Lower Colorado River 

Water Supply 

Its Magnitude and 

Distribution

GEOLOGICAL SURVEY PROFESSIONAL PAPER 486-D

Lower Colorado River

Water Supply

Its Magnitude and

Distribution

By ALLEN G. HELY

WATER RESOURCES OF LOWER COLORADO RIVER-SALTON SEA AREA

GEOLOGICAL SURVEY PROFESSIONAL PAPER 486-D

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1969
UNITED STATES DEPARTMENT OF THE INTERIOR 

STEWART L. UDALL, Secretary

GEOLOGICAL SURVEY 

William T. Pecora, Director

For sale by the Superintendent of Documents, U.S. Government Printing Office 

Washington, D.C. 20402 - Price 60 cents (paper cover)
CONTENTS

Abstract_ _ _______________________________________

Introduction. ______________________________________

The lower Colorado River and environs_____________

Water-control and distribution systems____________

Legal controls._________________________________

Studies of the water supply._________________________

Colorado River at compact point, near Lees Ferry, 

Ariz___________________________________

Actual flow, 1896-1966___________________

Man-caused depletion above compact point. ___ 

Virgin flow, 1896-1966____________.___

Probable future virgin flow_________________

Probable future regulated water supply______

Colorado River between compact point and Davis 

Dam.___________________________________

Gains and losses.___________________________

Effects of storage below compact point- _______

Colorado River and tributaries below Davis Dam_ 

Bill Williams River_______________________

Gila River.._______________________________

Colorado River below all major diversions.___.

Page

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2

2

8

10

11

12

12

12

13

14

17

19

20

21

21

21

22

23

Distribution of Colorado River water_______________

Gross diversions._______________________________

Net diversions________________________________

Distribution of flow during 1961-63---_---__------

Water use and water loss____-----__--_-_-_---__-

Conveyance losses from large canals _______

Lower Colorado River area Davis Dam to 

Mexico ____________-____-_____--_-__--_--

Salton Sea basin. _________________-_-_-_---_

Interrelation of surface water and ground water. _______

Deficiency of the Colorado River supply...____-_----_-

References _____________-___-_---_--_-___--------_--

Appendix.____________---_---_---------_-----------

Colorado River Compact, 1922.____-_-______-__--

Rio Grande, Colorado, and Tijuana Treaty, 1944___

Decree of the U.S. Supreme Court, 1964, Arizona v.

California, Colorado River--.....---------------

Tables of basic data ___-___________-____--_--

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45

49

ILLUSTRATIONS

Page

FIGURE 1. Map of the Colorado River basin showing report area...___-_______-_____-_-_--_------------_----------- D3

2. Map showing principal features of the Colorado River system and water-using areas from Davis Dam to Cibola

VaUey...______________________________________________________________________________________ 4

3. Map showing principal features of the Colorado River system and water-using areas below Cibola Valley._____ 5

4. Map showing principal features of the Colorado River distribution system and water-using areas in the Salton

Sea basin.______________________________________________________________.__--__-___-.._ 6

5. Graph showing relations of annual depletion of streamflow to annual virgin flow at compact point, 1896-1962-_ 13

6. Bar graph of annual flow of the Colorado River at compact point, 1896-1966.----_-_-----_-------_--------- 14

7. Graph showing progressive averages of annual virgin flow at compact point. ________-______________-------_-- 15

8. Cumulative frequency diagram of annual virgin flow at compact point, 1896-1964________________________ 16

9. Graphical storage analysis of the virgin flow of the Colorado River at compact point, 1895-1966____---_-__-- 18

10. Graph showing dimensionless draft-storage-variability relations____________--____-_-------_-__--__-__--- 18

11. Graph showing relations of uniform annual draft to carry-over storage capacity for virgin flow.______________ 19

12. Bar graphs of annual flows of the Bill Williams and Gila Rivers_-__------------_---------_-_---_ ___- 22

13. Bar graph of annual flow of the Colorado River below all major diversions______________-_____-----__---_ 23

14. Graph showing the principal diversions from the Colorado River below Davis Dam, 1908-63_______________ 25

15. Graphs showing annual diversions and return flows for Parker Valley and Yuma Valley, 1930-63._____---__-- 26

16. Bar graphs of depletion of the lower Colorado River in selected years, by States___________________-__-_--- 27

17. Schematic diagram showing distribution of Colorado River water below Davis Dam, 1961-63-_____--_---___- 28

in

CONTENTS V

TABLES

	Page 

TABLE 1. Summary of annual streamflow at compact point, near Lees Ferry, Ariz.__.__-_______._______.___--_-_----_ D12

