GEOHYDROLOGY OF THE HIGH PLAINS AQUIFER 

IN PARTS OF COLORADO, KANSAS, NEBRASKA, 

NEW MEXICO, OKLAHOMA, SOUTH DAKOTA,

k. TEXAS, AND WYOMING

LJ ~Y

U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1400-B
Geohydrology of the High Plains 

Aquifer In Parts of Colorado, 

Kansas, Nebraska, New Mexico, 

Oklahoma, South Dakota, 

Texas, and Wyoming

By EDWIN D. GUTENTAG, FREDERICK J. HEIMES, NOEL C. KROTHE, 

RICHARD R. LUCKEY, and JOHN B. WEEKS

HIGH PLAINS RASA PROJECT

U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1400-B

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1984
UNITED STATES DEPARTMENT OF THE INTERIOR 

WILLIAM P. CLARK, Secretary

GEOLOGICAL SURVEY 

Dallas L. Peck, Director

Library of Congress Cataloging in Publication Data

Main entry under title:

Geohydrology of the High Plains aquifer in parts of Colorado, Kansas, Nebraska, New Mexico, Oklahoma, South

Dakota, Texas, and Wyoming 

(Geological Survey Professional Paper ; 1400-B) 

Bibliography: 63 p. 

Supt. of Docs. No.: 119.16:1400-B 

1. Aquifers High Plains (U.S.) 

I. Gutentag, Edwin D., 1931-. II. Series 

GB1199.3.H53.G64 1984 553.7'9'0978 83-600268

For sale by the Branch of Distribution

U.S. Geological Survey

604 South Pickett Street

Alexandria, VA 22304
FOREWORD

THE REGIONAL AQUIFER-SYSTEM ANALYSIS PROGRAM

The Regional Aquifer-System Analysis (RASA) program was started in 1978 

after 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 

important components 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 of any changes brought about by human activities, as well as 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 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 Natural 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 Economic Development Administration was authorized by Congress in 1976. This 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. Together, these two studies will 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 will develop and propose alternative strategies to alleviate or mitigate those impacts and the U.S. Geological Survey will 

provide 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 and metric units for water chemistry measurements. The units commonly are abbreviated using'the notations shown below in parentheses. Inchpound 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 units

inch 2.54X101 millimeter

foot 3.048 x 10~ l meter

mile 1.609 kilometer

square foot (ft2) 9.29 xlO~2 square meter

acre 4.047X10" 1 hectare

square mile (mi2) 2.59 square kilometer

acre-foot (acre-ft) 1.233xlO~3 cubic hectometer

foot per day (ft/d) 3.048x 10" 1 meter per day

cubic foot per second (ft3/s) 2.832 x 10~2 cubic meter per second

gallon per minute (gal/min) 6.308x 10~2 liter per second

ton 9.072X10" 1 megagram
CONTENTS

Page

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

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

Purpose and scope ..................... 2

Physical setting ....................... 2

Physiography ...................... 2

Climate ......................... 3

Cultural setting ....................... 3

Agricultural development ............... 3

Agricultural production ................ 7

Previous hydrologic studies ................ 7

Geology .............................. 7

High Plains aquifer ..................... 8

Tertiary units ..................... 8

Quaternary units .................... 11

Depositional history ....

Bedrock .............

Permian units .......

Triassic and Jurassic units 

Cretaceous units ......

11

13

13

15

15

Page

Geology Continued 

Bedrock Continued

Tertiary units ..................... 16

Relationship between bedrock and aquifer ........ 16

Faults .......................... 16

Salt dissolution ..................... 17

Ground-water hydrology ..................... 17

Aquifer system ....................... 17

Geometry ........................ 20

Hydraulic characteristics ............... 23

Flow system ...................... 26

Water quality ........................ 34

Dissolved solids .................... 34

Sodium ......................... 38

Ground-water development ................. 40

Irrigation development ................ 40

Effects of development ................ 45

Constraints on development .............. 47

Summary and conclusions .................... 56

Selected references ....................... 59

ILLUSTRATIONS

Page

FIGURES 1-4. Maps showing:

1. Location of High Plains aquifer .......................................... 5

2. Normal annual precipitation and Class A pan evaporation in the High Plains ................ 6

3. Principal geologic units in the High Plains aquifer ................................ 10

4. Geology of bedrock units underlying the High Plains aquifer .......................... 14

5. Graph showing area of High Plains aquifer in contact with bedrock units ....................... 15

6. Map showing altitude of base of the High Plains aquifer ................................ 18

7. Diagram showing geohydrologic sections through the High Plains aquifer ....................... 19

8-15. Maps showing:

8. Water table in the High Plains aquifer, 1980 ................................... 21

9. Saturated thickness of the High Plains aquifer, 1980 ............................... 22

10. Areal distribution of hydraulic conductivity in the High Plains aquifer .................... 25

11. Areal distribution of specific yield in the High Plains aquifer ......................... 27

12. Predevelopment water table and direction of ground-water flow in the High Plains aquifer ........ 29

13. Discharge in the Platte River drainage, 1975 water year ............................ 30

14. Soil types in the High Plains ............................................ 32

15. Dissolved-solids concentration in water from the High Plains aquifer ..................... 35

16. Graph showing percentage volume of water in the High Plains aquifer exceeding indicated concentration of dissolved

solids ....................................................... 37

17-20. Maps showing:

17. Sodium concentration in water from the High Plains aquifer .......................... 39

18. Density of acreage irrigated by ground water in the High Plains, 1949 .................... 41

19. Density of acreage irrigated by ground water in the High Plains, 1964 .................... 42

20. Density of acreage irrigated by ground water in the High Plains, 1978 .................... 43

21. Graph showing acreage irrigated by ground water in the High Plains, 1949-78 .................... 44

22. Graph showing estimated ground-water pumpage from the High Plains aquifer, 1949-78 ............... 44

23. Map showing predevelopment to 1980 water-level changes in the High Plains aquifer ................ 46

24. Map showing potential well yields from the High Plains aquifer, 1980 ......................... 48

25. Diagram for classification of salinity and sodium hazards for irrigation water ..................... 50

26. Map showing generalized depth to water in the High Plains aquifer, 1980 ...................... 52

27. Map showing ground-water management areas in the High Plains ........................... 53

VII
VIII CONTENTS

TABLES

TABLE 1. Generalized section of geologic units in the High Plains ................................... 9

2. Distribution and volume of saturated material, High Plains aquifer, 1980 ......................... 24

3. Statistics on the vertical distribution of transmissivity and storage depth in the High Plains aquifer ......... 24

4. Distribution of average hydraulic conductivity in the High Plains aquifer ......................... 26

5. Hydraulic-conductivity and specific-yield values assigned to lithologic descriptions of the High Plains aquifer ..... 26

6. Distribution of average specific yield in the High Plains aquifer .............................. 26

7. Recharge estimates for the High Plains aquifer ........................................ 33

8. Distribution of drainable water in storage in the High Plains aquifer, 1980 ........................ 34

9. Chemical analyses of selected water samples from the High Plains aquifer ........................ 36

10. Chemical data from selected water samples from the High Plains aquifer ......................... 38

11. Distribution of water-level changes and volume of aquifer dewatered, High Plains aquifer, predevelopment to 1980 . 47

12. Summary of regulations controlling ground-water development from the High Plains aquifer, by State ......... 54
GEOHYDROLOGY OF THE HIGH PLAINS AQUIFER IN

PARTS OF COLORADO, KANSAS, NEBRASKA, NEW MEXICO,

OKLAHOMA, SOUTH DAKOTA, TEXAS, AND WYOMING

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

JOHN B. WEEKS

ABSTRACT

The High Plains aquifer, which underlies about 174,000 square 

miles in parts of eight States, is the principal source of water in 

one of the Nation's major agricultural areas. About 170,000 wells 

pump water from the aquifer to irrigate about 13 million acres in 

the High Plains. In 1978, the U.S. Geological Survey began a regional 

study of the High Plains aquifer to provide geohydrologic data and 

computer models of the aquifer needed to evaluate the effects of 

ground-water development. This report describes the geohydrology 

of the High Plains aquifer.

The High Plains aquifer consists mainly of hydraulically connected 

geologic units of late Tertiary or Quaternary age. The upper Tertiary 

rocks include part of the Brule Formation, Arikaree Group, and Ogallala Formation. The Quaternary deposits included in the aquifer consist of alluvial, dune-sand, and valley-fill deposits.

The Ogallala Formation, which underlies 134,000 square miles, is 

the principal geologic unit in the High Plains aquifer. The Ogallala 

consists of a heterogeneous sequence of clays, silts, sands, and 

gravels deposited by streams that flowed eastward from the mountains. Within the Ogallala, zones cemented with calcium carbonate 

are resistant to weathering and form escarpments that typically mark 

the boundary of the High Plains.

The High Plains aquifer is, regionally, a water-table aquifer consisting mostly of near-surface sand and gravel deposits. The 

maximum saturated thickness of the aquifer is about 1,000 feet and 

averages 200 feet. Hydraulic conductivity and specific yield of the 

aquifer depend on sediment types, which vary widely both horizontally and vertically. Consequently, hydraulic conductivity and specific 

yield also are highly variable. Hydraulic conductivity ranges from 

less than 25 to 300 feet per day and averages 60 feet per day. Specific 

yield ranges from less than 10 to 30 percent and averages about 15 

percent.

Ground-water flow generally is from west to east, at an average 

rate of about 1 foot per day, and discharges naturally to streams 

and springs, and directly to the atmosphere by evapotranspiration. 

Precipitation is the principal source of recharge to the High Plains 

aquifer. Estimated recharge rates range from 0.024 inch per year 

in part of Texas to 6 inches per year in south-central Kansas. Typically, recharge estimates are greatest for sandy soils.

The High Plains aquifer contains about 3.25 billion acre-feet of 

drainable water. About 66 percent of the water in storage is in Nebraska and about 12 percent is in Texas. New Mexico, the State with 

the smallest water resource in the High Plains, has only 1.5 percent 

of the volume of water in storage.

The quality of water in the High Plains aquifer generally is suitable 

for irrigation use but, in many places, the water does not meet U.S. 

Environmental Protection Agency drinking-water regulations. Excessive concentrations of dissolved solids, fluoride, chloride, and sulfate 

occur in parts of the aquifer in all States.

About 62 percent of the area of the High Plains aquifer contains 

water with 250 to 500 milligrams per liter dissolved solids; only 3 

percent of the area of the aquifer contains water exceeding 1,000 

milligrams per liter dissolved solids, most of which is in Texas. Generally, dissolved-solids concentrations are least in areas covered by 

sand because recharge is relatively large and the sand contains few 

readily soluble minerals. In most areas of the High Plains aquifer 

where the concentration of dissolved solids exceeds 1,000 milligrams 

per liter, the chemical composition of the water is affected by the 

underlying bedrock.

Sodium concentrations in ground water from the aquifer generally 

are less than 100 milligrams per liter. About 56 percent of the area 

of the aquifer contains water with less than 25 milligrams per liter 

sodium; only 3 percent of the area contains water exceeding 100 milligrams per liter sodium, most of which is in Texas. The concentration 

of sodium varies in response to the same factors that affect the concentration of dissolved solids. In parts of the southern High Plains 

of Texas, anomalously large concentrations of dissolved solids and 

sodium, caused by surface disposal of oilfield brines, have been reported.

About 95 percent of all water pumped from the High Plains aquifer 

is used for irrigation. In 1978, the reported number of acres irrigated 

in the High Plains was 13 million and about 170,000 wells pumped 

an estimated 23 million acre-feet of water for irrigation.

In parts of the High Plains, annual pumpage of 2 to 100 times 

greater than annual recharge has caused large water-level declines. 

Water levels have declined more than 100 feet from predevelopment 

to 1980 in parts of Kansas, New Mexico, Oklahoma, and Texas in 

areas totaling 2,500 square miles. Water levels have declined more 

than 50 feet in areas totaling 12,000 square miles and more than 

10 feet in areas totaling 50,000 square miles. Water-level declines 

increase pumping lift, decrease well yields, and limit development 

of the ground-water resource.

The volume of water in storage in the aquifer has decreased about 

166 million acre-feet since ground-water development began. Most 

of the depletion has occurred in Kansas and Texas: about 114 million 

acre-feet of depletion in Texas and 29 million acre-feet of depletion 

in Kansas.

The chemical quality of water in the aquifer may limit irrigation 

development in some areas. Areas of high salinity hazard occur in

1
HIGH PLAINS RASA PROJECT

Colorado, Kansas, Oklahoma, New Mexico, Texas, and Wyoming. In 

these areas, water from the High Plains aquifer may not be suitable 

for irrigation on soils that are not well drained.

The depth to water below land surface affects the cost of pumping 

water for irrigation. Declining water levels and increasing energy 

costs may seriously impact the economics of future irrigation development. The depth to water in the High Plains aquifer already is greater than 300 feet in parts of Kansas, New Mexico, and Texas.

Legal constraints also control development of ground water. The 

regulations controlling ground-water development vary widely between States and within some States. Future development of the 

High Plains aquifer will continue to be controlled by the laws of the 

individual States in the High Plains.

INTRODUCTION

The High Plains aquifer includes about 174,000 mi2 

(see Conversion Factors for definitions of abbreviated 

units) 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 as shown in figure 1. 

Ground water withdrawn from the aquifer is the principal water resource for most of the High Plains region, 

which is an important agricultural area. The High 

Plains aquifer is the shallowest and most abundant 

source of ground water in the region and the irrigated 

agricultural economy is dependent on the aquifer for 

continued growth and prosperity.

However, declining water levels and decreasing 

water supplies are causing serious concerns about the 

feasibility of continued crop production using ground 

water for irrigation. A comprehensive knowledge of the 

High Plains aquifer system is needed to provide a basis 

for predicting the effects of continued irrigation development.

PURPOSE AND SCOPE

National concern about the economic impact of declining water supplies in the High Plains resulted in the 

beginning of a regional study of the High Plains aquifer 

in 1978 as one of the first studies within the Regional 

Aquifer-System Analysis program of the U.S. Geological Survey. The purpose of this program is to provide 

hydrologic information and analytical capabilities 

needed for effective management of the Nation's 

ground-water resources.

The purpose of the High Plains study is to provide: 

(1) Hydrologic information needed to evaluate the effects of continued ground-water development; and (2) 

computer models to predict aquifer response to changes 

in ground-water development. This study is intended 

to provide managers with a coherent and comprehensive data set needed for ground-water resource management, and a tool (computer model) for evaluation 

of water-management alternatives. The computer 

model will be tested using historical data on irrigation 

demand and development. Selected ground-water management alternatives will be simulated to predict their 

effectiveness in prolonging the water supply.

A complete description of geology and hydrology of 

the High Plains aquifer is required for design and development of a computer model of the aquifer system. 

This report presents the geohydrologic framework on 

which the model will be based. The geologic and hydrologic characteristics of the aquifer are described; the 

relationships between the aquifer and bedrock units are 

discussed; the quantity and quality of ground water are 

presented; the effects of irrigation development on the 

aquifer are included.

PHYSICAL SETTING

The High Plains occupies the southern part of the 

Great Plains physiographic province which lies between 

the Rocky Mountains on the west and the Central Lowland on the east. The High Plains extends from southern South Dakota to northwestern Texas. The Platte, 

Arkansas, and Canadian Rivers are the only streams 

crossing the High Plains that originate in the Rocky 

Mountains. The area south of the Canadian River is 

commonly called the southern High Plains.

PHYSIOGRAPHY

The High Plains is characterized by flat to gently 

rolling terrain, which is a remnant of a vast plain 

formed by sediments that were deposited by streams 

flowing eastward from the Rocky Mountains. The ancestral plain extended from the mountains eastward 

beyond the Missouri River in some places (Trimble, 

1980b). Regional uplift forced streams to cut downward 

and erode the plain. Near the mountains, the plain was 

eroded by the Missouri, Platte, Arkansas, and Pecos 

Rivers, and the eastern border was eroded by many 

small streams. Erosion isolated the plains from the 

mountains and formed escarpments that typically mark 

the boundary of the High Plains. Only in southeastern 

Wyoming does the original plain still extend to the 

mountain front.

Wind-blown sand and silt, derived from the beds of 

rivers that eroded the plains, were deposited throughout large areas of the High Plains. The largest expanse 

of wind-blown sand deposits and dune topography in 

the Western Hemisphere (about 20,000 mi2) is in Nebraska (Madson, 1978) between the Platte and Niobrara 

Rivers. Within these sand hills, lakes and meadows 

occur between dunes where ground water is at or near 

land surface. Smaller areas of sand dunes occur in many 

other parts of the High Plains.
GEOHYDROLOGY OF THE HIGH PLAINS AQUIFER

Many lakes also occur on the High Plains outside of 

Nebraska. However, these lakes are shallow depressions or playas that collect and store water during 

periods of runoff; some of the deeper playas hold water 

throughout the year. Playas are most prevalent south 

of the Arkansas River. Because playas in the High 

Plains generally are above the regional water table, the 

water surfaces in the playas do not reflect the altitude 

of the water table in the underlying aquifer, as many 

of the lakes do in the sand hills of Nebraska.

CLIMATE

For the most part, the High Plains has a middle 

latitude dry continental climate. The climate is one of 

abundant sunshine, moderate precipitation (less than 20 

inches), frequent winds, low humidity, and a high rate 

of evaporation. Some areas of the High Plains in central 

Kansas and eastern Nebraska have a humid continental 

climate that has higher precipitation and humidity than 

the dry continental climate.

Mean annual precipitation increases eastward across 

the High Plains by about 1 inch every 25 miles from 

less than 16 inches to about 28 inches in eastern Nebraska and central Kansas as shown in figure 2. Typically, about 75 percent of the precipitation falls as rain 

during the growing season, April through September, 

a condition favorable to agriculture. However, much of 

the rain results from local thunderstorms, so large variations in rainfall can occur from place to place and year 

to year.

Both dry and humid continental climates have large 

daily and seasonal extremes of temperature. Daily temperatures may vary 15° to 30°C (Celsius). The seasonal 

extremes of temperature vary about 70°C between 

winter lows and summer highs. Wind direction and 

speed varies throughout the year, which is a consequence of cyclonic storms. Occasionally during the summer months, hot winds during extended dry periods 

cause crop damage and discomfort to animals and humans. Winter months generally are colder, dryer, and 

windier than the areas immediately east of the High 

Plains. Snowfall normally is light and often is accompanied by high winds with a resultant uneven distribution.

Persistent winds and high summer temperatures 

cause high rates of evaporation in the High Plains. 

Mean annual evaporation from Class A pans ranges 

from about 60 inches in northern Nebraska and southern South Dakota to about 105 inches in western Texas 

and southeastern New Mexico (fig. 2). Because of the 

large evaporative demand, little precipitation is available to recharge the ground-water system. Except in 

sand-dune areas where water can readily percolate 

down to the water table, most of the water that enters

the soil is returned to the atmosphere by evapotranspiration. Recharge to the ground-water system may be 

several inches per year in sand-dune areas; but, 

throughout the much larger part of the High Plains 

where soils can hold the water for subsequent evapotranspiration, recharge may average less than 0.5 inch 

per year.

Climate is the key factor in soil formation. Soils west 

of 97° W. longitude, which formed under short grass, 

are limy and those soils east of the 97° W. longitude, 

which formed under tall grass, are acid (White and 

Renner, 1957, p. 225). The limy soils are found in the 

dry continental climate where low precipitation and the 

absence of leaching account for the excellent fertility 

of the soil. Because evaporation greatly exceeds precipitation, there is an upward movement of nutrient 

minerals to the surface. The limy soils are extremely 

productive when water is available for vegetative 

growth.

CULTURAL SETTING

With few trees and little precipitation, the plains 

were known as the Great American Desert. Prior to 

the Civil War, the High Plains was home to few except 

the Plains Indians and North American bison upon 

which the Indians depended. The Indians dominated 

the plains until the late 1800's when the transcontinental railroad was constructed and the bison were virtually exterminated. The railroad opened the plains to 

range cattle. The grassy plains proved to be as favorable for cattle as they had been for bison and the Great 

American Desert became cattle country.

AGRICULTURAL DEVELOPMENT

Two pieces of legislation enacted during the Civil 

War greatly influenced the settling of the plains and 

the development of agriculture. The Homestead Act of 

1862 made the plains part of the public domain where 

land could be obtained for nominal fees. The Morrill 

Act of 1862 provided for the establishment of landgrant colleges. In 1863, Kansas State Agricultural College was established in Manhattan, Kansas, near the 

border of the High Plains.

During the late 1800's when the Plains Indians were 

no longer a threat, settlers and speculators began to 

surge onto the plains. Conflicts between farmers and 

ranchers resulted in range wars over fencing; but as 

the numbers of homesteaders grew, farmers were able 

to demand and defend their rights. During the severe 

winters of 1886-87, 50 to 60 percent of the range cattle 

starved (White and Renner, 1957, p. 229). The rangecattle industry never recovered and farming, supported 

by agricultural colleges, became the dominant industry.
HIGH PLAINS RASA PROJECT
O 

H 

O

SOfO O

sCO

> ,© c! > i^ M

250 KILUMETEKS

FIGURE 1. Location of High Plains aquifer.
HIGH PLAINS RASA PROJECT

101° 100° 99°

97° 96°

43°

42°

40°

390 I _ c§( COLORADO

AQUIFER 

BOUNDARYEXPLANATION

Line of equal normal 

annual precipitation 

Interval 4 inches

Line of equal normal 

annual pan evaporation 

Interval 5 inches

FIGURE 2. Normal annual precipitation and Class A pan evaporation in the High Plains (modified from U.S. Department of Commerce, 1977).
GEOHYDROLOGY OF THE HIGH PLAINS AQUIFER

From the turn of the century until World War I, 

agricultural development of the plains increased rapidly. During and after World War I, wheat became the 

dominant crop as a result of the war effort. The plains 

were planted to wheat year after year and by the time 

the drought of the 1930's occurred, continuous cropping 

had depleted the humus that bound the soil. The resulting poor crops were pastured to livestock and the 

ground became pulverized (White and Renner, 1957, 

p. 225). Wind erosion literally blew away the soil in 

gigantic dust clouds and the High Plains became known 

as the Dust Bowl. The drought of the 1930's spurred 

the development of irrigation farming on the High 

Plains and, during the next 2 decades, irrigation transformed the High Plains from Dust Bowl to Breadbasket one of the major farming areas in the United 

States.

