2.87

2005 .03 .06 .29 .46 1.59 2.51 4.97 9.26 8.94 2.35 2.30 .04 2.73

2006 .02 .06 .09 .93 1.16 5.73 10.90 7.87 6.57 .97 .00 .00 2.85

Statistical summary

Number of values 20 20 20 20 20 20 20 20 20 20 20 20 20

Mean 9.87 10.09 7.16 5.62 5.80 12.22 20.74 55.44 72.56 28.88 15.73 8.44 21.10

Maximum 42.10 63.80 43.60 29.70 22.60 25.20 76.90 210.60 292.40 95.80 67.00 32.50 64.70

75th percentile 16.68 11.53 7.74 6.93 6.82 18.78 25.63 87.60 146.18 48.95 24.75 16.15 34.55

50th percentile 5.93 6.62 4.62 3.64 4.03 11.05 16.40 34.00 23.80 13.20 5.73 2.28 12.85

25th percentile 1.21 2.19 1.76 1.46 2.46 5.90 8.84 8.99 9.96 3.14 2.15 .67 6.31

Minimum .00 .01 .08 .10 .01 .74 3.47 5.10 1.58 .05 .00 .00 .98

Table 21. Monthly and annual streamflow data for Boxelder Creek near Nemo (station 06422500), water years 1967–2006.—Continued

Water year

Streamflow, in cubic feet per second

Month

Annual

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

1967 6.62 5.14 3.54 3.38 5.00 15.00 17.20 39.00 157.30 48.10 19.20 13.50 27.70

1968 11.10 9.77 5.90 6.89 7.40 9.42 10.10 9.74 14.80 8.24 5.60 5.49 8.70

1969 3.97 4.49 2.74 1.78 2.40 5.17 18.30 23.70 13.30 16.10 6.38 3.70 8.55

1970 5.30 5.70 3.41 2.65 3.37 5.26 30.90 77.30 77.90 23.30 19.30 9.61 22.10

1971 7.73 9.04 6.39 3.51 10.00 11.00 84.40 93.70 64.70 23.30 10.50 10.90 27.90

1972 10.70 9.75 5.31 3.78 3.05 11.80 11.40 22.50 488.70 57.50 29.20 14.00 55.10
Appendix 41

Table 21. Monthly and annual streamflow data for Boxelder Creek near Nemo (station 06422500), water years 1967–2006.—Continued

Water year

Streamflow, in cubic feet per second

Month

Annual

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

1973 12.70 9.47 7.11 7.95 7.71 9.00 40.10 57.00 29.10 15.60 10.20 8.33 17.90

1974 7.71 7.77 6.30 5.87 5.99 8.30 9.31 6.20 4.09 3.84 3.48 2.96 5.98

1975 3.14 3.88 2.71 2.45 2.14 5.31 32.10 50.20 39.10 24.50 11.10 4.94 15.20

1976 5.49 5.49 6.12 5.49 9.05 9.59 14.20 20.60 114.30 36.30 14.00 9.26 20.70

1977 7.43 6.34 6.42 5.73 6.02 10.90 86.70 49.10 20.40 10.20 7.89 7.34 18.70

1978 8.86 5.96 4.75 4.03 3.71 14.50 16.20 125.60 33.40 19.90 15.70 9.41 22.00

1979 8.19 7.89 6.39 4.19 6.02 12.40 13.30 8.63 7.32 10.30 7.05 4.09 7.99

1980 3.80 3.92 3.46 2.28 3.44 7.50 12.80 10.70 7.47 3.45 3.10 2.92 5.40

1981 3.15 3.22 4.70 4.21 3.39 2.66 3.03 7.08 6.45 5.75 3.05 2.86 4.14

1982 3.06 2.79 2.02 1.42 2.12 5.97 6.79 43.60 27.40 14.20 11.10 8.57 10.80

1983 26.80 22.30 10.50 8.50 9.47 17.60 50.40 76.50 36.10 19.00 9.88 6.55 24.50

1984 7.90 7.10 5.27 6.52 7.66 9.86 20.50 71.00 72.10 35.50 23.20 11.70 23.20

1985 8.70 7.74 7.79 5.17 3.72 15.00 11.30 7.31 5.22 2.67 2.11 2.31 6.61

1986 3.39 2.59 2.25 3.45 6.36 11.20 25.60 33.90 24.30 14.80 8.16 11.20 12.30

1987 11.90 8.40 5.73 3.34 7.23 15.00 29.10 16.90 12.20 5.78 3.28 3.93 10.20

1988 4.46 4.59 3.40 1.72 2.03 7.29 11.60 11.70 3.92 1.70 1.65 1.17 4.61

1989 1.85 1.66 1.65 1.60 1.36 7.64 6.46 12.00 6.41 2.58 .76 1.51 3.81

1990 1.88 2.56 2.57 3.14 3.79 10.10 13.50 15.30 7.60 3.25 2.11 1.52 5.62

1991 2.07 2.33 1.65 1.64 1.44 4.45 10.60 39.40 64.30 16.40 8.80 8.91 13.50

1992 7.25 8.05 7.39 6.64 5.80 8.58 8.28 6.58 8.91 7.69 3.79 3.62 6.88

1993 3.02 3.88 2.64 3.05 3.83 11.90 18.70 64.20 90.00 49.70 22.10 13.40 24.00

1994 12.40 8.59 5.19 7.29 8.35 23.00 43.80 63.40 24.00 13.00 6.56 5.25 18.50

1995 11.00 9.79 7.40 7.17 7.60 13.40 12.40 274.90 168.60 58.10 26.50 15.70 51.40

1996 16.80 14.10 9.71 7.75 8.94 31.80 61.80 133.70 149.60 34.80 23.90 21.60 42.90

1997 24.50 28.90 17.40 16.40 18.20 44.50 148.80 175.60 136.20 54.40 51.30 40.00 63.10

1998 26.70 23.50 18.80 15.40 7.19 22.40 63.10 27.40 78.00 53.20 57.00 24.70 34.90

1999 71.10 64.10 37.70 26.40 17.30 22.60 84.30 84.30 142.50 64.60 37.70 21.60 56.30

2000 15.90 15.00 14.80 12.10 12.50 14.40 38.00 63.30 34.60 19.50 11.50 9.12 21.70

2001 9.19 11.80 8.79 8.27 8.18 12.50 26.30 20.00 15.90 12.80 9.85 7.33 12.60

2002 6.66 5.53 4.90 3.35 3.29 4.10 14.50 10.90 5.53 3.25 3.04 4.11 5.77

2003 4.26 3.74 3.41 4.01 3.78 14.80 12.80 26.60 17.20 7.76 4.29 3.74 8.90

2004 3.40 3.53 3.83 3.20 3.77 7.43 5.79 4.51 3.44 3.46 1.38 1.15 3.74

2005 1.68 2.24 1.77 1.94 2.68 3.46 4.31 7.24 7.66 4.11 2.90 1.49 3.46

2006 2.09 2.07 1.62 1.51 1.62 3.45 25.40 36.10 14.20 4.31 3.81 4.74 8.43

Statistical summary

Number of values 40 40 40 40 40 40 40 40 40 40 40 40 40

Mean 9.85 9.12 6.59 5.63 5.92 12.01 28.85 48.18 55.86 20.32 12.56 8.61 18.64

Maximum 71.10 64.10 37.70 26.40 18.20 44.50 148.80 274.90 488.70 64.60 57.00 40.00 63.10

75th percentile 11.03 9.54 7.18 6.96 7.67 14.58 33.58 63.60 73.55 27.08 16.58 10.98 23.40

50th percentile 7.34 6.15 5.23 4.02 5.40 10.50 16.70 30.65 24.15 14.50 8.48 6.94 13.05

25th percentile 3.40 3.85 3.24 2.95 3.35 7.40 11.38 11.50 7.65 5.39 3.43 3.68 6.81

Minimum 1.68 1.66 1.62 1.42 1.36 2.66 3.03 4.51 3.44 1.70 .76 1.15 3.46
42 Hydrologic Characterization for Spring Creek and Hydrologic Budget and Model Scenarios for Sheridan Lake, S. Dak.

Table 22. Actual and extrapolated monthly and annual streamflow values for Spring Creek above Sheridan Lake (station 06406920), 

water years 1962–2006.—Continued

[Shaded cells indicate extrapolated values. Unshaded cells indicate actual record]

Water year

Streamflow, in cubic feet per second

Month

Annual

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

1962 0.00 0.27 0.07 0.00 0.14 1.08 4.60 53.49 119.84 95.81 30.51 8.81 26.35

1963 12.90 6.62 3.99 2.18 3.53 14.42 31.79 35.90 157.19 49.47 14.52 13.50 28.79

1964 8.94 6.46 4.23 3.31 4.99 5.49 10.98 21.45 54.10 58.05 15.05 5.08 16.58

1965 5.19 3.32 2.54 2.24 1.75 2.52 8.99 90.14 167.37 92.28 28.48 11.25 34.80

1966 12.09 7.43 5.85 3.21 2.39 9.13 19.73 11.81 3.69 4.73 12.30 6.88 8.31

1967 5.67 5.67 3.13 3.02 2.92 10.94 12.69 16.79 240.50 40.16 14.77 10.78 30.41

1968 8.86 5.58 3.52 3.52 4.02 7.68 8.69 6.24 30.86 6.46 13.13 4.25 8.56

1969 3.65 3.36 2.57 1.84 1.30 4.87 13.26 6.48 14.76 12.93 15.23 2.82 6.95

1970 4.68 4.12 1.81 2.00 2.56 4.93 19.24 28.97 75.77 18.96 13.36 7.58 15.31

1971 6.49 7.28 1.24 1.47 2.04 8.64 39.27 94.21 110.35 18.96 8.94 8.64 25.65

1972 8.59 4.99 3.20 1.20 1.16 9.11 9.48 22.76 363.03 48.31 21.10 11.19 41.74

1973 9.96 6.27 3.15 2.82 2.06 7.42 23.15 38.02 25.11 12.52 16.31 6.54 12.84

1974 6.47 5.52 2.01 1.54 2.06 6.98 8.21 6.46 3.33 2.93 2.65 2.24 4.21

1975 2.98 3.32 .27 1.84 1.60 4.97 19.77 18.49 39.36 19.97 10.38 3.81 10.57

1976 4.83 4.58 2.83 2.34 3.11 7.79 11.08 69.51 133.15 30.01 11.19 7.29 23.98

1977 6.27 3.74 2.94 1.29 2.43 8.58 40.03 7.98 3.08 8.06 12.16 5.74 8.52

1978 7.30 4.21 2.81 1.23 1.66 10.66 12.16 114.77 47.29 16.11 12.70 7.42 20.03

1979 6.82 6.41 1.98 .96 1.40 9.47 10.57 5.97 8.94 8.14 5.50 3.13 5.79

1980 3.51 6.06 3.81 .79 1.66 6.46 10.29 10.16 7.35 2.62 6.70 2.21 5.15

1981 2.99 3.32 4.31 1.68 1.15 2.94 3.70 63.41 11.64 4.45 13.51 2.16 9.72

1982 2.92 2.76 1.49 .91 2.35 5.43 6.56 32.13 59.25 11.36 11.27 6.73 11.93

1983 18.97 5.83 3.48 2.21 2.47 12.35 27.23 27.72 15.45 15.35 7.80 5.10 12.06

1984 6.61 3.32 2.22 3.08 2.92 7.95 14.37 35.63 95.00 29.32 11.77 9.29 18.45

1985 7.18 6.30 1.35 1.34 2.84 10.94 9.42 3.01 4.03 2.01 1.58 1.73 4.31

1986 3.18 2.28 1.24 2.52 2.82 8.76 16.83 27.30 27.52 11.85 6.97 8.88 10.03

1987 13.15 6.98 4.20 2.97 2.67 20.01 19.73 24.78 16.12 8.08 4.99 .91 10.44

1988 .63 .36 .18 .26 .35 3.05 4.33 6.85 1.45 .14 .04 .86 1.55

1989 1.89 .02 .13 .16 .02 6.55 2.83 4.35 1.47 .35 .55 .63 1.60

1990 .74 .98 1.03 .69 .54 2.03 9.35 21.61 28.20 12.07 8.74 1.76 7.34

1991 2.61 3.32 2.28 2.42 2.16 5.56 10.40 73.70 121.20 26.90 13.00 6.12 22.50

1992 5.35 6.60 4.94 2.50 3.22 7.02 7.20 5.64 8.14 11.20 7.05 3.70 6.07

1993 3.00 2.37 1.62 1.80 2.30 9.48 17.60 71.30 107.70 45.20 22.80 12.70 24.90

1994 13.80 12.20 9.42 6.01 6.24 16.90 15.90 34.40 14.70 5.75 2.78 1.54 11.69

1995 5.92 4.53 4.05 3.47 3.69 8.65 7.29 144.50 184.70 59.00 22.80 13.80 38.67

1996 12.90 9.89 6.85 5.10 8.99 13.00 23.40 90.40 121.30 31.50 20.90 17.40 30.17

1997 18.00 25.00 19.50 16.00 14.50 21.50 41.80 121.00 135.00 51.90 50.10 26.20 45.16

1998 19.30 11.40 9.98 5.99 6.91 20.40 30.80 32.70 95.60 63.30 40.00 26.00 30.27

1999 35.80 51.20 34.80 21.90 19.20 21.80 64.20 95.70 151.20 54.90 35.60 22.00 50.72

2000 16.40 12.80 9.51 7.85 10.00 11.70 22.30 32.50 16.30 9.21 4.15 3.19 13.01

2001 4.83 5.74 3.90 3.37 3.56 7.91 17.20 15.60 20.60 27.00 12.30 7.45 10.83
Appendix 43

Table 22. Actual and extrapolated monthly and annual streamflow values for Spring Creek above Sheridan Lake (station 06406920), 

water years 1962–2006.—Continued

[Shaded cells indicate extrapolated values. Unshaded cells indicate actual record]

Water year

Streamflow, in cubic feet per second

Month

Annual

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

2002 7.80 6.42 3.65 1.84 2.27 4.66 13.70 17.20 10.30 3.94 3.87 5.91 6.81

2003 4.28 3.63 2.28 1.16 2.54 8.34 16.30 34.40 19.60 5.75 5.01 3.50 8.93

2004 2.59 3.13 1.89 1.01 1.21 5.50 5.38 4.12 2.21 2.92 2.19 1.32 2.80

2005 1.74 .10 .24 .60 .83 1.56 4.06 7.73 7.53 3.06 3.86 .07 2.63

2006 2.10 .10 .64 .59 .56 3.97 8.94 6.60 5.61 1.50 2.91 3.65 3.10

Statistical summary

Number of values 45 45 45 45 45 45 45 45 45 45 45 45 45

Mean 7.55 6.35 4.16 2.98 3.31 8.65 16.33 37.64 64.15 23.21 12.92 7.15 16.23

Maximum 35.80 51.20 34.80 21.90 19.20 21.80 64.20 144.50 363.03 95.81 50.10 26.20 50.72

75th percentile 8.94 6.46 4.05 3.08 3.22 10.66 19.73 53.49 110.35 31.50 15.05 8.88 24.90

50th percentile 5.92 4.99 2.83 2.00 2.39 7.91 12.69 27.30 27.52 12.52 11.77 5.91 11.69

25th percentile 3.00 3.32 1.62 1.20 1.60 5.43 8.94 7.98 8.94 5.75 5.01 2.82 6.95

Minimum .00 .02 .07 .00 .02 1.08 2.83 3.01 1.45 .14 .04 .07 1.55
44 Hydrologic Characterization for Spring Creek and Hydrologic Budget and Model Scenarios for Sheridan Lake, S. Dak.

