EFFECTS OF FUTURE GROUND-WATER PUMPAGE

ON THE HIGH PLAINS AQUIFER IN PARTS OF

COLORADO, KANSAS, NEBRASKA, NEW MEXICO,

OKLAHOMA, SOUTH DAKOTA, TEXAS, AND WYOMING

J s.-*'

r

WYOMING

i .

COLORADO

NEW MEXIO

u,s* GEOtocsiCAL SURVEY PROFESSIONAL PAPER i40o~E
Effects of Future Ground-Water Pumpage 

On the High Plains Aquifer in Parts of 

Colorado, Kansas, Nebraska, New Mexico, 

Oklahoma, South Dakota, Texas, and Wyoming

By RICHARD R. LUCKEY, EDWIN D. GUTENTAG, FREDERICK J. HEIMES, and 

JOHN B. WEEKS

REGIONAL AQUIFER-SYSTEM ANALYSIS

U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1400-E

UNITED STATES GOVERNMENT PRINTING OFFICE, W AS HINGTON : 1 988
DEPARTMENT OF THE INTERIOR 

DONALD PAUL HODEL, Secretary

U.S. GEOLOGICAL SURVEY 

Dallas L. Peck, Director

Library of Congress Cataloging-in-Publication Data

Effects of future ground-water pumpage on the High Plains aquifer in parts of Colorado, Kansas, 

Nebraska, New Mexico, Oklahoma, South Dakota, Texas, and Wyoming.

(Regional aquifer-system analysis) (Geological Survey professional paper ; 1400-E)

Bibliography: p.

Supt. of Docs, no.: I 19.16:1400-E

1. High Plains Aquifer. 2. Water consumption Great Plains. 3. Water suppty Great Plains. I. Luckey, 

Richard R. II. Series. III. Series: Geological Survey professional paper ; 1400-E. 

GB1199.3.G74E34 1988 553.7'9'0978 87-600004

For sale by the

Books and Open-File Reports Section

U.S. Geological Survey

Federal Center

Box 25425 

Denver, CO 80225
FOREWORD

THE REGIONAL AQUIFER-SYSTEM ANALYSIS PROGRAM

The Regional Aquifer-System Analysis (RASA) Program was started in 

1978 following a congressional mandate to develop quantitative appraisals of 

the major ground-water systems of the United States. The RASA Program 

represents a systematic effort to study a number of the Nation's most 

important aquifer systems, which in aggregate underlie much of the country 

and which represent an important component of the Nation's total water 

supply. In general, the boundaries of these studies are identified by the 

hydrologic extent of each system and accordingly transcend the political 

subdivisions to which investigations have often arbitrarily been limited in the 

past. The broad objective for each study is to assemble geologic, hydrologic, 

and geochemical information, to analyze and develop an understanding of the 

system, and to develop predictive capabilities that will contribute to the 

effective management of the system. The use of computer simulation is an 

important element of the RASA studies, both to develop an understanding of 

the natural, undisturbed hydrologic system and the changes brought about in 

it by human activities, and to provide a means of predicting the regional 

effects of future pumping or other stresses.

The final interpretive results of the RASA Program are presented in a series 

of U.S. Geological Survey Professional Papers that describe the geology, 

hydrology, and geochemistry of each regional aquifer system. Each study 

within the RASA Program is assigned a single Professional Paper number, 

and where the volume of interpretive material warrants, separate topical 

chapters that consider the principal elements of the investigation may be 

published. The series of RASA interpretive reports begins with Professional 

Paper 1400 and thereafter will continue in numerical sequence as the interpretive products of subsequent studies become available.

Dallas L. Peck 

Director

PREFACE

The Regional Aquifer-System Analysis of the High Plains was conducted 

by U.S. Geological Survey personnel in each of the eight States in the High 

Plains Colorado, Kansas, Nebraska, New Mexico, Oklahoma, South Dakota, 

Texas, and Wyoming. To provide assistance, technical support, and additional 

information, contracts were awarded to the Kansas Geological Survey, New 

Mexico Natural Resources Department, Oklahoma Water Resources Board, 

and Texas Department of Water Resources. In addition, valuable information 

was provided by many other State and local agencies throughout the High 

Plains. Their contributions are an integral part of this investigation without 

which this report would not have been possible.

The U.S. Geological Survey coordinated its investigation of the High Plains 

aquifer with a concurrent study by the Economic Development Administration of the Department of Commerce. The Six-State High Plains Ogallala 

Aquifer Area study conducted by the Ecomomic Development Administration 

was authorized by Congress in 1976. The study was charged with the responsibility of examining the feasibility of increasing water supplies to insure the 

economic growth and vitality of the High Plains. The results of that study are 

used extensively in this report. Together, these two studies provide a comprehensive evaluation of the High Plains aquifer and the potential impacts of 

declining ground-water supplies on the region. The Economic Development Administration study developed and proposed alternative strategies to alleviate 

or mitigate those adverse effects and the U.S. Geological Survey has provided 

hydrologic data and models needed to evaluate the effects of those strategies 

on the ground-water resource.
CONVERSION FACTORS

The following report uses inch-pound units as the primary system of 

measurements. The units commonly are abbreviated using the notations shown 

below in parentheses. Inch-pound units can be converted to metric units by 

multiplying by the factors given in the following list.

Inch-pound unit Multiply by To obtain metric unit

inch (in.) 2.540X101 millimeter

foot (ft) 3.048XKT1 meter

mile (mi) 1.609 kilometer

acre 4.047 X10"1 hectare

square mile (mi2) 2.590 square kilometer

acre-foot (acre-ft) 1.233X10"3 cubic hectometer

acre-foot per year 1.233X10"3 cubic hectometer per year

(acre-ft/yr)

cubic foot per second (ft3/s) 2.832X10~2 cubic meter per second

gallon per minute (gal/min) 6.308X10"2 liter per second

inch per year (in./yr) 2.540X10"1 millimeter per year

foot per day (ft/d) 3.048 X10'1 meter per day
CONTENTS

Abstract .................................

Introduction .............................

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

High Plains aquifer ....................

Ground-water flow models ..................

Model calibration ......................

Ground-water management strategies .....

Projected water levels and saturated thickness 

Southern High Plains ..................

Baseline strategy ..................

Management strategy 1 .............

Management strategy 2 .............

Comparison of strategies ............

Central High Plains ....................

Baseline strategy ..................

Page

El

1

4

4

4

6

8

9

9

10

12

16

16

16

20

Page 

Central High Plains Continued

Management strategy 1 ....................... E22

Management strategy 2 ......................

Comparison of strategies .....................

Northern High Plains ...........................

Baseline strategy ...........................

Management strategy 1 ......................

Management strategy 2 ......................

Comparison of strategies .....................

Projected well yields ...............................

Southern High Plains ...........................

Central High Plains .............................

Northern High Plains ...........................

Summary and conclusions ...........................

References cited ...................................

25

27

27

33

34

34

36

38

38

41

41

41

43

ILLUSTRATIONS

Page

FIGURES 1-4. Maps showing:

1. Location of High Plains aquifer .......................................................... E2

2. Division of the High Plains and grids for the models ....................................... 5

3. Density of acreage irrigated by ground water in the High Plains, 1978 ........................ 7

4. Regions for which pumpage projections were available for the southern High Plains ............. 10

5. Graph showing simulated pumpage for the southern High Plains by management strategy ................ 12

6-11. Maps showing:

6. Projected water-level changes, 1980 to 2020, for the southern High Plains resulting from pumpage for

the baseline strategy ............................................................... 13

7. Projected saturated thickness by 2020 in the southern High Plains resulting from pumpage for the baseline

strategy .......................................................................... 14

8. Projected water-level changes, 1980 to 2020, for the southern High Plains resulting from pumpage for

management strategy 1 ............................................................. 15

9. Projected water-level changes, 1980 to 2020, for the southern High Plains resulting from pumpage for

management strategy 2 ............................................................. 17

10. Difference in projected saturated thickness by 2020 between management strategy 2 and the baseline

strategy for the southern High Plains ................................................. 18

11. Regions for which pumpage projections were available for the central High Plains .............. 19

12. Graph showing simulated pumpage for the central High Plains by management strategy ................. 22

13-18. Maps showing:

13. Projected water-level declines, 1980 to 2020, for the central High Plains resulting from pumpage for

the baseline strategy ............................................................... 23

14. Projected saturated thickness by 2020 in the central High Plains resulting from pumpage for the baseline

strategy .......................................................................... 24

15. Projected water-level declines, 1980 to 2020, for the central High Plains resulting from pumpage for

management strategy 1 ............................................................. 25

16. Projected water-level declines, 1980 to 2020, for the central High Plains resulting from pumpage for

management strategy 2 ............................................................. 26

VII
VIII CONTENTS

Page

FIGURES 17. Difference in projected saturated thickness by 2020 between management strategy 2 and the baseline

strategy for the central High Plains .................................................. E28

18. Regions for which pumpage projections were available for the northern High Plains ............. 29

19. Graph showing simulated pumpage for the northern High Plains by management strategy ................ 32

20. Graph showing hypothetical streamflow capture for the northern High Plains ........................... 32

21-26. Maps showing:

21. Projected water-level declines, 1980 to 2020, for the northern High Plains resulting from pumpage for

the baseline strategy ............................................................... 33

22. Projected saturated thickness by 2020 in the northern High Plains resulting from pumpage for the

baseline strategy ................................................................... 35

23. Projected water-level declines, 1980 to 2020, for the northern High Plains resulting from pumpage for

managment strategy 2 .............................................................. 36

24. Difference in projected saturated thickness by 2020 between management strategy 2 and the baseline

strategy for the northern High Plains ................................................. 37

25. Probable well yields by 2020 for the High Plains resulting from pumpage for the baseline strategy 39

26. Percentage change in probable well yields, 1980 to 2020, for the High Plains resulting from pumpage for

the baseline strategy ............................................................... 40

27. Graph showing simulated pumpage for the baseline strategy by High Plains model region ................ 42

TABLES

Page

TABLE 1. Simulated pumpage, 1980 to 2020, by strategy and region, for the southern High Plains ....................... Ell

2. Simulated pumpage, 1980 to 2020, by strategy and region, for the central High Plains ........................ 21

3. Simulated pumpage, 1980 to 2020, by strategy and region, for the northern High Plains ....................... 30

4. Projected acreage, water application, and pumpage for northern High Plains regions VIII through XI for the baseline

strategy ........................................................................................ 31
EFFECTS OF FUTURE GROUND-WATER PUMPAGE

ON THE HIGH PLAINS AQUIFER IN PARTS OF

COLORADO, KANSAS, NEBRASKA, NEW MEXICO,

OKLAHOMA, SOUTH DAKOTA, TEXAS, AND WYOMING

By RICHARD R. LUCKEY, EDWIN D. GUTENTAG, FREDERICK J. HEIMES, and JOHN B. WEEKS

ABSTRACT

The U.S. Geological Survey conducted a geohydrologic study of the 

High Plains regional aquifer system to help State and local agencies 

manage the ground-water resource. Digital, finite-difference models 

of the ground-water flow system in the southern, central, and northern 

High Plains were developed during the study. The models were 

calibrated by matching the simulated and measured water levels, 

water-level changes, and streamflow prior to and after development. 

The calibrated models were used to project future water levels based 

on a baseline strategy (continuation of current economic trends and 

government policies) and on alternatives involving a voluntary reduction in water use (management strategy 1) and a mandatory reduction in water use (management strategy 2).

In the southern High Plains, the total simulated pumpage from 1980 

to 2020 would be 113 million acre-feet for the baseline strategy, 109 

million acre-feet for management strategy 1, and 88 million acre-feet 

for management strategy 2. For the baseline strategy, water levels 

in the southern High Plains are projected to decline more than 150 

feet between 1980 and 2020 in about 700 square miles. More than onehalf of the aquifer would have less than 25 feet of saturated thickness 

remaining by 2020, and slightly more than 100 million acre-feet of 

drainable water would remain in storage compared to about 200 million 

acre-feet during 1980. By 2020, probable well yields throughout most 

(80 percent) of the southern High Plains would be less than 250 gallons 

per minute. Similar water-level declines are projected for management 

strategy 1. For management strategy 2, water-level declines would 

continue to 2020 but would be less severe, resulting in about 125 

million acre-feet of drainable water remaining in storage by 2020.

In the central High Plains, simulated pumpage from 1980 to 2020 

would be 158 million acre-feet for the baseline strategy, 178 million 

acre-feet for management strategy 1, and 138 million acre-feet for 

management strategy 2. For the baseline strategy, water levels in the 

central High Plains are projected to decline more than 100 feet from 

1980 to 2020 in about 3,000 square miles. Although more than 400 

feet of saturated thickness are projected to remain in a few small areas, 

the average saturated thickness would be about 100 feet by 2020. Probable well yields in the central High Plains would decrease by more 

than 25 percent from 1980 to 2020 in 22,750 square miles (47 percent 

of the area), but would be more than 750 gallons per minute in 32 percent of the area. For management strategy 1, water-use per acre would 

decrease, but irrigated acreage would increase, so total water use would 

increase and water-level declines would be larger. For management 

strategy 2, water-level declines in excess of 100 feet from 1980 to 2020 

are projected in about 1,700 square miles.