AGRICULTURAL PRODUCTION

Of total United States crop production in 1977, the 

High Plains produced 16 percent of the wheat, 13 percent of the corn, 40 percent of the sorghum, and 25 

percent of the cotton. The total value of crops produced 

in the High Plains in 1977 was about $4.6 billion (High 

Plains Associates, 1982, p. 9 and 2-2). In addition, the 

High Plains produces about 40 percent of the feedlot 

beef raised in the United States. Grubb (1978) reported 

that, for the High Plains, total cash receipts for irrigated crops was more than $2 billion (nearly one-half 

of the High Plains total) and livestock production was 

valued at more than $10 billion.

During 1978, about 170,000 wells in the High Plains 

pumped about 23 million acre-ft of water to irrigate 

13 million acres. More than 20 percent of the irrigated 

land in the United States overlies the High Plains 

aquifer and about 30 percent of the ground water used 

for irrigation in the United States was pumped from 

the High Plains aquifer. Irrigation pumpage has caused 

areally extensive water-level declines in the aquifer. 

Consequently, many irrigators have experienced increased pumping costs, decreased well yields, and concern about the future of irrigation farming on the High 

Plains.

PREVIOUS HYDROLOGIC STUDIES

The first regional study of the High Plains was conducted by the U.S. Geological Survey at the beginning 

of this century (Johnson, 1901). The study provided a 

reconnaissance of the geographic, physiographic, and 

hydrologic features of the area and reported on the region within the framework of the then current technology. The conclusions of the study pointed to the vast 

ground-water resources of the area but held little promise for agricultural development of the region because 

of limited rainfall, high evaporation, and few surface 

streams.

Since that time, technological advances have provided the means to recover the ground-water resource 

identified by Johnson (1901). However, hydrologic 

studies of the region have not kept pace with groundwater development. Many water-resource studies of 

small areas such as counties or groups of counties have 

been made, but few studies of larger areas within the 

High Plains have been made. In fact, only one other 

region-wide hydrologic study has been made since 1901 

and that was reported on by Lohman (1953). The results of previous investigations provide a wealth of information subdivided by political boundaries but without continuity across those boundaries.

The results of previous studies provided the foundation for the Regional Aquifer-System Analysis of the 

High Plains aquifer. In developing the geohydrologic 

framework of the High Plains aquifer, this investigation 

assembled, organized, and assimilated the geohydrologic data available from many previous studies. The 

principal references (about 180) are listed in the 

Selected References section of this report.

GEOLOGY

The geologic history of the High Plains began more 

than 500 million years ago. During most of Cambrian 

to Tertiary time (570 to 63 million years ago), shallow 

seas covered the interior of North America. A thick 

sequence of sediments, in some places more than 10,000 

feet thick, was deposited on the subsiding seafloor.

The sea covered the High Plains almost entirely during the Permian Period (290 to 240 million years ago); 

but it receded during the Triassic Period (240 to 205 

million years ago). During Early and Middle Triassic 

time, the High Plains was subjected to erosion and no 

depositional record is found between the marine Permian rocks and the continental Upper Triassic rocks. During the Jurassic Period (205 to 138 million years ago), 

erosion predominated during Early Jurassic time prior 

to deposition of Middle and Upper Jurassic rocks. Jurassic rocks are of continental origin and represent deposition from intermittent streams during a dry climate. 

An abundance of fossil remains of dinosaurs and other 

land animals is characteristic of Jurassic deposits.

Shallow seas covered the area intermittently during 

Early Cretaceous time (138 to 96 million years ago). 

In the southern High Plains of Texas, marine shales 

and sands were deposited in response to changes in sea 

level. In the northern High Plains, most of the Early 

Cretaceous rocks were deposited near beaches or in adjoining wet lands, river estuaries, and river valleys.
8 HIGH PLAINS RASA PROJECT

During Late Cretaceous time (96 to 63 million years 

ago), the Rocky Mountain trough formed a vast seaway 

nearly 1,000 miles wide and 3,000 miles long. As much 

as 50 percent of present North America was covered 

by interior seas. The interior seas retreated southward 

and there was a rapid filling of the basin with sediments from the raising highlands to the west. The final 

retreat of the sea transformed its old floor into a vast 

swampy lowland. Eastward-flowing streams deposited 

thick sediments in this lowland during the closing 

stages of Cretaceous time. The vegetation that accumulated in the swamps of this lowland formed the vast 

coal beds of Late Cretaceous age in the Rocky Mountain region from Canada to Mexico.

The Laramide revolution or period of mountain building began about 70 million years ago at about the same 

time as the great interior sea retreated. The mountains 

produced by the Laramide revolution rose about onethird as high above sea level as the present-day Rocky 

Mountains (King, 1959, p. 126). These ancestral Rockies were eroded about as rapidly as they were uplifted. Regional altitudes remained low and the climate 

was uniformly moist and semitropical. As a result of 

the Laramide revolution, there was increased availability of water to streams and much rock material was 

available for stream transport. Mountain building continued into Tertiary time.

The Tertiary Period (63 to 2 million years ago) began 

with a long period of no deposition in most of the High 

Plains. The oldest Tertiary rocks found on the High 

Plains are of Oligocene age (38 to 24 million years ago). 

By the middle of the Oligocene, the Rocky Mountains 

virtually were peneplained, but slight differential uplift 

that included eastward tilting of the High Plains was 

occurring locally. During the Oligocene, volcanism was 

widespread in the mountains (Robinson, 1972) and 

enormous quantities of volcanic debris and sediment 

eroded from the mountain blocks were deposited on the 

plains.

During Miocene time (24 to 5 million years ago), 

sedimentation on the plains continued with some volcanic material deposited as well as weathered debris 

from the mountains. Most of the sediments comprising 

the High Plains aquifer were deposited during this 

time. Regional uplift was renewed near the end of Miocene time. The Rocky Mountains and the High Plains 

were raised differentially during this epoch, and uplift 

of the mountains is still continuing (Izett, 1975). Thus, 

the erosional cycle that started near the end of Miocene 

time is the present erosional cycle that has continued 

to shape the High Plains. By the close of the Miocene, 

the major physiographic features of the area occupied 

by the North American grasslands were established 

(Dix, 1964). The fossil plants and animals contained in

the middle and upper Tertiary deposits record increasing regional altitudes and aridity. The transition to 

more arid conditions resulted partly from world-wide 

cooling, and partly from the additional uplift of the 

Rocky Mountains, which produced a rain shadow over 

the High Plains.

Pliocene time (5 to 2 million years ago) was a period 

of continued uplift and erosion without much deposition. Regional uplift caused streams to cut downward; 

near the mountain front, the plains were eroded by the 

Missouri, Platte, Arkansas, and Pecos Rivers. The 

High Plains became a remnant of the much larger Miocene plain. Today, the High Plains extends to the 

mountain front in Wyoming only.

The sculpturing of the High Plains continued through 

the Quaternary Period (2 million years ago to present). 

Although the High Plains was not eroded by glaciers, 

stream erosion continued to shape the region. Large 

quantities of sediment were eroded from the mountains 

and the plains. Giant braided streams transported large 

quantities of silt, sand, and gravel and deposited these 

sediments in stream valleys and terraces. Winds winnowed sand and silt from the stream valleys and redeposited it as dune sand and loess over large parts of 

the High Plains.

HIGH PLAINS AQUIFER

The High Plains aquifer consists mainly of one or 

more hydraulically connected geologic units of late Tertiary or Quaternary age. The principal geologic units 

in the High Plains aquifer are shown in figure 3 and 

summarized in the generalized geologic section presented in table 1. The upper Tertiary rocks consist of 

the Brule Formation (of the White River Group), 

Arikaree Group, and Ogallala Formation. The Quaternary deposits consist of alluvial, dune-sand, and valleyfill deposits. Except for dune sand in figure 3, the 

Quaternary deposits are lumped and are shown only 

in areas where they do not overlie Tertiary aquifer 

units. In Texas, some collapse structures, filled with 

Triassic, Jurassic, and Lower Cretaceous rocks that 

have secondary permeability, are considered part of the 

High Plains aquifer, however, they are minor and are 

not shown in figure 3.

TERTIARY UNITS

The Brule Formation crops out in or underlies much 

of western Nebraska, northeastern Colorado, southwestern South Dakota, and southeastern Wyoming. 

The Brule is mainly a massive siltstone containing beds 

of sandstone and channel deposits of sand. Lenticular 

beds of volcanic ash, claystone, and fine sand are pres-
GEOHYDROLOGY OF THE HIGH PLAINS AQUIFER

TABLE 1. Generalized section of geologic units in the High Plains

[From Weeks and Gutentag, 1981]

System

QUATERNARY

TERTIARY

CRETACEOUS

O

U) 

CO

cr

TRIASSIC

 z. 

cr

LU 

Q.

Series

Pleistocene Holocene and 

Pleistocene

Miocene

Oligocene

Upper Cretaceous

Lower Cretaceous

Middle and Upper Jurassic

Upper Triassic

5 r6 S.I 

§ r) E

CD

Geologic unit

Valley-fill 

deposits

Dune sand

Loess

Unconsolidated 

alluvial deposits

Ogallala 

Formation

Arikaree Group

White River 

Group

Undifferentiated 

rocks

Undttferentiated 

rocks

Undifferentiated 

rocks

Dockum ! 

GrOTjp

Undifferentiated 

rocks

Thickness, 

in feet

0 to 60

0 to 300

0 to 250

0 to 550

0 to 700

0 to 1000

0 to 700

0 to 8000

0 to 700

0 to 600

0 to 2000

300 to 3000

Physical character

Stream-laid deposits of gravel, sand, silt, and clay associated with the most recent cycle 

of erosion and deposition along present streams. Forms part o* High Plains aquifer where 

hydraulically connected to underlying Quaternary and Tertiary deposits.

Fine to medium sand with small amounts of clay, silt, and coarse sand formed into hills 

and ridges by the wind. Forms part of High Plains aquifer where saturated.

Silt with lesser amounts of very fine sand and clay deposited as windblown dust.

Stream-laid deposits of gravel, sand, silt, and clay locally cemented by calcium carbonate 

into caliche or mortar beds. Forms part of High Plains aquifer where hydraulically connected 

laterally or vertically to Tertiary deposits.

Poorly sorted clay, silt, sand, and gravel generally unconsolidated; forms caliche layers or 

mortar beds when cemented by calcium carbonate. Includes units equivalent to the locally 

used terms "Ash Hollow," "Kimball," "Sidney Gravel," and "Valentine" Members or 

Formations assigned to the Ogallala Formation or "Group," and Delmore and Laverne 

Formations. Ogallala comprises large part of High Plains aquifer where saturated.

Predominantly massive very fine to fine-grained sandstone with localized beds of volcanic 

ash, silty sand, siltstone, claystone, sandy clay, limestone, marl, and mortar beds. Includes 

units assigned to the Hemingford Group of Lugn (1938), Marsland Formation, Rosebud 

Formation used in South Dakota by Harksen and Macdonald (1969), and Sheep Creek 

Formation. Also includes units equivalent to Gering Formation, Harrison Sandstone, and 

Monroe Creek Sandstone. Forms part of the High Plains aquifer.

Upper unit, Brule Formation, predominantly massive siltstone containing sarrastone beds 

and channel deposits of sandstone with localized lenticular beds of volcanic ash, claystone, 

and fine sand. The Brule Formation is considered part of the High Plains aquifer only where 

it contains saturated sandstones or interconnected fractures. Lower unit, Chadron 

Formation, mainly consists of varicolored, bentonitic, loosely to moderately cemented clay 

and silt that contains channel deposits of sandstone and conglomerate.

Shales, chalks, limestones, and sandstones. Upper part may contain lignite and coal beds. 

Unit includes Belle Fourche and Carlile Shales, Codell and Fox Hills Sandstones, Frontier 

Formation, Graneros Shale, Greenhorn Limestone, Lance Formation, Niobrara Chalk or 

Formation, and Pierre Shale.

Fine- to medium-grained, thin-bedded to massive cliff-forming sandstone interbedded with 

shale. Black and varicolored shale and thin- to thick-bedded limestone. Includes units 

equivalent to Fredericksburg and Washita Groups; Dakota and Purgatoire Formations; Antlers 

Sand of Hill (1894), Cheyenne, Fall River, Lakota, Mesa Rica, and Newcastle Sandstones; 

and Fuson, Kiowa, Mowry, Skull Creek, and Tucumcari Shales.

Varicolored shale, fine- to very coarse grained sandstone, limestone, dolomite, and 

conglomerate. Includes units equivalent to Entrada and Exeter Sandstones, and Morrison 

and Sundance Formations.

Upper unit, Trujillo Formation, varicolored siltstone, claystone, conglomerate, fine-grained 

sandstone, and limestone. Lower unit, Tecovas Formation, varicolored fine- to mediumgrained sandstone with some claystone and interbedded shale. Include units equivalent to 

Chinle and Redondo Formations, and Santa Rosa Sandstone.

Interbedded predominantly red-shale, siltstone, sandstone, gypsum, anhydrite, dolomite, 

bedded salt, and local limestone beds. Includes Artesia, Council Grove, Nippewalla Groups; 

Quartermaster Formation, Sumner and Whitehorse Groups.

ent, locally. Maximum thickness of the Brule is about 

600 feet.

The Brule Formation generally has little permeability. However, in some places, permeability of the formation has been increased by secondary porosity 

joints, fractures, and solution openings. The Brule Formation is considered part of the aquifer only in areas 

where it contains saturated zones resulting from interconnected secondary porosity (fig. 3). Where secondary 

porosity has not been developed, the top of the Brule
10 HIGH PLAINS RASA PROJECT

43°

42°

40°

39°

CANADIAN 

NEW MEXICO '

EXPLANATION

QUATERNARY UNITS 

Undivided

Dune sand

TERTIARY UNITS 

Ogallala Formation

Arikaree Group 

Brule Formation

AQUIFER 

BOUNDARY

FIGURE 3. Principal geologic units in the High Plains aquifer.
GEOHYDROLOGY OF THE HIGH PLAINS AQUIFER 11

Formation is considered the base of the High Plains 

aquifer. Well yields from the Brule Formation are 

highly variable because the yield depends on the degree 

to which secondary porosity has been developed. Wells 

yielding as much as 1,500 gal/min from fractured Brule 

have been reported along Lodgepole Creek in Nebraska 

and Wyoming and in the vicinity of Julesberg in northeastern Colorado (fig. 1). However, well yields from 

the Brule Formation typically are less than 300 gal/min. 

The Arikaree Group (or Formation) includes all late 

Tertiary deposits between the underlying Brule Formation and overlying Ogallala Formation. The Arikaree 

crops out in or underlies large areas in western Nebraska, southwestern South Dakota, and southeastern 

Wyoming (fig. 3). The Arikaree is mainly a massive, 

very fine- to fine-grained sandstone, but contains 

localized beds of volcanic ash, silty sand, and sandy 

clay. Maximum thickness of the Arikaree is about 1,000 

feet in western Nebraska and in Platte County, Wyoming.

Wells completed in the Arikaree Group generally do 

not yield large quantities of water. In Wyoming and 

probably western Nebraska, well yields of about 350 

gal/min can be expected from about 200 feet of saturated thickness. In Niobrara County, Wyoming, yields 

of 600 gal/min have been reported from 700 feet of saturated thickness. Secondary porosity, similar to that in 

the Brule, also occurs in the Arikaree Group.

The term Ogallala Formation, as used in this report, 

refers to all late Tertiary rocks in the study area that 

are younger than the Arikaree Group. The Ogallala 

Formation is the principal geologic unit in the High 

Plains aquifer and underlies about 134,000 mi2 of the 

study area (fig. 3). Maximum thickness of the Ogallala 

is about 700 feet. When the Ogallala was deposited, 

aggrading streams filled and buried valleys eroded into 

pre-Ogallala rocks. Braided streams flowed eastward 

from the mountains transporting rock debris, which 

was deposited as a heterogeneous sequence of clays, 

silts, sands, and gravels (Fenneman, 1931).

Within the Ogallala, zones cemented with calcium 

carbonate are resistant to weathering and form ledges 

in outcrops. The most distinctive of these layers, the 

Ogallala cap rock (commonly called caliche or mortar 

bed), is near the top of the Ogallala Formation. The 

cap rock underlies large areas in Texas and New 

Mexico, and may be as thick as 60 feet.

Saturated sediments in the Ogallala are not distributed evenly throughout the area. Irrigation wells with 

yields of about 1,000 gal/min can be developed from 

about 100 feet of saturated sand and gravel. In the 

southern High Plains and in parts of western Kansas, 

wells pumping 100 gal/min are developed in areas with 

as little as 20 feet of saturated sand and gravel.

QUATERNARY UNITS

Unconsolidated alluvial deposits of Quaternary age 

that are in hydraulic connection with Tertiary deposits 

are considered to be part of the High Plains aquifer. 

Much of the gravel, sand, silt, and clay in the alluvial 

deposits are reworked from the Ogallala Formation 

(Gutentag, 1963). These Quaternary alluvial deposits 

have a maximum thickness of about 300 feet. Alluvial 

deposits comprise the High Plains aquifer in eastern 

Nebraska and central Kansas (fig. 3). In many areas 

of the High Plains, Quaternary alluvial deposits directly 

overlie the Ogallala Formation to form one aquifer.

Dune-sand deposits of Quaternary age, consisting 

predominantly of very fine to medium wind-blown sand, 

are part of the High Plains aquifer. Areas covered by 

dune sand are shown in figure 3 which was modified 

from Thorp and others (1952). Of the 174,000 mi2 underlain by the High Plains aquifer, about 19 percent 

is covered by dune sand. The most extensive area of 

dune sand is in west-central Nebraska where the deposits cover an area of 20,000 mi2 with a maximum 

thickness of about 300 feet. Large areas also are covered by dune-sand deposits south of the Arkansas 

River in Kansas. In south-central Kansas, dune sand 

is saturated in many places and forms part of the 

aquifer system. In southwestern Kansas, the water 

table generally is below the dune-sand deposits. 

Throughout the High Plains, dune sands are important 

recharge areas for the aquifer.

Valley-fill deposits consist of unconsolidated gravel, 

sand, silt, and clay associated with the most recent 

cycle of erosion and deposition along present streams. 

These deposits are as much as 60 feet thick. Valley-fill 

deposits that are connected hydraulically to underlying 

Tertiary or Quaternary deposits are considered part of 

the High Plains aquifer. The valley-fill deposits and associated streams form stream-aquifer systems that link 

the High Plains aquifer to surface streams, particularly 

along the Platte, Republican, and Arkansas Rivers.

DEPOSITIONAL HISTORY

The depositional history of the geologic units that 

comprise the High Plains aquifer is complex. Both fluvial (stream-deposited) and eolian (wind-blown) sediments form the High Plains aquifer. Most studies of 

the depositional history of the High Plains aquifer are 

concerned with the Ogallala Formation. Consequently, 

the following discussion emphasizes the Ogallala, which 

is the principal geologic unit in the aquifer (fig 3).

The earliest hypothesis by the U.S. Geological Survey on the mode of deposition of the Ogallala was made 

by King (1878) who proposed that the Ogallala was deposited in a lake environment. Gilbert (1896) developed
12 HIGH PLAINS RASA PROJECT

the theory of stream deposition for the Ogallala and 

Johnson (1901), in the first regional study of the High 

Plains, described the Ogallala as a debris apron formed 

by coalescence of alluvial fans in series along the mountain front. Frye (1970) considered the Ogallala to be 

deposited by streams with local eolian deposition. Frye 

also considered the basal part of the formation to be 

deposited in east-west trending valleys, each containing 

its own alluvial fill. Coalescence of the alluvial fills from 

one valley to another took place as the individual divides were buried as the Ogallala deposits thickened. 

The Ogallala was succinctly described by Schultz (1977, 

p. 12) as " *** characterized to a great extent by a 

monotonous lithology representing a random intermixture of channel and flood-plain environments of deposition."

All theories since Gilbert (1896) on deposition of the 

Ogallala involve transport to the plains of debris eroded 

from the mountains by streams. Ore (1963, p. 153) 

studied the Ogallala in Wyoming and found it to be 

deposited by a rapid aggradational stream where no 

evidence of a major channel system was noted. He considered the Ogallala to be a sheet deposit laid down 

by braided streams along a rapidly rising mountain 

front. Streams that flow away from the mountain front 

with high discharges will develop braiding when the 

gradient decreases and deposition takes place.