2. Confidence limits for multiyear means of virgin flow at compact point- -___--_---____--_-____________-_-- 17

3. Gains and losses between compact point and Davis Dam, Ariz.-Nev______________________________________ 20

4. Average annual flow in the lower Colorado River system, 1961-63._-______--__-____--_____-_________-__ 29

5. Water losses from majoi canals, 1961-63_____-----______-______________-_________-______-___-_-_-_--- 30

6. Annual flow of Colorado River at compact point, near Lees Ferry, Ariz., 1896-1966,.__________---___-_-__-- 49

7. Annual flows of the lower Colorado River, 1902-66______-_-_____-__-_____----___-_-___--____---___---_- 50

8. Annual flows of principal tributaries to the lower Colorado River, 1903-66-________________________________ 51

9. Annual diversions and return flows, Lake Mead to Imperial Dam, 1915-66__--__--___----__-___-------_---- 52

10. Annual diversions and return flows at and below Imperial Dam, 1908-66_____--_-___----___-__-_---------- 53

11. Year-end usable contents of reservoirs below compact point, 1934-66..____________________________________ 54

12. Approximate irrigated acreage in principal water-using areas for selected years.____________________________ 54

WATER RESOURCES OF LOWER COLORADO RIVER-SALTON SEA AREA

LOWER COLORADO RIVER WATER SUPPLY ITS MAGNITUDE AND DISTRIBUTION

By AJLLEN G. HELY

ABSTRACT

The water supply in the lower Colorado River depends almost 

entirely on (a) the virgin flow at compact point (Lee Ferry), 

near Lees Ferry, Ariz., (b) the depletion of that flow caused by 

storage above compact point and use of water in the upper 

Colorado River service area, and (c) the provisions of the 

Colorado River Compact for release of water to the lower 

river.

The computed average annual virgin flow at compact point 

for the 71 water years 1806-1966 is 14,900,000 acre-feet, but 

for the 34 years, 1931-64, it is only 12,900,000 acre-feet. During 

the decade 1953-62 the virgin flow was depleted about 2 million acre-feet per year by diversion and use in the upper service 

area. These depletions increased sharply after 1962 and probably 

will continue to increase for many years.

Probability and storage analyses indicate that the water supply 

derived from the Colorado River system above compact point 

to meet all demands for depletion above that point and release to 

the lower river can be sustained at about 13 million acre-feet, 

and that 14 million acre-feet will be available most of the time.

The division of this gross supply between the upper and lower 

service areas depends in part on the existence of facilities to 

enable use of the water in the upper service area and on provisions of the Colorado River Compact. The actual flow at compact point probably will exceed compact requirements most of 

the time until the upper service area's development of water 

supplies progresses considerably and also during subsequent 

periods of abundant runoff.

Below compact point, the losses associated with storage and 

transport of water exceed the inflow from tributaries. Lake 

Mead provides storage capacity for regulation of the flow that 

cannot be regulated above compact point, and appropriate use 

of this capacity can increase the total usable supply below 

Lake Mead. However, if maximum feasible use is made of the 

capacity above compact point, storage in Lake Mead can contribute little if any to the dependable supply below the lake because of the large evaporation losses associated with long-term 

storage.

The annual depletion of the Colorado River caused by use in 

Arizona of water from the main stem increased from less than 

200,000 acre-feet in 1915 to about 1,100,000 acre-feet in 1960. 

Corresponding depletions caused by use of water in California 

were 1,800,000 acre-feet and 4,900,000 acre-feet. In the same years

the principal diversions to Mexico (via the Alamo Canal) were 

240,000 acre-feet and 1,800,000 acre-feet, respectively. As a 

result of such increases in water use and the predominately below average runoff since 1930, flow into the Gulf of California 

has diminished to negligible quantities in recent years. Future 

distribution of the available water supply in accordance with the 

U.S. Supreme Court decree of 1964 will permit a large increase in 

the amount of Colorado River water used in Arizona and will 

require a decrease in the amount used in California, at least 

during periods of below-average runoff.

The beneficial use of water below compact point is accompanied by large losses, some avoidable and some unavoidable. 