Table 23. Monthly and annual precipitation for Sheridan Lake, 1962–2006.—Continued

[Values were derived by using the mean of monthly data for three National Weather Service (NWS) stations (table 1; Hill City, Mt. Rushmore National Memorial, and Pactola Dam). Shading indicates that one of three monthly NWS precipitation values was missing. For gray shading, estimates for the NWS stations 

were obtained from Driscoll and others (2000) and were used in deriving the values for Sheridan Lake. For red shading, estimated values from Driscoll and 

others (2000) were not available, and values for Sheridan Lake were estimated by using the mean of two NWS stations]

Year

Precipitation, in inches

Month

Annual

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

1962 0.33 0.97 0.61 0.68 10.14 7.19 6.47 1.22 1.16 1.53 0.26 0.04 30.58

1963 .44 .42 1.46 5.00 2.02 7.31 3.09 1.17 3.09 .95 .11 .30 25.35

1964 .41 .42 .64 1.42 3.59 6.19 2.60 1.49 1.23 .04 .37 1.68 20.06

1965 .64 .19 .55 1.50 9.68 5.82 4.29 2.55 1.85 .14 .16 .34 27.70

1966 .15 .67 .91 3.05 .13 .97 4.48 3.82 2.45 .95 .48 .70 18.76

1967 .19 .50 .48 2.81 3.45 7.53 1.71 1.48 1.28 .36 .33 .46 20.57

1968 .59 .22 .28 1.05 2.38 5.71 1.59 2.86 1.28 .12 .34 .54 16.97

1969 .23 1.17 .50 1.80 2.43 3.92 6.21 .99 .73 1.37 .32 .13 19.81

1970 .24 .35 1.51 3.31 4.37 3.67 2.10 2.53 1.34 1.20 .64 .58 21.85

1971 .82 .71 1.46 5.98 5.71 3.40 1.70 1.17 2.52 1.73 .98 .23 26.42

1972 .25 .30 .69 1.95 2.92 10.72 3.22 3.13 .51 .75 .32 .31 25.07

1973 .09 .27 3.42 3.67 1.63 2.45 3.69 1.19 1.80 .74 1.22 .58 20.76

1974 .41 .18 .24 1.03 1.68 1.05 3.98 1.42 .93 2.15 .29 .12 13.47

1975 .72 .55 1.01 2.82 2.40 4.85 1.33 .88 .07 .47 .53 .80 16.43

1976 .25 .99 .34 4.37 3.74 6.12 3.61 2.02 1.12 .19 .47 .22 23.44

1977 .41 .29 2.00 1.68 1.54 3.11 4.01 2.67 1.94 .84 .68 .76 19.92

1978 .35 .74 .27 2.68 6.75 1.66 4.05 1.81 .57 .52 .76 .66 20.85

1979 .38 .43 .40 1.17 1.52 4.80 8.58 2.79 .19 .75 .30 .15 21.45

1980 .27 .37 .92 1.59 2.33 2.74 2.19 2.80 .76 1.94 .41 .43 16.75

1981 .05 .13 .23 .65 6.74 1.50 5.19 1.30 .39 2.33 .06 .73 19.30

1982 .53 .41 1.18 .87 5.82 4.08 3.17 2.31 2.57 2.14 .37 .52 23.98

1983 .32 .13 1.68 .95 2.80 3.39 1.29 2.88 .52 2.17 1.19 .56 17.89

1984 .13 .20 .57 3.62 1.97 5.17 4.83 1.34 1.12 .74 .80 .34 20.83

1985 .21 .07 1.02 1.10 1.04 1.23 2.08 1.20 2.10 .63 1.79 .69 13.17

1986 .11 1.20 .70 3.67 1.79 4.78 1.67 1.97 6.15 1.80 1.02 .01 24.87

1987 .07 1.64 1.71 .19 5.40 .64 1.67 2.75 .71 .73 .24 .35 16.09

1988 .29 .31 .78 .80 2.34 3.85 1.92 2.68 .26 .57 1.18 .24 15.22

1989 .05 .55 .93 1.75 2.00 2.00 1.85 2.81 4.68 .95 .34 .58 18.49

1990 .03 .57 1.51 2.06 4.80 1.65 4.61 1.63 1.14 .69 .54 .59 19.81

1991 .13 .63 .63 3.91 7.44 5.33 2.89 1.26 1.04 1.20 1.00 .00 25.44

1992 .07 .23 2.17 1.36 2.71 3.74 4.13 1.25 .63 .67 .32 .70 17.99

1993 .66 .82 .65 2.92 5.78 5.19 3.41 1.95 1.11 1.82 .40 .48 25.21

1994 .34 .63 .64 1.76 2.28 1.05 1.34 1.89 .72 4.81 .37 .46 16.29

1995 .04 .75 .90 2.39 8.03 5.24 4.28 1.28 1.45 2.75 .46 .15 27.72

1996 .93 .11 1.59 2.31 7.27 1.94 2.27 4.91 2.25 4.84 .40 1.06 29.88

1997 .28 .77 .35 3.05 5.25 3.16 5.16 2.54 2.06 1.09 .10 .33 24.14

1998 .57 .87 2.31 1.11 2.99 6.15 3.34 3.37 3.30 4.63 1.55 .11 30.29

1999 .90 .11 .99 3.43 2.59 7.74 2.99 2.90 1.32 .25 .23 .18 23.63

2000 .47 .29 1.07 4.59 3.14 2.15 3.03 .68 .67 1.64 1.38 .29 19.38
Appendix 45

Table 23. Monthly and annual precipitation for Sheridan Lake, 1962–2006.—Continued

[Values were derived by using the mean of monthly data for three National Weather Service (NWS) stations (table 1; Hill City, Mt. Rushmore National Memorial, and Pactola Dam). Shading indicates that one of three monthly NWS precipitation values was missing. For gray shading, estimates for the NWS stations 

were obtained from Driscoll and others (2000) and were used in deriving the values for Sheridan Lake. For red shading, estimated values from Driscoll and 

others (2000) were not available, and values for Sheridan Lake were estimated by using the mean of two NWS stations]

Year

Precipitation, in inches

Month

Annual

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

2001 0.28 0.99 0.76 2.48 2.68 4.16 4.58 2.79 1.74 1.51 0.63 0.08 22.68

2002 .15 .24 1.61 2.24 3.00 1.60 3.12 2.30 3.39 1.18 .34 .12 19.29

2003 .73 .56 1.95 3.29 1.94 2.47 .37 3.21 1.23 .48 1.26 .35 17.85

2004 .36 1.06 .48 1.57 2.43 1.54 2.86 1.33 2.46 .48 .19 .06 14.84

2005 .59 .22 .80 1.80 4.49 2.18 2.93 2.41 1.12 1.23 .24 .21 18.23

2006 .17 .43 2.37 1.93 3.30 2.37 1.13 3.18 2.02 .54 .70 .12 18.26

Statistical summary

Mean 0.35 0.53 1.05 2.30 3.74 3.86 3.22 2.14 1.58 1.30 0.58 0.41 21.04

Standard deviation .24 .35 .69 1.28 2.30 2.24 1.61 .90 1.18 1.14 .42 .32 4.42

Maximum .93 1.64 3.42 5.98 10.14 10.72 8.58 4.91 6.15 4.84 1.79 1.68 30.58

75th percentile .47 .74 1.51 3.05 5.25 5.24 4.13 2.79 2.06 1.73 .76 .58 24.14

50th percentile .29 .43 .90 1.95 2.92 3.67 3.09 2.02 1.23 .95 .40 .34 20.06

25th percentile .15 .24 .57 1.36 2.28 2.00 1.92 1.30 .73 .57 .32 .15 17.99

Minimum .03 .07 .23 .19 .13 .64 .37 .68 .07 .04 .06 .00 13.17
46 Hydrologic Characterization for Spring Creek and Hydrologic Budget and Model Scenarios for Sheridan Lake, S. Dak.

Table 24. Pan evaporation data for Pactola Dam and other selected stations, 1962–2006.—Continued

[Gray shading indicates estimates derived from the MOVE.1 analysis. Red shading indicates estimates derived from regression analysis with precipitation data. 

Blue shading indicates the “annual” total pan evaporation at Pactola Dam using measured and estimated data for May–October of each year. Unshaded values 

indicate measured data. --, no data]

Month and year

Evaporation data, in inches, for selected National Weather Service stations (station number)

Pactola Dam 

(396427)

Angostura 

Dam (390217) Oral (396304) Cottonwood (391972)

Shadehill Dam 

(397567)

Oahe Dam 

(396170)

Pickstown 

(396574)

May 1962 3.61 7.33 -- 7.03 -- -- 6.60

June 1962 4.23 7.38 -- 7.40 -- 6.84 5.68

July 1962 5.26 9.29 -- 8.31 -- 7.39 7.07

August 1962 4.97 9.23 -- 11.07 -- 9.11 7.55

September 1962 3.29 6.33 -- 7.89 -- 6.96 4.08

October 1962 2.44 4.07 -- 5.23 -- 4.20 2.54

Annual 1962 23.80

May 1963 4.37 7.12 -- 7.46 -- 7.93 6.86

June 1963 5.02 8.60 -- 9.15 -- 8.41 7.63

July 1963 5.89 10.96 -- 11.00 -- 11.58 9.35

August 1963 6.05 10.34 -- 11.94 -- 10.29 6.95

September 1963 3.13 5.94 -- 6.14 -- 5.39 3.99

October 1963 2.72 5.40 -- 6.10 -- 5.42 5.75

Annual 1963 27.18

May 1964 4.92 7.44 -- 8.36 -- 9.16 8.31

June 1964 4.52 7.69 -- 7.62 -- 7.62 8.05

July 1964 6.32 9.23 -- 11.02 -- 10.40 9.08

August 1964 6.24 9.95 -- 10.88 -- 10.07 7.33

September 1964 4.29 7.13 -- 7.95 -- 7.03 4.81

October 1964 3.00 .00 -- 6.11 -- 5.66 4.59

Annual 1964 29.29

May 1965 3.98 7.66 -- 7.19 -- 6.75 6.47

June 1965 4.95 7.50 -- 7.10 -- 8.24 6.48

July 1965 5.36 8.91 -- 8.81 -- 9.03 7.68

August 1965 4.84 8.52 -- 9.20 -- 9.11 7.88

September 1965 2.65 4.67 -- 4.98 -- 4.69 3.21

October 1965 3.10 4.44 -- .00 -- 4.76 2.89

Annual 1965 24.88

May 1966 5.51 8.31 -- 8.13 -- 8.05 7.52

June 1966 6.22 8.93 -- 10.52 -- 10.47 7.49

July 1966 7.96 12.70 -- 11.61 10.98 11.04 10.71

August 1966 5.45 7.86 -- 8.63 9.02 8.05 7.79

September 1966 3.71 6.09 -- 6.21 6.23 6.47 4.86

October 1966 2.19 4.28 -- .00 4.35 .00 4.09

Annual 1966 31.04
Appendix 47

Table 24. Pan evaporation data for Pactola Dam and other selected stations, 1962–2006.—Continued

[Gray shading indicates estimates derived from the MOVE.1 analysis. Red shading indicates estimates derived from regression analysis with precipitation data. 

Blue shading indicates the “annual” total pan evaporation at Pactola Dam using measured and estimated data for May–October of each year. Unshaded values 

indicate measured data. --, no data]

Month and year

Evaporation data, in inches, for selected National Weather Service stations (station number)

Pactola Dam 

(396427)

Angostura 

Dam (390217) Oral (396304) Cottonwood (391972)

Shadehill Dam 

(397567)

Oahe Dam 

(396170)

Pickstown 

(396574)

May 1967 3.71 5.83 -- 5.87 6.36 6.96 --

June 1967 3.73 6.45 -- 5.75 6.35 6.14 5.40

July 1967 6.30 9.50 -- 8.58 10.74 11.78 9.14

August 1967 5.80 10.48 -- 8.95 10.85 11.55 8.26

September 1967 3.81 7.20 -- 6.39 6.19 8.48 5.95

October 1967 3.14 5.78 -- -- 3.90 5.49 3.89

Annual 1967 26.49

May 1968 3.93 6.81 -- 6.22 6.95 6.96 6.06

June 1968 5.80 10.13 -- 7.46 7.43 8.78 8.08

July 1968 6.62 10.70 -- 8.67 9.16 10.11 9.31

August 1968 5.72 8.94 -- 8.37 8.75 8.68 8.86

September 1968 3.88 7.03 -- 7.11 6.17 6.81 5.15

October 1968 3.73 5.48 -- -- 4.48 5.11 3.22

Annual 1968 29.68

May 1969 5.55 8.76 -- 7.41 7.86 8.69 7.13

June 1969 4.27 8.22 -- 7.54 7.54 8.11 6.87

July 1969 7.00 11.42 -- 10.14 8.38 9.21 8.44

August 1969 7.24 11.79 -- 11.41 11.15 13.15 9.01

September 1969 5.13 8.40 -- 8.55 7.47 8.91 5.40

October 1969 1.92 .00 -- -- 3.26 -- --

Annual 1969 31.11

May 1970 4.72 8.20 -- 6.89 -- 7.30 6.88

June 1970 6.96 10.98 -- 9.60 8.55 10.12 8.63

July 1970 7.54 12.16 -- 10.66 9.89 13.04 9.67

August 1970 6.79 11.10 -- 10.88 10.31 10.66 7.81

September 1970 4.06 7.30 -- 7.54 7.08 8.68 5.94

October 1970 2.27 .00 -- -- 3.79 4.26 4.02

Annual 1970 32.34

May 1971 4.13 -- -- 6.82 6.81 7.26 6.46

June 1971 5.42 -- 7.26 7.84 7.69 8.37 8.03

July 1971 6.31 -- 8.17 10.11 9.45 11.89 8.27

August 1971 6.49 -- 8.84 11.15 10.34 12.83 9.58

September 1971 3.77 -- 4.76 7.06 5.92 6.72 5.55

October 1971 2.19 -- -- -- 3.73 5.22 4.68

Annual 1971 28.31
48 Hydrologic Characterization for Spring Creek and Hydrologic Budget and Model Scenarios for Sheridan Lake, S. Dak.

Table 24. Pan evaporation data for Pactola Dam and other selected stations, 1962–2006.—Continued

[Gray shading indicates estimates derived from the MOVE.1 analysis. Red shading indicates estimates derived from regression analysis with precipitation data. 

