Ground-Water Resources Program

Water-Use Trends in the Desert 

Southwest—1950–2000

By A.D. Konieczki and J.A. Heilman

Scientific Investigations Report 2004–5148

U.S. Department of the Interior

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

Gale A. Norton, Secretary

U.S. Geological Survey

Charles G. Groat, Director

For more information about the USGS and its products:

Telephone: 1-888-ASK-USGS

World Wide Web: http://www.usgs.gov/

Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply 

endorsement by the U.S. Government.

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

reproduce any copyrighted materials contained within this report.

Suggested citation:

Konieczki, A.D., and Heilman, J.A., 2004, Water-use trends in the desert Southwest—1950–2000: U.S. Geological 

Survey Scientific Investigations Report 2004–5148, 32 p.
iii

Contents

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

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

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

Previous investigations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Regional setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Water resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Surface-water resources. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Ground-water management. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Data availability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Water-use trends, 1950 to 2000. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Total water withdrawal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Domestic water use and population growth. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Agricultural water use and irrigated acreage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Industrial water use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

Summary and conclusions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

Selected references . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
iv

Figures

1–3. Maps showing:

Figure 1. States, Basin and Range Physiographic Province, and water-resources 

regions in the Desert Southwest . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Figure 2. Counties in the Basin and Range Physiographic Province . . . . . . . . . . . . . . . . . . . . . 4

Figure 3. Basins identified by each State in the Basin and Range Physiographic 

Province that require ground-water management or monitoring . . . . . . . . . . . . . . . 6

4–13. Graphs showing:

Figure 4. Ground-water and surface-water withdrawal and percentage of total 

withdrawal that is ground water and surface water, 1950–2000

A. Arizona. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

B. California . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

C. Nevada. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

D. New Mexico . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

E. Utah. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Figure 5. Ground-water withdrawal in Arizona and the Upper Santa Cruz Basin 

and annual and mean-annual precipitation at the National Weather 

Service rain gage in Tucson, Arizona . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Figure 6. Ground-water withdrawal in Utah and Salt Lake Valley and annual 

and mean-annual precipitation at the National Weather Service 

rain gage in Salt Lake City, Utah . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Figure 7. Population and projected population for Arizona, Utah, Nevada, 

New Mexico, and California, 1950–2025 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Figure 8. Population for selected counties within the Basin and Range 

Physiographic Province, 1950–2000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Figure 9. Population, and ground-water, surface-water, and total withdrawal 

for domestic water use, 1950–2000

A. Arizona. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

B. California . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

C. Nevada. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

D. New Mexico . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

E. Utah. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Figure 10. Percentage of ground-water and surface-water withdrawal for 

agricultural and domestic water uses, 1950–2000:

A. Arizona. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

B. California . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

C. Nevada. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

D. New Mexico . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

E. Utah. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Figure 11. Per-capita use of public-supply water in Arizona, California, Nevada, 

New Mexico, and Utah, 1960–2000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Figure 12. Total withdrawal, and ground-water, surface-water, and total 

withdrawal for agricultural uses, and irrigated acreage, 

1950–2000: 

A. Arizona. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

B. California . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

C. Nevada. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

D. New Mexico . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

E. Utah. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Figure 13. Crop-application rates in Arizona, California, Nevada, New Mexico, 

and Utah, 1965–2000. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
v

Tables

Table 1 Availability of water-use and related data for the Desert Southwest, 

1900–2000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Table 2. Freshwater withdrawal by water-use category and source in Arizona, 

California, Nevada, New Mexico, and Utah, 1950–2000. . . . . . . . . . . . . . . . . . . . . . . . 9

Table 3. Freshwater withdrawal by water-use category and source in the 

California, Great Basin, lower Colorado, and Rio Grande 

water-resources regions, 1965–1995 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Table 4. Freshwater withdrawal by source in counties in the Basin and Range 

Physiographic Province, 1985–2000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Table 5. Irrigated acreage in counties in the Basin and Range Physiographic 

Province, 1985–2000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Table 6. Populations of Arizona, California, Nevada, New Mexico, and 

Utah, 1950–2000. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Table 7. Public supply per-capita use in Arizona, California, Nevada, New Mexico, 

and Utah, 1960–2000. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Table 8. Freshwater withdrawal by water-use category in counties in the 

Basin and Range Physiographic Province, 1985–2000. . . . . . . . . . . . . . . . . . . . . . . . . 23

Table 9. Public supply per-capita use in counties in the Basin and Range 

Physiographic Province, 1985–2000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Table 10. Percentage of State populations represented by counties in the Basin 

and Range Physiographic Province, 1950–2000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Table 11. Population in the California, Great Basin, lower Colorado, and 

Rio Grande water-resources regions, 1965–1995 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Table 12. Irrigated acreage in Arizona, California, Nevada, New Mexico, and 

Utah, 1964–2000. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Table 13. Irrigated acreage in the lower Colorado, Great Basin, California, 

and Rio Grande water-resources regions, 1965–1995 . . . . . . . . . . . . . . . . . . . . . . . . . 29

Table 14. Crop-application rates in Arizona, California, Nevada, New Mexico, 

and Utah, 1965–2000. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Conversion Factors

Temperature in degrees Fahrenheit (oF) may be converted to degrees Celsius (oC) as follows:

oC=(oF-32)/1.8.

Multiply By To obtain

inch (in) 2.54 centimeter

mile (mi) 1.609 kilometer

acre 0.004047 square kilometer

square mile (mi2) 259.0 hectare

square mile (mi2) 2.590 square kilometer 

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

acre-foot (acre-ft) 0.001233 cubic hectometer 

gallon per day (gal/d) 0.003785 cubic meter per day

Water-Use Trends in the Desert Southwest—1950–2000

By A.D. Konieczki and J.A. Heilman

Abstract 

The population in the Desert Southwest is among the fastest growing in the country. In this area, groundwater supplies have been developed, surface-water resources have been fully appropriated, and conservation 

and conjunctive water-use measures are being used to meet water-resource needs. Complex networks of 

water-distribution systems have been developed to deliver surface-water supplies, and interstate agreements, 

such as the Colorado River Compact of 1922, help manage the distribution of water among many States in 

the Western United States, including Arizona, California, Nevada, New Mexico, and Utah.

The Colorado River, which lies on the borders of Arizona, California, and Nevada, plays an important 

role in supplying water to the Southwest. Water from the Colorado River is used to irrigate extensive 

farmland in the southern California deserts and is delivered to southern and central Arizona through the 

Central Arizona Project canal for domestic and agricultural uses. It is also the source of much of the water 

used for domestic purposes in southern Nevada.

Estimated water-withdrawal and related data were compiled from various sources to identify trends in 

Arizona, California, Nevada, New Mexico, and Utah. More water is used for agriculture than domestic and 

industrial use in these five States. From 1950 to 2000, however, the percentage increase in withdrawal for 

domestic water use exceeded that for agricultural use.

The estimated amount of water withdrawn for domestic, agricultural, and industrial purposes in Arizona, 

California, Nevada, New Mexico, and Utah increased 58 percent, from 39.6 to 62.8 million acre-feet, from 

1950 to 2000. During this period withdrawals for domestic water use, which included self-supplied domestic 

and public supply (all deliveries to residential, commercial, and some industrial users), increased 410 percent 

from 2.0 million to 10.2 million acre-feet and the population in these five Southwestern States increased 

250 percent. From 1965 to 2000, water withdrawals for agriculture, which were primarily for irrigation of 

crops and livestock uses, increased 14 percent in the five States, from 44.0 to 50.2 million acre-feet, while 

irrigated acreage increased 12 percent from 12.6 to 14.1 million acres.

Water-use trends in the Southwest are dominated by water use in California where crop acreage is more 

than twice as large as the combined crop acreages in Arizona, Nevada, New Mexico, and Utah, and the 

population in 2000 was more than three times larger than the combined population of these States. 

Withdrawals for agriculture in California accounted for 62 percent of the water withdrawals for agriculture 

in the five States in 1950 and 68 percent in 2000. Water withdrawals for domestic-water use in California 

declined from 82 percent of the total domestic-water withdrawals in all five States in 1950 to 70 percent in 

2000, indicating that the need for domestic withdrawals increased more in Arizona, Nevada, New Mexico, 

and Utah combined than in California.

The population of California is larger than the combined population of Arizona, New Mexico, Nevada, 

and Utah, but the combined population of these smaller States grew faster than the population of California. 

From 1950 to 2000 the California population increased 220 percent, but the combined population of the four 
2 Water-Use Trends in the Desert Southwest—1950–2000

other States increased 390 percent. From 1960 to 

2000, public supply per-capita use increased in 

Arizona, New Mexico, and California, and 

decreased in Nevada and Utah.

Crop-application rates (water withdrawal for 

irrigation of crops divided by the irrigated crop 

acreage) from 1965 to 2000 ranged from 2.32 acrefeet per acre in Utah in 1975 to 6.21 acre-feet per 

acre in Arizona in 2000. More water is used per acre 

of irrigated land in Arizona than in the other four 

States. This could be due to several reasons, 

including differences in climate, conveyance losses, 

length of growing season, and type of crops grown.

Trends in water withdrawals for industrial use 

are difficult to identify because of differences in 

data reporting from year to year. From 1950 to 2000, 

withdrawal for industrial use in the five States was 

generally less than 6 percent of the total withdrawal. 

Withdrawal for industrial use was less than 4 

percent of the total withdrawal in Arizona, except in 

1990; industrial withdrawal was less than 6 percent 

in California and less than 7 percent in Nevada, 

New Mexico, and Utah, except in 1980 when in 

Utah it was almost 12 percent of the total 

withdrawal.

From 1950 to 2000, ground-water withdrawals 

increased 324 percent in Nevada, 147 percent in 

New Mexico, 208 percent in Utah, and 52 percent in 

California. Ground-water withdrawal decreased 

15 percent in Arizona. For all five States, groundwater withdrawals increased 62 percent.

INTRODUCTION

Information on trends in water use and major wateruse categories are needed to evaluate current and 

potential future water needs. The possible effect on water 

resources can be determined by identifying the locations 

and sources of water that was used. This is of particular 

importance at a regional scale in the Southwest. 

Comparisons of water use, water-use trends, and sources 

of water among the Southwestern States could assist in 

the distribution management of limited water resources.

The population in the Southwest is among the fastest 

growing in the United States. The region could once be 

described as vast, open, and undeveloped, with isolated 

population clusters where water was readily available. 

In the last few decades, however, the populated areas 

have expanded becoming large metropolitan areas, and 

development has not always occurred where water is 

readily available. Large areas of the Southwest remain 

undeveloped, primarily because publicly owned land is 

extensive. Federal, State, city, and county land 

ownerships are limiting factors in land development, and 

water availability may be another. Development of 

farmland in valleys where water is available is a typical 

pattern in the Southwest. Recent population growth in the 

Southwest has affected land use such that some 

undeveloped desert land has been converted in the 

expansion of suburbs and construction of shopping 

malls, and some irrigated land is fallow or has been 

urbanized.