Evaporation from the Colorado River and from reservoirs consumes more than a million acre-feet per year, and nearly worthless native vegetation consumes more than half a million acrefeet. Seepage from large canals between Imperial Dam and the 

areas served amounts to about half a million acre-feet, some of 

which is being recovered or is recoverable. Considerably more 

than a million acre-feet per year drains to the Salton Sea. Although drainage is necessary to maintain productivity of the 

land and is also essential to the continued existence of the sea, 

much of this water can be considered a loss from the standpoint 

of irrigation. Annual deliveries of water to Mexico during 1961- 

63 exceeded treaty requirements by about 400,000 acre-feet, which 

can be considered a loss to the United States.

With no new importation of water to the lower Colorado 

River and with natural water yields similar to those of 1931-64, 

any new diversions from the river will depend chiefly on redistribution of the available supply among the States and on more 

effective use of that supply. The increased effectiveness can be 

achieved by such means as channel improvement and canal 

lining; eradication of worthless or low-value vegetation; increased use of holdover surface storage for water-supply rather 

than power needs; more precise deliveries of water to irrigation 

districts and Mexico; and controlled withdrawals of ground 

water from aquifers near the river to utilize their storage capacity, reduce evapotranspiration losses, and provide adequate 

drainage of fields.

The basic allotments of water from the upper Colorado 

River system and the lower river by compact and treaty amount 

to 16,500,000 acre-feet. If these basic allotments do not include 

unavoidable losses from the river and reservoirs below comDl
D2 WATER RESOURCES OP LOWER COLORADO RIVER-SALTON SEA AREA

pact point, the total water supply required for their fulfillment is more than 17,500,000 acre-feet. This potential requirement exceeds the 34-year (1931-64) mean virgin flow by 4,600,000 

acre-feet.

INTRODUCTION

The Colorado River basin includes about 243,000 

square miles in Arizona, California, Colorado, Nevada, 

New Mexico, Utah, and Wyoming in the United States 

and more than 1,000 square miles in Baja California and 

Sonora, Mexico. As most of the drainage basin is arid or 

semiarid, the flow of the river is small relative to its 

drainage area and is insufficient to meet the potential 

demand for water in the service area, which includes 

large areas outside the drainage basin but within the 

same States. Competition for rights to use water from 

the Colorado Biver system has resulted in an international treaty, interstate compacts, legislation at both 

State and national levels, delay in planning and construction of water utilization projects, and seemingly 

endless conflict and litigation.

The Colorado River basin is so extensive and its 

hydrologic characteristics are so diverse that investigations and appraisals of the water resources for certain 

parts of the basin or its service area are most conveniently made separately, even though the interrelations between the parts must be recognized. This investigation 

and appraisal concern most of the area for which the 

lower Colorado River has been the principal source 

of water supply but includes only a part of the "Lower 

Basin" as denned in the Colorado River Compact.

As denned by drainage boundaries, the report area 

consists of the Salton Sea basin and the natural drainage area of the Colorado River below Davis Dam, Ariz.- 

Nev., excluding the Bill Williams River basin above the 

gaging station near Alamo, Ariz., the Gila River basin 

above the Wellton-Mohawk Irrigation and Drainage 

District, and the drainage area of San Cristobal Wash 

(a desert wash that enters the Gila River from the south 

just below the upper end of the irrigation district). The 

investigation extended into Mexico only as far as necessary to delineate the hydrologic problems and relationships near the international boundary. For reasons to 

be explained, the investigation included the main stem 

of the Colorado River up to compact point, Ariz. Figure 

1 shows the relation of the 25,000-square mile report 

area to the entire basin and its surroundings.

This report is one of a series that constitutes an appraisal of the water resources of the area described. It 

concerns waters of the lower Colorado River and their 

disposition, which is largely by diversion for irrigation. 

Ground water related to the river or to irrigation with 

river water and the quality of the water are discussed 

herein only as required for a comprehensive description

of the river. Separate reports on these topics are in preparation. Use of water for the generation of hydroelectric 

power and for recreation is given only incidental consideration because these uses have very little effect on 

the supply of water available for irrigation, municipal, 

and industrial uses. Although power generation has 

been a major factor in the economic feasibility of major 

river-development projects and recreational use of 

reservoirs and several reaches of river channel has become a major factor in the economy of the region, the 

Colorado River Compact established higher priorities for irrigation, municipal, and industrial uses.