In the northern High Plains, simulated pumpage from 1980 to 2020 

would be 357 million acre-feet for the baseline strategy, 360 million 

acre-feet for management strategy 1, and 271 million acre-feet for

management strategy 2. For the baseline strategy, water levels in the 

northern High Plains are projected to decline more than 100 feet from 

1980 to 2020 in about 10,000 square miles. Probable well yields are 

projected to decrease by more than 75 percent from 1980 to 2020 in 

parts of the northern High Plains. However, probable well yields in 

excess of 750 gallons per minute are projected for 58 percent of the 

area by 2020. For management strategy 1. water-level declines would 

be virtually identical to those for the baseline strategy. For management strategy 2, water-level declines in excess of 100 feet from 1980 

to 2020 are projected in about 5,400 square miles. For all strategies, 

more than 800 feet of saturated thickness are projected to remain in 

part of central Nebraska by 2020.

INTRODUCTION

The U.S. Geological Survey began a study of the High 

Plains regional aquifer in 1978 (Weeks, 1978) as part of 

its program of regional aquifer-system analysis (Sun, 

1986). Major objectives of the High Plains study were 

to (1) provide hydrologic information needed to evaluate 

the effects of continued ground-water development; (2) 

design and develop computer models to simulate the 

aquifer system; and (3) evaluate aquifer response to future 

ground-water development. The first objective was met 

with the publication of the geohydrologic description of 

the High Plains aquifer (Gutentag and others, 1984). The 

second objective was met with the publication of the 

description of the ground-water simulation models 

(Luckey and others, 1986). This report discusses the effects of future ground-water development.

The High Plains aquifer underlies about 174,000 mi2 

of the central United States east of the Rocky Mountains in the southern part of the Great Plains. Parts 

of Colorado, Kansas, Nebraska, New Mexico, Oklahoma, 

South Dakota, Texas, and Wyoming are underlain by the 

High Plains aquifer (fig. 1). The High Plains aquifer is 

the shallowest and most abundant source of ground 

water in the region. The economy of the area depends 

in large part on irrigated agriculture; the economic 

growth of this region would not have occurred to the extent that it has without the High Plains aquifer.

El
E2 REGIONAL AQUIFER-SYSTEM ANALYSIS
EFFECTS OF FUTURE GROUND-WATER PUMPAGE ON THE HIGH PLAINS AQUIFER

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E4 REGIONAL AQUIFER-SYSTEM ANALYSIS

More than 20 percent of the irrigated land in the 

United States overlies the High Plains aquifer. About 

30 percent of all ground water used in the Nation during 1980 was pumped from the High Plains aquifer. 

Throughout much of the High Plains, the rate of 

ground-water withdrawal greatly exceeds the rate of 

natural replenishment, and this results in water-level 

declines. Consequently, many irrigators have experienced increased pumping costs and decreased well 

yields and are understandably concerned about the 

future of irrigated farming on the High Plains. This 

report describes future water-level declines and the effects of declining water levels on well yields as a result 

of future ground-water development.

PURPOSE AND SCOPE

The general purpose of the High Plains Regional 

Aquifer-System Analysis was to provide the hydrologic 

information and understanding of the aquifer system 

which were needed for effective management of the 

ground-water resource of the High Plains. The aquifer 

system was analyzed by computer-based models which 

are discussed in a report by Luckey and others (1986). 

The models also were used to evaluate the ground-water 

development strategies. The purpose of this report is 

to describe the effects of three different future pumping strategies on the High Plains aquifer.

HIGH PLAINS AQUIFER

The High Plains aquifer consists mainly of 

hydraulically connected geologic units of late Tertiary 

and Quaternary age. The Ogallala Formation of Tertiary age underlies 134,000 mi2 of the 174,000-mi2 

High Plains and is the principal geologic unit of the 

High Plains aquifer. Other older Tertiary units include 

part of the Brule Formation and the Arikaree Group 

(or Formation). Quaternary deposits included in the 

aquifer are alluvium, dune-sand, and valley-fill deposits 

(Gutentag and others, 1984, p. 8-13).

Water levels in the High Plains aquifer range from 

just below land surface to almost 400 ft below land surface. The saturated thickness ranges from almost zero 

to about 1,000 ft. Hydraulic conductivity ranges from 

about 25 to 300 ft/d and averages 60 ft/d. Specific yield 

ranges from about 10 to 30 percent and averages 15 percent. Ground water discharges naturally to streams and 

springs and directly to the atmosphere by evapotranspiration where the water table is near land surface. 

Precipitation is the principal source of recharge to the 

High Plains aquifer. Recharge rates estimated with the

calibrated model ranged from 0.056 to 1.52 in./yr 

(Luckey and others, 1986, p. 52-53). Typically, recharge 

estimates are greatest for areas with sandy soils. During 1980, the High Plains aquifer contained about 3.25 

billion acre-ft of drainable water (Gutentag and others, 

1984, p. 34). About 66 percent of the water in storage 

was in Nebraska, 12 percent was in Texas, and about 

10 percent was in Kansas.

About 95 percent of all water pumped from the High 

Plains aquifer is used for irrigation. During 1980, more 

than 170,000 irrigation wells pumped an estimated 18 

million acre-ft of water from the High Plains aquifer to 

irrigate 13 million acres (Heimes and Luckey, 1983, 

p. 34).

Large water-level declines have occurred in some 

areas of the aquifer. Water levels have declined more 

than 100 ft from predevelopment to 1980 in areas totaling 2,500 mi2 in parts of Kansas, New Mexico, Oklahoma, and Texas (Luckey and others, 1981). Water 

levels declined more than 50 ft in areas totaling 12,000 

mi2 in the same four states and more than 10 ft in 

areas totaling 50,000 mi2 in Colorado, Kansas, 

Nebraska, New Mexico, Oklahoma, and Texas. By 1980, 

the volume of water in storage in the aquifer had 

decreased about 166 million acre-ft since ground-water 

development began (Gutentag and others, 1984, table 

11). Most of the depletion of water in storage had occurred in Texas and Kansas; about 114 million acre-ft 

had been depleted in Texas, and 29 million acre-ft had 

been depleted in Kansas.

Water-level declines increase pumping lift, decrease 

well yields, increase the cost of water, and generally 

limit development of the ground-water resource. 

Although well yields of more than 750 gal/min generally can be obtained throughout large areas of the High 

Plains (Gutentag and others, 1984, fig. 24), only wells 

yielding less than 250 gal/min can be constructed where 

the saturated thickness is thin near the edge of the 

aquifer or where water-level declines have greatly 

decreased the saturated thickness.

GROUND-WATER FLOW MODELS

The High Plains was divided into three parts, as 

shown in figure 2, for modeling purpose. The southern 

High Plains is that part of the High Plains in Texas and 

New Mexico south and west of about lat 35° N., long 

102 ° W. The central High Plains includes the area north 

and east of about lat 35° N., long 102° W. and south 

of about lat 39° N. The northern High Plains includes 

all of the High Plains north of about lat 39° N.

A narrow strip of aquifer, about 12 mi wide, joins the 

southern and central High Plains in the vicinity of
EFFECTS OF FUTURE GROUND-WATER PUMPAGE ON THE HIGH PLAINS AQUIFER E5

"%. CANADIAN

NEW MEXICO

AQUIFER 

BOUNDARY- EXPLANATION 

Boundary between areas of the 

high plains

| | Model node

| | Common nodes between models

FIGURE 2. Division of the High Plains and grids for the models.
E6 REGIONAL AQUIFER-SYSTEM ANALYSIS

Amarillo, Tex. (fig. 1). The strip of aquifer joining the 

central and northern High Plains is about 32 mi wide 

and follows a bedrock high and a thin saturated section 

of the aquifer. There probably is very little exchange 

of water between the southern and central High Plains 

or between the central and northern High Plains. 

Because of the narrowness of the strips joining the three 

separate parts of the High Plains aquifer, construction 

of separate ground-water flow models for each part of 

the High Plains probably did not create significant 

errors.

The history of ground-water development in the High 

Plains was divided into two periods, the period prior to 

large-scale development of irrigation (predevelopment 

period) and the period after the beginning of significant 

development of irrigation (development period). Irrigation development began prior to 1940 in Texas and by 

1978 had spread throughout much of the High Plains 

(fig. 3). By 1978, more than one-half of the land was irrigated in large parts of the southern High Plains and 

in smaller parts of the central and northern High Plains. 

The development period was further subdivided as 

needed.

The ground-water flow model used during this study 

solves the ground-water flow equation in two dimensions at a regular network of nodes that are spaced 

10 mi apart in both the north-south and east-west directions (fig. 2). The computer code that solves the flow 

equations was described by Trescott and others (1976). 

Basically, the flow model integrates information on 

aquifer geometry, boundary conditions, aquifer 

parameters, and stresses with initial conditions to 

calculate a resulting water-level configuration, base flow 

to streams, flow across aquifer boundaries, and change 

of water in storage. Before the models were used to 

evaluate future hydrologic conditions due to pumping, 

they were calibrated to the degree that the models could 

adequately simulate historical hydrologic conditions. 

The model calibration was described in detail by Luckey 

and others (1986), and only a brief summary of the 

calibration is given here.

MODEL CALIBRATION

The models of each of the three parts of the High 

Plains aquifer were calibrated individually. Simulations 

were made for each part of the system prior to largescale irrigation development (predevelopment period) 

and during large-scale irrigation development (development period).

The model of the 29,000-mi2 southern High Plains 

aquifer had 303 active nodes (fig. 2). The predevelopment-period (prior to 1940) model was used to estimate

the predevelopment recharge rate over the area and to 

refine estimates of aquifer parameters. The estimated 

predevelopment recharge rate ranged from 0.086 to 1.03 

in./yr and averaged 0.13 in./yr. The simulated 

predevelopment water level was compared to the 

historical predevelopment water level, and the average 

difference between the two potentiometric surfaces was 

+0.22 ft. The simulated predevelopment water levels 

became the initial water level for the first developmentperiod (1940-60) model. During this simulation, return 

flow from irrigation was varied until the model adequately simulated the 1960 water level. Once the 

simulated 1960 water level adequately represented the 

measured 1960 water level, the model was used to 

simulate the second development period (1960-80). 

Again return flow from irrigation was varied during 

calibration. For both periods, calibration was achieved 

when return flow was adjusted such that net 

withdrawal (total pumpage minus return flow) was 

equal to 90 percent of the estimated irrigation requirement (Heimes and Luckey, 1982). During the second 

development period (1960-80), 2 in. of additional 

recharge were added to all agricultural land as described 

by Luckey and others (1986, p. 18). The simulated 

change in storage for 1940 to 1980 was 7 percent less 

than the actual change in storage for the same period 

(Luckey and others, 1986, p. 54).

The model of the 48,500-mi2 central High Plains 

aquifer had 513 active nodes (fig. 2). There was one common node between the southern and central High Plains 

models. The predevelopment-period (prior to 1950) 

model was used to estimate the predevelopment 

recharge rate and to refine estimates of aquifer 

parameters. The estimated predevelopment recharge 

rate ranged from 0.056 to 0.84 in./yr, averaged 0.13 

in./yr, and was distributed according to soil type. When 

the model was calibrated, the mean difference between 

the simulated and historical predevelopment water 

levels was -0.28 ft. The simulated predevelopment 

water level was used as the initial water level for a single 

development period (1950-80). During the developmentperiod calibration, return flow was adjusted to obtain 

the best correlation between the simulated and 

measured 1950-80 water-level changes. Calibration was 

obtained when return flow was adjusted such that net 

pumpage equaled 100 percent of the estimated irrigation requirement. The simulated change in storage was 

9 percent less than the actual change in storage (Luckey 

and others, 1986, p. 31).

The model of the 96,500-mi2 northern High Plains 

aquifer had 943 active nodes (fig. 2). There were five 

common nodes between the central and northern High 

Plains models. The predevelopment-period (prior to 

1960) model of the northern High Plains was used to
EFFECTS OF FUTURE GROUND-WATER PUMP AGE ON THE HIGH PLAINS AQUIFER E7

I EXPLANATION 

\ Density of irrigated

FIGURE 3. Density of acreage irrigated by ground water in the High Plains, 1978.
E8 REGIONAL AQUIFER-SYSTEM ANALYSIS

estimate predevelopment recharge from precipitation 

and to refine estimates of aquifer parameters. The 

estimated predevelopment recharge ranged from 0.076 

to 1.52 in./yr, averaged 0.46 in./yr, and was distributed 

according to soil type. An analysis of the flow of 

streams originating in the sandhills of central Nebraska 

indicated that recharge in the sandhills probably is 

greater than the estimated 1.52 in./yr. When the model 

was calibrated, the mean difference between the 

simulated and historical predevelopment water levels 

was +0.30 ft and the simulated base flow was 61 percent of the historical base flow. The simulated 

predevelopment water level was used as the initial water 

level for a development-period calibration. In the 

development-period (1960-80) calibration, return flow 

from irrigation was adjusted and the best correlation 

between simulated and measured water-level changes 

from 1960 to 1980 was achieved when net withdrawal 

equaled 100 percent of the estimated irrigation requirement. In the northern High Plains, there was substantial recharge due to agricultural practices and leakage 

from canals and surface-water reservoirs. This additional recharge and return flow from irrigation in large 

part counterbalanced the pumpage. Hence, although 

large pumping and recharge stresses have occurred in 

some areas, the net overall change in storage from 

predevelopment to 1980 was small. The simulated 

change in storage was 15 million acre-ft, and the actual 

change in storage was 6 million acre-ft. This difference 

of 9 million acre-ft is less than 10 percent of the total 

pumpage from 1960 to 1980.