Purpose and Scope

Compilation of existing water-use and related data is 

part of the Southwest Ground-Water Resources project 

that is supported by the Ground-Water Resources 

Program of the U.S. Geological Survey (USGS) Office 

of Ground Water. The project area comprises the alluvial 

basins in the Basin and Range Physiographic Province as 

defined by Fenneman (1931) in southern California, 

southern Arizona, Nevada, western Utah, and the Rio 

Grande drainage in New Mexico; however, data and 

analysis for this report are presented primarily for the 

entire States because the spatial and temporal availability 

of water-use and other related data are mainly reported 

by State, and separation of data by basin was not possible 

(fig. 1). Discussion also includes water-use trends of the 

58 counties and 4 water-resources regions within the 

alluvial basins in the Basin and Range Physiographic 

Province and the Rio Grande Basin in New Mexico for 

periods of available data (figs. 1 and 2).

Data from 1950 to 2000 were compiled and 

examined to identify changes over time in ground-water 

and surface-water withdrawals for agricultural, 

domestic, and self-supplied industrial water uses for the 

States, counties, and water-resources regions. 

Withdrawals for agricultural use include water used for 

crop irrigation and, when reported, for livestock use. 

Withdrawals for domestic use include reported public 

water supply as well as self-supplied domestic use. 

Withdrawals for industrial water use include selfsupplied water used for mining, thermoelectric, and other 

general industrial and commercial purposes. Only fresh 

ground water and surface water for all offstream uses 

were compiled. Changes in factors that affect water use, 

such as population and irrigated acreage, are also 

discussed. Because the boundaries of the water-resources 

regions are similar to State boundaries, water-use trends 

within the water-resources regions are discussed only 

when they differ from the trends within the States.
Introduction 3

120o

110o

105o

35o

40o

0 100 200 MILES

0 100 200 300 KILOMETERS

CALIFORNIA

Base from U.S. Geological Survey

digital data, 1972, 1:2,000,000

Alber Equal-Area Conic projection

N E VA DA

Great Basin

UTAH

ARIZONA

Lower Colorado

NEW 

MEXICO

Rio Grande

Basin

and

Range

Physiographic

Province

115o

Figure 1. States, Basin and Range Physiographic Province, and water-resources regions in the Desert Southwest.
4 Water-Use Trends in the Desert Southwest—1950–2000

120o

110o

105o

35o

40o

NEW 

MEXICO

ARIZONA

UTAH

N E VA DA

NYE

LYON

INYO

CARSON CITY

DOUGLAS

ELKO

HUMBOLDT

PERSHING

CHURCHILL

MINERAL

WASHOE

STOREY

DOÑA

ANA

OTERO

CATRON

GRANT

GILA

YUMA

LA PAZ

RIVERSIDE

SAN BERNARDINO

IMPERIAL

COCHISE

LUNA

SIERRA

SOCORRO

SANDOVAL SANTA FE

LINCOLN

CALIFORNIA

ESMERALDA

MONO

BERNALILLO

VALENCIA

HIDALGO

SANTA CRUZ

PIMA

PINAL

MARICOPA

YAVAPAI

MOHAVE

CLARK

LINCOLN

WHITE

PINE

IRON

BEAVER

MILLARD

JUAB UTAH

TOOELE

WEBER

DAVIS

SALT LAKE

BOX

ELDER

CACHE

GRAHAM

GREENLEE

EUREKA

LANDER

0 100 200 MILES

0 100 200 300 KILOMETERS

Base from U.S. Geological Survey

digital data, 1972, 1:2,000,000

Alber Equal-Area Conic projection

Basin

and

Range

Physiographic

Province

115o

Figure 2. Counties in the Basin and Range Physiographic Province.
Regional Setting 5

Previous Investigations

National water-use trends have been noted in 

previous reports by many authors in the USGS series of 

reports titled “Estimated Use of Water in the United 

States.” Regional water-use trends for different water-use 

categories are discussed in Mann and others (1983) and 

U.S. Geological Survey (1990).

REGIONAL SETTING

The combined area of California, Arizona, Nevada, 

New Mexico, and Utah is 583,000 square miles. The five 

States incorporate five physiographic provinces 

(Fenneman, 1931). The most prominent province is the 

Basin and Range Physiographic Province, which 

comprises about 50 percent of the area. The Basin and 

Range Physiographic Province encompasses 58 counties 

in 5 States and 4 water-resources regions. The four waterresources regions are the lower Colorado, California, 

Great Basin, and Rio Grande (fig. 1).

Precipitation in the five States ranges from about 

3 inches per year in the southern California, Arizona, and 

Nevada deserts to more than 100 inches per year in 

northern California. The two driest States in the country 

are Nevada and Utah which have average annual rainfalls 

of 9 and 13 inches, respectively. Temperatures vary 

considerably throughout the five States. In the desert 

areas, temperatures are mild in the winter and hot in the 

summer, and in the higher elevations and northern part of 

the area the temperature ranges from cold in the winter to 

mild in the summer. Most notable in the desert areas of 

the five States are the diurnal temperature swings, which 

commonly are about 30°F. 

WATER RESOURCES

Surface-Water Resources

Surface water is a fully allocated resource in the arid 

Southwest. Municipal, State, and Federal laws govern its 

use and distribution so that the demands of a growing 

population can be met. There are few major rivers to 

supply the demand for surface water. Complex networks 

of water distribution systems have been developed to 

deliver surface-water supplies where needed, and 

interstate agreements, such as the Colorado River 

Compact of 1922, help manage the distribution of water 

among Arizona, California, Colorado, Nevada, 

New Mexico, Utah, and Wyoming. 

The Colorado River, which lies on the borders of 

Arizona, California, and Nevada, and flows across the 

southeastern part of Utah, plays an important role in 

supplying water to the Southwest. Water from the 

Colorado River is used to irrigate extensive farmland in 

the southern California deserts and also is delivered to 

central and southern Arizona through the Central Arizona 

Project (CAP) canal for irrigation of crops and publicsupply use. The Colorado River is the source of much of 

the water used for public supply in southern Nevada. 

With the exception of the Colorado River drainage, most 

of the surface water in Utah has been appropriated. The 

Central Utah Project was designed to deliver water from 

the Colorado River Basin in eastern Utah to the more 

populated areas in central Utah. There is also an 

international agreement between the United States and 

Mexico for delivery of Colorado River water to Mexico.

The Rio Grande flows from north to south in the 

western half of New Mexico. Water stored in reservoirs 

along the Rio Grande is used to irrigate crops in 

New Mexico and Texas, and like the Colorado River, 

there is an international agreement for delivery of water 

to Mexico.

The densest population in the Southwest is in 

southern California where the climate is generally 

semiarid to arid and water availability is limited. Some of 

the water for use in the metropolitan areas in California is 

transported from northern and central California through 

the California Aqueduct and from the Colorado River 

through the Colorado River Aqueduct.

Dams have been built on the major rivers in the 

Southwest to store water for various purposes, including 

irrigation, domestic water supply, hydroelectric power, 

and recreation. Maximum storage capacity in the major 

reservoirs is about 42 million acre-ft in Arizona, about 

49 million acre-ft in California, about 31 million acre-ft 

in Nevada, about 10 million acre-ft in New Mexico, and 

about 7.5 million acre-ft in Utah. (Ruddy and Hitt, 1990).

Conjunctive use of water—temporary storage of 

unused surface water in the aquifer to be withdrawn 

later—is becoming a popular and important method of 

managing water to help meet the needs of the large and 

growing population in the Southwest. In California, the 

Conjunctive Water Management Branch was established 

to assist local agencies in developing conjunctive wateruse projects, and in Arizona, the legislature established 

the Underground Water Storage and Recovery program 

to allow for underground storage of surplus water 

supplies and withdrawal at a later date as needed. In the 

Las Vegas, Nev., area, the Southern Nevada Water 

Authority has recharged more than 242,000 acre-ft of 

Colorado River water since 1988 (Advisory Committee 

for Groundwater Management and the Southern Nevada 

Water Authority, 2002), and in Tucson, Ariz., more than 
6 Water-Use Trends in the Desert Southwest—1950–2000

15,000 acre-ft of water from the Colorado River is 

recharged annually to be used at a later time (Tucson 

Water, 2002).

Ground-Water Management

The lack of infrastructure to get water where it was 

needed and the occasionally limited availability of 

surface water owing to climate conditions contributed to 

the need to develop ground-water supplies. Development 

of ground-water supplies also became a necessity as 

surface-water supplies were allocated. Political, 

hydrological, and geographical boundaries affect the 

distribution of water in the Southwest. Each State has 

statutes that affect the distribution and management of 

water. Generally, surface water in the West is governed 

by prior appropriation; the rules that control groundwater allocation, distribution, and management vary 

from State to State.

In 1980, the Arizona legislature enacted the Arizona 

Groundwater Management Code (Arizona Department 

of Water Resources, 2003). The code established three 

levels of ground-water management. In areas where 

ground-water withdrawal was the greatest, Active 

Management Areas (AMAs) were established. In 

farming areas where withdrawal was not as large, 

Irrigation Non-Expansion Areas (INAs) were 

established. There are general conditions of groundwater management for the remainder of the State. 

Arizona established five AMAs and three INAs in areas 

in which ground-water overdraft conditions were 

identified (fig. 3).

120o

110o

105o

35o

40o

0 100 200 MILES

0 100 200 300 KILOMETERS

Salt Lake

Valley 

Upper Santa Cruz Basin 

ARIZONA

UTAH

N E VADA

CALIFORNIA

NEW MEXICO

Arizona pumpage:

 Active Management Area

 Irrigation Non-expansion Area

California overdraft condition

Nevada designated basin

New Mexico declared basin

Utah basin with significant

 ground-water development

EXPLANATIO N

Basin

and

Range

Physiographic

Province

Base from U.S. Geological Survey

digital data, 1972, 1:2,000,000

Alber Equal-Area Conic projection

115o

Figure 3. Basins identified by each State in the Basin and Range Physiographic Province that require ground-water management or monitoring.
Data Availability 7

California does not have a statewide ground-water 

management code. Ground-water is managed by local 

agencies. The California Department of Water 

Resources, however, monitors and assists local agencies 

with ground-water issues. In Bulletin 118–80, the 

California Department of Water Resources (1980) reports 

that conditions in 42 ground-water basins “indicate 

overdraft” or provide evidence of “adverse impacts from 

ground-water overdraft.” Furthermore, of those basins 

adversely affected, 11 are “subject to critical conditions 

of overdraft.” The California Department of Water 

Resources identifies a basin as “subject to critical 

conditions of overdraft” when “continuation of present 

water management practices would probably result in 

significant adverse overdraft-related environmental, 

social, or economic impacts” (fig. 3).

In Nevada, the Office of the State Engineer, under 

the Nevada Department of Conservation and Natural 

Resources, manages the surface- and ground-water 

resources. Designated or Administered Groundwater 

Basins have been identified where “permitted groundwater rights approach or exceed the estimated average 

annual recharge and the water resources are being 

depleted or require additional administration.” The State 

Engineer’s office in Nevada has designated 115 of 

232 basins as needing management of the ground-water 

resources (fig. 3; Horton, 2001).

In Utah, where the State Engineer administers all 

water rights, 36 areas of “significant ground-water 

development” have been identified (fig. 3; Burden and 

others, 2000). In most of these areas, ground-water 

withdrawal is less than the estimated recharge.

About 90 percent of the area in New Mexico is in 

“declared ground-water basins” where appropriation of 

ground-water resources is by permit only (Wilson and 

Lucero, 1997). The declared ground-water basin 

boundaries do not generally have hydrological 

significance, but are delineated for administrative or 

ground-water management purposes (fig. 3).

DATA AVAILABILITY

Although withdrawal data were compiled from many 

published reports, the main sources of data were the 

series of USGS Circulars titled “Estimated Use of Water 

in the United States,” published every 5 years since 1950, 

and the USGS water-use Web pages (USGS, 2003). 