Blue shading indicates the “annual” total pan evaporation at Pactola Dam using measured and estimated data for May–October of each year. Unshaded values 

indicate measured data. --, no data]

Month and year

Evaporation data, in inches, for selected National Weather Service stations (station number)

Pactola Dam 

(396427)

Angostura 

Dam (390217) Oral (396304) Cottonwood (391972)

Shadehill Dam 

(397567)

Oahe Dam 

(396170)

Pickstown 

(396574)

May 1972 3.93 -- -- -- 6.37 7.21 5.71

June 1972 5.41 -- 7.49 8.48 7.93 7.84 6.85

July 1972 5.36 -- 7.74 9.15 9.14 8.61 8.21

August 1972 4.93 -- 7.54 8.73 7.21 9.70 7.28

September 1972 3.80 -- 6.12 -- 6.63 8.84 5.10

October 1972 2.04 -- -- 4.61 3.46 4.06 --

Annual 1972 25.47

May 1973 4.47 -- 6.88 -- 8.04 8.55 7.53

June 1973 6.95 -- 9.74 10.08 9.07 11.22 8.41

July 1973 7.37 -- 10.29 -- 10.78 13.25 8.59

August 1973 5.54 -- 8.64 -- 9.10 11.90 9.06

September 1973 3.12 -- 4.66 -- -- 5.48 3.42

October 1973 2.38 -- -- -- 3.95 4.50 3.29

Annual 1973 29.83

May 1974 3.60 -- 6.24 -- 5.48 6.72 6.08

June 1974 6.27 -- 8.90 -- 8.68 10.17 8.62

July 1974 7.69 -- 10.70 -- 10.60 11.15

August 1974 5.69 -- 8.58 -- 7.68 11.09 7.51

September 1974 3.84 -- -- -- 6.31 7.93 6.19

October 1974 2.75 -- -- -- 4.51 5.05 4.68

Annual 1974 29.84

May 1975 4.39 -- -- -- -- 7.58 6.86

June 1975 5.21 -- 7.47 -- 5.93 8.26 7.83

July 1975 7.25 -- 10.14 -- 9.50 12.59 10.88

August 1975 6.03 -- 8.62 -- -- 8.77 7.58

September 1975 3.90 -- 6.38 -- 6.39 6.73 5.68

October 1975 2.20 -- -- -- 3.69 4.87 5.01

Annual 1975 28.98

May 1976 5.28 -- -- 8.23 7.91 8.76 7.31

June 1976 5.87 -- 9.08 10.57 9.61 13.30 9.70

July 1976 6.19 -- 9.30 10.80 9.88 14.50 10.90

August 1976 5.46 -- 8.25 11.45 9.63 13.91 10.14

September 1976 4.22 -- 6.98 10.03 6.77 9.94 6.70

October 1976 2.86 -- -- 6.07 4.14 -- 3.35

Annual 1976 29.88
Appendix 49

Table 24. Pan evaporation data for Pactola Dam and other selected stations, 1962–2006.—Continued

[Gray shading indicates estimates derived from the MOVE.1 analysis. Red shading indicates estimates derived from regression analysis with precipitation data. 

Blue shading indicates the “annual” total pan evaporation at Pactola Dam using measured and estimated data for May–October of each year. Unshaded values 

indicate measured data. --, no data]

Month and year

Evaporation data, in inches, for selected National Weather Service stations (station number)

Pactola Dam 

(396427)

Angostura 

Dam (390217) Oral (396304) Cottonwood (391972)

Shadehill Dam 

(397567)

Oahe Dam 

(396170)

Pickstown 

(396574)

May 1977 6.04 -- -- 9.13 -- 9.47 6.13

June 1977 6.57 -- 9.02 8.80 -- 10.53 7.68

July 1977 6.83 -- 9.58 11.32 -- 11.09 8.42

August 1977 4.56 -- 6.50 9.16 -- 8.01 6.20

September 1977 4.69 -- -- 9.71 -- 6.78 4.94

October 1977 1.82 -- -- -- -- 3.27 2.48

Annual 1977 30.51

May 1978 4.13 -- -- 6.82 -- 6.75 5.41

June 1978 6.07 -- 8.45 8.31 -- 8.46 7.01

July 1978 7.57 -- 9.80 10.01 -- 9.76 7.81

August 1978 5.39 -- 7.96 9.43 -- 10.52 7.20

September 1978 5.34 -- 6.09 9.00 -- 9.41 6.52

October 1978 3.07 -- -- -- -- 5.43 3.93

Annual 1978 31.57

May 1979 4.35 -- 6.88 -- -- 7.20 5.68

June 1979 5.43 -- 8.49 8.88 -- 8.86 6.51

July 1979 6.40 -- 8.54 8.20 -- 8.80 6.36

August 1979 4.43 -- 6.59 7.95 -- 7.56 6.00

September 1979 4.46 -- 6.09 10.37 -- 8.62 6.30

October 1979 2.65 -- -- 5.70 -- -- --

Annual 1979 27.72

May 1980 4.88 -- 7.40 -- -- 9.54 5.93

June 1980 6.01 -- 8.48 9.97 -- 11.01 7.60

July 1980 7.52 -- 10.73 12.63 -- 11.46 9.27

August 1980 5.97 -- 8.76 9.79 -- 9.46 7.50

September 1980 4.18 -- 5.63 9.19 -- 7.66 5.33

October 1980 3.72 -- -- -- -- 6.55 4.51

Annual 1980 32.28

May 1981 3.71 -- 6.13 -- -- 6.10 5.56

June 1981 5.27 -- 8.69 -- -- 9.05 7.14

July 1981 6.16 -- 8.40 9.81 -- 10.06 7.92

August 1981 4.69 -- 5.92 7.98 -- 8.28 7.03

September 1981 4.32 -- -- 9.01 -- 7.64 5.71

October 1981 2.49 -- -- -- -- -- --

Annual 1981 26.64
50 Hydrologic Characterization for Spring Creek and Hydrologic Budget and Model Scenarios for Sheridan Lake, S. Dak.

Table 24. Pan evaporation data for Pactola Dam and other selected stations, 1962–2006.—Continued

[Gray shading indicates estimates derived from the MOVE.1 analysis. Red shading indicates estimates derived from regression analysis with precipitation data. 

Blue shading indicates the “annual” total pan evaporation at Pactola Dam using measured and estimated data for May–October of each year. Unshaded values 

indicate measured data. --, no data]

Month and year

Evaporation data, in inches, for selected National Weather Service stations (station number)

Pactola Dam 

(396427)

Angostura 

Dam (390217) Oral (396304) Cottonwood (391972)

Shadehill Dam 

(397567)

Oahe Dam 

(396170)

Pickstown 

(396574)

May 1982 4.71 -- -- 7.72 -- 6.08 5.49

June 1982 4.43 -- 6.82 6.86 -- 7.20 6.35

July 1982 5.77 -- 8.34 9.71 -- 9.13 7.19

August 1982 4.66 -- 7.11 8.65 -- 9.11 6.51

September 1982 2.90 -- -- 6.21 -- 7.07 4.28

October 1982 2.30 -- -- -- -- 3.29 --

Annual 1982 24.77

May 1983 3.83 -- 6.86 -- -- 7.06 --

June 1983 4.58 -- 6.37 7.72 -- 8.21 6.06

July 1983 7.24 -- 9.77 11.77 -- 11.23 8.11

August 1983 5.80 -- 7.83 11.48 -- 11.69 8.04

September 1983 4.38 -- 5.77 9.45 -- 7.66 6.01

October 1983 1.49 -- -- 3.54 -- 3.34 2.97

Annual 1983 27.32

May 1984 4.17 -- -- -- -- 7.26 5.68

June 1984 5.16 -- 7.05 7.96 -- 7.75 6.99

July 1984 5.91 -- 9.21 10.61 -- 10.00 7.46

August 1984 6.00 -- 8.57 11.64 -- 10.92 6.98

September 1984 4.21 -- 5.60 7.75 -- 6.45 4.34

October 1984 2.07 -- -- -- -- -- 2.94

Annual 1984 27.52

May 1985 5.48 -- 7.69 -- -- 8.23 6.34

June 1985 5.71 -- 8.46 9.20 -- 8.14 6.84

July 1985 7.31 -- 10.09 13.01 -- 11.79 8.15

August 1985 5.53 -- 7.91 9.47 -- 8.24 5.21

September 1985 4.03 -- -- 8.04 -- 5.62 3.80

October 1985 2.63 -- -- -- -- -- --

Annual 1985 30.69

May 1986 5.00 -- -- -- -- 7.46 6.67

June 1986 6.06 -- 9.01 -- -- 8.58 7.70

July 1986 5.77 -- 9.52 -- -- 10.35 8.22

August 1986 5.70 -- 7.64 -- -- 8.89 8.72

September 1986 2.45 -- 3.77 -- -- 4.01 3.53

October 1986 1.49 -- -- -- -- 2.69 2.71

Annual 1986 26.47
Appendix 51

Table 24. Pan evaporation data for Pactola Dam and other selected stations, 1962–2006.—Continued

[Gray shading indicates estimates derived from the MOVE.1 analysis. Red shading indicates estimates derived from regression analysis with precipitation data. 

Blue shading indicates the “annual” total pan evaporation at Pactola Dam using measured and estimated data for May–October of each year. Unshaded values 

indicate measured data. --, no data]

Month and year

Evaporation data, in inches, for selected National Weather Service stations (station number)

Pactola Dam 

(396427)

Angostura 

Dam (390217) Oral (396304) Cottonwood (391972)

Shadehill Dam 

(397567)

Oahe Dam 

(396170)

Pickstown 

(396574)

May 1987 3.69 -- -- -- -- 7.52 6.96

June 1987 5.98 -- 8.09 8.91 -- 10.20 8.04

July 1987 6.46 -- 9.35 11.54 -- 12.62 9.70

August 1987 5.17 -- 7.38 9.78 -- 8.78 6.57

September 1987 3.90 -- 5.48 9.25 -- 6.95 5.15

October 1987 2.71 -- -- -- -- -- 3.81

Annual 1987 27.91

May 1988 5.33 -- -- -- -- 9.57 8.23

June 1988 8.14 -- 9.52 11.94 -- 13.07 9.35

July 1988 7.69 -- 9.25 10.84 -- 13.68 8.13

August 1988 6.70 -- 7.99 12.30 -- 11.48 8.60

September 1988 4.54 -- 5.44 8.74 -- 7.06 6.02

October 1988 2.95 -- -- -- -- 5.23 3.02

Annual 1988 35.35

May 1989 5.03 -- -- -- -- 8.48 6.40

June 1989 4.79 -- 7.20 9.32 -- 10.41 7.60

July 1989 6.89 -- 9.92 12.78 -- 13.45 9.49

August 1989 5.76 -- 8.26 12.41 -- 11.88 7.69

September 1989 4.21 -- -- 7.61 -- 7.86 5.77

October 1989 2.86 -- -- -- -- 4.02

Annual 1989 29.54

May 1990 3.20 -- -- -- -- 7.07 5.36

June 1990 5.79 -- 7.83 9.33 -- -- 7.83

July 1990 6.43 -- 7.91 10.84 -- 9.29 7.37

August 1990 4.96 -- 7.74 9.67 -- -- 7.62

September 1990 3.91 -- -- 10.61 -- 7.89 7.96

October 1990 3.50 -- -- -- -- -- 4.88

Annual 1990 27.79

May 1991 4.54 -- -- 7.33 -- 7.47 --

June 1991 5.02 -- 7.47 6.96 -- 7.29 8.90

July 1991 6.15 -- 8.18 10.79 -- 12.29 10.08

August 1991 4.73 -- 7.38 10.58 -- 11.42 9.24

September 1991 3.93 -- -- 9.46 -- 7.70 7.82

October 1991 2.59 -- -- -- -- -- --

Annual 1991 26.96
52 Hydrologic Characterization for Spring Creek and Hydrologic Budget and Model Scenarios for Sheridan Lake, S. Dak.

Table 24. Pan evaporation data for Pactola Dam and other selected stations, 1962–2006.—Continued

[Gray shading indicates estimates derived from the MOVE.1 analysis. Red shading indicates estimates derived from regression analysis with precipitation data. 

Blue shading indicates the “annual” total pan evaporation at Pactola Dam using measured and estimated data for May–October of each year. Unshaded values 

indicate measured data. --, no data]

Month and year

Evaporation data, in inches, for selected National Weather Service stations (station number)

Pactola Dam 

(396427)

Angostura 

Dam (390217) Oral (396304) Cottonwood (391972)

Shadehill Dam 

(397567)

Oahe Dam 

(396170)

Pickstown 

(396574)

May 1992 6.67 -- -- 9.86 -- 10.82 7.33

June 1992 3.87 -- 5.96 7.54 -- 7.90 5.95

July 1992 3.99 -- 6.19 6.60 -- 6.38 5.74

August 1992 4.57 -- 5.97 7.63 -- 6.22 --

September 1992 4.48 -- 5.71 9.02 -- 7.29 5.97

October 1992 3.00 -- -- -- -- 5.32 4.34

Annual 1992 26.58

May 1993 4.33 -- -- 7.07 -- 7.93 --

June 1993 4.22 -- 6.86 7.22 -- 7.85 6.07

July 1993 4.62 -- 7.69 7.81 -- 7.16 6.19

August 1993 5.01 -- 7.45 8.32 -- 9.59 6.90

September 1993 3.21 -- -- 5.81 -- 6.37 4.89

October 1993 2.48 -- -- -- -- 4.42 --

Annual 1993 23.87

May 1994 5.66 -- -- 9.08 -- 9.38 8.13

June 1994 6.20 -- 8.27 8.49 -- 9.98 6.16

July 1994 6.04 -- 8.40 9.83 -- 9.87 6.84

August 1994 6.47 -- 8.07 9.98 -- 8.15 6.93

September 1994 4.23 -- -- 9.09 -- 6.71 6.10

October 1994 2.51 -- -- -- -- 4.47 --

Annual 1994 31.11

May 1995 3.87 -- -- -- -- -- --

June 1995 4.26 -- 6.32 6.95 -- 8.79 8.02

July 1995 5.32 -- 9.17 10.61 -- 10.22 9.96

August 1995 5.59 -- 7.62 10.38 -- 9.29 7.85

September 1995 3.18 -- 4.70 8.21 -- 6.70 5.56

October 1995 2.21 -- -- -- -- -- 3.13

Annual 1995 24.43

May 1996 3.98 -- -- -- -- -- --

June 1996 5.52 -- 7.34 9.41 -- 9.15 7.07

July 1996 6.74 -- 9.30 10.74 -- 10.78 8.12

August 1996 6.09 -- 8.19 11.60 -- 11.21 7.47

September 1996 3.24 -- -- 7.79 -- 7.93 5.52

October 1996 3.30 -- -- -- -- -- 4.61

Annual 1996 28.87
Appendix 53

Table 24. Pan evaporation data for Pactola Dam and other selected stations, 1962–2006.—Continued

[Gray shading indicates estimates derived from the MOVE.1 analysis. Red shading indicates estimates derived from regression analysis with precipitation data. 