GROUND-WATER MANAGEMENT STRATEGIES

After the models of each area of the High Plains were 

calibrated and the 1980 water levels were computed, the 

models were used to project water levels and water-level 

changes from 1980 to 2020. The simulation of future 

water levels required estimates of future rates of 

withdrawal of water. A concurrent study done for the 

U.S. Department of Commerce, Economic Development 

Administration, projected pumpage throughout much 

of the High Plains aquifer for 1977, 1985, 1990, 2000, 

and 2020 (High Plains Associates, 1982; High Plains 

Study Council, 1982). The study evaluated several different water-resource management strategies in parts 

or all of a six-State area. The pumpage estimates for 

three of these strategies were used to project future 

water levels in the High Plains.

The three ground-water management strategies defined by High Plains Associates (1982, p. 7) that were 

used to project water levels are:

1. "A 'Baseline' trend projection of currently

available water conservation and use technology 

and practices already in use to some extent, with 

no new purposeful public policy to intervene with 

action programs for altering the course of irrigation water consumption, (the Baseline);"

2. "A strategy which would stimulate voluntary action to reduce water demands through research, 

education, demonstration programs and incentives, using technology and practices either not 

considered in the Baseline analysis or reflected 

at rates which would be purposefully accelerated. 

(Management Strategy One);" and

3. "A strategy which assumes Strategy One policies 

and programs, and in addition projects further 

water demand reduction by mandatory programs 

of a regulatory nature to control water use. 

(Management Strategy Two)." 

The baseline strategy assumes a continuation of current government policies and economic trends with no 

new State or Federal programs undertaken that have 

not already been implemented or authorized. Management strategy 1 assumes faster adoption of new techniques to conserve water and voluntary measures to 

decrease irrigation water use. Management strategy 1 

decreases per-acre water use, but in some areas the strategy may result in increased irrigated acreage and, hence, 

increased pumpage. Management strategy 2 is based on 

the assumption that, in addition to all the voluntary 

water conservation measures assumed under management 

strategy 1, mandatory water conservation measures 

would be imposed by governmental agencies. For management strategy 2, water application rates for 1985, 

1990, 2000, and 2020 were assumed to be decreased to 

90, 80, 70, and 70 percent of those projected for management strategy 1, respectively. For management strategy 

2, the irrigated acreage is assumed to be equal to the 

irrigated acreage for management strategy 1.

In addition to the regional reports by High Plains 

Associates (1982) and High Plains Study Council (1982), 

other reports resulting from the Economic Development 

Administration study were published for each of the six 

States involved. The Colorado part of the study was 

summarized by the Colorado Department of Agriculture 

(1983) with more detail given by Burns (1982), McBroom 

(1982), McKean (1982), and Young and others (1982). 

The results of the Kansas part of the study were 

reported by Buller (1982), Emerson and others (1982), 

and Wagner and others (1982). The Nebraska Natural 

Resources Commission (1981) summarized that State's 

part of the study. The New Mexico part of the study 

was summarized by Lansford and others (1982f) with 

details given by Lansford and others (1982a, b, c, d, e). 

The results of the Oklahoma part of the study were 

given by Warren and others (1981). The results of the
EFFECTS OF FUTURE GROUND-WATER PUMPAGE ON THE HIGH PLAINS AQUIFER E9

Texas part of the study were given by Grubb (1984). 

Supalla (1982) summarized the methodology of the 

Economic Development Administration study while 

Warren and others (1981) determined that the irrigatedacreage projections and, hence, pumpage projections are 

very sensitive to the assumed real commodity prices.

PROJECTED WATER LEVELS AND 

SATURATED THICKNESS

SOUTHERN HIGH PLAINS

The southern High Plains is an area of 29,000 mi2 in 

Texas and New Mexico south and west of about lat 35° 

N., long 102° W. The southern High Plains constitutes 

17 percent of the total area of the High Plains. About 

one-half of the water pumped from the High Plains 

aquifer prior to 1980 was from the southern High Plains.

Pumpage projections were available for the eight 

regions in the southern High Plains shown in figure 4. 

Four of the regions are in Texas, and four are in New 

Mexico. The regions in Texas correspond to the subregions defined by High Plains Associates (1982, fig. 

II-l), and the regions in New Mexico correspond to 

counties. Region I is part of Subregion 2 of Texas (High 

Plains Associates, 1982) which includes part of the central High Plains. Pumpage projections for this region 

were divided by assigning 90 percent of the pumpage 

to the southern High Plains and 10 percent to the central High Plains. Pumpage projections for the regions 

in Texas were available on an annual basis from 1980 

through 2020 (H.W. Grubb, Texas Department of Water 

Resources, written commun., August 1983). Pumpage 

estimates for the regions in New Mexico were available 

for 1977, 1985, 1990, 2000, and 2020 (Lansford and 

others, 1982a, table 1; 1982b, table 2; 1982c, table 1; 

1982d, table 1; 1982e, table 2). Pumpage projections for 

individual years from 1980 to 2020 were made for 

regions V-VIII by linear interpolation between the years 

for which pumpage estimates were available.

The pumpage had to be distributed to the model 

nodes, which are considerably smaller than the regions. 

The projected pumpage was distributed throughout the 

area that was irrigated during 1980, as mapped by 

digital analysis of Landsat imagery (Thelin and Heimes, 

in press). During simulation, the pumpage for each 

region was distributed according to the 1980 irrigated 

area in the region until the average saturated thickness 

at a model node decreased to less than 5 ft. If saturated 

thickness was less than 5 ft at the beginning of a 5-year 

simulation period, irrigated acreage in the node was 

assumed to be zero, pumpage at that node ceased, and 

the projected pumpage was redistributed to the remaining irrigated acreage in the region. If saturated thickness for the node decreased to less than 2 ft during a 

5-year simulation period, pumpage was immediately curtailed at that node and the pumpage was not redistributed to other nodes until the beginning of the next 

5-year simulation period. This procedure for distributing 

pumpage to model nodes also was used for the central 

model and part of the northern model.

The simulated pumpage for the southern High Plains 

is given in table 1. For the baseline strategy, total pumpage would be about 113 million acre-ft for the 40 years. 

The pumpage would range from almost 4.9 million acreft/yr for 1980-84 to less than 2.0 million acre-ft/yr for 

2015-19. For management strategy 1, pumpage would 

be about 109 million acre-ft for the 40 years. The pumpage would range from 4.6 million acre-ft/yr for 1980-84 

to less than 2.0 million acre-ft/yr for 2015-19. For 

management strategy 2, pumpage would be about 88 

million acre-ft for the 40 years. The pumpage would 

range from almost 4.6 million acre-ft/yr for 1980-84 to 

slightly more than 1.4 million acre-ft/yr for 2015-19. For 

management strategy 2, simulated pumpage by 2020 

would be less than one-third of the 1980 pumpage. For 

all three strategies the pumpage in Region I would be 

about one-half of the total pumpage.

The simulated pumpage for the southern High Plains 

is summarized in figure 5. During the first two 5-year 

simulation periods, pumpage for management strategy 

1 would be significantly smaller than pumpage for the 

baseline strategy, but after 1990, pumpage for management strategy 1 and the baseline strategy would be practically identical. Pumpage for management strategy 2 

would be smaller than pumpage for both the baseline 

strategy and management strategy 1, particularly after 

1985. By the last 5-year simulation period (2015-19), 

pumpage for management strategy 2 would be only 73 

percent of pumpage for the baseline strategy or management strategy 1. The total volume that would be pumped 

for management strategy 1 would be 4 percent less than 

that for the baseline strategy, whereas the total volume 

that would be pumped for management strategy 2 would 

be 22 percent less than that for the baseline strategy.

During model calibration, return flow was assumed 

to be a function of water applied in excess of the irrigation requirement (Luckey and others, 1986, p. 9). However, pumpage for most of the 1980 to 2020 projection 

would be less than the estimated irrigation requirement 

(Heimes and Luckey, 1982). Also, for those States that 

considered return flow in the Economic Development 

Administration study, the return flow would be small 

compared to the pumpage. Therefore, return flow was 

assumed to be negligible and was not simulated during 

the projection period in the southern, central, and northern High Plains models.
E10

104°

REGIONAL AQUIFER-SYSTEM ANALYSIS

103° 102° 101 C

EXPLANATION

\\J Pumpage region and 

number in table 1

FIGURE 4. Regions for which pumpage projections were available for the southern High Plains.

BASELINE STRATEGY

The projected water-level changes from 1980 to 2020 

that would result from baseline-strategy pumpage are 

shown in figure 6. Much of the southern High Plains

would have water-level declines in excess of 10 ft for 

this strategy and declines are projected to exceed 150 ft 

in two areas. The size of the larger area is about 

700 mi2. The maximum 1980 to 2020 water-level 

decline would be about 180 ft over one model node
EFFECTS OF FUTURE GROUND-WATER PUMPAGE ON THE HIGH PLAINS AQUIFER 

TABLE 1. Simulated pumpage, 1980 to 2020, by strategy and region for the southern High Plains

Ell

wfegion Simulated pumpage,

1980- 

1984

Baseline strategy 

I.......... 2

II.........

III. .......

IV. ........

V. .........

VI.........

VII. .......

VIII.......

Total.... 4

Management strategy 

I.......... 2

II.........

III........

IV.........

V. .........

VI.........

VII. .......

VIII.......

Total.... 4

Management strategy 

I.......... 2

II.........

III........

IV.........

V..........

VI.........

VII. .......

VIII.......

Total.... 4

,610 

984 

473 

40 

12 

312 

221 

236

,888

1 

,558 

870 

402 

35 

12 

310 

217 

230

,634

2 

,558 

870 

402 

35 

11 

289 

203 

216

,584

1985- 

1989

1,710 

685 

345 

32 

11 

282 

217 

253

3,535

1,574 

563 

276 

26 

10 

278 

208 

237

3,172

1,356 

486 

237 

23 

9 

238 

179 

203

2,731

in thousands of acre-feet per

1990- 

1994

1,290 

508 

270 

27 

10 

211 

209 

267

2,792

1,389 

484 

261 

26 

10 

205 

197 

237

2,809

1,084 

378 

203 

20 

8 

162 

153 

185

2,193

1995- 

1999

1,210 

469 

260 

27 

12 

147 

207 

270

2,602

1,285 

443 

249 

25 

11 

139 

191 

232

2,575

938 

323 

182 

19 

8 

104 

139 

170

1,883

2000- 

2004

1,160 

432 

252 

27 

11 

97 

189 

268

2,436

1,221 

404 

238 

25 

10 

90 

180 

228

2,396

855 

283 

167 

18 

8 

70 

124 

159

1,684

year, for

2005- 

2009

1,120 

397 

242 

28 

8 

70 

152 

258

2,275

1,163 

367 

227 

26 

7 

65 

160 

222

2,237

814 

257 

160 

18 

8 

69 

111 

156

1,593

the indicated period

2010- 

2014

1,080 

363 

234 

32 

5 

38 

106 

246

2,104

1,109 

332 

216 

29 

4 

35 

138 

217

2,080

776 

232 

151 

20 

8 

67 

95 

152

1,501

2015- 

2019

1,030 

331 

226 

42 

2 

16 

76 

239

1,962

1,057 

299 

205 

41 

2 

15 

121 

213

1,953

740 

209 

143 

29 

8 

66 

85 

149

1,429

(100 mi2). Water levels are projected to decline more 

than 100 ft in several areas of the southern High Plains 

that total about 2,900 mi2. The average projected 

water-level decline from 1980 to 2020 for the baseline 

strategy in the southern High Plains would be 32 ft. 

The median decline would be 13 ft; this means that for 

the baseline strategy, one-half of the area would have 

water-level declines in excess of 13 ft. The median is less 

than the average because the average is influenced more 

by the larger water-level declines than is the median. 

The projected water-level declines from 1980 to 2020 

would be in addition to the water-level declines of as 

much as 150 ft that have already occurred in the 

southern High Plains prior to 1980 (Luckey and others,

1981). The small projected water-level rises near the 

southern and eastern boundaries probably were due to 

neglecting small streams in the nodes where ground 

water discharges.

The total volume of water that would be removed 

from storage in the southern High Plains during the 40 

years is projected to be 101 million acre-ft. The 

12-million-acre-ft difference between the volume 

pumped and the volume removed from storage would 

be supplied by decreased seepage across the eastern 

boundary and decreased ground-water discharge to 

small streams near the eastern boundary.

The projected saturated thickness remaining in the 

southern High Plains by 2020 is shown in figure 7. The
E12 REGIONAL AQUIFER-SYSTEM ANALYSIS

LU

LU 4 

0_

O 3

Z 

O

0-

Q 

LU

I'

EXPLANATION

Baseline strategy 

Management strategy 1 

Management strategy 2

1980-84 1985-89 1990-94 1995-99 2000-04 2005-09 2010-14 

FIGURE 5. Simulated pumpage for the southern High Plains by management strategy.