Withdrawal data were published by water-use region 

from 1955 to 1965, but the region boundaries were 

redefined in 1965, and water-resources region boundaries 

were used through 1995. The withdrawal data by region 

for 1955, 1960, and 1965 were not considered in this 

report, and withdrawal data by region were not compiled 

for 2000. Estimated withdrawal data were available by 

county from the USGS water-use Web pages for 1985 to 

1995; data for 2000 were obtained from the USGS State 

offices.

Estimated withdrawal for both fresh ground water 

and surface water for all off-stream water-use categories 

were compiled. The categories for which withdrawal data 

were available varied during the period 1950 to 2000. 

In 1950 and 1955 the rural water-use category included 

withdrawal for self-supplied domestic and livestock. 

In 1960, domestic and livestock withdrawals were 

reported individually in the rural water-use category. 

Estimated withdrawal data for livestock were not 

collected in 2000 for many States, including Arizona, 

Nevada, New Mexico, and Utah. Prior to 1985, estimated 

mining withdrawals were incorporated into the selfsupplied industrial category, and in 2000, estimated 

mining withdrawals were not reported in several States, 

including New Mexico and Nevada.

Additional data were compiled from reports 

published by the Nevada and New Mexico State 

Engineers and California and Utah Departments of Water 

Resources. Ground-water withdrawal data are available 

for selected basins in Arizona from 1915 to 2000 and 

from selected areas in Utah from 1963 to present. 

Population and irrigated-acreage data were obtained from 

the USGS, the U.S. Census Bureau (U.S. Census Bureau, 

2002), and the U.S. Department of Agriculture (USDA, 

1999). Availability of the data used for this report is 

summarized in table 1.

WATER-USE TRENDS, 1950 TO 2000

Evaluation of water-use trends is assisted by review 

of estimated withdrawal of fresh ground water and 

surface water for agricultural, domestic, and industrial 

use in Arizona, California, Nevada, New Mexico, and 

Utah. The States were evaluated together and 

individually. Examination of related water-use data, such 

as population and irrigated acreage, and factors, such as 

per-capita water use and crop-application rates, also 

assist in the analysis of water-use trends.
8 Water-Use Trends in the Desert Southwest—1950–2000

Total Water Withdrawal

There was an increase in total water withdrawal of 

58 percent in the five States from 1950 to 2000 (table 2). 

This is consistent with the increased need for water for 

the expanding population, industry, and the associated 

increased need for agriculture use. Between 1950 and 

2000, total withdrawals increased 81 percent in Nevada, 

72 percent in California, 46 percent in Utah, and 

40 percent in Arizona, and declined 4 percent in 

New Mexico. Maximum withdrawals from 1950 to 2000 

occurred in 1980 in Arizona, California, and 

New Mexico; in 1985 in Nevada; and in 2000 in Utah.

Water-use trends in the Southwest are dominated by 

water withdrawals in California. Crop acreage in 

California is at least twice as large as the combined crop 

acreages in Arizona, Nevada, New Mexico, and Utah, 

and in 2000 the population of California was more than 

three times larger than the combined population of 

Arizona, Nevada, New Mexico, and Utah.

The ranking of each State’s percentages of total 

withdrawal varied slightly from 1950 to 2000. Total 

withdrawal in California represented 63 percent of the 

total withdrawal for all five States in 1950 and increased 

to 69 percent in 2000; Arizona declined from 14 to 

12 percent; New Mexico represented 10 percent of the 

total withdrawal in 1950 and declined to 6 percent in 

2000; Utah declined from 9 to 8 percent; and Nevada 

increased from 4 to 5 percent.

Total withdrawal in the four water-resources regions 

increased 12 percent from 1965 to 1995, and as with the 

State percentages, the portion of the total withdrawal 

represented by each region did not change substantially 

(table 3). From 1965 to 1995, withdrawal increased 

21 percent in the lower Colorado water-resources region, 

14 percent in California, and 12 percent in the Great 

Basin, and decreased 6 percent in the Rio Grande waterresources region.

Ground-water and surface-water withdrawals 

increased 62 and 59 percent, respectively, from 1950 to 

2000 for all five States (table 2). Trends can be noted 

when total withdrawal is separated by source of water for 

the individual States, as is shown in the relatively large 

increases in ground-water withdrawal of 324 percent in 

Nevada and 208 percent in Utah during that time. 

Ground-water withdrawal increased 147 percent in 

New Mexico; this included a large increase between 

1950 and 1955. Ground-water withdrawal increased 

52 percent in California and decreased 15 percent in 

Arizona. One factor that influenced the increases in 

ground-water withdrawal during the 1950s was the 

expanded use of large turbine pumps for irrigation of 

crops.

Table 1. Availability of water-use and related data for the Desert Southwest, 1900–2000

[USGS, U.S. Geological Survey; USDA, U.S. Department of Agriculture. Dashes indicate no data]

Area Population

(source)

Irrigated acreage

(source)

Water use, 

all categories

(source)

Public supply 

per-capita use

(source)

Region

1965 to 1995,

5-year interval

(USGS)

1960 to 1995

5-year interval

(USGS)

1955 to 1995

5-year interval 

(USGS)

---

State

1900 to 1950 

10-year interval 

(U.S. Census Bureau)

1960 to 2000

5-year interval

(USGS)

1965 to 2000

5-year interval

(USGS)

1964 to 1997,

4- to 5-year interval

(USDA)

1950 to 2000

5-year interval 

(USGS)

1960 to 1995

5-year interval 

(USGS)

County

1900 to 1980

10-year interval 

(U.S.Census Bureau)

1985 to 2000

5-year interval 

(USGS)

1985 to 2000

5-year interval

(USGS)

1985 to 2000

5-year interval 

(USGS)

1985 to 1995

5-year interval 

(USGS)
Water-Use Trends, 1950 to 2000 9

Table 2. Freshwater withdrawal by water-use category and source in Arizona, California, Nevada, New Mexico, and Utah, 1950–2000

[In thousands of acre-feet]

State 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

Total withdrawal

Arizona 5,370 8,080 5,620 7,020 7,600 8,610 8,910 7,200 7,230 7,640 7,530

California 25,000 28,600 24,200 34,400 43,300 45,700 49,000 42,000 39,400 40,700 43,100

Nevada 1,740 2,290 2,130 2,300 3,650 3,840 4,060 4,200 3,760 2,530 3,150

New Mexico 3,820 2,980 2,270 3,320 3,500 3,620 4,400 3,670 3,950 3,930 3,650

Utah 3,660 5,170 4,350 4,460 4,750 4,560 5,150 4,690 4,900 4,820 5,340

Total 39,590 47,120 38,570 51,500 62,800 66,330 71,520 61,760 59,240 59,620 62,770

Domestic withdrawal

Arizona 100 160 190 260 380 490 660 720 820 950 1,240

California 1,620 1,510 3,160 4,580 3,960 4,290 4,760 6,100 6,880 6,430 7,180

Nevada 60 70 90 130 160 200 280 340 450 530 730

New Mexico 80 110 140 130 180 240 270 290 340 380 370

Utah 110 210 260 300 340 400 880 510 580 570 730

Total 1,970 2,060 3,840 5,400 5,020 5,620 6,850 7,960 9,070 8,860 10,250

Agricultural withdrawal

Arizona 5,220 7,740 5,280 6,630 6,980 7,890 7,970 6,260 6,060 6,390 6,050

California 23,100 25,900 20,200 28,120 37,200 39,300 41,600 34,600 31,700 32,900 34,200

Nevada 1,660 2,150 1,990 2,150 3,350 3,520 3,520 3,790 3,180 1,850 2,360

New Mexico 3,720 2,820 2,070 3,100 3,190 3,300 4,050 3,210 3,400 3,380 3,210

Utah 3,460 4,690 3,780 3,960 4,100 3,950 3,670 4,060 4,060 4,080 4,330

Total 37,160 43,300 33,320 43,960 54,820 57,960 60,810 51,920 48,400 48,600 50,150

Industrial withdrawal

Arizona 50 180 150 130 240 230 280 220 350 300 230

California 330 1,220 870 1,670 2,180 2,140 2,690 1,270 770 1,350 1,690

Nevada 20 70 50 70 140 120 260 70 130 150 53

New Mexico 20 55 60 90 130 80 80 170 210 170 75

Utah 90 270 310 200 310 210 600 120 260 170 280

Total 510 1,795 1,440 2,160 3,000 2,780 3,910 1,850 1,720 2,140 2,328

Ground-water withdrawal

Arizona 3,320 5,560 3,610 4,690 4,730 5,290 4,730 3,470 3,100 3,170 3,830

California 11,200 12,400 11,800 15,460 20,700 22,000 24,000 16,600 16,300 16,300 17,000

Nevada 200 300 400 530 580 750 790 1,020 1,200 960 849

New Mexico 700 1,730 1,160 1,570 1,720 1,760 2,070 1,690 1,970 1,910 1,730

Utah 370 580 590 690 770 880 1,160 880 1,080 870 1,140

Total 15,790 20,570 17,560 23,940 28,500 30,680 32,750 23,660 23,650 23,210 25,549

Surface-water withdrawal

Arizona 2,060 2,520 2,020 2,330 2,870 3,330 4,180 3,750 4,200 4,440 3,700

California 13,900 16,100 12,400 18,960 22,600 23,800 25,100 25,500 23,200 24,600 26,000

Nevada 1,550 1,990 1,740 1,780 3,070 3,110 3,270 3,190 2,560 1,570 2,300

New Mexico 3,120 1,250 1,090 1,780 1,810 1,890 2,350 2,020 1,930 2,020 1,920

Utah 3,300 4,580 3,770 3,760 4,000 3,670 3,980 3,810 3,830 4,060 4,190

Total 23,930 26,440 21,020 28,610 34,350 35,800 38,880 38,270 35,720 36,690 38,110
10 Water-Use Trends in the Desert Southwest—1950–2000

Table 3. Freshwater withdrawal by water-use category and source in the California, Great Basin, lower Colorado, and Rio Grande water-resources regions, 

1965–1995

[In thousands of acre-feet]

Region 1965 1970 1975 1980 1985 1990 1995

Total withdrawal

California 35,900 43,700 46,000 49,300 42,100 39,700 40,900

Great Basin 6,050 7,510 7,620 8,300 9,080 8,070 6,760

Lower Colorado 7,400 8,070 9,530 9,750 8,280 8,690 8,920

Rio Grande 8,070 6,950 6,050 5,270 6,280 6,730 7,580

Total 57,420 66,230 69,200 72,620 65,740 63,190 64,160

Domestic withdrawal

California 4,580 3,960 4,290 4,750 6,100 6,800 6,430

Great Basin 333 390 458 948 614 701 694

Lower Colorado 336 464 612 849 964 1,240 1,360

Rio Grande 291 371 421 396 550 623 574

Total 5,540 5,185 5,781 6,943 8,228 9,364 9,058

Agricultural withdrawal

California 29,200 38,200 39,300 42,700 34,800 32,200 33,100

Great Basin 5,410 6,660 6,780 6,670 8,340 7,100 5,820

Lower Colorado 6,860 7,320 8,460 8,540 7,070 6,900 7,230

Rio Grande 7,250 6,320 5,530 4,860 5,620 5,970 6,790

Total 48,720 58,500 60,070 62,770 55,830 52,170 52,940

Industrial withdrawal

California 1,720 2,200 1,770 2,800 1,270 821 1,370

Great Basin 415 284 312 706 122 335 240

Lower Colorado 180 291 466 381 255 401 327

Rio Grande 497 256 134 37 108 131 114

Total 2,812 3,031 2,682 3,924 1,755 1,688 2,051

Ground-water withdrawal

California 15,700 20,200 21,300 23,500 16,600 16,100 16,400

Great Basin 1,230 1,230 1,570 1,790 1,850 2,210 1,800

Lower Colorado 4,820 5,040 5,600 5,040 3,700 3,450 3,360

Rio Grande 3,590 2,690 2,580 2,130 1,880 2,400 2,160

Total 25,340 29,160 31,050 32,460 24,030 24,160 23,720

Surface-water withdrawal

California 20,200 23,500 24,700 25,800 25,600 23,500 24,500

Great Basin 4,820 6,170 6,050 6,500 7,230 5,860 4,960

Lower Colorado 2,470 3,140 3,920 4,710 4,600 5,100 5,570

Rio Grande 4,480 4,260 3,360 3,140 4,390 4,320 5,310

Total 31,970 37,070 38,030 40,150 41,820 38,780 40,340
Water-Use Trends, 1950 to 2000 11

In Arizona, ground water was the main source of 

water until the early 1980s when the CAP began 

delivering Colorado River water to Maricopa, Pinal, 

and Pima Counties. In 2000, 51 percent of the total 

withdrawal was from ground water (fig. 4A). Between 

1995 and 2000 there was a 10 percent decline in irrigated 

acreage in Arizona and a 17 percent decrease in surfacewater withdrawals, which accounted for the proportional 

change in ground-water and surface-water withdrawals.