An important study concerning the vertical and horizontal dimensions of stream deposits that formed the 

Ogallala was made by Breyer (1975). Breyer applied 

a statistical approach using Markov chain analysis to 

detect repetitive lithologic sequences in the Ogallala in 

Nebraska. The analytical method was to classify the 

lithology in a vertical sequence into eight facies and 

tabulate the number of vertical transitions between 

each of the facies. The eight facies were limestone, 

marl, clay, silt, sandy silt, sand, gravelly sand, and 

gravel. The probability of occurrence of each transition 

was calculated and statistically tested to determine 

which transitions occurred with greater than random 

frequency. Breyer found only 4 of the possible 56 facies 

transitions occurred with greater than random frequencies; these were limestone to sand, clay to sand, 

gravelly sand to gravel, and gravel to gravelly sand. 

Breyer (1975, p. 4) concluded that the distribution of 

sediment types (facies) in a vertical section is largely 

random and representative of deposition by braided 

streams. Braided stream deposits show coarsening-upward transitions as well as fining-upward transitions.

The Oligocene fluvial deposits of the White River 

Group were compared by Blodgett (1974) to the modern 

Platte River system in Nebraska. Blodgett viewed 31 

sites in Wyoming and 15 sites in Nebraska where the 

fluvial White River deposits were exposed. He concluded that fining-upward sequences were present with 

coarsening-upward sequences. His conclusion was that, 

in the White River Group, fluvial facies were deposited 

by aggradational Platte-type braided streams.

Numerous studies of modern braided streams have 

been made. Kessler (1971) studied braided streams 

with examples from the South Canadian River, Texas. 

Waechter (1972) studied the Prairie Dog Town Fork 

of the Red River in Texas. The Platte River has been 

studied intensely by Smith (1970), Williams (1978), 

Blodgett and Stanley (1980), and Crowley (1981). Miall 

(1977) reviewed the environments of braided streams 

and showed that vertical sequences recorded in modern 

and ancient deposits are of several types: channel-fill 

deposits, valley-fill deposits, channel reoccupation deposits, and point-bar deposits. The identifying feature 

of braided stream deposits is the occurrence of coarsening-upward as well as fining-upward sediments. There 

is sufficient evidence from modern streams and ancient 

stream deposits to indicate that braiding was an important factor in deposition of the High Plains aquifer.

In western Texas and eastern New Mexico, Seni 

(1980) considered the three-dimensional patterns of 

Ogallala thickness, sand-body geometry, and formational texture to be consistent with a wet alluvial-fan 

depositional model. Wet or humid alluvial fans may be 

regarded as deposits of braided streams that develop 

without lateral confinement (Reineck and Singh, 1980). 

The fan facies recognized are the medial and distal 

facies of alluvial fans. Medial-fan facies are characterized as a broad sand and gravel sheet deposited by 

braided streams. Medial-fan facies grade downdip into 

distal-fan facies. Distal-fan facies are characterized by 

digitate bifurcating sand and gravel bands. Seni (1980) 

indicated that distal-fan facies are separated by thinner 

sand and gravel deposits as well as fine-grained material similar to interchannel deposits found on flood 

plains of meandering streams.

The mode of fluvial deposition depends on the climate 

at the time the sediments were deposited. Climate can 

be inferred by determining the ecological factors controlling the flora and fauna that existed during deposition. The climate of the area during late Tertiary time 

was not the same as the modern climate. The climate 

at the time the Ogallala was deposited was described 

by Hibbard (1960) after considering all available fossil 

faunas and floras as " *** the majority of the area from 

South Dakota to Texas was a moist, subhumid, subtropical savanna with forests and tall grasses along the 

river valleys, with chiefly shrubs and tall grasses on 

the valley walls and on the low divides. Some short 

grasses may have occurred on the higher and welldrained divides."

The Kilgore flora found in the lower part of the Ogal-
GEOHYDROLOGY OF THE HIGH PLAINS AQUIFER 13

lala in western Nebraska was compared by MacGmitie 

(1962) to modern areas where similar flora flourish. The 

present areas with flora comparable to the ancient 

Ogallala Kilgore flora are the Kerrville-San Antonio 

area in south-central Texas and the hills near Monterrey, Mexico. The present climate at San Antonio is considerably wetter and warmer than western Nebraska. 

Average annual precipitation is about 6 inches greater, 

average January temperature is about 17°C warmer, 

the average July temperature is about 6°C warmer, and 

the average annual temperature is 11°C warmer in San 

Antonio than in western Nebraska. Thus, the climate 

of the High Plains during late Tertiary time was wetter 

and warmer than the present climate, which is consistant with the formation of humid alluvial fans deposited 

by braided streams.

There is agreement by various investigators that the 

Ogallala Formation and other geologic components of 

the High Plains aquifer were deposited by fluvial action. The concept of a humid alluvial-fan model (Seni, 

1980) with deposition of the fan material by braided 

streams is not appreciably different from that of Breyer 

(1975) who postulated deposition by braided streams. 

The concept of stream alluviation without fan development and local eolian deposition proposed by Frye 

(1970) is not contradictory to humid-fan development 

because in some areas fan development may not have 

been as active and stream alluviation could have occurred downstream from distal-fan development. Undoubtedly, more than one mode of stream deposition 

occurred in the vast area of the High Plains.

During Tertiary time, the major mode of deposition 

was fluvial with minor periods of local eolian deposition. 

However, during Quaternary time, as the climate of 

the area became dryer and colder due to mountain uplift, the major mode of deposition in the High Plains 

changed to eolian.

All areas of the High Plains surface were modified 

by either erosional or depositional wind action during 

the Quaternary. The source areas for the eolian deposits were the Tertiary outcrops and the flood-plain 

deposits of the major rivers. Winds transported fine 

material eroded from the source areas many hundreds 

of miles before it was deposited. Different size materials in eolian deposits are separated from each other 

in the direction of wind movement. Sand will not be 

carried into the main region of dust deposition. There 

are transition zones where loess and sand interface with 

one another. Loess is the dust deposited by ancient 

dust storms.

Recent dust storms resulted from abnormally low 

precipitation for prolonged periods. Droughts were 

common in the middle 1930's, 1950's and in the 1970's. 

Lugn (1962) reported that the March 20th, 1935, dust

storm deposited 5 grams of dust per square foot at Lincoln, Nebraska. Dust storms were so severe during the 

1930's that many domestic animals died by suffocation 

and both man and beast severely suffered from respiratory ailments. Fossil evidence indicates that during 

late Pleistocene time (30,000 to 10,000 years ago) there 

were many periods when blowing dust adversely affected the mammal population (Schultz, 1968). Some 

mammals, such as the great mammoths, died from lack 

of food and water, and their bones were buried by the 

dust. Later mammal generations returned to repopulate the loess areas when climatic conditions again became favorable and there was available water and forage.

The winds that winnowed dust-sized particles also 

moved sand-sized material from the source areas to 

form dune deposits. Dune-sand deposits of Quaternary 

age consist predominantly of very fine to medium windblown sand. In Nebraska, the largest and most prominant dunes were formed during a time of strong, persistent, and widespread wind action under desert conditions when vegetation was almost absent. At the time 

the dunes were forming, the landscape was probably 

similar to that of modern deserts in Africa and Asia 

(Smith, 1965). At any given place, dune-building winds 

may be assumed to be at right angles to the average 

trend of the dune ridges. In Nebraska, the principal 

wind direction was from the north and northwest based 

on dune orientation (Ahlbrandt and Fryberger, 1980). 

Dune development was terminated by climatic change 

that allowed vegetation to stabilize the dune surface. 

Many cycles of dune development and stabilization, 

which resulted from climatic changes during glacial and 

interglacial periods, are found in the dune sand.

BEDROCK

Bedrock units in contact with the High Plains aquifer 

range in age from Permian to Tertiary. The location 

of the bedrock is shown in figure 4, which is reproduced 

here from a larger map presented by Weeks and Gutentag (1981). The geology of the bedrock units is summarized in table 1. The area of the High Plains aquifer 

in contact with each bedrock unit is summarized in figure 5.

PERMIAN UNITS

The oldest rocks in contact with the High Plains 

aquifer are of Permian age (290 to 240 million years 

ago). Permian rocks directly underlie 12 percent of the 

High Plains aquifer in Kansas, Oklahoma, and Texas 

(figs. 4 and 5). Permian red beds and evaporites were 

deposited in extensive, shallow, brackish to saline seas 

subject to periodic influxes of marine water. Dissolution
14 HIGH PLAINS RASA PROJECT

106°

43°

WHITE CLAY 

FAULT

BEAR CREEK 

FAULT

CROOKED CREEK 

FAULT

EXPLANATION

GEOLOGIC UNITS UNDERLYING

HIGH PLAINS AQUIFER 

Tertiary rocks

Upper Cretaceous rocks 

Lower Cretaceous rocks 

Jurassic and Triassic rocks 

Permian rocks

AQUIFER h/ 

BOUNDARY-4

FAULT-Bar and ball on 

downthrown side

FIGURE 4. Geology of bedrock units underlying the High Plains aquifer (from Weeks and Gutentag, 1981).
GEOHYDROLOGY OF THE HIGH PLAINS AQUIFER 15

and removal of some of these evaporites by ground 

water within the Permian rocks has resulted in faulting 

of the overlying deposits (Gutentag, Lobmeyer, and 

Slagle, 1981). Bear Creek fault (fig. 4) in southwestern 

Kansas and southeastern Colorado, and Crooked Creek 

fault (fig. 4) in southwestern Kansas and northwestern 

Oklahoma, are the result of salt dissolution. Salt collapse basins and a broad zone of salt dissolution in 

northwestern Texas have been mapped by Seni (1980). 

Sink holes developed by salt solution subsequently 

were filled by younger materials that are part of the 

High Plains aquifer.

Permian rocks in contact with the High Plains aquifer 

contain water that is not suitable for irrigation use because of large concentrations of dissolved solids. Gutentag, Lobmeyer, and Slagle (1981, p. 39) reported 33,800 

mg/L (milligrams per liter) dissolved solids in water 

from a well completed in Permian rocks in Seward 

County, Kansas. Mineralized water from Permian rock 

moves naturally through the High Plains aquifer to discharge along the Beaver, Cimarron, and Arkansas Rivers in Kansas and Oklahoma. Generally, Permian rocks 

have low permeability relative to the overlying High 

Plains aquifer. Where the High Plains aquifer is in hydraulic connection with Permian beds, water-level declines in the High Plains aquifer can cause or enhance 

movement of mineralized water from Permian beds into 

the aquifer.

TRIASSIC AND JURASSIC UNITS

Rocks of Triassic and Jurassic age (240 to 138 million 

years ago) directly underlie 16 percent of the High 

Plains aquifer in Colorado, Kansas, New Mexico, Oklahoma, and Texas (figs. 4 and 5). Although the Triassic 

and Jurassic are separate systems in table 1 showing 

the geologic section, they are combined on the geologic 

map (fig. 4) because the rocks of both systems are predominantly sandstones and shales and have similar hydrologic characteristics.

Lower and Middle Triassic and Lower Jurassic rocks 

are not present in the High Plains. The missing rocks 

indicate that continental erosion prevailed through 

Early and Middle Triassic time prior to deposition of 

the continental Upper Triassic rocks. Continental erosion again prevailed during Early Jurassic time prior 

to deposition of Middle and Upper Jurassic rocks.

Some sandstones of Triassic and Jurassic age have 

adequate permeability to yield large enough quantities 

of water for irrigation. Between the Arkansas and 

Canadian Rivers in parts of Colorado, Kansas, Oklahoma, New Mexico, and Texas, many irrigation wells 

withdraw water from both the High Plains aquifer and 

Triassic and Jurassic sandstones. In parts of Texas,

north of the Canadian River, Triassic and Jurassic 

sandstones are in direct contact with overlying 

semiconsolidated sediments of Tertiary age. Locally, 

where the rocks of both systems are hydraulically connected and are hydrologically similar, the High Plains 

aquifer includes Triassic and Jurassic sandstones in 

parts of Dallam, Hartley, Moore, and Sherman Counties, Texas.

CRETACEOUS UNITS

Lower Cretaceous rocks directly underlie 12 percent 

of the High Plains aquifer in parts of Colorado, Kansas, 

Nebraska, New Mexico, Oklahoma, and Texas (figs. 4 

and 5). Shallow seas covered the area intermittently 

throughout Early Cretaceous time (138 to 96 million 

years ago) when the Lower Cretaceous rocks were deposited. North of the Canadian River, Lower Cretaceous rocks were deposited near sea level or in adjoining lowlands and consist mostly of sandstones and 

shales. South of the Canadian River, Lower Cretaceous 

rocks were deposited in deeper water and consist 

mainly of shales that grade into limestones.

The sandstone beds within the Lower Cretaceous deposits are discontinuous and differ greatly in permeabil40

0 30

I LLJ

H O

8< 20

0?

u. O 

O

10

FIGURE 5. Area of High Plains aquifer in contact with 

bedrock units
16 HIGH PLAINS RASA PROJECT

ity both horizontally and vertically from one area to 

another. Where Lower Cretaceous sandstone beds are 

in contact with the overlying younger deposits in the 

High Plains aquifer, there is hydraulic connection between the two units. Except in the southern High 

Plains, Lower Cretaceous sandstones and shales generally contain water of suitable quality for irrigation use. 

However, these sandstones and shales typically have 

low permeability and storage relative to the High 

Plains aquifer and wells completed in Lower Cretaceous rocks experience large drawdowns and well interference throughout large areas.

Upper Cretaceous rocks directly underlie 32 percent 

of the High Plains aquifer in large areas in Colorado, 

Kansas, and Nebraska and small areas in New Mexico, 

South Dakota, and Wyoming (figs. 4 and 5). During 

Late Cretaceous time (96 to 63 million years ago), 

Upper Cretaceous shales, chalks, limestones, and sandstones were deposited in the broad Rocky Mountain 

trough that formed a vast seaway nearly 1,000 miles 

wide and about 3,000 miles long.

Within the Upper Cretaceous rocks, only the Niobrara Chalk or Formation (table 1) is known to yield 

water to wells in quantities large enough for irrigation. 

The Niobrara Chalk underlies the High Plains in Colorado, Kansas, Nebraska, South Dakota, and Wyoming. Where fractures and solution openings have developed, large quantities of water of suitable quality 

for irrigation have been developed in Finney and Scott 

Counties, Kansas (Gutentag and Stullken, 1976, p. 11). 

The water in the Niobrara Chalk in Kansas is derived 

from the overlying High Plains aquifer. In Madison and 

Pierce Counties, Nebraska, the Niobrara Chalk yields 

water to domestic, stock, and municipal wells.

TERTIARY UNITS

Oligocene rocks directly underlie 28 percent of the 

High Plains aquifer in Colorado, Nebraska, South 

Dakota, and Wyoming (figs. 4 and 5). Rocks in the 

White River Group (38 to 24 million years ago) are the 

oldest Tertiary deposits present under the High Plains 

(table 1). Older Tertiary deposits, although present 

further west, do not underlie the High Plains.

The Chadron and Bmle Formations comprise the 

White River Group. The Chadron Formation is the 

lower unit and consists of consolidated beds of clay and 

silt deposited on ancient flood plains and stream channel fill deposits of sandstone and conglomerate. The 

Chadron is overlain by the Brule Formation, which is 

predominately a massive siltstone containing consolidated beds of volcanic ash, clay, and fine sand.

The sediments comprising the Brule Formation were 

deposited in a large basin that contained freshwater

lakes, mud flats, and braided streams. The Brule Formation is considered part of the aquifer only in areas 

where it contains secondary permeability resulting 

from interconnected fractures (fig. 3). Generally, the 

top of the Brule Formation is considered the base of 

the High Plains aquifer.

RELATIONSHIP BETWEEN BEDROCK 

AND AQUIFER

Faulting and salt dissolution in the bedrock units affect the base of the High Plains aquifer. The altitude 

of the base of the High Plains aquifer is shown in figure 

6. In this report, National Geodetic Vertical Datum of 

1929 is called sea level. Thus, figure 6 shows altitudes 

relative to modern sea level. The base of the aquifer 

is primarily an erosional surface cut into Permian, Triassic, Jurassic, Cretaceous, and Tertiary rocks. A 

larger scale map of the altitude of aquifer base was 

published by Weeks and Gutentag (1981).

Sandstone beds in Triassic, Jurassic, and Lower Cretaceous rocks are the principal bedrock aquifers underlying the High Plains aquifer. The relationship between 

the High Plains aquifer and bedrock units is shown by 

the geohydrologic sections in figure 7. The north-south 

section along longitude 102° W. shows that these bedrock units are in contact with the base of the High 

Plains aquifer between the Arkansas and Cimarron 

Rivers and south of the Canadian River. The section 

along latitude 36°30' N. shows that these bedrock units 

also are in contact with the High Plains aquifer west 

of Beaver River. In the vicinity of the intersection of 

these two sections, the bedrock units have been uplifted (Irwin and Morton, 1969) and eroded. The erosional surface subsequently was covered by deposits 

that formed the High Plains aquifer. As a result of this 

geologic structure, water can move between the High 

Plains aquifer and bedrock sandstones where they are 

in contact.

FAULTS

The present mountain ranges are flanked by upturned sedimentary rocks and in many places by border 

faults. Faults have little effect on regional groundwater flow in the High Plains aquifer. Locally, faults 

are important because they affect aquifer thickness and 

productivity. The Wheatland and Whelan fault systems 

are of particular significance to the High Plains aquifer 

in Wyoming (fig. 4). According to Morris and Babcock 

(1960), the Wheatland and Whelan faults were formed 

by post-Miocene stresses along faults that were active 

during the Laramide revolution. The configuration of 

the bedrock surface has been altered greatly by the
GEOHYDROLOGY OF THE HIGH PLAINS AQUIFER 17

faults. Along the Wheatland fault, the bedrock has been 

displaced about 1,000 feet (fig. 6) and much of the Tertiary fill material on the down-thrown side is part of 

the High Plains aquifer. Faulting took place after deposition of the Tertiary bedrock, and sedimentation was 

probably about equal to the rate of faulting so that little 

surface expression was evident.

The White Clay fault is near the Nebraska-South 

Dakota State line. This normal fault occurred in at least 

two stages, the most recent of which occurred in middle 

Tertiary or later time (Dunham, 1961). Within the 

study area, as shown by figure 4, the bedrock on both 

sides of the fault is Tertiary age; the Arikaree Group 

is adjacent to the White River Group. Outside of the 

study area, Upper Cretaceous rocks are adjacent to the 

White River Group. The White Clay fault has caused 

about 500 feet of displacement in the aquifer base (fig. 

6). The Bear Creek and Crooked Creek faults shown 

on figure 4 are the result of salt dissolution discussed 

in the following section.

SALT DISSOLUTION

There are many evaporite beds in the Permian deposits underlying the High Plains. When geologic conditions are favorable, as when joints or fractures are 

present, the bedded salt is susceptible to dissolution 

by ground water. Subsequent collapse and filling of dissolution zones has affected aquifer thickness and the 

quality of ground water.

From the Arkansas River drainage in central Kansas 

to the Colorado River drainage in Texas, Permian salt 

deposits are being dissolved by circulating ground 

water. Saline water from Permian bedrock flows 

through the High Plains aquifer and the underlying 

bedrock to discharge along the Beaver, Cimarron, and 

Arkansas Rivers in Kansas and Oklahoma and the 

Canadian, all forks and branches of the Red, Peace, 

Wichita, Brazos, and Colorado Rivers that drain the 

High Plains in Texas. Gustavson (1980a, p. 71) estimated that the average annual solute discharge for 

streams draining the southern High Plains of Texas 

from 1969 to 1974 was 2.8 million tons of dissolved solids per year of which 66 percent (1.85 million tons per 

year) was salt (NaCl).

Ward (1963) and Johnson (1981) reported on the occurrence of salt plains and salt springs on the eastern 

edge of the High Plains in Oklahoma and Texas. 

Numerous salt plains caused by evaporation of saline 

water from Permian bedrock discharging at land surface occur on tributaries to the Arkansas and Red Rivers. According to Johnson (1981), individual salt plains 

release brines that contribute 110 to 3,300 tons of salt

per day that degrade the water quality in the Arkansas 

and Red River systems.

Sinkholes, depressions, and other collapse structures 

resulting from salt dissolution occur in many places. 

Surface manifestations of subsurface dissolution and 

collapse occur in Hall County, Texas, where more than 

400 sinkholes and undrained depressions have been 

identified from aerial photographs (Simpkins and 

others, 1981). Salt dissolution structures occur in southern Kansas, Oklahoma, and northern Texas.

Faulting and collapse structures associated with salt 

dissolution have formed since Permian time. Active 

sinkholes exist in the vicinity of Bear Creek and 

Crooked Creek faults. At land surface where unconsolidated materials are affected by collapse structures, concentric slump cracks and scarps outline areas of depression. Older collapse structures have been filled by 

younger material. For example, a collapse basin in Carson County, Texas, has been filled by several hundred 

feet of Ogallala Formation (shown by closed contour 

in fig. 6). Faults resulting from dissolution of evaporites 

in Permian deposits and collapse of the overlying rocks 

occur in Colorado, Kansas, and Oklahoma. Movement 

along these faults occurs as the edge of the dissolution 

zone is dissolved slowly by ground-water movement.

The Bear Creek fault crosses the Arkansas River 

twice in Colorado and Kansas. The Crooked Creek fault 

extends southward from Kansas into Oklahoma. Collapse along these faults has caused about 200 feet of 

displacement in the altitude of the aquifer base (fig. 

6). Salt dissolution in the vicinity of Crooked Creek 

fault results in large concentrations of chloride in 

ground water discharging to the Cimarron and Beaver 

Rivers. The concentration of chloride increases from 

215 to 580 mg/L in a 5-mile reach of the Cimarron 

River near Crooked Creek fault (Gutentag, Lobmeyer, 

and Slagle, 1981, p. 45).