2015-19

saturated thickness would exceed 100 ft in several 

areas that total 1,500 mi2 . The area in the east-central 

part of the southern High Plains represents 600 mi2 of 

this total. These areas were not extensively irrigated 

in 1980, and they have about the same saturated 

thickness projected for 2020 that they had in 1980. Projected saturated thickness for 2020 for the baseline 

strategy would be less than 25 ft in 54 percent of the 

southern High Plains and less than 19 ft in 50 percent 

of the area. Although the average saturated thickness 

by 2020 in the southern High Plains for the baseline 

strategy would be 36 ft, figure 7 shows that this would 

not be distributed uniformly. Under much of the area 

that was intensely irrigated in 1980, the projected 

saturated thickness by 2020 would be less than 10 ft. 

By 2020, drainable water in storage is projected to be 

slightly more than 100 million acre-ft for the southern 

High Plains. Most of this water will be concentrated 

along the eastern, southern, and western edges of the 

aquifer. The aquifer contained about 200 million acreft of drainable water in 1980 and for the baseline 

strategy would contain about 140 million acre-ft in 

2000.

MANAGEMENT STRATEGY 1

The projected water-level changes from 1980 to 2020 

resulting from management-strategy-1 pumpage are 

shown in figure 8. Projected water-level declines would 

exceed 150 ft in two areas totaling 450 mi2 . The extent 

of the larger area would be 400 mi2 . By 2020, 

simulated 1980 to 2020 water-level declines would exceed 100 ft under 2,300 mi2 . The maximum projected 

water-level decline for 1980 to 2020 would be about 180 

ft. Although the most severe declines would be less for 

management strategy 1 than for the baseline strategy, 

the extent of significant water-level declines (declines 

in excess of 10 ft) are similar for management strategy 

1 and the baseline strategy. Much of the water that 

would be saved in the early part of the 1980 to 2020 

projection period for management strategy 1 would be 

pumped later in the period so that total pumpage for 

management strategy 1 would be only 3 percent less 

than that for the baseline strategy. The average waterlevel decline for 1980 to 2020 for management strategy 

1 would be 31 ft, and the median decline would be 13 ft. 

The average water-level decline prior to 1980 for the
EFFECTS OF FUTURE GROUND-WATER PUMPAGE ON THE HIGH PLAINS AQUIFER

104° 103° 102° 101°

E13

EXPLANATION

Water-level change, 

in feet

Rise more than 10 

+10 to-10 

-10 to-25

-25 to -50

-50 to-100

-100 to-150 

Decline more than 150

FIGURE 6. Projected water-level changes, 1980 to 2020, for the southern High Plains resulting from pumpage for the

baseline strategy.
E14

33°-

32° ~ -

104°

REGIONAL AQUIFER-SYSTEM ANALYSIS

103° 102°

EXPLANATION

Saturated thickness, 

in feet

Oto25 

25 to 50

50 to 100 

More than 100

FIGURE 7. Projected saturated thickness by 2020 in the southern High Plains resulting from pumpage for the baseh'ne

strategy.
EFFECTS OF FUTURE GROUND-WATER PUMPAGE ON THE HIGH PLAINS AQUIFER

1G4 C 103° 102° 101°

E15

EXPLANATION

Water-level change, 

in feet

Rise more than 10 

+10 to-10 

-10 to -25

-25 to -50

-50 to-100

-100 to-150 

Decline more than 150

FIGURE 8. Projected water-level changes, 1980 to 2020, for the southern High Plains resulting from pumpage for

management strategy 1.
E16 REGIONAL AQUIFER-SYSTEM ANALYSIS

southern High Plains was about 33 ft (Luckey and 

others, 1981), and the median decline was 20 ft.

The total volume of water that would be removed 

from storage in the southern High Plains from 1980 to 

2020 for management strategy 1 is projected to be 98 

million acre-ft. The average saturated thickness projected for 2000 would be 48 ft and by 2020 it would be 

37 ft. For management strategy 1, one-half of the 

southern High Plains is projected to have less than 20 

ft of saturated thickness by 2020. By 2020, less than 

105 million acre-ft of drainable water would remain in 

storage in the southern High Plains.

MANAGEMENT STRATEGY 2

The projected water-level changes from 1980 to 2020 

resulting from management-strategy-2 pumpage are 

shown in figure 9. The large mandatory decrease in 

water use will have a significant effect on water-level 

changes. For management strategy 2, there would be 

only one small area (30 mi2) where water levels are projected to decline more than 150 ft, and the maximum 

decline would be only slightly more than 150 ft. The two 

areas where management-strategy-2 water levels are 

projected to decline more than 100 ft total about 2,000 

mi2 . For management strategy 2, about 47 percent of 

the area of the southern High Plains is projected to have 

water-level declines of less than 10 ft. The average projected water-level decline from 1980 to 2020 for this 

management strategy would be 26 ft.

The total volume of water that would be removed 

from storage in the southern High Plains from 1980 to 

2020 for management strategy 2 is projected to be 80 

million acre-ft. The average saturated thickness projected for 2000 would be 51 ft, and by 2020 it would 

be 42 ft. For management strategy 2, one-half of the 

area of the southern High Plains would have less than 

34 ft of saturated thickness remaining by 2020. By 

2020, about 125 million acre-ft of drainable water would 

remain in storage in the southern High Plains.

COMPARISON OF STRATEGIES

Different volumes of pumpage for the baseline strategy, management strategy 1, and management strategy 

2 resulted in different projected water-level changes. 

Because the pumping pattern is assumed to be similar 

for all three strategies, the pattern of water-level change 

would be similar for all strategies although the magnitude of the change would be different. Compared to the 

baseline strategy, the projected water-level declines 

would be slightly less for management strategy 1 and 

would be much less for management strategy 2. Waterlevel declines are projected to exceed 100 ft under 

2,900 mi2 for the baseline strategy, 2,300 mi2 for 

management strategy 1, and 2,000 mi2 for management strategy 2. The maximum water-level decline 

would be about 180 ft for both the baseline strategy and 

management strategy 1 but would be only about 150 

ft for management strategy 2. The median decline would 

be about 13 ft for both the baseline strategy and 

management strategy 1 and about 10 ft for management strategy 2. The average water-level decline for 

management strategy 1 would be 1 ft less than that for 

the baseline strategy, whereas the average water-level 

decline for management strategy 2 would be 7 ft less 

than that for the baseline strategy.

The difference in saturated thickness between management strategy 2 and the baseline strategy by 2020 

is shown in figure 10. The maximum difference in the 

saturated thickness by 2020 between management 

strategy 2 and the baseline strategy would be 63 ft. In 

two areas, more than 50 ft of saturated thickness could 

be saved as a result of the mandatory decrease in water 

use of management strategy 2. These areas compose 

about 2 percent of the area of the southern High Plains. 

The difference in saturated thickness would exceed 25 ft 

in 3,200 mi2 and 10 ft in about 6,600 mi2 (23 percent of 

the southern High Plains). In areas with less than 10 ft 

difference in saturated thickness, the average difference 

is only 1.3 ft.

For the baseline strategy, ground-water storage is 

projected to decrease by 101 million acre-ft from 1980 

to 2020. A similar decrease in storage (98 million acreft) is projected for management strategy 1. For management strategy 2, ground-water storage is projected to 

decrease by 80 million acre-ft during the 40 years.

CENTRAL HIGH PLAINS

The central High Plains consists of 48,500 mi2 in 

Colorado, Kansas, New Mexico, Oklahoma, and Texas 

north and east of about lat 35° N., long 102° W. and 

south of lat 39 ° N. The central High Plains constitutes 

about 28 percent of the entire High Plains. About 24 

percent of the water pumped from the High Plains 

aquifer prior to 1980 was from the central High Plains.

The central High Plains was divided into 12 regions 

(fig. 11) with different pumpage estimates for each 

region. Note that Region VIII has two separate parts. 

Projected pumpage was available for selected years 

(1985, 1990, 2000, and 2020) for all regions except 

Region IX. Actual pumpage was available for 1980 for 

all regions. A linear interpolation was made between 

years for which pumpage was available. Region II is 

part of Region 2 of Texas as defined by High Plains
EFFECTS OF FUTURE GROUND-WATER PUMPAGE ON THE HIGH PLAINS AQUIFER

104° 103° 102° 101°

E17

32° pr

EXPLANATION

Water- level change, 

in feet

Rise more than 10 

+ 10 to-10 

-10 to -25

-25 to -50

-50 to-100

-100 to-150 

Decline more than 150

FIGURE 9. Projected water-level changes, 1980 to 2020, for the southern High Plains resulting from pumpage for

management strategy 2.
E18

104°

REGIONAL AQUIFER-SYSTEM ANALYSIS

103° 102°

35°

34'

EXPLANATION

Saturated-thickness difference, in feet

(Management strategy two minus baseline)

OtolO 

10 to 25

25 to 50 

More than 50

FIGURE 10. Difference in projected saturated thickness by 2020 between management strategy 2 and the baseline

strategy for the southern High Plains.
EFFECTS OF FUTURE GROUND-WATER PUMPAGE ON THE HIGH PLAINS AQUIFER

104° 103° 102° 101° 100°

E19

VI Pumpage region and 

number in table 2

35° U

FIGURE 11. Regions for which pumpage projections were available for the central High Plains.

Associates (1982). The pumpage estimates for this 

region were divided between the southern and central 

High Plains by assigning 10 percent of the pumpage 

to the central High Plains and the remainder to the 

southern High Plains. Region XI is composed of parts 

of Regions 5 and 6 of Colorado as defined by Young and 

others (1982). Twelve percent of Colorado Region 5 

pumpage was assigned to Region XI with the remainder 

assigned to the northern High Plains. Colorado Region 

6 contributed 96 percent of its pumpage to Region XI; 

the remainder was assigned to Region VI. Region XII 

is part of Region 2 in Kansas (Duller, 1982), and the 

pumpage estimates for this region were divided by

assigning 25 percent to the central High Plains and the 

remainder to the northern High Plains. Pumpage 

estimates for all regions were distributed to model 

nodes within the regions as described for the southern 

model.

Region IX is outside the Economic Development Administration study area; hence, pumpage had to be estimated for that region. Pumpage for 1980, assuming 

normal climatic conditions, was estimated by multiplying the 1980 irrigated acreage as mapped from Landsat (Thelin and Heimes, in press) by an estimated annual 

application of water of 1.25 ft. This resulted in a normalized 1980 pumpage of 512,000 acre-ft. The 1.25-ft
E20 REGIONAL AQUIFER-SYSTEM ANALYSIS

application was decreased from a measured application 

of 1.32 ft in 1980 (a relatively hot and dry year) for 4,000 

acres in Stafford County, Kans. (Heimes and Luckey, 

1983, table 2). The baseline-strategy pumpage projection was made using the percentages of the normalized 

1980 pumpage listed below. The percentages approximately define the trend for the combined baselinestrategy pumpage projections for Regions VII and 

VIII. These regions were used to define the trend 

because they are adjacent to Region IX and, when combined, provide a consistent trend. The baseline-strategy 

pumpage projection for Region IX was as follows:

1980-1984 pumpage =85 percent of normalized

1980 pumpage

1985-1989 pumpage =60 percent of normalized

1980 pumpage

1990-1994 pumpage =40 percent of normalized

1980 pumpage

1995-2019 pumpage =30 percent of normalized

1980 pumpage.

Pumpages for management strategy 1 and management strategy 2 were estimated for Region IX using 

ratios between the combined pumpage in Regions VII 

and VIII for the baseline strategy and for management 

strategy 1 and management strategy 2, respectively. 

The baseline-strategy pumpage projection for Region 

IX was multiplied by the following ratios to generate 

management-strategy-1 and management-strategy-2 

pumpage projections:

Region IX pumpage ratio

Years Management strategy 1 Management strategy 2 

to baseline strategy to baseline strategy

1980-84

1985-89

1990-94

1995-99

2000-04

2005-09

2010-14

2015-19

0.97

.99

1.35

2.10

2.26

2.38

2.13

1.89

0.92

.87

1.05

1.51

1.86

1.67

1.49

1.32

The pumpage projections for the central High Plains 

are given in table 2. For the baseline strategy, projected 

pumpage is about 6.0 million acre-ft/yr for 1980-84 and 

decreases to about 3.4 million acre-ft/yr for 2015-19. 

There is a steady decrease in total pumpage throughout 

the central High Plains except for projected increases 

in Regions IV and V. For management strategy 1, 

pumpage is projected to decrease from about 5.7 million 

acre-ft/yr for 1980-84 to about 4.0 million acre-ft/yr for 

2015-19. Note that the projected pumpage is greater

for management strategy 1 than for the baseline 

strategy during later periods. The additional pumpage 

primarily is in Regions VII, VIII, and IX where, 

although less water is applied per acre for management 

strategy 1, the irrigated acreage is more than for the 

baseline strategy (Buller, 1982, p. 81-82). This additional irrigated acreage more than offsets the decreased 

rate of application of water. Projected pumpage for 

management strategy 2 ranges from about 5.5 million 

acre-ft/yr in 1980-84 to about 2.8 million acre-ft/yr in 

2015-19.

The pumpage projections for the central High Plains 

are summarized in figure 12. This figure shows that, 

compared to the baseline strategy, projected pumpage 

is larger for management strategy 1 and smaller for 

management strategy 2 starting in 1990. These pumpages were used to project future water levels and 

saturated thickness for each of the three strategies. The 

total simulated pumpage for 1980 to 2020 is 158 million 

acre-ft for the baseline strategy, 178 million acre-ft for 

management strategy 1, and 138 million acre-ft for 

management strategy 2.