Blue shading indicates the “annual” total pan evaporation at Pactola Dam using measured and estimated data for May–October of each year. Unshaded values 

indicate measured data. --, no data]

Month and year

Evaporation data, in inches, for selected National Weather Service stations (station number)

Pactola Dam 

(396427)

Angostura 

Dam (390217) Oral (396304) Cottonwood (391972)

Shadehill Dam 

(397567)

Oahe Dam 

(396170)

Pickstown 

(396574)

May 1997 3.90 -- -- 6.52 -- -- 6.26

June 1997 5.13 -- -- 8.33 -- 8.27 7.85

July 1997 5.78 -- 8.98 9.62 -- 8.27 7.92

August 1997 4.58 -- 5.94 7.00 -- 6.83 6.15

September 1997 3.75 -- 5.58 7.13 -- 6.92 5.11

October 1997 2.71 -- -- -- -- 4.81 --

Annual 1997 25.85

May 1998 4.23 -- -- 6.94 -- 7.45 6.70

June 1998 4.24 -- 6.19 6.50 -- 8.07 6.16

July 1998 5.15 -- 7.69 8.80 -- 9.52 7.46

August 1998 4.90 -- 6.85 8.87 -- 8.80 7.88

September 1998 4.24 -- 5.08 7.13 -- 7.79 6.37

October 1998 2.05 -- -- -- -- 3.67 2.75

Annual 1998 24.81

May 1999 3.70 -- -- 6.26 -- 6.30 5.58

June 1999 4.91 -- 6.64 7.64 -- 8.98 5.97

July 1999 6.51 -- 8.32 9.60 -- 10.78 7.75

August 1999 5.15 -- 6.72 8.88 -- 10.03 7.15

September 1999 3.32 -- 4.90 5.92 -- 5.87 4.94

October 1999 2.48 -- -- -- -- 4.41 --

Annual 1999 26.07

May 2000 4.29 -- -- 7.02 -- 8.38 6.16

June 2000 6.04 -- 7.42 9.25 -- 9.64 7.77

July 2000 5.86 -- 8.66 9.40 -- 10.89 8.24

August 2000 5.91 -- 8.36 11.72 -- -- 7.68

September 2000 4.22 -- -- 8.50 -- 10.26 6.92

October 2000 2.29 -- -- -- -- -- 3.23

Annual 2000 28.61

May 2001 4.55 -- -- 7.34 -- -- 5.51

June 2001 5.35 -- 6.72 8.50 -- 7.21 7.22

July 2001 6.28 -- 8.93 9.29 -- 10.46 7.24

August 2001 6.19 -- 8.56 9.99 -- 10.93 7.68

September 2001 3.35 -- -- 7.57 -- 7.73 5.48

October 2001 2.88 -- -- -- -- -- 4.05

Annual 2001 28.60
54 Hydrologic Characterization for Spring Creek and Hydrologic Budget and Model Scenarios for Sheridan Lake, S. Dak.

Table 24. Pan evaporation data for Pactola Dam and other selected stations, 1962–2006.—Continued

[Gray shading indicates estimates derived from the MOVE.1 analysis. Red shading indicates estimates derived from regression analysis with precipitation data. 

Blue shading indicates the “annual” total pan evaporation at Pactola Dam using measured and estimated data for May–October of each year. Unshaded values 

indicate measured data. --, no data]

Month and year

Evaporation data, in inches, for selected National Weather Service stations (station number)

Pactola Dam 

(396427)

Angostura 

Dam (390217) Oral (396304) Cottonwood (391972)

Shadehill Dam 

(397567)

Oahe Dam 

(396170)

Pickstown 

(396574)

May 2002 4.78 -- -- 7.63 -- 8.28 7.00

June 2002 5.96 -- 8.33 10.99 -- 11.68 9.47

July 2002 8.14 -- 9.96 12.17 -- 15.48 10.63

August 2002 5.70 -- 8.57 10.16 -- 10.39 7.94

September 2002 3.75 -- -- 7.16 -- 8.74 6.41

October 2002 2.59 -- -- -- -- -- --

Annual 2002 30.92

May 2003 3.61 -- -- 6.14 -- 5.95 5.66

June 2003 4.42 -- -- 7.19 -- 8.32 5.63

July 2003 8.45 -- -- 12.90 -- 13.84 9.20

August 2003 6.84 -- 10.01 13.01 -- 14.03 8.77

September 2003 3.76 -- -- 7.38 -- 9.35 6.49

October 2003 2.64 -- -- -- -- -- --

Annual 2003 29.72

May 2004 4.42 -- 6.96 8.47 -- 8.07 6.49

June 2004 4.76 -- 7.96 8.81 -- 9.39 6.49

July 2004 4.63 -- 8.66 10.01 -- 10.56 7.72

August 2004 5.18 -- 8.39 9.61 -- 9.80 7.37

September 2004 3.64 -- 5.66 8.05 -- -- 6.47

October 2004 2.30 -- -- -- -- -- 3.25

Annual 2004 24.93

May 2005 4.06 -- 5.91 6.52 -- 6.98 6.85

June 2005 4.85 -- 7.05 8.03 -- 7.86 7.13

July 2005 6.87 -- 10.36 12.05 -- 9.51 9.78

August 2005 4.68 -- 8.04 10.26 -- 12.17 7.49

September 2005 4.44 -- -- 8.59 -- -- 7.57

October 2005 2.65 -- -- -- -- -- 3.73

Annual 2005 27.55

May 2006 4.21 -- 6.78 -- -- 9.98 7.08

June 2006 6.37 -- 8.79 10.46 -- 12.19 7.77

July 2006 7.38 -- 10.07 14.36 -- 9.73

August 2006 5.60 -- 8.11 10.31 -- 7.16 7.93

September 2006 3.80 -- 5.74 5.08 -- 4.51

October 2006 2.64 -- -- -- -- -- --

Annual 2006 30.00
Appendix 55

Table 25. Total monthly stream inflow to Sheridan Lake, 1962–2006.—Continued[Total inflows include ungaged tributary inflows and were computed by multiplying inflows at gaging station 06406920 (Spring Creek above Sheridan Lake, table 22) by 1.146. Monthly volumes (in acre-feet) then were computed by multiplying by 1.98 times the number of days in each month]

Year Monthly stream inflow, in acre-feet

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

1962–63 3,769.19 8,172.30 6,751.34 2,149.61 600.99 908.79 451.64 281.00 153.72 224.93 1,016.39 2,167.741963–64 2,529.60 10,719.07 3,485.73 1,023.15 920.53 630.25 440.33 298.21 233.04 317.67 386.76 748.561964–65 1,511.37 3,689.26 4,090.77 1,060.66 346.31 365.85 226.12 178.93 158.02 111.63 177.70 612.891965–66 6,351.67 11,413.49 6,502.31 2,006.96 767.01 852.22 506.38 411.97 226.27 152.17 643.16 1,345.391966–67 831.93 251.70 333.26 866.98 468.89 399.67 386.78 220.74 212.75 186.05 771.05 865.191967–68 1,183.02 16,399.93 2,829.66 1,040.99 734.88 624.10 380.23 247.80 247.80 256.03 541.09 592.661968–69 439.64 2,104.66 455.01 925.39 289.79 257.02 229.09 181.39 129.74 82.75 343.10 904.461969–70 456.85 1,006.21 911.25 1,072.96 192.20 329.57 280.86 127.28 140.81 162.72 347.40 1,312.071970–71 2,041.39 5,166.74 1,336.13 941.38 517.09 457.47 496.26 87.31 103.30 129.96 608.73 2,677.691971–72 6,638.20 7,524.89 1,336.13 630.25 589.09 605.04 340.36 225.66 84.85 73.86 641.93 646.211972–73 1,603.60 24,755.50 3,403.95 1,486.77 762.84 701.57 427.83 221.97 198.60 131.07 522.64 1,578.641973–74 2,679.01 1,712.53 882.35 1,149.20 445.69 455.62 376.66 141.42 108.22 131.07 491.90 559.931974–75 455.01 227.31 206.60 186.92 152.93 210.29 226.12 19.06 129.74 101.63 350.48 1,348.361975–76 1,302.92 2,684.23 1,407.45 731.70 260.03 340.64 312.40 199.22 164.79 197.71 549.08 755.701976–77 4,898.10 9,079.74 2,114.56 788.27 496.86 442.10 255.27 207.21 91.00 154.39 604.42 2,729.451977–78 562.61 210.05 568.15 857.14 391.54 514.65 286.81 197.99 86.70 105.52 751.38 829.491978–79 8,087.46 3,224.53 1,135.06 894.64 505.79 480.83 437.36 139.58 67.64 88.86 667.14 720.601979–80 420.58 609.92 573.68 387.37 213.62 247.18 412.96 268.70 55.95 105.52 455.01 701.551980–81 715.72 501.02 184.46 472.22 150.55 210.90 226.12 303.75 118.67 73.31 207.21 252.301981–82 4,468.30 793.79 313.59 951.83 147.57 205.98 188.03 105.14 63.95 149.40 382.45 447.471982–83 2,263.97 4,040.33 800.57 794.42 458.78 1,336.74 397.49 245.34 155.56 157.17 870.05 1,857.121983–84 1,953.46 1,053.82 1,081.57 549.70 347.50 466.08 226.12 156.18 217.05 186.05 560.15 980.031984–85 2,510.54 6,478.21 2,065.98 829.47 633.72 506.04 429.62 95.31 94.69 180.50 771.05 642.641985–86 212.13 274.91 141.42 111.29 117.82 223.81 155.31 87.31 177.70 179.39 617.34 1,147.831986–87 1,923.95 1,876.76 835.00 491.29 605.75 926.62 476.03 295.76 209.06 169.94 1,409.91 1,345.391987–88 1,746.25 1,099.04 569.38 351.71 61.88 44.27 24.40 12.91 18.45 22.21 215.21 295.141988–89 482.68 98.78 9.84 3.07 58.91 133.43 1.19 9.22 11.07 1.11 461.77 192.791989–90 306.82 99.97 24.60 38.74 42.84 52.26 66.64 72.56 48.58 34.43 143.27 637.881990–91 1,523.05 1,923.17 850.37 616.11 120.20 183.85 226.12 160.48 170.32 137.73 391.68 709.291991–92 5,193.24 8,265.12 1,895.66 916.17 417.12 376.92 449.85 348.02 176.47 204.93 494.36 490.91
56 Hydrologic Characterization for Spring Creek and Hydrologic Budget and Model Scenarios for Sheridan Lake, S. Dak. Table 25. Total monthly stream inflow to Sheridan Lake, 1962–2006.—Continued [Total inflows include ungaged tributary inflows and were computed by multiplying inflows at gaging station 06406920 (Spring Creek above Sheridan Lake, table 22) by 1.146. Monthly volumes (in acre-feet) then were computed by multiplying by 1.98 times the number of days in each month] Year Monthly stream inflow, in acre-feet May June July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. 1992–93 397.21 555.17 789.50 496.82 252.30 211.52 161.85 114.37 126.66 146.62 667.76 1,200.20 1993–94 5,024.15 7,344.00 3,185.06 1,606.67 865.79 972.12 831.87 664.07 423.65 397.09 1,191.01 1,084.17 1994–95 2,423.84 1,002.64 405.20 196.15 104.73 416.89 308.83 285.30 244.72 234.92 609.34 496.86 1995–96 10,182.35 12,595.24 4,157.18 1,606.67 940.76 908.79 674.18 482.68 359.09 572.03 916.17 1,595.90 1996–97 6,370.12 8,271.67 2,219.70 1,472.63 1,186.51 1,268.49 1,704.79 1,374.25 1,127.68 923.03 1,515.05 2,850.25 1997–98 8,526.49 9,205.88 3,657.28 3,530.00 1,786.91 1,360.11 777.12 703.42 421.80 439.85 1,437.58 2,100.50 1998–99 2,303.94 6,519.27 4,460.31 2,818.59 1,773.22 2,522.84 3,491.70 2,452.13 1,543.34 1,221.82 1,535.96 4,377.72 1999–2000 6,743.35 10,310.88 3,868.80 2,508.69 1,500.10 1,155.35 872.93 670.21 553.39 636.46 824.55 1,520.93 2000–2001 2,290.41 1,111.54 648.69 292.68 217.79 340.64 391.54 274.85 237.34 226.59 557.08 1,172.83 2001–02 1,099.40 1,404.89 1,902.43 866.98 508.17 549.70 437.95 257.02 129.74 144.40 328.34 934.21 2002–03 1,211.92 702.15 277.92 273.00 402.84 301.29 247.54 160.48 81.78 161.61 587.82 1,111.54 2003–04 2,423.84 1,336.46 405.20 352.94 238.61 182.62 213.62 133.43 71.33 77.20 387.37 367.14 2004–05 290.22 150.55 205.98 154.33 89.85 122.36 6.55 17.22 42.43 52.76 110.06 276.69 2005–06 544.78 513.52 215.82 271.78 4.76 148.19 6.55 44.89 41.81 35.54 279.77 609.92 Statistical summary Number of values 44 44 44 44 44 44 44 44 44 44 44 44 Mean 2,702.14 4,465.47 1,670.34 926.69 492.98 544.33 442.44 299.59 214.98 215.45 621.40 1,131.69 Maximum 10,182.35 24,755.50 6,751.34 3,530.00 1,786.91 2,522.84 3,491.70 2,452.13 1,543.34 1,221.82 1,535.96 4,377.72 75th percentile 3,943.97 7,686.74 2,372.19 1,063.74 612.74 648.08 442.71 287.92 219.36 209.93 756.30 1,346.13 50th percentile 1,938.71 1,899.97 896.80 843.31 409.98 429.50 358.51 203.22 147.27 153.28 558.62 884.83 25th percentile 677.44 679.09 405.20 378.76 182.38 220.74 226.12 124.05 86.24 104.55 385.68 612.15 Minimum 212.13 98.78 9.84 3.07 4.76 44.27 1.19 9.22 11.07 1.11 110.06 192.79
Appendix 57

Table 26. Effective monthly precipitation on Sheridan Lake, 1962–2006.—Continued[Effective precipitation reflects potential sublimation of snowpack on ice cover]

