1.2

Zone 3

3.8

Zone 1

1.1

Zone 5

0.1

Zone 4

2.2 

Zone 2

0.1

Zone 3

2.4

Zone 3

4.3

Zone 2

Qa

Tw

T.

102

N.

T.

101

N.

T.

100

N.

T.

98

N.

T.

97

N.

T.

96

N.

T.

95

N.

T.

99

N.

R. 33 W.

R. 32 W.

R. 30 W.

R. 29 W.

R. 28 W.

R. 27 W.

R. 26 W.

R. 25 W.

R. 79 W.

R. 31 W.

MELLETTE COUNTY

TODD COUNTY

TODD COUNTY

CHERRY COUNTY

TRIPP COUNTY

83

83

18

18

Little

White

Keya Paha River

River

South

Cr

Cr

Cr

ray

Beads

Omaha

Rosebud

Phister

S. Ironwood

Creek

Creek

Lone Tree

Creek

Creek

Soldier Creek

Eagletail

Sand

Creek

Creek

Creek

Creek

Thunder

Creek White

Rock

Spring

Antelope

Eagle

Oak

Creek

Cut

Meat

Creek

Creek

Pine

North Branch

Branch

Creek

Creek

Minnechaduza

Dry Creek

White River

Wood

Carter

Okreek

Parmelee

Mission Antelope

Rosebud

St. Francis

Olsonville

100°45'

100°30'

100°15'

43°

Base from U.S. Geological Survey digital data 1:100,000, 1980, 1982, 1983, 1985

Universal Transverse Mercator projection, zone 14

0 10 5 MILES

0 10 5 KILOMETERS

NEBRASKA

SOUTH DAKOTA

Water-supply well in Oga

Water-supply well in Ari

if

r recharge area 

a

EXPLANATION

Qa

To

R. 33 W.

R. 32 W.

R. 30 W.

R. 29 W.

R. 28 W.

R. 27 W.

R. 31 W.

MELLETTE COUNTY

BENNETT COUNTY

TODD COUNTY

TODD COUNTY

CHERRY COUNTY

JACKSON COUNTY

NEBRASKA

SOUTH DAKOTA

83

83

18

18

Little

White

Keya 

River

South

Cr

Cr

Cr

Gray

Beads

Omaha

Rosebud

Phister

S. Ironwood

Creek

Creek

Lone Tree

Creek

Creek

Soldier Creek

Eagletail

Creek

Creek

Thunder

Creek

White

Rock

Spring

Black

Pipe

Creek

Antelope

Eagle

Oak

Creek

Cut

Meat

Creek

Creek

Pine

North Branch

Branch

Creek

Creek

Minnechaduza

Dry

Creek

White River

Wood

Okreek

Parmelee

Mission Antelope

Rosebud

Blackpipe

St. Francis

Olsonville

Norris

101°15'

101°

100°45'

100°30'

100°15'

43°

43°15'

43°30'

Base from U.S. Geological Survey digital data 1:100,000, 1980, 1982, 1983, 1985

Universal Transverse Mercator projection, zone 14

9

N

T.

95

N.

R. 33 W.

R. 32 W.

R. 30 W.

R. 29 W.

R. 28 W.

R. 27 W.

R. 26 W.

R. 25 W.

R. 79 W.

R. 31 W.

MELLETTE COUNTY

BENNETT COUNTY

TODD COUNTY

TODD COUNTY

CHERRY COUNTY

JACKSON COUNTY

NEBRASKA

SOUTH DAKOTA

83

83

18

Little

White

Keya

Paha

River

River

South

Cr

Cr

Cr

Gray

Beads

Omaha

Rosebud

Phister

S. Ironwood

Creek

Creek

Lone Tree

Creek

Creek Soldier Creek

Eagletail

Sand

Creek

Creek

Creek

Creek

Thunder

Cree

White

Rock

Spring

Black

Pipe

Creek

Antelope

Antelope

Eagle

Cut

Meat

Creek

Pine Creek

North Branch

Branch

Creek

Creek

Minnechaduza

Creek

Dry

Creek

101°15'

101°

100°45'

43°

43°15'

43°30'

Base from U.S. Geological Survey digital data 1:100,000, 1980, 1982, 1983, 1985

Universal Transverse Mercator projection, zone 14 0 10 5 MILES

0 10 5 KILOMETERS

SOUTH

DAKOTA

Study area

Missouri River

Todd

County

Mellette County

EXPLANATION

Rosebud Indian Reservation

White River

Wood

Okreek

Parmelee

Mission Antelope

Rosebud

Olsonville

Blackpipe

St. Francis

Norris

Black

Hills

Sand Hills

Central

Lowland

Great

Plains

Physiographic division boundary

NEBRASKA

SOUTH DAKOTA

Qa

Tw

T.

102

N.

T.

101

N.

T.

100

N.

T.

98

N.

T.

97

N.

T.

96

N.

T.

95

N.

T.

99

N.

R. 32 W.

R. 30 W.

R. 29 W.

R. 28 W.

R. 27 W.

R

26 W

R. 31 W.

MELLETTE COUNTY

BENNETT COUNTY

TODD COUNTY

TODD COUNTY

CHERRY COUNTY

JACKSON COUNTY

TRIPP COUNTY

83

83

18

18

Little

White

Keya

Paha

River

River

South

Cr

Cr

Cr

Gray

Beads

Omaha

Rosebud

Phister

S. Ironwood

Creek

Creek

Lone Tree

Creek

Creek

Soldier Creek

Eagletail

Sand Creek

Creek

Creek

Creek

Thunder

Creek

White

Rock

ng

Black Pipe

Creek

Antelope

Eagle

Oak

Creek

Cut

Meat

Creek

Creek Pine

North Branch

Branch

Creek

Creek

Minnechaduza

Dry

Creek

White River

Wood

Carter

Okreek

Parmelee

Mission Antelope

Rosebud

Blackpipe

St. Francis

Olsonville

Norris

101°15'

101°

100°45'

100°30'

100°15'

43°30'

Geological Survey digital data 1:100,000, 1980, 1982, 1983, 1985

erse Mercator projection, zone 14

13.3

Zone 5

28.1

Zone 3

2.5

Zone 4

0.4

Zone 3

84.4

Zone 3

26.8

Zone 1

5.4

Zone 1

0.2

Zone 2

1.3

Zone 1

25.1

Zone 2

2.8

Zone 3

8.4

Zone 2

Prepared in cooperation with the Rosebud Sioux Tribe 

Simulated Groundwater Flow in the Ogallala and 

Arikaree Aquifers, Rosebud Indian Reservation Area, 

South Dakota—Revisions with Data Through Water 

Year 2008 and Simulations of Potential Future Scenarios

U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2010–5105

Ogallala aquifer

Arikaree aquifer

Eagle Creek

Antelope Creek

Rock Creek

Keya Paha River

Little White River

White River Group

A A'

2,000

2,200

2,400

2,600

ELEVATION, IN FEET ABOVE NATIONAL GEODETIC VERTICAL DATUM OF 1929 (NGVD 29)

2,800

3,000

3,200

FEET

2,000

2,200

2,400

2,600

2,800

3,000

3,200

FEET

WEST EAST

VERTICAL SCALE IS GREATLY EXAGGERATED

Trace of section shown in figures 4 and 5

0 1 2 3 4 MILES Tops of hydrogeologic units modified from Carter (1998)

0 1 2 3 4 KILOMETERS
EXPLANATION

Average hydraulic head in Arikaree aquifer, water years 1979–98

Average hydraulic head in Ogallala aquifer, water years 1979–98

General direction of groundwater flow

EXPLANATION FOR THE COVER ILLUSTRATION 

(figure 6 from this report)
Simulated Groundwater Flow in the Ogallala 

and Arikaree Aquifers, Rosebud Indian 

Reservation Area, South Dakota—Revisions 

with Data Through Water Year 2008 and 

Simulations of Potential Future Scenarios

By Andrew J. Long and Larry D. Putnam

Prepared in cooperation with the Rosebud Sioux Tribe

Scientific Investigations Report 2010–5105

U.S. Department of the Interior

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

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2010

For more information on the USGS—the Federal source for science about the Earth, its natural and living resources, 

natural hazards, and the environment, visit http://www.usgs.gov or call 1-888-ASK-USGS

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Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the 

U.S. Government.

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

reproduce any copyrighted materials contained within this report.

Suggested citation:

Long, A.J., and Putnam, L.D., 2010, Simulated groundwater flow in the Ogallala and Arikaree aquifers, Rosebud Indian 

Reservation area, South Dakota—Revisions with data through water year 2008 and simulations of potential future 

scenarios: U.S. Geological Survey Scientific Investigations Report 2010–5105, 64 p.
iii

Contents

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

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

Purpose and Scope ..............................................................................................................................2

Acknowledgments................................................................................................................................2

Description of Study Area ............................................................................................................................3

Physiography and Land Use ...............................................................................................................4

Drainage Features and Streamflow...................................................................................................4

Geology...................................................................................................................................................5

Hydrologic Setting ................................................................................................................................5

Conceptual Model..........................................................................................................................................9

Groundwater Flow ................................................................................................................................9

Recharge..............................................................................................................................................11

Evapotranspiration..............................................................................................................................13

Discharge to Streams and Springs..................................................................................................13

Well Withdrawals ...............................................................................................................................17

Numerical Model .........................................................................................................................................18

Model Design.......................................................................................................................................18

Grid and Boundary Conditions.................................................................................................18

Hydraulic Conductivity..............................................................................................................19

Recharge.....................................................................................................................................20

Discharge....................................................................................................................................23

Model Calibration................................................................................................................................27

Steady-State Simulation...........................................................................................................28

Transient Simulation..................................................................................................................35

Simulation of Potential Future Scenarios .......................................................................................37

Model Limitations................................................................................................................................38

Summary........................................................................................................................................................52

References Cited..........................................................................................................................................53

Appendix 1 – Wells used for estimating potentiometric surfaces of the Ogallala and Arikaree 

aquifers. ...........................................................................................................................................55

Figures

1–5. Maps showing:

1. Study area.............................................................................................................................3

2. Drainage basins in the study area ....................................................................................4

3. Generalized surficial geology of study area....................................................................8

4. Estimated average potentiometric surface of the Ogallala aquifer..........................10

5. Estimated average potentiometric surface of the Arikaree aquifer .........................11

6. Cross section showing relation between hydraulic head, hydrogeologic units, and 

topographic features..................................................................................................................12

7–16. Maps showing:

7. Streamflow measurement sites for seepage runs during 1999 and 2006.................14

8. Recharge areas and locations of water-supply wells.................................................19
iv

9. Cell types in the Ogallala aquifer (layer 1), observation wells completed in the 

Ogallala aquifer, and row and column widths for the Ogallala and Arikaree 

aquifers................................................................................................................................20

10. Cell types in the Arikaree aquifer (layer 2) and observation wells completed in the 

Arikaree aquifer.................................................................................................................21

11. Estimated horizontal hydraulic conductivity of the Ogallala aquifer, in feet per 

day........................................................................................................................................22

12. Estimated horizontal hydraulic conductivity of the Arikaree aquifer, in feet per 

day........................................................................................................................................23

13. Estimated vertical hydraulic conductivity (K), in feet per day, for the Arikaree 

aquifer in five parameter zones where overlain by the Ogallala aquifer.................26

14. River cells, evapotranspiration zones, spring cells, and water-supply wells in the 

Ogallala and Arikaree aquifers........................................................................................27

15. Potentiometric surface of the Ogallala aquifer for steady-state simulation ...........30

16. Potentiometric surface of the Arikaree aquifer for steady-state simulation...........31

17–20. Graphs showing:

17. Histogram of residuals of average observed and steady-state simulated hydraulic 

head for 383 wells, water years 1979–98 .......................................................................32

18. Linear regression of average observed and simulated steady-state hydraulic 

heads for 383 wells, water years 1979–98 .....................................................................33

19. Relative parameter sensitivities as a fractional change in the objective function 

(sum of the squared weighted residuals) resulting from a 5-percent change in 

parameter values...............................................................................................................37

20. Relative sensitivities of parameter classes as a percent change in the objective 

function (sum of the squared weighted residuals) resulting from a 5-percent 

change in parameter values ............................................................................................38

21–23. Hydrographs showing:

21. Simulated and observed data for State observation wells for calibrated transient 

model ...................................................................................................................................39

22. Simulated and observed data for Tribal observation wells for calibrated transient 

model ...................................................................................................................................44

23. Differences of water levels in wells between results of the calibrated model and 

the assumed potential drought scenario for the 30-year simulation period for 

selected sites for the Ogallala aquifer...........................................................................48

24. Map showing simulated potentiometric surfaces for the calibrated model and the 

drought scenario at the end of a 30-year simulation period for the Ogallala aquifer.....49

25. Hydrographs showing the differences in water levels in wells between results of the 

calibrated model and the scenario of pumping increased by 50 percent for the 30-year 

simulation period for selected sites for the Ogallala aquifer..............................................50

26. Map showing simulated potentiometric surfaces for the calibrated model and the 

scenario of pumping increased by 50 percent at the end of a 30-year simulation period 

for the Ogallala aquifer..............................................................................................................51
v

 Tables

1. Generalized stratigraphic column showing geologic units and hydrologic characteristics ..................................................................................................................................................6

2. Estimated maximum evapotranspiration rate during summer stress periods, water 

years 1979–2008. .........................................................................................................................13

 3. Measured streamflow at selected sites during seepage runs during 1999 and 2006. 

Estimates of base flow for each drainage basin are shown...............................................15

4. Estimated groundwater withdrawals for irrigation and public supply in the study area, 

1979–2008 .....................................................................................................................................17

5. Revisions to the model described by Long and others (2003).............................................18

6. Estimated recharge to the Ogallala aquifer, water years 1979–2008.................................24

7. Selected data for Tribal observation wells in the study area..............................................28

8. Selected data for State observation wells in the study area..............................................29

9. Comparison of steady-state simulated and estimated base flows for six surface-water 

drainage basins...........................................................................................................................32

10. Parameter values estimated by inverse modeling for the steady-state simulation........34

11. Water budget for steady-state simulation compared with the water budget from Long 

and others (2003).........................................................................................................................35

12. Parameter correlation matrix showing correlation coefficients for all parameter pair 

combinations ...............................................................................................................................36

13. Comparison of estimated hydraulic conductivity values for the model described by 

Long and others (2003) and the revised model described in this report ...........................43
vi

Conversion Factors, Abbreviations, 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)

mile, nautical (nmi) 1.852 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 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) 

Flow rate

foot per day (ft/d) 0.3048 meter per day (m/d)

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

gallon per minute (gal/min) 0.06309 liter per second (L/s)

inch per year (in/yr) 25.4 millimeter per year (mm/yr)

Hydraulic conductivity

foot per day (ft/d) 0.3048 meter per day (m/d)

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

°F=(1.8×°C)+32

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 is the 12-month period, October 1 through September 30, and is designated by the 

calendar year in which it ends.
vii

Abbreviations and Acronyms

K hydraulic conductivity

R2 coefficient of determination

RMSE root mean square error

SWUDS U.S. Geological Survey’s Site-Specific Water-Use Data System

USGS U.S. Geological Survey

36

A B

C D

A B

C D

C

A B

C D

D

A B

1 2 3 4 5 6

12 11 10 9 8 7

13 14 15 16 17

24

23

22 21 20 19

25

26 27 28

29

30

18

35

34

33

32 31

R. 28 W. T. 38 N.

MELLETTE COUNTY

TODD COUNTY

SOUTH DAKOTA

NEBRASKA

T. 36 N.

T. 37 N.

T. 38 N.

T. 39 N.

T. 40 N.

T. 41 N.

T. 42 N.

T. 35 N.

R. 31 W.

R. 32 W.

R. 33 W.

R. 27 W.

R. 28 W.

R. 29 W. R. 30 W.

R. 25 W.

R. 26 W.

Well

38N28W36ABCB

The well number consists of the township number, followed by "N," the range number followed by "W," and the 

section number followed by a maximum of four uppercase letters that indicate, respectively, the 160-, 40-, 10-, and 2 

1/2-acre tract in which the well is located. These letters are assigned in a counterclockwise direction beginning with 

"A" in the northeast quarter. A serial number following the last letter is used to distinguish between wells in the same 

2 1/2-acre tract.

Well-Numbering System

Abstract

The Ogallala and Arikaree aquifers are important water 

resources in the Rosebud Indian Reservation area and are 

used extensively for irrigation, municipal, and domestic water 

supplies. Drought or increased withdrawals from the Ogallala 

and Arikaree aquifers in the Rosebud Indian Reservation area 

have the potential to affect water levels in these aquifers. This 

report documents revisions and recalibration of a previously 

published three-dimensional, numerical groundwater-flow 

model for this area. Data for a 30-year period (water years 

1979 through 2008) were used in steady-state and transient 

numerical simulations of groundwater flow. In the revised 

model, revisions include (1) extension of the transient calibration period by 10 years, (2) the use of inverse modeling for 

steady-state calibration, (3) model calibration to base flow for 

an additional four surface-water drainage basins, (4) improved 

estimation of transient aquifer recharge, (5) improved delineation of vegetation types, and (6) reduced cell size near large 

capacity water-supply wells. In addition, potential future 

scenarios were simulated to assess the potential effects of 

drought and increased groundwater withdrawals.

The model comprised two layers: the upper layer represented the Ogallala aquifer and the lower layer represented the 

Arikaree aquifer. The model’s grid had 168 rows and 

202 columns, most of which were 1,640 feet (500 meters) 

wide, with narrower rows and columns near large watersupply wells. Recharge to the Ogallala and Arikaree aquifers 

occurs from precipitation on the outcrop areas. The average 

recharge rates used for the steady-state simulation were 

2.91 and 1.45 inches per year for the Ogallala aquifer and 

Arikaree aquifer, respectively, for a total rate of 255.4 cubic 

feet per second (ft3/s). Discharge from the aquifers occurs 

through evapotranspiration, discharge to streams as base flow 

and spring flow, and well withdrawals. Discharge rates for 

the steady-state simulation were 171.3 ft3/s for evapotranspiration, 74.4 ft3

/s for net outflow to streams and springs, and 

11.6 ft3/s for well withdrawals. Estimated horizontal hydraulic 

conductivity used for the numerical model ranged from 0.2 to 

84.4 feet per day (ft/d) in the Ogallala aquifer and from 0.1 to 

4.3 ft/d in the Arikaree aquifer. A uniform vertical hydraulic 

conductivity value of 4.2x10-4 ft/d was estimated for the Ogallala aquifer. Vertical hydraulic conductivity was estimated for 

five zones in the Arikaree aquifer and ranged from 8.8x10-5 to 

3.7 ft/d. Average rates of recharge, maximum evapotranspiration, and well withdrawals were included in the steady-state 

simulation, whereas the time-varying rates were included in 

the transient simulation.

Inverse modeling techniques were used for steady-state 

model calibration. These methods were designed to estimate 

parameter values that are, statistically, the most likely set of 

values to result in the smallest differences between simulated 

and observed hydraulic heads and base-flow discharges. For 

the steady-state simulation, the root mean square error for 

simulated hydraulic heads for all 383 wells was 27.3 feet. 

Simulated hydraulic heads were within ±50 feet of observed 

values for 93 percent of the wells. The potentiometric surfaces 

of the two aquifers calculated by the steady-state simulation 

established initial conditions for the transient simulation. For 

the transient simulation, the difference between the simulated 

and observed means for hydrographs was within ±40 feet for 

98 percent of 44 observation wells. 

A sensitivity analysis was used to examine the response 

of the calibrated steady-state model to changes in model 

parameters including horizontal and vertical hydraulic conductivity, evapotranspiration, recharge, and riverbed conductance. 

The model was most sensitive to recharge and maximum 

evapotranspiration and least sensitive to riverbed and spring 

conductances.

To simulate a potential future drought scenario, a 

synthetic recharge record was created, the mean of which was 

equal to 64 percent of the average estimated recharge rate 

for the 30-year calibration period. This synthetic recharge 

record was used to simulate the last 20 years of the calibration period under drought conditions. Compared with results 

of the calibrated model, decreases in hydraulic-head values 

for the drought scenario at the end of the simulation period 

Simulated Groundwater Flow in the Ogallala and Arikaree 

Aquifers, Rosebud Indian Reservation Area, South 

Dakota—Revisions with Data through Water Year 2008 

and Simulations of Potential Future Scenarios

By Andrew J. Long and Larry D. Putnam
2 Simulated Groundwater Flow in the Ogallala and Arikaree Aquifers, Rosebud Indian Reservation Area

were as much as 39 feet for the Ogallala aquifer. To simulate 

the effects of potential increases in pumping, well withdrawal 

rates were increased by 50 percent from those estimated for 

the 30-year calibration period for the last 20 years of the 

calibration period. Compared with results of the calibrated 

model, decreases in hydraulic-head values for the scenario of 

increased pumping at the end of the simulation period were as 

much as 13 feet for the Ogallala aquifer.

This numerical model is suitable as a tool to help understand the flow system, to help confirm that previous estimates 

of aquifer properties were reasonable, and to estimate aquifer 

properties in areas without data. The model also is useful to 

help assess the effects of drought and increases in pumping 

by simulations of these scenarios, the results of which are not 

precise but may be considered when making water management decisions.

Introduction

The Ogallala and Arikaree aquifers are included in 

the High Plains aquifer system that underlies parts of eight 

States and extends from southern South Dakota to Texas. 

In 2000, the High Plains aquifer supplied 23 percent of all 

groundwater used for irrigation, public supply, and industry, 

and 30 percent of groundwater used for irrigation in the United 

States (Maupin and Barber, 2005). 

 The High Plains aquifer underlies about 4,750 square 

miles (mi2) in south-central South Dakota (Gutentag and 

others, 1984) including most of the Rosebud Indian Reservation. In this area, the Ogallala and Arikaree aquifers are important water resources and are used extensively for irrigation, 

municipal, and domestic water supplies. From about 1950, 

when little water use for irrigation occurred, to 2007, groundwater storage declines in the High Plains aquifer nationwide 

ranged from 0.6 million acre-feet (acre-ft) in South Dakota to 

140 million acre-ft in Texas (McGuire, 2009). Continued or 

increased withdrawals from the Ogallala and Arikaree aquifers 

in the Rosebud Indian Reservation area have the potential to 

affect water levels in these aquifers and base-flow discharge to 

area streams.

The Rosebud Sioux Tribe has identified a need for 

water-resource tools to evaluate management issues associated with the Ogallala and Arikaree aquifers, such as planning 

for source-water protection, describing potential effects of 

contamination, and evaluating effects of drought cycles. A 

primary tool conceived by the Tribe was a numerical groundwater-flow model of these aquifers for the Rosebud Indian 

Reservation. Therefore, the Tribe has worked in cooperation 

with the U.S. Geological Survey (USGS) to develop an initial 

model (Long and others, 2003) and more recently to revise the 

model with data through September 30, 2008. 

Model revisions include (1) extension of the transient 

calibration period by 10 years to include data measured 

through 2008, (2) the use of inverse modeling for steady-state 

calibration that minimized the squares of the differences 

between measured and simulated flow metrics, (3) model 

calibration to base flow for an additional four surface-water 

drainage basins, (4) improved estimation of transient aquifer 

recharge using a method that considers antecedent rainfall 

effects, (5) improved estimation of vegetation types based on 

satellite imagery for evapotranspiration processes, and 

(6) reduced cell size near municipal water-supply wells. In 

addition, potential future scenarios were simulated to assess 

the effects of potential future hydrologic stresses such as 

drought conditions and increased groundwater withdrawals. 

Purpose and Scope

The purpose of this report is to describe a conceptual 

and numerical model developed to simulate groundwater flow 

in the Ogallala and Arikaree aquifers in the Rosebud Indian 

Reservation area. The numerical model is a revision of that 

described in Long and others (2003). Steady-state simulation of average conditions (based on measured data for water 

years 1979–1998) was used for model calibration. Transient 

simulations were executed for a 30-year period of measured 

data consisting of water years 1979–2008 (October 1, 1978, 

through September 30, 2008). For convenience of the reader, 

much of the background material and description of the 

conceptual model covered in the report by Long and others 

(2003) is included in this report. 

Acknowledgments

The authors would like to recognize important contributions by the Rosebud Sioux Tribe to the development of 

the groundwater-flow model described in this report. Development of a calibrated numerical model has resulted from 

the Tribe’s long-term commitment to obtaining hydrologic 

information, which has been obtained through a series of 

water-resource investigations that the Tribe has participated in 

and by data-collection networks operated or supported by the 

Tribe. Characterization of the Ogallala and Arikaree aquifers 

was enabled by a substantial program of test-hole drilling and 

installation of observation wells that was a major component 

of a water-resource investigation (Carter, 1998) involving the 

USGS, Rosebud Sioux Tribe, and Geological Survey Program 

of the South Dakota Department of Environment and Natural 

Resources. Water-level data from the resulting network of 

observation wells and from other State and Tribal observation 

wells have been instrumental for calibration of the numerical 

model. Tribal support and involvement in collection of streamflow data has been critical for estimation of groundwater 

discharge rates. The Tribe also was actively involved in study 

design, conceptualization of the groundwater-flow system, 

technical evaluation of model performance, and review of this 

report.
Description of Study Area 3

Description of Study Area

The study area includes areas within and immediately 

surrounding the Rosebud Indian Reservation where the Ogallala and Arikaree aquifers are present (fig. 1). The original 

boundaries of the Rosebud Indian Reservation included all 

or nearly all of Mellette, Todd, Tripp, and Gregory (east of 

Tripp) Counties, and a small portion of Lyman County (east 

of northern Tripp County). Various revisions to the Rosebud 

Indian Reservation boundary have occurred (Carter, 1998); the 

boundary was revised to include only Todd County in 1975 

(fig. 1).

Figure 1. Study area (from Long and others, 2003; physiographic divisions modified from Fenneman, 1946; Flint, 1955).

T.

102

N.

T.

101

N.

T.

100

N.

T.

98

N.

T.

97

N.

T.

96

N.

T.

95

N.

T.

99

N.