BASELINE STRATEGY

The projected water-level declines from 1980 to 2020 

resulting from baseline-strategy pumpage are shown in 

figure 13. Much of the central High Plains will have 

water-level declines in excess of 10 ft under this 

strategy. The projected water-level declines would exceed 200 ft for the 40 years in 150 mi2 in Texas north 

of the Canadian River. The maximum water-level 

decline from 1980 to 2020 would be about 250 ft. Water 

levels are projected to decline more than 100 ft in 

2,950 mi2 of Texas, Oklahoma, and Kansas. Water 

levels are projected to decline more than 25 ft in 15,700 

mi2 in parts of all States in the central High Plains except New Mexico. For the baseline strategy, the average 

projected water-level decline from 1980 to 2020 in the 

central High Plains would be 26 ft; the median projected 

decline would be 11 ft. The median decline indicates that 

one-half of the area of the central High Plains is projected to have water-level declines of more than 11 ft. 

The average decline is larger than the median decline 

because the average is influenced more by the large 

water-level declines than is the median. These projected 

declines are in addition to the declines, in excess of 50 

ft, that had already occurred in the area by 1980 

(Luckey and others, 1981).

The total volume of water that would be removed from 

storage during the 40 years is projected to be 138 million 

acre-ft. This is about 87 percent of the total volume of 

the simulated pumpage. The 13-percent difference
EFFECTS OF FUTURE GROUND-WATER PUMPAGE ON THE HIGH PLAINS AQUIFER 

TABLE 2. Simulated pumpage, 1980 to 2020, by strategy and region for the central High Plains

E21

Region Simulated pumpage, in thousands of acre-feet per year, for the indicated period

1980- 

1984

1985- 

1989

1990- 

1994

1995- 

1999

2000- 

2004

2005- 

2009

2010- 

201A

2015- 

2019

Baseline strategy

I.......... 2,029 1,802 1,356 1,360 1,426 1,421 1,418 1,416

II......... 290 190 144 134 129 125 120 115

III........ 75 71 53 56 58 59 60 61

IV......... 566 545 519 599 649 654 658 663

V.......... 137 146 154 159 165 173 180 187

VI......... 141 111 78 71 64 57 50 43

VII........ 1132 848 512 408 357 386 416 445

VIII....... 884 674 442 349 289 280 270 261

I.......... 435 310 205 155 155 155 155 155

........... 248 146 91 94 86 62 38 14

.I......... 44 41 37 34 30 25 21 16

.II........ 36 30 24 19 15 13 10 7

Total.... 6,017 4,914 3,615 3,438 3,423 3,410 3,396 3,383

Management strategy 1

I.......... 1,845 1,646 1,379 1,305 1,353 1,332 1,312 1,294

II......... 256 157 139 128 122 116 111 106

III........ 73 67 46 47 47 46 46 46

IV......... 544 501 447 496 521 511 501 491

V.......... 136 143 146 148 151 156 160 192

VI......... 141 120 98 85 81 90 99 108

VII........ 1,057 833 792 1,038 1,150 1,061 971 882

VIII....... 897 686 499 549 564 527 491 454

I.......... 422 307 277 326 350 369 330 293

........... 234 128 82 93 100 98 96 95

.I......... 44 42 41 37 33 29 26 22

.II........ 35 28 26 23 22 21 21 20

Total.... 5,684 4,658 3,972 4,275 4,494 4,356 4,164 4,003

Management strategy 2

I.......... 1,845 1,418 1,076 953 947 932 918 906

II......... 256 136 108 94 86 81 78 74

III........ 69 60 36 34 33 32 32 31

IV......... 515 445 355 348 339 331 322 313

V.......... 132 123 115 109 107 110 113 116

VI......... 137 107 80 64 57 64 71 78

VII........ 999 722 610 747 805 742 680 617

VIII....... 846 598 388 398 395 369 343 318

I.......... 400 270 215 234 288 259 231 205

........... 223 112 64 68 70 69 68 66

.I......... 42 36 30 25 22 20 19 17

.II........ 33 25 20 17 15 15 15 14

Total.... 5,497 4,052 3,097 3,091 3,164 3,024 2,890 2,755
E22 REGIONAL AQUIFER-SYSTEM ANALYSIS

DC

LU

LU 5 

D_

3

ID 

Q.

Q

LU

EXPLANATION 

Baseline strategy 

Management strategy 1 

Management strategy 2

I

1980-84 1985-89 1990-94 1995-99 2000-04 2005-09 2010-14 

FIGURE 12. Simulated pumpage for the central High Plains by management strategy.

201 5-19

between the simulated pumpage and the projected 

volume removed from storage would be supplied 

primarily by decreased seepage to streams.

The projected saturated thickness remaining in the 

central High Plains by 2020 is shown in figure 14. There 

would be two small areas totaling 400 mi2 that are projected to have more than 400 ft of saturated thickness 

remaining by 2020. There would be one large area (3,150 

mi2) and a few small areas projected to have more than 

200 ft of saturated thickness remaining by 2020. There 

would be 21,600 mi2 of the central High Plains that are 

projected to have less than 50 ft of saturated thickness 

remaining by 2020 as a result of baseline-strategy

pumpage. Although the average saturated thickness 

was 104 ft during 1980, some areas, particularly in the 

western part of the central High Plains, are projected 

to have almost zero saturated thickness by 2020. The 

median saturated thickness by 2020 in the central High 

Plains for the baseline strategy is projected to be 82 ft.

MANAGEMENT STRATEGY 1

The projected water-level declines from 1980 to 2020 

resulting from management-strategy-1 pumpage are 

shown in figure 15. Two areas would have declines
104

EFFECTS OF FUTURE GROUND-WATER PUMPAGE ON THE HIGH PLAINS AQUIFER

103° 102° 101° 100°

E23

39°

EXPLANATION

Water- level change, 

in feet

Decline less than 10

-10 to-25

-25 to -50

-50 to -100

-100 to-150

-150 to -200 

Decline more than 200

FIGURE 13. Projected water-level declines, 1980 to 2020, for the central High Plains resulting from pumpage for the baseline strategy.

exceeding 200 ft, one in Texas and one in Kansas. The 

maximum projected water-level decline from 1980 to 

2020 would be about 230 ft. There would be large areas 

totaling 3,850 mi2 where projected water-level declines 

would exceed 100 ft for the 40 years. Water-level 

declines would exceed 10 ft in 55 percent of the central

High Plains as a result of management-strategy-1 

pumpage. Those areas with projected declines of less 

than 10 ft were only sparsely irrigated in 1980 and are 

projected to have little irrigation in the future. The 

average decline from 1980 to 2020 for this strategy 

would be 29 ft, and the median decline would be 12 ft.
E24

104°

REGIONAL AQUIFER-SYSTEM ANALYSIS

102° 101° 100°

EXPLANATION

Saturated thickness, 

in feet

Less than 50 ____j 100 to 200

50 to 100 I [ 200 to 400

, . More than 400

FIGURE 14. Projected saturated thickness by 2020 in the central High Plains resulting from pumpage for the baseline strategy.

The average water-level decline prior to 1980 for the 

area was about 15 ft (Luckey and others, 1981).

The total volume of water that would be removed from 

storage in the central High Plains from 1980 to 2020 for 

management strategy 1 is projected to be 157 million acreft compared to 178 million acre-ft of pumpage. The

12-percent difference between the simulated pumpage and 

the projected volume removed from storage would be supplied primarily by decreased seepage to streams. The 

average projected saturated thickness would be 114 ft by 

2000 and 100 ft by 2020; the median projected saturated 

thickness would be 94 ft by 2000 and 78 ft by 2020.
104°

EFFECTS OF FUTURE GROUND-WATER PUMPAGE ON THE HIGH PLAINS AQUIFER

103° 102° 101° 100° 99° 98°

E25

97°

EXPLANATION

Water- level change, 

in feet

Decline less than 10 r ^J ~50 to -100

-10 to-25 | t:^**1 -100 to-150

-25 to-50 UK -150 to-200

Decline more than 200

FIGURE 15. Projected water-level declines, 1980 to 2020, for the central High Plains resulting from pumpage for management strategy 1.

MANAGEMENT STRATEGY 2

The projected water-level declines from 1980 to 2020 

resulting from management-strategy-2 pumpage are 

shown in figure 16. Even with significant mandatory

decreases in water use, the central High Plains will continue to have large water-level declines between 1980 

and 2020. No areas are projected to have declines in excess of 200 ft; the maximum projected water-level 

decline for 1980 to 2020 for management strategy 2 is
E26

104° 103

REGIONAL AQUIFER-SYSTEM ANALYSIS

102° 10! c 100°

35° r

EXPLANATION

Water-level change, 

in feet

Decline less than 10

-10 to -25

-25 to -50

H

~\ ~50 to-100 

-100 to-150 

Decline more than 150

FIGURE 16. Projected water-level declines, 1980 to 2020, for the central High Plains resulting from pumpage for management strategy 2.

about 180 ft. Water levels are projected to decline more 

than 100 ft in 1,700 mi2. About one-half (24,000 mi2) of 

the central High Plains is projected to have declines of 

more than 10 ft. The average water-level decline for 

management strategy 2 would be 22 ft.

The total volume of water projected to be removed 

from storage in the central High Plains from 1980 to

2020 under management strategy 2 would be 121 

million acre-ft. This would be 88 percent of the simulated pumpage. The remaining 12 percent of the pumpage would be supplied primarily by decreased discharge 

to or increased recharge from streams. The average 

saturated thickness for management strategy 2 is projected to be 116 ft by 2000 and 107 ft by 2020. The
EFFECTS OF FUTURE GROUND-WATER PUMPAGE ON THE HIGH PLAINS AQUIFER E27

median saturated thickness is projected to be 96 ft by 

2000 and 87 ft by 2020.

COMPARISON OF STRATEGIES

Projected water-level declines generally would be 

smallest for management strategy 2. South of the 

Kansas-Oklahoma State line, the projected water-level 

declines would be largest for the baseline strategy (fig. 

13). North of this line, projected water-level declines 

would be largest for management strategy 1 (fig. 15). 

The greater water-level declines for management 

strategy 1 compared to the baseline strategy north of 

the Kansas-Oklahoma State line would be due to more 

pumpage resulting from increased irrigated acreage. 

Throughout the central High Plains, the projected 

water-level declines resulting from managementstrategy-2 pumpage (fig. 16) would be considerably less 

than those resulting from management-strategy-1 

pumpage (fig. 15). A decrease in pumpage between 

management strategy 1 and management strategy 2 

was simulated for all pumping periods from 1980 to 

2020; this resulted in a uniform decrease in projected 

water-level declines.

The difference in saturated thickness by 2020 between management strategy 2 and the baseline strategy 

is shown in figure 17. In Texas and Oklahoma, there 

would be three areas totaling 500 mi2 where more than 

50 ft of saturated thickness would be saved as a result 

of the mandatory decrease in water use in management 

strategy 2. The maximum difference in saturated 

thickness between management strategy 2 and the 

baseline strategy would be 68 ft. The difference in 

saturated thickness would exceed 25 ft in 4,250 mi2 

and 10 ft in 6,800 mi2. In Kansas, there would be an 

area where saturated thickness would be greater for the 

baseline strategy than for management strategy 2. The 

maximum such difference between management 

strategy 2 and the baseline strategy would be 46 ft. The 

decreased saturated thickness between management 

strategy 2 and the baseline strategy would exceed 25 

ft in 1,000 mi2 and 10 ft in 2,300 mi2. The area where 

saturated thickness would be greater for the baseline 

strategy corresponds to pumpage Region VII and 

would be the result of larger simulated pumpage for 

management strategy 2 than for the baseline strategy. 

Total management-strategy-2 pumpage in Region VII 

would be 7.1 million acre-ft more than the baselinestrategy pumpage (table 2). Much of the map shows less 

than 10 ft difference in 2020 saturated thickness between strategies; the average difference in this area is 

only 0.11 ft.

The average projected saturated thickness by 2020

resulting from baseline-strategy pumpage would be 104 

ft with 550 million acre-ft of drainable water remaining 

in storage. During the projection period, 1980 to 2020, 

138 million acre-ft of water would be removed from 

storage. With management-strategy-1 pumpage, the 

average projected saturated thickness by 2020 would be 

100 ft, and 530 million acre-ft of drainable water would 

remain in storage. This would be a 157-million acre-ft 

decrease in storage from 1980. The projected change in 

storage from 1980 to 2020 resulting from managementstrategy-2 pumpage would be 121 million acre-ft. With 

management strategy 2, 560 million acre-ft of drainable 

water is projected to remain in storage by 2020 with an 

average saturated thickness of 107 ft. The difference in 

storage between management strategy 2 and the 

baseline strategy would be about 17 million acre-ft.

NORTHERN HIGH PLAINS

The northern High Plains consists of 96,500 mi2 in 

Colorado, Kansas, Nebraska, South Dakota, and 

Wyoming north about lat 39 ° N. The northern High 

Plains constitutes 55 percent of the entire High Plains. 

From predevelopment to 1980, 26 percent of the total 

ground water pumped from the High Plains aquifer was 

pumped from the northern High Plains.