The investigation and appraisal were made under the 

general supervision of C. C. McDonald, project hydrologist. Many organizations furnished records or cooperated with the Geological Survey in gathering the 

streamflow data used in this report. Most of the records 

used are contained in the annual series of reports and 

in compilation reports by the U.S. Geological Survey 

(1954, 1964), and the details of such cooperation are 

contained therein. The U.S. Bureau of Reclamation 

furnished additional records of water distribution and 

return flows near Yuma, Ariz.; the United States Section of The International Boundary and Water Commission furnished records of flow at the boundary; the 

Imperial Irrigation District furnished records for Imperial Valley, Calif., including the All-American Canal 

below Pilot Knob and part of the Coachella Canal, and 

also for the Alamo Canal in Baja California; the Coachella Valley County Water District furnished records 

for Coachella Valley, Calif.; and the Upper Colorado 

River Commission furnished estimates of virgin flow 

at compact point, Ariz.

THE LOWER COLORADO RIVER AND ENVIRONS

A legal division of the Colorado River service area 

into an "Upper Basin" and a "Lower Basin" was made 

by terms of the Colorado River Compact at a point on 

the Colorado River 1 mile downstream from the Paria 

River, 17 miles downstream from Glen Canyon Dam, 

and 29 miles downstream from the Arizona-Utah 

boundary. Although the compact refers to this point as 

Lee Ferry, this and many other Geological Survey reports refer to it as compact point to avoid confusion 

with stream-gaging stations that are above the confluence of the two rivers and that are named for the 

community of Lees Ferry at the confluence.

The features of the Colorado River system above 

Davis Dam that are most significant in this study are 

shown in figure 1. The major features below Davis Dam 

and the principal tracts in the report area that use 

Colorado River water are shown in figures 2-4.
119°

LOWER COLORADO RIVER WATER SUPPLY ITS MAGNITUDE AND DISTRIBUTION

114° 109°

D3

37° -

Lower Colorado RiverSalton Sea area

Drainage-basin boundary

Canyon Dam | 

Compact point^^v^ . . _^g

y^Marble Canyon 

damsite

Springs

^O

Grand^ \Cameron 

Canyon

Bridge Canyon ^ Grand Falls 

damsite

\ ", §\Soover

. N » / _ 

\ \ \ UNITEp_STATESi^El Paso

f MEXICO v

32° -

FIGURE 1. The Colorado River basin showing report area.
D4 WATER RESOURCES OF LOWER COLORADO RIVER-SALTON SEA AREA

115°

EXPLANATION 

« \ ^ ^ - ^^~ 

 Drainage-basin boundary

I I I I I I I I M I I I I I I I I I I I I

Approximate boundary 

of water-using area

; §T// / . ^ ^/ ^\ _* - ~-A COLORADO RIVER 

Metropolitan INDIAN RESERVATION

Water District 

of Southern 

California

\

/ X dr

( Blytheo ~t^PALO VERDE VALLEY

V

~-i "f~CIBOLA VALLEY

10

KOFA(MTS (MTJ

10 

I

20 MILES

FIGURE 2. Principal features of the Colorado River system and water-using areas from Davis Dam to Cibola Valley.
LOWER COLORADO RIVER WATER SUPPLY ITS MAGNITUDE AND DISTRIBUTION D5

bo

(3 s

I
D6 WATER RESOURCES OF LOWER COLORADO RIVER-SALTON SEA AREA

To Lake Havasu

EXPLANATION

Drainage-basin boundary

I I I I I I I I I I I I I I I I I I I I I I I I I I

Approximate boundary

of water-using area

FIGURE 4. Principal features of the Colorado River distribution system and water-using areas in the Salton Sea basin.

The Colorado River flows in deep, rugged canyons 

(including the famous Grand Canyon) in nearly all 

the 422-mile reach from compact point to Davis Dam. 

The only diversions from this reach are made by pumping from Lake Mead to the Boulder City-HendersonLas Vegas area in southern Nevada.

Minor canyons alternate with fertile valleys between 

Davis Dam and the river's delta, which is a vast arable 

plain. Although this is one of the most arid parts of 

the United States, agriculture made possible by irrigation with Colorado River water is the mainstay of the 

area's economy. The productivity of the land is enhanced by a growing season that is practically continuous although frost occurs occasionally in most winters. 