R. 33 W. R. 32 W. R. 31 W. R. 30 W. R. 29 W. R. 28 W. R. 27 W. R. 26 W. R. 25 W. R. 79 W.

MELLETTE COUNTY

BENNETT COUNTY

TODD COUNTY

TODD COUNTY

CHERRY COUNTY

JACKSON COUNTY

TRIPP COUNTY

NEBRASKA

SOUTH DAKOTA

83

83

18

18

Little

White

Keya Paha

River

River

South

Cr

Cr

Cr

Gray

Beads

Omaha

Rosebud

Phister

S. Ironwood Creek

Creek

Lone Tree

Creek

Creek Soldier Creek

Eagletail

Sand Creek

Creek

Creek

Creek

Thunder

Creek

White

Rock

Spring

Black

Pipe

Creek

Antelope

Antelope

Eagle

Oak

Creek

Cut

Meat

Creek

Creek

North

Pine

Branch

Branch

Creek

Creek

Minnechaduza

Creek

Dry

Creek

101°15' 101° 100°45' 100°30' 100°15'

43°

43°15'

43°30'

Base from U.S. Geological Survey digital data 1:100,000, 1980, 1982, 1983, 1985

Universal Transverse Mercator projection, zone 14

0 5 10 MILES

0 5 10 KILOMETERS

SOUTH DAKOTA

Study area

Missouri River

Todd

County

Mellette County

EXPLANATION

Rosebud Indian Reservation

White River

Wood

Okreek Carter

Parmelee

Mission Antelope

Rosebud

Olsonville

Blackpipe

St. Francis

Norris

Black

Hills

Sand Hills

Central

Lowland

Great

Plains

Physiographic division boundary
4 Simulated Groundwater Flow in the Ogallala and Arikaree Aquifers, Rosebud Indian Reservation Area

Physiography and Land Use

The northern part of the study area is in the Great Plains 

physiographic province, and the southern part is in the Sand 

Hills physiographic province (fig. 1). Much of the study 

area has rolling topography, and numerous deep valleys 

drain into the White River to the north. Agriculture is the 

primary land use within the study area. Cattle ranching is the 

primary agricultural activity with most land used for grazing 

or hay production. Less than 15 percent of the land is used 

for crops, which include wheat, sorghum, oats, corn, and 

alfalfa (Springer, 1974). Most of the crop land is located in 

south-central Todd County, where extensive irrigation from 

the Ogallala aquifer occurs. The climate is subhumid with an 

annual precipitation of about 20 inches (National Climatic 

Data Center, 2010; Mission station 395620 in Todd County). 

About 8 percent of the average annual precipitation becomes 

streamflow; however, this quantity varies because of climatic 

conditions (Carter, 1998).

Drainage Features and Streamflow

The major streams that drain the study area (fig. 2) are 

the Little White River, which flows into the White River in 

Figure 2. Drainage basins in the study area (from Long and others, 2003).

T.

102

N.

T.

101

N.

T.

100

N.

T.

98

N.

T.

97

N.

T.

96

N.

T.

95

N.

T.

99

N.

R. 33 W. R. 32 W. R. 31 W. R. 30 W. R. 29 W. R. 28 W. R. 27 W. R. 26 W. R. 25 W. R. 79 W.

MELLETTE COUNTY

BENNETT COUNTY

TODD COUNTY

TODD COUNTY

CHERRY COUNTY

JACKSON COUNTY

TRIPP COUNTY

NEBRASKA

SOUTH DAKOTA

White River

Wood

Okreek Carter

Parmelee

Mission Antelope

Rosebud

Blackpipe

St. Francis

Olsonville

Norris

83

83

18

18

Little

White

Keya Paha

River

River

South

Cr

Cr

Cr

Gray

Beads

Omaha

Rosebud

Phister

S. Ironwood Creek

Creek

Lone Tree

Creek

Creek

Soldier Creek

Eagletail

Sand Creek

Creek

Creek

Creek

Thunder

Creek

White

Rock

Spring

Black

Pipe

Creek

Antelope

Antelope

Eagle

Oak

Creek

Cut

Meat

Creek

Creek

North

Pine

Branch

Branch

Creek

Creek

Minnechaduza

Creek

Dry

Creek

Keya Paha River

Minnechaduza

Creek

White

Thunder

Creek

Black

Pipe

Creek

Little

Dog

Creek

Oak

Creek

Little White River

Keya Paha River

Minnechaduza

Creek

White

Thunder

Creek

Black

Pipe

Creek

Little

Dog

Creek

Oak

Creek

Louis Creek

White River Basin

Niobrara River Basin Niobrara River Basin

101°15' 101° 100°45' 100°30' 100°15'

43°

43°15'

43°30'

Base from U.S. Geological Survey digital data 1:100,000, 1980, 1982, 1983, 1985

Universal Transverse Mercator projection, zone 14

EXPLANATION

Drainage basin boundary

Drainage subbasin boundary

0 5 10 MILES

0 5 10 KILOMETERS
Description of Study Area 5

northern Mellette County, and the Keya Paha River, which 

flows into the Niobrara River in Nebraska. Groundwater 

discharge from the Ogallala and Arikaree aquifers provides 

base flow to the Little White River, Keya Paha River, and 

several smaller creeks. These streams generally receive more 

than one-half of their flow from groundwater discharge, especially during the winter months (Carter, 1998). Direct runoff is 

the largest component of streamflow for streams with minimal 

discharge from the Ogallala and Arikaree aquifers. In addition, numerous ephemeral springs occur along the Little White 

River.

Geology

The exposed rocks and sediments in the study area range 

from sedimentary rocks of Cretaceous age to unconsolidated 

deposits of Quaternary age. Deeper rocks include rocks of 

Precambrian age, the Ordovician-age Red River and Winnipeg 

Formations, the Mississippian-age Madison Limestone, and 

the Permian- and Pennsylvanian-age Minnelusa Formation. 

Cretaceous-age rocks include the Inyan Kara Group, Skull 

Creek Shale, Dakota Formation, Graneros Shale, Greenhorn 

Formation, Carlile Shale, Niobrara Formation, and Pierre 

Shale. Tertiary-age rocks include the White River Group, 

Arikaree Formation, and Ogallala Formation. Unconsolidated 

deposits include terrace, windblown, and alluvial deposits 

(table 1). 

The following descriptions of the Arikaree and Ogallala 

Formations are from Ellis and others (1971). The Arikaree 

Formation consists of silicified claystone, silty clays, siltstone, and poorly consolidated sandstone, all of which are 

a light pinkish tan. The basal 50 to 150 feet (ft) generally is 

composed of silty and sandy beds that commonly are separated from the upper clayey part by 5 to 10 ft of thin-bedded 

limestone. Thickness of the Arikaree Formation ranges from 

0 to 620 ft. The Arikaree Formation forms gently rolling grasscovered hills similar to those formed by the Ogallala Formation, but the banks formed by the Arikaree Formation along 

streams commonly are steeper.

The Ogallala Formation consists of an upper unit 

composed of well-cemented, fine- to medium-grained sandstone and a lower unit composed of poorly consolidated clay, 

silt, and sand. The contact between the units commonly is 

marked by a bed of silty volcanic ash in the base of the upper 

unit. This marker bed ranges in thickness from 1 to 4 ft. 

Locally, however, silty limestone or gravel beds may 

be found at the base of the upper unit. The composition of the 

beds in the lower unit ranges from silty clay to coarse sand 

and varies vertically and horizontally. A 5- to 20-ft thick bed 

of coarse sand and gravel commonly occurs in the basal part 

of the lower unit. Thickness of the upper unit ranges from 

0 to 40 ft and the lower unit ranges from 0 to 200 ft. The upper 

unit forms the caprock on the isolated buttes and ridges in 

the southeastern and northwestern parts of Todd County. The 

lower unit forms the gently rolling grasslands in south-central 

Todd County. The upper unit of the Ogallala Formation also is 

known as the Ash Hollow Formation, and the lower unit also 

is known as the Valentine Formation.

Hydrologic Setting

The shallow aquifers in the study area are the alluvial, 

Ogallala, Arikaree, and White River aquifers. These shallow 

aquifers consist primarily of unconsolidated sand and gravel 

or poorly consolidated sandstones and siltstones. The deeper, 

bedrock aquifers are the Pierre, Dakota Sandstone, Inyan 

Kara, Minnelusa, and Madison aquifers. In the southern part 

of the study area, groundwater generally can be obtained from 

shallow wells (less than 300 ft) completed in Quaternary-age 

alluvial deposits or in Tertiary-age deposits (Ogallala Formation, Arikaree Formation, or White River Group). Groundwater is more difficult to obtain in the northern part of the 

study area where the Tertiary deposits have been eroded resulting in surface exposure of the Pierre Shale (fig. 3). 

The Ogallala aquifer comprises the saturated sandstone 

and silt of the Ogallala Formation. The upper unit of the Ogallala Formation has relatively low permeability, but small seeps 

occur near its base (Ellis and others, 1971). The lower unit of 

the Ogallala Formation generally is water bearing; however, 

the permeability of that unit varies with lithology (Ellis and 

others, 1971).

The Ogallala aquifer is present throughout most of the 

southern part of the study area where it underlies 950 mi2 in 

Todd County with an estimated 17 million acre-ft of water in 

storage (Carter, 1998). The Ogallala aquifer is not present in 

the northern part of the study area. The saturated thickness of 

the Ogallala aquifer in the study area averages 137 ft (Carter, 

1998), and the aquifer is fully saturated in some areas. In 

the study area, the aquifer generally is thickest in the central 

part of Todd County where withdrawals from the aquifer for 

irrigation are highest. The Ogallala aquifer is overlain by 

unconsolidated deposits consisting of alluvium near streams 

and windblown sand deposits composed of fine- to mediumgrained sand, similar to that of the Ogallala Formation, in the 

southwestern part of the study area (fig. 3).

The Ogallala aquifer is unconfined except in the southwestern part of the study area where the aquifer is confined by 

well-cemented layers or concretion beds in the upper part of 

the formation (Carter, 1998). Where unconfined, the depth to 

water ranges from 0 to greater than 150 ft below land surface 

(Carter, 1998). In some areas, the water table in the Ogallala aquifer can be considerably above the altitude of stream 

bottoms, and numerous seeps occur along hillsides and cliffs 

in these areas. The Ogallala aquifer has the highest yield 

potential of all aquifers in the study area with wells yielding 

from 1 to 1,250 gallons per minute (gal/min; Carter, 1998). 

Long and others (2003) estimated hydraulic conductivity to be 

in the range of 0.2–120 feet per day (ft/d).

The Arikaree aquifer generally comprises the saturated 

sandstones and siltstones of the Arikaree Formation. The 
Table 1. Generalized stratigraphic column showing geologic units and hydrologic characteristics. [From Carter, 1998] Era System Formation or deposit Thickness (feet) Description and origin Hydrologic characteri

Cenozoic

Quaternary

Alluvium 0–35 Brown, varies between clay, silts, fine to coarse sand, 

and gravel. Generally sandy along the Little White River and other streams that flow over deposits of Tertiary age. Generally clayey with some thin sand beds along intermittent streams that flow over the Pierre Shale. Fluvial.

Locally, deposits are moderately permeable a

and relatively impermeable along streams Shale. Yields generally are adequate to supwells except along streams that flow over tfresh, low in concentrations of dissolved sately hard except in deposits underlain by 

Windblown sand 

deposits

0–150 Brown, unconsolidated, very fine to medium grained, 

uniform, quartz sand; characterized by dune topography and blowouts. Eolian.

Generally very permeable and water bearing; 

ply stock and domestic wells except where 

Terrace deposits 0–105 Brown, silty clay, sand, and gravel. Commonly, the 

silty and sandy layers are partly cemented, and the gravel and sand beds commonly are interbedded with laminated silty clay. Fluvial.

Generally water bearing in the basal portion 

usually adequate to supply stock and domelow in concentrations of dissolved solids, aexcept in areas where the water-bearing dePierre Shale.

Tertiary

Ogallala Formation 0–240 Tan to olive, fine- to medium-grained sandstone with 

some silty clay. Upper unit of Ogallala Formation also is known as the Ash Hollow Formation and the lower unit as the Valentine Formation. Fluvial.

The upper part of the formation generally has 

small seeps occur near its base. The lower be very permeable and generally is water-bto supply stock and domestic wells and can some areas. Water is fresh, low in concentrand soft to moderately hard.

Arikaree Formation 0–620 Pinkish tan to red; consists of poorly consolidated, 

tuffaceous sandstone, siltstone, shale, and silty clay. The Rosebud Formation sometimes is differentiated as a unit within the Arikaree Formation. Basal unit is composed mostly of silts and sands. Fluvial.

The upper part of the formation generally has 

yield small amounts of water from fractureThe basal part is moderately permeable andomestic and stock wells. Water is fresh, losolved solids, and soft to moderately hard.

White River Group 

(undifferentiated)

0–470 Yellow to brown, poorly consolidated siltstone and 

claystone with some beds of fine sand. Units of the White River Group sometimes are differentiated into the Brule and Chadron Formations. Fluvial.

Permeability varies from low to moderate, de

content. Yields are usually adequate to supdomestic wells. Water is slightly saline, modissolved solids, and hard depending on thto the Pierre Shale.
Table 1. Generalized stratigraphic column showing geologic units and hydrologic characteristics.—Continued[From Carter, 1998]

Era System Formation or deposit Thickness (feet) Description and origin Hydrologic chara

Mesozoic

Cretaceous

Pierre Shale 600–1,395 Bluish-black shale with some layers of bentonite. Marine. Most of the formation is relatively im

small amounts of water if fractureent. Typically not considered an ain concentrations of dissolved soli

Niobrara Formation 125–175 Tan to gray, highly calcareous shale. Commonly described by drillers as “chalk.” Marine. Water-bearing traits are largely unkn

water for some purposes.

Carlile Shale 300–400 Light grayish blue to black, noncalcareous shale. Marine. Very low permeability. Water-bearinGreenhorn Formation 100–120 Tan, bluish, white, or gray calcareous shale. Marine. Water-bearing traits are largely unknGraneros Shale 130–200 Dark-gray non-calcareous shale. Marine. Very low permeability. Water-bearinDakota Formation 

(Dakota Sandstone)

270–340 Interbedded tan to white sandstone and dark-colored 

shale. Sandstone is composed of loose to wellcemented, very fine to coarse quartz sand; cement most commonly is calcium carbonate. Marine.

Permeable sandstone beds yield mod

under artesian pressure for stock awater is highly mineralized and capurposes.

Skull Creek Shale 95–150 Dark bluish-gray shale. Marine. Very low permeability. Water-bearinInyan Kara Group 

(undifferentiated)

100–275 White to light-gray or tan sandstone and siltstone; contains beds of gray to black and reddish to buff shale. 

The Inyan Kara Group sometimes is divided into the Fall River and Lakota Formations. Continental to marginal marine.

Permeable sandstone beds yield mod

under artesian pressure for stock awater is highly mineralized and capurposes.

Paleozoic

Permian and 

PennsylvanianMinnelusa Formation 300–530 Consists of interbedded sandstone, siltstone, dolomite, limestone, anhydrite, and shale. Marine. Permeable zones can yield adequate 

tic wells under artesian pressure. Wsolids than the Dakota Sandstone Can be used for irrigation on cropwith proper salinity management.

MississippianMadison Formation 90–240 Light gray to buff, varies from pure limestone to pure do- lomite with various combinations of the two. Marine. Permeable zones can yield adequate 

tic wells under artesian pressure. Wsolids than the Dakota Sandstone Can be used for irrigation on cropwith proper salinity management.

 Ordovician Red River and Win- nipeg Formations (undifferentiated) 0–170 The Red River Formation mostly consists of dolomite, and the Winnipeg Formation mostly consists of sand- stones. Marine. Water-bearing traits largely unknown

vicinity of study area.

Precambrian Granite. Water-bearing traits largely unknown

vicinity of study area.
8 Simulated Groundwater Flow in the Ogallala and Arikaree Aquifers, Rosebud Indian Reservation Area

Ogallala aquifer, where present, overlies the Arikaree aquifer 

in the study area except in the extreme eastern part of Todd 

County where the Arikaree Formation does not exist. Beds in 

the upper clayey part of the Arikaree Formation are composed 

of relatively low-permeability material, but generally yield 

water from fractures, joints, and thin silty zones (Ellis and 

others, 1971). The basal sandy and silty part of the formation 

is moderately permeable (Ellis and others, 1971). Long and 

others (2003) estimated hydraulic conductivity to be in the 

range of 0.1–5.4 ft/d.

EXPLANATION

Qa

Qa

Qa

Qa

Qa

Qa

Qa

Qa

Qa

Kp

Kp Kp

Kp

Qwd

Qwd Qwd

To

To To

To

Ta

Ta Ta

Ta

Tw

Tw

Tw

Tw

Quaternary-age unconsolidated deposits

Alluvium and terrace deposits

Windblown sand deposits

Tertiary-age sedimentary deposits

Ogallala Formation

Arikaree Formation

White River Group

Cretaceous-age sedimentary deposits

Pierre Shale

T.

102

N.

T.

101

N.

T.

100

N.

T.

98

N.

T.

97

N.

T.

96

N.

T.

95

N.

T.

99

N.

R. 33 W. R. 32 W. R. 31 W. R. 30 W. R. 29 W. R. 28 W. R. 27 W. R. 26 W. R. 25 W. R. 79 W.

MELLETTE COUNTY

BENNETT COUNTY

TODD COUNTY

TODD COUNTY

CHERRY COUNTY

JACKSON COUNTY

TRIPP COUNTY

NEBRASKA

SOUTH DAKOTA

83

83

18

18

Little

White

Keya Paha

River

River

South

Cr

Cr

Cr

Gray

Beads

Omaha

Rosebud

Phister

S. Ironwood Creek

Creek

Lone Tree

Creek

Creek

Soldier Creek

Eagletail

Sand Creek

Creek

Creek

Creek

Thunder

Creek

White

Rock

Spring

Black

Pipe

Creek

Antelope

Antelope

Eagle

Oak

Creek

Cut

Meat

Creek

Creek

North

Pine

Branch

Branch

Creek

Creek

Minnechaduza

Creek

Dry

Creek

White River

Wood

Okreek Carter

Parmelee

Mission Antelope

Rosebud

Blackpipe

St. Francis

Olsonville

Norris

101°15' 101° 100°45' 100°30' 100°15'

43°

43°15'

43°30'

Base from U.S. Geological Survey digital data 1:100,000, 1980, 1982, 1983, 1985

Universal Transverse Mercator projection, zone 14

0 5 10 MILES

0 5 10 KILOMETERS

Figure 3. Generalized surficial geology of study area (modified from Ellis and others, 1971).
Conceptual Model 9

The Arikaree aquifer underlies 1,360 mi2 in Todd and 

Mellette Counties with an estimated 50 million acre-ft of 

water in storage (Carter, 1998). The thickness of the Arikaree aquifer ranges from 0 to 618 ft, with an average of 290 ft 

(Carter, 1998). In the study area, the Arikaree aquifer is thickest in southern Todd County. Hydraulic heads in the Arikaree 

aquifer range from 0 to greater than 150 ft below land surface 

(Carter, 1998). Like the Ogallala aquifer, the water table in 

the Arikaree aquifer can be considerably higher in some areas 

than the altitude of stream bottoms, and numerous seeps occur 

along hillsides and cliffs in these areas. Well yields range from 

1 to 1,005 gal/min depending on clay content in the aquifer, 

consolidation of the materials, and well construction; yields 

generally are less than those from the Ogallala aquifer but are 

substantially greater than yields from the underlying White 

River aquifer (Carter, 1998).

Conceptual Model

The windblown sand deposits overlying the Ogallala 

aquifer in the southwestern part of the study area have similar 

hydrogeological properties and are in direct connection with 

the Ogallala aquifer, and therefore, these units are conceptualized as a single water-bearing unit. The Ogallala and Arikaree 

aquifers were assumed to be hydraulically connected with the 

limiting factor of the low permeability of the Arikaree aquifer, 

which is enhanced by fractures. The White River Group 

contains an aquifer but was considered an underlying confining unit because of numerous clay lenses that impede vertical 

groundwater movement. 

Recharge to the Ogallala and Arikaree aquifers occurs 

from precipitation on the outcrop areas, and regional flow 

enters the study area from the west. Groundwater originating from precipitation recharge moves from areas of higher 

altitude toward streams that gain flow from the Ogallala and 

Arikaree aquifers. Discharge by evapotranspiration from the 

aquifers occurs in areas where the water table is near the land 

surface, which generally occurs in topographically low areas. 

Many of the springs that discharge along the banks of the 

Little White and Keya Paha Rivers probably flow from the 

Ogallala aquifer because the Arikaree aquifer generally has 

lower permeability than the Ogallala aquifer. The Arikaree 

aquifer discharges to springs and seeps on the northern boundary of the aquifer where the surface drainage is towards the 

north. In addition, discharge from the aquifers occurs through 

withdrawals from irrigation, public supply, domestic, and 

stock wells.

For analysis of groundwater flow, data for a 30-year 

period (water years 1979–2008) were analyzed. Each water 

year was subdivided into three periods (hereinafter referred to 

as stress periods) for a total of 90 stress periods for analysis 

based on the hydrologic characteristics of each period: (1) a 

fall and winter period, which included the months of October 

through February; (2) a spring period, which included the 

months of March through May; and (3) a summer period, 

which included the months of June through September. The 90 

stress periods are numbered 1 through 90 starting with the fall 

and winter period of water year 1979. During most of the fall 

and winter period, evapotranspiration is very small because 

the ground is frozen, plant growth is limited, and precipitation 

is less than in the spring or summer periods. During the spring 

period, precipitation is greater than during the fall and winter 

period, and the evapotranspiration rate is less than during the 

summer period. During the summer period, evapotranspiration 

is greatest and irrigation withdrawals are largest.

Groundwater Flow

Carter (1998) constructed average potentiometric surfaces 

for the Ogallala and Arikaree aquifers for water years 1979–98 

and evaluated hydraulic gradients, flow directions, and aquifer 

boundaries. Long and others (2003) revised these potentiometric surfaces (figs. 4 and 5). Water levels measured during 1996 

for more than 350 wells, primarily domestic, open to the Ogallala and Arikaree aquifers were documented by Carter (1998). 

Water levels also are available for 44 Tribal and State observation wells open to the Ogallala and Arikaree aquifers for 

1979–2008. Of these, 21 are maintained by the Rosebud Sioux 

Tribe (Rosebud Sioux Tribe, written commun., 2009), and 23 

are maintained by the South Dakota Department of the Environment and Natural Resources (Ken Buhler, South Dakota 

Department of the Environment and Natural Resources, 

written commun., 2009). During water years 1979–2008, some 

of these water levels increased, some decreased, and some had 

little change. Water levels changed as much as 6 and 12 ft for 

Ogallala and Arikaree aquifers, respectively. There was little, 

if any, change in general water-level trends from 1999 to 2008 

in comparison to the previous 20 years. This is consistent with 

estimated water-level changes for the High Plains aquifer in 

South Dakota, where the area-weighted water-level change 

from 1950 to 2007 was 0 ft, the change from 2005–06 was 

0.2 ft, and the change from 2006–07 was -0.2 ft (McGuire, 

2009). Additional information regarding water-level trends in 

the study area is in the “Transient Simulation” section of this 

report. 

Water levels generally fluctuated between 1 and 4 ft 

seasonally. Hydraulic head in the Ogallala aquifer ranged 

from about 3,000 ft on the western boundary of the study area 

to about 2,400 ft on the eastern boundary (fig. 4). Hydraulic 

head in the Arikaree aquifer ranged from about 3,000 ft in the 

southwestern corner of the study area to about 2,400 ft in parts 

of the northern and eastern boundaries of the aquifer (fig. 5). 

Information on wells used to estimate potentiometric surfaces 

is in Appendix 1.

Groundwater flow in the Ogallala and Arikaree aquifers 

in the study area generally is to the east or northeast. Locally, 

groundwater flow is topographically controlled and is towards 

the Little White and Keya Paha Rivers or smaller streams 

(figs. 4 and 5). Domestic water use is small in comparison to 
10 Simulated Groundwater Flow in the Ogallala and Arikaree Aquifers, Rosebud Indian Reservation Area

irrigation, and municipal water-supply wells have little local 

effect on groundwater flow. Groundwater flows from recharge 

areas towards streams and topographically low areas where 

discharge occurs as base flow to streams or evapotranspiration. 

The relation between hydraulic heads and topographic features 

(fig. 6) shows the local influence of streams on the direction of 

groundwater flow. In particular, the Little White River, which 

is deeply incised into the Ogallala aquifer and to a lesser 

extent into the Arikaree aquifer, strongly influences groundwater flow. The Keya Paha River is hydraulically connected to 

the Arikaree aquifer (fig. 3), and tributary streams gain water 

from the Ogallala aquifer. A comparison between the surfacedrainage basins (fig. 2) and the potentiometric surfaces (figs. 

4 and 5) shows that groundwater divides are related to the 

surface-drainage basins.

T.

102

N.

T.

101

N.

T.

100

N.

T.

98

N.

T.

97

N.

T.

96

N.

T.

95

N.

T.

99

N.

R. 33 W. R. 32 W. R. 31 W. R. 30 W. R. 29 W. R. 28 W. R. 27 W. R. 26 W. R. 25 W. R. 79 W.

MELLETTE COUNTY

BENNETT COUNTY

TODD COUNTY

TODD COUNTY

CHERRY COUNTY

JACKSON COUNTY

TRIPP COUNTY

NEBRASKA

SOUTH DAKOTA

White River

Wood

Okreek Carter

Parmelee

Mission Antelope

Rosebud

Blackpipe

St. Francis

Olsonville

Norris

83

83

18

18

Little

White

Keya Paha

River

River

South

Cr

Cr

Cr

Gray

Beads

Omaha

Rosebud

Phister

S. Ironwood Creek

Creek

Lone Tree

Creek

Creek

Soldier Creek

Eagletail

Sand Creek

Creek

Creek

Creek

Thunder

Creek

White

Rock

Spring

Black

Pipe

Creek

Antelope

Antelope

Eagle

Oak

Creek

Cut

Meat

Creek

Creek

North

Pine

Branch

Branch

Creek

Creek

Minnechaduza

Creek

Dry

Creek

101°15' 101° 100°45' 100°30' 100°15'

43°

43°15'

43°30'

Base from U.S. Geological Survey digital data 1:100,000, 1980, 1982, 1983, 1985

Universal Transverse Mercator projection, zone 14

0 5 10 MILES

0 5 10 KILOMETERS

2,700

2,700

2,650

2,750 2,600

2,800

2,800

2,900

2,950

2,550

2,500

3,000

2,450

2,400

3,050

2,850

2,850

2750

2,500

2,5002,450

2,450

2,900

2,900

3,050

2,800

3,000

2,850

2,500

2,750

2,700

2,550

2,550

2,400

2,400

2,800

,,

2,623

2,686 2,607

2,514

2,753 2,669 2,707

2,579 2,677

2,467

2,601

2,665

2,819

2,773

2,756

2,815

2,785

2,821

2,809

2,843

2,848

2,823

2,916

2,947

2,742 2,803

2,812

2,768

2,732

2,750

2,729

2,791 2,740

2,662

2,601

2,467

2,711

2,778

2,594

2,660

2,815

2,850

2,489

2,623

2,434 2,666

2,576 2,678

3,032 2,893 2,785 2,709 2,650

2,744 2,623 3,035 2,850 2,815 2,831 2,913 2,705 2,573 2,698,

2,686

2,496

2,711 2,619 2,818

2,975 2,496

2,875 2,780

2658 2,832 2,791 2,821

2,927 2,628 2,809 2,603 2,510

2,679 2,834 2,829 2,607

2,810 2,660

2,850 2,794

2,836 2,849 2,818 2,530 2,856 2,723

2,823 2,514

2,819

2,526 2,843 2,854 2,773

2,832 2,801 2,756 2,851 2,608

2,811 2,613 2,845

2,858

2,831 2,543

2,665

2,848

2,821 2,622 2,815

2,855 2,871 2,866 2,779 2,753 2,850 2,823

2,916 2,669 2,827

2,839

2,890 2,817 2,793 2,764 2,421

2,850 2,707

2,778 2,804 2,579

2,602 2,816 2,7832,740 2,872 2,677 2,785

2,801 2,778 2,777 2,895 2,768

2,742 2,662 2,803 2,882

2,584 2,812 2,810 2,882 2,876 2,772 2,646

2,714 2,605 2,766

2,955

2,768

2,757 2,755 2,732

2,762

2,716 2,876 2,386 2,740

2,947

3,0323,009 2,466 2,960 2,818 2,750

2,729 2,504

2,467 2,406

2,647

2,743 2,601

2,804

2,837

2,594

2,834

2,843 2,822

2,816

2,750 2,817

2,791 2,727 2,745

2,727

2,790

2,930 2,754

2,902

2,918

A

A

A'

A' 2,815 2,725

2,865

2,811

2,660

2,600

2,589

2,792

2,671

!