GROUND-WATER HYDROLOGY

Primarily, geology and climate control the hydrology 

of the High Plains aquifer. The following sections of 

this report describe the hydrology of the aquifer and, 

where appropriate, relate hydrology to the geologic and 

climatic characteristics that control the availability and 

quality of ground water.

AQUIFER SYSTEM

The High Plains aquifer consists of one or more hydraulically-connected geologic units of late Tertiary or 

Quaternary age that contain sufficient saturated permeable material to yield significant quantities of water to 

wells and springs. The aquifer can be conceptualized
18 HIGH PLAINS RASA PROJECT

1D6° 105° 1D4° 1030 1D2° 101- 100° 99° on° 9?°

40°

39°

38°

AQUIFER 

BOUNDARY

EXPLANATION

 2000 BASE OF AQUIFER CONTOURShows altitude of aquifer base. 

Contour interval, in feet, is 

variable. Datum is sea level

FAULT Bar and ball on downthrown side

FIGURE 6. Altitude of base of the High Plains aquifer (modified from Weeks and Gutentag, 1981).
Land surface 

Unsaturated zone 

Water table 

Base of aquifer

0 50 100 MILES 

VERTICAL EXAGGERATION X240

HIGH PLAINS AQUIFER 

TERTIARY BEDROCK 

UPPER CRETACEOUS BEDROCK LOWER CRETACEOUS BEDROCK 

JURASSIC AND TRIASSIC BEDROCK 

PERMIAN BEDROCK

CONTACT Dashed where approximately 

located

O 

H 

O

Otr1 o

O

ffiHH

O

GO

> 

«O

FIGURE 7. Geohydrologic sections through the High Plains aquifer (from Weeks and Gutentag, 1981).
20 HIGH PLAINS RASA PROJECT

as a three-dimensional subsurface reservoir. The upper 

surface is the water table, the lower surface is the top 

of the bedrock, and the sides of the reservoir are the 

physical limits of the aquifer.

GEOMETRY

The configuration of the water table in the High 

Plains depicting the upper surface of the reservoir is 

shown in figure 8. Water-level data for this map were 

obtained during the winter and spring of 1980, when 

effects of seasonal pumping for irrigation were at a 

minimum. A larger scale map of the 1978 water table 

was published by Gutentag and Weeks (1980). There 

is little difference between the 1978 and 1980 maps because of the contour interval used to depict the water 

table.

Hydraulic interconnection between geologic units 

that comprise the High Plains aquifer is sufficient to 

permit contouring a continuous water table throughout 

most of the region. The degree of hydraulic interconnection may vary from place to place; and, locally, some 

water-yielding beds may have a water level representative of a confined pressure surface greater than that 

of the water table. However, from a regional aspect, 

water-table conditions prevail in the aquifer.

In a few areas, the aquifer is not saturated and the 

water table is discontinuous. Wells drilled in these 

areas will not yield water unless they penetrate saturated sediments in buried channels which were eroded 

into the bedrock. The major areas where there is little 

or no saturated aquifer material, are shown on the 

water-table map (fig. 8). The water table generally 

slopes eastward across the High Plains, which indicates 

that the general direction of ground-water flow is eastward.

The configuration of the base of the aquifer is shown 

in figure 6 which is reduced from a larger scale map 

by Weeks and Gutentag (1981). Because of the scale 

of the map, the contours showing the altitude of the 

base of the aquifer are generalized and only illustrate 

the principal topographic features of the surface upon 

which the High Plains aquifer was deposited.

In some areas, data are adequate to define the complex topographic surface of the rocks beneath the High 

Plains aquifer. In other areas, data are few and the 

contours are smooth. In areas with smooth contours, 

an intricately sculptured topographic surface would be 

revealed if the aquifer materials were stripped away 

and the surface underlying the aquifer was exposed. 

The contours illustrate the major predepositional drainage system in the region as well as the effects of faults 

and salt dissolution of the aquifer base. There is a general eastward slope of the aquifer base caused by mountain building and regional uplift during the last 70 million years.

The lateral boundaries of the ground-water reservoir 

are defined by the physical limits of the geologic units 

that comprise the aquifer or hydrologic boundaries 

where discharge occurs. The western boundary of the 

aquifer is a no-flow boundary because ground water 

generally flows eastward and escarpments isolate the 

aquifer from adjacent units except in Wyoming. In 

Wyoming, the western boundary of the aquifer is a noflow boundary because the adjacent geologic units are 

relatively impermeable. The eastern boundary of the 

aquifer is a flow boundary where water from the High 

Plains aquifer discharges to streams and springs.

The saturated thickness of the aquifer represents the 

vertical distance between the water table and base of 

the High Plains aquifer. A saturated-thickness map of 

the High Plains aquifer was prepared by superimposing 

1980 water-table contours over the altitude of the base 

of aquifer map and constructing lines of equal saturated 

thickness. The resulting map is presented in figure 9, 

which shows the 1980 areal variation of saturated thickness. Each thickness interval shows the range in thickness of the aquifer that predominates in that area. Because of map scale, it is not possible to show small 

areas where saturated thickness may be more or less 

than that indicated. The 1980 saturated-thickness map 

was published at a larger scale by Weeks and Gutentag 

(1981).

Saturated thickness ranges from zero where the deposits comprising the High Plains aquifer are unsaturated to about 1,000 feet in west-central Nebraska. The 

percentage of the area of the High Plains aquifer within 

each saturated-thickness interval is summarized by 

State in table 2. The tabulated results show that 46 

percent of the High Plains aquifer has less than 100 

feet of saturated thickness whereas only 5 percent has 

more than 600 feet of saturated thickness. With the 

exception of Nebraska, at least 40 percent of the High 

Plains aquifer in each State has less than 100 feet of 

saturated thickness. Significant areas where the saturated thickness of the aquifer is greater than 600 feet 

occur only in Nebraska and Wyoming.

The volume of saturated aquifer material contained 

in the ground-water reservoir also is summarized in 

table 2. The total volume of saturated material in the 

High Plains aquifer is 21.8 billion acre-ft, of which 

about 64 percent is in Nebraska and only 1 percent 

is in New Mexico. Based on the volume of saturated 

material and the area of the aquifer, the average saturated thickness of the High Plains aquifer is about 200
GEOHYDROLOGY OF THE HIGH PLAINS AQUIFER 21

706°

-1^1_____!04° 103° 102° 101° 100° 99°

96°

EXPLANATION

3200- WATER-TABLE CONTOURShows altitude of water table. 

Contour interval, in feet, is 

variable. Datum is sea level 

AREA OF LITTLE OR NO SATUR - 

ATED THICKNESS

FIGURE 8. Water table in the High Plains aquifer, 1980
22 HIGH PLAINS RASA PROJECT

38°

EXPLANATION

SATURATED THICKNESS,

IN FEET 

0-100

37°

FIGURE 9. Saturated thickness of the High Plains aquifer, 1980 (modified from Weeks and Gutentag, 1981).
GEOHYDROLOGY OF THE HIGH PLAINS AQUIFER 23

feet. The saturated thickness of the aquifer in Nebraska averages about 340 feet. In the area excluding 

Nebraska, the saturated thickness of the aquifer averages about 110 feet.

HYDRAULIC CHARACTERISTICS

Hydraulic conductivity and specific yield are the two 

principal hydraulic characteristics that control groundwater flow in a water-table aquifer. In order to quantitatively analyze flow in the High Plains aquifer, a 

knowledge of the values of these characteristics and 

their distribution within the aquifer is required. Both 

hydraulic conductivity and specific yield depend on the 

character of the sediments that comprise the aquifer; 

therefore, their values can be expected to vary both 

horizontally and vertically according to the variation in 

sediment types.

Hydraulic conductivity is defined as the rate of flow 

of water in cubic feet per day through a cross-sectional 

area of 1 ft2 under a hydraulic gradient of 1 foot per 

foot at a temperature of about 15°C. Specific yield is 

defined as the ratio of (1) the volume of water that 

the saturated rock will yield by gravity drainage to (2) 

the total volume of saturated rock. Specific yield is expressed as a dimensionless fraction or percentage. The 

difference between porosity and specific yield is known 

as specific retention which is defined as the ratio of 

(1) the volume of water retained in the rock after gravity drainage to (2) the total volume of the saturated 

rock. Both hydraulic conductivity and specific yield depend on particle size, shape, sorting, and cementation 

of the aquifer material.

One of the principal objectives of the High Plains 

study is to develop a computer model of the aquifer 

system. Before a computer model of the High Plains 

aquifer can be developed, it is necessary to determine 

whether the vertical distribution of sediment types 

within the aquifer is random or nonrandom. A method 

was devised by Gutentag and Weeks (1981) to evaluate 

vertical variability using estimates of hydraulic conductivity and specific yield based on drillers' logs. The 

method requires statistical computations that describe 

the vertical distribution of aquifer characteristics determined from drillers' logs.

The method consists of calculating the center of gravity (first moment) and the variance (second moment) 

of the distribution of transmissivity (product of hydraulic conductivity and thickness) and storage depth (product of specific yield and thickness) relative to the base 

of aquifer. The center of gravity indicates the position 

of the centroid of distribution of the aquifer characteristic within the geologic section; the variance is a measure of variability of the aquifer characteristic about the

center of gravity. Thus, a center of gravity of 0.5 (onehalf the saturated thickness) indicates that the aquifer 

characteristic is equally distributed about the centroid 

of the vertical section. If the mean center of gravity 

determined from a group of drillers' logs is not significantly different from 0.5, then the aquifer characteristic 

(and the sediments that control the characteristic) is 

distributed randomly in the vertical section. A random 

distribution (all sediment types are equally likely to 

occur at any position in the vertical section) can be 

modeled using vertically-averaged aquifer characteristics. A nonrandom distribution (one sediment type is 

more likely to occur at a particular position in the vertical section than any other sediment type) can be modeled by developing relationships between vertical position and each aquifer characteristic.

Several thousand drillers' logs from the High Plains 

aquifer were analyzed using the procedure described 

above. Hydraulic conductivity and specific yield values 

were assigned to each lithologic interval described on 

each log. A computer program was developed and used 

to calculate the statistics from groups of logs from each 

of the eight States in the High Plains. The results of 

this analysis are presented in table 3 which indicates 

that the centers of gravity of both transmissivity and 

storage depth are not significantly different from 0.5.

The method also was tested in Texas by Ashworth 

(1980) for wells drilled by the Texas Department of 

Water Resources using drill-hole samples and laboratory analyses. Using these controlled samples at 41 sites 

in 36 counties, the average centers of gravity for both 

transmissivity and specific yield were not significantly 

different from 0.5. Ashworth (1980, p. 20) concluded 

that " *** there is not an overall relationship between 

permeability and depth within the Ogallala Formation." 

Ashworth (1980, p. 20) also noted that specific yield 

was found to have little variance throughout the saturated zone.

Based on these results, the authors have concluded 

that on a regional scale, the sediments that comprise 

the aquifer are distributed randomly in the vertical section. Therefore, the aquifer can be modeled in two dimensions using vertically-averaged values of hydraulic 

conductivity and specific yield. Because the distribution 

of sediment types within the High Plains aquifer is virtually random, it is likely that the dominant mode of 

deposition of the aquifer was by braided streams, probably as individual valley stream deposits that coalesced 

to form broad alluvial fans. Coarsening-upward and fining-upward sediments are characteristic of braided 

stream deposits and would result in a random distribution of sediment types in the vertical section.
24 HIGH PLAINS RASA PROJECT

TABLE 2. Distribution and volume of saturated material, High Plains aquifer, 1980

[Modified from Weeks and Gutentag, 1981]

Area of _. ^ .. ... . ._ ^ > ,. i *. -, Volume of 

 .,_., . Percentage of area within each saturated thickness interval . . , High Plains 6 saturated

State aquifer 

within State 

(square 

miles)

New Mexico 

South DakotaTotal 

1 14,900 

2 30,500 

63,650 

3 9,450 

7,350 

4,750 

35,450 

8,000

4 174,050

0- 

100 

feet

76 

66 

14 

85 

58 

44 

61 

46

46

100- 

200 

feet

18 

21 

21 

15 

25 

13 

25 

26

22

200- 400- 600- 800- 

400 600 800 1,000 

feet feet feet feet

6 

12 1 

29 22 10 4

11 6 

25 18 

14 

18 4 4 2

18 9 4 1

aquifer 

material 

(millions of 

acre-feet)

750 

2,000 

14,000 

320 

610 

700 

2,500 

920

21,800

Includes 1,200 square miles with little or no saturated thickness.

2 Includes 3,200 square miles with little or no saturated thickness.

3 Includes 2,600 square miles with little or no saturated thickness.

4 Includes 7,000 square miles with little or no saturated thickness.

The areal distribution of hydraulic conductivity is 

shown in figure 10. The range in values shown on the 

map represent the average hydraulic conductivity estimated from drillers' logs. Local changes in lithologic 

character of the High Plains aquifer result in local hydraulic conductivity changes too variable to show on 

the scale of this map. The average hydraulic conductivity for the area of the High Plains aquifer in each State 

and the percentage of the area within each hydraulic 

conductivity interval are listed in table 4. As shown 

by figure 10 and table 4, the hydraulic conductivity of 

most (68 percent) of the aquifer is 25 to 100 ft/d, although the values range from less than 25 to 300 ft/d.

Differences in hydraulic conductivity in figure 10 reflect areal variations in lithology. Hydraulic conductivity values were assigned to lithologic descriptions from 

drillers' logs based on the data in table 5, which was 

modified from a table of values prepared for professionally collected sample logs by Reed and Piskin that was 

published by Lappala (1978). Values for hydraulic conductivity (and specific yield) in table 5 were adjusted 

for local conditions based on aquifer-test data, local drillers' terminology, and experience of the hydrologist 

who analyzed the data. The data in table 5 show that 

fine-grained deposits have much smaller hydraulic conductivities than coarse-grained deposits. Thus, the 

quantity of fine-grained material interspersed with 

coarse-grained material controls permeability. The values of hydraulic conductivity in table 5 are less for various lithologic mixtures of coarse- and fine-grained material than for well-sorted material.

The procedure used to estimate the average hydraulic conductivity from drillers' logs requires the calculation of a thickness-weighted average value. Hydraulicconductivity values were assigned to each lithologic 

unit described by a drillers' log. Each value was multiplied by the thickness of the corresponding lithologic 

unit to obtain the transmissivity of that unit. The transmissivities of the individual units were summed for the 

saturated section, and the total was divided by the 

saturated thickness to obtain the average hydraulic 

conductivity. These average values, supplemented with 

data from aquifer tests, were used to prepare the hydraulic conductivity map (fig. 10). Thus, a heterogeneous mixture of fine and coarse material can be expected 

at any site; and, test drilling would be necessary to 

determine whether or not the lithology of the aquifer

TABLE 3. Statistics on the vertical distribution of transmissivity 

and storage depth in the High Plains aquifer

State Number 

of logs

Transmissivity

Mean center Standard 

of gravity deviation

Storage depth 1

Mean center Standard 

of gravity deviation

Colorado -----

Nebraska----- 

New Mexico--- 

Oklahoma ----- 

South Dakota804

88 

58 

682 

205

0.46

.52 

.47 

.47 

.51

0.08

.10 

.13 

.11 

.10 

.10

.11

0.48

.51 

.49 

.48 

.51

Kn

0.06

.06 

.08 

.08 

.08

Total 3,076 0.48 0.10 0.49 0.07

1 Product of specific yield and thickness.
GEOHYDROLOGY OF THE HIGH PLAINS AQUIFER 25

105° 104" 1030 102° 101 o 100° 99' 97° 96°

43°

40'

38°

HYDRAULIC CONDUCTIVITY,

IN FEET PER DAY 

0-25

AREA OF LITTLE OR NO

SATURATED THICKNESS

FIGURE 10. Areal distribution of hydraulic conductivity in the High Plains aquifer.
26 HIGH PLAINS RASA PROJECT

TABLE 4. Distribution of average hydraulic conductivity in the High 

Plains aquifer

. , Percentage of area within each 

H' h6 pl°' hydraulic-conductivity interval Average

within" withm tate ° 25 10° 20° conductivity State t (f t d }

(square miles) 25 ]00 20Q 3QO

South Dakota 4,750 69 31 28

at a selected site indicated a potential yield to wells 

adequate for the intended use. 

The area! distribution of specific yield is shown in 

figure 11. The range in values shown on the map represents the average specific yield determined from drillers' logs. As with hydraulic conductivity, the specific 

yield is greatly affected by changes in lithology. Local 

changes in lithology result in local changes in specific 

yield too variable to show on the scale of this map. 

Average specific yield for the area of the High Plains 

aquifer in each State and the percentage of the area 

within each specific yield interval are presented in table 

6, which was prepared from a more detailed map than 

figure 11. As shown by the data in figure 11 and table 

6, the specific yield of most (76 percent) of the aquifer 

is 10 to 20 percent, although the values range from 

less than 5 to 30 percent and average 15. 1 percent.

TABLE 5. Hydraulic-conductivity and specific-yield values assigned 

to lithologic descriptions of the High Plains aquifer

Hydraulic Specific 

Lithologic description conductivity yield 

(feet per day) (percent)

TABLE 6. Distribution of average specific yield in the High Plains 

aquifer

. , Percentage of area within 

... . , , each specific-yield interval Average

State .?*» f£ t 0 5 10 15 20 25 yield'''

(s^g are" miS to to to to to to <P ercent > isquare mi les) 5 1Q ]5 2Q 25 3Q

Nebraska 63,650 2 6 36 49 6 1 15.2

New Mexico 9,450 -- 4 54 35 7 14.8 

Oklahoma 7,350 2 13 49 35 1 18.5

South Dakota 4,750 26 35 22 14 3 9.2

Total 174,050 3 10 32 44 10 1 15.1

Differences in specific yield in figure 11 reflect areal 

variations in lithology. Specific-yield values were assigned to lithologic descriptions from drillers' logs using 

table 5. These values were determined from a study 

on specific yield by Johnson (1967) and studies of the 

relation between lithology and specific yield in the High 

Plains of Nebraska made by the U.S. Geological Survey 

(M. J. Ellis, U.S. Geological Survey, written commun., 

1978). The data in table 5 illustrate that fine-grained 

deposits have less specific yield than coarse-grained deposits, because specific retention increases as grain-size 

decreases. The same procedure used to calculate average hydraulic conductivity from drillers' logs was used 

to determine average specific yield from logs using the 

data in table 5. These average values then were used 

to construct figure 11. 

Both hydraulic-conductivity (fig. 10) and specificyield (fig. 11) maps show complex areal variations that 

are the result of the complex depositional history of 

the aquifer. Most of the High Plains aquifer consists 

of semiconsolidated to unconsolidated deposits resulting 

from several cycles of deposition. Consequently, there 

are few areas where the hydraulic conductivity and specific yield maps can be used to interpret the depositional environment of the aquifer. Near the NebraskaKansas State line, both hydraulic-conductivity and specific-yield values are large, because the Republican 

River has eroded the Ogallala Formation, and only alluvial deposits are present. In parts of Colorado, Nebraska, South Dakota, and Wyoming, both hydraulicconductivity and specific-yield values are small because 

the aquifer primarily consists of consolidated rocks of 

the Arikaree and Brule Formations (fig. 3).

FLOW SYSTEM

The hydraulic characteristics described in the previous section control the storage and movement of water
106°

105

GEOHYDROLOGY OF THE HIGH PLAINS AQUIFER

103° 102° 101" 100° 99° 98°

27

970 96°

43°

39° U_ c$7 COLORADO

SPECIFIC YIELD, IN

PERCENT 

0-10

AREA OF LITTLE OR NO

SATURATED THICKNESS

FIGURE 11. Areal distribution of specific yield in the High Plains aquifer.
28 HIGH PLAINS RASA PROJECT

in the High Plains aquifer. In addition, recharge to and 

discharge from the aquifer control the long-term availability of ground water. For example, when recharge 

exceeds discharge, the quantity of water in storage increases and the water table rises. Conversely, when 

discharge exceeds recharge, the quantity of water in 

storage decreases and the water table declines. Prior 

to man's activities, the ground-water reservoir operated under natural conditions. That is, the water table 

was near equilibrium and the quantity of water stored 

in the reservoir was relatively constant, varying only 

in response to changes in annual precipitation, 

streamflow, and vegetation. This section discusses 

ground-water movement (including recharge and natural discharge) and storage.

Prior to development of ground water by wells, the 

water table in the High Plains aquifer was near equilibrium or steady-state. The predevelopment water table 

is shown in figure 12. The map was constructed from 

water-level data collected prior to significant development of irrigation wells in the High Plains. Development generally progressed northward from New 

Mexico and Texas during the 1930's, to Oklahoma and 

Kansas during the 1940's, and Colorado, Nebraska, and 

Wyoming during the 1950's and 1960's. Significant development has not yet occurred in South Dakota. At 

the scale of this map, there is little difference between 

figure 12 and the 1980 water-table map in figure 8 except for a slight westward displacement of the 1980 

water-table contours caused by pumpage. Consequently, the following discussion generally applies to 

both current and predevelopment conditions.

Ground-water flow in the High Plains aquifer generally is from west to east in response to the hydraulic 

gradient or slope of the water table. The flow pattern 

is shown by arrows in figure 12. The general direction 

of ground-water movement is at right angles to the 

water-table contours in the direction of greatest slope. 

Based on average values of hydraulic gradient and 

aquifer characteristics, the velocity of water moving 

through the aquifer is about 1 ft/d, which is typical of 

sand and gravel aquifers.