Year Effective monthly precipitation, in acre-feet

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

1962–63 323.68 229.51 206.53 38.94 37.03 48.84 5.81 0.64 7.02 6.70 27.96 127.681963–64 64.48 233.34 98.64 37.35 98.64 30.33 2.46 4.79 6.54 6.70 12.26 36.261964–65 114.60 197.59 82.99 47.56 39.26 1.28 8.27 26.81 10.21 3.03 10.53 38.311965–66 309.00 185.78 136.94 81.40 59.05 4.47 3.58 5.43 2.39 10.69 17.43 77.891966–67 4.15 30.96 143.01 121.94 78.21 30.33 10.73 11.17 3.03 7.98 9.19 71.761967–68 110.13 240.37 54.59 47.24 40.86 11.49 7.37 7.34 9.42 3.51 5.36 26.811968–69 75.97 182.27 50.75 91.29 40.86 3.83 7.60 8.62 3.67 18.67 9.58 45.971969–70 77.57 125.13 198.23 31.60 23.30 43.73 7.15 2.07 3.83 5.59 28.92 84.531970–71 139.50 117.15 67.03 80.76 42.77 38.31 14.30 9.26 13.09 11.33 27.96 152.711971–72 182.27 108.53 54.27 37.35 80.44 55.22 21.90 3.67 3.99 4.79 13.22 49.801972–73 93.21 342.19 102.79 99.91 16.28 23.94 7.15 4.95 1.44 4.31 65.50 93.721973–74 52.03 78.21 117.79 37.99 57.46 23.62 27.26 9.26 6.54 2.87 4.60 26.301974–75 53.63 33.52 127.05 45.33 29.69 68.63 6.48 1.92 11.49 8.78 19.34 72.011975–76 76.61 154.82 42.46 28.09 2.23 15.00 11.84 12.77 3.99 15.80 6.51 111.601976–77 119.38 195.36 115.24 64.48 35.75 6.07 10.50 3.51 6.54 4.63 38.31 42.901977–78 49.16 99.27 128.00 85.23 61.93 26.81 15.19 12.13 5.59 11.81 5.17 68.441978–79 215.47 52.99 129.28 57.78 18.20 16.60 16.98 10.53 6.07 6.86 7.66 29.881979–80 48.52 153.22 273.88 89.06 6.07 23.94 6.70 2.39 4.31 5.91 17.62 40.601980–81 74.38 87.46 69.91 89.38 24.26 61.93 9.16 6.86 .80 2.07 4.41 16.601981–82 215.15 47.88 165.67 41.50 12.45 74.38 1.34 11.65 8.46 6.54 22.60 22.221982–83 185.78 130.24 101.19 73.74 82.04 68.31 8.27 8.30 5.11 2.07 32.18 24.261983–84 89.38 108.21 41.18 91.93 16.60 69.27 26.59 8.94 2.07 3.19 10.92 92.441984–85 62.88 165.03 154.18 42.77 35.75 23.62 17.88 5.43 3.35 1.12 19.54 28.091985–86 33.20 39.26 66.40 38.31 67.03 20.11 40.00 11.01 1.76 19.15 13.41 93.721986–87 57.14 152.58 53.31 62.88 196.31 57.46 22.79 .16 1.12 26.18 32.75 4.851987–88 172.37 20.43 53.31 87.78 22.66 23.30 5.36 5.59 4.63 4.95 14.94 20.431988–89 74.70 122.90 61.29 85.55 8.30 18.20 26.37 3.83 .80 8.78 17.81 44.691989–90 63.84 63.84 59.05 89.70 149.39 30.33 7.60 9.26 .48 9.10 28.92 52.611990–91 153.22 52.67 147.16 52.03 36.39 22.03 12.07 9.42 2.07 10.06 12.07 99.851991–92 237.49 170.14 92.25 40.22 33.20 38.31 22.34 .00 1.12 3.67 41.56 34.731992–93 86.51 119.38 131.83 39.90 20.11 21.39 7.15 11.17 10.53 13.09 12.45 74.57
58 Hydrologic Characterization for Spring Creek and Hydrologic Budget and Model Scenarios for Sheridan Lake, S. Dak. Table 26. Effective monthly precipitation on Sheridan Lake, 1962–2006.—Continued [Effective precipitation reflects potential sublimation of snowpack on ice cover] Year Effective monthly precipitation, in acre-feet May June July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. 1993–94 184.50 165.67 108.85 62.25 35.43 58.10 8.94 7.66 5.43 10.06 12.26 44.94 1994–95 72.78 33.52 42.77 60.33 22.98 153.54 8.27 7.34 .64 11.97 17.24 61.03 1995–96 256.33 167.27 136.62 40.86 46.29 87.78 10.28 2.39 14.84 1.76 30.45 58.99 1996–97 232.07 61.93 72.46 156.73 71.82 154.50 8.94 16.92 4.47 12.29 6.70 77.89 1997–98 167.59 100.87 164.71 81.08 65.76 34.79 2.23 5.27 9.10 13.89 44.24 28.35 1998–99 95.44 196.31 106.62 107.57 105.34 147.79 34.63 1.76 14.36 1.76 18.96 87.59 1999–2000 82.68 247.07 95.44 92.57 42.14 7.98 5.14 2.87 7.50 4.63 20.49 117.21 2000–2001 100.23 68.63 96.72 21.71 21.39 52.35 30.84 4.63 4.47 15.80 14.56 63.33 2001–02 85.55 132.79 146.20 89.06 55.54 48.20 14.08 1.28 2.39 3.83 30.84 57.20 2002–03 95.76 51.07 99.59 73.42 108.21 37.67 7.60 1.92 11.65 8.94 37.35 84.02 2003–04 61.93 78.85 11.81 102.47 39.26 15.32 28.15 5.59 5.75 16.92 9.19 40.09 2004–05 77.57 49.16 91.29 42.46 78.53 15.32 4.25 .96 9.42 3.51 15.32 45.97 2005–06 143.33 69.59 93.53 76.93 35.75 39.26 5.36 3.35 2.71 6.86 45.39 49.29 Statistical summary Number of values 44 44 44 44 44 44 44 44 44 44 44 44 Mean 119.80 124.16 104.38 67.42 50.02 42.13 12.88 6.61 5.55 8.23 20.31 59.59 Maximum 323.68 342.19 273.88 156.73 196.31 154.50 40.00 26.81 14.84 26.18 65.50 152.71 75th percentile 168.79 167.99 133.03 89.06 66.08 55.78 17.21 9.26 7.74 11.45 28.92 79.42 50th percentile 91.30 118.27 99.12 63.68 39.26 30.33 8.94 5.51 4.55 6.78 17.34 51.21 25th percentile 70.71 63.36 65.12 41.34 23.22 19.63 7.04 2.75 2.39 3.79 10.82 35.88 Minimum 4.15 20.43 11.81 21.71 2.23 1.28 1.34 .00 .48 1.12 4.41 4.85
Appendix 59

Table 27. Monthly (May through October) evaporation from Sheridan Lake, 1962–2006.—Continued

[Lake evaporation was computed by multiplying pan evaporation data for National Weather Service station 396427 (table 24) by monthly pan coefficients]

Year

Estimated monthly evaporation, in acre-feet, using monthly pan coefficients

0.50 0.60 0.70 0.80 0.90 1.00

May June July August September October

1962–63 57.78 81.08 117.47 127.05 94.49 77.89

1963–64 69.91 96.08 131.51 154.50 90.02 86.83

1964–65 78.53 86.51 141.09 159.29 123.22 95.76

1965–66 63.52 94.81 119.70 123.53 76.29 98.96

1966–67 88.10 119.07 177.80 139.18 106.62 69.91

1967–68 59.37 71.50 140.77 148.11 109.49 100.23

1968–69 62.88 111.09 147.79 146.20 111.40 119.07

1969–70 88.74 81.72 156.41 184.82 147.48 61.29

1970–71 75.33 133.43 168.54 173.33 116.51 72.46

1971–72 66.08 103.74 141.09 165.67 108.21 69.91

1972–73 62.88 103.74 119.70 125.77 109.17 65.12

1973–74 71.50 133.11 164.71 141.41 89.70 75.97

1974–75 57.46 120.02 171.74 145.24 110.45 87.78

1975–76 70.23 99.91 162.16 153.86 112.04 70.23

1976–77 84.27 112.36 138.22 139.50 121.30 91.29

1977–78 96.40 125.77 152.58 116.51 134.71 58.10

1978–79 66.08 116.19 169.18 137.58 153.54 98.00

1979–80 69.59 104.06 143.01 113.00 128.00 84.59

1980–81 77.89 115.24 167.90 152.58 120.02 118.75

1981–82 59.37 100.87 137.58 119.70 124.17 79.48

1982–83 75.33 84.91 128.96 119.07 83.31 73.42

1983–84 61.29 87.78 161.84 148.11 125.77 47.56

1984–85 66.72 98.96 132.15 153.22 120.98 66.08

1985–86 87.46 109.49 163.44 141.09 115.87 83.95

1986–87 79.80 116.19 128.96 145.56 70.55 47.56

1987–88 59.05 114.60 144.28 132.15 112.04 86.51

1988–89 85.23 155.77 171.74 171.10 130.56 94.17

1989–90 80.44 91.61 153.86 147.16 120.98 91.29

1990–91 51.07 110.77 143.64 126.73 112.36 111.72

1991–92 72.46 96.08 137.58 120.66 113.00 82.68

1992–93 106.62 74.06 89.06 116.83 128.64 95.76

1993–94 69.27 80.76 103.11 128.00 92.25 79.16

1994–95 90.34 118.75 135.03 165.35 121.62 80.12

1995–96 61.93 81.72 118.75 142.69 91.29 70.55

1996–97 63.52 105.66 150.67 155.46 93.21 105.34

1997–98 62.25 98.32 129.28 116.83 107.89 86.51

1998–99 67.67 81.08 115.24 125.13 121.94 65.44

1999–2000 59.05 94.17 145.56 131.51 95.44 79.16

2000–2001 68.63 115.55 130.88 150.99 121.30 73.10

2001–02 72.78 102.47 140.45 158.01 96.40 91.93

2002–03 76.29 114.28 181.95 145.56 107.89 82.68
60 Hydrologic Characterization for Spring Creek and Hydrologic Budget and Model Scenarios for Sheridan Lake, S. Dak.

Table 27. Monthly (May through October) evaporation from Sheridan Lake, 1962–2006.—Continued

[Lake evaporation was computed by multiplying pan evaporation data for National Weather Service station 396427 (table 24) by monthly pan coefficients]

Year

Estimated monthly evaporation, in acre-feet, using monthly pan coefficients

0.50 0.60 0.70 0.80 0.90 1.00

May June July August September October

2003–04 57.78 84.59 188.97 174.61 107.89 84.27

2004–05 70.55 91.29 103.42 132.15 104.70 73.42

2005–06 64.80 92.89 153.54 119.38 127.68 84.59

Statistical summary

Number of values 44 44 44 44 44 44 

Mean 71.28 102.55 143.67 141.69 111.60 82.24

Maximum 106.62 155.77 188.97 184.82 153.54 119.07

75th percentile 78.05 114.76 161.92 153.38 121.70 91.45

50th percentile 69.43 101.67 142.05 142.05 112.04 82.68

25th percentile 62.72 90.41 130.48 126.49 102.63 71.98

Minimum 51.07 71.50 89.06 113.00 70.55 47.56
Appendix 61

Table 28. Computed monthly net inflow to Sheridan Lake, 1962–2006. Net inflow is computed as total inflow minus evaporation, and is independent of releases.—Continued[Net inflow was computed as total inflow minus evaporation. Negative values represent a drawdown condition for the historical pass-through operating system]

Year Monthly net inflow, in cubic feet per second

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

1962–63 65.62 139.83 111.25 33.53 9.13 14.31 7.69 4.58 2.61 4.17 16.98 38.581963–64 41.05 182.45 56.16 14.73 15.61 9.33 7.44 4.93 3.90 5.84 6.49 13.191964–65 25.17 63.87 65.59 15.43 4.41 4.41 3.94 3.35 2.74 2.06 3.06 10.941965–66 107.29 193.34 106.03 31.95 12.60 12.32 8.57 6.79 3.72 2.93 10.74 23.921966–67 12.16 2.75 4.85 13.82 7.40 5.86 6.68 3.77 3.51 3.49 12.69 15.751967–68 20.07 278.45 44.62 15.29 11.20 8.71 6.51 4.15 4.18 4.67 8.89 10.411968–69 7.36 36.57 5.82 14.16 3.68 2.31 3.98 3.09 2.17 1.83 5.74 15.971969–70 7.25 17.64 15.50 14.96 1.14 5.07 4.84 2.10 2.35 3.03 6.12 23.471970–71 34.24 86.56 20.08 13.80 7.45 6.88 8.58 1.57 1.89 2.54 10.35 47.571971–72 109.85 126.54 20.32 8.16 9.43 9.60 6.09 3.73 1.44 1.42 10.65 11.701972–73 26.57 420.04 55.08 23.76 11.26 10.74 7.31 3.69 3.25 2.44 9.57 28.101973–74 43.25 27.86 13.59 17.01 6.95 6.56 6.79 2.45 1.87 2.41 8.07 9.851974–75 7.34 2.37 2.63 1.42 1.21 3.11 3.91 .34 2.30 1.99 6.01 23.871975–76 21.29 46.03 20.94 9.85 2.52 4.64 5.45 3.45 2.74 3.84 9.04 14.581976–77 80.23 153.98 34.02 11.60 6.91 5.80 4.47 3.43 1.59 2.86 10.45 46.591977–78 8.38 3.08 8.84 13.43 5.36 7.86 5.08 3.42 1.50 2.11 12.30 15.091978–79 133.96 53.13 17.81 13.25 6.23 6.50 7.64 2.44 1.20 1.72 10.97 12.611979–80 6.50 11.08 11.46 5.91 1.54 3.03 7.05 4.41 .98 2.01 7.69 12.471980–81 11.58 7.95 1.41 6.65 .92 2.51 3.95 5.05 1.94 1.36 3.44 4.521981–82 75.20 12.45 5.56 14.21 .60 3.27 3.18 1.90 1.18 2.81 6.59 7.891982–83 38.62 68.66 12.57 12.18 7.69 21.66 6.82 4.13 2.61 2.87 14.67 31.621983–84 32.23 18.05 15.63 8.03 4.01 7.93 4.25 2.69 3.56 3.41 9.29 18.021984–85 40.77 109.98 33.96 11.69 9.22 7.54 7.52 1.64 1.59 3.27 12.86 11.271985–86 2.57 3.44 .72 .14 1.16 2.60 3.28 1.60 2.92 3.57 10.26 20.861986–87 30.92 32.15 12.35 6.65 12.29 15.23 8.38 4.81 3.42 3.53 23.46 22.691987–88 30.24 16.89 7.78 5.00 -.46 -.31 .50 .30 .38 .49 3.74 5.301988–89 7.68 1.11 -1.64 -1.34 -1.06 .93 .46 .21 .19 .18 7.80 3.991989–90 4.72 1.21 -1.14 -.30 1.20 -.14 1.25 1.33 .80 .78 2.80 11.601990–91 26.43 31.34 13.89 8.81 .74 1.53 4.00 2.76 2.80 2.66 6.57 13.601991–92 87.14 140.14 30.09 13.59 5.67 5.41 7.94 5.66 2.89 3.76 8.72 8.831992–93 6.13 10.09 13.54 6.83 2.42 2.23 2.84 2.04 2.23 2.88 11.06 21.42
62 Hydrologic Characterization for Spring Creek and Hydrologic Budget and Model Scenarios for Sheridan Lake, S. Dak. Table 28. Computed monthly net inflow to Sheridan Lake, 1962–2006. Net inflow is computed as total inflow minus evaporation, and is independent of releases.—Continued [Net inflow was computed as total inflow minus evaporation. Negative values represent a drawdown condition for the historical pass-through operating system] Year Monthly net inflow, in cubic feet per second May June July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. 1993–94 83.58 124.85 51.89 25.06 13.60 15.47 14.13 10.92 6.98 7.33 19.57 18.98 1994–95 39.13 15.42 5.09 1.48 .10 7.97 5.33 4.76 3.99 4.45 10.19 9.38 1995–96 168.76 213.11 67.90 24.47 15.05 15.06 11.50 7.89 6.08 10.33 15.40 27.81 1996–97 106.34 138.28 34.83 23.97 19.58 21.43 28.80 22.63 18.41 16.84 24.75 49.21 1997–98 140.38 154.75 60.06 56.83 29.32 21.28 13.10 11.53 7.01 8.17 24.10 35.78 1998–99 37.92 111.50 72.40 45.55 29.52 42.37 59.26 39.91 25.33 22.03 25.29 75.04 1999–2000 110.05 175.85 62.10 40.17 24.31 17.63 14.76 10.95 9.12 11.54 13.74 27.53 2000–2001 37.76 17.89 9.99 2.66 1.98 5.20 7.10 4.55 3.93 4.36 9.30 20.77 2001–02 18.09 24.12 31.03 12.98 7.85 8.23 7.60 4.20 2.15 2.67 5.84 16.66 2002–03 20.03 10.74 3.18 3.27 6.78 4.17 4.29 2.64 1.52 3.07 10.17 20.09 2003–04 39.49 22.36 3.71 4.57 2.86 1.85 4.06 2.26 1.25 1.69 6.45 6.84 2004–05 4.83 1.82 3.15 1.05 1.07 1.05 .18 .30 .84 1.01 2.04 5.42 2005–06 10.14 8.24 2.53 3.73 -1.46 1.67 .20 .78 .72 .76 5.29 11.08 Statistical summary Number of values 44 44 44 44 44 44 44 44 44 44 44 44 Mean 44.73 75.41 26.53 13.86 7.25 8.20 7.65 4.98 3.59 4.03 10.44 20.02 Maximum 168.76 420.04 111.25 56.83 29.52 42.37 59.26 39.91 25.33 22.03 25.29 75.04 75th percentile 68.02 129.48 37.28 15.33 9.87 9.89 7.65 4.77 3.60 3.92 12.40 23.88 50th percentile 31.58 31.75 14.70 12.58 5.95 6.18 6.30 3.44 2.48 2.88 9.44 15.86 25th percentile 11.22 11.00 5.44 5.68 1.21 2.92 3.97 2.09 1.52 2.01 6.48 11.05 Minimum 2.57 1.11 -1.64 -1.34 -1.46 -.31 .18 .21 .19 .18 2.04 3.99
Appendix 63