!

! !

!

!

! !

!

EXPLANATION

2,400

Active model cells for Ogallala aquifer 

Trace of geologic section (fig. 6)

Aquifer potentiometric contour—Shows average 

altitude at which water level would have stood in 

tightly cased wells, water years 1979–98. Contour 

interval is 50 feet. Datum is NGVD of 1929

2,804

General direction of groundwater flow

Water well—Number is estimated 

average hydraulic head for water years 

1979–98, in feet above NGVD of 1929

Figure 4. Estimated average potentiometric surface of the Ogallala aquifer (from Long and others, 2003).
Conceptual Model 11

On the basis of previous estimates and model calibration, 

Long and others (2003) estimated hydraulic conductivity (K) 

values. For the Ogallala aquifer, horizontal K estimates ranged 

from 0.2 to 120 ft/d, and the vertical K estimate was 6.6x10-4

ft/d. For the Arikaree aquifer, horizontal K estimates ranged 

from 0.1 to 5.4 ft/d, and vertical K estimates ranged from 

8.6x10-6 to 7.2x10-1 ft/d.

Recharge

Recharge to the Ogallala aquifer occurs from infiltration 

of precipitation on the outcrop of the Ogallala Formation and 

the overlying windblown sand deposits in the southeastern 

part of the study area. Recharge to the Arikaree aquifer occurs 

from infiltration of precipitation on the outcrop of the Arikaree 

Formation.

Figure 5. Estimated average potentiometric surface of the Arikaree aquifer (from Long and others, 2003).

T.

102

N.

T.

101

N.

T.

100

N.

T.

98

N.

T.

97

N.

T.

96

N.

T.

95

N.

T.

99

N.

R. 33 W. R. 32 W. R. 31 W. R. 30 W. R. 29 W. R. 28 W. R. 27 W. R. 26 W. R. 25 W. R. 79 W.

MELLETTE COUNTY

BENNETT COUNTY

TODD COUNTY

TODD COUNTY

CHERRY COUNTY

JACKSON COUNTY

TRIPP COUNTY

NEBRASKA

SOUTH DAKOTA

White River

Wood

Okreek Carter

Parmelee

Mission Antelope

Rosebud

Blackpipe

St. Francis

Olsonville

Norris

83

83

18

18

Little

White

Keya Paha

River

River

South

Cr

Cr

Cr

Gray

Beads

Omaha

Rosebud

Phister

S. Ironwood Creek

Creek

Lone Tree

Creek

Creek

Soldier Creek

Eagletail

Sand Creek

Creek

Creek

Creek

Thunder

Creek

White

Rock

Spring

Black

Pipe

Creek

Antelope

Antelope

Eagle

Oak

Creek

Cut

Meat

Creek

Creek

North

Pine

Branch

Branch

Creek

Creek

Minnechaduza

Creek

Dry

Creek

101°15' 101° 100°45' 100°30' 100°15'

43°

43°15'

43°30'

Base from U.S. Geological Survey digital data 1:100,000, 1980, 1982, 1983, 1985

Universal Transverse Mercator projection, zone 14

0 5 10 MILES

0 5 10 KILOMETERS

2,550

2,600

2,600

2,650

2,650

2,700

2,700

2,750

2,750

2,800

2,800

2,800

2,500

2,850

2,900

2,950

3,050

3,000

2,450

3,050

2,400

2,500

2,500

2,550

2,600

2,550

2,850

2,850

2,400

2,500

2,500

2,800

3,000

2,900

2,450

2,450

2,450

2,843

2,931

2,488

2,668 2,851 2,565

2,783

2,831

2,611

2,569

2,824 2,558 2,673 2,593 2,812 2,783 2,558

2,719 2,513

2,646

2,660

2,842 2,550

2,614

2,673

2,546 2,628 2,525

2,712 2,645

2,860 2,534 2,447 2,820

2,722 2,734 2,856

2,674 2,736 2,498 2,642

2,428

2,597

2,614 2,631 2,395

2,521

2,667

2,511

2,603 2,734

2,781

2824 2,533 2,839 2,802 2,522

2,359 2,737

2,442 2,495 2,557

2,753 2,548 2,418 2,609 2,876 2,639 2,453 2,789

2,472

2,466

2,792 2,537

2,498 2,604 2,526 2,347

2,740

2,718 2,401 2,451 2,351 2,373

2,582 2,694 2,506 2,394

2,414 2,716

2,341

2,701 2,413 2,477 2,736 2,437 2,540 2,926 2,605 2,708 2,609

2,624 2,573 2,645 2,476 2,388 2,417 2,507

2,724

2,670 2,563 2,416

2,686 2,627 2,827 2,638 2,505 2,657 2,539

2,431 2,453 2,639 2,505 2,699 2,907 2,878 2650 2,670

2,688 2,782 2,610

2,732 2,416 2,632 2,587 2,529 2,486 2,553 2,468

2,931 2,716

2,841 2,606

2,474

2,492 2,656 2,497

2,502 2,489 2,457 2,681

2,536 2477 2,521

2,513

2,597 2,625

2,601 2,671 2,534 2,629 2,648 2,543 2,646 2,646 2,552 2,587 2,505

2,471

2,599

2,603 2,645 2,768

2,568 2,626 2,625 2,615 2,609

2,469 2,583 2,545 2,585

2,616

2,525

2,506

2,600

2,639 2,482 2510 2,517

2,585 2,479 2,449 2,469

2,686

2,686 2,600

2,586 2,543 2,570

2,523

2,516

2,781 2,523

2,458

2,764

2,578

2,561

2,832

2,586

!

!

!

!

!

!

!

!

! ! ! !

! !

!

!

! !

! ! ! ! ! ! ! !

! ! ! ! ! !

! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !

! ! ! ! ! ! ! ! ! ! ! !

! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !

! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !

! ! ! ! ! ! ! ! ! ! ! ! ! !

! ! ! !

! ! ! ! !

! ! !

! !

! ! ! !

! ! ! ! !

! ! ! ! ! ! ! !

! !

!

! 2,843

2,931

2,488

2,668 2,851 2,565

2,783

2,831

2,611

2,569

2,824 2,558 2,673 2,593 2,812 2,783 2,558

2,719 2,513

2,646

2,660

2,842 2,550

2,614

2,673

2,546 2,628 2,525

2,712 2,645

2,860 2,534 2,447 2,820

2,722 2,734 2,856

2,674 2,736 2,498 2,642

2,428

2,597

2,614 2,631 2,395

2,521

2,667

2,511

2,603 2,734

2,781

2824 2,533 2,839 2,802 2,522

2,359 2,737

2,442 2,495 2,557

2,753 2,548 2,418 2,609 2,876 2,639 2,453 2,789

2,472

2,466

2,792 2,537

2,498 2,604 2,526 2,347

2,740

2,718 2,401 2,451 2,351 2,373

2,582 2,694 2,506 2,394

2,414 2,716

2,341

2,701 2,413 2,477 2,736 2,437 2,540 2,926 2,605 2,708 2,609

2,624 2,573 2,645 2,476 2,388 2,417 2,507

2,724

2,670 2,563 2,416

2,686 2,627 2,827 2,638 2,505 2,657 2,539

2,431 2,453 2,639 2,505 2,699 2,907 2,878 2650 2,670

2,688 2,782 2,610

2,732 2,416 2,632 2,587 2,529 2,486 2,553 2,468

2,931 2,716

2,841 2,606

2,474

2,492 2,656 2,497

2,502 2,489 2,457 2,681

2,536 2477 2,521

2,513

2,597 2,625

2,601 2,671 2,534 2,629 2,648 2,543 2,646 2,646 2,552 2,587 2,505

2,471

2,599

2,603 2,645 2,768

2,568 2,626 2,625 2,615 2,609

2,469 2,583 2,545 2,585

2,616

2,525

2,506

2,600

2,639 2,482 2510 2,517

2,585 2,479 2,449 2,469

2,470 2,686

2,686 2,600

2,586 2,543 2,570

2,523

2,516

2,781 2,523

2,458

2,764

2,578

2,561

2,832

2,586

A

A

A'

A'

EXPLANATION

2,800

Active model cells for Arikaree aquifer 

Trace of geologic section (fig. 6)

Potentiometric contour—Shows average altitude 

at which water level would have stood in tightly 

cased wells, water years 1979–98. Contour 

interval is 50 feet. Datum is NGVD of 1929

! 2,804

General direction of groundwater flow

Water well—Number is estimated average 

hydraulic head for water years 1979–98, in 

feet above NGVD of 1929
Figure 6. Relation between hydraulic head, hydrogeologic units, and topographic features.

Ogallala aquifer

Arikaree aquifer

ElCk

Antelope Creek

Rock Creek

Little White River

White River Group

A 

2,000

2,2002,4002,600

ELEVATION, IN FEET ABOVE NATIONAL GEODETIC VERTICAL DATUM OF 1929 2,800 3,000

3,200

FEET

WEST 

VERTICAL SCALE IS GREATLY EXAGGERATED

Trace of section shown in figures 4 and 5

Tops of hydrogeologic units modi

EXPLANATION

0 1 2 3 4 MILES0 1 2 3 4 KILOMETERS

Average hydraulic head in Arikaree aquifer, water years 1979–98Average hydraulic head in Ogallala aquifer, water years 1979–98General direction of groundwater flow
Conceptual Model 13

Previous investigators have estimated recharge for the 

High Plains aquifer, which includes the Ogallala and Arikaree 

aquifers. These estimates include 15 percent of precipitation or 

2.5 to 3.0 inches per year (in/yr) for the study area (Langbein, 

1949), 2.6 in/yr in the upper Niobrara River Basin (Bradley, 

1956), 3.07 in/yr for the Sand Hills of Nebraska (Rahn and 

Paul, 1975), and 8 percent of precipitation or 1.3 to 1.8 in/yr 

for South Dakota (Kolm and Case, 1983). These estimates 

primarily pertain to precipitation recharge to the overlying 

Ogallala aquifer. The lower permeability of the Arikaree 

aquifer, particularly in the upper part, may prevent that aquifer 

from accepting as much precipitation recharge as the Ogallala 

aquifer. 

Recharge to the aquifers from infiltrating irrigation water, 

or irrigation return flow, was considered negligible because 

total irrigation for the study area was less than 5 percent of 

estimated recharge in the study area, and irrigation return flow 

was assumed to be a small fraction of total irrigation. Additional details on irrigation and recharge estimates are in the 

“Well Withdrawals” and “Model Calibration” sections.

Evapotranspiration

Evapotranspiration occurs when the water table is at or 

near the land surface and thus generally occurs in topographically low areas such as river valley bottoms. The water-table 

altitude influences the evapotranspiration rate. When the water 

table is at the land surface, evapotranspiration is larger than 

when the water table is below the land surface. Evapotranspiration is smallest when the water table is below the root zone. 

Generally, the depth of this root zone is assumed to be about 

5 to 10 ft in the study area with deeper root penetration associated with pine and deciduous forests, which are common as 

much as one-half mile (mi) from the Little White River and its 

tributaries between Spring Creek and Soldier Creek. Forests 

also are common near streams along the northern extent of 

the outcrop of the Arikaree Formation. Other parts of the 

study area generally are grasslands or agricultural. Land-cover 

information was obtained from the Multi-Resolution Land 

Characteristics Consortium (2009) to differentiate forests from 

grasslands and agricultural areas. To simplify the vegetation 

zones, small areas less than about 0.7 mi2 were removed and 

included in the surrounding vegetation zones (see “Numerical 

Model” section). 

Maximum evapotranspiration during summer stress 

periods was estimated as 70 percent of pan evaporation on the 

basis of the relation between pan evaporation and evapotranspiration described by Farnsworth and others (1982). Pan evaporation rates in the study area were assumed to be similar to 

those at a National Weather Service climatological data station 

at Cottonwood (National Climatic Data Center, 2010; station 

391972), which is located about 75 mi northwest of the study 

area. Pan evaporation records were available for the months 

of June through September for the 30 water years included in 

the analysis. The estimated maximum evapotranspiration for 

the 30 summer stress periods (table 2) ranged from 20.4 to 

30.7 inches (in.), with a median value of 26.5 in. On the basis 

of sparse pan evaporation data for spring and late fall, a value 

for all spring stress periods was estimated as 9 in., and a value 

for all fall/winter stress periods was estimated as 3 in. On the 

basis of these estimates and the assumption that maximum 

evapotranspiration was 70 percent of pan evaporation, the 

maximum evapotranspiration was calculated as 6.3 and 2.1 in., 

respectively, for the spring and fall/winter stress periods. 

Discharge to Streams and Springs

Springs and seeps discharge groundwater to streams in 

the study area. Long and others (2003) estimated the average 

groundwater discharge, or base flow, to the Little White and 

Keya Paha Rivers in the study area for water years 1979–98 

as 49 and 23 ft3/s, respectively. These estimates were made 

Table 2. Estimated maximum evapotranspiration rate 

during summer stress periods, water years 1979–2008.

Water 

year

Stress 

period

Pan evaporation 

(inches)

Estimated maximum 

June–September 

evapotranspiration 

(inches)

1979 3 35.4 24.8

1980 6 41.6 29.1

1981 9 35.5 24.9

1982 12 31.4 22.0

1983 15 40.4 28.3

1984 18 38.0 26.6

1985 21 39.7 27.8

1986 24 29.9 20.9

1987 27 39.5 27.6

1988 30 43.8 30.7

1989 33 42.1 29.5

1990 36 40.5 28.3

1991 39 37.8 26.5

1992 42 30.8 21.6

1993 45 29.2 20.4

1994 48 37.4 26.2

1995 51 36.2 25.3

1996 54 39.5 27.7

1997 57 32.1 22.5

1998 60 31.3 21.9

1999 63 32.0 22.4

2000 66 38.9 27.2

2001 69 35.4 24.7

2002 72 40.5 28.3

2003 75 40.5 28.3

2004 78 36.5 25.5

2005 81 38.9 27.3

2006 84 40.2 28.1

2007 87 40.6 28.4

2008 90 34.5 24.1
14 Simulated Groundwater Flow in the Ogallala and Arikaree Aquifers, Rosebud Indian Reservation Area

by applying hydrograph separation methods to continuous streamflow measurements. Additional manual streamflow measurements were used to verify these estimates and 

to estimate base flow for four other drainage basins—Cut 

Meat Creek, Black Pipe Creek, Minnechaduza Creek, and 

Sand Creek (table 3). Four sets of synoptic measurements of 

streamflow at low-flow conditions during late summer and fall 

were collected to assess base flow. Streamflow was measured 

by wading streams with vertical-axis bucket-wheel current 

meters as described by Rantz and others (1982). Streamflow 

was measured at 35 sites (fig. 7) twice during 1999 and twice 

during 2006, with the exception of a few sites that were not 

measured on all four dates because of limited access (table 3). 

These measurements were made during periods when direct 

runoff was not observed to occur and thus represent approximate base-flow conditions. 

Base flow for the Little White River in the study area is 

approximated by the subtraction of base flow at the furthest 

upstream site (site 1) from base flow at the furthest downstream site (site 12), and base flow for the Keya Paha River 

is approximated by base flow at site 33 (fig. 7, table 3). 

The average of these base-flow approximations for the four 

measurements was 54 and 18 ft3/s for the Little White and 

Keya Paha Rivers, respectively (table 3). These values are 

similar to estimates of 49 and 23 ft3/s made by using hydrograph separation techniques on continuous streamflow data 

T.

102

N.

T.

101

N.

T.

100

N.

T.

98

N.

T.

97

N.

T.

96

N.

T.

95

N.

T.

99

N.

R. 33 W. R. 32 W. R. 31 W. R. 30 W. R. 29 W. R. 28 W. R. 27 W. R. 26 W. R. 25 W. R. 79 W.

MELLETTE COUNTY

BENNETT COUNTY

TODD COUNTY

TODD COUNTY

CHERRY COUNTY

JACKSON COUNTY

TRIPP COUNTY

NEBRASKA

SOUTH DAKOTA

83

83

18

18

Little

White

Keya Paha

River

River

South

Cr

Cr

Cr

Gray

Beads

Omaha

Rosebud

Phister

S. Ironwood Creek

Creek

Lone Tree

Creek

Creek

Soldier Creek

Eagletail

Sand Creek

Creek

Creek

Creek

Thunder

Creek

White

Rock

Spring

Black

Pipe

Creek

Antelope

Antelope

Eagle

Oak

Creek

Cut

Meat

Creek

Creek

North

Pine

Branch

Branch

Creek

Creek

Minnechaduza

Creek

Dry

Creek

White River

Wood

Okreek Carter

Parmelee

Mission Antelope

Rosebud

Blackpipe

St. Francis

Olsonville

Norris

101°15' 101° 100°45' 100°30' 100°15'

43°

43°15'

43°30'

Base from U.S. Geological Survey digital data 1:100,000, 1980, 1982, 1983, 1985

Universal Transverse Mercator projection, zone 14

0 5 10 MILES

0 5 10 KILOMETERS

9

8

7

5 6

1 3

4

2

34

35

32

31

30

29

28

27

24

23

22

21

19

20

18

17

15

16

14

13

12

11

10

33

25

26

EXPLANATION

Measurement site—Number is map index number in table 3 10

Figure 7. Streamflow measurement sites for seepage runs during 1999 and 2006.
Table 3. Measured streamflow at selected sites during seepage runs during 1999 and 2006. Estimates of base flow for each drainage basin are s[Shading indicates data used in estimating drainage basin base flow; --, not measured; NA, not applicable]

Map 

label 

(fig. 7)

Site identficiation 

number Station name

Streamflow, in cubic feet per s

July 27–29, 

1999a

Aug. 30–

Sept. 1, 

1999a

Aug. 7–9, 

2006

Oct. 

16–17, 

2006

Little White River drainage basin

1 06449100 Little White River near Vetal, SD 72.0 44.9 20.4 33.4 2 430158101045400 Spring Creek near Cody, NE 2.1 -- -- -- 3 430610101044300 Spring Creek near Spring Creek, near St. Francis, SD 9.1 4.3 3.5 3.7 4 430611101044600 Little White River below Spring Creek, near St. Francis, SD 117 66.1 39.9 57.9 5 431146100574900 Omaha Creek near Rosebud, SD .9 .8 .6 1.0 6 431205100580200 Beads Creek near Rosebud, SD 1.5 1.0 .4 1.6 7 431208100580300 Little White River below Beads Creek 117 75.6 50.1 71.8 8 431343100571700 South Fork Ironwood Creek, near Rosebud, SD 1.8 1.6 1.3 1.8 9 06449300 Little White River above Rosebud, SD 119 84.9 57.0 81.4 10 06449400 Rosebud Creek at Rosebud, SD 8.0 7.8 4.6 8.0 11 431911100525200 Soldier Creek near Rosebud, SD 1.7 1.9 0 1.3 12 06449500 Little White River near Rosebud, SD 140 99.3 60.7 85.3 

Site 12 minus site 1 68.0 54.4 40.3 51.9 

Cut Meat Creek drainage basin

13 431830101033400 Phister Creek near Parmelee, SD .7 .6 .1 .4 14 431837101033200 Cut Meat Creek below Phister Creek, near Parmelee, SD 1.1 .7 .1 .5 15 432249100595500 Cut Meat Creek near Parmelee, SD 2.4 0 0 0 16 432405100591300 Gray Eagletail Creek near Parmelee, SD 2.1 2.3 0 0 

Black Pipe Creek drainage basin

17 432323101113300 Black Pipe Creek near Black Pipe, SD 3.9 2.8 .2 2.4 18 432743101100900 Black Pipe Creek near Norris, SD 3.6 -- 0 .7 

Minnechaduza Creek drainage basin

19 430021101075300 Minnechaduza Creek near Cody, NE .1 -- -- -- 20 430114100574900 Minnechaduza Creek near Kilgore, NE 2.7 -- .2 -- 

Keya Paha River drainage basin

21 06463900 Antelope Creek near Mission, SD 2.0 3.2 0 2.0 22 431700100412500 Antelope Creek tributary above Mission, SD .5 .6 0 .2 23 431648100331800 Antelope Creek below Antelope Lake near Mission, SD 4.3 1.3 .1 .2 
Table 3. Measured streamflow at selected sites during seepage runs during 1999 and 2006. Estimates of base flow for each drainage basin are s[Shading indicates data used in estimating drainage basin base flow; --, not measured; NA, not applicable] Map label (fig. 7) Site identficiation number Station name Streamflow, in cubic feet per sec

July 27–29, 1999a Aug. 30– Sept. 1, 1999a Aug. 7–9, 2006 Oct. 16–17, 2006 

Keya Paha River drainage basin—Continued 24 431506100281600 Antelope Creek above Keya Paha River near Mission, SD 6.1 1.7 .2 .6 

25 430940100294800 Lone Tree Creek near Olsonville, SD .7 .6 .4 .4 26 430940100294600 Rock Creek below Lone Tree Creek, near Olsonville, SD 5.2 4.4 2.9 3.3 27 431258100240000 Rock Creek near Mission, SD 9.4 8.6 4.1 5.9 28 431257100220000 Keya Paha River below Rock Creek near Mission, SD 19.3 14.1 4.7 8.6 29 431132100184700 Keya Paha River above Eagle Creek near Mission, SD 19.8 15.4 5.2 8.2 30 430645100185200 Eagle Creek near Olsonville, SD .2 .4 0 -- 31 430930100171500 Eagle Creek near Keyapaha, SD 1.6 2.2 1.0 1.3 32 431008100140300 Keya Paha River below Eagle Creek, SD 22.0 15.6 7.0 9.4 33 06464100 Keya Paha River near Keyapaha, SD 26.5 22.4 9.6 11.5 

Sand Creek drainage basin 34 425959100174900 Sand Creek near Valentine, NE -- -- -- -- 

35 430254100111000 Sand Creek near Keya Paha, SD 4.4 4.5 2.6 4.0 

aFrom Long and others (2003). bEstimated for drainage area within the study area only.
Conceptual Model 17

by Long and others (2003), which indicates that the additional 

manual measurements could be used to approximate base 

flow for the four smaller drainage basins in the study area. 

Therefore, the average streamflow measurements for sites 15, 

16, 18, 20, and 35 were used to estimate base flow for the Cut 

Meat, Black Pipe, Minnechaduza, and Sand Creek drainage basins (fig. 7, table 3). The Black Pipe Creek drainage 

basin is partly outside of the study area, and the base-flow 

estimate was reduced accordingly from 1.4 to 1.2 ft3/s based 

on the proportion of the area outside of the study area. Site 

20 on Minnechaduza Creek is about midway between the 

stream’s headwaters and the model boundary, and to account 

for unmeasured flow downstream from site 20, the average 

flow of 1.5 ft3/s at site 20 was doubled (3.0 ft3/s) and used as 

the base-flow estimate for the drainage basin. The base-flow 

estimate of 1.7 ft3/s for the Cut Meat drainage basin is the 

sum of the average flows for sites 15 and 16. The base-flow 

estimate of 3.9 ft3/s for the Sand Creek drainage basin is the 

average flow at site 35. The four smaller drainage basins were 

estimated to have a total average base flow of 9.8 ft3/s. These 

estimates are inclusive of spring flow along streambanks. For 

the Little White and Keya Paha Rivers, the original base-flow 

estimates of 49 and 23 ft3/s from Long and others (2003) based 

on continuous streamflow data were used (table 3). Estimated 

base flow for these two rivers is about 88 percent of the total 

estimated base flow.

Springs are located along the northern contact of the 

Arikaree Formation with the underlying White River Group 

and discharge from the Arikaree aquifer into streams flowing 

to the north. Spring discharge probably takes place near this 

contact because of the very low permeability of the White 

River Group, which causes northerly flowing groundwater to 

emerge as springflow. 

Well Withdrawals

Well withdrawals in the study area occur primarily for 

irrigation but also for public supply, domestic use, and stock 

use. Irrigation withdrawals from the Ogallala aquifer are 

especially important in Todd County and mainly occur east 

of St. Francis (fig. 8), where the saturated thickness of the 

Ogallala aquifer is greatest. The acres of irrigated land in Todd 

County from 1985 to 2005 ranged from 10,000 to 11,000 acres 

(U.S. Geological Survey, 2009). Irrigation withdrawals are 

variable because they are affected by numerous factors, such 

as climatic conditions, commodity prices, and energy costs. 

Most of the wells used for irrigation in the study area were 

constructed in the 1970s.

Water-use data for irrigation and public supply are 

compiled every 5 years as part of the USGS National 

Water-Use Information Program in cooperation with local, 

State, and Federal agencies and is aggregated by counties for 

each State (U.S. Geological Survey, 2009). Data on groundwater withdrawals from the Ogallala and Arikaree aquifers in 

the study area were compiled from the USGS Site-Specific 

Water-Use Data System (SWUDS) for the period of available 

record (1981–2005). The SWUDS database includes water use 

reported by operators under specific water-use permits. The 

reported use for a permit can include more than one well or 

center-pivot irrigation system (table 4). 

Groundwater withdrawals for 1979 and 1980 were 

estimated as the average withdrawals for the period 1981–85 

and proportioned to each well according to the estimated 

withdrawals for 1981. Groundwater withdrawals for 2006–08 

were estimated as being equal to withdrawals for 2005. The 

Table 4. Estimated groundwater withdrawals for irrigation and 

public supply in the study area, 1979–2008.

Year

Acre-feet Cubic feet per seconda

Total Ogallala 

aquifer

Arikaree 

aquifer Total

1979 6,796 28.1 0 28.1

1980 6,796 28.1 0 28.1

1981 6,852 28.3 0 28.3

1982 7,054 29.2 0 29.2

1983 5,504 22.7 0 22.7

1984 7,751 32.0 0.05 32.0

1985 6,818 28.2 0 28.2

1986 7,481 30.7 .23 30.9

1987 5,437 22.2 .23 22.5

1988 7,054 29.2 0 29.2

1989 14,524 59.5 .56 60.0

1990 10,020 41.1 .28 41.4

1991 6,234 25.8 0 25.8

1992 5,178 21.4 0 21.4

1993 5,886 24.0 .28 24.3

1994 8,256 33.8 .28 34.1

1995 7,088 29.2 .09 29.3

1996 11,862 49.0 .00 49.0

1997 10,053 41.4 .14 41.5

1998 6,459 26.5 .19 26.7

1999 6,470 26.6 .19 26.7

2000 7,593 31.1 .28 31.4

2001 9,267 38.2 .14 38.3

2002 13,255 54.4 .37 54.8

2003 12,761 52.5 .23 52.7

2004 12,783 52.5 .37 52.8

2005 10,772 44.2 .28 44.5

2006 10,772 44.2 .28 44.5

2007 10,772 44.2 .28 44.5

2008 10,772 44.2 .28 44.5

Average 8,611 35.4 .17 35.6

a

Withdrawal rate based on a 4-month season (June-September).
18 Simulated Groundwater Flow in the Ogallala and Arikaree Aquifers, Rosebud Indian Reservation Area

estimated groundwater withdrawal for the study area by 

year ranged from about 5,200 to 14,500 acre-ft and averaged 

8,611 acre-ft (table 4), or 35.6 ft3/s over a 4-month period. The 

largest estimated irrigation use during the analysis period was 

in 1989 when precipitation was about 4 in. below normal. 