The configuration of the water-table contours in figure 12 is controlled by several factors, including (1) 

slope of the bedrock base of the aquifer, (2) changes 

in the thickness and hydraulic conductivity of saturated 

materials, (3) discharge of ground water into streams, 

(4) recharge to the aquifer from streams, and (5) recharge by infiltration of water through permeable soils. 

Typically, many of these factors control the water-table 

configuration in any particular area. For example, 

along the western border of the High Plains, especially 

in southeastern Wyoming, the steep slope of the water

surface may be the result of low permeability, reduced 

thickness of water-bearing materials, a steep slope of 

the bedrock surface, or a combination of these factors. 

Flattening of the gradient near the eastern border of 

the High Plains, may be due to high permeability of 

the material through which the water is moving, increased thickness of water-bearing materials, a decrease in slope of the bedrock surface, or a combination 

of these factors.

Up-gradient flexures of water-table contours near 

streams indicate ground water flows toward and discharges into streams. This is most evident along the 

North Platte River and Platte River west of 99° W. 

longitude and along the Canadian River in Texas. 

Down-gradient flexures of water-table contours near 

streams indicate water flows from streams into the 

aquifer. The 2,000-foot contour crossing the Platte 

River in Nebraska and the Arkansas River in Kansas 

(fig. 12) shows this condition. Lack of flexures in areas 

where contours cross stream valleys may indicate that 

the water table is below the streambed. This condition 

is true for most ephemeral (intermittent) streams in 

the High Plains.

Down-gradient flexures or increased spacing of 

water-table contours in areas away from perennial 

streams in figure 12 indicate differences in recharge by 

infiltration of water through the overlying soil profile. 

Recharge is indicated by the water-table contours in 

areas covered by dune sand in Colorado, Kansas, and 

Nebraska, and to a lesser extent in New Mexico, Oklahoma, and Texas (compare figures 3 and 12). The 

spacing and flexures of the water-table contours north 

of the Platte River in Nebraska indicate that large 

quantities of recharge to the aquifer occur in this area 

covered by dune sand.

Ground water from the High Plains aquifer discharges naturally to streams and to springs and seeps 

along the eastern escarpment. Streams that originate 

in the High Plains generally are ephemeral in their upstream reaches and perennial where their channels are 

incised to the water table. The Niobrara, Loup, Republican, Smoky Hill, Red, and Brazos Rivers (fig. 1) are 

among those streams that have their headwaters on the 

High Plains. Some streams draining the High Plains 

the Platte, Arkansas, Cimarron, Beaver, and Canadian 

Rivers (fig. 1) have headwaters in the mountains to 

the west; but, of these, only the Platte River is perennial throughout its course across the High Plains.

The importance of ground-water discharge to 

streamflow in the Platte River is illustrated for the 

1975 water year in figure 13 modified from Bentall and 

Shaffer (1979). Downstream from the confluence of the 

North Platte and South Platte Rivers, there is little
'06° 105°

GEOHYDROLOGY OF THE HIGH PLAINS AQUIFER

103° 102° 101° 100° 99°

29

97° 96°

43°

42°

AQUIFER 

BOUNDARY im:

 3200 WATER TABLE CONTOURShows altitude of water table. 

Contour interval, in feet, is 

variable. Datum is sea level. 

Arrow shows direction of 

ground-water flow. 

AREA OF LITTLE OR NO SATURATED THICKNESS

FIGURE 12. Predevelopment water table and direction of ground-water flow in the High Plains aquifer.
30 HIGH PLAINS RASA PROJECT

[EXPLANATION

RIVER DISCHARGE INDICATED 

BY COLOR WIDTH

I I I I I I 

MILLIONS OF ACRE-FEET

 ^v _J_________________1_____________

50 100 150 200 KILOMETERS

I i_____i ____I

FIGURE 13.

0 50 100 MILES 

-Discharge in the Platte River drainage, 1975 water year (modified from Bentall and Shaffer, 1979).

surface-water runoff and the gain in streamflow is 

mostly the result of ground-water discharge from the 

High Plains aquifer. Streamflow in the Loup River system is almost entirely from ground-water discharge 

from the sand-dune area in central Nebraska. As shown 

in figure 13, the gain in streamflow in the Platte River 

drainage in Nebraska was about 3 million acre-ft during 

the 1975 water year, most of which was from groundwater discharge. Considering that large quantities of 

water are diverted and consumed by irrigation, groundwater discharge to streams in the Platte River drainage 

in Nebraska must have been significantly greater than 

the apparent gain in streamflow shown in figure 13.

Discharge from the aquifer also occurs in areas where 

the water table is near enough to the land surface to 

permit evapotranspiration directly from ground water. 

Ground-water discharge by evapotranspiration is greatest in areas where phreatophytes such as salt cedar, 

willows, cottonwoods, and sedges grow mainly along 

stream valleys. In the area of sand hills in Nebraska,

evaporation from numerous lakes in hydraulic connection with the aquifer represents ground-water discharge. The water table is so close to land surface in 

many places in the sand hills that ground-water discharge by evapotranspiration may equal or exceed that 

of seepage into streams (Sniegocki, 1959).

Although greatly exaggerated, the east-west sections 

in figure 7 show the eastward slope of the aquifer base. 

Ground water moves regionally under the force of gravity in the general direction of the slope of the aquifer 

base to discharge areas along streams or the aquifer 

boundary.

As shown on the north-south section (fig. 7), the 

North Platte River at Lake McConaughy and the 

Arikaree, Arkansas, and Canadian Rivers have cut 

their channels through the aquifer into bedrock. These 

streams in addition to the South Platte, North Loup, 

Elkhorn, and North Fork Solomon Rivers are gaming 

streams at the locations shown in figure 7. At other 

locations, these and most other streams in the High
GEOHYDROLOGY OF THE HIGH PLAINS AQUIFER 31

Plains are losing streams, such as the Beaver and 

Cimarron Rivers in figure 7, and may provide recharge 

to the aquifer during periods of runoff.

Recharge is the difference between the volume of 

water that enters the soil profile and the volume of 

water that leaves the soil by evapotranspiration. 

Evapotranspiration includes evaporation from the soil 

and transpiration through plants. As shown in figure 

2, pan evaporation in the High Plains is much greater 

than precipitation; therefore, most precipitation during 

the growing season returns to the atmosphere by 

evapotranspiration and little or no recharge occurs depending on the capacity of the soils to store water. 

Sandy soils generally have large infiltration rates, high 

permeability, and low field capacity (moisture storage). 

A generalized soils map of the High Plains is shown 

in figure 14. Most soils have developed on dune sand 

or loess. It is probable that the sandy-soil areas shown 

in figure 14 are important recharge areas for the High 

Plains aquifer.

Recharge to the aquifer also is derived from 

streamflow. During periods of normal precipitation, 

practically no runoff collects in channels of ephemeral 

(intermittent) streams. However, after exceptionally 

intense rains, the streams may, in some places, transport large quantities of water. During these rare flows, 

large quantities of water infiltrate into channel and 

flood-plain deposits and part of the water probably percolates downward to recharge the aquifer. Gillespie and 

Slagle (1972) evaluated recharge from Wet Walnut 

Creek south of La Crosse, Rush County, Kansas (fig. 

1). Their study showed that recharge to the aquifer 

during low-flow periods was only about 0.05 ft3,s per 

mile of stream channel although recharge from high 

flows can be substantial. They noted water-level rises 

in observation wells ranging from 4 to 14 feet following 

high-flow periods. Gillespie and Slagle (1972, p. 91) concluded that most of the recharge from Wet Walnut 

Creek results from high flows. In a related project, Jordan (1977) studied transmission losses of flood flows in 

ephemeral channels in western Kansas. He estimated 

the average transmission loss to be 1.3 percent of the 

flow per mile of stream channel.

Based on the above research, it is probable that high 

flows in ephemeral streams also are important sources 

of recharge to the High Plains aquifer. Although 

ephemeral streams are intermittent sources of recharge, it is possible that a few high flows per decade 

or century may be a principal source of recharge to 

the aquifer.

Recharge estimates for the High Plains aquifer are 

listed in table 7. Values are listed by State and authors. 

The values represent only a small part of the extensive 

work on the subject. The estimated recharge rates

range from 0.024 inch per year in Texas to 6 inches 

per year in south-central Kansas. In terms of percentage of mean annual precipitation, the estimates range 

from 0.1 to 20 percent. Even within individual States, 

the estimates vary considerably. However, the estimates presented in table 7 consistently show higher recharge rates in areas with sandy soils.

The estimates of recharge presented in table 7 generally result in a long-term average recharge rate. However, depending on the period of analysis, the recharge 

rate can vary considerably. This is illustrated in table 

7 by estimates for Finney County, Kansas, by Meyer 

and others (1970). Based on the analysis of water-level 

changes in wells between 1940 and 1952 (a period of 

greater than normal precipitation), they estimated the 

average recharge rate to be 1.4 inches per year. In 

the same study using the water-budget method, the authors estimated the long-term average recharge rate 

to be only 0.05 inch per year. If the long-term average 

recharge rate is 0.05 inch per year, then one period 

of recharge of the same magnitude as that during 1940- 

52 occurring every 336 years would contribute enough 

recharge to account for the long-term average recharge 

rate.

Differences in recharge estimates also are shown in 

table 7 for Washington County, Colorado. McGovern 

(1964) estimated the long-term average recharge rate 

to be 0.95 inch per year based on a water-budget analysis. Longenbaugh and Krishnamurthi (1975) calculated 

recharge for 1969-73 in Washington County using a 

soil-moisture model and three observation wells near 

an ephemeral stream. For the short study period, recharge was estimated to average 4 inches per year. The 

results showed larger rates of recharge below the 

ephemeral stream than away from the stream.

Based on the analyses referenced in table 7, recharge 

rates vary according to climatic, soil, and topographic 

conditions as well as the period of analyses. With the 

exception of areas of sandy soil and stream courses, 

the long-term average annual recharge to the High 

Plains aquifer under natural conditions is extremely 

small (a few tenths of an inch) and probably results 

from infrequent climatic events that cause relatively 

large quantities of recharge during relatively short 

periods of time.

Water in storage in the High Plains aquifer varies 

in response to changes in ground-water discharge and 

recharge. The volume of drainable water in storage in 

the High Plains aquifer in 1980 can be estimated by 

multiplying the volume of saturated material (table 2) 

by the average specific yield (table 6). The product 

shown by State in table 8, is an estimate of the volume 

of drainable water in storage in 1980. The distribution 

of drainable water in storage is not uniform. The data
32

106° 105<

HIGH PLAINS RASA PROJECT

104° 103° 102° 101° 100° 99°

97°

43°

390 I _ c§f COLORADO

EXPLANATION

CLAY LOAM

LOAM

SILT LOAM

SANDY LOAM

SAND

CALICHE

AQUIFER 

BOUNDARY \/:/:f:^^/-:^ l-:'':'.''.-'-\^i^>i

FIGURE 14. Soil types in the High Plains.
GEOHYDROLOGY OF THE HIGH PLAINS AQUIFER 

TABLE 7. Recharge estimates for the High Plains aquifer

33

Recharge

State , i ncnes In percentage Reference

r, 0 v, ,,, °f mean annual 

Per year precipitation

Colorado 0.80 to 0.95 

0.95 

0.82

4.0 

0.59

Kansas 6.0

0.30 

1.40

0.05 

0.19

0.28 

0.6 

1.85

Nebraska-- 0.75 to 1.00

5.0 

1.0

0.50 to 0.75 

0.72 

2.40

2.0

5 

5 

5

23 

2

20

2

8

0.3

1

1.5 

3

n

4 to 6

19 

5

2 to 3 

3 

11

10

McGovern and Coffin (1963) -

McGovern (1964) 

Reddell (1967) 

Longenbaugh and Krishnamurthi 

(1975).

Williams and Lohman (1949) 

Fader and others (1964) 

Gutentag and Stullken (1976)--

Barker and others (1983) 

Cady (1940) 

Cardwell and Jenkins (1963) 

Huntoon (1974) 

Emery (1966) 

Lappala (1978) 

Fred Otradovsky (U.S. Bureau

Remarks

Northern High Plains, water-budget method. 

Washington County, water-budget method. 

Northern High Plains, county averages range from 0.15 

(Kiowa) to 1.45 inches per year (Yuma), computer-model 

analysis. 

Washington County, sandy soils, computer-model analysis.

Cheyenne and Kiowa Counties, computer-model analysis.

Quaternary deposits, south-central Kansas, sandy soils, 

water-budget method. 

Grant and Stanton Counties, water-budget method. 

Finney County, value for 1940-52 wet period, data from 

well hydrographs.

Lane and Scott Counties, water-budget method for dryland 

areas. 

Wichita County, computer-model analysis. 

Pawnee River valley, computer-model analysis. 

Arkansas River valley and adjoining sand hills, for dryland areas, computer-model analysis.

Box Butte County, flow-line analysis for water-budget 

method. 

Loup River drainage in sand hills, water-budget method. 

Frenchman Creek area of Colorado and Nebraska, waterbudget method. 

Big Blue area, computer-model analysis. 

Big Blue area, analog-model analysis. 

Upper Republican Natural Resources District, computermodel analysis. 

Sand hills, Box Butte County, computer-model analysis.

5.0 22 

1.1 to 2.8 6 to 16

of Reclamation, oral commun.

1981). 

Fred Otradovsky (U.S. Bureau

of Reclamation, oral commun.,

1981). 

R. A. Pettijohn and H. H. Chen

(U.S. Geological Survey,

oral commun., 1982).

Sand hills, Holt County, computer-model analysis.

Box Butte County, computer-model analysis, clayey soil-- 

1.1 inches per year for cropland and 1.6 inches per 

year for native grassland; sandy soil 2.4 inches per 

year for cropland and 2.8 inches per year for native 

grassland.

South 

Dakota.

0.5

0.39

0.25 to 0.50

0.20 to 2.2

1.3 to 1.8

0.50

0.06 

0.175

4

6 

2.5

1 to 2

1 to 12

7 to 10

3

0.3

1

Theis (1937) 

Havens (1966) 

Lansford and others (1974) 

Hart and others (1976) 

Morton (1980) 

K. E. Kolm (U.S. Geological 

Survey, oral commun., 1981).

Theis (1937) 

White and others (1946) 

W. F. Guyton, cited by Rayner

method.

method. 

Southern High Plains, computer-model analysis.

Southwestern South Dakota, computer-model analysis.

adjusted to Texas precipitation, water-budget method.

Parmer County, water-budget method.

0.024 to 0.072 0.1 to 0.4

0.183 1

0.50 3

1.00 5

and others (1973). 

Brown and Signer (1973)-

Brutsaert and others (1975)--

Texas Department of Water 

Resources (1981) county 

reports.

Texas Department of Water 

Resources (1981) county 

reports.

Southern High Plains of Texas and New Mexico, water-budget

method. 

C. E. Jacob's analysis for tax depletion court case,

Southern High Plains, water-budget method 

0.5 inch per year recharge used in computer-model analysis

of: Armstrong, Carson, Dallam, Deaf Smith, Donley, Gray,

Hansford, Harley, Hemphill, Hutchinson, Lipscomb, Moore,

Ochiltree, Oldham, Potter, Randall, Roberts, Sherman,

and Wheeler Counties. 

1.0 inch per year recharge used in computer-model analysis

for the other 23 counties in the High Plains.

Wyoming 0.83

0.56

0.17

5.5 

3.6 

2

Morgan (1946)--- 

Crist (1977) - 

Borchert (1977)-

Cheyenne area, water-budget method.

High Plains aquifer, Niobrara County, water-budget method. 

Arikaree Formation, central Wyoming, computer-model 

analysis.
34 HIGH PLAINS RASA PROJECT

TABLE 8. Distribution of drainable water in 

storage in the High Plains aquifer, 1980

State

Colorado-- --

licU Tab K.a

I exas

Drainable water 

in storage

Percent

3.7

r r r

1.5

1.9

12.0 

o r>

Millions of 

acre- feet

120 

320 

2,130 

50

no

60 

390

Total- 100.0 3,250

in table 8 show that Nebraska, with 36 percent of the 

land area in the High Plains, contains 65.5 percent of 

the drainable water in storage in the High Plains 

aquifer. Texas, with 20 percent of the land area in the 

High Plains, has only 12 percent of the drainable water 

in storage. New Mexico, with 1.5 percent of the drainable water, has the least volume of water in storage 

in the High Plains aquifer. The regional variability in 

the distribution of water in storage can be seen by 

examining the saturated-thickness map shown in figure 

9 and the geohydrologic sections shown in figure 7. The 

total volume of drainable water in storage in the High 

Plains aquifer was estimated at 3.25 billion acre-ft for 

1980.

All the drainable water in storage in the High Plains 

aquifer cannot be recovered for use. The volume of 

water that can be removed from the aquifer is site specific and depends on the lithology of the site, well construction, saturated thickness, hydraulic conductivity, 

and specific yield. Because most of the water is used 

for irrigation, energy costs, well yield, and water quality also need to be considered.

WATER QUALITY

The High Plains aquifer is the only source of water 

for irrigation in most of the High Plains. About 95 percent of all water used for irrigation in the study area 

is pumped from the High Plains aquifer. The agricultural economy of the High Plains depends, in part, on 

the availability of large quantities of ground water of 

suitable quality for irrigation. Concentrations of dissolved solids and sodium are of particular importance to 

irrigation use. Excessive concentrations of dissolved 

solids affect plant growth; excessive concentrations of 

sodium affect plant growth and decrease soil tillability 

and permeability.

Dissolved-solids and sodium concentrations are a hazard to irrigation in the southern part of the High Plains 

in Texas and in small areas in the High Plains in each 

of the other seven States. Hazardous concentrations of 

dissolved solids and sodium occur naturally, except 

along major streams, where irrigation practices concentrate dissolved constituents.

DISSOLVED SOLIDS

As a result of geochemical and biochemical interactions between water and the geologic materials through 

which it flows, ground water contains a variety of dissolved inorganic chemical constituents. The concentration of dissolved solids in ground water can vary by 

many orders of magnitude. A simple method for 

categorizing ground water based on dissolved-solids 

concentration is presented below (Winslow and Kister, 

1956).

Category

Concentration of dissolved

solids, in milligrams

per liter

Fresh

Slightly saline 

Moderately saline 

Very saline 

Brine

Less than 1,000

1,000-3,000

3,000-10,000

10,000-35,000

More than 35,000

To put the concentration ranges in perspective, 

water containing more than 2,000 to 3,000 mg/L dissolved solids generally is too mineralized to drink (Freeze 

and Cherry, 1979). The U.S. Environmental Protection 

Agency commended limit for dissolved solids in drinking-water supplies is 500 mg/L. Most crops can tolerate 

water with as much as 500 mg/L dissolved solids without adverse effects; if leaching or drainage is adequate, 

concentrations of 500 to 1,500 mg/L are not likely to 

be harmful (U.S. Salinity Laboratory Staff, 1954).

The areal distribution of dissolved-solids concentration in water from the High Plains aquifer is shown 

in figure 15, which is reproduced here from a largerscale map by Krothe and others (1982). Each interval 

on the map shows the range in concentration that predominates in that area. The chemical composition of the 

water at selected sites in the High Plains aquifer is 

presented in table 9 and located by number in figure 

15. As shown in table 9, concentrations of sulfate, 

chloride, fluoride, nitrate, and dissolved solids exceed 

the U.S. Environmental Protection Agency (1976, 1977)
GEOHYDROLOGY OF THE HIGH PLAINS AQUIFER 35

DISSOLVED-SOLIDS CONCENTRATION, IN MILLIGRAMS 

PER LITER 

LESS THAN 250

250-500

500-1000

MORE THAN 1000

.5 SAMPLE SITE-Number refers 

to table 9

200 KILOMETERS

100 MILES

FIGURE 15. Dissolved-solids concentration in water from the High Plains aquifer 

(from Krothe and others, 1982).
36 HIGH PLAINS RASA PROJECT

TABLE 9. Chemical analyses of selected water samples from the High Plains aquifer

[From Krothe and others (1982); values are in milligrams per liter except as indicated; itmhos, micromhos at 25° Celcius; values underlined exceed U.S. Environmental Protection 

Agency drinking-water regulations, 1976-1977; ARKR=Arikaree Formation or Group; OGLL=Ogallala Formation, SDGV=Quaternary sand and gravel deposits]

Sample 

number 

shown in 

figure 15

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

Geologic 

unit

ARKR

ARKR

SDGV

OGLL

OGLL

OGLL

OGLL

OGLL

SDGV

OGLL

OGLL

OGLL

OGLL

OGLL

OGLL

Well 

depth 

(feet)

96

100

245

200

250

200

321

100

100

40

260

170

569

150

104

Silica 

(SiD2 )

77

54

58

63

28

58

36

22

20

20

23

38

27

58

64

Calcium 

(Ca)

28

122

20

94

45

56

30

228

108

51

63

56

46

72

231

Sodium 

Magne- + 

sium Potas- 

(Mg) sium 

(Na+K)

8

29

3.3

14

5.5

15

10

114

21

20

19

34

18

20

225

66

38

12

21

6.4

19

27

226

114

35

245

17

37

44

845

Bicarbonate 

(HC03 )

230

446

94

336

157

200

181

184

248

180

210

215

243

221

282

Sulfate 

(S04 )

28

24

5.0

18

6.5

13

10

1,170

94

8.1

94

49

32

104

1^351

Chloride 

(CD

8.5

40

.3

18

2.8

3.9

3.0

143

177

30

350

46

28

43

1,109

Fluoride 

(F)

0.1

.5

.2

 

.4

.8

1.8

4.0

1.0

1.4

1.0

1.6

.8

1.5

4.0

Nitrate 

(N03 )

1.9

 

3.0

7.6

7.0

 

7.6

3.9

32

12

1.7

24

3.9

5.6

4.2

Dissolved 

solids 

(sum)

332

678

148

403

191

273

214

2,140

694

339

900

372

312

507

3.970

pH 

(units)

7.6

7.5

8.1

7.7

7.4

7.7

8.0

7.7

7.5

7.6

7.7

7.4

8.0

7.3

7.4

Specific 

conductance 

(pmhos)

446

926

158

605

281

420

325

2,630

1,235

555

1,650

628

507

675

5,350

Predominant

Cation

Na

Ca

Ca

Ca

Ca

Ca

Mixed

Mixed

Mixed

Mixed

Na

Mixed

Mixed

Ca

Na

An ion

HC03

HC03

HC03

HC03

HC03

HC03

HC03

S04

Mixed

HC03

Cl

HC03

HC03

HC03

Mixed

primary and secondary drinking-water regulations at 

some sites. Feder and Krothe (1981) noted that both 

selenium and fluoride exceeded the regulations in some 

water samples from the Ogallala Formation.