Table 29. Computed values of accumulated end-of-month storage change for zero-release scenario (pass-through operating system) for Sheridan Lake, 1962–2006.—Continued[Negative values indicate storage deficits, which are accumulated. Values of zero indicate a monthend condition at or above the spillway. Positive values are shown only for months when storage deficits end. NA, not applicable]

Year Monthly end-of-month storage, in acre-feet

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

1962–63 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.001963–64 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001964–65 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001965–66 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001966–67 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001967–68 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001968–69 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001969–70 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001970–71 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001971–72 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001972–73 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001973–74 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001974–75 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001975–76 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001976–77 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001977–78 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001978–79 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001979–80 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001980–81 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001981–82 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001982–83 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001983–84 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001984–85 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001985–86 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001986–87 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001987–88 .00 .00 .00 .00 -27.50 -46.44 -16.68 1.82 .00 .00 .00 .001988–89 .00 .00 -100.61 -183.09 -246.44 -188.98 -161.42 -148.37 -136.50 -126.61 352.97 .001989–90 .00 .00 -70.21 -88.93 -17.68 -26.38 47.86 .00 .00 .00 .00 .001990–91 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00
64 Hydrologic Characterization for Spring Creek and Hydrologic Budget and Model Scenarios for Sheridan Lake, S. Dak. Table 29. Computed values of accumulated end-of-month storage change for zero-release scenario (pass-through operating system) for Sheridan Lake, 1962–2006.—Continued [Negative values indicate storage deficits, which are accumulated. Values of zero indicate a monthend condition at or above the spillway. Positive values are shown only for months when storage deficits end. NA, not applicable] Year Monthly end-of-month storage, in acre-feet May June July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. 1991–92 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 1992–93 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 1993–94 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 1994–95 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 1995–96 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 1996–97 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 1997–98 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 1998–99 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 1999–2000 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 2000–2001 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 2001–02 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 2002–03 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 2003–04 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 2004–05 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 2005–06 .00 .00 .00 .00 -87.17 15.69 .00 .00 .00 .00 .00 .00 Statistical summary Number of values 44 44 44 44 44 44 44 44 44 44 44 44 Mean NA NA NA NA NA NA NA NA NA NA NA NA Maximum NA NA NA NA NA NA NA NA NA NA NA NA 75th percentile .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 50th percentile .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 25th percentile .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 Minimum .00 .00 -100.61 -183.09 -246.44 -188.98 -161.42 -148.37 -136.50 -126.61 .00 .00
Appendix 65

Table 30. Computed monthly values of reservoir outflow from Sheridan Lake for pass-through operating system, 1962–2006.—Continued[Positive values represent computed outflow through the spillway. Values of zero indicate a monthend condition of storage deficit]

Year Computed monthly values of reservoir outflow, in cubic feet per second

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

1962–63 65.62 139.83 111.25 33.53 9.13 14.31 7.69 4.58 2.61 4.17 16.98 38.581963–64 41.05 182.45 56.16 14.73 15.61 9.33 7.44 4.93 3.90 5.84 6.49 13.191964–65 25.17 63.87 65.59 15.43 4.41 4.41 3.94 3.35 2.74 2.06 3.06 10.941965–66 107.29 193.34 106.03 31.95 12.60 12.32 8.57 6.79 3.72 2.93 10.74 23.921966–67 12.16 2.75 4.85 13.82 7.40 5.86 6.68 3.77 3.51 3.49 12.69 15.751967–68 20.07 278.45 44.62 15.29 11.20 8.71 6.51 4.15 4.18 4.67 8.89 10.411968–69 7.36 36.57 5.82 14.16 3.68 2.31 3.98 3.09 2.17 1.83 5.74 15.971969–70 7.25 17.64 15.50 14.96 1.14 5.07 4.84 2.10 2.35 3.03 6.12 23.471970–71 34.24 86.56 20.08 13.80 7.45 6.88 8.58 1.57 1.89 2.54 10.35 47.571971–72 109.85 126.54 20.32 8.16 9.43 9.60 6.09 3.73 1.44 1.42 10.65 11.701972–73 26.57 420.04 55.08 23.76 11.26 10.74 7.31 3.69 3.25 2.44 9.57 28.101973–74 43.25 27.86 13.59 17.01 6.95 6.56 6.79 2.45 1.87 2.41 8.07 9.851974–75 7.34 2.37 2.63 1.42 1.21 3.11 3.91 .34 2.30 1.99 6.01 23.871975–76 21.29 46.03 20.94 9.85 2.52 4.64 5.45 3.45 2.74 3.84 9.04 14.581976–77 80.23 153.98 34.02 11.60 6.91 5.80 4.47 3.43 1.59 2.86 10.45 46.591977–78 8.38 3.08 8.84 13.43 5.36 7.86 5.08 3.42 1.50 2.11 12.30 15.091978–79 133.96 53.13 17.81 13.25 6.23 6.50 7.64 2.44 1.20 1.72 10.97 12.611979–80 6.50 11.08 11.46 5.91 1.54 3.03 7.05 4.41 .98 2.01 7.69 12.471980–81 11.58 7.95 1.41 6.65 .92 2.51 3.95 5.05 1.94 1.36 3.44 4.521981–82 75.20 12.45 5.56 14.21 .60 3.27 3.18 1.90 1.18 2.81 6.59 7.891982–83 38.62 68.66 12.57 12.18 7.69 21.66 6.82 4.13 2.61 2.87 14.67 31.621983–84 32.23 18.05 15.63 8.03 4.01 7.93 4.25 2.69 3.56 3.41 9.29 18.021984–85 40.77 109.98 33.96 11.69 9.22 7.54 7.52 1.64 1.59 3.27 12.86 11.271985–86 2.57 3.44 .72 .14 1.16 2.60 3.28 1.60 2.92 3.57 10.26 20.861986–87 30.92 32.15 12.35 6.65 12.29 15.23 8.38 4.81 3.42 3.53 23.46 22.691987–88 30.24 16.89 7.78 5.00 .00 .00 .00 .03 .38 .49 3.74 5.301988–89 7.68 1.11 .00 .00 .00 .00 .00 .00 .00 .00 5.74 3.991989–90 4.72 1.21 .00 .00 .00 .00 .80 1.33 .80 .78 2.80 11.601990–91 26.43 31.34 13.89 8.81 .74 1.53 4.00 2.76 2.80 2.66 6.57 13.601991–92 87.14 140.14 30.09 13.59 5.67 5.41 7.94 5.66 2.89 3.76 8.72 8.831992–93 6.13 10.09 13.54 6.83 2.42 2.23 2.84 2.04 2.23 2.88 11.06 21.42
66 Hydrologic Characterization for Spring Creek and Hydrologic Budget and Model Scenarios for Sheridan Lake, S. Dak. Table 30. Computed monthly values of reservoir outflow from Sheridan Lake for pass-through operating system, 1962–2006.—Continued [Positive values represent computed outflow through the spillway. Values of zero indicate a monthend condition of storage deficit] Year Computed monthly values of reservoir outflow, in cubic feet per second May June July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. 1993–94 83.58 124.85 51.89 25.06 13.60 15.47 14.13 10.92 6.98 7.33 19.57 18.98 1994–95 39.13 15.42 5.09 1.48 .10 7.97 5.33 4.76 3.99 4.45 10.19 9.38 1995–96 168.76 213.11 67.90 24.47 15.05 15.06 11.50 7.89 6.08 10.33 15.40 27.81 1996–97 106.34 138.28 34.83 23.97 19.58 21.43 28.80 22.63 18.41 16.84 24.75 49.21 1997–98 140.38 154.75 60.06 56.83 29.32 21.28 13.10 11.53 7.01 8.17 24.10 35.78 1998–99 37.92 111.50 72.40 45.55 29.52 42.37 59.26 39.91 25.33 22.03 25.29 75.04 1999–2000 110.05 175.85 62.10 40.17 24.31 17.63 14.76 10.95 9.12 11.54 13.74 27.53 2000–2001 37.76 17.89 9.99 2.66 1.98 5.20 7.10 4.55 3.93 4.36 9.30 20.77 2001–02 18.09 24.12 31.03 12.98 7.85 8.23 7.60 4.20 2.15 2.67 5.84 16.66 2002–03 20.03 10.74 3.18 3.27 6.78 4.17 4.29 2.64 1.52 3.07 10.17 20.09 2003–04 39.49 22.36 3.71 4.57 2.86 1.85 4.06 2.26 1.25 1.69 6.45 6.84 2004–05 4.83 1.82 3.15 1.05 1.07 1.05 .18 .30 .84 1.01 2.04 5.42 2005–06 10.14 8.24 2.53 3.73 .00 .26 .20 .78 .72 .76 5.29 11.08 Statistical summary Number of values 44 44 44 44 44 44 44 44 44 44 44 44 Mean 44.73 75.41 26.59 13.90 7.29 8.16 7.62 4.97 3.58 4.02 10.39 20.02 Maximum 168.76 420.04 111.25 56.83 29.52 42.37 59.26 39.91 25.33 22.03 25.29 75.04 75th percentile 68.02 129.48 37.28 15.33 9.87 9.89 7.65 4.77 3.60 3.92 12.40 23.88 50th percentile 31.58 31.75 14.70 12.58 5.95 6.18 6.30 3.44 2.48 2.88 9.44 15.86 25th percentile 11.22 11.00 5.44 5.68 1.20 2.92 3.97 2.09 1.52 2.01 6.37 11.05 Minimum 2.57 1.11 .00 .00 .00 .00 .00 .00 .00 .00 2.04 3.99
Appendix 67

Table 31. Computed values of accumulated end-of-month storage change for release scenario of 1.0 cubic foot per second, 1962–2006.—Continued[Prescribed release is for May through October, with continued releases of 1 cubic foot per second for subsequent months with persisting storage deficits. Negative values indicate storage deficits, which are accumulated. Values of zero indicate a monthend condition at or above the spillway. Positive values are shown only for months when storage deficits end. NA, not applicable]

Year Computed end-of-month storage, in acre-feet

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

1962–63 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.001963–64 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001964–65 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001965–66 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001966–67 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001967–68 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001968–69 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001969–70 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001970–71 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001971–72 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001972–73 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001973–74 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001974–75 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001975–76 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001976–77 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001977–78 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001978–79 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001979–80 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001980–81 .00 .00 .00 .00 -4.71 87.88 .00 .00 .00 .00 .00 .001981–82 .00 .00 .00 .00 -23.65 115.74 .00 .00 .00 .00 .00 .001982–83 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001983–84 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001984–85 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001985–86 .00 .00 -17.11 -70.09 -60.61 37.87 .00 .00 .00 .00 .00 .001986–87 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001987–88 .00 .00 .00 .00 -87.00 -167.43 -197.17 -240.16 -278.57 -306.95 -138.29 177.281988–89 .00 .00 -162.10 -306.07 -428.92 -432.95 -464.89 -513.33 -562.95 -608.60 -190.51 46.971989–90 .00 .00 -131.70 -211.91 -200.16 -270.35 -255.61 -235.28 -247.71 -259.72 -149.02 541.471990–91 .00 .00 .00 .00 -15.27 17.40 .00 .00 .00 .00 .00 .001991–92 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00
68 Hydrologic Characterization for Spring Creek and Hydrologic Budget and Model Scenarios for Sheridan Lake, S. Dak. Table 31. Computed values of accumulated end-of-month storage change for release scenario of 1.0 cubic foot per second, 1962–2006.—Continued [Prescribed release is for May through October, with continued releases of 1 cubic foot per second for subsequent months with persisting storage deficits. Negative values indicate storage deficits, which are accumulated. Values of zero indicate a monthend condition at or above the spillway. Positive values are shown only for months when storage deficits end. NA, not applicable] Year Computed end-of-month storage, in acre-feet May June July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. 1992–93 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 1993–94 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 1994–95 .00 .00 .00 .00 -53.41 375.41 .00 .00 .00 .00 .00 .00 1995–96 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 1996–97 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 1997–98 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 1998–99 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 1999–2000 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 2000–2001 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 2001–02 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 2002–03 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 2003–04 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 2004–05 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 2005–06 .00 .00 .00 .00 -146.67 -105.30 -152.89 -166.14 -183.11 -196.25 128.91 .00 Statistical summary Number of values 44 44 44 44 44 44 44 44 44 44 44 44 Mean NA NA NA NA NA NA NA NA NA NA NA NA Maximum NA NA NA NA NA NA NA NA NA NA NA NA 75th percentile .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 50th percentile .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 25th percentile .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 Minimum .00 .00 -162.10 -306.07 -428.92 -432.95 -464.89 -513.33 -562.95 -608.60 -190.51 .00
Appendix 69