Numerical Model

The numerical flow model of the Ogallala and Arikaree aquifers described in this report is a revision of that 

described by Long and others (2003), which was an analysis that included water years 1979–98. The revised model 

includes water years 1979–2008 for transient simulation and 

was discretized into 90 seasonal stress periods, or three stress 

periods per year. Future scenarios of potential drought and 

increased pumping were simulated for a 20-year period with 

the calibrated model. Other revisions are listed in table 5 and 

described in more detail in subsequent sections.

Model Design

MODFLOW-2000 (Harbaugh and others, 2000), which 

is a numerical, three-dimensional, finite-difference groundwater model, was used to simulate flow in the aquifers. Details 

of the MODFLOW-2000 packages that were included in the 

model were described by McDonald and Harbaugh (1988) 

and Harbaugh and others (2000). These packages included 

Layer-Property Flow, River, Recharge, Well, Drain, and 

Evapotranspiration. Average rates of recharge, maximum 

evapotranspiration, and well withdrawals were included in the 

steady-state simulation, and time-varying rates were included 

in the transient simulation. Model parameters estimated by 

calibration were horizontal and vertical hydraulic conductivity (K), recharge and evapotranspiration rates, and the vertical 

hydraulic conductances of riverbeds and springs. 

Grid and Boundary Conditions

The model had two layers: the upper layer represented 

the Ogallala aquifer and surficial Quaternary-age deposits, and 

the lower layer represented the Arikaree aquifer. The model’s 

grid had 168 rows oriented east-west and 202 columns 

oriented north-south. Most of the rows and columns were 

1,640 ft (500 meters (m)) wide, except that smaller rows and 

columns were used in areas where large water-supply wells are 

located because of potentially steep hydraulic gradient in these 

areas. These rows and columns were 984 ft (300 m) wide 

(fig. 9). The height of each cell is equal to the estimated 

formation thickness, which was determined on the basis of 

structure-contour maps of the Arikaree Formation and White 

River Group (Carter, 1998) and land-surface elevation data 

at a 30-m grid resolution (National Elevation Dataset, 2006). 

These elevation data were used to represent the top of layer 

1, where the Ogallala Formation and overlying windblown 

deposits are exposed to the land surface, and the top of layer 2, 

where the Arikaree Formation is exposed. The altitude of the 

top of the Arikaree Formation, where buried, represented the 

bottom of layer 1 and top of layer 2. The altitude of the top of 

the White River Group represented the bottom of layer 2. 

Both layers were simulated so that cells were convertible 

between confined and unconfined conditions. Although the top 

of layer 1 is the land surface, there is no option in MODFLOW 

to simulate a layer as strictly unconfined. If hydraulic head in a 

convertible cell exceeds the top of layer 1, the cell will convert 

to confined (McDonald and Harbaugh, 1988). This occurs 

where discharge to simulated streams and spring occurs, which 

prevents pressure from building in these cells and allows 

outflow to occur. Cells of constant hydraulic head were used 

on the western model boundary and the western part of the 

southern boundary for both layers and also in the southeastern corner for layer 1 (figs. 9 and 10). Other boundaries were 

designated as no-flow boundaries, which included the edges 

of the aquifers or where study area boundaries were approximately parallel to the estimated groundwater-flow direction. 

Table 5. Revisions to the model described by Long and others (2003).

Category 2003 modela Revision in 2010 model

Simulated period, in water years 1979–1998 1979–2008.

Calibration method Trial-and-error Inverse modeling.

Base-flow calibration Two drainage basins Six drainage basins.

Recharge estimate Percentage of precipitation as a 

constant

Percentage of recharge is variable.

Delineation of vegetation types Topographic maps Satellite imagery.

Model cell discretization Uniform cell size (1,640 feet 

each side)

Variable cell size with smallest cells 

near municipal production wells 

(984 to 1,640 feet each side).

a

Long and others (2003).
Numerical Model 19

Hydraulic Conductivity

Zones of constant K were delineated by considering 

potential structural features, and specific capacities of wells 

(figs. 11–13). Five major zones for horizontal and vertical K

were separated along stream reaches because of the possibility 

of structural control of streams. Subareas within these zones 

in the Ogallala aquifer partly were delineated in accordance 

with spatial variations of specific capacity of wells (fig. 11), 

especially high specific capacities in the central part of the 

model area between the Little White and Keya Paha Rivers 

(Long and others, 2003). Subareas were further delineated 

as needed for model calibration purposes as described in the 

“Model Calibration” section. Parameter estimation for these 

zones by inverse modeling resulted in horizontal K values 

ranging from about 0.2 to 84.4 ft/d for the Ogallala aquifer 

and about 0.1 to 4.3 ft/d for the Arikaree aquifer (figs. 11 and 

12). Zones of large horizontal K were assigned along the Little 

White and Keya Paha Rivers in layer 2 (fig. 12) to allow for a 

substantial groundwater discharge that occurs to these streams. 

Higher horizontal K may be the result of near-surface weathering, which probably extends below the water table in these 

topographically low areas. In addition, if the locations of these 

streams are affected by fractures or faults, higher K values 

could result. The process of delineating hydraulic conductivity 

zones is further described in the “Model Calibration” section.

Figure 8. Recharge areas and locations of water-supply wells.

Water-supply well in Ogallala aquifer

Water-supply well in Arikaree aquifer

Ogallala aquifer recharge area 

Arikaree aquifer recharge area

EXPLANATION

Qa

To

Tw

T.

102

N.

T.

101

N.

T.

100

N.

T.

98

N.

T.

97

N.

T.

96

N.

T.

95

N.

T.

99

N.

R. 33 W. R. 32 W. R. 31 W. R. 30 W. R. 29 W. R. 28 W. R. 27 W. R. 26 W. R. 25 W. R. 79 W.

MELLETTE COUNTY

BENNETT COUNTY

TODD COUNTY

TODD COUNTY

CHERRY COUNTY

JACKSON COUNTY

TRIPP COUNTY

NEBRASKA

SOUTH DAKOTA

83

83

18

18

Little

White

Keya Paha

River

River

South

Cr

Cr

Cr

Gray

Beads

Omaha

Rosebud

Phister

S. Ironwood Creek

Creek

Lone Tree

Creek

Creek

Soldier Creek

Eagletail

Sand Creek

Creek

Creek

Creek

Thunder

Creek

White

Rock

Spring

Black

Pipe

Creek

Antelope

Eagle

Oak

Creek

Cut

Meat

Creek

Creek

North

Pine

Branch

Branch

Creek

Creek

Minnechaduza

Dry

Creek

White River

Wood

Okreek Carter

Parmelee

Mission Antelope

Rosebud

Blackpipe

St. Francis

Olsonville

Norris

101°15' 101° 100°45' 100°30' 100°15'

43°

43°15'

43°30'

Base from U.S. Geological Survey digital data 1:100,000, 1980, 1982, 1983, 1985

Universal Transverse Mercator projection, zone 14

0 5 10 MILES

0 5 10 KILOMETERS
20 Simulated Groundwater Flow in the Ogallala and Arikaree Aquifers, Rosebud Indian Reservation Area

MODFLOW-2000 calculates vertical K between adjacent layers as the harmonic mean of vertical K for the two 

layers. The Arikaree aquifer was delineated into five vertical 

K zones, but because of the harmonic mean calculation, it was 

not necessary to delineate the Ogallala aquifer into zones to 

produce unique vertical K values between the two layers. A 

constant value of 4.2x10-4 ft/d was estimated for the Ogallala 

aquifer and ranged from 8.8x10-5 to 3.7 ft/d for the Arikaree 

aquifer (fig. 13). 

Recharge

Recharge accounted for by the Recharge Package in 

MODFLOW-2000 (McDonald and Harbaugh, 1988) is the 

amount of infiltrating precipitation that surpasses the root 

zone and reaches the water table. Recharge rates for the 

steady-state simulation were estimated from model calibration 

(see “Model Calibration” section) and were consistent with 

previously published values. Recharge was 2.91 in/yr for the 

Ogallala aquifer (about 15 percent of average precipitation for 

EXPLANATION

Qa

Tw

T.

102

N.

T.

101

N.

T.

100

N.

T.

98

N.

T.

97

N.

T.

96

N.

T.

95

N.

T.

99

N.

R. 33 W. R. 32 W. R. 31 W. R. 30 W. R. 29 W. R. 28 W. R. 27 W. R. 26 W. R. 25 W. R. 79 W.

MELLETTE COUNTY

BENNETT COUNTY

TODD COUNTY

TODD COUNTY

CHERRY COUNTY

JACKSON COUNTY

TRIPP COUNTY

83

83

18

18

Little

White

Keya Paha

River

River

South

Cr

Cr

Cr

Gray

Beads

Omaha

Rosebud

Phister

S. Ironwood Creek

Creek

Lone Tree

Creek

Creek

Soldier Creek

Eagletail

Sand Creek

Creek

Creek

Creek

Thunder

Creek

White

Rock

Spring

Black

Pipe

Creek

Antelope

Eagle

Oak

Creek

Cut

Meat

Creek

Creek

North

Pine

Branch

Branch

Creek

Creek

Minnechaduza

Dry

Creek

White River

Wood

Okreek Carter

Parmelee

Mission Antelope

Rosebud

Blackpipe

St. Francis

Olsonville

Norris

101°15' 101° 100°45' 100°30' 100°15'

43°

43°15'

43°30'

Base from U.S. Geological Survey digital data 1:100,000, 1980, 1982, 1983, 1985

Universal Transverse Mercator projection, zone 14

0 5 10 MILES

0 5 10 KILOMETERS

Tribal observation well completed in Ogallala 

aquifer. Label is well identifier (table 7)

State observation well completed in Ogallala 

aquifer. Label is well identifier (table 8)

Active cells

Inactive cells

Constant-head cells

RST-6

RST-7

RST-3 RST-8

RST-5

RST-9

RST-4

RST-27 TD-76A

RST-17 BT-76C

TD-76B TD-76H

TD-76G TD-76I TD-76D

BT-80E

RST-16

RST-13 TD-76C RST-23

RST-12 RST-18 TD-76J

TD-76F TD-79B TD-76E

RST-11

TD-80B RST-22

TD-80E

RST-19

RST-10

RST-10

TD-59A

TD-59A

RST-20 RST-21

TD-59B

Columns 

984 feet 

wide

Columns 984 

feet wide

Rows 984 

feet wide

Rows 984 

feet wide

Rows and 

columns 984 

feet wide

Row and columns 

are 1,640 feet wide 

except where 

otherwise specified

Figure 9. Cell types in the Ogallala aquifer (layer 1), observation wells completed in the Ogallala aquifer, and row and 

column widths for the Ogallala and Arikaree aquifers.
Numerical Model 21

1978–2008) and 1.45 in/yr for the Arikaree aquifer (about 

7.5 percent of average precipitation for 1978–2008), for a total 

rate of 255.4 ft3/s. Although recharge probably is spatially 

variable, a uniform distribution was assumed for each of the 

two recharge areas (fig. 8) because of insufficient data. A 

lower rate of recharge for the Arikaree aquifer than the Ogallala aquifer is consistent with the lower permeability of the 

Arikaree aquifer. Precipitation records were available for a 

National Weather Service Climatological Data station in the 

town of Mission (National Climatic Data Center, 2010; station 

395620), which is located near the center of the study area.

For the transient simulation, the antecedent rainfall 

conditions were considered in estimating recharge. During a 

rainstorm, the preexisting soil moisture content heavily influences the effectiveness of precipitation in recharging groundwater. The amount of rain that has fallen prior to a rainfall 

event—the antecedent rainfall condition—largely determines 

soil moisture content. Heavy rains prior to an event can 

saturate the root zone and decrease evapotranspiration rates in 

the unsaturated zone. The amount of precipitation that is not 

removed by evapotranspiration commonly is referred to as 

effective precipitation in rainfall-runoff modeling. Neglecting 

Figure 10. Cell types in the Arikaree aquifer (layer 2) and observation wells completed in the Arikaree aquifer.

EXPLANATION

Qa

Tw

T.

102

N.

T.

101

N.

T.

100

N.

T.

98

N.

T.

97

N.

T.

96

N.

T.

95

N.

T.

99

N.

R. 33 W. R. 32 W. R. 31 W. R. 30 W. R. 29 W. R. 28 W. R. 27 W. R. 26 W. R. 25 W. R. 79 W.

MELLETTE COUNTY

BENNETT COUNTY

TODD COUNTY

TODD COUNTY

CHERRY COUNTY

JACKSON COUNTY

TRIPP COUNTY

83

83

18

18

Little

White

Keya Paha

River

River

South

Cr

Cr

Cr

Gray

Beads

Omaha

Rosebud

Phister

S. Ironwood Creek

Creek

Lone Tree

Creek

Creek

Soldier Creek

Eagletail

Sand Creek

Creek

Creek

Creek

Thunder

Creek

White

Rock

Spring

Black

Pipe

Creek

Antelope

Eagle

Oak

Creek

Cut

Meat

Creek

Creek

North

Pine

Branch

Branch

Creek

Creek

Minnechaduza

Dry

Creek

White River

Wood

Okreek Carter

Parmelee

Mission Antelope

Rosebud

Blackpipe

St. Francis

Olsonville

Norris

101°15' 101° 100°45' 100°30' 100°15'

43°

43°15'

43°30'

Base from U.S. Geological Survey digital data 1:100,000, 1980, 1982, 1983, 1985

Universal Transverse Mercator projection, zone 14

0 5 10 MILES

0 5 10 KILOMETERS

Tribal observation well completed in Arikaree 

aquifer. Label is well identifier (table 7)

State observation well completed in Arikaree 

aquifer. Label is well identifier (table 8)

Active cells

Inactive cells

Constant-head cells

NEBRASKA

SOUTH DAKOTA

MT-78A

TD-80A

TD-79D

TD-80D RST-15

RST-15

TD-79A

TD-80C

TD-80C
22 Simulated Groundwater Flow in the Ogallala and Arikaree Aquifers, Rosebud Indian Reservation Area

direct runoff, effective precipitation is synonymous with 

groundwater recharge. Direct runoff was assumed negligible 

on the outcrop of the Ogallala Formation and overlying 

surficial deposits because of the high permeability of these 

sandy media. Because of the low permeability of the Arikaree 

aquifer, some direct runoff was assumed to occur. The method 

of Jakeman and Hornberger (1993) can be used to calculate an 

antecedent rainfall index si, which weights the daily rainfall by 

previous rainfall. The weighting si is distributed exponentially 

backward in time by

 si = cri+( 1-a-1)si-1 (1) 

 = c[ri+(1-a-1)si-1+(1-a-1)2si-2+...] i = 0, 1, ....N, 0 >si > 1, 

where c is a normalizing parameter to limit si to values 

between 0 and 1 [1/inches], a adjusts the influence of 

antecedent conditions [dimensionless], ri is total daily rainfall 

[inches], and i is the time step in days. Effective daily precipitation, or recharge, ui

 [inches] is then calculated by

 ui = risi (2)

A value of a = 24 was estimated by inverse modeling for a 

rainfall-runoff simulation in western South Dakota (Long, 

2009) and was used to estimate recharge for the Ogallala 

aquifer. Values of ri were from the Weather Service Climatological Data station at Mission (National Climatic Data Center, 

2010; station 395620). A value of c = 0.059 for the Ogallala 

aquifer was used because this resulted in an average recharge 

rate equal to 15 percent of precipitation for the 30-year period, 

which was consistent with the recharge rate estimated by 

the steady-state calibration. Recharge rates for the Ogallala 

Figure 11. Estimated horizontal hydraulic conductivity of the Ogallala aquifer, in feet per day. Hydraulic conductivity 

of subareas within five major parameter zones are shown in each shaded area.

NEBRASKA

SOUTH DAKOTA

Qa

Tw

T.

102

N.

T.

101

N.

T.

100

N.

T.

98

N.

T.

97

N.

T.

96

N.

T.

95

N.

T.

99

N.

R. 33 W. R. 32 W. R. 31 W. R. 30 W. R. 29 W. R. 28 W. R. 27 W. R. 26 W. R. 25 W. R. 79 W.

MELLETTE COUNTY

BENNETT COUNTY

TODD COUNTY

TODD COUNTY

CHERRY COUNTY

JACKSON COUNTY

TRIPP COUNTY

83

83

18

18

Little

White

Keya Paha

River

River

South

Cr

Cr

Cr

Gray

Beads

Omaha

Rosebud

Phister

S. Ironwood Creek

Creek

Lone Tree

Creek

Creek

Soldier Creek

Eagletail

Sand Creek

Creek

Creek

Creek

Thunder

Creek

White

Rock

Spring

Black

Pipe

Creek

Antelope

Eagle

Oak

Creek

Cut

Meat

Creek

Creek

North

Pine

Branch

Branch

Creek

Creek

Minnechaduza

Dry

Creek

White River

Wood

Okreek Carter

Parmelee

Mission Antelope

Rosebud

Blackpipe

St. Francis

Olsonville

Norris

101°15' 101° 100°45' 100°30' 100°15'

43°

43°15'

43°30'

Base from U.S. Geological Survey digital data 1:100,000, 1980, 1982, 1983, 1985

Universal Transverse Mercator projection, zone 14

0 5 10 MILES

0 5 10 KILOMETERS

13.3

Zone 5

28.1

Zone 3 2.5

Zone 4

0.4

Zone 3

84.4

Zone 3

26.8

Zone 1

5.4

Zone 1

0.2

Zone 2

1.3

Zone 1

25.1

Zone 2

2.8

Zone 3

8.4

Zone 2
Numerical Model 23

aquifer in total inches for each stress period were calculated as 

the sum of the effective daily precipitation (ui) for each stress 

period (table 6). As averages of daily values, recharge rates for 

each stress period ranged from 1.9 to 33.7 percent of precipitation for the Ogallala aquifer. Recharge by stress period for the 

Arikaree aquifer was estimated as one-half that of the Ogallala 

aquifer to be consistent with the steady-state simulation and to 

account for direct runoff.

Discharge

Various MODFLOW-2000 packages were used to simulate the discharge components of evapotranspiration, discharge 

to streams, and well withdrawals. The Evapotranspiration 

Package (McDonald and Harbaugh, 1988) was designed to 

simulate evapotranspiration from the uppermost aquifer in any 

given cell where the water table is within a specified depth 

below the land surface, referred to as the extinction depth. 

This extinction depth was set to 10 ft in areas with woody 

vegetation (U.S. Geological Survey, 1955) and to 7 ft elsewhere 

(fig. 14). The evapotranspiration rate is zero at the extinction depth and increases linearly to a maximum rate when the 

water level is at or above the land surface. The land-surface 

altitude for each cell was set to the average land-surface altitude for the area covered by the cell based on a 30-m digital 

elevation model.

The Evapotranspiration Package accounts for only part 

of total evapotranspiration because it affects groundwater at 

or below the water table only. Evapotranspiration of infiltrating or suspended groundwater in the unsaturated zone is not 

Figure 12. Estimated horizontal hydraulic conductivity of the Arikaree aquifer, in feet per day. Hydraulic conductivity 

of subareas within five major parameter zones are shown in each shaded area.

1.2

Zone 3

3.8

Zone 1

1.1

Zone 5

0.1

Zone 4

2.2 

Zone 2

0.1

Zone 3

2.4

Zone 3

4.3

Zone 2

Qa

Tw

T.

102

N.

T.

101

N.

T.

100

N.

T.

98

N.

T.

97

N.

T.

96

N.

T.

95

N.

T.

99

N.

R. 33 W. R. 32 W. R. 31 W. R. 30 W. R. 29 W. R. 28 W. R. 27 W. R. 26 W. R. 25 W. R. 79 W.

MELLETTE COUNTY

BENNETT COUNTY

TODD COUNTY

TODD COUNTY

CHERRY COUNTY

JACKSON COUNTY

TRIPP COUNTY

83

83

18

18

Little

White

Keya Paha

River

River

South

Cr

Cr

Cr

Gray

Beads

Omaha

Rosebud

Phister

S. Ironwood Creek

Creek

Lone Tree

Creek

Creek

Soldier Creek

Eagletail

Sand Creek

Creek

Creek

Creek

Thunder

Creek

White

Rock

Spring

Black

Pipe

Creek

Antelope

Eagle

Oak

Creek

Cut

Meat

Creek

Creek

North

Pine

Branch

Branch

Creek

Creek

Minnechaduza

Dry

Creek

White River

Wood

Okreek Carter

Parmelee

Mission Antelope

Rosebud

Blackpipe

St. Francis

Olsonville

Norris

101°15' 101° 100°45' 100°30' 100°15'

43°

43°15'

43°30'

Base from U.S. Geological Survey digital data 1:100,000, 1980, 1982, 1983, 1985

Universal Transverse Mercator projection, zone 14

0 5 10 MILES

0 5 10 KILOMETERS

NEBRASKA

SOUTH DAKOTA
24 Simulated Groundwater Flow in the Ogallala and Arikaree Aquifers, Rosebud Indian Reservation Area

Table 6. Estimated recharge to the Ogallala aquifer, water years 1979–2008.

Stress 

period Water year Months Precipitation (inches)

Recharge to Ogallala 

aquifer (inches)

Recharge as a percentage of precipitationa

1 1979 Oct.–Feb. 1.48 0.03 1.9

2 1979 Mar.–May 4.67 .36 7.6

3 1979 June–Sept. 11.50 2.33 20.3

4 1980 Oct.–Feb. 3.20 .25 7.9

5 1980 Mar.–May 3.34 .19 5.6

6 1980 June–Sept. 7.16 .86 12.0

7 1981 Oct.–Feb. 3.17 .21 6.6

8 1981 Mar.–May 5.92 .66 11.1

9 1981 June–Sept. 10.05 1.78 17.7

10 1982 Oct.–Feb. 4.67 .45 9.7

11 1982 Mar.–May 9.84 1.85 18.8

12 1982 June–Sept. 13.46 3.45 25.7

13 1983 Oct.–Feb. 5.35 .78 14.6

14 1983 Mar.–May 8.47 1.28 15.1

15 1983 June–Sept. 9.70 1.53 15.8

16 1984 Oct.–Feb. 3.80 .25 6.7

17 1984 Mar.–May 6.67 .65 9.8

18 1984 June–Sept. 7.65 1.00 13.1

19 1985 Oct.–Feb. 2.76 .14 5.2

20 1985 Mar.–May 3.11 .17 5.5

21 1985 June–Sept. 7.67 .82 10.6

22 1986 Oct.–Feb. 4.04 .28 7.0

23 1986 Mar.–May 8.34 1.06 12.7

24 1986 June–Sept. 12.83 2.07 16.1

25 1987 Oct.–Feb. 3.72 .33 8.8

26 1987 Mar.–May 8.40 1.12 13.4

27 1987 June–Sept. 6.63 .96 14.5

28 1988 Oct.–Feb. 3.06 .13 4.3

29 1988 Mar.–May 6.57 .82 12.5

30 1988 June–Sept. 7.85 1.23 15.7

31 1989 Oct.–Feb. 1.23 .03 2.4

32 1989 Mar.–May 2.96 .13 4.3

33 1989 June–Sept. 9.75 1.46 14.9

34 1990 Oct.–Feb. 2.55 .19 7.4

35 1990 Mar.–May 6.70 .67 10.1

36 1990 June–Sept. 10.69 2.44 22.8

37 1991 Oct.–Feb. 2.37 .10 4.1

38 1991 Mar.–May 10.70 2.22 20.8

39 1991 June–Sept. 8.16 2.75 33.7

40 1992 Oct.–Feb. 4.16 .23 5.6

41 1992 Mar.–May 1.99 .09 4.6

42 1992 June–Sept. 13.20 2.51 19.0

43 1993 Oct.–Feb. 2.37 .09 3.7

44 1993 Mar.–May 5.40 .57 10.6

45 1993 June–Sept. 9.77 1.31 13.4

46 1994 Oct.–Feb. 4.01 .25 6.2
Numerical Model 25

Table 6. Estimated recharge to the Ogallala aquifer, water years 1979–2008.—Continued

Stress 

period Water year Months Precipitation (inches)

Recharge to Ogallala 

aquifer (inches)

Recharge as a percentage of precipitationa

47 1994 Mar.–May 3.75 0.36 9.7

48 1994 June–Sept. 12.45 2.14 17.2

49 1995 Oct.–Feb. 2.98 .18 6.2

50 1995 Mar.–May 10.35 1.69 16.3

51 1995 June–Sept. 8.07 1.52 18.9

52 1996 Oct.–Feb. 6.33 1.05 16.7

53 1996 Mar.–May 7.03 .91 13.0

54 1996 June–Sept. 7.68 1.04 13.6

55 1997 Oct.–Feb. 4.58 .42 9.3

56 1997 Mar.–May 6.47 .77 12.0

57 1997 June–Sept. 11.07 2.00 18.1

58 1998 Oct.–Feb. 3.11 .22 7.0

59 1998 Mar.–May 5.66 .50 8.8

60 1998 June–Sept. 13.78 3.05 22.1

61 1999 Oct.–Feb. 6.87 .94 13.7

62 1999 Mar.–May 8.87 1.48 16.7

63 1999 June–Sept. 14.15 2.91 20.6

64 2000 Oct.–Feb. 2.10 .09 4.5

65 2000 Mar.–May 9.61 1.98 20.6

66 2000 June–Sept. 8.90 1.97 22.1

67 2001 Oct.–Feb. 6.21 .52 8.3

68 2001 Mar.–May 8.32 1.20 14.5

69 2001 June–Sept. 9.38 1.53 16.3

70 2002 Oct.–Feb. 3.98 .42 10.4

71 2002 Mar.–May 4.36 .35 8.0

72 2002 June–Sept. 5.11 .51 9.9

73 2003 Oct.–Feb. 2.65 .13 4.9

74 2003 Mar.–May 5.30 .49 9.3

75 2003 June–Sept. 6.00 .71 11.9

76 2004 Oct.–Feb. 2.13 .08 4.0

77 2004 Mar.–May 7.29 .79 10.8

78 2004 June–Sept. 10.27 1.59 15.5

79 2005 Oct.–Feb. 4.99 1.06 21.2

80 2005 Mar.–May 10.23 1.93 18.9

81 2005 June–Sept. 10.56 2.18 20.7

82 2006 Oct.–Feb. 2.49 .11 4.3

83 2006 Mar.–May 5.59 .61 10.8

84 2006 June–Sept. 10.35 1.36 13.2

85 2007 Oct.–Feb. 2.72 .14 5.2

86 2007 Mar.–May 7.76 .94 12.1

87 2007 June–Sept. 8.15 1.24 15.2

88 2008 Oct.–Feb. 5.58 .79 14.1

89 2008 Mar.–May 6.32 .66 10.5

90 2008 June–Sept. 13.62 3.21 23.6

a

Average of daily values for each stress period.
26 Simulated Groundwater Flow in the Ogallala and Arikaree Aquifers, Rosebud Indian Reservation Area

accounted for. Estimation of the recharge rate as some percentage of total precipitation, as previously described, accounts for 

this remaining part of the evapotranspiration process. 