Ground-water withdrawal data are available for 

basins in Arizona from 1915 to 1995, 1998, and 2000 

(Anning and Duet, 1994, Tadayon and others, 1998, 

1999, 2000, and 2001). An example of changing wateruse trends is shown in figure 5, which includes total 

ground-water withdrawals in Arizona and the Upper 

Santa Cruz Basin, precipitation recorded in a rain gage 

near Tucson, Ariz., and mean annual rainfall data for the 

period of record. The figure shows that ground-water 

withdrawal in the Upper Santa Cruz Basin, which is 

mostly in Pima County, increased from 1934 to 1952, and 

fluctuated until 1968 when another period of increasing 

withdrawal began because of population growth in Pima 

County. Periods of greater than average precipitation in 

1978, 1982 through 1984, and 1990 through 1994 were 

coincident with decreased ground-water withdrawal.

California, which has the largest total water 

withdrawal in the country, has a complex waterdistribution and delivery system. Much of the available 

water is in the northern part of the State, but the 

population and water needs are greatest in the southern 

and central parts of the State where the climate is arid to 

semiarid. Between 1960 and 1980, ground-water 

withdrawal in California more than doubled, but then 

declined 31 percent between 1980 and 1985 and 

remained well below the 1980 level through 2000. 

Surface-water withdrawal followed a similar trend 

through 1980, with minor fluctuations through 2000 

(fig. 4B). Possible reasons for the apparent decline in 

withdrawal include water-conservation implementation, 

changes in water allocation, and water-use reporting 

practices.

Prior to 1980, more than 80 percent of the water 

needs for Nevada were met by surface water. Since 1980, 

the trend has been less use of surface water and more use 

of ground water (fig. 4C). The ground-water portion of 

the total water withdrawal increased from 11 percent in 

1950 to 27 percent in 2000. The changes in ground-water 

withdrawal may also be the result of differences in 

reporting of ground-water withdrawal. 

From 1950 to 2000 ground-water withdrawal in 

New Mexico increased from 18 percent of the total water 

withdrawal to 47 percent. New Mexico is primarily 

dependent on surface water to meet its water-use needs, 

but because of the variability in streamflow, the State 

occasionally uses more ground water than surface water, 

as was the case in 1955, 1960, and 1990 (fig. 4D).

Utah, like New Mexico, is primarily dependent on 

surface water for most uses. During most years, surface 

water is more than 80 percent of the water withdrawal in 

Utah. Ground-water withdrawal was 10 percent of the 

total withdrawal in 1950 and 19 percent of the total 

withdrawal in 2000 (fig. 4E).

Ground-water withdrawal data have been collected 

annually in Utah since 1963 and are reported by wateruse category for 35 areas where ground-water resources 

have been developed. Fifteen areas are considered to 

have “significant” ground-water development (fig. 3).

From 1964 to 2000 ground-water withdrawals in the 

Salt Lake Valley (Salt Lake City area) were greater than 

withdrawals from any other basin in Utah. A total of 

110,000 acre-ft of ground water was pumped in the valley 

in 1963, and 145,000 acre-ft of ground water was pumped 

in 2000, an increase of more than 30 percent. It was also 

the area with the largest withdrawal for domestic and 

industrial use. Ground-water withdrawal for domestic use 

increased from 32,500 acre-ft in 1964 to 93,800 acre-ft in 

2000.

Ground-water withdrawal in Utah and in Salt Lake 

Valley, precipitation at Salt Lake City airport, and mean 

annual rainfall are shown in figure 6. Because ground 

water is used to supplement surface-water supplies used 

for agriculture, there is an increase in ground-water 

withdrawal during years with below average rainfall. 

During years with above average rainfall, there is a 

decrease in ground-water withdrawal. For example, 

figure 6 shows that from 1987 to 1990, when the 

precipitation in Salt Lake City was below average, 

ground-water withdrawal, correspondingly, increased.

Water withdrawal data by county are available in 

5-year periods from 1985 to 2000. Sixty-nine of 

152 counties in the 5 Southwestern States showed 

declines in water withdrawals that ranged from 1 to 

72 percent between 1985 and 2000. Total water 

withdrawal increased from 1 to 709 percent in the other 

81 counties, and 2 counties had no change.

The Basin and Range Physiographic Province 

incorporates all or parts of 58 counties in the 

5 Southwestern States (fig. 2). The areas of the counties 

within each State in the Basin and Range Physiographic 

Province represent 65 percent of Arizona, 29 percent of 

California, 42 percent of New Mexico, 42 percent of 

Utah, and 100 percent of Nevada. Overall, these counties 

represent 53 percent of the total area of the five States.
12 Water-Use Trends in the Desert Southwest—1950–2000

A. Arizona

10,000

8,000

6,000

4,000

2,000

0

WITHDRAWAL, IN ACRE-FEET (x1,000)

100

80

60

40

20

0

B. California PERCENTAGE

50,000

40,000

30,000

20,000

10,000

0

WITHDRAWAL , IN ACRE-FEET (x1,000)

100

80

60

40

20

0

C. Nevada PERCENTAGE

5,000

4,000

3,000

2,000

1,000

0

WITHDRAWAL, IN ACRE-FEET (x1,000)

100

80

60

40

20

0

PERCENTAGE

1950195519601965197019751980198519901995200019501955196019651970197519801985199019952000

1950195519601965197019751980198519901995200019501955196019651970197519801985199019952000

1950195519601965197019751980198519901995200019501955196019651970197519801985199019952000

Figure 4. Ground-water and surface-water withdrawal and percentage of total withdrawal that is ground water and surface water, 1950–2000. A, Arizona; 

B, California; C, Nevada; D, New Mexico; E, Utah.
Water-Use Trends, 1950 to 2000 13

100

80

60

40

20

0

D. New Mexico PERCENTAGE

5,000

4,000

3,000

2,000

1,000

0

WITHDRAWAL , IN ACRE-FEET (x1,000)

100

80

60

40

20

0

E. Utah PERCENTAGE

0

WITHDRAWAL , IN ACRE-FEET (x1,000)

5,000

6,000

4,000

3,000

2,000

1,000

EXPLANATION

Ground water Surface water

1950195519601965197019751980198519901995200019501955196019651970197519801985199019952000

1950195519601965197019751980198519901995200019501955196019651970197519801985199019952000

Figure 4. Continued.
14 Water-Use Trends in the Desert Southwest—1950–2000 1915

7,000

6,000

5,000

4,000

3,000

0

PRECIPITATION , IN INCHES AND GROUND-WATER WITHDRAWAL

IN THE UPPER SANTA CRUZ BASIN, IN ACRE-FEET (x10,000)

1920

30

25

2,000

1,000

20

15

10

5

0

1925193019351940194519501955196019651970197519801985199019952000

Ground-water withdrawal in Arizona

Ground-water withdrawal in the Upper Santa Cruz

Precipitation

Mean-annual precipitation

GROUND-WATER WITHDRAWAL IN

ARIZONA, IN ACRE-FEET (x1,000)

1,100

0 GROUND-WATER WITHDRAWAL IN UTAH, IN ACRE-FEET (x1,000)

1,000

900

800

700

600

500

400

300

200

100

196019651970197519801985199019952000

Ground-water withdrawal in Utah

Ground-water withdrawal in Salt Lake Valley

Precipitation

Mean-annual precipitation

PRECIPITATION , IN INCHES AND GROUND-WATER

WITHDRAWAL IN SALT LAKE VALLEY , IN ACRE-FEET (x10,000)

30

25

20

15

10

5

0

Figure 5. Ground-water withdrawal in Arizona and the Upper Santa Cruz Basin and annual and mean-annual precipitation at the National Weather Service 

rain gage in Tucson, Arizona.

Figure 6. Ground-water withdrawal in Utah and Salt Lake Valley and annual and mean-annual precipitation at the National Weather Service rain gage in 

Salt Lake City, Utah.
Water-Use Trends, 1950 to 2000 15

Total withdrawal for all the counties in the Basin and 

Range Physiographic Province increased 3 percent from 

1985 to 2000, an overall increase of 660,000 acre-ft 

(table 4). Surface-water withdrawal increased 

160,000 acre-ft and ground-water withdrawal increased 

500,000 acre-ft during this period. There was a decrease 

in total withdrawal in 26 counties and an increase in total 

withdrawal in 32 counties.

The county in the Basin and Range Physiographic 

Province with the largest increase in total withdrawal 

from 1985 to 2000 (450,000 acre-ft) was Imperial 

County, Calif. Imperial County also had the largest 

increase in surface-water withdrawal (400,000 acre-ft) 

and irrigated acreage of 114,000 acres (table 5). La Paz 

County, Ariz., had the largest increase in ground-water 

withdrawal (225,000 acre-ft). Elko County, Nev., had the 

largest decrease in total withdrawal (470,000 acre-ft) and 

the largest decrease in surface-water withdrawal 

(444,000 acre-ft). Pinal County, Ariz., had the largest 

decrease in ground-water withdrawal (116,000 acre-ft).