Table 32. Computed values of accumulated end-of-month storage change for release scenario of 2.0 cubic feet per second, 1962–2006.—Continued[Prescribed release is for May through October, with continued releases of 1 cubic foot per second for subsequent months with persisting storage deficits. Negative values indicate storage deficits, which are accumulated. Values of zero indicate a monthend condition at or above the spillway. Positive values are shown only for months when storage deficits end. NA, not applicable]

Year Computed end-of-month storage, in acre-feet

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

1962–63 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.001963–64 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00

1964–65 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00

1965–66 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00

1966–67 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00

1967–68 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00

1968–69 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00

1969–70 .00 .00 .00 .00 -50.99 138.04 .00 .00 .00 .00 .00 .00

1970–71 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00

1971–72 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00

1972–73 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00

1973–74 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00

1974–75 .00 .00 .00 -35.97 -82.81 -14.65 158.45 .00 .00 .00 .00 .00

1975–76 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00

1976–77 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00

1977–78 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00

1978–79 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00

1979–80 .00 .00 .00 .00 -27.32 36.23 .00 .00 .00 .00 .00 .00

1980–81 .00 .00 -36.51 249.53 -64.22 -33.12 142.66 .00 .00 .00 .00 .00

1981–82 .00 .00 .00 .00 -83.16 -5.26 124.61 .00 .00 .00 .00 .00

1982–83 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00

1983–84 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00

1984–85 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00

1985–86 .00 .00 -78.60 -193.07 -243.10 -206.11 -70.30 -33.47 145.99 .00 .00 .00

1986–87 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00

1987–88 .00 .00 .00 .00 -146.51 -288.43 -318.17 -361.16 -399.57 -427.95 -259.29 56.28

1988–89 .00 -53.10 -276.69 -482.15 -664.51 -730.03 -761.97 -810.41 -860.03 -905.68 -487.59 -309.61

1989–90 -142.37 -189.18 -382.37 -524.07 -571.83 -703.51 -688.77 -668.44 -680.87 -692.88 -582.18 48.81

1990–91 .00 .00 .00 .00 -74.78 -103.60 75.09 .00 .00 .00 .00 .00

1991–92 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00
70 Hydrologic Characterization for Spring Creek and Hydrologic Budget and Model Scenarios for Sheridan Lake, S. Dak. Table 32. Computed values of accumulated end-of-month storage change for release scenario of 2.0 cubic feet per second, 1962–2006.—Continued [Prescribed release is for May through October, with continued releases of 1 cubic foot per second for subsequent months with persisting storage deficits. Negative values indicate storage deficits, which are accumulated. Values of zero indicate a monthend condition at or above the spillway. Positive values are shown only for months when storage deficits end. NA, not applicable] Year Computed end-of-month storage, in acre-feet May June July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. 1992–93 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 1993–94 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 1994–95 .00 .00 .00 -31.85 -144.77 222.56 .00 .00 .00 .00 .00 .00 1995–96 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 1996–97 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 1997–98 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 1998–99 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 1999–2000 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 2000–2001 .00 .00 .00 .00 -1.13 195.78 .00 .00 .00 .00 .00 .00 2001–02 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 2002–03 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 2003–04 .00 .00 .00 .00 .00 -9.31 172.96 .00 .00 .00 .00 .00 2004–05 .00 -10.59 60.28 -58.34 -113.67 -172.39 -221.09 -264.40 -274.04 -273.31 -209.42 113.24 2005–06 .00 .00 .00 .00 -206.18 -226.30 -273.89 -287.14 -304.11 -317.25 -53.58 605.63 Statistical summary Number of values 44 44 44 44 44 44 44 44 44 44 44 44 Mean NA NA NA NA NA NA NA NA NA NA NA NA Maximum NA NA NA NA NA NA NA NA NA NA NA NA 75th percentile .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 50th percentile .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 25th percentile .00 .00 .00 .00 -54.30 -1.32 .00 .00 .00 .00 .00 .00 Minimum -142.37 -189.18 -382.37 -524.07 -664.51 -730.03 -761.97 -810.41 -860.03 -905.68 -582.18 -309.61
Appendix 71

Table 33. Computed values of accumulated end-of-month storage change for release scenario of 3.0 cubic feet per second, 1962–2006.—Continued[Prescribed release is for May through October, with continued releases of 1 cubic foot per second for subsequent months with persisting storage deficits. Negative values indicate storage deficits, which are accumulated. Values of zero indicate a monthend condition at or above the spillway. Positive values are shown only for months when storage deficits end. NA, Not applicable]

Year Computed end-of-month storage, in acre-feet

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

1962–63 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.001963–64 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001964–65 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001965–66 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001966–67 .00 -14.92 99.09 .00 .00 .00 .00 .00 .00 .00 .00 .001967–68 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001968–69 .00 .00 .00 .00 .00 -42.68 134.51 .00 .00 .00 .00 .001969–70 .00 .00 .00 .00 -110.49 17.06 .00 .00 .00 .00 .00 .001970–71 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001971–72 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001972–73 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001973–74 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001974–75 .00 -37.70 -60.25 -157.70 -264.04 -257.36 -84.26 -124.77 -45.03 65.38 .00 .001975–76 .00 .00 .00 .00 -28.29 72.66 .00 .00 .00 .00 .00 .001976–77 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001977–78 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001978–79 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001979–80 .00 .00 .00 .00 -86.82 -84.75 275.41 .00 .00 .00 .00 .001980–81 .00 .00 -97.99 126.57 -123.72 -154.10 21.68 .00 .00 .00 .00 .001981–82 .00 .00 .00 .00 -142.66 -126.24 3.63 .00 .00 .00 .00 .001982–83 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001983–84 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001984–85 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001985–86 -26.59 -.42 -140.50 -316.45 -425.98 -450.47 -314.66 -277.83 -159.86 38.68 .00 .001986–87 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001987–88 .00 .00 .00 .00 -206.01 -409.41 -439.15 -482.14 -520.55 -548.93 -380.27 -124.201988–89 163.49 -112.60 -397.67 -664.61 -906.47 -1,033.47 -1,065.41 -1,113.85 -1,163.47 -1,209.12 -791.03 -613.051989–90 -507.29 -613.60 -868.27 -1,071.45 -1,178.71 -1,371.87 -1,357.13 -1,336.80 -1,349.23 -1,361.24 -1,250.54 -619.551990–91 821.19 .00 .00 .00 -134.28 -224.58 -45.89 124.01 .00 .00 .00 .001991–92 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00
72 Hydrologic Characterization for Spring Creek and Hydrologic Budget and Model Scenarios for Sheridan Lake, S. Dak. Table 33. Computed values of accumulated end-of-month storage change for release scenario of 3.0 cubic feet per second, 1962–2006.—Continued [Prescribed release is for May through October, with continued releases of 1 cubic foot per second for subsequent months with persisting storage deficits. Negative values indicate storage deficits, which are accumulated. Values of zero indicate a monthend condition at or above the spillway. Positive values are shown only for months when storage deficits end. NA, Not applicable] Year Computed end-of-month storage, in acre-feet May June July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. 1992–93 0.00 0.00 0.00 0.00 -34.74 -82.05 27.45 0.00 0.00 0.00 0.00 0.00 1993–94 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 1994–95 .00 .00 .00 -93.33 -265.75 40.10 .00 .00 .00 .00 .00 .00 1995–96 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 1996–97 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 1997–98 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 1998–99 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 1999–2000 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 2000–2001 .00 .00 .00 -21.06 -81.69 53.74 .00 .00 .00 .00 .00 .00 2001–02 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 2002–03 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 2003–04 .00 .00 .00 .00 -8.53 -79.32 102.95 .00 .00 .00 .00 .00 2004–05 .00 -70.09 -60.70 -180.52 -295.35 -415.55 -464.25 -507.56 -517.20 -516.47 -452.58 -189.42 2005–06 249.43 .00 -28.65 16.22 -265.68 -347.28 -394.87 -408.12 -425.09 -438.23 -174.56 484.65 Statistical summary Number of values 44 44 44 44 44 44 44 44 44 44 44 44 Mean NA NA NA NA NA NA NA NA NA NA NA NA Maximum NA NA NA NA NA NA NA NA NA NA NA NA 75th percentile .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 50th percentile .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 25th percentile .00 .00 .00 .00 -113.80 -82.73 .00 .00 .00 .00 .00 .00 Minimum -507.29 -613.60 -868.27 -1,071.45 -1,178.71 -1,371.87 -1,357.13 -1,336.80 -1349.23 -1,361.24 -1,250.54 -619.55
Appendix 73

Table 34. Computed values of accumulated end-of-month storage change for release scenario of 4.0 cubic feet per second, 1962–2006.—Continued[Prescribed release is for May through October, with continued releases of 1 cubic foot per second for subsequent months with persisting storage deficits. Negative values indicate storage deficits, which are accumulated. Values of zero indicate a monthend condition at or above the spillway. Positive values are shown only for months when storage deficits end. NA, Not applicable]

Year Computed end-of-month storage, in acre-feet

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

1962–63 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.001963–64 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001964–65 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001965–66 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001966–67 .00 -74.43 -21.91 581.88 .00 .00 .00 .00 .00 .00 .00 .001967–68 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001968–69 .00 .00 .00 .00 -18.77 -122.94 54.25 .00 .00 .00 .00 .001969–70 .00 .00 .00 .00 -17.00 -103.94 124.57 .00 .00 .00 .00 .001970–71 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001971–72 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001972–73 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001973–74 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001974–75 .00 -97.21 -181.25 -340.19 -506.04 -560.85 -387.75 -428.26 -348.52 -293.65 14.68 .001975–76 .00 .00 .00 .00 -87.80 -48.34 216.40 .00 .00 .00 .00 .001976–77 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001977–78 .00 -54.47 243.15 .00 .00 .00 .00 .00 .00 .00 .00 .001978–79 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001979–80 .00 .00 .00 .00 -146.33 -205.75 154.41 .00 .00 .00 .00 .001980–81 .00 .00 -159.48 3.59 -183.23 -275.10 -99.32 149.80 .00 .00 .00 .001981–82 .00 .00 .00 .00 -202.17 -247.24 -117.37 -62.07 10.34 .00 .00 .001982–83 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001983–84 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001984–85 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001985–86 -88.08 -121.42 -322.99 -560.43 -729.47 -815.45 -679.64 -642.81 -524.84 -381.84 187.42 .001986–87 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001987–88 .00 .00 .00 .00 -265.52 -530.41 -560.15 -603.14 -641.55 -669.93 -501.27 -245.201988–89 -19.00 -191.11 -537.67 -866.10 -1,167.47 -1,355.96 -1,387.90 -1,436.34 -1,485.96 -1,531.61 -1,113.52 -935.541989–90 -891.27 -1,057.09 -1,373.25 -1,637.92 -1,804.69 -2,059.34 -2,044.60 -2,024.27 -2,036.70 -2,048.71 -1,938.01 -1,307.021990–91 72.23 .00 .00 .00 -193.79 -345.58 -166.89 -58.48 113.91 .00 .00 .001991–92 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00
74 Hydrologic Characterization for Spring Creek and Hydrologic Budget and Model Scenarios for Sheridan Lake, S. Dak. Table 34. Computed values of accumulated end-of-month storage change for release scenario of 4.0 cubic feet per second, 1962–2006.—Continued [Prescribed release is for May through October, with continued releases of 1 cubic foot per second for subsequent months with persisting storage deficits. Negative values indicate storage deficits, which are accumulated. Values of zero indicate a monthend condition at or above the spillway. Positive values are shown only for months when storage deficits end. NA, Not applicable] Year Computed end-of-month storage, in acre-feet May June July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. 1992–93 0.00 0.00 0.00 0.00 -94.25 -203.05 -93.55 -29.50 107.69 0.00 0.00 0.00 1993–94 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 1994–95 .00 .00 .00 -154.82 -386.75 -142.39 115.21 .00 .00 .00 .00 .00 1995–96 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 1996–97 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 1997–98 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 1998–99 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 1999–2000 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 2000–2001 .00 .00 .00 -82.55 -202.69 -128.75 234.13 .00 .00 .00 .00 .00 2001–02 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 2002–03 .00 .00 -50.39 -95.48 69.66 .00 .00 .00 .00 .00 .00 .00 2003–04 .00 .00 -17.91 16.94 -68.04 -200.32 -18.05 120.97 .00 .00 .00 .00 2004–05 .00 -129.60 -181.70 -363.01 -537.35 -719.04 -767.74 -811.05 -820.69 -819.96 -756.07 -492.91 2005–06 -115.55 136.65 -90.14 -106.76 -431.95 -575.04 -622.63 -635.88 -652.85 -665.99 -402.32 197.39 Statistical summary Number of values 44 44 44 44 44 44 44 44 44 44 44 44 Mean NA NA NA NA NA NA NA NA NA NA NA NA Maximum NA NA NA NA NA NA NA NA NA NA NA NA 75th percentile .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 50th percentile .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 25th percentile .00 .00 .00 .00 -185.87 -203.73 -36.93 .00 .00 .00 .00 .00 Minimum -891.27 -1,057.09 -1,373.25 -1,637.92 -1,804.69 -2,059.34 -2,044.60 -2,024.27 -2,036.70 -2,048.71 -1,938.01 -1,307.02
Appendix 75

Table 35. Computed values of accumulated end-of-month storage change for release scenario of 5.0 cubic feet per second, 1962–2006.—Continued[Prescribed release is for May through October, with continued releases of 1 cubic foot per second for subsequent months with persisting storage deficits. Negative values indicate storage deficits, which are accumulated. Values of zero indicate a monthend condition at or above the spillway. Positive values are shown only for months when storage deficits end. NA, Not applicable]