Discharge to streams, which includes springs and seeps, 

was represented using two packages. The River Package in 

MODFLOW-2000 was used to simulate the hydraulic connection between groundwater and surface water by allowing 

streams to gain or lose water on the basis of the difference 

between the surrounding hydraulic head and stream stage 

through riverbed material. The hydraulic conductance of this 

material is defined by McDonald and Harbaugh (1988) as 

hydraulic conductivity of the material times the cross-sectional 

area of the stream reach divided by the streambed thickness. 

Estimated riverbed conductance was based on model calibration. Model cells were designated as river leakage cells along 

major streams and tributaries for six streams groups (fig. 14), 

which are (1) the Little White River and tributaries upstream 

from site 12 (fig. 7); (2) the Keya Paha River and tributaries; 

(3) Black Pipe Creek; (4) Gray Eagle and Cut Meat Creeks; 

(5) Sand Creek; and (6) Minnechaduza and Dry Creeks. River 

leakage cells were placed in stream reaches that are at or 

below the estimated potentiometric surface for the recharge 

area of the aquifer upon which the reach is located (figs. 4 

and 5). Above these altitudes, streams are dry except during 

intense storms. Digital elevation data were used to determine 

stream locations, and thus river leakage cells do not always 

coincide exactly with streams shown on figure 14.

The Drain Package simulated springs discharging from 

the Ogallala aquifer along the banks of the Little White River 

and along the northern edge of the Arikaree aquifer (fig. 14). 

The Drain Package is similar to the River Package except that 

drain cells can only take water out of the aquifer, whereas river 

Figure 13. Estimated vertical hydraulic conductivity (K), in feet per day, for the Arikaree aquifer in five parameter 

zones where overlain by the Ogallala aquifer. 

9.2x10-3

Zone 3

1.3x10-2

Zone 5

1.0x10-1

Zone 4

8.8x10-5

Zone 1

3.7

Zone 2

Qa

Tw

T.

102

N.

T.

101

N.

T.

100

N.

T.

98

N.

T.

97

N.

T.

96

N.

T.

95

N.

T.

99

N.

R. 33 W. R. 32 W. R. 31 W. R. 30 W. R. 29 W. R. 28 W. R. 27 W. R. 26 W. R. 25 W. R. 79 W.

MELLETTE COUNTY

BENNETT COUNTY

TODD COUNTY

TODD COUNTY

CHERRY COUNTY

JACKSON COUNTY

TRIPP COUNTY

83

83

18

18

Little

White

Keya Paha

River

River

South

Cr

Cr

Cr

Gray

Beads

Omaha

Rosebud

Phister

S. Ironwood Creek

Creek

Lone Tree

Creek

Creek

Soldier Creek

Eagletail

Sand Creek

Creek

Creek

Creek

Thunder

Creek

White

Rock

Spring

Black

Pipe

Creek

Antelope

Eagle

Oak

Creek

Cut

Meat

Creek

Creek

North

Pine

Branch

Branch

Creek

Creek

Minnechaduza

Dry

Creek

White River

Wood

Okreek Carter

Parmelee

Mission Antelope

Rosebud

Blackpipe

St. Francis

Olsonville

Norris

101°15' 101° 100°45' 100°30' 100°15'

43°

43°15'

43°30'

Base from U.S. Geological Survey digital data 1:100,000, 1980, 1982, 1983, 1985

Universal Transverse Mercator projection, zone 14

0 5 10 MILES

0 5 10 KILOMETERS

NEBRASKA

SOUTH DAKOTA
Numerical Model 27

cells can also recharge the aquifer (McDonald and Harbaugh, 

1988). Model cells were designated as drain cells for seven 

spring groups (fig. 14), and drain (spring) conductance was 

estimated by model calibration for each spring group.

Well withdrawals were simulated with the Well Package 

(McDonald and Harbaugh, 1988) to withdraw water from each 

well at a specified rate. Well withdrawals used in the transient simulation are listed in table 4, and locations are shown 

in figures 8 and 14. Because water use was negligible from 

October through May, total annual withdrawals were assigned 

to the summer stress periods only (June–September). For 

the steady-state calibration, the average withdrawal rate was 

calculated as 11.6 ft3/s.

Model Calibration

The steady-state simulation was calibrated to the estimated average water levels shown in figures 4 and 5 and to the 

estimated base flows listed in table 3. The transient model was 

Figure 14. River cells, evapotranspiration zones, spring cells, and water-supply wells in the Ogallala and Arikaree aquifers.

Cell simulating river leakage

Cell simulating spring discharge

Water-supply well in Ogallala aquifer

Water-supply well in Arikaree aquifer

Ogallala Formation outcrop cells

Arikaree Formation outcrop cells

Evapotranspiration extinction depth equals 10 feet 

(7 feet elsewhere)

Spring group showing parameter name

BLACKP_SP

LW2D_SP

LW3D_SP

WT_SP

WT_SP

EXPLANATION

Qa

Tw

T.

102

N.

T.

101

N.

T.

100

N.

T.

98

N.

T.

97

N.

T.

96

N.

T.

95

N.

T.

99

N.

R. 33 W. R. 32 W. R. 31 W. R. 30 W. R. 29 W. R. 28 W. R. 27 W. R. 26 W. R. 25 W. R. 79 W.

MELLETTE

COUNTY

BENNETT COUNTY

TODD COUNTY

TODD COUNTY

CHERRY COUNTY

JACKSON COUNTY

TRIPP COUNTY

83

83

18

18

Little

White

Keya Paha

River

River

South

Cr

Cr

Cr

Gray

Beads

Omaha

Rosebud

Phister

S. Ironwood Creek

Creek

Lone Tree

Creek

Creek

Soldier Creek

Eagletail

Sand Creek

Creek

Creek

Creek

Thunder

Creek

White

Rock

Spring

Black

Pipe

Creek

Antelope

Eagle

Oak

Creek

Cut

Meat

Creek

Creek

North

Pine

Branch

Branch

Creek

Creek

Minnechaduza

Dry

Creek

White River

Wood

Okreek Carter

Parmelee Mission Antelope

Rosebud

Blackpipe

St. Francis

Olsonville

Norris

101°15' 101° 100°45' 100°30' 100°15'

43°

43°15'

43°30'

Base from U.S. Geological Survey digital data 1:100,000, 1980, 1982, 1983, 1985

Universal Transverse Mercator projection, zone 14

0 5 10 MILES

0 5 10 KILOMETERS

NEBRASKA

SOUTH DAKOTA

L_WHITE_SP

LW1D_SP

OAK_SP
28 Simulated Groundwater Flow in the Ogallala and Arikaree Aquifers, Rosebud Indian Reservation Area

calibrated to water levels measured frequently in Tribal and 

State observation wells during water years 1979–2008. 

Steady-State Simulation

Steady-state conditions were numerically approximated 

by simulating a 100-year stress period in transient mode with 

constant recharge and discharge rates. This method was more 

numerically stable and used fewer iterations than the equivalent simulation in steady-state mode. The potentiometric 

surface from the steady-state simulation established initial 

conditions for the transient simulation. 

Calibration of the steady-state model primarily was 

accomplished by applying what is commonly known as 

inverse modeling. This method is an efficient way to determine an optimum set of parameter values that minimize the 

residuals between measured and simulated flow metrics, such 

as hydraulic head, base flow, and spring flow. Parameters estimated by inverse modeling were those describing hydraulic 

conductivity (K), recharge, maximum evapotranspiration, 

riverbed conductance, and spring conductance. 

Optimization of parameter values by inverse modeling 

was accomplished by linking the parameter estimation software PEST (Doherty, 2004) with MODFLOW-2000. PEST is 

an iterative parameter estimation process that applies nonlinear estimation techniques described by Levenberg (1944), 

Marquardt (1963), and Doherty (2004). This allows a nonlinear problem to be linearized in relation to the best parameter 

set for the current iteration. A new set of parameters is then 

estimated in an attempt to improve model calibration, and the 

process is repeated until the residuals are minimized. Parameter sensitivities and confidence intervals are determined by 

calculating the derivatives of all observations with respect to 

all parameters. This calibration approach was considered an 

improvement over the trial-and-error methods because it was 

more efficient and objective and provided a statistical assessment of model uncertainty, including confidence intervals on 

estimated parameter values and a matrix of parameter correlation coefficients.

Table 7. Selected data for Tribal observation wells in the study area.

[Hydraulic heads are estimated averages for water years 1979–98. NGVD of 1929, National Geodetic Vertical Datum of 1929]

Well 

name 

(figs. 9 

and 10)

Site identification 

numer Legal location Aquifer

Land surface 

altitude (feet 

above NGVD 

of 1929)

Well 

depth 

(feet)

Average 

measured 

hydraulic 

head (feet 

above NGVD 

of 1929)

Steady-state 

simulated 

hydraulic 

head (feet 

above NGVD 

of 1929)

Residuala

RST-3 430309100570901 36N31W34DBBC Ogallala 2,920 91 2,865 2,833 -32

RST-4 430017100595101 35N31W17CCDA Ogallala 2,896 62 2,893 2,888 -5

RST-5 430159100531001 35N30W 6DDDD Ogallala 2,853 84 2,832 2,850 18

RST-6 430501100504901 36N30W22CBBB Ogallala 2,888 137 2,858 2,860 2

RST-7 430415100451401 36N29W29ACAA Ogallala 2,870 134 2,851 2,830 -21

RST-8 430258100471401 36N30W36DDDA Ogallala 2,885 123 2,836 2,846 10

RST-9 430100100460501 35N29W18AAAA Ogallala 2,870 84 2,831 2,844 13

RST-10 430154100411801 35N29W 2DDDD Ogallala 2,800 44 2,792 2,790 -2

RST-11 430530100422501 36N29W14CDAB Ogallala 2,893 200 2,811 2,801 -10

RST-12 430712100421301 36N29W 2CDCC Ogallala 2,850 200 2,804 2,791 -13

RST-13 430755100582301 37N29W31DACC Ogallala 2,921 275 2,815 2,824 9

RST-15 431342100344101 38N28W36ABCB Arikaree 2,620 73 2,609 2,577 -32

RST-16 430820100371401 37N28W34ABDA Ogallala 2,783 171 2,725 2,733 8

RST-17 431027100333001 37N27W18DDAB Ogallala 2,609 53 2,605 2,613 8

RST-18 430702100330501 36N28W12AABA Ogallala 2,806 215 2,660 2,678 18

RST-19 430243100371701 36N28W33BDDD Ogallala 2,753 75 2,723 2,732 9

RST-20 430122100344501 35N28W11DBBB Ogallala 2,728 94 2,711 2,711 0

RST-21 430057100275401 35N27W14BAAB Ogallala 2,690 84 2,671 2,636 -35

RST-22 430335100241401 36N26W32BBAA Ogallala 2,619 78 2,589 2,594 5

RST-23 430728100135801 36N27W 1BDDD Ogallala 2,627 58 2,600 2,607 7

RST-27 431127100532801 37N30W 8DACC Ogallala 2,880 150 2,759 2,805 46

a

Residual is the difference between simulated hydraulic head and average measured hydraulic head.
Numerical Model 29

The criterion for estimating optimum parameter values 

was to achieve a minimum value for the sum of the squared 

and weighted residuals, or differences, between simulated 

and observed hydraulic heads and base flows in streams. This 

is referred to as the objective function. Water-level measurements for 383 wells that were used for estimation of potentiometric surfaces of the Ogallala and Arikaree aquifers (figs. 

4 and 5) were used in calibration of the steady-state model. 

These wells included 44 observation wells with long-term 

water-level records that also were used for calibration of the 

transient model. The rest were wells mainly used for water 

supply. The observation wells included 21 Tribal wells, of 

which 20 were completed in the Ogallala aquifer and 1 was 

completed in the Arikaree aquifer, and 23 State wells, of 

which 17 were completed in the Ogallala aquifer and 6 were 

completed in the Arikaree aquifer (figs. 9 and 10). Selected 

data for the Tribal and State observation wells are shown 

in table 7 and table 8, respectively. The model also was 

calibrated to estimated base flow in streams. As described in 

the “Conceptual Model” section, estimated base-flow values 

for the Little White River, Keya Paha River, Cut Meat Creek, 

Black Pipe Creek, Minnechaduza Creek, and Sand Creek were 

49, 23, 1.7, 1.2, 3.0, and 3.9 ft3/s, respectively.

The primary calibration objective was to minimize the 

objective function. A second calibration objective for the 

steady-state simulation was to have the simulated potentiometric surfaces and hydraulic gradients generally resemble those 

of the estimated average potentiometric surfaces (water years 

1979–98). The simulated steady-state potentiometric surfaces 

(figs. 15 and 16) are similar to the estimated average potentiometric surfaces (figs. 4 and 5) in comparisons of both hydraulic heads and gradients. 

Simulated hydraulic heads matched observed values 

to within ±50 ft for 93 percent of the 383 wells used in 

the steady-state calibration. Fifty feet is about 7 percent 

of the total hydraulic head relief for the estimated average 

Table 8. Selected data for State observation wells in the study area.

[Hydraulic heads are estimated averages for water years 1979–98. NGVD of 1929, National Geodetic Vertical Datum of 1929]

Well 

name 

(figs. 9 

and 10)

Site identification 

number Legal location Aquifer

Land surface 

altitude (feet 

above NGVD 

of 1929)

Well 

depth 

(feet)

Other 

name

Average 

measured 

hydraulic 

head (feet 

above NGVD 

of 1929)

Steady-state 

simulated 

hydraulic 

head (feet 

above NGVD 

of 1929)

Residuala

BT-76C 431018101152001 37N33W17CCCC Ogallala 2,998 181 S207 2,930 2,929 -1

BT-80E 430825101151801 37N33W32BBBB2 Ogallala 2,960 143 S170 2,902 2,901 -1

MT-78A 432554101065601 40N32W21BBBB Arikaree 2,576 163 S384 2,561 2,567 6

TD-59A 430148100471001 35N29W 7BBBB Ogallala 2,903 83 S41 2,837 2,849 12

TD-59B 425957100445601 35N29W20AADD Ogallala 2,890 128 S2 2,804 2,833 29

TD-76A 431109100445901 37N29W16AAAA Ogallala 2,852 184 S219 2,754 2,786 32

TD-76B 430924100460601 37N29W29AAAA Ogallala 2,868 204 S194 2,790 2,802 12

TD-76C 430748100455601 37N29W33CCCC Ogallala 2,909 203 S160 2,817 2,814 -3

TD-76D 430840100445601 37N29W28DDDD Ogallala 2,858 195 S176 2,791 2,793 2

TD-76E 430610100481701 36N30W13BBBB Ogallala 2,916 225 S126 2,843 2,844 1

TD-76F 430609100434201 36N29W16AAAA Ogallala 2,863 222 S125 2,822 2,809 -13

TD-76G 430842100411301 37N28W30CCCB Ogallala 2,770 184 S177 2,745 2,764 19

TD-76H 430932100390001 37N28W21CCCC Ogallala 2,772 163 S201 2,727 2,731 4

TD-76I 430839100373801 37N28W27CCCC Ogallala 2,805 182 S175 2,727 2,739 12

TD-76J 430701100363001 36N28W10BBBB Ogallala 2,823 183 S145 2,750 2,745 -5

TD-79A 431020100243501 37N26W16CCBB Arikaree 2,530 137 S210 2,523 2,521 -2

TD-79B 430613101561701 36N31W14BAAA Ogallala 2,955 160 S130 2,816 2,830 14

TD-79D 432044101115201 39N33W15DDDD Arikaree 2,800 360 S361 2,764 2,781 17

TD-80A 432310101045501 39N32W 3AAAA Arikaree 2,610 125 S374 2,578 2,585 7

TD-80B 430340101012301 36N32W25DDDD Ogallala 2,841 125 S87 2,834 2,829 -5

TD-80C 430959100444001 37N29W22CCCC Arikaree 2,882 265 S205 2,781 2,787 6

TD-80D 431430100195901 38N25W30BCBB Arikaree 2,483 144 S274 2,458 2,451 -7

TD-80E 430310100245501 36N26W31ADDD Ogallala 2,620 125 S80 2,594 2,605 11

a

Residual is the difference between simulated hydraulic head and average measured hydraulic head.
30 Simulated Groundwater Flow in the Ogallala and Arikaree Aquifers, Rosebud Indian Reservation Area

potentiometric surfaces in the model area, which is about 

780 ft for the Ogallala aquifer and 720 ft for the Arikaree 

aquifer. A histogram shows the distribution of the hydraulichead residuals for the 383 wells (fig. 17). Results for the

44 observation wells was better than for all 383 wells. Simulated hydraulic heads for observation wells were within ±40 ft 

of the observed hydraulic heads for 98 percent of these wells. 

The root mean square error (RMSE) for all 383 wells was 

27.3 ft. The mean error was 4.3 ft, which indicates a slight 

model bias toward overestimating hydraulic head values. For 

the observation wells only, the RMSE was 15.8 ft, and the 

mean error was 3.4 ft. A linear regression analysis of simulated 

and observed water levels for all 383 wells (fig. 18) yielded 

an R2 value (coefficient of determination) of 0.97. The total 

simulated base flow was 73.3 ft3/s, which is about 10 percent 

less than the total estimated base flow of 81.8 ft3/s (table 9). 

Because a large number of estimated parameters can 

result in high parameter correlations and large parameter 

confidence intervals, the horizontal K areas were grouped into 

five major parameter zones for each model layer (figs. 11 and 

Figure 15. Potentiometric surface of the Ogallala aquifer for steady-state simulation.

EXPLANATION

Qa

Tw

T.

102

N.

T.

101

N.

T.

100

N.

T.

98

N.

T.

97

N.

T.

96

N.

T.

95

N.

T.

99

N.

R. 33 W. R. 32 W. R. 31 W. R. 30 W. R. 29 W. R. 28 W. R. 27 W. R. 26 W. R. 25 W. R. 79 W.

MELLETTE

COUNTY

BENNETT COUNTY

TODD COUNTY

TODD COUNTY

CHERRY COUNTY

JACKSON COUNTY

TRIPP COUNTY

83

83

18

18

Little

White

Keya Paha

River

River

South

Cr

Cr

Cr

Gray

Beads

Omaha

Rosebud

Phister

S. Ironwood Creek

Creek

Lone Tree

Creek

Creek

Soldier Creek

Eagletail

Sand Creek

Creek

Creek

Creek

Thunder

Creek

White

Rock

Spring

Black

Pipe

Creek

Antelope

Eagle

Oak

Creek

Cut

Meat

Creek

Creek

North

Pine

Branch

Branch

Creek

Creek

Minnechaduza

Dry

Creek

White River

Wood

Okreek Carter

Parmelee Mission Antelope

Rosebud

Blackpipe

St. Francis

Olsonville

Norris

101°15' 101° 100°45' 100°30' 100°15'

43°

43°15'

43°30'

Base from U.S. Geological Survey digital data 1:100,000, 1980, 1982, 1983, 1985

Universal Transverse Mercator projection, zone 14

0 5 10 MILES

0 5 10 KILOMETERS

Ogallala aquifer active cells

Simulated potentiometric contour—Shows average 

altitude at which water level would have stood in 

tightly cased wells, water years 1979–98. Contour 

interval is 50 feet. Datum is NGVD of 1929

2700

2700

2800

2650

2600

2900

2950

2850

3000

2500

2500

2550

2500

2550

2550

2450

2400

2500

2550

2350

2350

2450

2400

2450

3050

3000

2900

2750

2700

2600

2600

2950

2600

2750

2750

2750

2800

2900

2600

2850

2850

2400

SOUTH DAKOTA

NEBRASKA

2750

2650
Numerical Model 31

12). One parameter value was estimated by inverse modeling for each of these 10 zones. Prior to executing the inverse 

modeling process, these parameter values were multiplied 

by values assigned to subareas within the parameter zones to 

allow variation within parameter zones. Subarea values were 

assigned on the basis of specific capacities of wells (Long 

and others, 2003) and the assumption that horizontal K for 

the Arikaree aquifer is highest near streams (figs. 11 and 12). 

Trial-and-error was used to further refine subarea values in an 

iterative process with inverse modeling in order to minimize 

the objective function. As a result of this calibration process, 

an additional subarea, which was not part of the previously 

published model, was delineated in the northeastern part of 

zone 1 (horizontal K of 1.3 ft/d, fig. 11). 

The shaded subareas in figures 11 and 12 show the results 

of this multiplication, which are the final horizontal K values 

used in the steady-state simulation. Vertical K was assumed 

to be homogeneous within each of the five parameter zones 

for the Arikaree aquifer (fig. 13), and a uniform vertical K

value was applied to the Ogallala aquifer because parameter 

Figure 16. Potentiometric surface of the Arikaree aquifer for steady-state simulation.

EXPLANATION

Qa

Tw

T.

102

N.

T.

101

N.

T.

100

N.

T.

98

N.

T.

97

N.

T.

96

N.

T.

95

N.

T.

99

N.

R. 33 W. R. 32 W. R. 31 W. R. 30 W. R. 29 W. R. 28 W. R. 27 W. R. 26 W. R. 25 W. R. 79 W.

MELLETTE

COUNTY

BENNETT COUNTY

TODD COUNTY

TODD COUNTY

CHERRY COUNTY

JACKSON COUNTY

TRIPP COUNTY

83

83

18

18

Little

White

Keya Paha

River

River

South

Cr

Cr

Cr

Gray

Beads

Omaha

Rosebud

Phister

S. Ironwood Creek

Creek

Lone Tree

Creek

Creek

Soldier Creek

Eagletail

Sand Creek

Creek

Creek

Creek

Thunder

Creek

White

Rock

Spring

Black

Pipe

Creek

Antelope

Eagle

Oak

Creek

Cut

Meat

Creek

Creek

North

Pine

Branch

Branch

Creek

Creek

Minnechaduza

Dry

Creek

White River

Wood

Carter

Okreek

Parmelee Mission Antelope

Rosebud

Blackpipe

St. Francis

Olsonville

Norris

101°15' 101° 100°45' 100°30' 100°15'

43°

43°15'

43°30'

Base from U.S. Geological Survey digital data 1:100,000, 1980, 1982, 1983, 1985

Universal Transverse Mercator projection, zone 14

0 5 10 MILES

0 5 10 KILOMETERS

Arikaree aquifer active cells

Simulated potentiometric contour—Shows average 

altitude at which water level would have stood in 

tightly cased wells, water years 1979–98. Contour 

interval is 50 feet. Datum is NGVD of 1929

SOUTH DAKOTA

NEBRASKA

2600

2650

2600

2550

2700

2650

2800

2750

2850

2900

2850

2800

2750

2700

2550

2950

2900

2500

2450

3000

2450

2450

2500

2500

2500

2400

2400

3050

2350

2500

2500

2500

2550

2550

2550

2450

2450

2600

2500

2450

2550

2450

2800

2950

2950

3000

2600

2450

2400
32 Simulated Groundwater Flow in the Ogallala and Arikaree Aquifers, Rosebud Indian Reservation Area

estimates for only one of the two intervening layers need to be 

adjusted for calibration. This resulted in a total of six parameter values for vertical K. Greater discretization of horizontal 

or vertical K might have further minimized the objective 

function by adjusting K near individual wells or small groups 

of wells, but the available data did not support this degree of 

detail. Therefore, the calibration accuracy obtained using these 

parameter zones and subareas was considered sufficient to 

fulfill the objectives of this study. 

The remaining parameter categories were recharge, 

maximum evapotranspiration, riverbed conductance, and 

spring conductance. Two recharge rates were estimated by 

inverse modeling: one rate for the Ogallala aquifer recharge 

area and a second rate for the Arikaree aquifer recharge area 

(fig. 8). A single value applied to the entire model for the 

maximum evapotranspiration rate was estimated by inverse 

modeling. A value for each of the six riverbed conductance 

cell groups and seven spring conductance cell groups was 

estimated by inverse modeling (fig. 14). With these additional 

parameter values, there were a total of 32 values to be estimated by inverse modeling for the steady-state simulation 

(table 10). 

These 32 parameter values were estimated during an 

initial execution of the inverse modeling process. However, 

diagnostics, such as large parameter confidence intervals, 

insensitivity of several parameters, and many highly correlated parameters, indicated the need to group some parameters 

together and thereby reduce the total number of parameters to 

be estimated directly by inverse modeling. This was accomplished by tying parameters together, a method in which a 

Figure 17. Histogram of residuals of average observed and steady-state simulated hydraulic head for 383 wells, water 

years 1979–98.

0

10

20

30

40

50

60

70

80

90

-125 -115 -105 -95 -85 -75 -65 -55 -45 -35 -25 -15

RESIDUAL, IN FEET

FREQUENCY

-5 5 15 25 35 45 55 65 75 85 95 105 115 125

Table 9. Comparison of steady-state simulated and 

estimated base flows for six surface-water drainage 

basins.

[ft3/s, cubic feet per second]

Stream

Base flow (ft3/s)

Estimated Steady-state 

simulateda

Little White River 49.0 36.7

Keya Paha River 23.0 20.0

Cut Meat Creek 1.7 8.4

Black Pipe Creek 1.2 1.3

Minnechaduza Creek 3.0 3.2

Sand Creek 3.9 3.8

 Total 81.8 73.3

a

Net outflow. Includes spring flow along river banks.
Numerical Model 33

parameter is tied to an independent parameter, which can be 

adjusted during the inverse modeling process. The two parameters maintain a constant ratio based on their starting values, 

but only the independent parameter takes an active role in the 

inverse modeling process. Parameter confidence intervals are 

calculated for independent parameters but not for tied parameters (table 10). The least sensitive parameters were tied to 

more sensitive parameters of the same type. The 32 parameter 

values estimated during the initial execution were used as 

starting values for the independent and tied parameters. 

Recharge to the Arikaree aquifer was tied to recharge to 

the Ogallala aquifer. All of the vertical K parameters for the 

Arikaree aquifer were tied to the single vertical K parameter 

for the Ogallala aquifer. Riverbed conductance parameters for 

small drainage basins were tied to the Little White and Keya 

Paha River conductance parameters, and most of the spring 

conductance parameters were tied to one spring. This resulted 

in 15 independent parameters estimated directly by inverse 

modeling and 17 parameters estimated indirectly by being 

tied to 7 of the independent parameters (table 10). The range 

of values within which each parameter could be estimated 

was limited to what was considered physically reasonable. 

This prevented PEST from estimating unreasonable parameter 

values simply because they reduced the value of the objective 

function.

PEST calculated 95-percent confidence intervals on 

parameters, which indicates 95 percent confidence that a 

parameter value within this range results in the smallest 

possible objective function (table 10). In the final execution, 

the largest confidence intervals were associated with parameters WT_SP, VKA1_1, KEYA_PAHA, and L_WHITE_SP. 

It is noted that these confidence intervals rely on an assumption of linearity, which might not be valid at wide confidence 

limits. Other parameters, for example RECH1, had small 

confidence intervals indicating a high degree of confidence in 

these estimates relative to some other parameters. The estimated recharge rates for the Ogallala and Arikaree aquifers of 

2.91 and 1.45 in/yr, respectively, are about 15 and 7.5 percent 

of average precipitation for the simulated period.