Excessive fluoride concentrations (greater than 2 mg/ 

L) are a widespread problem in the High Plains 

aquifer. Fluoride concentrations exceed drinking-water 

regulations in parts of Colorado (Boettcher, 1964), Kansas (Hathaway and others, 1977), Nebraska (Engberg 

and Spalding, 1978), New Mexico (Dinwiddie, 1963), 

Oklahoma (Schoff, 1939, 1943), and Texas (Cronin, 

1964; Bassett and others, 1980). Some fluoride in water 

in the High Plains aquifer is derived from the solution 

of fluoride minerals in the sand and gravel that comprises most of the aquifer. However, excessive concentrations (2-8 mg/L) occur where the aquifer contains 

volcanic-ash deposits or where it is underlain by Cretaceous (especially Lower Cretaceous) rocks. Fluoride is 

of concern in drinking water; commonly occurring concentrations of fluoride are not of concern in irrigation 

water.

The chemical composition of water in the High Plains 

aquifer is related to the concentration of dissolved solids. In general, water in the High Plains aquifer containing less than 250 mg/L dissolved solids is calcium 

bicarbonate type water; sodium and sulfate become 

more prevalent as the concentration of dissolved solids 

increases from 250 to 500 mg/L. Water from the aquifer 

containing small concentrations of dissolved solids indicates short residence time and dissolution of calcium 

and magnesium minerals, such as calcite and dolomite. 

Larger concentrations of dissolved solids indicate 

longer residence time, contact with soluble minerals 

such as gypsum, anhydrite, and halite, or mixing with 

more mineralized water from bedrock. The chemical

character of ground water that exceeds 500 mg/L dissolved solids is mixed, with ions calcium, sodium, sulfate, and chloride most prevalent.

Most of the water (85 percent) in the High Plains 

aquifer contains less than 500 mg/L dissolved solids as 

shown in figure 16. About 27 percent of the volume 

of water in the High Plains aquifer contains less than 

250 mg/L dissolved solids and 15 percent of the volume 

of water in the aquifer contains more than 500 mg/L 

dissolved solids. Only 3 percent of the volume of water 

in the aquifer exceeds 1,000 mg/L dissolved solids, most 

of which is in Texas. Generally, the largest concentrations of dissolved solids in water from the High Plains 

aquifer are less than 3,000 mg/L except where water 

has been contaminated by saline water.

Water in the High Plains aquifer in parts of Colorado, Kansas, Nebraska, and Wyoming contains less 

than 250 mg/L dissolved solids (fig. 15). A large part 

of this area in Colorado and Nebraska is covered by 

sandy soils and dune sands. The concentration of dissolved solids in the area covered by sand is less than 250 

mg/L because recharge to the aquifer from precipitation is relatively large and most soluble material already has been removed from the sand.

In many areas shown in figure 15, water in the 

aquifer contains 500 to 1,000 mg/L dissolved solids, and 

in some areas, more than 1,000 mg/L. The water 

chemistry in these areas appears to be related to bedrock geology. Except south of the Canadian River, the 

age of the geologic units underlying the High Plains 

aquifer increases from north to south and from west 

to east (fig. 4). The age of the bedrock ranges from 

Tertiary to Permian and, in general, the older rocks 

contain more soluble minerals than the younger rocks.

The bedrock can affect the chemical composition of
GEOHYDROLOGY OF THE HIGH PLAINS AQUIFER 37

100

<

cc

S 75

3 0 O

|0 50

UJ <

25

250 500 750 1000

DISSOLVED-SOLIDS CONCENTRATION, 

IN MILLIGRAMS PER LITER

FIGURE 16. Percentage volume of water in the High 

Plains aquifer exceeding indicated concentration of dissolved solids.

water in the aquifer in several ways. Water at the base 

of the aquifer in contact with the bedrock can dissolve 

minerals and transport solutes through the aquifer by 

ground-water flow and diffusion. Water containing 

large concentrations of solutes within the bedrock can 

flow from the bedrock into the aquifer in response to 

hydraulic-head differences. Also, dissolution of minerals 

from reworked bedrock material contained in the 

aquifer since deposition can affect water chemistry.

In parts of northeastern Nebraska, the High Plains 

aquifer includes reworked bedrock material of marine 

origin. Wells in these areas do not yield adequate quantities of water for irrigation and the dissolved-solids 

concentration in ground water may exceed 1,000 mg/L 

(fig. 15). The largest concentration of dissolved solids 

reported was 2,120 mg/L.

The concentration of dissolved solids in water from 

the High Plains aquifer exceeds 1,000 mg/L near outcrops of Late Cretaceous age in southeastern Wyoming 

(fig. 15). The bedrock units underlying the aquifer in 

this area are the Upper Cretaceous Lance Formation 

and the Tertiary Chadron and Brule Formations of the 

White River Group. Rapp and others (1957) reported

that the dissolved-solids concentration in water from 

the Lance Formation ranged from 416 to 1,250 mg/L 

and exceeded 1,000 mg/L in 2 of 7 water samples. 

Water in the Lance Formation generally is under artesian pressure (Rapp and others, 1957) and may be moving into the High Plains aquifer.

The concentration of dissolved solids in water from 

the aquifer exceeds 1,000 mg/L north of the Arkansas 

River in Colorado. The largest concentration of dissolved solids reported by Boettcher (1964) in this area was 

2,560 mg/L. The aquifer is underlain by the Smoky Hill 

Marl Member of the Niobrara Formation of Late Cretaceous age. The Smoky Hill Marl Member is "practically 

impermeable" and contains gypsum (calcium sulfate) 

crystals according to Boettcher (1964). Water in the 

aquifer contains sulfate as the dominant anion (table 

9, sample 8), which is attributed to gypsum in the bedrock. Because the Smoky Hill is not known to yield 

water to wells, the chemistry of water in the High 

Plains aquifer probably is affected by solution of gypsum at the bedrock contact or in wells that are drilled 

through the aquifer into bedrock.

In parts of south-central and southwestern Kansas, 

the High Plains aquifer is underlain by Permian age 

bedrock (fig. 4) containing salt beds and saline water. 

In this area, water in the aquifer contains 500 to 1,000 

mg/L dissolved solids (fig. 15). The water type is mixed 

with large proportions of sodium and chloride (table 9, 

sample 9) indicating that water from the Permian bedrock may be entering the aquifer.

Permian bedrock also underlies the High Plains 

aquifer in parts of southwestern Kansas, western Oklahoma, and northern Texas (fig. 4). Water in the 

aquifer in this area typically contains 250 to 500 mg/L 

dissolved solids but concentrations exceed 1,000 mg/L 

near Permian outcrops in Oklahoma (fig. 15). As shown 

in table 9, sample 11, water in the aquifer is a sodium 

chloride type, which indicates that saline water from 

the Permian bedrock is entering the aquifer. The 

largest dissolved-solids concentration noted in water 

from the aquifer in this area was 6,200 mg/L.

In the southern High Plains of New Mexico and 

Texas, the aquifer is underlain by Triassic, Jurassic, 

and Lower Cretaceous bedrock (fig. 4). The Lower Cretaceous rocks were deposited in a deep-water marine 

environment. Water in these rocks is very mineralized 

and probably is moving into the High Plains aquifer 

in response to hydraulic-head differences. As shown in 

figure 15 and table 9 (samples 14 and 15), water in 

the aquifer in the southern High Plains contains excessive concentrations of dissolved solids and unusually 

large proportions of magnesium, sodium, chloride, and 

sulfate. This probably is caused by the movement of 

solutes from the marine bedrock into the aquifer. Also,
38 HIGH PLAINS RASA PROJECT

Reeves and Miller (1978) proposed that seepage from 

saline lakes or playas contributes to the relatively large 

dissolved-solids concentration found in water from the 

aquifer in the southern High Plains of Texas. The 

largest concentration of dissolved solids in water from 

the aquifer noted during this study was 20,200 mg/L 

reported by Rettman and Leggat (1966, p. 169) in 

Gaines County, Texas. This anomalous concentration 

was caused by contamination from disposal of oilfield 

brines in surface pits. Generally, the dissolved-solids 

concentration in water from the High Plains aquifer in 

southern Texas is less than 3,000 mg/L.

The concentration of dissolved solids in water in the 

High Plains aquifer near major streams is affected by 

irrigation practices. Salts that accumulate in the soil 

due to evapotranspiration are dissolved and flushed 

with irrigation water. In stream valleys where the 

water table is near land surface, the salts that were 

dissolved from the soil are transported to the aquifer. 

As shown in figure 15, the concentration of dissolved 

solids in ground water along the Arkansas, Platte, and 

Republican Rivers generally is 500 to 1,000 mg/L and

exceeds 1,000 mg/L along parts of the South Platte and 

Arkansas Rivers.

SODIUM

The areal distribution of sodium concentration in 

water from the High Plains aquifer is shown in figure 

17, which is reproduced here from a larger scale map 

by Krothe and others (1982). Each interval on the map 

shows the range in sodium concentration that predominates in that area. Chemical data from 28 water samples from the High Plains aquifer are presented in table 

10 and located by number in figure 17. The table includes the data needed to evaluate the salinity and sodium hazards associated with the use of water for irrigation discussed later in this report. These 28 chemical 

analyses were selected because they are representative 

of the variations in the concentrations of the cations 

calcium, magnesium, and sodium found in water from 

the High Plains aquifer. The sodium hazard associated 

with the use of water for irrigation is determined by 

the concentrations of these cations.

TABLE 10. Chemical data from selected water samples from the High Plains aquifer

[mg/L, milligrams per liter; meq/L, milliequivalents per liter; (xmho, micromhos per centimeter at 25°Celsius]

Sample Geonumber in logic 

figure 17 unit

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

ARKR

ARKR

ARKR

OGLL

SDGV

BRUL

OGLL

OGLL

OGLL

OGLL

OGLL

OGLL

OGLL

OGLL

OGLL

OGLL

SDGV

OGLL

OGLL

OGLL

OGLL

OGLL

OGLL

OGLL

OGLL

OGLL

OGLL

OGLL

Well 

depth 

(feet)

150

96

100

220

245

150

200

250

153

368

200

227

321

100

340

320

70

180

178

260

230

180

560

120

201

90

95

101

Calcium

(mg/L)

57

28

122

40

20

24

94

45

41

29

56

43

30

228

no

320

91

54

33

63

49

46

54

35

38

108

383

295

(meq/L)

2.84

1.40

6.09

2.00

1.00

1.20

4.69

2.25

2.05

1.45

2.79

2.15

1.50

11.38

5.49

15.97

4.54

2.69

1.65

3.14

2.45

2.30

2.69

1.75

1.90

5.39

19.11

14.72

Magnesium

(mg/L) (meq/L)

2.4

8.3

29

6.7

3.3

11

14

5.5

11

9.7

15

17

10

114

48

62

12

20

20

19

29

14

23

30

16

16

177

297

0.20

.68

2.39

.55

.27

,90

1.15

.45

.90

.80

1.23

1.40

0.82

9.38

3.95

5.10

.99

1.65

1.65

1.56

2.39

1.15

1.89

2.47

1.32

1.32

14.56

24.43

Sodium

 C

(mg/L) (meq/L)

77

52

27

8.0

6.6

59

12

4.4

25

22

9.8

24

22

222

47

120

80

18

28

240

20

100

130

46

47

68

227

1,151

3.35

2.26

1.17

.35

.29

2.57

.52

.19

1.09

.96

.43

1.04

.96

9.66

2.04

5.22

3.48

.78

1.22

10.44

.87

4.35

5.66

2.00

2.04

2.96

9.87

50.07

Specific 

onductance 

(pmhos)

617

446

926

305

158

485

605

281

400

328

420

450

325

2,630

1,060

2,100

875

470

435

1,650

555

855

1,070

612

475

941

2,900

4,250

Sodium 

adsorption 

ratio

2.7

2.2

.6

.3

.4

2.5

.3

.2

.9

.9

.3

1.3

0.9

3.0

.9

1.6

2.1

.5

1.0

6.8

.6

3.6

4.1

1.4

1.6

1.6

2.4

11.3
GEOHYDROLOGY OF THE HIGH PLAINS AQUIFER 39

43°

42°

41° __

40'

39°

103° 102° 101° 100° 99°

c§l COLORADO

EXPLANATION

SODIUM CONCENTRATION, IN

MILLIGRAMS PER LITER 

Less than 25

18 SAMPLE SITE-Number refers to 

table 10

FIGURE 17. Sodium concentration in water from the High Plains aquifer (from Krothe and others, 1982).
40 HIGH PLAINS RASA PROJECT

The sodium concentration in water from the High 

Plains aquifer generally increases from north to south 

and ranges from less than 25 to more than 100 mg/L 

as shown in figure 17. The maximum reported sodium 

concentration in uncontaminated water from the aquifer 

was 1,151 mg/L. The concentration of sodium in most 

of the area of the High Plains aquifer is less than 50 

mg/L because the aquifer is composed mostly of sand 

and gravel deposits that contain few sodium minerals. 

In the northern High Plains, water from the Arikaree 

Formation (table 10, samples 1, 2, and 3) and the Brule 

Formation (table 10, sample 6) generally contain larger 

concentrations of sodium than water from the Ogallala 

Formation (table 10, samples 4 and 7-13) or Quaternary 

sand and gravel deposits (table 10, sample 5). However, 

the concentration of sodium in many parts of the High 

Plains appears to be affected by the bedrock.

In Colorado, sample 14 (table 10) from the High 

Plains aquifer contains 222 mg/L sodium. In this area, 

the aquifer is underlain by the Smoky Hill Marl Member of the Niobrara Formation, which contains marine 

clays. The sodium concentration probably is increased 

by ion exchange on clays at the weathered surface of 

the bedrock or on clays in the aquifer derived from 

reworked bedrock.

In southwestern Kansas, Oklahoma, and northern 

Texas, the sodium concentration in water from the 

aquifer exceeds 100 mg/L in several places (fig. 17). 

The concentration of sodium in samples 20, 22, and 23 

in table 10 ranges from 100 to 240 mg/L. The bedrock 

underlying the aquifer in this area is of Permian age 

and contains salt beds and saline water. Relatively 

large concentrations of sodium and chloride (table 9, 

sample 11) indicate that saline water from the Permian 

rocks may be entering the aquifer.

The sodium concentration also exceeds 100 mg/L in 

parts of the High Plains aquifer in New Mexico and 

Texas, south of the Canadian River (fig. 17). In table 

10, sample 27 from the aquifer contains 227 mg/L sodium and sample 28 contains 1,151 mg/L sodium. Most 

of this area of the aquifer is underlain by Lower Cretaceous rocks (fig. 4) containing mineralized water that 

may be entering the aquifer. Also, many saline lakes 

or playas occur in this area (Reeves and Miller, 1978) 

and seepage from the playas may contribute to the relatively large concentrations of sodium found in water 

from the aquifer. In some areas, large concentrations 

of sodium have been caused by disposal of oilfield 

brines in surface pits (Rettman and Leggat, 1966).

Sodium concentrations in water in the High Plains 

aquifer near major streams are affected by irrigation 

practices. In areas of extensive irrigation, sodium is 

concentrated by evapotranspiration and ion exchange

in the soil. In stream valleys where the water table 

is near land surface, infiltration of irrigation water has 

resulted in relatively large concentrations of sodium. 

As shown in figure 17, the sodium concentration in 

ground water is 50 to 100 mg/L along most of the Platte 

and Republican Rivers in Nebraska, and exceeds 100 

mg/L along part of the Arkansas River in Kansas.

GROUND-WATER DEVELOPMENT

Water from the High Plains aquifer is the principal 

source of supply for irrigated agriculture in the region. 

Rapid development of irrigation in the High Plains in 

recent years has transformed the area into one of the 

major agricultural regions of the United States.

IRRIGATION DEVELOPMENT

Irrigation began in the High Plains along the Arkansas and Platte Rivers in the late 1800's, when surface 

water was diverted through ditches to irrigate crops 

in the stream valleys. Because of the lack of adequate 

streamflow during dry years, ditch irrigation was unreliable until storage reservoirs were constructed decades 

later.

Ground-water irrigation in the High Plains also 

began in the late 1800's with the use of windmills. However, ground-water development was sporadic until the 

drought of the 1930's. Spurred by the drought, technological advances in well drilling and pumping plants, 

inexpensive energy, profitable crop prices, and available financing, ground-water irrigation developed rapidly after the 1930's.

The density of acreage irrigated by ground water in 

the High Plains during 1949, 1964, and 1978 is shown 

in figures 18, 19, and 20. These density maps were prepared from data published in the Census of Agriculture 

(U.S. Department of Commerce, 1949, 1964, 1978). 

During 1949 (fig. 18), most of the acreage irrigated by 

ground water was in Texas, New Mexico, southwestern 

Kansas, and along the Platte River in Nebraska. Prior 

to 1949, depth to water in the aquifer and land-surface 

slope were major factors controlling the distribution of 

irrigation development.

During the 1950's, irrigation development was spurred again by severe drought. In addition, development 

of natural-gas fields underlying the High Plains made 

inexpensive energy available, and irrigation development spread throughout large parts of the High Plains. 

Prior to the 1960's, most irrigation wells were drilled 

in areas where the water table was less than 100 feet 

below land surface. Since the early 1960's, development 

of efficient powerplants for turbine pumps has allowed 

areas with deeper water to be developed (Jenkins and
106° 105o

GEOHYDROLOGY OF THE HIGH PLAINS AQUIFER

103° 102° 101° 100° 99° 9B°

41

43°

42°

40°

36°

DENSITY OF IRRIGATED

ACREAGE, IN PERCENT 

0-5

FIGURE 18. Density of acreage irrigated by ground water in the High Plains, 1949.
42 HIGH PLAINS RASA PROJECT

104° 103° 102° 101° 100° 99°

42°

EXPLANATION

DENSITY OF IRRIGATED

ACREAGE, IN PERCENT 

0-5

FIGURE 19. Density of acreage irrigated by ground water in the High Plains, 1964.
GEOHYDROLOGY OF THE HIGH PLAINS AQUIFER 43

42°

41° |__

EXPLANATION

DENSITY OF IRRIGATED

ACREAGE, IN PERCENT 

0-5

FIGURE 20. Density of acreage irrigated by ground water in the High Plains, 1978.
44 HIGH PLAINS RASA PROJECT

Pabst, 1975). Comparison of figures 18 and 19 shows 

the increase and northern migration of irrigation in the 

High Plains, especially in northern Texas, Oklahoma, 

western Kansas, and parts of Nebraska.

The development of center-pivot irrigation systems 

during the 1960's, which were adapted to sandy soils 

and rolling terrain, made land available for irrigation 

that previously was not suitable. The increase in irrigated acreage in the northern parts of the High Plains 

(fig. 20) was mainly the result of center-pivot development. During 1978, an estimated 2,190,000 acres of 

cropland were irrigated by center-pivot systems in 

Nebraska (Bittinger and Green, 1980); this was nearly 

50 percent of the total acreage irrigated by ground 

water in Nebraska.

The growth of irrigated cropland in the High Plains 

based on Census of Agriculture data from 1949-78 is 

shown in figure 21. In the Texas High Plains, the graph 

shows rapid increase of irrigated acreage until 1959 followed by a decrease in the growth rate in recent years. 

The decrease is primarily the result of declining water 

availability in many areas of the Texas High Plains 

(Luckey and others, 1981). In contrast to Texas, the 

graph for the Nebraska High Plains shows a slow rate 

of increase in early years and a rapid increase in irri24

22

20

18

16 

O 

w

z

O 14

12

O 6

DC 

DC

[__I Colorado, New Mexico, 

Oklahoma, South 

Dakota, and Wyoming 

combined

\ | Kansas

|^| Nebraska 

| [ Texas

1949 1954 1959 1964 1969 1974 1978

FIGURE 21. Acreage irrigated by ground water in the High Plains, 

1949-78.

gated acreage in recent years. The growth of irrigated 

acreage in Nebraska is continuing, primarily because 

of the availability of large quantities of ground water 

underlying the sand-dune areas that are suitable for 

irrigation with center-pivot systems. Although the rate 

of growth has decreased in some parts of the High 

Plains, it has increased in other areas. The total acreage irrigated by ground water in the High Plains increased from slightly more than 2 million acres in 1949 

to about 13 million acres in 1978. This rapid increase 

in irrigated acreage in the High Plains has resulted in 

a corresponding increase in ground-water pumpage and 

water-level decline.