The northern High Plains was divided into 16 regions 

with different pumpage estimates as shown in figure 

18. Note that Region VII has two parts. Pumpage 

estimates for 1980 to 2020 are shown in table 3. Pumpage estimates were available for 1985, 1990, 2000, and 

2020 for all three management strategies for Regions 

I through VII (Young and others, 1982; Buller, 1982) 

and all years from 1980 to 2020 for the baseline strategy 

for Regions XII through XVI (Dayle Williamson, 

Nebraska Natural Resources Commission, written commun., August 1983). A linear interpolation was made 

between years for which pumpage was available. Pumpage projections were made during this study for 

Regions VIII through XI. Baseline-strategy pumpage 

estimates for Regions VIII through XI were the product of assumed water application and irrigated acreage 

for selected years. For each region, the 1980 irrigated 

acreage and application were based on actual data 

(Heimes and Luckey, 1983; Thelin and Heimes, in press). 

The projected water application, acreage, and baselinestrategy pumpage for Regions VIII-XI are summarized 

in table 4. Projections of pumpage were made for 2000 

and 2020 for all four regions (VIII-XI). In addition, projections of pumpage were also made for 1985 and 1990 

for Region XI to provide more detail. A linear interpolation was done between the years for which pumpage was 

projected.
E28

104C

! 

j

I 

39°!

103

REGIONAL AQUIFER-SYSTEM ANALYSIS

102° 101° 100° 99°

36° j 

35° -

EXPLANATION

Saturated-thickness difference, in feet

(Management strategy two minus baseline)

Less than -25

-25 to -10

-10 to+10 =

+10 to +25 

+25 to +50 

More than +50

FIGURE 17. Difference in projected saturated thickness by 2020 between management strategy 2 and the baseline strategy for the central 

High Plains. Decrease in difference indicates that management strategy 2 results in less saturated thickness than does baseline strategy; 

increase in difference indicates that management strategy 2 results in more saturated thickness than does baseline strategy.

Pumpage for 1980, 1985, 1990, 2000, and 2020 for 

regions VIII through XI also was estimated for management strategy 1 and management strategy 2. 

Management-strategy-1 pumpage was assumed to be 

the same as the baseline-strategy pumpage.

Management-strategy-2 pumpage was assumed to be 

equal to baseline-strategy pumpage for 1980, 90 percent 

of baseline-strategy pumpage for 1985, 80 percent of 

baseline-strategy pumpage for 1990, and 70 percent of 

the baseline-strategy pumpage for 2000 and 2020.
EFFECTS OF FUTURE GROUND-WATER PUMPAGE ON THE HIGH PLAINS AQUIFER E29

39° j

Aquifer boundary 

COLORAD

Model

EXPLANATION

IV Pumpage region and 

number in table 3

FIGURE 18. Regions for which pumpage projections were available for the northern High Plains.

Much more detailed pumpage projections were 

available for the High Plains in Nebraska (Dayle 

Williamson, Nebraska Natural Resources Commission, 

written commun., August 1983) than were available for 

the other States. Annual pumpage estimates were made 

to 2020 by the Economic Development Administration 

study investigators for several ground-water flow 

models which together covered most of the High Plains 

aquifer in Nebraska. The nodes in these models ranged 

in size from 1 to 25 mi2. The pumpage estimates from 

these models were aggregated to the 100-mi2 nodes 

during this study. Pumpage estimates for the Regions 

outside of Nebraska were distributed to model nodes 

as described in the section on the southern High Plains.

Regions XII through XVI are Nebraska economic 

regions defined in the Economic Development Administration study (High Plains Associates, 1982; High 

Plains Study Council, 1982) and are used here for summary purposes only. As noted above, detailed projections of pumpage were available for Nebraska; the data

presented in table 3 are a summary of that information. 

The projected pumpage for Regions XII through XVI 

would be identical for the baseline strategy and management strategy 1 because "***projected demand for 

Strategy 1 did not differ significantly from the 

Baseline" (Nebraska Natural Resources Commission, 

1981, p. 29). For management strategy 2, the projected 

pumpage for Nebraska was assumed to be equal to 

management-strategy-1 pumpage for 1980, 90 percent 

of management-strategy-1 pumpage for 1985, 80 percent of management-strategy-1 pumpage for 1990, and 

70 percent of management-strategy-1 pumpage for 2000 

and 2020. The percentages varied linearly between the 

specified years. These decreases are comparable to 

management-strategy-2 pumpage decreases in regions 

outside of Nebraska.

The projected pumpage by management strategy is 

summarized in figure 19. There would be a slight increase in pumpage between the baseline strategy and 

management strategy 1 for all time periods except 2005
E30 REGIONAL AQUIFER-SYSTEM ANALYSIS 

TABLE 3. Simulated pumpage, 1980 to 2020, by strategy and region for the northern High Plains

Region Simulated pumpage,

Baseline strategy 

I..........

II.........

III........

IV.........

V..........

VI.........

VII........

VIII.......

IX.........

X..........

YT

YTT

YTTT

XIV........

XV.........

XVI........

Total. ...

Management strategy 

I..........

II.........

III........

IV.........

V..........

VI.........

VII. .......

VIII.......

TV

YT

YT T

YTTT

XIV........

XV.........

XVI........

Total....

Management strategy 

I..........

II.........

III........

IV.........

V..........

VI.........

VII........

VIII.......

TV

YT

YTT

YTTT

XIV........

XV.........

XVI........

Total....

1980- 

1984

31 

128 

194 

283 

202 

440 

109 

14

24 

7 

17 

204 

591 

1,060 

2,050 

1,340

6,694

1 

32 

129 

194 

284 

280 

419 

104 

14

24 

7 

17 

204 

591 

1,060 

2,050 

1,340

6,749

2 

30 

120 

183 

266 

263 

394 

99 

13

23 

7 

16 

190 

552 

992 

1,916 

1,253

6,317

1985- 

1989

31 

128 

178 

293 

184 

381 

90 

14

27 

8 

19 

242 

902 

1,381 

2,278 

1,566

7,722

31 

127 

185 

290 

275 

354 

86 

14

27 

8 

19 

242 

902 

1,381 

2,278 

1,566

7,785

27 

109 

155 

249 

229 

307 

74 

12

23 

7 

17 

207 

771 

1,181 

1,947 

1,339

6,654

in thousands of acre-feet per

1990- 

1994

31 

127 

172 

304 

161 

291 

73 

14

28 

8 

22 

264 

1,069 

1,621 

2,492 

1,897

8,574

31 

124 

187 

294 

267 

280 

77 

14

28 

8 

22 

264 

1,069 

1,621 

2,492 

1,897

8,675

24 

97 

135 

229 

192 

220 

60 

11

22 

7 

17 

206 

834 

1,265 

1,944 

1,479

6,742

1995- 

1999

31 

128 

171 

315 

127 

242 

58 

13

27 

8 

22 

295 

1,269 

1,833 

2,765 

2,216

9,520

30 

121 

182 

300 

242 

243 

69 

13

27 

8 

22 

295 

1,269 

1,833 

2,765 

2,216

9,635

23 

89 

124 

217 

166 

179 

51 

9

20 

6 

16 

215 

927 

1,338 

2,018 

1,617

7,015

2000- 

2004

31 

123 

163 

320 

114 

200 

46 

12

26 

7 

22 

324 

1,472 

1,017 

2,836 

2,417

9,130

29 

117 

175 

301 

216 

209 

65 

12

26 

7 

22 

324 

1,472 

1,017 

2,836 

2,417

9,245

22 

83 

116 

209 

144 

146 

45 

8

18 

5 

15 

227 

1,031 

712 

1,985 

1,692

6,458

year, for

2005- 

2009

31 

111 

148 

513 

114 

169 

38 

11

25 

7 

23 

356 

1,582 

813 

2,994 

2,670

9,605

29 

110 

165 

296 

186 

181 

63 

12

25 

7 

23 

356 

1,582 

813 

2,994 

2,670

9,512

21 

79 

113 

206 

130 

127 

44 

8

18 

5 

16 

249 

1,108 

569 

2,096 

1,869

6,658

the indicated period

20 ID2014

30 

100 

132 

311 

103 

137 

30 

11

25 

7 

23 

391 

1,682 

905 

3,122 

2,898

9,907

29 

103 

154 

290 

157 

152 

62 

11

25 

7 

23 

391 

1,682 

905 

3,126 

2,898

10,015

21 

76 

111 

204 

115 

107 

44 

8

17 

5 

16 

274 

1,178 

633 

2,188 

2,028

7,025

2015- 

2019

30 

88 

116 

307 

103 

105 

22 

11

24 

7 

24 

424 

1,766 

974 

3,202 

3,036

10,239

28 

95 

144 

285 

128 

124 

61 

11

24 

7 

24 

424 

1,766 

974 

3,202 

3,036

10,333

20 

73 

109 

202 

100 

87 

43 

8

17 

5 

17 

297 

1,236 

682 

2,242 

2,125

7,263
EFFECTS OF FUTURE GROUND-WATER PUMPAGE ON THE HIGH PLAINS AQUIFER E31 

TABLE 4. Projected acreage, water application, andpumpage for northern High Plains Regions VIII through XI for the baseline strategy

Region Year

VIII.......... 1980

2000

2020

TY 1 QRD

2000

2020 

X............. 1980

2000

2020

YT 1 QRn

1985

1990

2000

2020

Irrigated 

acres

10,800

10,800

10,800 

17,900

23,600

23,600 

5,100

6,700

6,700 

11,500

13,800

16,600

18,200

21,900

Water application, 

in feet

1 in

1.20

1.10 

i ?n

1.10

1.00 

i ?=>

1.15

1.05 

i in

1.30

1.30

1.20

1.10

Pumpage , in 

acre-feet

14,000

13,000

12,000 

21,500

26,000

23,600 

6,400

7,700

7,000 

15,000

17,900

21,600

21,800

24,100

to 2009. The total volume pumped for the baseline 

strategy would be 357 million acre-ft, whereas the total 

volume pumped for management strategy 1 would be 

360 million acre-ft. There would be less than a 1-percent 

difference in pumpage between the two strategies. The 

total volume pumped for management strategy 2 would 

be 271 million acre-ft. This would be about 76 percent 

of the volume pumped for the baseline strategy. 

Management-strategy-2 pumpage would be significantly less than the baseline-strategy pumpage for all 

periods.

The water levels in the northern High Plains aquifer 

are largely controlled by streams (Luckey and others, 

1986, p. 37-38). Future pumpage could change the relation between streams and aquifer to the extent that 

streams will no longer control the water levels. Simulations were made to see if streams would cease flowing 

with the pumpage projected for the northern High 

Plains. Simulated pumpage would be sufficient near the 

South Loup River and parts of the Elkhorn and 

Republican Rivers to deplete the base flow of parts of

these streams after 1990. To properly simulate the 

hydrologic conditions, the parts of the streams where 

base flow would be depleted were removed from the 

model in 1990 and then the simulations were continued 

to 2020. The South Loup River was removed from the 

model upstream from its confluence with the Middle 

Loup River, the Republican River and its tributaries 

were removed from the model west of long 101 ° W., and 

the Elkhorn River was removed from the model west 

of long 98° W.

The model, which was developed to compute water 

levels within large areas, cannot provide detailed information about streamflow capture within small areas. 

Streamflow capture, defined as decreased streamflow 

caused by pumping from wells, may include both direct 

depletion from the stream and decrease in ground-water 

flow to the stream. To provide more quantitative information about streamflow capture, the ground-water 

flow equation was solved directly for streamflow capture (Jenkins, 1970) using assumptions that are 

reasonable for the northern High Plains.
E32 REGIONAL AQUIFER-SYSTEM ANALYSIS

12

LLJ

CC

LU

a.

O 

to

13 

CLEXPLANATION

,1 Baseline strategy

i

Management strategy 1 

Management strategy 2

Wffij

i.

1980-84 1985-89 1990-94 1995-99 2000-04 2005-09 2010-14 

FIGURE 19. Simulated pumpage for the northern High Plains by management strategy.

2015-19

Streamflow capture was calculated on the basis of the 

average aquifer-parameter estimates for the northern 

High Plains aquifer determined by model calibration 

{Luckey and others, 1986). Values of the aquifer 

parameters were hydraulic conductivity, 53 ft/d; 

saturated thickness, 340 ft; and specific yield, 0.152. 

The calculated streamflow capture shown in figure 20 

assumes one well pumping 130 acre-ft/yr on every other 

quarter section (two wells per square mile). This assumed density of irrigation is not an average for the entire northern High Plains, but is typical of the more 

intensely irrigated areas. The data in figure 20 represent the calculated streamflow capture, per mile of 

stream, at the end of 40 years of pumping. Most of the 

streamflow capture would be caused by pumpage from 

wells within 10 mi of the stream and virtually all the 

streamflow capture would be caused by pumpage from 

wells within 20 mi of the stream. The difference between 

streamflow capture at the end of the 3-month irrigation

Nine months after end 

of irrigation season

10 20 30 

DISTANCE FROM RIVER, IN MILES

FIGURE 20. Hypothetical streamflow capture for the northern 

High Plains computed based on estimated average aquifer 

parameters and two irrigation wells per square mile withdrawing 130 acre-ft of water per year.
EFFECTS OF FUTURE GROUND-WATER PUMPAGE ON THE HIGH PLAINS AQUIFER E33

season and 9 months later would be caused by pumpage 

from wells within 3 mi of the stream. Streamflow capture would be directly related to pumpage, particularly within a few miles from the stream. Because the 

model described here has 10-mi grid spacing, a more 

detailed model would be needed to simulate management strategies to regulate streamflow capture.