The water budget for the steady-state simulation balanced 

(inflows minus outflows) with a discrepancy of 0.2 percent 

(table 11). Total inflow from model constant-head boundaries 

Figure 18. Linear regression of average observed and simulated steady-state hydraulic heads for 383 wells, water 

years 1979–98.

2,300

2,300

2,400

2,400

2,500

2,500

2,600

2,600

2,700

2,700

2,800

2,800

2,900

2,900

3,000

3,000

3,100

3,100

OBSERVED HYDRAULIC HEAD, IN FEET ABOVE NGVD OF 1929

SIMULATED HYDRAULIC HEAD, IN FEET ABOVE NGVD OF 1929

Arikaree aquifer

Ogallala aquifer
34 Simulated Groundwater Flow in the Ogallala and Arikaree Aquifers, Rosebud Indian Reservation Area

Table 10. Parameter values estimated by inverse modeling for the steady-state simulation.

[ft/d, feet per day; ft2/d, feet squared per day; in/yr, inches per year; --, not applicable]

Parameter 

name

Estimated value

95-percent confidence intervals

Units Tied to

Value applied 

to transient 

model

Description Lower limit Upper limit

HK1_1 48.81 21.98 108.40 ft/d -- Yes Horizontal hydraulic conductivity layer 1, zone 1.

HK1_2 15.25 1.47 158.41 ft/d -- Yes Horizontal hydraulic conductivity layer 1, zone 2.

HK1_3 25.61 12.30 53.32 ft/d -- Yes Horizontal hydraulic conductivity layer 1, zone 3.

HK1_4 4.54 -- -- ft/d HK1_5 Yes Horizontal hydraulic conductivity layer 1, zone 4.

HK1_5 40.33 10.45 155.58 ft/d -- Yes Horizontal hydraulic conductivity layer 1, zone 5.

HK2_1 2.52 .42 15.07 ft/d -- Yes Horizontal hydraulic conductivity layer 2, zone 1.

HK2_2 1.44 .58 3.58 ft/d -- Yes Horizontal hydraulic conductivity layer 2, zone 2.

HK2_3 .81 .69 .95 ft/d -- Yes Horizontal hydraulic conductivity layer 2, zone 3.

HK2_4 .06 -- -- ft/d HK2_5 Yes Horizontal hydraulic conductivity layer 2, zone 4.

HK2_5 .73 .10 5.12 ft/d -- Yes Horizontal hydraulic conductivity layer 2, zone 5.

VKA1_1 4.18x10-4 3.45x10-7 .507 ft/d -- Yes Vertical hydraulic conductivity layer 1.

VKA2_1 8.77x10-5 -- -- ft/d VKA1_1 Yes Vertical hydraulic conductivity layer 2, zone 1.

VKA2_2 3.66 -- -- ft/d VKA1_1 Yes Vertical hydraulic conductivity layer 2, zone 2.

VKA2_3 9.18x10-3 -- -- ft/d VKA1_1 Yes Vertical hydraulic conductivity layer 2, zone 3.

VKA2_4 .101 -- -- ft/d VKA1_1 Yes Vertical hydraulic conductivity layer 2, zone 4.

VKA2_5 1.32x10-2 -- -- ft/d VKA1_1 Yes Vertical hydraulic conductivity layer 2, zone 5.

RECH1 2.91 2.80 3.03 in/yr -- No Recharge layer 1.

RECH2 1.45 -- -- in/yr RECH1 No Recharge layer 2.

EVTR1 53.02 48.71 57.70 in/yr -- No Maximum evapotranspiration rate.

L_WHITE 8.64x103 1.79x103 4.16x104 ft2/d -- Yes Riverbed conductance.

KEYA_PAHA 4.72x103 22.0 1.01x106 ft2/d -- Yes Riverbed conductance.

CUTMEAT 5.56x102 -- -- ft2/d L_WHITE Yes Riverbed conductance.

MDUZA 4.01x103 -- -- ft2/d L_WHITE Yes Riverbed conductance.

BLACKPIPE 1.44x102 -- -- ft2/d L_WHITE Yes Riverbed conductance.

SAND 4.72x103 -- -- ft2/d KEYA_PAHA Yes Riverbed conductance.

L_WHITE_SP 1.00x104 2.17x102 4.61x105 ft2/d -- Yes Spring conductance.

BLACKP_SP 9.80x102 -- -- ft2/d WT_SP Yes Spring conductance.

LW1D_SP 9.75x102 -- -- ft2/d WT_SP Yes Spring conductance.

LW2D_SP 1.00x103 -- -- ft2/d WT_SP Yes Spring conductance.

LW3D_SP 1.00x103 -- -- ft2/d WT_SP Yes Spring conductance.

WT_SP 1.28x103 1.14 1.45x106 ft2/d -- Yes Spring conductance.

OAK_SP 9.80x102 -- -- ft2/d WT_SP Yes Spring conductance.
Numerical Model 35

for the steady-state simulation was 12.5 ft3/s. Discharge rates 

for the steady-state simulation were 171.3 ft3/s for evapotranspiration, 74.4 ft3

/s for net outflow (outflow minus inflow) to 

streams and springs, 11.6 ft3/s for well withdrawals, and 

9.9 ft3/s as outflow from model constant-head boundaries. 

A sensitivity analysis was used to examine the response 

of the steady-state model to changes in parameter values. 

During each simulation when a parameter was being tested, 

the other parameters remained at the steady-state calibrated 

value. The fractional changes in the objective function values 

for a 5-percent change in parameter values are shown in figure 

19. The model was most sensitive to HK2_3, RECH1, and 

RECH2 followed by HK1_3, VKA1_1, and EVTR1. In terms 

of parameter classes, the model was most sensitive to recharge 

and maximum evapotranspiration rate and least sensitive to 

riverbed and spring conductances (fig. 20). 

This sensitivity analysis was useful for quantifying the 

sensitivity of each parameter with respect to all other parameters. The information gained from this analysis is limited, 

however, because it does not take into account parameter 

sensitivities as they covary with other parameters. Confidence 

intervals on parameter estimates calculated by PEST take into 

account these sensitivities as parameters covary (Doherty, 

2004) and thus provide an assessment of confidence in the 

values estimated. Also, high correlation between two parameters indicates parameter sets that when varied in a complementary manner have little effect on the objective function value 

(Doherty, 2004), and thus highly correlated parameters are 

not desirable. A matrix of parameter correlation coefficients 

for the independent parameters shows no highly correlated 

parameter pairs (correlation coefficient greater than 0.95) with 

the highest correlation coefficient of 0.64 occurring between 

RECH1 and VKA1_1 (table 12). 

A comparison of estimated K values shows differences 

between calibration of the model described by Long and 

others (2003) and the revised model described in this report 

(table 13). The percent deviation from Long and others (2003) 

ranged from 0 for several values to more than 900 for one 

of the vertical K values (table 13). Estimated values with the 

largest percent change were associated with the small parameter sensitivities (fig. 19), and thus, changes in these parameter 

values resulted in only minor changes to model outcome. 

These and other revisions to the model resulted in minor 

changes to the steady-state water budget (table 11).

Transient Simulation

All parameter estimates from the steady-state calibration 

except for the time-varying parameters recharge and maximum 

evapotranspiration rate were applied to the transient model 

(table 10). Estimated recharge and maximum evapotranspiration rates for the transient model are shown in tables 6 and 

2, respectively. Estimated recharge for the Arikaree aquifer 

was one-half that of the Ogallala aquifer (table 6). Additional adjustments to model parameters were not necessary 

to achieve acceptable calibration. Calibration criteria for the 

transient simulation consisted of approximately reproducing 

the general temporal trends of the hydrographs for the 

44 observation wells. No attempt was made to calibrate the 

transient simulation to match hydraulic heads in the observation wells closer than that required for the steady-state

simulation (±50 ft). Therefore, a difference of as much as

50 ft between the observed and simulated well hydrographs 

was acceptable if the general trends matched reasonably well.

In most cases, the simulated water levels were within 

40 ft of observed values, and the general trends in simulated 

and observed hydraulic heads matched reasonably well with 

some exceptions (figs. 21 and 22). In some cases, the simulated hydrograph had an upward trend when the observed 

hydrograph had a downward trend, or the opposite. In other 

cases, the trends were consistent. Although the simulated 

hydrograph trends were not always consistent with those 

observed, the overall variability of simulated hydrographs 

generally was consistent with the variability of the observed 

hydrographs, and it is this variability that is of most concern 

for purposes of simulating the effects of drought or increased 

pumping. Measured water levels for well RST-19 (fig. 22) 

declined by about 30 ft in less than 1 year. Because this is 

unusual for the Ogallala aquifer and is the only well where 

such a large decline occurred, the data may be in error. 

Table 11. Water budget for steady-state simulation compared 

with the water budget from Long and others (2003).

[ft3/s, cubic feet per second; %, percent]

Flow rate (ft3/s)

2003 modela Revised model 

(this report)

Inflows

Storage 0.5 0.2

Constant-head boundary 17.9 12.5

River leakage 2.1 8.1

Recharge 266.2 255.4

 Total inflows 286.7 276.1

Outflows

 Storage 0.7 0.2

Constant-head boundary 13.2 9.9

Well withdrawals 11.6 11.6

Springs along northern boundary.5 1.1

River leakageb 78.0 81.4

Evapotranspiration 183.9 171.3

 Total outflows 287.9 275.5

Summary

Inflows minus outflows -1.2 0.6

Budget descrepancy -.4% .2%

a

Long and others (2003).

b

Includes spring flow along river banks.
Table 12. Parameter correlation matrix showing correlation coefficients for all parameter pair combinations. (Parameter names defined in table [--, not included because of redundancy] Parameter name L_WHITE_SP WT_SP HK1_1 HK1_2 HK1_3 HK1_5 HK2_1 HK2_2 HK2_3 HK2_5 VKA1_1 RECH1 EVTR1 L_WHITE_SP 1.00 -- -- -- -- -- -- -- -- -- -- -- -- WT_SP -.52 1.00 -- -- -- -- -- -- -- -- -- -- -- HK1_1 -.07 .02 1.00 -- -- -- -- -- -- -- -- -- -- HK1_2 -.04 .03 0 1.00 -- -- -- -- -- -- -- -- -- HK1_3 -.08 .02 .10 .18 1.00 -- -- -- -- -- -- -- -- HK1_5 -.02 -.01 .04 .20 .32 1.00 -- -- -- -- -- -- -- HK2_1 .04 -.09 -.10 -.01 .13 .06 1.00 -- -- -- -- -- -- HK2_2 -.01 .02 .04 .02 .23 .18 .07 1.00 -- -- -- -- -- HK2_3 -.35 .26 .04 0 -.07 .01 -.01 .01 1.00 -- -- -- -- HK2_5 .01 .11 .04 .01 .10 -.14 .06 .05 .01 1.00 -- -- -- VKA1_1 -.07 .12 -.19 .14 -.29 -.03 -.28 -.12 -.07 -.19 1.00 -- -- RECH1 -.10 .10 -.07 .38 .26 .40 -.11 .18 -.03 -.06 .64 1.00 -- EVTR1 -.02 .01 0 .06 .06 .08 0 .07 0 .01 .02 .14 1.00 L_WHITE .14 .18 .03 -.02 .01 -.01 -.13 .01 .01 .01 -.10 -.07 -.01 KEYA_PAHA .01 -.77 .02 -.02 .02 .03 .02 -.03 .01 -.15 -.08 -.06 0 
Numerical Model 37

Simulation of Potential Future Scenarios

Model simulations were conducted to assess groundwater responses to potential future drought and increases in 

well withdrawals. A synthetic drought simulation recharge 

record was created that has similar variability to that of the 

original estimated record (table 6), except that on average, 

the synthetic drought record was approximately equal to 

the 30th-percentile recharge rates for each model season of 

the original record. Random variability was added to this 

30th-percentile recharge rate for each season with a maximum 

possible variability that was similar to that of the original 

estimated record for each respective season. This resulted in a 

mean drought recharge rate for the overall record of 1.87 in/yr 

for the Ogallala aquifer, or 64 percent of the original average 

recharge rate of 3.91 in/yr. The simulation was executed as a 

30-year transient simulation with the first 10 years having the 

same recharge as in the original record. The synthetic drought 

record was used for last 20 years of the simulation. Hydrographs of the simulated observation wells plotted with results 

of the non-drought simulation show the effects of this drought 

scenario for selected sites (fig. 23). The simulated maximum 

decline in water levels for the 44 observation wells as a result 

of the drought simulation ranged from about 1 to 16 ft, and 

about 50 percent of the wells had declines of 8 to 16 ft. 

The differences in hydraulic-head values between results 

of the calibrated model and the drought scenario at the end of 

the 30-year simulation ranged from 0 to 39 ft for the Ogallala 

aquifer. The largest differences were in the northwestern part 

of the model area followed by the center of the model area 

where many irrigation wells are located. The shift in position 

of potentiometric contours from those of the calibrated model 

to those of the drought scenario indicates the differences 

(fig. 24).

To assess the effects of potential increases in pumping, 

well withdrawal rates were increased by 50 percent from those 

listed in table 4 for the last 20 years of record. The first 10 

years of record were unchanged from table 4 (fig. 25). The 

simulated maximum decline in water levels for the 

44 observation wells as a result of simulated pumping 

increases ranged from less than 0.5 to 5 ft. The differences 

in hydraulic-head values between results of the calibrated 

model and the increased scenario of pumping at the end of 

the 30-year simulation ranged from 0 to 13 ft for the Ogallala 

0

0.0002

0.0004

PARAMETER NAME

0.0006

0.0008

0.0010

0.0012

0.0014

0.0016

HK1_1

HK1_2HK1_3HK1_4HK1_5

HK2_1

HK2_2

HK2_3

HK2_4

HK2_5

VKA1_1

VKA2_1

VKA2_2VKA2_3

VKA2_4

VKA2_5

RECH1

RECH2

EVTR1

L_WHITE

KEYA_PAHA

CUTMEAT

MDUZA

BLACKPIPE

SAND

L_WHITE_SP

BL

ACKP_SP

LW1D_SP

LW2D_SP

LW3D_SP

WT_SP

OAK_SP

FRACTIONAL CHANGE, IN OBJECTIVE FUNCTION

Figure 19. Relative parameter sensitivities as a fractional change in the objective function (sum of the squared weighted 

residuals) resulting from a 5-percent change in parameter values. (Parameter names defined in table 10).
38 Simulated Groundwater Flow in the Ogallala and Arikaree Aquifers, Rosebud Indian Reservation Area

aquifer, with the largest differences in the center of the model 

area where many irrigation wells are located. The shift in position of potentiometric contours from those of the calibrated 

model to those of the drought scenario are shown in figure 26; 

the shift generally is only evident in the center of the model 

area where the largest groundwater withdrawals occur.

Model Limitations

For purposes and objectives of this study, the numerical 

model adequately simulates flow in the Ogallala and Arikaree 

aquifers in the study area. However, water managers should 

be aware of the model’s limitations. There are uncertainties in 

model input parameters, most importantly recharge, evapotranspiration, and horizontal and vertical hydraulic conductivity. Although these parameters had a large influence on model 

results, extensive field data with respect to these were not 

available. The objective function possibly could have been 

reduced more by breaking down further the spatial discretization of some parameters, such as hydraulic conductivity or 

recharge; however, without additional field data, finer discretization was not justifiable. Combinations of parameter values 

other than those used in this model also might give satisfactory results, and thus, parameter confidence intervals help to 

quantify the uncertainty in the final set of estimated parameter 

values. The use of inverse modeling methods resulted in more 

objective parameter estimates than did previous trial-and-error 

methods. 

This numerical model is suitable as a tool to help understand the flow system, to help confirm that previous estimates 

of aquifer properties were reasonable, and to estimate aquifer 

properties in areas without data. The model also is useful to 

help assess the effects of drought and increases in pumping 

by simulations of these scenarios, the results of which are not 

precise but may be considered when making water management decisions. Limitations of the model should be taken into 

account when applying the model to water management. With 

additional data, further refinement of the model would be 

possible, which could improve the accuracy of model prediction of the effects of additional stresses on the system, such as 

increased withdrawals or drought.

Figure 20. Relative sensitivities of parameter classes as a percent change in the objective function (sum of the squared 

weighted residuals) resulting from a 5-percent change in parameter values. Sensitivities were calculated as averages of 

those in figure 19.

0

0.0002

0.0004

0.0006

0.0008

0.0010

0.0012

Recharge Maximum

evapotranspiration

Riverbed

conductance

Spring

conductance

FRACTIONAL CHANGE IN OBJECTIVE FUNCTION

Horizontal 

hydraulic 

conductivity

PARAMETER CLASS

Vertical 

hydraulic 

conductivity
Numerical Model 39

2910

2,920

2,930

2,940

2,950

BT-76C OGALLALA AQUIFER

2,890

2,900

2,910

2,920

2,930

BT-80E, OGALLALA AQUIFER

2,540

2,550

2,,560

2,570

2,580

MT-78A, ARIKAREE AQUIFER

HYDRAULIC HEAD, IN FEET ABOVE NGVD OF 1929

2,820

2,830

2,840

2,850

2,860

TD-59A, OGALLALA AQUIFER

1978198019821984198619881990199219941996199820002002200420062008

2,800

2,810

2,820

2,830

2,840

CALENDAR YEAR

TD-59B, OGALLALA AQUIFER

1978198019821984198619881990199219941996199820002002200420062008

2,745

2,755

2,765

2,775

2,785

TD-76A, OGALLALA AQUIFER

Simulated

Observed

EXPLANATION

Figure 21. Hydrographs showing simulated and observed data for State observation wells for calibrated transient model.
40 Simulated Groundwater Flow in the Ogallala and Arikaree Aquifers, Rosebud Indian Reservation Area

Figure 21. Hydrographs showing simulated and observed data for State observation wells for calibrated transient model.—

Continued

CALENDAR YEAR

2,770

2,780

2,790

2,800

2,810

TD-76B, OGALLALA AQUIFER

2,790

2,800

2,810

2,820

2,830

TD-76C, OGALLALA AQUIFER

2,770

2,780

2,790

2,800

2,810 TD-76D,OGALLALA AQUIFER

HYDRAULIC HEAD, IN FEET ABOVE NGVD OF 1929

2,820

2,830

2,840

2,850

2,860 TD-76E, OGALLALA AQUIFER

1978198019821984198619881990199219941996199820002002200420062008

2,790

2,800

2,810

2,820

2,830

TD-76F, OGALLALA AQUIFER

1978198019821984198619881990199219941996199820002002200420062008

2,730

2,740

2,750

2,760

2,770

TD-76G, OGALLALA AQUIFER

Simulated

Observed

EXPLANATION
Numerical Model 41

Figure 21. Hydrographs showing simulated and observed data for State observation wells for calibrated transient model.—

Continued HYDRAULIC HEAD, IN FEET ABOVE NGVD OF 1929

2,710

2,720

2,730

2,740

2,750 TD-76H, OGALLALA AQUIFER

2,710

2,720

2,730

2,740

2,750

TD-76I, OGALLALA AQUIFER

2,730

2,740

2,750

2,760

2,770 TD-76J, OGALLALA AQUIFER

2,500

2,510

2,520

2,530

2,540

TD-79A, ARIKAREE AQUIFER

1978198019821984198619881990199219941996199820002002200420062008

2,800

2,810

2,820

2,830

2,840

TD-79B, OGALLALA AQUIFER

1978198019821984198619881990199219941996199820002002200420062008

2,750

2,760

2,770

2,780

2,790

TD-79D, ARIKAREE AQUIFER

CALENDAR YEAR

Simulated

Observed

EXPLANATION
42 Simulated Groundwater Flow in the Ogallala and Arikaree Aquifers, Rosebud Indian Reservation Area

Figure 21. Hydrographs showing simulated and observed data for State observation wells for calibrated transient model.—

Continued

CALENDAR YEAR

Figure 21d. HYDRAULIC HEAD, IN FEET ABOVE NGVD OF 1929

2,560

2,570

2,580

2,590

2,600 TD-80A, ARIKAREE AQUIFER

2,810

2,820

2,830

2,840

2,850TD-80B, OGALLALA AQUIFER

2,760

2,770

2,780

2,790

2,800 TD-80C, ARIKAREE AQUIFER

1978198019821984198619881990199219941996199820002002200420062008

2,430

2,440

2,450

2,460

2,470

CALENDAR YEAR

TD-80D, ARIKAREE AQUIFER

1978198019821984198619881990199219941996199820002002200420062008

2,580

2,590

2,600

2,610

2,620

TD-80E, OGALLALA AQUIFER

Simulated

Observed

EXPLANATION
Numerical Model 43

Table 13. Comparison of estimated hydraulic conductivity values for the 

model described by Long and others (2003) and the revised model described 

in this report.

[--, not applicable]

Zone 2003 modela Revised model 

described in this report

Deviation from 2003 

model as a percentage

Horizontal hydraulic conductivity layer 1

Zone 1 -- 1.3 --

Zone 1 2 5.4 170

Zone 1 20 26.8 34

Zone 2 .2 .2 0

Zone 2 7.6 8.4 11

Zone 2 23 25.1 9

Zone 3 .9 .4 -56

Zone 3 9.3 2.8 -70

Zone 3 46 28.1 -39

Zone 3 120 84.4 -30

Zone 4 2.5 2.5 0

Zone 5 37 13.3 -64

Horizontal hydraulic conductivity layer 2

Zone 1 5.4 3.8 -30

Zone 2 2.3 2.2 -4

Zone 2 4.7 4.3 -9

Zone 3 1.2 1.2 0

Zone 3 2.4 2.4 0

Zone 3 1.2 .1 -92

Zone 4 .1 .1 0

Zone 5 1.3 1.1 -15

Vertical hydraulic conductivity layer 1

Zone 1 6.6x10-4 4.2x10-4 -37

Vertical hydraulic conductivity layer 2

Zone 1 8.6x10-6 8.8x10-5 923

Zone 2 .72 3.7 414

Zone 3 1.8x10-3 9.2x10-3 411

Zone 4 2.0x10-2 .10 400

Zone 5 2.6x10-3 1.3x10-2 400

a

Long and others (2003).
44 Simulated Groundwater Flow in the Ogallala and Arikaree Aquifers, Rosebud Indian Reservation Area

Figure 22. Hydrographs showing simulated and observed data for Tribal observation wells for calibrated transient model. HYDRAULIC HEAD, IN FEET ABOVE NGVD OF 1929

2,820

2,830

2,840

2,850

2,860

2,870

RST-3,OGALLALA AQUIFER

2,870

2,880

2,890

2,900

2,910

RST-4, OGALLALA AQUIFER

2,820

2,830

2,840

2,850

2,860

RST-5, OGALLALA AQUIFER

2,830

2,840

2,850

2,860

2,870

RST-6, OGALLALA AQUIFER

1978198019821984198619881990199219941996199820002002200420062008

2,815

2,825

2,835

2,845

2,855

RST-7, OGALLALA AQUIFER

197819801982198419861988199019921994

19961998

2000

20022004

20062008

2,820

2,830

2,840

2,850

2,860

RST-8, OGALLALA AQUIFER

CALENDAR YEAR

Simulated

Observed

EXPLANATION
Numerical Model 45

Figure 22. Hydrographs showing simulated and observed data for Tribal observation wells for calibrated transient model.—

Continued

2,810

2,820

2,830

2,840

2,850

RST-9, OGALLALA AQUIFER

2,770

2,780

2,790

2,800

2,810 RST-10, OGALLALA AQUIFER

2,785

2,795

2,,805

2,815

2,825

RST-11, OGALLALA AQUIFER

2,770

2,780

2,790

2,800

2,810

RST-12, OGALLALA AQUIFER

1978198019821984198619881990199219941996199820002002200420062008

2,790

2,800

2,810

2,820

2,830

RST-13, OGALLALA AQUIFER

1978198019821984198619881990199219941996199820002002200420062008

2,575

2,585

2,595

2,605

2,615 RST-15, ARIKAREE AQUIFER

CALENDAR YEAR

HYDRAULIC HEAD, IN FEET ABOVE NGVD OF 1929

Simulated

Observed

EXPLANATION
46 Simulated Groundwater Flow in the Ogallala and Arikaree Aquifers, Rosebud Indian Reservation Area

Figure 22. Hydrographs showing simulated and observed data for Tribal observation wells for calibrated transient model.—

Continued HYDRAULIC HEAD, IN FEET ABOVE NGVD OF 1929

CALENDAR YEAR

2,710

2,720

2,730

2,740

2,750

RST-16, OGALLALA AQUIFER

2,590

2,600

2,610

2,620

2,630

RST 17, OGALLALA AQUIFER

2,650

2,660

2,670

2,680

2,690

RST-18, OGALLALA AQUIFER

2,700

2,710

2,720

2,730

2,740

RST-19, OGALLALA AQUIFER

197819801982198419861988199019921994

19961998

2000

20022004

20062008

2,690

2,700

2,710

2,720

2,730

RST-20, OGALLALA AQUIFER

197819801982198419861988199019921994

19961998

2000

20022004

20062008

2,635

2,645

2,655

2,665

2,675

RST-21, OGALLALA AQUIFER

Simulated

Observed

EXPLANATION
Numerical Model 47

Figure 22. Hydrographs showing simulated and observed data for Tribal observation wells for calibrated transient model.—

Continued HYDRAULIC HEAD, IN FEET ABOVE NGVD OF 1929

CALENDAR YEAR

2,570

2,580

2,590

2,600

2,610

RST-22, OGALLALA AQUIFER

197819801982198419861988199019921994

19961998

2000

20022004

20062008

2,580

2,590

2,600

2,610

2,620

RST-23, OGALLALA AQUIFER

197819801982198419861988199019921994

19961998

2000

20022004

20062008

2,750

2,760

2,770

2,780

2,790

CALENDAR YEAR

RST-27, OGALLALA AQUIFER

Simulated

Observed

EXPLANATION
48 Simulated Groundwater Flow in the Ogallala and Arikaree Aquifers, Rosebud Indian Reservation Area

Figure 23. Hydrographs showing the differences of water levels in wells between results of the calibrated model and the assumed 

potential drought scenario for the 30-year simulation period for selected sites for the Ogallala aquifer. HYDRAULIC HEAD, IN FEET ABOVE NGVD OF 1929

CALENDAR YEAR

EXPLANATION

2,800

2,810

2,820

2,830

2,840 RST-3, OGALLALA AQUIFER

2,870

2,880

2,890

2,900

2,910 RST-4, OGALLALA AQUIFER

2,820

2,830

2,840

2,850

2,860

RST-5, OGALLALA AQUIFER

2,820

2,830

2,840

2,850

2,860 RST-6, OGALLALA AQUIFER

2,790

2,800

2,810

2,820

2,830

RST-7, OGALLALA AQUIFER

2,820

2,830

2,840

2,850

2,860

RST-8, OGALLALA AQUIFER

1978198019821984198619881990199219941996199820002002200420062008

1978

19801982

1984

1986

19881990

1992

19941996

1998

2000

2002

2004

2006

2008

Calibrated model

Drought scenario
Numerical Model 49

Figure 24. Simulated potentiometric surfaces for the calibrated model and the drought scenario at the end of a 

30-year simulation period for the Ogallala aquifer.