Table 4. Freshwater withdrawal by source in counties in the Basin and Range Physiographic Province, 1985–2000 

[In thousands of acre-feet]

County

1985 1990 1995 2000 1985 1990 1995 2000 1985 1990 1995 2000

Ground water Surface water Total

Arizona

Cochise 217 187 255 260 6 5 7 2 223 192 262 262

Gila 34 49 27 14 6 33 18 2 40 82 45 16

Graham 70 69 87 144 145 154 110 49 215 223 198 193

Greenlee 6 18 17 19 14 10 24 9 20 28 41 28

La Paz 99 68 24 324 605 733 681 661 704 801 705 985

Maricopa 1,380 1,190 1,160 1,370 1,400 1,600 1,520 1,040 2,790 2,800 2,680 2,410

Mohave 47 78 155 132 68 85 2 40 114 163 157 172

Pima 260 246 255 318 0 11 41 19 260 256 296 337

Pinal 724 508 555 611 380 342 855 569 1,100 850 1,410 1,180

Santa Cruz 12 11 17 24 0 0 0 1 12 11 17 25

Yavapai 53 119 66 79 25 97 26 13 78 215 92 92

Yuma 471 309 438 408 1,010 1,100 1,130 1,230 1,480 1,410 1,570 1,640

Subtotal 3,373 2,852 3,056 3,703 3,659 4,170 4,414 3,635 7,036 7,031 7,473 7,340

California

Imperial 64 155 104 109 2,710 2,600 2,820 3,110 2,770 2,760 2,920 3,219

Inyo 50 56 81 56 23 84 87 24 72 140 168 80

Mono 73 125 101 87 131 113 147 118 204 239 248 205

Riverside 442 349 431 484 1,190 1,260 1,170 1,370 1,640 1,610 1,610 1,854

San Bernardino 377 555 428 426 277 119 220 245 655 675 648 671

Subtotal 1,006 1,240 1,145 1,162 4,331 4,176 4,444 4,867 5,341 5,424 5,594 6,029

New Mexico

Bernalillo 134 138 148 129 54 74 65 62 188 212 213 191

Catron 1 2 1 1 10 18 18 20 11 21 19 21

Doña Ana 87 146 120 139 377 368 375 414 464 514 495 553

Grant 20 40 36 9 39 26 32 26 59 65 68 35

Hidalgo 41 30 39 34 1 9 7 9 42 39 46 43

Lincoln 9 10 14 9 20 21 25 19 29 31 39 28

Luna 111 103 126 97 33 5 22 4 145 109 147 101
16 Water-Use Trends in the Desert Southwest—1950–2000

Table 4. Freshwater withdrawal by source in counties in the Basin and Range Physiographic Province, 1985–2000—Continued

County

1985 1990 1995 2000 1985 1990 1995 2000 1985 1990 1995 2000

Ground water Surface water, Total

New Mexico—Continued

Otero 28 26 36 31 21 15 16 17 49 41 52 48

Sandoval 8 13 21 20 39 50 55 62 48 63 76 82

Santa Fe 27 25 27 31 27 23 24 20 54 48 51 51

Sierra 10 14 19 13 28 26 29 24 38 40 47 37

Socorro 19 34 42 37 81 103 123 144 100 138 165 181

Valencia 7 16 19 16 127 132 183 162 134 148 202 178

Subtotal 502 597 648 566 857 870 974 983 1,361 1,469 1,620 1,549

Nevada

Churchill 17 30 21 15 342 259 136 162 359 289 157 177

Clark 86 83 90 96 213 305 373 497 298 388 463 593

Douglas 17 17 28 19 224 196 119 149 241 213 147 168

Elko 73 79 62 47 986 838 340 542 1,060 917 402 590

Esmeralda 31 31 34 27 7 5 6 3 38 36 40 30

Eureka 119 140 94 79 68 47 17 44 187 187 111 123

Humboldt 290 305 245 207 370 277 69 237 660 582 314 444

Lander 60 75 74 60 105 73 33 49 165 149 107 110

Lincoln 44 47 40 43 30 21 21 22 73 67 61 65

Lyon 84 106 45 79 315 223 173 173 399 329 218 252

Mineral 7 9 9 8 36 26 16 7 42 35 26 16

Nye 47 55 67 43 42 8 14 16 89 63 81 59

Pershing 23 65 33 27 175 60 64 95 197 125 96 123

Storey 0 0 1 4 1 3 3 5 1 4 4 9

Washoe 60 78 44 59 199 165 128 175 259 243 172 234

White Pine 51 60 66 21 56 40 52 105 107 100 118 126

Carson City 7 7 7 13 6 6 10 14 13 13 17 28

Subtotal 1,016 1,187 960 847 3,175 2,552 1,574 2,295 4,188 3,740 2,534 3,147

Utah

Beaver 48 51 45 59 70 79 100 81 119 129 145 140

Box Elder 72 72 88 71 314 317 327 428 386 388 416 499

Cache 45 47 40 49 217 353 289 281 262 400 328 330

Davis 39 26 24 40 116 147 155 114 155 173 178 154

Iron 148 144 122 151 46 39 51 86 195 183 173 237

Juab 22 31 26 35 118 94 98 62 140 125 124 97

Millard 84 124 86 105 199 182 232 352 283 306 319 457

Salt Lake 94 155 97 108 324 349 336 265 418 504 433 373

Tooele 37 52 69 35 47 37 46 51 84 89 116 86

Utah 122 166 110 169 281 259 224 419 403 425 335 588

Weber 37 56 34 41 208 219 249 201 244 275 283 242

Subtotal 748 924 741 863 1,940 2,075 2,107 2,340 2,689 2,997 2,850 3,203

Total 6,640 6,800 6,550 7,140 13,960 13,840 13,510 14,120 20,610 20,660 20,070 21,270
Water-Use Trends, 1950 to 2000 17

Table 5. Irrigated acreage in counties in the Basin and Range Physiographic Province, 1985–2000

[In thousands of acres. Dashes indicate no data; <, value is less than the number listed]

County 1985 1990 19921 1995 19971 2000

Arizona

Cochise 45 35 52 54 63 57

Gila 1 1 1 2 1 1

Graham 33 33 41 39 40 39

Greenlee 9 3 4 4 5 3

La Paz 99 112 95 79 101 103

Maricopa 439 388 273 352 298 263

Mohave 15 23 19 17 13 16

Pima 29 22 27 29 29 26

Pinal 151 208 213 255 228 199

Santa Cruz 2 1 7 2 6 2

Yavapai 18 25 9 7 9 9

Yuma 446 463 190 231 196 244

Subtotal 1,287 1,314 931 1,071 989 962

California

Imperial 515 518 407 570 438 629

Inyo 12 18 16 11 19 15

Mono 41 46 24 51 31 44

Riverside 264 258 192 237 220 294

San Bernardino 63 57 36 44 41 46

Subtotal 895 897 675 913 749 1,028

New Mexico

Bernalillo 10 9 10 9 11 9

Catron 1 2 2 1 2 2

Doña Ana 76 79 80 72 82 76

Grant 3 3 4 3 3 3

Hidalgo 11 9 9 11 10 12

Lincoln 5 5 5 6 3 4

Luna 41 44 30 45 31 42

Otero 9 7 6 9 6 8

Sandoval 8 9 8 9 11 9

Santa Fe 14 16 8 16 11 17

Sierra 8 8 6 9 6 8

Socorro 20 19 16 19 15 20

Valencia 21 20 13 21 17 21

Subtotal 226 230 197 230 208 231

See footnote at end of table.
18 Water-Use Trends in the Desert Southwest—1950–2000

Table 5. Irrigated acreage in counties in the Basin and Range Physiographic Province, 1985–2000—Continued

County 1985 1990 19921 1995 19971 2000

Nevada

Churchill 64 61 46 45 47 43

Clark 9 7 8 8 6 6

Douglas 48 41 33 39 38 43

Elko 244 210 127 120 205 158

Esmeralda 8 8 14 12 16 9

Eureka 48 45 24 26 49 35

Humboldt 154 135 88 94 157 127

Lander 36 31 27 33 26 31

Lincoln 17 16 18 17 16 16

Lyon 77 64 67 59 74 63

Mineral 7 6 4 9 10 3

Nye 19 12 18 13 17 13

Pershing 42 31 27 29 40 32

Storey 0 0 --- <1 <1 <1

Washoe 40 35 24 23 35 33

White Pine 29 26 29 32 29 34

Carson City 1 1 --- 2 1 2

Subtotal 843 729 554 561 766 648

Utah

Beaver 30 49 34 34 35 36

Box Elder 108 120 121 121 137 150

Cache 95 103 87 87 93 117

Davis 29 30 21 21 22 28

Iron 54 62 52 52 60 66

Juab 24 23 20 20 22 28

Millard 88 113 89 89 99 118

Salt Lake 16 24 16 16 15 20

Tooele 22 28 16 16 19 33

Utah 86 79 84 84 81 110

Weber 34 32 32 32 33 47

Subtotal 586 663 572 572 616 753

Total 3,837 3,833 2,929 3,347 3,328 3,622

1Data from National Agricultural Statistics Service.
Water-Use Trends, 1950 to 2000 19

Domestic Water Use and Population Growth

Even though more water is withdrawn for agriculture 

than for any other category in the Southwest, it is the 

population growth and the associated increased 

withdrawals for domestic uses that have the most notable 

increasing trends. Water withdrawals for domestic use, 

which, for this report, includes public supply and selfsupplied domestic water use, increased 421 percent in the 

five States from about 2.0 million acre-ft in 1950 to 

10.2 million acre-ft in 2000 (table 2). California 

represented 82 percent of the total withdrawal for 

domestic use in 1950 and 70 percent in 2000—the 

decrease due to the relative growth in the other States. 

The total withdrawal for domestic use in the waterresources regions and the total withdrawal for domestic 

use in the five States had similar changes between 1965 

and 1995 of about 64 percent.

Dominated by the growth in Maricopa County, the 

population of Arizona increased by 4.4 million people, 

or 580 percent, from 1950 to 2000, and 40 percent in 

the last decade (table 6 and fig. 7). Between 1990 and 

2000, the population of Maricopa County increased by 

950,000 people, the largest increase of any county in 

the country during the last decade (fig. 8). With the 

increased population, there was a steady increase in water 

withdrawal for domestic use. Annual withdrawal for 

domestic water use increased from 100,000 acre-ft in 

1950 to 1.2 million acre-ft in 2000 (fig. 9A and table 2). 

The increase also is reflected in the percentage of the total 

withdrawal that was used for domestic supply. In 1950 

withdrawal for domestic use was 2 percent of the total 

withdrawal, and in 2000 it was 16 percent of the total 

withdrawal (fig. 10A). Public supply per-capita use 

increased in Arizona from 145 gal/d in 1960 to 219 gal/d 

in 2000 (table 7 and fig. 11).

Table 6. Populations of Arizona, California, Nevada, New Mexico, and 

Utah, 1950–2000

[In thousands. Data from U.S. Census Bureau, 2002]

State 1950 1960 1970 1980 1990 2000

Arizona 750 1,302 1,771 2,718 3,665 5,131

California 10,586 15,717 19,953 23,668 29,760 33,872

Nevada 160 285 489 800 1,202 1,998

New Mexico 681 951 1,016 1,303 1,515 1,819

Utah 689 891 1,059 1,461 1,723 2,233

Total 12,866 19,146 24,288 29,950 37,865 45,053

POPULATION—ARIZONA , UTAH , NEVADA ,

AND NEW MEXICO (x1,000,000 )

7

6

5

4

3

0

2

1

8 5

4

3

2

1

0

Arizona

Utah

Nevada

New Mexico

California

POPULATION—CALIFORNI A (x10,000,000 )

1950195519601965197019751980198519901995200020052010201520202025

POPULATION (x1,000,000 )

2.0

3.0

2.0

1.0

1.5

0.5

0

4.0

Maricopa Co., Arizona

Clark Co., Nevada

Bernalillo Co., New Mexico

San Bernardino Co.,

 California

Salt Lake Co., Utah

Washoe Co., Nevada

Riverside Co.,

 California

Pima Co.,

 Arizona

195019601970198019902000

Figure 7. Population and projected population for Arizona, Utah, Nevada, 

New Mexico, and California, 1950–2025.