BASELINE STRATEGY

The projected water-level declines from 1980 to 2020 

resulting from baseline-strategy pumpage are shown in 

figure 21. The projected water-level declines for the 

northern High Plains would range from less than 10 ft

in about one-half of the northern High Plains to more 

than 200 ft in two isolated areas. The maximum waterlevel decline from 1980 to 2020 would be 230 ft over one 

model node (100 mi2). Water levels are projected to 

decline more than 100 ft in several areas of Nebraska 

and Colorado totaling 9,700 mi2 . Water levels are projected to decline more than 25 ft in parts of all States 

in the northern High Plains by 2020. The median projected water-level decline from 1980 to 2020 for the 

baseline strategy would be 14 ft. This means that onehalf of the area of the northern High Plains is projected 

to have water-level declines of more than 14 ft from 1980 

to 2020. The average water-level decline from 1980 to 

2020 for the baseline strategy would be 36 ft. The

EXPLANATION

Water- level change, 

in feet

Decline less than 10

-10 to -25

-25 to -50

-50 to -100

-100 to-150

-150 to-200 

Decline more than 200

FIGURE 21. Projected water-level declines, 1980 to 2020, for the northern High Plains resulting from pumpage for the baseline strategy.
E34 REGIONAL AQUIFER-SYSTEM ANALYSIS

average water-level decline is larger than the median 

decline because the average is influenced more by the 

larger water-level declines than is the median. The projected water-level declines from 1980 to 2020 would be 

in addition to the declines, in excess of 25 ft, that had 

already occurred in the northern High Plains by 1980 

(Luckey and others, 1981).

Large water-level declines are projected near parts of 

the Elkhorn, South Loup, and Republican Rivers. These 

water-level declines would occur because projected 

pumpage in these areas would be large enough to 

deplete the normal base flow of these streams early in 

the projection period (1980-2020). Along the rest of the 

major streams, water-levels are projected to decline by 

less than 10 ft because pumpage near the streams would 

be supplied mostly by streamflow capture. The total 

volume of water that would be removed from storage 

during this 40-year simulation is projected to be 291 

million acre-ft. The difference between the volume of 

water that would be removed from storage (291 million 

acre-ft) and the volume of water that would be pumped 

(357 million acre-ft) would come primarily from decreased discharge to or increased recharge from the 

streams. By 2020, the total projected rate of streamflow 

capture estimated by the model for the entire northern 

High Plains would be 2,750 ft3/s. By 2020, the estimated maximum streamflow capture would be about 

18 ft3/s per mile of stream and the average would be 

about 1.4 ft3/s per mile. The maximum streamflow capture calculated by the model would be more than the 

hypothetical streamflow capture shown in figure 20, and 

the average would be much less than that shown in 

figure 20. However, figure 20 is based on the average 

estimated aquifer parameters and about 40-percent density of irrigation (two 130-acre center-pivot systems per 

640 acres). As shown in figure 3, the maximum density 

of irrigation in the northern High Plains is considerably 

more than 40 percent and the average is much less than 

40 percent. Hence, the streamflow capture calculated 

by the model appears to be consistent with that 

calculated by directly solving the ground-water flow 

equation for streamflow capture.

The projected saturated thickness remaining in the' 

northern High Plains by 2020 is shown in figure 22. 

There would be a large area (1,650 mi2 ) in central 

Nebraska where the projected saturated thickness 

would exceed 800 ft. The projected saturated thickness 

would exceed 200 ft in 34,400 mi2 in parts of 

Nebraska, South Dakota, and Wyoming. In 40 percent 

of the northern High Plains, the saturated thickness is 

projected to be less than 100 ft by 2020. The median 

saturated thickness projected by 2020 for the baseline 

strategy would be 138 ft. The average saturated thickness is projected to be 217 ft by 2020, but this average

is influenced by the large saturated-thickness area of 

central Nebraska. The average saturated thickness in 

the areas with less than 200 ft of saturated thickness 

would be 77 ft.

MANAGEMENT STRATEGY 1

The projected pumpage from 1980 to 2020 for management strategy 1 would be 3 million acre-ft (1 percent) 

greater than that for the baseline strategy. 

Management-strategy-1 pumpage would be greater 

than baseline-strategy pumpage in parts of Colorado 

and Kansas; management-strategy-1 pumpage would be 

identical to baseline-strategy pumpage in Nebraska, 

South Dakota, and Wyoming. Simulated water-level 

declines from 1980 to 2020 would be virtually identical 

for management strategy 1 and the baseline strategy; 

thus, simulated declines for management strategy 1 are 

not shown. The average water-level decline from 1980 

to 2020 would be 36 ft for management strategy 1, and 

the median decline would be 14 ft. For the 159 nodes 

(17 percent of the area of the model) where the water 

levels would be different between the baseline strategy 

and management strategy 1, the water-level declines 

would average 0.2 ft more for management strategy 1 

than for the baseline strategy.

MANAGEMENT STRATEGY 2

The projected water-level declines from 1980 to 2020 

resulting from management-strategy-2 pumpage are 

shown in figure 23. Even with large mandatory 

decreases in water use, significant water-level declines 

would still occur in the northern High Plains from 1980 

to 2020. The maxiumum water-level decline for management strategy 2 would be 168 ft. There would be 

numerous areas totaling 5,400 mi2 where water levels 

are projected to decline more than 100 ft from 1980 to 

2020. Water levels are projected to decline more than 

10 ft in 47,000 mi2 in parts of all five States. The 

average water-level decline from 1980 to 2020 in the 

northern High Plains for management strategy 2 is projected to be 28 ft and the median water-level decline is 

projected to be 11 ft.

The total volume of water that would be removed 

from storage from 1980 to 2020 for management 

strategy 2 is projected to be 228 million acre-ft. Most 

(83 percent) of the 43-million-acre-ft difference between 

pumpage and water removed from storage would come 

from streamflow capture. The total projected 

streamflow capture for the northern High Plains by 

2020 for management strategy 2 would be 1,700 ft3/s.
EFFECTS OF FUTURE GROUND-WATER PUMPAGE ON THE HIGH PLAINS AQUIFER E35

EXPLANATION

Saturated thickness, 

in feet

0 to 100 

100 to 200 

200 to 400 i

400 to 600 

600 to 800 

More than 800

FIGURE 22. Projected saturated thickness by 2020 in the northern High Plains resulting from pumpage for the baseline strategy.

The average streamflow capture would be 0.86 ft3/s 

per mile of stream, and the maximum would be 18 ft3/s 

per mile.

The average projected saturated thickness by 2020 

for management strategy 2 would be 225 ft, but this

is influenced by the large saturated thickness in central Nebraska where the projected saturated thickness 

would exceed 800 ft in places. The median simulated 

saturated thickness projected by 2020 for management 

strategy 2 would be 152 ft.
E36 REGIONAL AQUIFER-SYSTEM ANALYSIS

Aquifer boundary

«

COLORADO

EXPLANATION

Water-level change, 

in feet

Decline less than 10 

-10 to -25

-25 to -50

-50 to -100

Decline more than 100

FIGURE 23. Projected water-level declines, 1980 to 2020, for the northern High Plains resulting from pumpage for management strategy 2.

COMPARISON OF STRATEGIES

The water-level declines projected for the baseline 

strategy and management strategy 1 would be virtually identical for the entire northern High Plains, but 

declines resulting from management-strategy-2 pumpage

would be much less. The average water-level decline 

from 1980 to 2020 for the baseline strategy would be 

36 ft, and the average decline for management strategy 

2 would be 28 ft. The median water-level declines for 

the same period would be 14 ft for the baseline strategy 

and 11 ft for management strategy 2.
EFFECTS OF FUTURE GROUND-WATER PUMPAGE ON THE HIGH PLAINS AQUIFER E37

The difference in saturated thickness between management strategy 2 and the baseline strategy is shown 

in figure 24. More than 50 ft of saturated thickness 

would be saved in several areas totaling 750 mi2 in 

eastern Colorado and eastern Nebraska as a result of 

the mandatory decrease in water use in management 

strategy 2. The maximum difference in saturated thickness by 2020 between management strategy 2 and the 

baseline strategy would be 67 ft. The difference in 

saturated thickness would exceed 10 ft in 27 percent 

of the northern High Plains. Most of this area is between the Republican and Platte Rivers and north of 

the Loup River system. Although the average difference 

in saturated thickness between management strategy 

2 and the baseline strategy by 2020 would be almost 

8 ft, the median difference only would be slightly more

than 1 ft. In areas with differences in saturated thickness of less than 10 ft, the average difference is 1.34 ft.

In addition to the difference in saturated thickness, 

streamflow capture also would be decreased. The decrease in streamflow capture between the baseline strategy and management strategy 2 would be 19 million 

acre-ft during the 40 years, and by 2020, streamflow for 

management strategy 2 would be 1,050 ft3/s more than 

that for the baseline strategy.

As a result of baseline-strategy pumpage, the volume 

of drainable water in storage in the northern High 

Plains is projected to be 1,810 million acre-ft in 2020. 

Virtually the same volume of water would remain in 

storage assuming management-strategy-1 pumpage. 

About 63 million acre-ft more water would remain in 

storage by 2020 for management strategy 2 than for

SOUTH >4> DAKOTA

Aquifer boundary 

COLORADO

EXPLANATION

Saturated thickness difference, in feet

(Management strategy two minus baseline)

Less than 10 

10 to 25

: 25 to 50 

More than 50

FIGURE 24. Difference in projected saturated thickness by 2020 between management strategy 2 and the baseline strategy for the northern High Plains.
E38 REGIONAL AQUIFER-SYSTEM ANALYSIS

the baseline strategy. Although this is only 3.5 percent 

of the water projected to remain in storage by 2020, it 

represents an 8.7-year supply of water at the 2015-2019 

management-strategy-2 withdrawal rate.

PROJECTED WELL YIELDS

Water-level declines increase the cost of pumping and 

decrease well yields. Gutentag and others (1984, p. 47) 

reported that well yield

"***required to irrigate a specific number of acres will depend on 

the crop and soil type, climate, and irrigation system. Typically, 

one well capable of producing 250 gal/min can irrigate 40 acres; one 

well capable of producing 750 gal/min can irrigate 160 acres and 

effectively operate a quarter-section center-pivot system. Of course, 

it is possible to use several wells operated as a unit to obtain the 

desired yield. But, at some point, well yields will become a constraint 

to irrigation development because of the costs associated with drilling, operating, and maintaining additional wells." 

Determining potential well yields was the first step 

in calculating the probable well yields. Potential well 

yields in the High Plains were calculated by solving 

the Theis (1935) equation with the water-table correction (Jacob, 1963). The hypothetical well used in the 

calculation was assumed to be pumped continuously for 

90 days (irrigation season). The well was assumed to 

have an effective radius of 1.25 ft because irrigation 

wells commonly are constructed by gravel packing a 

16-in. screen in a 30-in. hole. The water level in the 

aquifer adjacent to the well at the end of the 90-day 

pumping period was assumed to be 15 ft above the base 

of the aquifer. Interference from nearby wells was 

neglected in the calculation, because well spacing in the 

High Plains normally is about 0.5 mi and interference 

usually is small. These assumptions are the same as 

those used by Lindner-Lunsford and Borman (1985) 

for the High Plains in Colorado but are somewhat different from those used by Gutentag and others (1984, 

p. 47). The potential well yield was calculated by the 

following equation based on the above described 

assumptions.

= 0.0326JC(m2-225) 

log/m/C/Sy)+4.8626

(1)

where Qp is the potential well yield in gallons per

minute;

K is the hydraulic conductivity, in feet per day; 

m is the saturated thickness, in feet; and 

Sy is the specific yield (dimensionless). 

Probable well yield was then calculated by multiplying the potential well yield by 0.65 to account for the 

inherent inefficiencies of constructed wells. The probable well yield is given by

Q 0.0212JC(m2 -225) (2)

where Q is the probable well yield in gallons per minute 

and the other symbols are as defined above. The probable well yield was calculated for each model node of 

the southern, central, and northern High Plains models 

using equation 2.

Probable well yields for the High Plains by 2020, 

based on projected saturated thickness resulting from 

baseline-strategy pumpage, are shown in figure 25. 

Probable well yields in 2020 would be greatest in the 

northern High Plains and least in the southern High 

Plains.

The percentage change in probable well yields from 

1980 to 2020 for the High Plains is shown in figure 26. 

The change-in-yield map is based on the difference in 

probable well yields in 1980 and that projected by 2020 

as a result of baseline-strategy pumpage. As expected, 

the largest percentage changes would occur where the 

projected water-level change from 1980 to 2020 is large 

and the 1980 saturated thickness was small. Decreases 

in probable well yields are projected to be greatest in 

the southern High Plains and least in the northern High 

Plains.