2750

2750

2700

2800

2800

2650

2650

2600

2600

2950

2900

2850

3000

2500

2550

2400

2350

2450

3050

2950

2700

2850

2800

2800

2600

3000

2800

2600

25502500

2450

2750

2950

2900

2700

2650

2750

2750

2700

2750

2850

2400

2450

2750

2450

2400

2350

3550

3550

EXPLANATION

Qa

Tw

T.

102

N.

T.

101

N.

T.

100

N.

T.

98

N.

T.

97

N.

T.

96

N.

T.

95

N.

T.

99

N.

R. 33 W. R. 32 W. R. 31 W. R. 30 W. R. 29 W. R. 28 W. R. 27 W. R. 26 W. R. 25 W. R. 79 W.

MELLETTE

COUNTY

BENNETT COUNTY

TODD COUNTY

TODD COUNTY

CHERRY COUNTY

JACKSON COUNTY

TRIPP COUNTY

83

83

18

18

Little

White

Keya Paha

River

River

South

Cr

Cr

Cr

Gray

Beads

Omaha

Rosebud

Phister

S. Ironwood Creek

Creek

Lone Tree

Creek

Creek

Soldier Creek

Eagletail

Sand Creek

Creek

Creek

Creek

Thunder

Creek

White

Rock

Spring

Black

Pipe

Creek

Antelope

Eagle

Oak

Creek

Cut

Meat

Creek

Creek

North

Pine

Branch

Branch

Creek

Creek

Minnechaduza

Dry

Creek

White River

Wood

Okreek Carter

Parmelee Mission Antelope

Rosebud

Blackpipe

St. Francis

Olsonville

Norris

101°15' 101° 100°45' 100°30' 100°15'

43°

43°15'

43°30'

Base from U.S. Geological Survey digital data 1:100,000, 1980, 1982, 1983, 1985

Universal Transverse Mercator projection, zone 14

0 5 10 MILES

0 5 10 KILOMETERS

Ogallala aquifer active cells

Simulated potentiometric contour for the calibrated 

model at the end of the 30-year simulation—Shows 

average altitude at which water level would have 

stood in tightly cased wells. Contour interval is 50 

feet. Datum is NGVD of 1929

Simulated potentiometric contour for the drought 

scenario at the end of the 30-year simulation— 

Shows average altitude at which water level would 

have stood in tightly cased wells. Contour interval is 

50 feet. Datum is NGVD of 1929
50 Simulated Groundwater Flow in the Ogallala and Arikaree Aquifers, Rosebud Indian Reservation Area

Figure 25. Hydrographs showing the differences in water levels in wells between results of the calibrated model and the scenario 

of pumping increased by 50 percent for the 30-year simulation period for selected sites for the Ogallala aquifer.

2,820

2,830

2,840

2,850

2,860

RST-6, OGALLALA AQUIFER

2,790

2,800

2,810

2,820

2,830

RST-7, OGALLALA AQUIFER

2,820

2,830

2,840

2,850

2,860

RST-8, OGALLALA AQUIFER

2,760

2,770

2,780

2,790

2,800

RST-11, OGALLALA AQUIFER

1978198019821984198619881990199219941996199820002002200420062008

2,760

2,770

2,780

2,790

2,800

RST-12, OGALLALA AQUIFER

1978198019821984198619881990199219941996199820002002200420062008

2,790

2,800

2,810

2,820

2,830

RST-13, OGALLALA AQUIFER

HYDRAULIC HEAD, IN FEET ABOVE NGVD OF 1929

CALENDAR YEAR

EXPLANATION

Calibrated model

Increased groundwater withdrawals
Numerical Model 51

Figure 26. Simulated potentiometric surfaces for the calibrated model and the scenario of pumping increased by 

50 percent at the end of a 30-year simulation period for the Ogallala aquifer.

2750

2700

2800

2650

2650

2600

2600

2950

2900

2850

3000

2500

2450

2450

2550

2400

2350

2350

2450

2400

3050

2950

2700

2850

2600

2550

2500

2450

2750 2800 2750

2750

2700

2750

2800

2800

2600

3000

2800

2900

2950

2900

2650

2650

2650

2850

2400

EXPLANATION

Qa

Tw

T.

102

N.

T.

101

N.

T.

100

N.

T.

98

N.

T.

97

N.

T.

96

N.

T.

95

N.

T.

99

N.

R. 33 W. R. 32 W. R. 31 W. R. 30 W. R. 29 W. R. 28 W. R. 27 W. R. 26 W. R. 25 W. R. 79 W.

MELLETTE

COUNTY

BENNETT COUNTY

TODD COUNTY

TODD COUNTY

CHERRY COUNTY

JACKSON COUNTY

TRIPP COUNTY

83

83

18

18

Little

White

Keya Paha

River

River

South

Cr

Cr

Cr

Gray

Beads

Omaha

Rosebud

Phister

S. Ironwood Creek

Creek

Lone Tree

Creek

Creek

Soldier Creek

Eagletail

Sand Creek

Creek

Creek

Creek

Thunder

Creek

White

Rock

Spring

Black

Pipe

Creek

Antelope

Eagle

Oak

Creek

Cut

Meat

Creek

Creek

North

Pine

Branch

Branch

Creek

Creek

Minnechaduza

Dry

Creek

White River

Wood

Okreek Carter

Parmelee Mission Antelope

Rosebud

Blackpipe

St. Francis

Olsonville

Norris

101°15' 101° 100°45' 100°30' 100°15'

43°

43°15'

43°30'

Base from U.S. Geological Survey digital data 1:100,000, 1980, 1982, 1983, 1985

Universal Transverse Mercator projection, zone 14

0 5 10 MILES

0 5 10 KILOMETERS

Ogallala aquifer active cells

Simulated potentiometric contour for the calibrated 

model at the end of the 30-year simulation—Shows 

average altitude at which water level would have 

stood in tightly cased wells. Contour interval is 50 

feet. Datum is NGVD of 1929

Simulated potentiometric contour for the increased 

pumping scenario at the end of the 30-year 

simulation—Shows average altitude at which water 

level would have stood in tightly cased wells. 

Contour interval is 50 feet. Datum is NGVD of 1929

2800

2850
52 Simulated Groundwater Flow in the Ogallala and Arikaree Aquifers, Rosebud Indian Reservation Area

Summary

The Ogallala and Arikaree aquifers are important water 

resources in the Rosebud Indian Reservation area and are 

used extensively for irrigation, municipal, and domestic water 

supplies. Continued or increased withdrawals from the Ogallala and Arikaree aquifers in the Rosebud Indian Reservation 

area have the potential to affect water levels in these aquifers. 

A water-resource tool was needed to evaluate management 

and environmental issues associated with the Ogallala and 

Arikaree aquifers, such as assessing the effects of drought and 

potential increases in groundwater withdrawals. To address 

this need, the U.S. Geological Survey has worked in cooperation with the Rosebud Sioux Tribe to revise and recalibrate a 

previously published three-dimensional, numerical groundwater-flow model for this area by using data from October 

1978 through September 2008. 

The model had two layers to represent the Ogallala 

and Arikaree aquifers. The model grid had 168 rows and 

202 columns, most of which were 1,640 feet (500 meters) 

wide, with narrower rows and columns near large watersupply wells. Data for a 30-year period (water years 1979 

through 2008) were used in steady-state and transient numerical simulations of groundwater flow. Revisions to the model 

include (1) extension of the transient calibration period by 

10 years, (2) the use of inverse modeling for steady-state 

calibration, (3) model calibration to base flow for an additional 

four surface-water drainage basins, (4) improved estimation 

of transient aquifer recharge, (5) improved delineation of 

vegetation types, and (6) reduced cell size near large capacity water-supply wells. In addition, potential future scenarios 

were simulated to assess the potential effects of drought and 

increased groundwater withdrawals.

Recharge to the Ogallala and Arikaree aquifers occurs 

from precipitation on the outcrop areas, and regional flow 

enters the study area from the west. Groundwater originating from precipitation recharge moves from areas of higher 

altitude toward streams that gain flow from the Ogallala and 

Arikaree aquifers. Discharge from the Ogallala and Arikaree aquifers occurs through evapotranspiration, discharge to 

streams and springs, and well withdrawals. Well withdrawals 

in the study area are for irrigation, municipal, domestic, and 

stock use, the largest of which is for irrigation. Evapotranspiration generally occurs in topographically low areas and along 

streams. Maximum evapotranspiration occurs only when the 

water level is at the land surface.

Multiple streamflow measurements were made in the 

study area to obtain information describing stream base flow. 

Average base flow was estimated for six surface-water drainage basins in the study area, including the Little White and 

Keya Paha Rivers, which were estimated to have average base 

flows of 49 and 23 cubic feet per second, respectively. The 

four smaller drainage basins (Cut Meat Creek, Black Pipe 

Creek, Minnechaduza Creek, and Sand Creek) were estimated 

to have a total average base flow of 9.8 cubic feet per second. 

These estimates are inclusive of spring flow along stream 

banks.

Average inflow and outflow rates for water years 1979–

2008 were used in the steady-state simulation, whereas the 

time-varying rates were used in the transient simulation. The 

steady-state model was calibrated to average water levels in 

383 wells and estimated average base-flow rates for 6 surfacewater drainage basins. Inverse modeling techniques were 

used for steady-state model calibration. These methods were 

designed to estimate parameter values that are, statistically, the 

most likely set of values to result in the smallest overall differences between simulated and observed hydraulic heads and 

base-flow discharges. Parameters estimated by this method 

were hydraulic conductivity, recharge, maximum evapotranspiration, riverbed conductance, and spring conductance. 

The average recharge rates used for the steady-state simulation were 2.91 and 1.45 inches per year applied to outcrops 

of the Ogallala and Arikaree aquifers, respectively, for a total 

rate of 255.4 cubic feet per second. Total inflow from model 

boundaries for the steady-state simulation was 12.5 cubic feet 

per second. Discharge rates in cubic feet per second for the 

steady-state simulation were 171.3 for evapotranspiration, 

74.4 for net outflow to streams and springs, 11.6 for well withdrawals, and 9.9 as outflow from model boundaries. Estimated 

horizontal hydraulic conductivity used for the numerical 

model ranged from 0.2 to 84.4 feet per day for the Ogallala 

aquifer and 0.1 to 4.3 feet per day for the Arikaree aquifer. 

A uniform vertical hydraulic conductivity value of 

4.2x10-4 feet per day was estimated for the Ogallala aquifer. 

Vertical hydraulic conductivity was estimated for five zones in 

the Arikaree aquifer and ranged from 8.8x10-5 to 3.7 feet per 

day. 

For the steady-state simulation, the root mean square 

error for simulated hydraulic heads for all wells was 27.3 feet. 

Simulated hydraulic heads were within ±50 feet of observed 

values for 93 percent of the 383 wells. For the transient 

simulation, the difference between the simulated and observed 

means for hydrographs was within ±40 feet for 98 percent of 

44 observation wells. The potentiometric surfaces of the two 

aquifers calculated by the steady-state simulation established 

initial conditions for the transient simulation. A sensitivity 

analysis was used to examine the response of the calibrated 

steady-state model to changes in model parameter values. 

The model was most sensitive to recharge and maximum 

evapotranspiration and least sensitive to riverbed and spring 

conductances.

To simulate a potential future drought scenario, a 

synthetic recharge record was created, the mean of which was 

equal to 64 percent of the average estimated recharge rate 

for the 30-year calibration period. This synthetic recharge 

record was used to simulate the last 20 years of the calibration period under drought conditions. Compared with results 

of the calibrated model, decreases in hydraulic-head values 

for the drought scenario at the end of the simulation period 

were as much as 39 feet for the Ogallala aquifer. To simulate 

the effects of potential increases in pumping, well withdrawal 
References Cited 53

rates were increased by 50 percent from those estimated for 

the 30-year calibration period for the last 20 years of the 

calibration period. Compared with results of the calibrated 

model, decreases in hydraulic-head values for the scenario of 

increased pumping at the end of the simulation period were as 

much as 13 feet for the Ogallala aquifer.

This numerical model is suitable as a tool to help understand the flow system, to help confirm that previous estimates 

of aquifer properties were reasonable, and to estimate aquifer 

properties in areas without data. The model also is useful to 

help assess the effects of drought and increases in pumping 

by simulations of these scenarios, the results of which are not 

precise but may be considered when making water management decisions. Limitations of the model should be taken into 

account when applying the model to water management.

References Cited

Bradley, Edward, 1956, Geology and groundwater resources 

of the Upper Niobrara River Basin, Nebraska and Wyoming: U.S. Geological Survey Water-Supply Paper 1368, 

70 p.

Carter, J.M., 1998, Water resources of Mellette and Todd 

Counties, South Dakota: U.S. Geological Survey WaterResources Investigations Report 98–4146, 68 p.

Doherty, J., 2004, PEST—Model-independent parameter 

estimation user manual (5th ed.): Watermark Numerical 

Computing, variously paged, accessed December 2, 2009, at 

http://www.pesthomepage.org/files/pestman.pdf.

Ellis, M.J., Ficken, J.H., and Adolphson, D.G., 1971, Hydrology of the Rosebud Indian Reservation, South Dakota: 

U.S. Geological Survey Hydrologic Investigations Atlas 

HA–335, 2 sheets, scale 1:100,000.

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.

Fenneman, N.M., 1946, Physical divisions of the United 

States: U.S. Geological Survey map prepared in cooperation with the Physiographic Commission, U.S. Geological 

Survey, scale 1:700,000 (reprinted 1964).

Flint, R.F., 1955, Pleistocene geology of eastern South Dakota: 

U.S. Geological Survey Professional Paper 262, 173 p.

Gutentag, E.D., Heimes, F.J., Krothe, N.C., Luckey, R.R., and 

Weeks, J.B., 1984, Geohydrology of the High Plains aquifer 

in parts of Colorado, Kansas, Nebraska, New Mexico, Oklahoma, South Dakota, Texas, and Wyoming: U.S. Geological 

Survey Professional Paper 1400–B, 63 p.

Harbaugh, A.W., Banta, E.R., Hill, M.C., and McDonald, 

M.G., 2000, MODFLOW-2000, the U.S. Geological Survey 

modular ground-water model—User guide to modularization concepts and the ground-water flow process: U.S. 

Geological Survey Open-File Report 00–92, 121 p.

Jakeman, A.J., and Hornberger, G.M., 1993, How much 

complexity is warranted in a rainfall–runoff model?: Water 

Resources Research, v. 29, no. 8, p. 2,637–2,649.

Kolm, K.E., and Case, H.L., III, 1983, A two-dimensional, 

finite-difference model of the High Plains aquifer in southern South Dakota: U.S. Geological Survey Water-Resources 

Investigations Report 83–4175, 34 p.

Langbein, W.B., 1949, Annual runoff in the United States: 

U.S. Geological Survey Circular 52, 14 p.

Levenberg, K., 1944, A method for the solution of certain 

non-linear problems in least squares: Quarterly of Applied 

Mathematics, v. 2, p. 164–168.

Long, A.J., Putnam, L.D., and Carter, J.M., 2003, Groundwater flow model of the Ogallala and Arikaree aquifers in 

the Rosebud Indian Reservation area, South Dakota: U.S. 

Geological Survey Water-Resources Investigations Report 

03–4043, 69 p. 

Long, A.J., 2009, Hydrograph separation for karst watersheds 

using a two-domain rainfall-discharge model: Journal of 

Hydrology, v. 364, no. 3–4, p. 249–256.

Marquardt, D.W., 1963. An algorithm for least-squares 

estimation of nonlinear parameters: Journal of the Society 

for Industrial and Applied Mathematics, v. 11, no. 2, p. 

431–441.

Maupin, M.A., and Barber, N.L., 2005, Estimated withdrawals from principal aquifers in the United States, 2000: U.S. 

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2010, at http://pubs.er.usgs.gov/usgspubs/cir/cir1279.

McDonald, M.G., and Harbaugh, A.W., 1988, A modular 

three-dimensional finite-difference ground-water flow 

model: U.S. Geological Survey Techniques of WaterResources Investigations, book 6, chap. A1 [variously 

paged].

McGuire, V.L., 2009, Water-level changes in the High 

Plains aquifer, predevelopment to 2007, 2005–06, and 

2006–07: U.S. Geological Survey Scientific Investigations 

Report 2009–5019, 9 p., accessed February 22, 2010, at 

http://pubs.usgs.gov/sir/2009/5019/.

Multi-Resolution Land Characteristics Consortium, 2009, 

National Land Cover Database 2001, accessed July 10, 

2009, at http://www.mrlc.gov/nlcd.php.
54 Simulated Groundwater Flow in the Ogallala and Arikaree Aquifers, Rosebud Indian Reservation Area

National Climatic Data Center, 2010, NOAA Satellite and 

Information Service, accessed February 22, 2010, at

http://www.ncdc.noaa.gov/oa/climate/stationlocator.html.

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Distribution System (SDDS), access May 19, 2010, at

http://ned.usgs.gov/.

Rahn, P.H., and Paul, H.A., 1975, Hydrogeology of a portion 

of the Sand Hills and Ogallala aquifer, South Dakota and 

Nebraska: Ground Water, v. 13, no. 5, p. 428–437.

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

of streamflow, Volume 1, Measurement of stage and |

discharge: U.S. Geological Survey Water-Supply Paper 

2175, 284 p., accessed 24 February 2010 at 

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Springer, R.F., 1974, Soil survey of Todd County, South 

Dakota: U.S. Department of Agriculture, 89 p.

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Geological Survey Topographic Map, scale 1:250,000.

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U.S. Geological Survey database, accessed November 30, 

2009, at http://water.usgs.gov/watuse/.
Appendix 1
56 Simulated Groundwater Flow in the Ogallala and Arikaree Aquifers, Rosebud Indian Reservation Area

Appendix 1. Wells used for estimating potentiometric surfaces of the Ogallala and Arikaree aquifers.

[Hydraulic heads are estimated averages for water years 1979–98. NGVD of 1929, National Geodetic Vertical Datum of 1929. --, not applicable or 

unknown]

Site identification 

number Legal location Aquifer

Land surface altitude (feet above 

NGVD of 1929)

Well depth 

(feet)

Average hydraulic 

head (feet above 

NGVD of 1929)

Observation 

well name

430239100174301 35N25W 5BBAA Ogallala 2,518 72 2,510 --

430200100164801 35N25W 5DDD Ogallala 2,501 100 2,496 --

430242100184801 35N25W 6BBA Arikaree 2,525 100 2,513 --

430151100173901 35N25W 8BB Ogallala 2,513 90 2,496 --

430023100115602 35N25W13DADD2 Ogallala 2,443 160 2,434 --

430002100174801 35N25W20BBBC Ogallala 2,493 47 2,489 --

430003100174802 35N25W20BBBC3 Arikaree 2,493 120 2,488 --

430204100212001 35N26W 3DDAB Arikaree 2,617 120 2,593 --

430237100241201 35N26W 5BA Ogallala 2,635 70 2,603 --

430216100252101 35N26W 6DBBA Arikaree 2,620 132 2,558 --

430127100230601 35N26W 9BDAD Arikaree 2,585 100 2,558 --

430126100222001 35N26W10CBBA2 Ogallala 2,618 82 2,573 --

430126100221901 35N26W10CBBA3 Arikaree 2,617 492 2,569 --

430033100203001 35N26W14DB Ogallala 2,530 28 2,520 --

430040100233901 35N26W17DAB Ogallala 2,583 60 2,576 --

430033100234902 35N26W17DAB2 Arikaree 2,583 103 2,565 --

430006100254301 35N26W19BBAC Ogallala 2,660 100 2,623 --

430236100274201 35N27W 2ABCC Ogallala 2,700 90 2,628 --

430215100273301 35N27W 2DBCC Ogallala 2,695 -- 2,658 --

430245100292801 35N27W 3BBBB Ogallala 2,671 47 2,660 --

430245100292701 35N27W 3BBBB4 Arikaree 2,671 202 2,660 --

430230100320301 35N27W 6AAC Ogallala 2,710 -- 2,679 --

430121100323001 35N27W 7CACB Ogallala 2,724 120 2,698 --

430115100322101 35N27W 7DACC Ogallala 2,731 120 2,705 --

430119100291801 35N27W10CBBB Ogallala 2,717 100 2,686 --

430103100280601 35N27W11CCDC Ogallala 2,682 120 2,651 --

430106100271403 35N27W11DD Ogallala 2,637 80 2,623 --

430106100271402 35N27W11DD2 Arikaree 2,637 120 2,611 --

430139100264401 35N27W12B Ogallala 2,636 85 2,619 --

430057100275401 35N27W14BAAB Ogallala 2,690 84 2,671 RST-21

430022100270901 35N27W14DAA Ogallala 2,676 50 2,666 --

430039100301001 35N27W16BD Ogallala 2,695 55 2,678 --

430039100320801 35N27W18A Ogallala 2,725 55 2,709 --

430000100285401 35N27W22ABBC Arikaree 2,679 75 2,668 --

430154100332601 35N28W 1DC Arikaree 2,683 100 2,673 --

430217100370801 35N28W 4ACCB Arikaree 2,753 140 2,719 --

430122100344501 35N28W11DBBB Ogallala 2,728 94 2,711 RST-20

430613100352901 35N28W14AAAA Arikaree 2,735 120 2,722 --

430055100362702 35N28W15BBBD2 Ogallala 2,754 76 2,744 --

430154100411801 35N29W 2DDDD Ogallala 2,800 44 2,792 RST-10

430156100411901 35N29W 2DDDD2 Ogallala 2,800 37 2,791 --

430238100434801 35N29W 4AA Ogallala 2,830 50 2,810 --

430226100445201 35N29W 4BCCB Arikaree 2,845 113 2,832 --
Appendix 1 57

Appendix 1. Wells used for estimating potentiometric surfaces of the Ogallala and Arikaree aquifers.—Continued

[Hydraulic heads are estimated averages for water years 1979–98. NGVD of 1929, National Geodetic Vertical Datum of 1929. --, not applicable or 

unknown]

Site identification 

number Legal location Aquifer

Land surface altitude (feet above 

NGVD of 1929)

Well depth 

(feet)

Average hydraulic 

head (feet above 

NGVD of 1929)

Observation 

well name

430226100445203 35N29W 4BCCB3 Ogallala 2,845 27 2,829 --

430225100445401 35N29W 5DDDA Arikaree 2,880 135 2,783 --

430148100471001 35N29W 7BBBB Ogallala 2,903 83 2,837 TD-59A

430151100415402 35N29W11ABBB2 Ogallala 2,800 110 2,780 --

430048100450201 35N29W17AACD Arikaree 2,913 190 2,831 --

430014100445401 35N29W17DDDA Arikaree 2,878 140 2,851 --

430100100460501 35N29W18AAAA Ogallala 2,870 84 2,831 RST-9

425957100445601 35N29W20AADD Ogallala 2,890 128 2,804 TD-59B

430212100524001 35N30W 5CA Ogallala 2,828 105 2,809 --

430153100521303 35N30W 5DDCC3 Ogallala 2,842 108 2,822 --

430217100535201 35N30W 6CABA Ogallala 2,873 105 2,834 --

430159100531001 35N30W 6DDDD Ogallala 2,853 84 2,832 RST-5

430113100491601 35N30W11C Arikaree 2,910 260 2,824 --

430139100474801 35N30W12ACBB Ogallala 2,935 160 2,875 --

430037100471601 35N30W13ADD Ogallala 2,895 140 2,785 --

430045100495701 35N30W15ACA Ogallala 2,880 125 2,850 --

430231100591501 35N31W 5AACC Ogallala 2,865 70 2,850 --

430142100580301 35N31W 9AACD Arikaree 2,840 120 2,812 --

430120100574901 35N31W10CBBC Ogallala 2,823 57 2,818 --

430021100543301 35N31W13D Arikaree 2,840 125 2,783 --

430042100565801 35N31W15ACA Ogallala 2,822 75 2,815 --

430017100595101 35N31W17CCDA Ogallala 2,896 62 2,893 RST-4

430113101062401 35N32W 8D Ogallala 2,980 80 2,975 --

430152101054803 35N32W 9BABB3 Ogallala 2,935 67 2,928 --

430153101054902 35N32W 9BABB5 Arikaree 2,938 452 2,931 --

430047101025001 35N32W14A Ogallala 2,982 105 2,913 --

430028101111701 35N33W15DB Ogallala 3,060 90 3,035 --

425956101134503 35N33W20ABCC3 Ogallala 3,050 165 3,032 --

430727100170304 36N25W 5DBD Arikaree 2,440 45 2,428 --

430704100145901 36N25W10BABB Ogallala 2,442 30 2,421 --

430348100172001 36N25W29CDAC Ogallala 2,573 120 2,526 --

430326100185001 36N25W31ABC Arikaree 2,597 100 2,550 --

430315100184301 36N25W31BDCB Ogallala 2,552 70 2,530 --

430331100153301 36N25W33AA Ogallala 2,585 70 2,514 --

430700100225701 36N26W 9AB Arikaree 2,505 120 2,498 --

430607100212101 36N26W15AAAB Arikaree 2,505 100 2,448 --

430528100242001 36N26W17CDD Arikaree 2,554 50 2,534 --

430454100255101 36N26W19BBC Ogallala 2,650 120 2,608 --

430455100241301 36N26W20CAD Arikaree 2,537 140 2,525 --

430515100225001 36N26W21AAB Ogallala 2,585 120 2,543 --

430424100214301 36N26W27ABBB Arikaree 2,588 130 2,546 --

430310100245501 36N26W31ADDD Ogallala 2,620 125 2,594 TD-80E

430335100241401 36N26W32BBAA Ogallala 2,619 78 2,589 RST-22
58 Simulated Groundwater Flow in the Ogallala and Arikaree Aquifers, Rosebud Indian Reservation Area

Appendix 1. Wells used for estimating potentiometric surfaces of the Ogallala and Arikaree aquifers.—Continued

[Hydraulic heads are estimated averages for water years 1979–98. NGVD of 1929, National Geodetic Vertical Datum of 1929. --, not applicable or 

unknown]

Site identification 

number Legal location Aquifer

Land surface altitude (feet above 

NGVD of 1929)

Well depth 

(feet)

Average hydraulic 

head (feet above 

NGVD of 1929)