Figure 8. Population for selected counties within the Basin and Range 

Physiographic Province, 1950–2000.
20 Water-Use Trends in the Desert Southwest—1950–2000

1,500

1,200

900

600

300

0

A. Arizona WITHDRAWAL , IN ACRE-FEET (x1,000)

POPULATION (x10,000 )

0

5,000

4,000

3,000

2,000

1,000

0

6,000

19501955196019651970197519801985199019952000

8,000

0

B. California WITHDRAWAL , IN ACRE-FEET (x1,000)

POPULATION (x10,000 )

6,000

4,000

2,000

1,000

800

600

400

200

1,000

800

600

400

200

3,000

2,000

1,000

0

4,000

POPULATION (x10,000 )

1,500

1,000

500

0

2,000

POPULATION (x10,000 )

1,500

1,000

500

0

2,000

19501955196019651970197519801985199019952000

C. Nevada WITHDRAWAL , IN ACRE-FEET (x1,000)

19501955196019651970197519801985199019952000

0

E. Utah WITHDRAWAL , IN ACRE-FEET (x1,000)

POPULATION (x10,000 )

2,000

500

1,000

1,500

0

2,500

19501955196019651970197519801985199019952000

D. New Mexico 1950 1955

196019651970197519801985199019952000

400

0

WITHDRAWAL , IN ACRE-FEET (x1,000)

300

200

100

EXPLANATIO N

Domestic use:

 Ground water

 Surface water

 Tota l

Population

NOTE: No population data 

 available for 1955

Figure 9. Population, and ground-water, surface-water, and total withdrawal for domestic water use, 1950–2000; A, Arizona; B, California; C, Nevada; 

D, New Mexico; E, Utah.
Water-Use Trends, 1950 to 2000 21

100

80

60

40

20

0

A. Arizona WITHDRAWAL , IN PERCENTAGE 1950

1955196019651970197519801985199019952000

B. California

C. Nevada

EXPLANATION

Agriculture:

 Ground water

 Surface water

Domestic use:

 Ground water

 Surface water

100

80

60

40

20

0

WITHDRAWAL , IN PERCENTAGE

19501955196019651970197519801985199019952000

100

80

60

40

20

0

WITHDRAWAL , IN PERCENTAGE

19501955196019651970197519801985199019952000

100

80

60

40

20

0

WITHDRAWAL , IN PERCENTAGE

19501955196019651970197519801985199019952000

100

80

60

40

20

0

E. Utah WITHDRAWAL , IN PERCENTAGE

19501955196019651970197519801985199019952000

D. New Mexico

Figure 10. Percentage of ground-water and surface-water withdrawal for agricultural and domestic water uses, 1950–2000; A, Arizona; B, California; 

C, Nevada; D, New Mexico; E, Utah.
22 Water-Use Trends in the Desert Southwest—1950–2000

The population in California increased by more than 

23 million, or 220 percent, between 1950 and 2000 

(table 6 and fig. 7), and during that same time period, 

withdrawal for domestic use increased from 6.5 to 

17 percent of the total withdrawal (fig. 10B). There was 

a decline in the amount withdrawn for domestic use from 

1950 to 1955, from 1965 to 1970, and from 1990 to 1995 

even though the population continued to increase, 

perhaps owing to water availability and waterconservation measures (fig. 9B). Public supply percapita use in California has varied between 1960 and 

2000, from 182 gal/d in 1970 to 231 gal/d in 1965 (table 

7 and fig. 11).

The population in the desert areas of southern 

California in Riverside and San Bernardino Counties are 

among the fastest growing in the country. Withdrawal for 

domestic use in the five counties in California in the 

Basin and Range Physiographic Province increased 

28 percent from 1985 to 2000 (table 8).

The population in Nevada is increasing faster than 

the population of any other State in the country. From 

1950 to 2000, the population increased 1,150 percent, 

from 160,000 to 2.0 million (table 6 and fig. 7), and in the 

last decade it increased by almost 800,000, or 66 percent. 

Water withdrawal for domestic use in Nevada also was 

increased to meet the needs of the growing population. 

From 1950 to 2000, the domestic water-use portion of the 

total withdrawal increased from 3 percent to 23 percent 

(fig. 10C). There was some variation in the public supply 

per-capita use, but generally it was more than 300 gal/d 

(table 7 and fig. 11). Of the five States, Nevada had the 

largest public supply per-capita use.

Water withdrawals for domestic use in New Mexico 

represented 2 percent of the total withdrawal in the State 

in 1950 and 10 percent in 2000 (fig. 10D). Between 1950 

and 2000, the population in New Mexico increased by 

more than 1.1 million people, or 167 percent. Public 

supply per-capita use in New Mexico increased from 

163 gal/d in 1960 to 203 gal/d in 2000. An anomalously 

low public supply per-capita use value of 126 gal/d in 

1965 (table 7 and fig. 11) was not considered in this 

report.

Water withdrawals for domestic use in Utah was 

3 percent of the total withdrawals in 1950 and 14 percent 

of the total withdrawals in 2000 (fig. 10E). The 

population in Utah increased more than 220 percent, 

from 690,000 to 2.2 million people (table 6 and fig. 7). 

Public supply per-capita use ranged from 269 gal/d in 

1995 to 334 gal/d in 1975 (fig. 11 and table 7). The value 

of 575 gal/d reported in 1980 (Solley and others, 1983, 

page 10) appeared anomalously large and was not 

considered in this report.

The percentages of withdrawal for domestic uses 

that was ground water varies in the five Southwestern 

States. Ground water was the main source of water for 

domestic use in New Mexico and Utah. From 1950 to 

2000 more than 80 percent of the withdrawal for 

domestic use in New Mexico was ground water (fig. 9D).

Table 7. Public supply per-capita use in Arizona, California, Nevada, 

New Mexico, and Utah, 1960–2000

[In gallons per day. Dashes indicate no data] 

State 1960 1965 1970 1975 1980 1985 1990 1995 2000

Arizona 145 147 207 213 230 200 208 206 219

California 198 231 182 186 184 218 228 184 204

Nevada 346 285 306 316 323 326 344 325 338

New Mexico 163 126 205 236 240 226 226 225 203

Utah 301 290 296 334 --- 285 308 269 293

Weighted average 201 224 192 199 212 223 234 197 216 PER-CAPITA USE, IN GALLONS PER DAY

250

200

100

150

350

300

Arizona

California

Nevada

New Mexico

Utah

196019651970197519801985199019952000

Figure 11. Per-capita use of public-supply water in Arizona, California, 

Nevada, New Mexico, and Utah, 1960–2000.
Water-Use Trends, 1950 to 2000 23

Table 8. Freshwater withdrawal by water-use category in counties in the Basin and Range Physiographic Province, 1985–2000

[In thousands of acre-feet]

1985 1990 1995 2000 1985 1990 1995 2000 1985 1990 1995 2000

County Domestic Agriculture Industry

Arizona

Cochise 13 22 16 15 201 159 193 240 9 11 7 6

Gila 9 8 6 7 4 5 6 7 27 69 22 2

Graham 5 4 4 6 190 218 185 187 20 1 0 0

Greenlee 1 1 1 1 16 13 15 15 3 14 19 12

La Paz 4 2 2 5 700 799 708 981 0 0 0 0

Maricopa 460 540 673 834 2,310 2,190 1,840 1,520 19 68 23 56

Mohave 21 25 18 23 75 114 149 148 19 23 22 1

Pima 115 111 119 193 101 78 96 100 44 68 60 44

Pinal 23 22 21 40 1,050 800 1,270 1,130 36 28 20 6

Santa Cruz 4 4 5 10 7 6 13 15 0 0 0 0

Yavapai 15 21 19 27 43 129 36 41 20 65 27 22

Yuma 27 30 28 34 1,440 1,380 1,450 1,600 10 4 0 1

Subtotal 697 790 912 1,195 6,137 5,891 5,961 5,984 207 351 200 150

California

Imperial 21 27 27 35 2,740 2,710 2,880 3,180 17 22 15 7

Inyo 8 5 3 4 63 97 56 76 2 38 108 0

Mono 4 1 3 4 200 227 234 201 1 11 11 0

Riverside 348 376 411 472 1,270 1,180 1,150 1,380 17 51 43 5

San Bernardino 371 381 355 446 239 212 209 205 44 81 84 19

Subtotal 752 790 799 961 4,512 4,426 4,529 5,042 81 203 261 31

New Mexico

Bernalillo 126 129 138 124 57 78 69 65 5 5 6 1

Catron 0 0 0 0 10 20 19 20 1 1 1 0

Dona Ana 23 31 37 39 435 473 447 511 6 10 11 3

Grant 3 4 5 5 31 29 37 30 25 32 27 0

Hidalgo 1 1 2 1 34 32 38 42 7 6 6 0

Lincoln 3 3 3 5 23 26 34 23 2 1 2 0

Luna 4 4 5 5 140 104 141 96 1 1 1 0

Otero 11 12 14 13 37 28 37 34 1 1 2 0

Sandoval 7 12 18 15 39 50 56 62 2 1 2 4

Santa Fe 12 15 18 18 41 33 33 33 1 1 1 0

Sierra 2 2 3 2 35 37 44 35 1 1 1 0

Socorro 2 2 2 3 95 134 160 177 2 1 2 0

Valencia 4 6 8 9 129 141 192 169 1 2 2 0

Subtotal 198 221 253 239 1,106 1,185 1,307 1,297 55 63 64 8
24 Water-Use Trends in the Desert Southwest—1950–2000

Table 8. Freshwater withdrawal by water-use category in counties in the Basin and Range Physiographic Province, 1985–2000—Continued

1985 1990 1995 2000 1985 1990 1995 2000 1985 1990 1995 2000

County Domestic Agriculture Industry

Nevada

Churchill 4 4 5 6 354 281 150 170 2 4 2 0

Clark 211 302 383 526 49 37 36 28 39 49 44 39

Douglas 7 9 12 12 232 203 133 155 1 1 2 0

Elko 10 12 14 16 1,040 893 376 573 12 12 12 0

Esmeralda 0 0 0 0 36 35 39 30 2 1 1 0

Eureka 0 0 0 1 182 170 91 122 4 17 19 0

Humboldt 2 4 5 6 648 568 290 438 10 11 19 0

Lander 1 1 2 2 159 139 97 108 5 8 8 0

Lincoln 1 2 2 2 72 65 59 63 1 0 0 0

Lyon 5 5 6 12 388 320 200 235 5 3 12 4

Mineral 2 2 1 2 40 31 22 14 1 2 3 0

Nye 3 4 7 8 80 50 66 51 6 9 8 0

Pershing 1 2 2 2 196 122 93 120 1 2 2 0

Storey 0 0 0 1 0 0 1 2 1 4 2 6

Washoe 74 81 83 111 179 156 82 121 6 6 7 2

White Pine 3 3 4 3 99 89 102 123 5 7 12 0

Carson City 10 10 10 20 3 3 7 8 0 0 0 0

Subtotal 334 441 536 730 3,757 3,162 1,844 2,361 101 136 153 51

Utah

Beaver 2 2 2 2 116 126 136 135 0 1 7 2

Box Elder 33 18 29 26 349 367 382 472 3 3 5 2

Cache 31 31 25 38 226 366 272 291 5 4 31 1

Davis 39 38 49 49 112 130 127 103 4 5 3 2

Iron 5 7 8 10 169 175 164 224 20 1 1 2

Juab 4 4 4 6 130 120 119 89 6 1 0 1

Millard 3 4 4 5 277 276 275 427 3 25 40 25

Salt Lake 196 246 214 290 202 164 195 67 20 94 24 17

Tooele 11 9 10 9 68 70 68 76 5 10 37 1

Utah 76 91 82 116 305 303 240 448 22 31 12 25

Weber 37 48 61 58 204 219 206 166 4 8 15 17

Subtotal 437 498 488 609 2,158 2,316 2,184 2,498 92 183 175 95

Total 2,420 2,740 2,990 3,730 17,670 16,980 15,820 17,180 540 940 850 335
Water-Use Trends, 1950 to 2000 25

The portion of withdrawal for domestic use that came 

from ground water in Utah decreased from 73 percent in 

1950 to 57 percent in 2000 (fig. 9E). In Arizona, ground 

water was the source for 81 percent of the water used for 

domestic purposes in 1960 and 43 percent in 2000 

(fig. 9A). Generally, more surface water than ground 

water was used for domestic purposes in California from 

1950 to 2000 (fig. 9B). The exceptions, however, were in 

1985 and 1990 when more ground water was used, and in 

1990 and 1995 when equal portions of ground water and 

surface water were used. Since 1975 surface-water 

withdrawals have increased more than ground-water 

withdrawals in order to meet domestic-supply demands in 

Nevada (fig. 9C). Lake Mead, along the Colorado River, 

is a major source of water for domestic use in the southern 

part of Nevada.