SOUTHERN HIGH PLAINS

Throughout 80 percent of the southern High Plains, 

the probable well yields by 2020 (fig. 25) are projected 

to be less than 250 gal/min although there would be 

several areas totaling 2,050 mi2 where the probable 

well yields are projected to exceed 750 gal/min. The 

largest of these areas, in the east-central part of the 

southern High Plains, had significant saturated 

thickness in 1980 (Weeks and Gutentag, 1981) and very 

little projected water-level decline from 1980 to 2020, 

so the probable well yields by 2020 would be similar to 

those in 1980. The average probable well yield by 2020 

for the southern High Plains on the basis of projected 

pumpage for the baseline strategy would be 230 gal/min, 

but the median would be much less. The average for the 

area with probable well yields of less than 250 gal/min 

would be only 32 gal/min. Similar results were obtained 

for management strategy 1. For management strategy 

2, the average probable well yield for the southern High 

Plains by 2020 is projected to be 290 gal/min.

In about 38 percent of the southern High Plains, probable well yields are projected to decrease by more than 

75 percent from 1980 to 2020 as a result of baselinestrategy pumpage (fig. 26). In about 56 percent of the 

area, well yields are projected to decrease by more than
EFFECTS OF FUTURE GROUND-WATER PUMPAGE ON THE HIGH PLAINS AQUIFER E39

43° -

41° __

39°

Probable well yield, 

in gallons per minute

Less than 250 

250 to 750 

More than 750

FIGURE 25. Probable well yields by 2020 for the High Plains resulting from pumpage for the baseline strategy.
E40

10G°

REGIONAL AQUIFER-SYSTEM ANALYSIS

104° 103° 102° 101° 100° 99° 98° 97°

43°

42° U

41° U_

40° k

Change in probable well 

yeild, in percent

Increase more than 25 

+25 to -25 

-25 to -75 

Decrease more than 75

FIGURE 26. Percentage changes in probable well yields, 1980 to 2020, for the High Plains resulting from pumpage

for the baseline strategy.
EFFECTS OF FUTURE GROUND-WATER PUMPAGE ON THE HIGH PLAINS AQUIFER E41

25 percent by 2020. In two areas totaling 620 mi2, the 

probable well yields are projected to increase by more 

than 25 percent by 2020 because water levels are projected to rise in these areas (fig. 6).

CENTRAL HIGH PLAINS

Most of the western part of the central High Plains 

is projected to have well yields of less than 250 gal/min 

by 2020 as a result of baseline-strategy pumpage (fig. 

25). Significant water-level declines from 1980 to 2020 

are projected for this area (fig. 13), and these declines, 

combined with small saturated thickness in 1980 

(Weeks and Gutentag, 1981), are projected to decrease 

probable well yields to less than 250 gal/min. East of 

about long 101 °30' W., projected well yields by 2020 

generally would be greater than 750 gal/min. Although 

this area is projected to have significant water-level 

declines from 1980 to 2020, the saturated thickness in 

1980 generally was more than 200 ft and the well yields 

are projected to remain greater than 750 gal/min by 

2020. Wells in the central High Plains are projected to 

yield less than 250 gal/min in about 47 percent of the 

area and more than 750 gal/min in 32 percent of the 

area. For the baseline strategy, the median probable 

well yield by 2020 is projected to be 370 gal/min. For 

management strategy 1, the median is projected to be 

350 gal/min, whereas for management strategy 2, the 

median is projected to be 430 gal/min.

Probable well yields in the central High Plains as a 

result of baseline-strategy pumpage are projected to 

decrease by more than 75 percent from 1980 to 2020 

in several areas (fig. 26), most of which are west of long 

101 ° W. Probable well yields are projected to decrease 

by 25-75 percent in about 15,000 mi2 and by more 

than 75 percent in 7,050 mi2. Many of the largest 

percentage changes in probable well yield are projected 

to occur in those areas which had less than 100 ft of 

saturated thickness in 1980.

NORTHERN HIGH PLAINS

In the northern High Plains, well yields are projected 

to be greater than 750 gal/min in 58 percent of the area 

by 2020 (fig. 25). The only large areas in the northern 

High Plains with projected well yields of less than 250 

gal/min would be south of lat 40°30' N. and between 

the North and South Platte Rivers in Colorado and 

Nebraska. In the northern High Plains, significant 

decreases in probable well yields are projected south of 

the Platte Rivers (fig. 26). North of the Platte Rivers, 

significant decreases are projected east of long 99° W.

and in the vicinity of long 103° W. These changes are 

in areas that had substantial irrigation in 1978 (fig. 3). 

The saturated thickness is so large throughout much 

of the northern High Plains that even with large projected water-level declines from 1980 to 2020, well yields 

will still exceed 750 gal/min by 2020 (fig. 25).

SUMMARY AND CONCLUSIONS

The High Plains is one of the major irrigated agricultural areas of the United States and in 1980 accounted 

for more than 20 percent of the irrigated land and about 

30 percent of the ground water pumped for irrigation 

in the Nation. Throughout much of the High Plains, the 

rate of withdrawal of ground water for irrigation exceeds the natural rate of replenishment and, as a consequence, water-level declines have occurred. The U.S. 

Geological Survey began a regional geohydrologic study 

of the 174,000-mi2 High Plains aquifer in 1978. One of 

the objectives of the study was to evaluate the effects 

of future pumpage on the High Plains aquifer.

The High Plains aquifer system was divided into 

three parts: the southern High Plains, the central High 

Plains, and the northern High Plains; each part was 

simulated separately. The models of each part were first 

calibrated so that they could adequately simulate 

historical hydrologic conditions. The models were 

calibrated by comparing simulated and measured water 

levels or water-level changes for predevelopment and 

development periods. The predevelopment-period 

models simulated the system prior to large-scale irrigation development; the development-period models 

simulated the system after the beginning of large-scale 

irrigation development. Once the models were 

calibrated, they were used to project the hydrologic effects of estimated future ground-water pumpage.

Three different water-management strategies, as 

defined by an economic study of the High Plains region 

(High Plains Associates, 1982), were simulated. The 

baseline strategy assumed continuation of current 

(1980) economic trends and governmental policies. 

Management strategy 1 assumed voluntary adoption 

of new techniques to decrease irrigation water use. 

Management strategy 2 assumed an additional mandatory decrease in water use from management 

strategy 1. The total pumpage simulated for 1980 to 

2020 was 628 million acre-ft for the baseline strategy, 

647 million acre-ft for management strategy 1, and 497 

million acre-ft for management strategy 2. Pumpage increased between the baseline strategy and management strategy 1 because increased irrigated acreage in 

management strategy 1 more than offset the decreased 

per-acre water use for this strategy. The simulated
E42 REGIONAL AQUIFER-SYSTEM ANALYSIS

12

10

EXPLANATION

Southern High Plains 

Central High Plains 

Northern High Plains

Q_

D

C/J

1980-84 1985-89 1990-94 1995-99 2000-04 2005-09 2010-14 2015-19 

FIGURE 27. Simulated pumpage for the baseline strategy by High Plains model region.

pumpage for the baseline strategy by High Plains model 

region is shown in figure 27.

In the southern High Plains, the total simulated pumpage from 1980 to 2020 would be 113 million acre-ft for 

the baseline strategy, 109 million acre-ft for management strategy 1, and 88 million acre-ft for management 

strategy 2. Projected water-level declines from 1980 to 

2020 resulting from baseline-strategy pumpage would 

exceed 150 ft in parts (700 mi2) and exceed 10 ft 

throughout much of the southern High Plains. During 

the 40 years from 1980 to 2020, 101 million acre-ft of 

water are projected to be removed from the southern 

High Plains aquifer, and by 2020, more than one-half 

of the area would have less than 25 ft of saturated 

thickness remaining. Slightly more than 100 million 

acre-ft of drainable water would remain in storage compared to about 200 million acre-ft during 1980. By 2020, 

probable well yields throughout most (80 percent) of the 

southern High Plains would be less than 250 gal/min.

Projected water-level declines for the southern High 

Plains resulting from management-strategy-1 pumpage 

are similar to those projected for the baseline strategy. 

The average water-level decline would be only 1 ft less 

for management strategy 1 than for the baseline strategy.

Projected water-level declines from 1980 to 2020 

resulting from management-strategy-2 pumpage are 

significantly less than those for the baseline strategy. 

Water levels in only one small area (30 mi2) are projected to decline more than 150 ft. The average waterlevel decline from 1980 to 2020 is projected to be 7 ft 

less for management strategy 2 than for the baseline 

strategy, and saturated thickness is projected to be 25 

ft greater in 3,200 mi2 (11 percent of the area) as a 

result of the decreased water use between the baseline 

strategy and management strategy 2.

In the central High Plains, simulated pumpage from 

1980 to 2020 would be 158 million acre-ft for the baseline 

strategy, 178 million acre-ft for management strategy
EFFECTS OF FUTURE GROUND-WATER PUMPAGE ON THE HIGH PLAINS AQUIFER E43

1, and 138 million acre-ft for management strategy 2. 

Projected water-level declines from 1980 to 2020 resulting from baseline-strategy pumpage would exceed 200 

ft in about 150 mi2 (less than 1 percent of the area) and 

25 ft in about one-third of the area. About 138 million 

acre-ft of water are projected to be removed from storage 

as a result of 40 years of baseline-strategy pumpage; the 

average saturated thickness will be about 100 ft by 2020. 

About 550 million acre-ft of drainable water would remain in storage in 2020 assuming baseline-strategy 

pumpaga Probable well yields in the central High Plains 

would decrease by more than 25 percent from 1980 to 

2020 in 47 percent of the area, but would be more than 

750 gal/min in 32 percent of the area.

Total management-strategy-1 pumpage in the central 

High Plains would be 13 percent greater than total 

baseline-strategy pumpage. Consequently, water-level 

declines would be greater assuming management 

strategy 1.

Projected water-level declines from 1980 to 2020 

resulting from management-strategy-2 pumpage would 

be everywhere less than those resulting from management-strategy-1 pumpage. There are areas in Kansas 

where water-level declines projected for management 

strategy 2 exceed those projected for the baseline 

strategy due to an increase in irrigated acreage. For 

management strategy 2, water-level declines of more 

than 100 ft from 1980 to 2020 are projected in about 

1,700 mi2 (4 percent of the area).

In the northern High Plains, simulated pumpage from 

1980 to 2020 would be 357 million acre-ft for the baseline 

strategy, 360 million acre-ft for management strategy 

1, and 271 million acre-ft for management strategy 2. 

Projected water-level declines from 1980 to 2020 for the 

baseline strategy would exceed 200 ft in a few isolated 

areas and exceed 100 ft throughout more than 9,700 

mi2 (10 percent of the area). The average water-level 

decline from 1980 to 2020 for the baseline strategy 

would be 36 ft, and the average saturated thickness by 

2020 would be 217 ft. About 1,810 million acre-ft of 

drainable water would remain in storage in 2020 assuming baseline-strategy pumpage. Probable well yields are 

projected to decline by more than 75 percent from 1980 

to 2020 in parts of the northern High Plains. However, 

probable well yields of more than 750 gal/min by 2020 

are projected for 58 percent of the area.

Management-strategy-1 pumpage in the northern 

High Plains would be nearly identical to baselinestrategy pumpage. Consequently, the water-level 

declines from 1980 to 2020 as a result of managementstrategy-1 pumpage would be almost identical to those 

projected for the baseline.

For management strategy 2, water-level declines of 

more than 100 ft from 1980 to 2020 would occur in about

5,400 mi2 (6 percent of the area). The average waterlevel decline from 1980 to 2020 as a result of management-strategy-2 pumpage would be 8 ft less than that 

for the baseline strategy. Water-level declines for 

management strategy 2 would be at least 10 ft less than 

those for the baseline strategy in more than one-fourth 

of the northern High Plains and at least 50 ft less in 

about 750 mi2 (less than 1 percent of the area). For all 

strategies, more than 800 ft of saturated thickness are 

projected to remain in the central part of Nebraska by 

2020.

Streamflow capture is important in the northern High 

Plains aquifer. For all three strategies, the base flow of 

the South Loup River and parts of the Elkhorn and 

Republican Rivers were projected to be depleted after 

1990. For the baseline strategy, projected streamflow 

capture would be about 60 million acre-ft from 1980 to 

2020. By 2020, the baseline-strategy projected rate of 

streamflow capture would be 2,750 ft3/s. For management strategy 2, projected streamflow capture would be 

about 36 million acre-ft from 1980 to 2020. Most of the 

streamflow capture would be caused by wells within 10 

mi of the streams.

From 1980 to 2020 for all three strategies, pumpage 

will decrease in the southern and central High Plains, 

but will increase in the northern High Plains. Water 

levels will continue to decline during the 40 years as a 

result of the pumpage. Water-level declines resulting 

from baseline-strategy pumpage will exceed 200 ft in a 

few small areas of the High Plains, and water-level 

declines will exceed 100 ft in more than 15,500 mi2 . 

More than one-half of the 174,000-mi2 High Plains area 

will have water-level declines of more than 10 ft from 

1980 to 2020.

Declining water levels will decrease the rate at which 

water can be pumped. Probable well yields by 2020 are 

projected to exceed 750 gal/min in small areas of the 

southern High Plains, large parts of the central High 

Plains, and most of the northern High Plains. Probable 

well yields by 2020 are projected to be less than 250 

gal/min in most of the southern High Plains, in about 

one-half of the central High Plains, and in small parts 

of the northern High Plains.

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/, U.S. GOVERNMENT PRINTING OFFICE: 1988 573-047/66,074 REGION NO. 8