Observation 

well name

430246100222302 36N26W34CCC2 Ogallala 2,634 110 2,607 --

430727100262801 36N27W 1 Arikaree 2,650 128 2,597 --

430728100135801 36N27W 1BDDD Ogallala 2,627 58 2,600 RST-23

430721100290001 36N27W 3CA Ogallala 2,663 150 2,602 --

430705100304701 36N27W 5DDD Ogallala 2,600 120 2,579 --

430512100291801 36N27W15CC Ogallala 2,698 150 2,622 --

430458100300901 36N27W21BDDB Ogallala 2,664 90 2,613 --

430451100290001 36N27W22CDBA Arikaree 2,638 75 2,628 --

430410100261701 36N27W25ADBB Arikaree 2,658 205 2,614 --

430412100323001 36N27W30BDA Arikaree 2,693 140 2,673 --

430245100272401 36N27W35DCD Arikaree 2,673 144 2,647 --

430737100350602 36N28W 2BDAC2 Ogallala 2,773 167 2,677 --

430719101380501 36N28W 5DACC Ogallala 2,818 140 2,783 --

430604100390801 36N28W 7DDB Ogallala 2,829 214 2,793 --

430649100364801 36N28W 9ADDA Ogallala 2,805 70 2,764 --

430701100363001 36N28W10BBBB Ogallala 2,823 183 2,750 TD-76J

430700100344501 36N28W11ABB Ogallala 2,807 140 2,707 --

430702100330501 36N28W12AABA Ogallala 2,806 215 2,660 RST-18

430618100330301 36N28W12DD Ogallala 2,675 20 2,669 --

430614100362503 36N28W15BABB3 Ogallala 2,778 75 2,753 --

430601100364501 36N28W16ABCA Ogallala 2,805 40 2,779 --

430454100341801 36N28W23DAAC Arikaree 2,730 120 2,712 --

430515100331201 36N28W24AAA Ogallala 2,685 140 2,665 --

430448100332401 36N28W24ACA Arikaree 2,655 40 2,645 --

430406100380701 36N28W29ACDC Ogallala 2,771 40 2,756 --

430403100395001 36N28W30BCDD Ogallala 2,820 100 2,801 --

430348100390401 36N28W30DDAB Ogallala 2,792 100 2,773 --

430314100392301 36N28W31ACDC Ogallala 2,839 95 2,819 --

430243100371701 36N28W33BDDD Ogallala 2,753 75 2,723 RST-19

430712100421301 36N29W 2CDCC Ogallala 2,850 200 2,804 RST-12

430714100445001 36N29W 4CCBC Ogallala 2,853 150 2,816 --

430624100461601 36N29W 7DDB Ogallala 2,925 190 2,890 --

430659100434901 36N29W 9AA Ogallala 2,845 200 2,778 --

430629100434401 36N29W 9DAD Ogallala 2,885 209 2,817 --

430530100422501 36N29W14CDAB Ogallala 2,893 200 2,811 RST-11

430522100411902 36N29W14DDDD2 Ogallala 2,884 225 2,815 --

430558100430301 36N29W15ACBB Ogallala 2,884 160 2,866 --

430609100434201 36N29W16AAAA Ogallala 2,863 222 2,822 TD-76F

430604100445201 36N29W17AADD R Ogallala 2,905 243 2,823 --

430603100460501 36N29W18AADD Ogallala 2,940 123 2,850 --

430450100453701 36N29W20CA Ogallala 2,868 140 2,845 --

430508100431901 36N29W22BBDD Ogallala 2,911 230 2,831 --

430415100451401 36N29W29ACAA Ogallala 2,870 134 2,851 RST-7
Appendix 1 59

Appendix 1. Wells used for estimating potentiometric surfaces of the Ogallala and Arikaree aquifers.—Continued

[Hydraulic heads are estimated averages for water years 1979–98. NGVD of 1929, National Geodetic Vertical Datum of 1929. --, not applicable or 

unknown]

Site identification 

number Legal location Aquifer

Land surface altitude (feet above 

NGVD of 1929)

Well depth 

(feet)

Average hydraulic 

head (feet above 

NGVD of 1929)

Observation 

well name

430305100455401 36N29W32CB Ogallala 2,835 60 2,823 --

430252100431301 36N29W34CD Ogallala 2,804 100 2,794 --

430302100412001 36N29W35DAD Ogallala 2,834 45 2,819 --

430723100512101 36N30W 4DBCB Ogallala 2,978 235 2,872 --

430627100532601 36N30W 7D Arikaree 2,960 187 2,856 --

430652100484001 36N30W11ADBB Ogallala 2,949 300 2,851 --

430615100472701 36N30W12DDCD Ogallala 2,960 285 2,827 --

430610100481701 36N30W13BBBB Ogallala 2,916 225 2,843 TD-76E

430518100533701 36N30W19ABB Ogallala 2,902 145 2,855 --

430501100504901 36N30W22CBBB Ogallala 2,888 137 2,858 RST-6

430507100483701 36N30W23ADBB Ogallala 2,934 217 2,848 --

430342100482901 36N30W26DDDB Ogallala 2,851 50 2,832 --

430250100532701 36N30W31DCDA Ogallala 2,868 50 2,849 --

430327100512301 36N30W33BADD Ogallala 2,945 180 2,854 --

430334100515201 36N30W33BBB Ogallala 2,896 110 2,843 --

430254100515001 36N30W33CCBD Ogallala 2,879 50 2,856 --

430301100492101 36N30W35CBCC Arikaree 2,917 179 2,843 --

430258100471401 36N30W36DDDA Ogallala 2,885 123 2,836 RST-8

430721100563001 36N31W 2CBCD Ogallala 2,934 200 2,785 --

430630100565401 36N31W10DACD3 Arikaree 2,958 305 2,736 --

430613100544901 36N31W12DCCD Arikaree 2,899 194 2,843 --

430613101561701 36N31W14BAAA Ogallala 2,955 160 2,816 TD-79B

430541100555501 36N31W14DB Ogallala 2,970 140 2,871 --

430555100570301 36N31W15ACAC Ogallala 3,005 310 2,916 --

430603101003401 36N31W18ABDD Ogallala 2,877 98 2,839 --

430309100570901 36N31W34DBBC Ogallala 2,920 91 2,865 RST-3

430650101021001 36N32W 1DCDC Arikaree 2,623 60 2,614 --

430721101032801 36N32W 2C Arikaree 2,660 180 2,667 --

430712101042801 36N32W 3CD Arikaree 2,686 118 2,631 --

430619101020501 36N32W12CD2 Arikaree 2,895 335 2,734 --

430612101014401 36N32W12DD Arikaree 2,842 340 2,674 --

430537101062801 36N32W17DBD Arikaree 2,860 205 2,820 --

430458101042001 36N32W22CADA Ogallala 2,850 40 2,821 --

430426101020201 36N32W25BAA Ogallala 2,845 55 2,811 --

430340101012301 36N32W25DDDD Ogallala 2,841 125 2,834 TD-80B

431500101133301 36N33W21BBC Arikaree 2,985 160 2,860 --

431236100172601 37N25W 4BCCA Ogallala 2,467 100 2,386 --

431254100191001 37N25W 6ABA Arikaree 2,410 120 2,373 --

431211100194502 37N25W 6CCC2 Arikaree 2,369 80 2,347 --

430908100175801 37N25W29ACDD Arikaree 2,374 60 2,360 --

430757100183301 37N25W32CCAB Arikaree 2,423 124 2,396 --

431245100210801 37N26W 2ADAA Arikaree 2,383 109 2,351 --

431215100225801 37N26W 3CDA Arikaree 2,444 95 2,401 --
60 Simulated Groundwater Flow in the Ogallala and Arikaree Aquifers, Rosebud Indian Reservation Area

Appendix 1. Wells used for estimating potentiometric surfaces of the Ogallala and Arikaree aquifers.—Continued

[Hydraulic heads are estimated averages for water years 1979–98. NGVD of 1929, National Geodetic Vertical Datum of 1929. --, not applicable or 

unknown]

Site identification 

number Legal location Aquifer

Land surface altitude (feet above 

NGVD of 1929)

Well depth 

(feet)

Average hydraulic 

head (feet above 

NGVD of 1929)

Observation 

well name

431020100243501 37N26W16CCBB Arikaree 2,530 -- 2,523 TD-79A

430932100262401 37N26W19DCC Ogallala 2,655 160 2,584 --

430931100251801 37N26W20CDD Arikaree 2,605 140 2,557 --

430932100211701 37N26W23DDCD Arikaree 2,538 140 2,495 --

431019100200001 37N26W24AAA Arikaree 2,471 110 2,453 --

430953100200001 37N26W24DAA Arikaree 2,451 90 2,418 --

430858100202301 37N26W25DBBD Arikaree 2,565 140 2,522 --

430851100210801 37N26W26DADD Arikaree 2,576 140 2,533 --

430756100231601 37N26W34CCAA Arikaree 2,540 140 2,521 --

430803100212801 37N26W35DBDA Arikaree 2,554 140 2,511 --

431212100280601 37N27W 1CC Arikaree 2,474 120 2,451 --

431245100320601 37N27W 5A Arikaree 2,593 60 2,582 --

431126100321001 37N27W 8D Arikaree 2,553 100 2,537 --

431139100311501 37N27W 9CAAA Arikaree 2,540 120 2,526 --

431050100274501 37N27W13BDD Arikaree 2,530 140 2,472 --

431051100293101 37N27W15ADD Arikaree 2,518 150 2,466 --

431027100333001 37N27W18DDAB Ogallala 2,609 53 2,605 RST-17

431000100325101 37N27W20BCD Arikaree 2,620 80 2,609 --

430938100273701 37N27W24DCB Arikaree 2,595 165 2,548 --

430926100290301 37N27W26BAB Arikaree 2,564 250 2,442 --

430909100333501 37N27W30BDDA Ogallala 2,722 150 2,662 --

430817100312001 37N27W33BD Arikaree 2,620 120 2,604 --

431159100412102 37N28W 7BBBC2 Arikaree 2,793 243 2,718 --

431159100412103 37N28W 7BBBC3 Ogallala 2,793 98 2,716 --

431021100384701 37N28W16CCDD Ogallala 2,744 80 2,714 --

430956100402901 37N28W19ACDD Ogallala 2,800 120 2,773 --

430932100390001 37N28W21CCCC Ogallala 2,772 163 2,727 TD-76H

430839100373801 37N28W27CCCC Ogallala 2,805 182 2,727 TD-76I

430907100401001 37N28W30ADDA Ogallala 2,757 80 2,742 --

430922100410302 37N28W30BBAA2 Arikaree 2,818 321 2,753 --

430842100411301 37N28W30CCCB Ogallala 2,770 184 2,745 TD-76G

430820100371401 37N28W34ABDA Ogallala 2,783 171 2,725 RST-16

430821100373401 37N28W34BCAB Arikaree 2,808 200 2,734 --

430809100372401 37N28W34BDA (2) Ogallala 2,800 171 2,740 --

431212100472901 37N29W 6DDBD Ogallala 2,868 237 2,740 --

431149100462301 37N29W 8AADC Arikaree 2,810 -- 2,740 --

431138100441601 37N29W10DBBB Ogallala 2,818 150 2,756 --

431141100422501 37N29W12BCDD Ogallala 2,825 150 2,762 --

431211100194502 37N25W 6CCC2 Arikaree 2,369 80 2,347 --

430908100175801 37N25W29ACDD Arikaree 2,374 60 2,360 --

430757100183301 37N25W32CCAB Arikaree 2,423 124 2,396 --

431245100210801 37N26W 2ADAA Arikaree 2,383 109 2,351 --

431133100402201 37N29W13CBCD Ogallala 2,796 150 2,732 --
Appendix 1 61

Appendix 1. Wells used for estimating potentiometric surfaces of the Ogallala and Arikaree aquifers.—Continued

[Hydraulic heads are estimated averages for water years 1979–98. NGVD of 1929, National Geodetic Vertical Datum of 1929. --, not applicable or 

unknown]

Site identification 

number Legal location Aquifer

Land surface altitude (feet above 

NGVD of 1929)

Well depth 

(feet)

Average hydraulic 

head (feet above 

NGVD of 1929)

Observation 

well name

431109100445901 37N29W16AAAA Ogallala 2,852 184 2,754 TD-76A

431100100461601 37N29W17AACD Ogallala 2,845 180 2,768 --

430959100444001 37N29W22CCCC Arikaree 2,882 265 2,781 TD-80C

430920100444801 37N29W27BBCA Ogallala 2,877 190 2,810 --

430852100435001 37N29W27DACD Ogallala 2,825 180 2,768 --

430909100452701 37N29W28ACBC Ogallala 2,880 150 2,803 --

430840100445601 37N29W28DDDD Ogallala 2,858 195 2,791 TD-76D

430924100460601 37N29W29AAAA Ogallala 2,868 204 2,790 TD-76B

430836100464301 37N29W29CDDD Ogallala 2,870 88 2,801 --

430755100582301 37N29W31DACC Ogallala 2,921 275 2,815 RST-13

430748100455601 37N29W33CCCC Ogallala 2,909 203 2,817 TD-76C

431238100490301 37N30W 1ACB Arikaree 2,740 220 2,694 --

431250100530101 37N30W 4BAA Arikaree 2,842 265 2,717 --

431122100551202 37N30W 7CDBA2 Arikaree 2,770 187 2,604 --

431127100532801 37N30W 8DACC Ogallala 2,880 150 2,759 RST-27

431033100493201 37N30W13CBCD Ogallala 2,783 60 2,766 --

431022100542301 37N30W17CCCB Arikaree 2,995 386 2,789 --

430910100490201 37N30W25ACBC Ogallala 2,899 165 2,882 --

430912100542301 37N30W29BCBB Ogallala 2,997 216 2,812 --

430848100544001 37N30W30DDBC Ogallala 2,980 272 2,778 --

430824100522501 37N30W33ABD Arikaree 2,985 265 2,839 --

430800100491801 37N30W36ADCA Arikaree 2,935 320 2,825 --

431234100574401 37N31W 3ADAC Arikaree 2,512 42 2,506 --

431131100580701 37N31W10DBBB Arikaree 2,530 55 2,498 --

430920100581201 37N31W22ABCD2 Arikaree 2,943 430 2,639 --

430838100561701 37N31W25CC Arikaree 3,015 370 2,802 --

430845100571903 37N31W26C3 Arikaree 3,017 350 2,737 --

430807100591001 37N31W33DAA Arikaree 3,037 445 2,781 --

430831100580301 37N31W34ABAC Ogallala 2,970 295 2,777 --

431200101034801 37N32W11ABA Ogallala 3,060 245 2,876 --

431030101031201 37N32W13CAD Arikaree 2,970 325 2,792 --

430907101073801 37N32W29ACB Ogallala 2,910 165 2,882 --

431222101093501 37N33W 1DAA Ogallala 3,104 285 3,009 --

431148101165001 37N33W 7ABD Ogallala 3,018 260 2,947 --

431156101105801 37N33W11AAB Ogallala 3,153 305 3,032 --

431018101132301 37N33W16DCDC Ogallala 3,023 270 2,955 --

431018101152001 37N33W17CCCC Ogallala 2,998 181 2,930 BT-76C

430929101104202 37N33W26AAAA2 Arikaree 2,953 395 2,876 --

430929101104203 37N33W26AAAA3 Ogallala 2,953 236 2,876 --

431432101123401 37N33W27BAA Ogallala 2,978 120 2,918 --

430836101152201 37N33W32BBBB Ogallala 2,960 185 2,895 --

430825101151801 37N33W32BBBB2 Ogallala 2,960 143 2,902 BT-80E

431250101163701 37N34W 1AAAA Ogallala 3,113 245 2,960 --
62 Simulated Groundwater Flow in the Ogallala and Arikaree Aquifers, Rosebud Indian Reservation Area

Appendix 1. Wells used for estimating potentiometric surfaces of the Ogallala and Arikaree aquifers.—Continued

[Hydraulic heads are estimated averages for water years 1979–98. NGVD of 1929, National Geodetic Vertical Datum of 1929. --, not applicable or 

unknown]

Site identification 

number Legal location Aquifer

Land surface altitude (feet above 

NGVD of 1929)

Well depth 

(feet)

Average hydraulic 

head (feet above 

NGVD of 1929)

Observation 

well name

431540100154501 38N25W15DCCB Ogallala 2,467 110 2,406 --

431509100185901 38N25W19ADCC Ogallala 2,530 80 2,504 --

431430100195901 38N25W30BCBB Arikaree 2,483 144 2,458 TD-80D

431311100193201 38N25W31CDBA Arikaree 2,426 56 2,414 --

431327100164501 38N25W33ACD Ogallala 2,475 24 2,466 --

431637100264101 38N26W 7CDB Arikaree 2,513 90 2,486 --

431716100212001 38N26W11AAB Ogallala 2,651 160 2,601 --

431554100203301 38N26W13BCCA Arikaree 2,608 230 2,505 --

431532100200101 38N26W24AAAB Ogallala 2,503 85 2,467 --

431413100244901 38N26W29DAA Arikaree 2,440 90 2,418 --

431356100255401 38N26W30DAD Arikaree 2,420 90 2,388 --

431340100253901 38N26W32BBD Arikaree 2,452 85 2,437 --

431328100240901 38N26W33BDD Arikaree 2,424 70 2,413 --

431308100223101 38N26W34DDB Arikaree 2,417 100 2,395 --

431323100213501 38N26W35DBBA Arikaree 2,403 100 2,341 --

431736100293201 38N27W 3DAD Arikaree 2,526 100 2,474 --

431808100312801 38N27W 4BAB Arikaree 2,550 100 2,489 --

431757100323302 38N27W 5BDAB Arikaree 2,522 100 2,497 --

431650100330701 38N27W 7DAAB Arikaree 2,477 -- 2,468 --

431548100314401 38N27W16CBCD Arikaree 2,484 90 2,453 --

431440100275301 38N27W25BABA Arikaree 2,448 100 2,416 --

431430100320101 38N27W28B Arikaree 2,518 110 2,507 --

431337100312101 38N27W33BDA Arikaree 2,570 130 2,541 --

431539100352401 38N28W13CCCC Arikaree 2,577 -- 2,539 --

431625100361301 38N28W14BAAB Arikaree 2,589 115 2,529 --

431615100390701 38N28W17AADD Arikaree 2,664 -- 2,610 --

431625100411801 38N28W18BBBA Arikaree 2,596 -- 2,587 --

431512100402501 38N28W19ADCD Arikaree 2,673 -- 2,639 --

431714100364101 38N28W20AAAD Ogallala 2,700 -- 2,646 --

431506100363601 38N28W23CBBB Arikaree 2,635 -- 2,627 --

431430100371601 38N28W27ACB Arikaree 2,768 220 2,724 --

431427100375201 38N28W28ADAA Ogallala 2,781 -- 2,729 --

431354100375201 38N28W28DDDD Ogallala 2,781 -- 2,750 --

431347100404901 38N28W31ABBB Arikaree 2,666 120 2,645 --

431342100344101 38N28W36ABCB Arikaree 2,620 73 2,609 RST-15

431551100441601 38N29W15DBCD Arikaree 2,696 -- 2,699 --

431536100472201 38N29W17BCDA Arikaree 2,687 100 2,670 --

431502100443801 38N29W22CAC Arikaree 2,730 160 2,686 --

431435100414101 38N29W25AACB Ogallala 2,663 -- 2,647 --

431424100430601 38N29W26ACB Arikaree 2,750 220 2,671 --

431340100430401 38N29W35ACBB Arikaree 2,803 370 2,708 --

431809100483401 38N30W 1AAAA Arikaree 2,763 180 2,626 --

431740100502201 38N30W 2CAA Arikaree 2,640 265 2,492 --
Appendix 1 63

Appendix 1. Wells used for estimating potentiometric surfaces of the Ogallala and Arikaree aquifers.—Continued

[Hydraulic heads are estimated averages for water years 1979–98. NGVD of 1929, National Geodetic Vertical Datum of 1929. --, not applicable or 

unknown]

Site identification 

number Legal location Aquifer

Land surface altitude (feet above 

NGVD of 1929)

Well depth 

(feet)

Average hydraulic 

head (feet above 

NGVD of 1929)

Observation 

well name

431610100484701 38N30W13ADBB Arikaree 2,645 119 2,632 --

431537100504701 38N30W14CCCA Arikaree 2,723 280 2,639 --

431601100514301 38N30W15BDC Arikaree 2,650 158 2,650 --

431612100551201 38N30W18BADB Arikaree 2,550 245 2,416 --

431515100501701 38N30W23ACBC Arikaree 2,720 258 2,657 --

431255100545701 38N30W31DCCD Arikaree 2,872 250 2,701 --

431315100541301 38N30W32CBD Arikaree 2,887 265 2,736 --

431318100532301 38N30W32DAAB Ogallala 2,838 47 2,818 --

431340100521405 38N30W33AA5 Arikaree 2,840 238 2,624 --

431335100511101 38N30W34A Arikaree 2,600 -- 2,573 --

431252100501801 38N30W35BDDB Arikaree 2,708 219 2,605 --

431744100561401 38N31W 1BACB2 Arikaree 2,600 160 2,502 --

431744100583601 38N31W 3ABAB Arikaree 2,692 200 2,601 --

431733100585701 38N31W 4DABD2 Arikaree 2,725 226 2,656 --

431623101010501 38N31W 8CCC Arikaree 2,787 93 2,732 --

431654100574302 38N31W10ADAC2 Arikaree 2,698 210 2,606 --

431630100570201 38N31W11CDAA Arikaree 2,652 240 2,553 --

431550100590501 38N31W16CABD (2) Ogallala 2,747 20 2,743 --

431520100593601 38N31W16DBAA Arikaree 2,710 128 2,688 --

431551101003901 38N31W17CAA Arikaree 2,880 180 2,878 --

431501101005701 38N31W20CBAA Arikaree 2,837 140 2,827 --

431526100563202 38N31W23AAAB2 R Arikaree 2,443 60 2,431 --

431508100562101 38N31W24BDAD R Arikaree 2,605 262 2,505 --

431427100561201 38N31W25BBAC Arikaree 2,722 360 2,563 --

431259100574401 38N31W34DDAC Arikaree 2,502 85 2,477 --

431338100570901 38N31W35BA Arikaree 2,485 60 2,476 --

431738103035702 38N32W 1BAAC Arikaree 2,750 262 2,671 --

431740101044601 38N32W 3ADDD Arikaree 2,750 205 2,681 --

431637101084802 38N32W 7DCAB2 Arikaree 2,890 152 2,841 --

431639101043102 38N32W11CBD2 Arikaree 2,785 225 2,716 --

431554101044501 38N32W15DAAA Arikaree 2,805 90 2,782 --

431533101080501 38N32W17CCD Arikaree 3,059 154 2,907 --

431303101075401 38N32W32CDB Arikaree 3,032 285 2,926 --

431625101103001 38N33W12CCDC Arikaree 2,943 150 2,931 --

431843100263301 39N26W31BDA Arikaree 2,600 140 2,543 --

431830100250201 39N26W32DCDA Arikaree 2,533 153 2,457 --

432242100281201 39N27W 1CCB Arikaree 2,520 80 2,479 --

432316100305801 39N27W 3BBD Arikaree 2,500 65 2,469 --

432205100294301 39N27W10DABB Arikaree 2,513 75 2,482 --

432033100305601 39N27W21ADDA Arikaree 2,754 220 2,583 --

432009100290301 39N27W23CDBA Arikaree 2,651 130 2,610 --

431937100320101 39N27W29ADBD Arikaree 2,676 130 2,645 --

431815100341801 39N27W31CCC Arikaree 2,537 160 2,477 --

431818100324201 39N27W32CDCB2 Arikaree 2,544 90 2,513 --
64 Simulated Groundwater Flow in the Ogallala and Arikaree Aquifers, Rosebud Indian Reservation Area

Appendix 1. Wells used for estimating potentiometric surfaces of the Ogallala and Arikaree aquifers.—Continued

[Hydraulic heads are estimated averages for water years 1979–98. NGVD of 1929, National Geodetic Vertical Datum of 1929. --, not applicable or 

unknown]

Site identification 

number Legal location Aquifer

Land surface altitude (feet above 

NGVD of 1929)

Well depth 

(feet)

Average hydraulic 

head (feet above 

NGVD of 1929)

Observation 

well name

431814100302602 39N27W34CCDC2 Arikaree 2,562 80 2,536 --

431903100282002 39N27W35AAAB2 Arikaree 2,598 91 2,552 --

432150100381701 39N28W 9DCA Arikaree 2,518 68 2,506 --

432203100361301 39N28W11CAA Arikaree 2,535 160 2,510 --

432117100371601 39N28W15ACC Arikaree 2,585 160 2,525 --

432108100400001 39N28W17CBD Arikaree 2,683 210 2,616 --

432003100352501 39N28W24CC Arikaree 2,675 150 2,615 --

431907100350201 39N28W25CCD Arikaree 2,565 150 2,505 --

431947100354001 39N28W26AADB Arikaree 2,628 150 2,568 --

431927100381501 39N28W28DBAA Arikaree 2,628 140 2,599 --

431949100392901 39N28W29ABAD Arikaree 2,634 150 2,625 --

431933100412101 39N28W30BCDB Arikaree 2,622 150 2,603 --

431912100410501 39N28W30CDBD Arikaree 2,601 150 2,587 --

431812100383901 39N28W33CDD Arikaree 2,563 140 2,521 --

432049100415301 39N29W13CC Arikaree 2,640 200 2,585 --

432025100434001 39N29W23BCD Arikaree 2,500 112 2,469 --

431830100450901 39N29W33DA Arikaree 2,657 140 2,629 --

431822100424301 39N29W35DDAB Arikaree 2,681 -- 2,648 --

431813100413101 39N29W36DDDC Arikaree 2,645 220 2,597 --

432244100594502 39N31W 4CBDB2 Arikaree 2,467 60 2,449 --

432149101005001 39N31W 8CACB Arikaree 2,653 274 2,517 --

432020101010901 39N31W19ACDA2 Arikaree 2,625 300 2,545 --

431903100561701 39N31W25CCCA Arikaree 2,558 170 2,471 --

431933101010501 39N31W29BCB Arikaree 2,640 240 2,586 --

431823101005201 39N31W32CBDB Arikaree 2,685 198 2,646 --

431813100571001 39N31W35CDBD Arikaree 2,620 200 2,534 --

432310101045501 39N32W 3AAAA Arikaree 2,610 125 2,578 TD-80A

432205101032201 39N32W11ACDA Arikaree 2,595 125 2,585 --

432131101034001 39N32W14AAA Arikaree 2,634 125 2,600 --

432131101053001 39N32W15BAB Arikaree 2,678 200 2,639 --

431922101032201 39N32W25CBAB Arikaree 2,705 180 2,626 --

431913101084001 39N32W30DBDC Arikaree 2,820 138 2,768 --

431820101045002 39N32W34DADC2 Arikaree 2,781 300 2,646 --

432044101115201 39N33W15DDDD Arikaree 2,800 360 2,764 TD-79D

432416100315601 40N27W32AAA Arikaree 2,478 16 2,470 --

432540101092202 40N32W19BCC2 Arikaree 2,595 100 2,570 --

432515101071701 40N32W20DDBB Arikaree 2,597 220 2,586 --

432554101065601 40N32W21BBBB Arikaree 2,576 163 2,561 MT-78A

432530101024801 40N32W24CBB Arikaree 2,568 152 2,543 --

432453101075601 40N32W29BCAB Arikaree 2,618 240 2,600 --

432654101130401 40N33W 9DDDA Arikaree 2,570 120 2,516 --

432545101102701 40N33W24BBDD Arikaree 2,548 108 2,523 --

432446101131104 40N33W28AD Arikaree 2,740 110 2,686 --

432407101131201 40N33W33AAB Arikaree 2,742 225 2,686 --
Publishing support provided by: 

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For more information concerning this publication, contact:

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1608 Mt. View Rd.

Rapid City, South Dakota 57702

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Or visit the South Dakota Water Science Center Web site at:

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A.J. Long and L.D. Putnam—Simulated Groundwater Flow in the Ogallala and Arikaree Aquifers, Rosebud Indian Reservation Area—Scientific Investigations Report 2010–5105