Public supply per-capita use presented in this report 

was computed on the basis of total public-supply 

withdrawals and the population served by the publicwater suppliers. Public-supply withdrawals include the 

amount of water delivered by private and public water 

suppliers for domestic use, and include deliveries to 

commercial, industrial, and thermoelectric power users.

Water-withdrawal data reported by county from 

1985 to 2000 indicate that total withdrawals for domestic 

use for the counties in the Basin and Range 

Physiographic Province increased 54 percent (table 8). 

Surface-water withdrawal accounted for almost 

80 percent of the increase. Withdrawals for domestic 

purposes were 12 percent of the total withdrawal in the 

counties in the Basin and Range Physiographic Province 

in 1985 and 18 percent of the total withdrawal in 2000. 

Of the counties within the Basin and Range 

Physiographic Province, Maricopa County, Ariz., which 

had a 22-percent decrease in ground-water withdrawal 

and a 183-percent increase in surface-water withdrawal, 

had the largest increase in withdrawals for domestic 

purposes from 1985 to 2000. Clark County, Nev., had the 

next largest increase in withdrawals for domestic 

purposes. This change in withdrawal also corresponds to 

the order in the change in population. Withdrawals for 

domestic use in Clark County increased 149 percent 

from 1985 to 2000. This increase was composed of a 

190-percent increase in surface-water withdrawal and 

a 44-percent increase in ground-water withdrawal. The 

percentage of withdrawal in Clark County for domestic 

use increased from 71 percent in 1985 to 89 percent in 

2000. During that same period, water imported from the 

Colorado River increased from 155,000 to 438,000 acreft (Coache, 2000).

Among the five States, the largest difference 

between public supply per-capita use in counties in the 

Basin and Range Physiographic Province and public 

supply per-capita use in the entire State is in California 

(tables 7 and 9). The statewide public supply per-capita 

use in California is smaller by at least 30 percent for each 

reported year from 1985 to 2000. The differences in percapita use is perhaps due to the arid climate in the 

counties in the Basin and Range Physiographic Province. 

There was a decline in public supply per-capita use in 

four of the five counties within the Basin and Range 

Physiographic Province in southern California. In that 

area the amount of water withdrawn for public-supply use 

increased 23 percent, while the population served 

increased 48 percent. 

The combined population of Arizona, Nevada, 

New Mexico, and Utah is growing faster than the 

population of California. In 1950, the population of 

California was 10.6 million, and the combined population 

of the four other States was 2.3 million. By 2000, the 

population of California had grown to 33.9 million, an 

increase of 220 percent, and the combined population of 

the four other States in the Basin and Range 

Physiographic Province had grown to 11.2 million, an 

increase of 390 percent.

The population in the counties in the Basin and 

Range Physiographic Province is growing faster than the 

population in counties not in the Basin and Range 

Physiographic Province (table 10). In 1950, 18 percent of 

the population lived in the counties in the Basin and 

Range Physiographic Province compared to 30 percent in 

2000.

Table 9. Public supply per-capita use in counties in the Basin and Range 

Physiographic Province, 1985–2000

[In gallons per day] 

State 1985 1990 1995 2000

Arizona 205 210 210 223

California 338 331 242 282

Nevada 326 344 325 338

New Mexico 233 227 224 197

Utah 277 300 263 284

Weighted average 268 272 244 261

Table 10. Percentage of State populations represented by counties in the 

Basin and Range Physiographic Province, 1950–2000

States 1950 1960 1970 1980 1990 1995 2000

Arizona 89 92 93 93 94 94 94

California 5 6 6 7 9 10 10

Nevada 100 100 100 100 100 100 100

New Mexico 49 50 55 58 60 65 66

Utah 83 87 89 88 88 87 87

All States 18 19 20 24 26 27 30
26 Water-Use Trends in the Desert Southwest—1950–2000

From 1965 to 1995, estimated withdrawal for 

domestic use in the four water-resources regions 

increased 64 percent and the total population in the four 

water-resources regions increased more than 80 percent 

(tables 3 and 11).

Agricultural water use and irrigated acreage

The amount of water withdrawn for agricultural use 

from 1965 to 2000 in the five States increased 14 percent, 

while irrigated acreage increased 11 percent. Withdrawal 

for agriculture in California represented 64 percent of the 

withdrawal for agriculture in all five States in 1965 and 

68 percent of the withdrawal for agriculture in 2000. This 

increased withdrawal reflects increased irrigated acreage 

in California and decreases in acreage in other States.

The areal extent and temporal changes in irrigated 

acreage are important in evaluating water use. Irrigatedacreage data are generally compiled on the basis of State 

and county boundaries by State and Federal agencies. 

Several factors can affect changes in irrigated acreage 

from year to year that do not necessarily indicate trends 

in the amount of irrigated acreage. For example, with 

extreme climate conditions, such as drought, farmers 

may use more water for their crops or may use less water 

if they remove acreage from production. Reduction in 

crop market value may also prompt farmers to reduce the 

amount of acreage in production. Government programs, 

such as crop subsidies, can also effect short-term changes 

in irrigated acreage. In some areas, however, irrigated 

acreage has declined as farmland has been converted to 

residential use, shifting water-use type from agriculture 

to domestic use.

Irrigated-acreage data for 5-year intervals are 

available by State from the USGS for years 1965 to 2000 

(table 12). The National Agricultural Statistics Service 

(NASS) of the U.S. Department of Agriculture published 

data for 4-to 5-year intervals for 1964 to 1997 (U.S. 

Department of Agriculture, 2002). Between the two sets 

of data, the irrigated acreage differs, perhaps owing to 

differences in reporting and compilation years; however, 

the trends are similar. Estimated acreage from the NASS 

was generally less than that reported by the USGS. Both 

data sets indicate an increase in irrigated acreage in the 

five States between the mid-1960s and 1980, a decline 

from 1980 through the mid-1990s, and an increase in the 

last reported data.

Table 11. Population in the California, Great Basin, lower Colorado, and 

Rio Grande water-resources regions, 1965–1995

[In thousands. Data from U.S. Geological Survey] 

Region 1965 1970 1975 1980 1985 1990 1995

Lower Colorado 1,848 2,223 2,640 3,241 3,926 4,747 5,318

Great Basin 1,163 1,213 1,434 1,782 1,980 2,182 2,405

California 18,456 20,009 21,117 23,671 26,358 29,442 32,060

Rio Grande 1,877 1,617 1,991 1,775 2,094 2,229 2,566

Total 23,344 25,062 27,182 30,469 34,358 38,600 42,349

Table 12. Irrigated acreage in Arizona, California, Nevada, New Mexico, and Utah, 1964–2000

[In thousands of acres]

State 1965* 1970* 1975* 1980* 1985* 1990* 1995* 2000*

Arizona 1,200 1,200 1,400 1,300 1,320 1,350 1,090 980

California 8,500 8,700 9,000 9,700 9,580 9,480 9,480 10,100

Nevada 730 830 860 850 840 730 560 650

New Mexico 1,000 1,100 1,100 1,400 940 980 960 1,000

Utah 1,200 1,300 1,700 1,200 1,100 1,290 1,140 1,410

Total 12,630 13,130 14,060 14,450 13,780 13,830 13,230 14,140

State 1964** 1969** 1974** 1978** 1982** 1987** 1992** 1997**

Arizona 1,120 1,180 1,150 1,200 1,100 910 960 1,010

California 7,600 7,240 7,750 8,510 8,460 7,600 7,570 8,710

Nevada 825 753 778 881 830 779 556 765

New Mexico 813 823 867 891 807 718 738 805

Utah 1,090 1,020 970 1,170 1,080 1,160 1,140 1,210

Total 11,448 11,016 11,515 12,652 12,277 11,167 10,964 12,500

*Data from U.S. Geological Survey.

**Data from National Agricultural Statistics Service.
Water-Use Trends, 1950 to 2000 27

10,000

8,000

6,000

4,000

2,000

0

A. Arizona WITHDRAWAL , IN ACRE-FEET (x1,000)

IRRIGATED ACRES (x1,000)

0

19501955196019651970197519801985199019952000

B. California WITHDRAWAL , IN ACRE-FEET (x1,000)

IRRIGATED ACRES (x1,000)

5,000

4,000

3,000

2,000

1,000

6,000

IRRIGATED ACRES (x1,000)

0

1,000

IRRIGATED ACRES (x1,000)

1,200

800

400

0

1,600

19501955196019651970197519801985199019952000

C. Nevada WITHDRAWAL , IN ACRE-FEET (x1,000)

19501955196019651970197519801985199019952000

0

E. Utah WITHDRAWAL , IN ACRE-FEET (x1,000)

IRRIGATED ACRES (x1,000)

1,600

400

800

1,200

0

2,000

19501955196019651970197519801985199019952000

D. New Mexico1950

1955196019651970197519801985199019952000

5,000

0

WITHDRAWAL , IN ACRE-FEET (x1,000)

NOTE: No irrigation data available

 for 1950, 1955, and 1960 for

 California, Nevada,and Utah

EXPLANATION

Tota l withdrawal

Agricultural use:

 Ground water

 Surface water

 Tota l

Irrigated acres

50,000

40,000

30,000

20,000

10,000

0

4,000

3,000

2,000

1,000

0

12,000

10,000

800

200

400

600

8,000

2,000

4,000

6,000

5,000

4,000

3,000

2,000

1,000

1,200

800

400

0

1,600

Figure 12. Total withdrawal, and ground-water, surface-water, and total withdrawal for agricultural uses, and irrigated acreage, 1950–2000; A, Arizona; 

B, California; C, Nevada; D, New Mexico; E, Utah.
28 Water-Use Trends in the Desert Southwest—1950–2000

More than 80 percent of the water withdrawn in 

Arizona is for agriculture. The maximum annual 

withdrawal for agriculture in Arizona was 8.0 million 

acre-ft in 1980 (table 2 and fig. 12A). Agricultural 

withdrawals declined from 97 percent of the total 

withdrawal in 1950 to 80 percent in 2000 (fig. 10A). 