Estimates of ground-water pumpage were made, 

using crop consumptive-use data, climatic data, irrigated acreage, and irrigation efficiency estimates. 

Heimes and Luckey (1982, table 2) estimated historical 

irrigation requirement for the High Plains using normal-year climatic data. Pumpage can be estimated by 

adjusting irrigation requirement for efficiency of the irrigation system; efficiency is the ratio of the water 

pumped to the water required by the crop in addition 

to precipitation (irrigation requirement).

13

12

11

10

u_ 6

O

9 5

[ j Colorado, New Mexico. 

Oklahoma, South 

Dakota, and Wyoming 

combined

\ \ Kansas

P"] Nebraska 

\ \ Texas pT

1949 1954 1959 1964 1969 1974 1978

FIGURE 22. Estimated ground-water pumpage from the High 

Plains aquifer, 1949-78.
GEOHYDROLOGY OF THE HIGH PLAINS AQUIFER 45

Ground-water pumpage in the High Plains, estimated 

by the above procedure for 1949-78, is shown in figure 

22. These pumpage estimates are subject to error because of uncertainty in the data used to compute the 

estimates. The irrigated acreage used in the calculations was obtained from the Census of Agriculture and 

adjusted to reflect ground-water irrigated acreage only. 

Irrigation demand was calculated by using the procedures outlined by the U.S. Department of Agriculture 

(1967), based on long-term average climatic data. An 

average system efficiency of 65 percent was assumed 

for the calculation of pumpage presented in figure 22. 

System efficiency generally ranges from about 40 to 90 

percent and depends on many factors, such as type of 

irrigation system, crop type, soil, and climate.

A dramatic increase in pumpage during the last 30 

years is shown by figure 22. Pumpage from the High 

Plains aquifer for irrigation during 1978 was estimated 

at approximately 23 million acre-ft which is almost 20 

million acre-ft more than the estimated pumpage for 

irrigation during 1949.

EFFECTS OF DEVELOPMENT

Irrigation demand for crops grown in the High Plains 

generally is much larger than recharge from precipitation. As previously discussed, natural recharge from 

precipitation in the High Plains is equivalent to only 

a small fraction of total precipitation. Estimates of natural recharge (table 7) range from 0.024 inch per year 

(0.1 percent of mean annual precipitation i for parts of 

the southern High Plains of Texas to 5 inches per year 

(22 percent of the mean annual precipitation) for the 

sand hills in Holt County, Nebraska. Irrigation demand 

for most crops commonly grown in the High Plains is 

more than 1 foot per year, with the greatest demands 

occurring in the southern part and the least demands 

occurring in the northeastern part. The ratio between 

irrigation demand by crops and natural rate of recharge 

to the aquifer could be as small as 2 for crops requiring 

little water in areas with significant recharge and 100 

or more for crops requiring significant water in areas 

with little recharge. Consequently, pumpage for irrigation in large parts of the High Plains greatly exceeds 

the rate of natural replenishment. Any long-term withdrawal of water from the aquifer that greatly exceeds 

the recharge rate will result in long-term water-level 

declines.

The areal extent of water-level declines from predevelopment to 1980 caused by ground-water pumpage 

is shown in figure 23; this figure was modified from 

one published at a larger scale by Luckey and others 

(1981). Water-level declines have occurred in all States 

except South Dakota, where development, relative to

the other States, is sparse. Areas of decline in excess 

of 100 feet occur in 2,500 mi2 in parts of Kansas, New 

Mexico, Oklahoma, and Texas, with most of the area 

occurring in Texas, south of the Canadian River. Areas 

of decline in excess of 50 feet from predevelopment to 

1980 have occurred in 12,000 mi2 in parts of Colorado 

as well as the States mentioned above. Almost all declines in excess of 50 feet have occurred in the part 

of the High Plains aquifer south of 39° latitude. Water 

levels have declined more than 10 feet in 50,000 mi2 

of the High Plains aquifer. Large areas in figure 23 

show no significant change in water levels ( + 10 to-10 

feet of change); some areas show significant rises. Rises 

in Nebraska are due to recharge from surface-water 

irrigation; rises in the other States are due to either 

land-use changes or recovery from abnormally low 

water levels resulting from the drought of 1933-40.

Water-level changes from predevelopment to 1980 

are summarized in table 11, which shows that the High 

Plains aquifer has had a net depletion caused by pumpage of 166 million acre-ft of water. This is about 5 

percent of the predevelopment volume of drainable 

water stored in the aquifer (table 8). About 70 percent 

of this depletion has occurred in Texas (114 million 

acre-ft); 16 percent of the depletion has occurred in 

Kansas (29 million acre-ft). Nebraska has had significant areas of decline, but the volume of water depleted 

nearly has been balanced by the volume added in areas 

of water-level rise (fig. 23) caused by irrigation with 

water from streams.

The ratio of the volume of drainable water remaining 

to the volume of water depleted by 1980 can be calculated by using tables 8 and 11. Texas, the State with 

greatest depletion, still has 3.4 times as much water 

remaining in the aquifer as has been removed from the 

aquifer. For the High Plains as a whole, about 19 times 

as much water remains as has been removed. However, 

in local areas, the volume of water remaining in the 

aquifer is less than the volume that has been removed. 

Luckey and others (1981) showed that more than 50 

percent of the original saturated thickness has been dewatered in parts of southwestern Kansas and the southern High Plains of New Mexico and Texas.

The areas of greatest water-level decline shown in 

figure 23 occur where irrigation first developed, and 

the volume of water withdrawn from the aquifer since 

predevelopment is greatest. By comparing the irrigated-acreage density maps (figs. 18, 19, and 20) and 

the water-level change map (fig. 23), it is apparent that 

the greatest water-level declines have occurred in those 

parts of Texas, Oklahoma, and Kansas where irrigation 

developed earliest. The 1978 irrigated-acreage density 

map (fig. 20) also shows areas where irrigation was 

started during the last 2 decades. Water-level declines
46 HIGH PLAINS RASA PROJECT

105° 1040 103o 1Q2o 101 o KIQO 990 98°

WYOMING

96°

43°

40°

39°

EXPLANATION

WATER-LEVEL CHANGES, 

IN FEET

Rise more than 10

AQUIFER 

BOUNDARY

10 to -10

-10 to -50

-50 to -100

Decline more than 100

FIGURE 23. Predevelopment to 1980 water-level changes in the High Plains aquifer 

(modified from Luckey and others, 1981).
GEOHYDROLOGY OF THE HIGH PLAINS AQUIFER 47

TABLE 11. Distribution of water-level changes and volume of aquifer dewatered, High Plains aquifer, predevelopment to 1980

[Modified from Luckey and others, 1981]

State

Kansas 

hl A(-v» <~l^ 

An 

High 1

ea of Percentage of 

Plains 

aquifer More than

within

(square

. 14

CO

New Mexico 9-J Oklahoma / 

South Dakota-- 4

Total- - 174

State 50-foot

miles) rise

,900

,500

,650 1 

,450

,350 

,750

,450

,000 

,050

+50

to

+25

-

-

1

_

-

-

area within each water-level

+25

to

+10

-

1

2

3

1

1

+10

to

-10

78

72

90 

62

56 

100

23

99 

70

-10

to

-25

19

11

5 

23

29

34

1 

15

-25

to

-50

3

11

1

11

10

17

7

change

- 50

to

-100

--

4

4

2

18

5

interval

More than

100-foot

decline

-

1

-

-

7

2

Volume of 

aquifer

dewatered

(millions of

acre-feet)

6

29

9

114

166

in these areas are less, because pumpage began later 

and the total volume of water withdrawn is smaller. 

This is most evident in Colorado, northwestern Kansas, 

and Nebraska (compare figs. 19 and 23).

CONSTRAINTS ON DEVELOPMENT

Water-level declines, decreased well yields, and the 

distribution of saturated aquifer material have limited 

development of the ground-water resource in parts of 

the High Plains. However, other factors, including 

physical, chemical, economic, and legal constraints limit 

the areas in which the aquifer has been (and can be) 

developed.

Historically, topography and soils were the principal 

constraints on irrigation development. More recently, 

water-level declines causing decreased well yields and 

larger pumping lifts have made well yields and 

economics important constraints. In the future, it is 

likely that continued water-level declines will cause 

well yields and economics to become more important 

factors.

The physical characterisitics of the aquifer constrain 

further irrigation development in the High Plains by 

limiting the well yield. The exact pumping rate 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.

A generalized map of potential well yields from the 

High Plains aquifer is shown in figure 24. The map is 

based on the 1980 saturated thickness (fig. 9) and hydraulic conductivity (fig. 10) of the aquifer. Potential 

yield was estimated by assuming that drawdown in the 

aquifer was limited to 70 percent of the saturated thickness.

The map shows that wells yielding more than 750 

gal/min generally can be obtained throughout large 

areas of the High Plains; most noticeable of these areas 

are large parts of Nebraska and Wyoming and much 

of the area in southwestern Kansas, Oklahoma, and 

northern Texas. Only wells yielding less than 250 gal/ 

min generally can be obtained near the western edge 

of the aquifer and in large parts of Colorado, northwestern Kansas, New Mexico, and the southern High 

Plains of Texas. Depending on crop water demand and 

area to be irrigated, limited well yields may constrain 

irrigation development in the areas where well yields 

are less than 250 gal/min (fig. 24).

Comparison of the potential-yield map (fig. 24) to the 

1978 irrigated-acreage-density map (fig. 20) shows that 

well yields are not yet a limiting factor in most of the 

area that was irrigated extensively during 1980. However, there are notable areas, particularly in the southern High Plains, where only wells yielding less than 

250 gal/min can now be obtained in highly developed 

areas. Greater yielding wells could be obtained in these 

areas, prior to severe water-level declines.

As well yields decreased, irrigators compensated by 

drilling more wells or irrigating less acreage. For example, the average number of acres irrigated per well 

in Castro, Crosby, Floyd, Hale, Lubbock, Farmer, and 

Swisher Counties, Texas, decreased from 118 in 1958 

to 62 in 1980 (Luckey and others, 1981). This decrease
48 HIGH PLAINS RASA PROJECT

10G° 105° 104° 103° 102° 101° 100° 99°

96°

42o

40°

EXPLANATION

POTENTIAL YIELD OF WELLS, 

IN GALLONS PER MINUTE 

Less than 250

FIGURE 24. Potential well yields from the High Plains aquifer, 1980.
GEOHYDROLOGY OF THE HIGH PLAINS AQUIFER 49

in acres irrigated per well is the result of decreasing 

well yields, caused by declining water levels and decreasing saturated thickness in the aquifer. From 1958 

to 1980, the number of irrigated acres in the seven 

counties decreased from 2.5 million to 1.9 million, and 

the number of wells increased from about 21,000 to 

30,000. Declining well yields and increased pumping 

lifts in these seven counties undoubtedly have caused 

significant increases in farm-operation expenses. Similar impacts can be expected, as ground-water development continues in other areas of the High Plains.

Chemical quality of water in the High Plains aquifer 

may limit irrigation development in some areas. Although many chemical constituents or properties of 

water affect its suitability for irrigation, the two main 

criteria for determining the suitability of water for irrigation are dissolved-solids concentration (salinity hazard) and sodium concentration, relative to calcium and 

magnesium concentrations (sodium hazard).

Salinity hazard is important because mineralized 

water can interfere with the process by which plants 

extract water from the soil. The importance of this hazard is related to irrigation practices and crop type. Two 

crops commonly grown in the High Plains, alfalfa and 

sugar beets, are tolerant to salinity, while some kinds 

of field beans are sensitive to salinity (U.S. Salinity 

Laboratory Staff, 1954). All other crops commonly 

grown on the High Plains are semi-tolerant to salinity.

Specific conductance is a convenient measure of the 

dissolved-solids concentration and salinity hazard of 

water; specific conductance is the electrical conductivity 

of water, measured in micromhos per centimeter at 25° 

Celsius (|xmho). Almost all sources of irrigation water 

that have been used successfully for a considerable time 

have specific conductances of less than 2,250 ixmho. 

Waters with greater specific conductance are used occasionally, but crop production has not been satisfactory, 

except in unusual situations (U.S. Salinity Laboratory 

Staff, 1954).

Excessive concentrations of sodium are harmful to 

plants and soil. Accumulation of sodium in soils affects 

plant growth and decreases soil permeability and tillability. The sodium hazard is most important in finetextured (clayey) soils (fig. 14). The sodium-adsorption 

ratio is a means of determining whether the sodium 

concentration of water is likely to affect soil properties 

adversely. The U.S. Salinity Laboratory Staff (1954) 

defined sodium-adsorption ratio (SAR) of water as:

SAR =

(Na+ )

V;ca 

-

where ion concentrations are expressed in milliequivalents per liter. Experiments cited by the U.S. Salinity 

Laboratory show that the SAR predicts reasonably 

well the degree to which irrigation water tends to enter 

into cation-exchange reactions in soil. Large SAR values indicate a hazard of sodium replacing adsorbed calcium and magnesium; this replacement is damaging to 

soil structure (Hem, 1970).

A diagram for the classification of irrigation waters, 

developed by the U.S. Salinity Laboratory Staff (1954), 

is shown in figure 25; it is based on the specific conductance and SAR. Chemical analyses of 28 ground-water 

samples from the High Plains aquifer were presented 

in table 10; locations of the wells from which these samples were collected are shown in figure 17. The specific 

conductance and SAR from these samples (table 10) are 

plotted and identified by number in figure 25.

The diagram for classification of irrigation waters 

(fig. 25) shows that 17 of the 28 samples had low- or 

medium-salinity hazard, and all samples but 2 had lowsodium hazard. Most of the water in the High Plains 

aquifer has medium-salinity hazard and low-sodium hazard. This type of water can be used for irrigation, if 

some leaching occurs. Plants with moderate salt tolerances (which include most crops grown in the High 

Plains) can be grown in most instances without special 

practices for salinity control; there is little danger of 

the development of harmful levels of exchangeable sodium.

In a few areas in the High Plains, salinity or sodium 

hazard could limit further agricultural development. 

Areas of high- or very high salinity hazard occur in Colorado (sample 14), Kansas (samples 15, 16, 17, and 20), 

New Mexico (sample 26), Oklahoma (sample 22), Texas 

(samples 23, 27, and 28), and Wyoming (sample 3). In 

the vicinity of these samples (fig. 17), water from the 

High Plains aquifer may not be suitable for irrigation 

on soils with poor drainage without management for 

salinity control. In other areas where the concentration 

of dissolved solids exceeds 1,000 mg/L (fig. 15), salinity 

could limit the use of water from the aquifer for irrigation, depending on the type of crops grown, soil type, 

and management practices. Also, alkaline soils could 

develop from the use of ground water for irrigation in 

areas where the concentration of sodium exceeds 100 

mg/L (fig. 17), depending on soil type, calcium and 

magnesium concentrations in ground water, and management practices.

Agricultural economics also could be a limiting factor 

to further irrigation development in the High Plains. 

Most economic factors, such as crop prices, and energy, 

land, fertilizer, labor, and equipment costs, are independent of water resources, but the cost of pumping 

water is related to the depth from which water is
50 HIGH PLAINS RASA PROJECT

100 200 I 500

 i i m

1000 2000 r 5000

30

28

26

24

22

_ 20 

a:

9. 18

16

en 14

Q

<

2 12 Q 

O 

cn

10

5«

2 6. 1. 

10 19 12\25 24

N. Q'NS'^ 91

J.P4 11|» 18i * P 71

20*

17. 

26* 

3. - 15

16*

28*

100 250 750 2250

SPECIFIC CONDUCTANCE, IN MICROMHOS 

PER CENTIMETERS AT 25° CELSIUS

1

LOW

2

MEDIUM

3

HIGH

4

VERY HIGH

SALINITY HAZARD

FIGURE 25. Classification of salinity and sodium hazards for irrigation water (from Krothe and

others, 1982).

pumped. The limiting depth from which it is no longer 

economically feasible to lift irrigation water is not a 

fixed quantity; it changes as the prices of energy and 

crops change.

In 1979, energy costs to pump 1 acre-ft of water with 

100 feet of lift were $9.95 for electricity and $6.00 for

natural gas (Sloggett, 1981). Based on 1990 projected 

energy prices (Sloggett, 1981, p. 19), the above costs 

will double for electricity and increase 6-fold for natural 

gas. Considering that water levels in the High Plains 

aquifer are declining (increasing pumping lift), and that 

energy costs are proportional to lift (doubling lift dou-
GEOHYDROLOGY OF THE HIGH PLAINS AQUIFER 51

bles cost), depth to water may become an important 

constraint to future agricultural economics and development.

A generalized map of depth to water in the High 

Plains aquifer is shown in figure 26. This map was prepared by subtracting the 1980 altitude of the table in 

the aquifer (fig. 8) from the average altitude of land 

surface from U.S. Geological Survey topographic maps 

at approximately 1,800 points and contouring the results. The map is very general and represents only typical depth to water for large areas. In topographically 

low areas, such as stream valleys or inter-dune areas, 

depth to water could be considerably less than that 

shown on the map; in topographically high areas, such 

as on hills or tops of dunes, depth to water could be 

considerably greater than that shown on the map. In 

areas of little or no saturated thickness, the indicated 

depth to water may be in the bedrock.

The depth-to-water map (fig. 26) shows large areas 

in Nebraska, Kansas, New Mexico, and Texas, where 

the depth to water is less than 50 feet. The depth to 

water is greater than 300 feet in parts of Kansas, New 

Mexico, and Texas. If all other factors were equal, 

pumping costs would be 6 times greater where the 

depth to water is 300 feet than where it is 50 feet. 

Thus, depending on future energy costs, pumping lifts 

may constrain agricultural development in those areas 

of the High Plains where the depth to water is greatest.

In the High Plains, State laws regulate development 

of ground-water resources as summarized in table 12. 

Each of the eight States has developed its own body 

of law, and these laws vary from State to State. Oklahoma and Texas are the only two States that recognize private ownership of ground water; in the other 

six States, water is dedicated to the people of the 

State. In New Mexico and South Dakota, State agencies administer the water. In the other six States, administration is shared to a greater or lesser extent between State and local agencies. This results in varying 

rules within a State. In all States, a well registration 

or permitting system exists; and, in several States, 

there is a limit on the minimum spacing between wells. 

Other regulations vary between States and may vary 

within each State. A more detailed discussion is given 

by Sloggett (1977).

The Colorado Groundwater Commission, directed by 

the State Engineer, manages ground water in Colorado. The Commission has the authority to designate 

ground-water basins and approve local ground-water 

management district boundaries and rules within 

ground-water basins. In the High Plains, two groundwater basins have been designated, the Northern High

Plains and the Southern High Plains (fig. 27). There 

are eight operational ground-water management districts in the Northern High Plains basin. Well permits 

are required Statewide; further restrictions apply in 

designated ground-water basins (table 12). Groundwater management districts may adopt rules that are 

more restrictive than Groundwater Commission policy. 

These districts may determine well spacing requirements, establish depletion rates, limit pumping, require 

metering, and develop water-conservation measures.

Ground water in Kansas is administered by the Chief 

Engineer, Division of Water Resources, State Board 

of Agriculture. Five ground-water management districts have been formed in the High Plains (fig. 27). 

District management programs are approved by the 

Chief Engineer. Well permits are required Statewide 

to establish water rights. Management districts have 

the authority to adopt and enforce ground-water management policies within existing State laws. Regulations vary among the districts, but restrictions on well 

spacing, drilling, allocation of water, and wastage have 

been adopted (table 12). Management policies vary 

from allowing no depletion of the aquifer to allowing 

controlled depletion.

In Nebraska, ground water is administered by the 

Department of Water Resources, ground-water conservation districts, and natural resource districts. Six 

ground-water conservation districts were formed prior 

to 1972, when 24 natural resource districts were established to cover the State. The conservation and natural 

resource districts share the responsibility and function 

of ground-water management, where both districts 

exist. Registration of wells, minimum spacing of 600 

feet for irrigation wells and 1,000 feet for municipal 

and industrial wells, and runoff control are required 

Statewide (table 12). Control areas can be proposed by 

natural resource districts and approved by the Division 

of Water Resources. Control areas are managed by the 

local natural resource district. In control areas, permits 

to drill wells are required, and regulations may be established to restrict well spacing, limit allocations, and 

restrict well drilling. As of 1982, three control areas 

had been established (fig. 27) in the Upper Republican, 

Upper Big Blue, and Little Blue Natural Resource Districts. Beginning in 1982, natural resource districts 

have the authority to establish managment areas, 

where well spacing and water allocation may be restricted without approval from the Division of Water 

Resources.

The State Engineer administers ground water in 

New Mexico, but only within declared ground-water 

basins. Ground water outside declared basins is not 

subject to regulation. Two ground-water basins have
52 HIGH PLAINS RASA PROJECT

106° 105° 104°

42° \-

40°

390 L c$ COLORADO

EXPLANATION

DEPTH TO WATER, IN FEET 

0-50

50-100 

100-200 

200-300 

300-400

AQUIFER 

BOUNDARY-4::H;..