Year Computed end-of-month storage, in acre-feet

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

1962–63 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.001963–64 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001964–65 .00 .00 .00 .00 -35.17 -71.24 103.65 .00 .00 .00 .00 .001965–66 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001966–67 .00 -133.93 -142.90 399.40 .00 .00 .00 .00 .00 .00 .00 .001967–68 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001968–69 .00 .00 .00 .00 -78.27 -243.93 -66.74 61.78 .00 .00 .00 .001969–70 .00 .00 .00 .00 -229.50 -224.93 3.58 .00 .00 .00 .00 .001970–71 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001971–72 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001972–73 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001973–74 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001974–75 .00 -156.71 -302.24 -522.67 -748.02 -864.32 -691.22 -731.73 -651.99 -597.12 -288.79 1,131.581975–76 .00 .00 .00 .00 -147.30 -169.33 95.41 .00 .00 .00 .00 .001976–77 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001977–78 .00 -113.97 122.16 .00 .00 .00 .00 .00 .00 .00 .00 .001978–79 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001979–80 .00 .00 .00 .00 -205.83 -326.74 33.42 .00 .00 .00 .00 .001980–81 .00 .00 -220.97 -119.39 -362.12 -515.48 -339.70 -90.58 28.89 .00 .00 .001981–82 .00 .00 .00 .00 -261.67 -368.23 -238.36 -183.06 -172.14 -16.20 388.85 .001982–83 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001983–84 .00 .00 .00 .00 -59.19 121.16 .00 .00 .00 .00 .00 .001984–85 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001985–86 -149.57 -242.41 -505.47 -804.40 -1,032.94 -1,180.41 -1,044.60 -1,007.77 -889.80 -746.80 -177.54 1,064.011986–87 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001987–88 .00 .00 .00 -.10 -325.12 -651.50 -681.24 -724.23 -762.64 -791.02 -622.36 -366.291988–89 -201.58 -433.19 -841.24 -1,231.16 -1,592.03 -1,842.01 -1,873.95 -1,922.39 -1,972.01 -2,017.66 -1,599.57 -1,421.591989–90 -1,438.81 -1,664.13 -2,041.78 -2,367.94 -2,594.21 -2,910.35 -2,895.61 -2,875.28 -2,887.71 -2,899.72 -2,789.02 -2,158.031990–91 -840.27 727.28 .00 .00 -253.29 -466.57 -287.88 -179.47 -68.57 79.22 .00 .001991–92 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00
76 Hydrologic Characterization for Spring Creek and Hydrologic Budget and Model Scenarios for Sheridan Lake, S. Dak. Table 35. Computed values of accumulated end-of-month storage change for release scenario of 5.0 cubic feet per second, 1962–2006.—Continued [Prescribed release is for May through October, with continued releases of 1 cubic foot per second for subsequent months with persisting storage deficits. Negative values indicate storage deficits, which are accumulated. Values of zero indicate a monthend condition at or above the spillway. Positive values are shown only for months when storage deficits end. NA, Not applicable] Year Computed end-of-month storage, in acre-feet May June July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. 1992–93 0.00 0.00 0.00 0.00 -153.75 -324.04 -214.54 -150.49 -74.79 84.92 0.00 0.00 1993–94 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 1994–95 .00 .00 .00 -216.31 -507.74 -324.87 -67.27 163.88 .00 .00 .00 .00 1995–96 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 1996–97 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 1997–98 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 1998–99 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 1999–2000 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 2000–2001 .00 .00 .00 -144.04 -323.68 -311.23 51.65 .00 .00 .00 .00 .00 2001–02 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 2002–03 .00 .00 -111.88 -218.46 -112.82 -163.98 31.66 .00 .00 .00 .00 .00 2003–04 .00 .00 -79.40 -106.04 -233.58 -427.35 -245.08 -167.55 -151.96 -57.84 338.72 .00 2004–05 -10.20 -199.30 -312.89 -555.69 -789.53 -1,032.71 -1,081.41 -1,124.72 -1,134.36 -1,133.63 -1,069.74 -806.58 2005–06 -490.71 -298.01 -449.64 -527.75 -912.44 -1,117.02 -1,164.61 -1,177.86 -1,194.83 -1,207.97 -944.30 -344.59 Statistical summary Number of values 44 44 44 44 44 44 44 44 44 44 44 44 Mean NA NA NA NA NA NA NA NA NA NA NA NA Maximum NA NA NA NA NA NA NA NA NA NA NA NA 75th percentile .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 50th percentile .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 25th percentile .00 .00 .00 -26.59 -255.39 -337.11 -220.50 -105.56 -17.14 .00 .00 .00 Minimum -1,438.81 -1,664.13 -2,041.78 -2,367.94 -2,594.21 -2,910.35 -2,895.61 -2,875.28 -2,887.71 -2,899.72 -2,789.02 -2,158.03
Appendix 77

Table 36. Computed values of accumulated end-of-month storage change for release scenario of 6.0 cubic feet per second, 1962–2006.—Continued[Prescribed release is for May through October, with continued releases of 1 cubic foot per second for subsequent months with persisting storage deficits. Negative values indicate storage deficits, which are accumulated. Values of zero indicate a monthend condition at or above the spillway. Positive values are shown only for months when storage deficits end. NA, Not applicable]

Year Computed end-of-month storage, in acre-feet

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

1962–63 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.001963–64 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001964–65 .00 .00 .00 .00 -94.67 -192.23 -17.34 188.40 .00 .00 .00 .001965–66 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001966–67 .00 -193.43 -263.89 216.92 .00 -8.84 329.17 .00 .00 .00 .00 .001967–68 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001968–69 .00 .00 -10.96 490.59 -137.77 -364.92 -187.73 -59.21 74.20 .00 .00 .001969–70 .00 .00 .00 .00 -289.00 -345.92 -117.41 -49.55 95.09 .00 .00 .001970–71 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001971–72 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001972–73 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001973–74 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001974–75 .00 -216.21 -423.23 -705.15 -99.00 -1,167.79 -994.69 -1,035.20 -955.46 -900.59 -592.26 768.611975–76 .00 .00 .00 .00 -206.80 -290.32 -25.58 186.41 .00 .00 .00 .001976–77 .00 .00 .00 .00 .00 -12.05 194.22 .00 .00 .00 .00 .001977–78 .00 -173.47 1.17 .00 -38.26 76.17 .00 .00 .00 .00 .00 .001978–79 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001979–80 .00 .00 .00 -5.50 -270.83 -453.23 -93.07 116.53 .00 .00 .00 .001980–81 .00 .00 -282.46 -242.37 -544.60 -759.45 -583.67 -334.55 -276.57 -256.73 -106.60 162.301981–82 .00 .00 -27.25 477.45 -321.17 -489.22 -359.35 -304.05 -293.13 -192.73 212.32 .001982–83 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001983–84 .00 .00 .00 .00 -118.69 .17 .00 .00 .00 .00 .00 .001984–85 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001985–86 -211.06 -363.40 -687.95 -1,048.37 -1,336.41 -1,545.37 -1,409.56 -1,372.73 -1,254.76 -1,111.76 -542.50 639.551986–87 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001987–88 .00 .00 .00 -61.59 -446.11 -833.98 -863.72 -906.71 -945.12 -973.50 -804.84 -548.771988–89 -445.55 -736.66 -1,206.20 -1,657.61 -2,077.98 -2,389.45 -2,421.39 -2,469.83 -2,519.45 -2,565.10 -2,147.01 -1,969.031989–90 -2,047.74 -2,332.56 -2,771.70 -3,159.35 -3,445.12 -3,822.75 -3,808.01 -3,787.68 -3,800.11 -3,812.12 -3,701.42 -3,070.431990–91 -1,814.16 -306.11 178.85 .00 -312.79 -587.56 -408.87 -300.46 -189.56 -97.31 306.44 .001991–92 .00 .00 .00 .00 -19.70 -56.08 356.61 .00 .00 .00 .00 .00
78 Hydrologic Characterization for Spring Creek and Hydrologic Budget and Model Scenarios for Sheridan Lake, S. Dak. Table 36. Computed values of accumulated end-of-month storage change for release scenario of 6.0 cubic feet per second, 1962–2006.—Continued [Prescribed release is for May through October, with continued releases of 1 cubic foot per second for subsequent months with persisting storage deficits. Negative values indicate storage deficits, which are accumulated. Values of zero indicate a monthend condition at or above the spillway. Positive values are shown only for months when storage deficits end. NA, Not applicable] Year Computed end-of-month storage, in acre-feet May June July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. 1992–93 0.00 0.00 0.00 0.00 -213.25 -445.03 -335.53 -271.48 -195.78 -91.61 588.60 0.00 1993–94 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 1994–95 .00 .00 -55.99 -333.79 -684.72 -563.34 -305.74 -74.59 170.77 .00 .00 .00 1995–96 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 1996–97 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 1997–98 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 1998–99 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 1999–2000 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 2000–2001 .00 .00 .00 -205.53 -444.67 -493.71 -130.83 87.16 .00 .00 .00 .00 2001–02 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 2002–03 .00 .00 -173.37 -341.44 -295.30 -407.95 -212.31 -111.40 -17.97 152.58 .00 .00 2003–04 .00 .00 -140.89 -229.02 -416.06 -671.32 -489.05 -411.52 -395.93 -357.35 -22.28 384.95 2004–05 -71.69 -320.29 -495.37 -799.66 -1,093.00 -1,397.67 -1,446.37 -1,489.68 -1,499.32 -1,498.59 -1,434.70 -1,171.54 2005–06 -917.16 -783.96 -997.08 -1,136.68 -1,580.87 -1,846.94 -1,894.53 -1,907.78 -1,924.75 -1,937.89 -1,674.22 -1,074.51 Statistical summary Number of values 44 44 44 44 44 44 44 44 44 44 44 44 Mean NA NA NA NA NA NA NA NA NA NA NA NA Maximum NA NA NA NA NA NA NA NA NA NA NA NA 75th percentile .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 50th percentile .00 .00 .00 .00 -28.98 -10.45 .00 .00 .00 .00 .00 .00 25th percentile .00 .00 -34.44 -97.58 -344.89 -511.12 -341.49 -278.73 -191.12 -93.03 .00 .00 Minimum -2,047.74 -2,332.56 -2,771.70 -3,159.35 -3,445.12 -3,822.75 -3,808.01 -3,787.68 -3,800.11 -3,812.12 -3,701.42 -3,070.43
Appendix 79

Table 37. Computed values of accumulated end-of-month storage change for release scenario of 7.0 cubic feet per second, 1962–2006.—Continued[Prescribed release is for May through October, with continued releases of 1 cubic foot per second for subsequent months with persisting storage deficits. Negative values indicate storage deficits, which are accumulated. Values of zero indicate a monthend condition at or above the spillway. Positive values are shown only for months when storage deficits end. NA, not applicable]

Year Computed end-of-month storage, in acre-feet

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

1962–63 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.001963–64 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001964–65 .00 .00 .00 .00 -154.18 -313.22 -138.33 5.92 .00 .00 .00 .001965–66 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001966–67 .00 -252.94 -384.88 34.45 .00 -70.32 267.69 .00 .00 .00 .00 .001967–68 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001968–69 .00 .00 -72.44 367.63 -197.28 -485.91 -308.72 -180.20 -108.28 -6.86 345.82 .001969–70 .00 .00 .00 .00 -348.51 -466.91 -238.40 -170.54 -87.39 80.92 .00 .001970–71 .00 .00 .00 .00 .00 -7.09 443.97 .00 .00 .00 .00 .001971–72 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001972–73 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001973–74 .00 .00 .00 .00 -3.08 -30.22 314.20 .00 .00 .00 .00 .001974–75 .00 -275.72 -544.22 -887.62 -1,231.98 -1,471.25 -1,298.15 -1,338.66 -1,258.92 -1,204.05 -895.72 465.151975–76 .00 .00 .00 .00 -266.31 -411.31 -146.57 3.93 .00 .00 .00 .001976–77 .00 .00 .00 .00 -5.22 -78.75 127.52 .00 .00 .00 .00 .001977–78 .00 -232.98 -119.82 275.63 -97.77 -44.82 197.68 .00 .00 .00 .00 .001978–79 .00 .00 .00 .00 -46.08 -77.06 317.78 .00 .00 .00 .00 .001979–80 -30.90 211.65 .00 -66.98 -391.82 -635.70 -275.54 -65.94 -5.68 105.75 .00 .001980–81 .00 .00 -343.94 -365.33 -727.07 -1,003.40 -827.62 -578.50 -520.52 -500.68 -350.55 -141.151981–82 4,052.52 .00 -88.73 354.49 -380.68 -610.21 -480.34 -425.04 -414.12 -313.72 29.84 .001982–83 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001983–84 .00 .00 .00 .00 -178.20 -120.82 72.39 .00 .00 .00 .00 .001984–85 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .001985–86 -272.54 -484.39 -870.42 -1,292.32 -1,639.87 -1,910.31 -1,774.50 -1,737.67 -1,619.70 -1,476.70 -907.44 274.611986–87 .00 .00 .00 -21.80 293.18 .00 .00 .00 .00 .00 .00 .001987–88 .00 .00 .00 -123.07 -567.10 -1,016.45 -1,046.19 -1,089.18 -1,127.59 -1,155.97 -987.31 -731.241988–89 -689.50 -1,040.12 -1,571.14 -2,084.03 -2,563.91 -2,936.86 -2,968.80 -3,017.24 -3,066.86 -3,112.51 -2,694.42 -2,516.441989–90 -2,656.63 -3,000.96 -3,501.58 -3,950.71 -4,295.99 -4,735.10 -4,720.36 -4,700.03 -4,712.46 -4,724.47 -4,613.77 -3,982.781990–91 -2,787.99 -1,339.45 -915.97 -804.97 -1,177.27 -1,513.52 -1,334.83 -1,226.42 -1,115.52 -1,023.27 -619.52 189.621991–92 .00 .00 .00 .00 -79.21 -177.07 235.62 .00 .00 .00 .00 .00
80 Hydrologic Characterization for Spring Creek and Hydrologic Budget and Model Scenarios for Sheridan Lake, S. Dak. Table 37. Computed values of accumulated end-of-month storage change for release scenario of 7.0 cubic feet per second, 1962–2006.—Continued [Prescribed release is for May through October, with continued releases of 1 cubic foot per second for subsequent months with persisting storage deficits. Negative values indicate storage deficits, which are accumulated. Values of zero indicate a monthend condition at or above the spillway. Positive values are shown only for months when storage deficits end. NA, not applicable] Year Computed end-of-month storage, in acre-feet May June July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. 1992–93 -53.31 130.65 0.00 -10.52 -283.28 -576.54 -467.04 -402.99 -327.29 -223.12 457.09 0.00 1993–94 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 1994–95 .00 .00 -117.47 -456.75 -867.19 -807.29 -549.69 -318.54 -134.67 112.22 .00 .00 1995–96 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 1996–97 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 1997–98 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 1998–99 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 1999–2000 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 2000–2001 .00 .00 .00 -267.01 -565.66 -676.18 -313.30 -95.31 146.50 .00 .00 .00 2001–02 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 2002–03 .00 .00 -234.85 -464.40 -477.77 -651.90 -456.26 -355.35 -323.41 -208.40 416.77 .00 2003–04 .00 .00 -202.37 -351.98 -598.53 -915.27 -733.00 -655.47 -639.88 -601.30 -266.23 141.00 2004–05 -133.17 -441.28 -677.84 -1,043.61 -1,396.46 -1,762.61 -1,811.31 -1,854.62 -1,864.26 -1,863.53 -1,799.64 -1,536.48 2005–06 -1,343.58 -1,269.89 -1,544.49 -1,745.57 -2,249.27 -2,576.82 -2,624.41 -2,637.66 -2,654.63 -2,667.77 -2,404.10 -1,804.39 Statistical summary Number of values 44 44 44 44 44 44 44 44 44 44 44 44 Mean NA NA NA NA NA NA NA NA NA NA NA NA Maximum NA NA NA NA NA NA NA NA NA NA NA NA 75th percentile .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 50th percentile .00 .00 .00 .00 -88.49 -99.78 .00 .00 .00 .00 .00 .00 25th percentile .00 .00 -140.46 -288.25 -566.02 -708.96 -497.68 -408.50 -349.00 -245.77 .00 .00 Minimum -2,787.99 -3,000.96 -3,501.58 -3,950.71 -4,295.99 -4,735.10 -4,720.36 -4,700.03 -4,712.46 -4,724.47 -4,613.77 -3,982.78
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Driscoll and Norton—Hydrologic Characterization for Spring Creek and Hydrologic Budget and Model Scenarios for Sheridan Lake, South Dakota—SIR 2009–5059

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