Ground water was the major source for agricultural use 

until 1980 when imported Colorado River water became 

available. In 1950, 62 percent of the water used for 

agriculture was ground water, and in 1995, 38 percent 

was ground water. Owing to the decline in surface-water 

withdrawal, perhaps because of the decline in irrigated 

acreage in the central part of the State, however, groundwater withdrawal was slightly greater than surface-water 

withdrawal in 2000. Irrigated acreage increased 

17 percent between 1965 and 1975, when the maximum 

was reported, and decreased 30 percent between 1975 

and 2000 (table 12).

The percentage of the water withdrawn in California 

for agriculture decreased from 92 percent to 82 percent 

between 1950 and 2000. This decreased percentage was 

the result of increased withdrawal for domestic use and 

more efficient irrigation methods. Surface water made up 

56 percent of the withdrawal for agriculture in 1950 and 

62 percent of the withdrawal for agriculture in 2000 

(fig. 10B). Between 1965 and 2000, irrigated acreage 

increased 19 percent in California.

The estimated water withdrawal for agricultural use 

in Nevada increased 128 percent between 1950 and 1985, 

when the maximum withdrawal for agriculture was 

reported. There was a 51-percent decline in withdrawal 

for agricultural use from 1985 to 1995, and a 28-percent 

increase in withdrawal for agriculture from 1995 to 2000 

(fig. 12C). This trend corresponds with the trend of 

irrigated acreage. The amount of irrigated acreage in 

Nevada decreased 11 percent from 1965 to 2000 and 

24 percent from 1975 to 2000. Withdrawal for 

agricultural use was 95 percent of the total withdrawal in 

1950 and 66 percent of the total withdrawal in 2000. 

Surface water has been the major source of water for 

agricultural use in Nevada.

Withdrawal for agricultural use in New Mexico 

between 1950 and 2000 ranged from a low of 

2.07 million acre-ft in 1960 to a high of 4.05 million 

acre-ft in 1980. The percentage of total withdrawal used 

for agriculture in New Mexico declined from 97 percent 

in 1950 to 88 percent in 2000 (table 2 and fig. 12D). 

There was no net change in irrigated acreage in 

New Mexico between 1965 and 2000; however, irrigated 

acreage declined 28 percent from 1980 to 2000.

Withdrawal for agricultural use in Utah increased 

25 percent from 1950 to 2000, from 3.46 million acre-ft 

to 4.33 million acre-ft. Irrigated acreage increased 

18 percent from 1965 to 2000. Withdrawal for 

agricultural use, however, declined as a percentage of 

total withdrawals, following a trend similar to that of the 

four other States. The withdrawal for agricultural use in 

Utah accounted for 94 percent of the total withdrawal in 

1950 and 83 percent of the total withdrawal in 2000.

The amount of withdrawal for agricultural use in the 

58 counties within the Basin and Range Physiographic 

Province decreased 3 percent from 1985 to 2000 

(table 8). Withdrawal for agricultural use declined from 

86 percent of the total water withdrawn in 1985 to 

81 percent in 2000. The counties using the most water 

from 1985 to 2000 were Imperial County, Calif., and 

Maricopa and Yuma Counties, Ariz. One third of the 

total withdrawal for agricultural use and irrigated acreage 

in the Basin and Range Physiographic Province was in 

these counties.

Irrigated-acreage data shown by county in table 5 

were reported by the USGS for the 5-year compilations 

and by the NASS for 1992 and 1997. There was an 

overall decline of 6 percent, 215,000 acres, between 1985 

and 2000; irrigated acreage decreased in 24 counties, 

increased in 26 counties, and did not change in 8 counties 

in the Basin and Range Physiographic Province.

Irrigated-acreage data in table 13 show that since 

1965 crop acreage declined in the Great Basin and Rio 

Grande water-resources regions, changed little in the 

lower Colorado water-resources region, and increased in 

the California water-resources region. There was an 

overall decline in the four regions of 3 percent. The large 

decline in the Rio Grande water-resources region 

occurred outside the Basin and Range Physiographic 

Province.

Crop-application rates (water withdrawn for 

irrigation of crops divided by irrigated acreage) from 

1965 to 2000 ranged from 2.29 acre-ft/ac in Utah in 1975 

to 6.18 acre-ft/ac in Arizona in 2000 (table 14 and 

fig. 13). Irrigated-acreage data published by the USGS 

were used to compute crop-application rates. The 

average for the eight data sets illustrates the differences 

and shows that, in all reporting years, more water was 

used per acre of irrigated land in Arizona than in each of 

the other four States. This difference could be due to 

several reasons, including differences in climate, 

conveyance losses, length of growing season, and type of 

crops grown. Most of the crops in Arizona have to be 

irrigated because most of the cropland is in the southern 

half of the State where the climate generally is arid. 

Climate can affect crop growing season, and the length of 

the season largely controls the amount of water used. 

Southern Arizona and southern California have longer 

growing seasons that are conducive to a wider variety of 

crop types and multiple crops per year, which result in 

greater water use.
Water-Use Trends, 1950 to 2000 29

Table 13. Irrigated acreage in the lower Colorado, Great Basin, California, and Rio Grande water-resources regions, 1965–1995 

[In thousands of acres] 

Region 1965 1970 1975 1980 1985 1990 1995

Lower Colorado 1,200 1,300 1,500 1,400 1,474 1,527 1,260

Great Basin 1,800 1,900 2,400 1,900 1,904 1,940 1,610

California 8,800 9,000 9,300 10,000 9,750 9,610 9,540

Rio Grande 2,300 2,500 2,000 1,400 1,349 1,384 1,260

Total 14,100 14,700 15,200 14,700 14,477 14,461 13,670

Table 14. Crop-application rates in Arizona, California, Nevada, New Mexico, and Utah, 1965–2000

[In acre-feet per acre] 

State 1965 1970 1975 1980 1985 1990 1995 2000 Average

Arizona 5.51 5.79 5.61 6.12 4.69 4.41 5.83 6.18 5.48

California 3.30 4.25 4.36 4.28 3.59 3.30 3.42 3.39 3.73

Nevada 3.01 4.02 4.08 4.13 4.47 4.33 3.28 3.63 3.91

New Mexico 3.03 2.85 2.96 2.88 3.36 3.44 3.49 3.21 3.13

Utah 3.27 3.12 2.29 3.02 3.65 3.12 3.47 3.07 3.08

Weighted average 3.47 4.15 4.11 4.19 3.74 3.46 3.62 3.55 3.79

4

3

1

2

7

5

6

19651970197519801985199019952000

Arizona

California

Nevada

New Mexico

Utah CROP-APPLICATION RATES, IN ACRE-FEET PER ACRE

Figure 13. Crop-application rates in Arizona, California, Nevada, 

New Mexico, and Utah, 1965–2000.
30 Water-Use Trends in the Desert Southwest—1950–2000

Industrial Water Use

Trends in industrial water use are difficult to identify 

because of the differences in the way that data are 

reported. Some industrial withdrawals are reported 

individually, and some are incorporated into the publicsupply withdrawals. Mining withdrawal estimates are not 

included in all of the 5-year compilations.

No discernible trend was identified for industrial 

use, which including withdrawals for mining increased 

almost 700 percent between 1950 and 1980 and 

decreased in the following years (table 2). In all the 

compilation reports, less than 4 percent of the total 

withdrawal in Arizona was for industrial use, except in 

1990; less than 6 percent of the total withdrawal in 

California was for industrial use; and less than 7 percent 

of the total withdrawal in Nevada, New Mexico, and 

Utah was for industrial use, except in 1980 when in Utah 

it was almost 12 percent. Overall, withdrawal for 

industrial use in the five States was less than 5.5 percent 

of the total withdrawal. Industrial withdrawal was 

generally less than 5 percent of the total withdrawal in 

each water-resources region in the Basin and Range 

Physiographic Province, from 1965 to 1995. In the 

counties within the Basin and Range Physiographic 

Province, withdrawal for industrial use represented 

2.6 percent of the total withdrawal in 1985 and 

1.6 percent of the total withdrawal in 2000 (table 8).

SUMMARY AND CONCLUSIONS

Water-use data published by the USGS by State 

every 5 years from 1950 to 2000, by county from 1985 to 

2000, and by major drainage region from 1965 to 1995 

were the main source of information used to identify 

trends in water use in Arizona, California, New Mexico, 

Nevada, and Utah. Population and irrigated-acreage data 

from Federal, State, and local sources were also used to 

describe changes and identify trends.

Estimated water withdrawal in the five States for 

domestic, agricultural, and industrial uses increased 

58 percent from 39.6 to 62.8 million acre-ft per year from 

1950 to 2000. Withdrawal for domestic use increased 

410 percent from about 2.0 to 10.2 million acre-ft per 

year. Total population in the five States increased 

250 percent. From 1965 to 2000 withdrawal for 

agricultural use increased 14 percent and irrigated 

acreage increased 12 percent.

More than 80 percent of the total withdrawal in the 

five States is for irrigation of crops. From 1965 to 2000 

withdrawal for agricultural use increased from 44.0 to 

50.2 million acre-ft per year while the irrigated acreage 

increased from 12.6 to 14.1 million acres.

From 1960 to 2000 public supply per-capita use 

increased 51 percent in Arizona, 24 percent in 

New Mexico, and 3 percent in California. It decreased 

2 percent in Nevada and 3 percent in Utah. Since 1985 

the largest public supply per-capita use has been reported 

in Nevada. 

Trends in the Southwest for all water-use categories 

are dominated by withdrawals in California, which are 

the largest in the country. From 1965 to 2000, irrigated 

acreage in California was at least twice as much as the 

combined irrigated acreage in Arizona, Nevada, 

New Mexico, and Utah. Withdrawal for agricultural use 

in California represents 62 percent of withdrawal for 

agricultural use in all five States in 1950 and 68 percent 

in 2000. Total estimated water withdrawal in California 

ranged from 25.0 million acre-ft in 1950 to 43.1 million 

acre-ft in 2000. The combined withdrawal in the other 

four States ranged from 14.6 million acre-ft to 

19.7 million acre-ft for the same time period.

Crop-application rates between 1965 and 2000 

ranged from 2.29 acre-ft per acre in Utah in 1975 to 

6.18 acre-ft per acre in Arizona in 2000. More water is 

used per acre of irrigated land in Arizona than in the other 

four States. This difference could be attributed to 

differences in climate, conveyance losses, length of 

growing season, and type of crops grown.

Estimated ground-water withdrawal increased 

62 percent and surface-water withdrawal increased 

59 percent in all five States from 1950 to 2000. There 

were increases in ground-water withdrawal from 1950 to 

2000 of 324 percent in Nevada, 147 percent in 

New Mexico, 208 percent in Utah, and 52 percent in 

California. Ground-water withdrawal decreased 

15 percent in Arizona during this period.

 The major identified trend was the proportional 

increase in withdrawal for domestic water use relative to 

withdrawal for agricultural water use. In 1950, 

94 percent of the total water withdrawal was for 

agricultural use and 5 percent was for domestic use. 

Fifty years later, in 2000, 80 percent of the total water 

withdrawal was for agriculture and 16 percent of the total 

water withdrawal was for domestic use. 

Distribution of available surface water, imposed 

water-conservation measures, legislated limits of 

ground-water withdrawal, and conjunctive use of water 

are being used in some areas where ground-water 

overdraft is occurring. In parts of the Southwest 

approaches to augment and sustain ground-water 

resources include recharge of unused surface water and 

treated wastewater.
Selected References 31

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