AREA OF LITTLE OR NO

SATURATED THICKNESS

FIGURE 26. Generalized depth to water in the High Plains aquifer, 1980.
GEOHYDROLOGY OF THE HIGH PLAINS AQUIFER 53

970 96°

43°

42°

40°

38°

105° 104° 103" 102" ini

39° ,L c§f COLORADO

AQUIFER 

BOUNDARY EXPLANATION

GROUND-WATER MANAGEMENT

AREAS 

Control area

Management district and number 

Ground-water basin

0 50 100 MILES

I

37"

FIGURE 27. Ground-water management areas in the High Plains.
54 HIGH PLAINS RASA PROJECT

TABLE 12. Summary of regulations controlling ground-water

Control of ground water

State Ownership

Administering

State

agencies

Local

Well 

permits

Flow 

metering

Regulations

Minimum well 

spacing 

(feet)

Colorado State Groundwater

Commission,

State

Engineer.

Groundwater

Management

Districts.

Required

statewide.

Can be

required.

2,640 in

ground-water

basins.

Kansas-- State

Nebraska State

New State 

Mexico.

State Board of 

Agriculture, 

Div. of Water 

Resources.

Department 

of Water 

Resources.

State 

Engineer.

Groundwater 

Management 

Districts.

Groundwater 

Conservation and 

Natural 

Resources 

Districts.

None

Required Can be 

required.

Registra- In some 

tion re- areas, 

quired.

Required In some 

areas.

1,320 to 2,640 

depending on 

area and well 

yield.

600 to 1,000 

in control 

areas.

None

Oklahoma Land- Water None, but

owner. Resources can be

Board. organized.

Required None, None, but 

but can can be 

be re- required, 

quired.

South State Dept. of Water None 

Dakota. and Natural 

Resources.

Required None None

Texas--- Land- Dept. of Water Groundwater Required None 

owner. Resources. Management

Districts.

Wyoming- State Board of Control , State 

Engineer.

Advisory 

board.

Required None 

statewide.

600 to 1,200 

depending on 

well size 

and yield.

None

been declared in the High Plains of New Mexico (fig. 

27) part of Lea County since 1931 and the Portales 

Valley in Roosevelt County since 1950. Within the declared basins, the State Engineer restricts drilling and 

limits allocation of water based on planned depletion 

of the ground-water supply in 40 years, beginning in 

1952 for Lea County and 1956 for Portales Valley. 

Water-use permits, when authorized, are limited to 3 

acre-ft per acre per year (table 12).

Ground water in Oklahoma belongs to the landowner 

but is administered by the Water Resources Board. Oklahoma ground-water law provides for the formation of

ground-water management districts, but none have 

been formed as of 1982. The Water Resources Board 

has the authority to regulate the allocation of ground 

water, require metering of wells if the majority of the 

landowners concur, and specify minimum well spacing. 

As of 1982, only allocations have been regulated by the 

Board. Allocations are based on planned depletion of 

the aquifer no sooner than 1993 (table 12). When applications for new wells would cause depletion before 

1993, no new water-use permits will be allowed.

Ground water in South Dakota is administered by 

the Department of Water and Natural Resources.
GEOHYDROLOGY OF THE HIGH PLAINS AQUIFER 

development from the High Plains aquifer, by State

affecting ground-water development

55

Drilling 

restrictions

In areas of 

planned rate 

of depletion.

Restricted in 

some areas.

Limited 

allocation 

(acre-feet per 

acre per year)

2.5 in N. High 

Plains, 3.5 in 

S. High Plains.

1.5 to 2.0 

depending on 

location.

Planned rate 

of depletion

40 percent in 

25 years in N. 

High Plains, 

none in S. 

High Plains.

Varies by 

management 

district.

Conservation 

measures

Can be 

required.

Required

Remarks

Most regulations 

only apply to 

designated 

ground-water 

basins.

Rules vary by 

management 

district.

Permit required in 

control 

areas.

Varies by None 

control area.

Statewide 

irrigationrunoff 

control .

Rules vary by 

conservation 

and natural 

resources 

district.

Restricted 

in declared 

ground-water 

basins.

None

None

3.0

Temporary permits for 2, 

permanent 

permits based 

on supply.

2 maximum

Not sooner 

than 40 years 

starting in 

1952 or 1956.

Not sooner 

than 1993.

Waste is not 

allowed.

Waste is not 

allowed.

Regulations 

only apply to 

declared groundwater basins.

Regulation began 

in 1973, only 

well permits and 

allocations controlled in 1982.

Allocation limited to rate 

of recharge; 

depletion not 

al lowed.

Waste is not 

allowed.

Regulations do 

not apply to 

Indian reservations.

Restricted

in certain

areas.

Permit

required.

None, but can None

be limited.

Restricted None

in control

areas.

Waste is not

allowed.

Waste is not

allowed.

Rules only apply

in management

districts.

Restrictions

apply to control areas.

There are no ground-water management districts in 

South Dakota. Permits are required for irrigation wells 

and allocations are limited to the recharge rate, as determined by the Department, in the area to be irrigated. Depletion of ground water is not allowed, and 

annual allocations cannot exceed 2 acre-ft per acre irrigated (table 12). There are no specific restrictions on 

well spacing or drilling, and metering is not required. 

However, if problems related to ground-water development occur in an area, the Department has the authority to declare a critical water-control area and restrict 

further development. As of 1982, there were no control

areas in South Dakota. The regulations do not apply 

to Indian reservations.

In Texas, ground water is owned and controlled by 

the landowner. The Texas Department of Water Resources is the principal State agency with water-resource planning functions. However, Department 

ground-water activities are limited to fact finding, data 

collection, and analysis of ground-water supplies. The 

Department has no control over well drilling or allocation of ground water. Ground-water management is the 

option of the people, who can establish ground-water 

management districts by vote under the local-option
56 HIGH PLAINS RASA PROJECT

ground-water control law of 1949. As of 1982, three 

ground-water management districts have been formed 

in the High Plains of Texas (fig. 27). These three districts have the authority to require permits, limit well 

spacing, restrict allocations, and prohibit waste. As of 

1982, the districts have exercised all their authority except limiting water-use allocations (table 12). There are 

no restrictions on irrigation wells outside the management districts.

Ground water in Wyoming is administered by the 

State Engineer and the State Board of Control. A permit must be obtained from the State Engineer before 

a well can be drilled in Wyoming. The permit usually 

is granted, except in control areas. In areas of groundwater supply or use problems, the State Engineer may 

recommend to the State Board of Control that a control 

area be established. Upon approval of the Board, a control area advisory board is elected from the local 

people. With the advice of the advisory board, the 

State Engineer establishes the regulations necessary to 

alleviate the ground-water problem (table 12). As of 

1982, there were three control areas in the High Plains 

of Wyoming in Laramie, Goshen, and Platte Counties 

(fig. 27). Within control areas, applications to drill wells 

and use ground water (for other than stock or domestic 

wells under 25 gal/min) must be approved by the advisory board. If the board approves, the application is advertised for public comment. If there are public protests, a hearing is held, before the State Engineer decides on the application.

Management of ground water, as well as other resources, is necessary to obtain the greatest benefit for 

the most people in the High Plains. This can be obtained only through orderly development. The regulations summarized in table 11 attempt to control development and manage the resource within the policies 

and legal structure of each State. Future development 

of the High Plains aquifer will be controlled by the laws 

of each State.

SUMMARY AND CONCLUSIONS

The High Plains aquifer underlies about 174,000 mi2 

in parts of eight States Colorado, Kansas, Nebraska, 

New Mexico, Oklahoma, South Dakota, Texas, and 

Wyoming. The aquifer is the principal source of water 

in one of the Nation's major agricultural areas. About 

170,000 wells pump water from the aquifer to irrigate 

about 13 million acres in the High Plains.

The High Plains aquifer consists of hydraulically connected geologic units of late Tertiary or Quaternary 

age. The upper Tertiary rocks include part of the Brule 

Formation, Arikaree Group, and Ogallala Formation.

The Quaternary rocks consist of alluvial, dune-sand, 

and valley-fill deposits.

The Brule Formation is predominately a massive siltstone with little permeability. In areas where the permeability of the formation has been increased by joints 

or fractures, the Brule is included in the High Plains 

aquifer. Where joints and fractures have not enhanced 

the permeability of the unit, the top of the Brule Formation is considered the base of the aquifer. The Brule 

Formation is included in the aquifer in parts of Colorado, Nebraska, and Wyoming.

The Arikaree Group (or Formation) includes all 

upper Tertiary rocks between the underlying Brule 

Formation and the overlying Ogallala Formation. The 

Arikaree crops out in, or underlies parts of, western 

Nebraska, southwestern South Dakota, southeastern 

Wyoming, and northeastern Colorado. The Arikaree is 

predominantly a massive sandstone, with thickness as 

much as 1,000 feet in Wyoming and western Nebraska.

The Ogallala Formation, which underlies 134,000 mi2, 

is the principal geologic unit in the High Plains aquifer. 

The Ogallala consists of a heterogeneous sequence of 

clays, silts, sands, and gravels, deposited by streams 

that flowed eastward from the mountains. Within the 

Ogallala, zones cemented with calcium carbonate are 

resistant to weathering and form escarpments that typically mark the boundary of the High Plains.

Unconsolidated alluvial deposits of Quaternary age in 

hydraulic connection with Tertiary deposits are part of 

the High Plains aquifer. Much of the gravel, sand, silt, 

and clay in the alluvial deposits are reworked from the 

Ogallala Formation. Alluvial deposits comprise the 

High Plains aquifer in south-central Nebraska and the 

Great Bend area in central Kansas. In many parts of 

the High Plains, Quaternary alluvial deposits directly 

overlie the Ogallala Formation to form one aquifer.

Dune-sand deposits of Quaternary age, consisting 

predominantly of very fine to medium wind-blown sand, 

are part of the High Plains aquifer. The most extensive 

area of dune sand is in west-central Nebraska, where 

the deposits cover an area of about 20,000 mi2. Large* 

areas also are covered by dune-sand deposits south of 

the Arkansas River in Kansas. In south-central Kansas, 

dune sand is saturated in many places and forms part 

of the aquifer system. In southwestern Kansas, the 

water table generally lies below the dune-sand deposits 

which are recharge areas for the underlying alluvial deposits and Ogallala Formation. Recharge areas also 

occur in other parts of the study area where dune sand 

overlies the High Plains aquifer.

Valley-fill deposits consist of unconsolidated gravel, 

sand, silt, and clay, associated with the most recent 

cycle of erosion and deposition along present streams.
GEOHYDROLOGY OF THE HIGH PLAINS AQUIFER 57

Valley-fill deposits that are hydraulically connected to 

underlying Tertiary or Quaternary deposits are part of 

the High Plains aquifer. The valley-fill deposits and associated streams form stream-aquifer systems that link 

the High Plains aquifer to surface streams, particularly 

along the Platte and Arkansas Rivers.

The bedrock in contact with the High Plains aquifer 

ranges in age from Permian to Tertiary. Geologic units 

comprising the High Plains aquifer primarily were deposited on an erosional surface cut into the bedrock 

units.

Permian rocks underlie 12 percent of the High Plains 

aquifer in Kansas, Oklahoma, and Texas. Dissolution 

of Permian evaporites by ground water has resulted 

in faulting of the overlying deposits. Bear Creek fault 

in Kansas and Colorado and Crooked Creek fault in 

Kansas and Oklahoma are the result of salt dissolution. 

In many areas, collapse structures in the Permian rocks 

are filled by younger material that is part of the High 

Plains aquifer.

Rocks of Triassic and Jurassic age directly underlie 

16 percent of the High Plains aquifer in Colorado, Kansas, New Mexico, Oklahoma, and Texas. Some sandstones of Triassic and Jurassic age have adequate permeability to yield large enough quantities of water for 

irrigation. Between the Arkansas and Canadian Rivers 

in parts of Colorado, Kansas, Oklahoma, New Mexico, 

and Texas, many irrigation wells withdraw water from 

both the High Plains aquifer and Triassic and Jurassic 

sandstones.

Lower Cretaceous rocks directly underlie 12 percent 

of the High Plains aquifer in parts of Colorado, Kansas, 

Nebraska, New Mexico, Oklahoma, and Texas. Where 

Lower Cretaceous sandstone beds are in contact with 

overlying younger deposits in the High Plains aquifer, 

hydraulic connection occurs between the two units. 

These sandstones typically have little permeability and 

storage relative to the High Plains aquifer.

Upper Cretaceous rocks directly underlie 32 percent 

of the High Plains aquifer in large areas in Colorado, 

Kansas, and Nebraska and small areas in New Mexico, 

South Dakota, and Wyoming. Except for the Niobrara 

Chalk, Upper Cretaceous rocks generally do yield significant quantities of water to wells.

Oligocene rocks directly underlie 28 percent of the 

High Plains aquifer in Colorado, Nebraska, South 

Dakota, and Wyoming. The White River Group of Oligocene age is the oldest Tertiary deposit present under 

the High Plains. The Chadron and Brule Formations 

comprise the White River Group. The Chadron Formation is the lower unit and mainly consists of consolidated beds of clay and silt. The Brule Formation is 

predominately a massive siltstone. The sediments comprising the Brule Formation were deposited in a large 

basin that contained freshwater lakes, mud flats, and 

braided streams. The upper part of the Brule Formation is part of the High Plains aquifer in areas where 

it contains secondary permeability resulting from interconnected fractures.

Faulting and salt dissolution have affected the bedrock surface and thickness of the High Plains aquifer. 

Along the Wheatland fault in Wyoming, the bedrock 

has been displaced as much as 1,000 feet, and much 

of the Tertiary-fill material on the downthrown side is 

part of the High Plains aquifer. In South Dakota, the 

White Clay fault has caused about 500 feet of displacement in the bedrock.

Faulting and collapse structures associated with salt 

dissolution in Permian bedrock occur from the Arkansas River drainage in Colorado and Kansas to the Colorado River drainage in Texas. Permian salt deposits 

are being dissolved by circulating water that flows from 

the bedrock through the High Plains aquifer or bedrock 

units to discharge to streams. Water from the bedrock 

units affects the quality of water in the aquifer and 

in streams draining the High Plains in Kansas, Oklahoma, and Texas.

Regionally, the High Plains aquifer is a water-table 

aquifer consisting mainly of near-surface sand and 

gravel deposits. Saturated thickness of the aquifer 

ranges from zero (mainly near the western edge) to 

about 1,000 feet in west-central Nebraska and a small 

area in Wyoming. Saturated thickness of the aquifer 

averages 200 feet, and the total volume of saturated 

aquifer material is 21.8 billion acre-ft.

Sediments comprising the aquifer control the hydraulic conductivity and specific yield of the aquifer. Because the distribution of sediment types varies both 

horizontally and vertically, hydraulic conductivity and 

specific yield also are variable. Based on an analysis 

of the vertical variation in sediment types, it was concluded that the vertical distribution of sediments is random. Therefore, for purposes of simulating regional 

ground-water flow, the aquifer system can be represented as two-dimensional, and average values of hydraulic conductivity and specific yield can be used. Hydraulic conductivity ranges from less than 25 to 300 

ft/d and averages 60 ft/d. Specific yield ranges from 

less than 5 to 30 percentand averages about 15 percent. 

A complex area! distribution of aquifer parameters results from the complex fluvial depositional history of 

the aquifer.

Ground water generally flows from west to east in 

the High Plains aquifer, at an average rate of about 

1 ft/d; it discharges naturally to streams and springs. 

Ground water is the major component of streamflow
58 HIGH PLAINS RASA PROJECT

for the Platte River drainage in Nebraska. Natural discharge of ground water by evapotranspiration also occurs where the water table is near land surface, especially in the sand hills of Nebraska.

Precipitation is the principal source of recharge to 

the High Plains aquifer. Because potential evapotranspiration greatly exceeds precipitation, recharge to the 

aquifer generally is small. Estimated recharge rates 

range from 0.024 inch per year in Texas to 6 inches 

per year in south-central Kansas. Typically, recharge 

estimates are greatest in areas with sandy soils. Watertable altitude data indicate that sand-dune areas are 

important recharge areas. The long-term average annual recharge rate is probably a few tenths of an inch, 

except in sand-dune areas.

The High Plains aquifer contained about 3.25 billion 

acre-ft of drainable water in 1980. About 66 percent 

of the water in storage is in Nebraska, and about 12 

percent is in Texas. New Mexico, the State with the 

smallest water resource in the High Plains, has only 

1.5 percent of the volume of drainable water in storage.

The quality of water in the High Plains aquifer generally is suitable for irrigation use; however, the water 

does not meet U.S. Environmental Protection Agency 

drinking water regulations in many places. The concentrations of dissolved solids, fluoride, chloride, and sulfate exceed drinking-water regulations in parts of the 

aquifer in all States.

In general, ground water in the High Plains aquifer 

containing less than 250 mg/L dissolved solids is calcium bicarbonate type water; sodium and sulfate are 

more prevalent at concentrations of 500 mg/L. Ground 

water exceeding 500 mg/L dissolved solids generally is 

a mixed type, with calcium, sodium, sulfate, and 

chloride most prevalent. About 62 percent of the area 

of the High Plains aquifer contains water with 250 to 

500 mg/L dissolved solids; only about 3 percent of the 

area of the aquifer contains water exceeding 1,000 nig/ 

L dissolved solids, most of which is in Texas. Generally, dissolved-solids concentrations are least in areas 

covered by sand, because recharge is relatively high 

and the sand contains few readily soluble minerals.

Bedrock underlying the aquifer affects the chemical 

composition of water in the aquifer in parts of all States 

in the High Plains. Water at the base of the aquifer 

in contact with the bedrock can dissolve minerals and 

transport solutes through the aquifer by ground-water 

flow and diffusion. Water containing excessive concentrations of solutes within the bedrock can flow from 

the bedrock into the aquifer in response to hydraulichead differences. Also, dissolution of minerals from reworked bedrock material contained in the aquifer since 

deposition can affect water chemistry. In most areas 

of the High Plains aquifer, where concentration of dissolved solids exceeds 1,000 mg/L, chemical composition 

of the water is affected by underlying bedrock.

Concentration of dissolved solids exceeds 500 mg/L 

along the Arkansas, Platte, and Republican Rivers because of irrigation practices. Salts that accumulate in 

the soil from evapotranspiration are flushed with irrigation water and carried to the aquifer in the stream valleys where the water table is near land surface.

Sodium concentrations in water from the aquifer generally are less than 100 mg/L. About 56 percent of the 

area of the aquifer contains water with less than 25 

mg/L sodium; only 3 percent of the area contains water 

exceeding 100 mg/L sodium, most of which is in Texas. 

Concentration of sodium varies in response to the same 

factors that affect the concentration of dissolved solids. 

In parts of the southern High Plains of Texas, anomalously large concentrations of dissolved solids and sodium caused by surface disposal of oilfield brines have 

been reported.

About 95 percent of all water pumped from the High 

Plains aquifer is used for irrigation. Ground-water irrigation began during the late 1800's and developed rapidly after the drought of the 1930's. Development of 

the center-pivot system allowed areas to be irrigated 

during the 1960's that previously were not suitable because of sandy soils and rolling terrain. By 1978, the 

reported number of acres irrigated in the High Plains 

was 13 million, and about 170,000 wells pumped an estimated 23 million acre-ft of water for irrigation.

Annual pumpage is from 2 to 100 times greater than 

recharge in parts of the High Plains. Consequently, 

water in the aquifer is removed considerably faster 

than it is replenished. Water levels have declined more 

than 100 feet from predevelopment to 1980 in parts of 

Kansas, New Mexico, Oklahoma, and Texas, including 

2 percent (2,500 mi2) of the area of the aquifer. Water 

levels have declined more than 50 feet in 7 percent 

(12,000 mi2) and more than 10 feet in 29 percent (50,000 

mi2) of the area of the aquifer.

Volume of water in storage in the aquifer has decreased 166 million acre-ft since ground-water development began. About 16 percent of the depletion has occurred in Kansas; about 70 percent of the depletion has 

occurred in Texas.

Water-level declines increase pumping lift, decrease 

well yields, and limit development of the ground-water 

resource. In addition, physical, chemical, economic, and 

legal constraints control where the aquifer has been (or 

can be) developed.

Well yields, which are controlled by the physical 

characteristics of the aquifer, limit development to 

those areas where adequate yields can be obtained. 

Well yields greater than 750 gal/min generally can be 

obtained throughout large areas in all States in the
GEOHYDROLOGY OF THE HIGH PLAINS AQUIFER 59

High Plains. Only wells yielding less than 250 gal/min 

can be obtained where the saturated thickness is thin 

near the edge of the aquifer, or where water-level declines have greatly decreased the saturated thickness.

Chemical quality of water in the aquifer may limit 

irrigation development in some areas. Areas of high-salinity hazard occur in Colorado, Kansas, Oklahoma, 

New Mexico, Texas, and Wyoming. In these areas, 

water from the High Plains aquifer may not be suitable 

for irrigation on soils with poor drainage.

Depth to water below land surface affects the cost 

of pumping water for irrigation. In 1979, the estimated 

cost of pumping 1 acre-ft of water with 100 feet of lift 

was about $10.00 for electricity and $6.00 for natural 

gas. These costs are expected to double for electricity 

and increase 6-fold for natural gas by 1990. Thus, declining water levels and increasing energy costs may 

have a serious impact on the economics of fiiture irrigation development. Depth to water in the High Plains 

aquifer already is greater than 300 feet in parts of Kansas, New Mexico, and Texas.

Legal restraints also control development of ground 

water. Regulations controlling ground-water development vary between States and within some States. In 

Texas, ground water is owned and controlled by the 

landowner. In Oklahoma, ground water is owned by 

the landowner, but development is controlled by the 

State. In the other six States, the water is dedicated 

to the people of the State and administered by the 

State and local management districts. Future development of the High Plains aquifer will be controlled by 

the laws of the States in the High Plains.

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* U.S. GOVERNMENT PRINTING OFFICE: 1984 576-595