Semitropical plants, such ias citrus trees and date palms, 

are grown in parts of the area. A summary of the irrigated acreage in the principal tracts is given in "Appendix" (table 12).

About 6 miles below Davis Dam the Colorado River 

enters Mohave Valley, through which it flows 40 miles 

to Topock, Ariz. Most of the valley is within Arizona, 

and much of it is within the Fort Mohave Indian Reservation. Needles, Calif., at the western edge of the 

valley, is its principal city. A land inventory in 1962
LOWER COLORADO RIVER WATER SUPPLY ITS MAGNITUDE AND DISTRIBUTION D7

by the U.S. Bureau of Reclamation (1963) indicated 

a total flood-plain area of 50,900 acres. Native vegetation, chiefly phreatophytes (plants that depend on shallow ground water), covered 47,600 acres. Only 3,050 

acres were irrigated, although 15,700 acres were considered arable.

The 58-mile reach below Mohave Valley includes 

minor canyons and Chemehuevi Valley, which is now 

largely covered by Lake Havasu. A new town on the 

shore of the lake, Lake Havasu City, Ariz., was started 

in 1964 to provide a setting for light industry and 

recreation.

The next major valley (referred to in some early 

reports as the Great Colorado Valley) is divided into 

three sections Parker, Palo Verde, and Cibola Valleys by meanders of the river. The principal cities 

are Parker, Ariz., at the head of Parker Valley, and 

Blythe, Calif., in Palo Verde Valley. Nearly all of 

Parker Valley is within the Colorado River Indian 

Reservation. The valley includes about 110,000 acres of 

flood plain, 31,700 acres of which were irrigated in 1962 

and most of the remainder was covered by 

phreatophytes. Additional land is being cleared and prepared for irrigation. Almost all of Palo Verde Valley 

and a small area on the adjoining mesa, a total of more 

than 80,000 acres, are irrigated. Phreatophytes cover minor areas along the river and along some drainage channels. During 1962, about 6,000 acres in Cibola Valley 

were irrigated with water pumped from the river or 

from wells near the river (U.S. Bureau of Reclamation, 

1963), and more than 12,000 acres were covered by 

phreatophytes.

Below Cibola Valley the Colorado River flows about 

43 miles through a minor canyon, most of which is 

within the Imperial Wildlife Refuge. It contains numerous small lakes and a few thousand acres of 

phreatophytes.

The river emergies from the mountains at Laguna 

Bam, 14 miles upstream from Yuma, Ariz. A few miles 

farther south the flood plains of the Colorado and Gila 

Rivers merge. Below Yuma the flood plain widens and 

merges with the delta, which extends westward into the 

Salton Sea basin and southward to the Gulf of 

California.

The area 'between the mountains and the international 

boundary, called the Yuma area in this report, is divided 

into several parts by geographic features. On the Arizona side of the Colorado River the flood plain between 

the mountains and Yuma is divided by the Gila River 

into North and South Gila Valleys. Yuma Valley extends from Yuma to the southerly international (Arizona-Sonora) boundary and is separated from South

Gila Valley by Yuma Mesa, a terrace that is generally 

70-80 feet higher than the adjacent valleys. The flood 

plain on the California side of the river includes the 

irrigable lands of the Yuma Indian Reservation, about 

an equal amount of non-Indian land, and the small 

towns of Bard and Winterhaven. The principal city 

within this area is Yuma, Ariz. San Luis, Sonora, is 

just south of the southerly international boundary at 

the lower end of Yuma Valley. Nearly 100,000 acres, 

including most of the flood plains and part of the Yuma 

Mesa, are irrigated; phreatophytes occupy an additional 13,000 acres. A small area in Sonora, south of 

San Luis along the east bank of the river, is irrigated 

by return flow from Yuma Valley and by pumping 

from the river or from wells.

About 12 miles east of Yuma at a narrow gap between 

the Gila and Laguna Mountains, the lower Gila River 

valley joins the common valley of the Gila and Colorado 

Rivers. Colorado River water has been diverted by 

pumping since 1952 to serve the Wellton-Mohawk area, 

which extends about 50 miles along the Gila River 

from the gap to a point a few miles east of the Mohawk 

Mountains. The Wellton-Mohawk Irrigation and Drainage District contains about 75,000 acres of irrigable 

land, and since 1959 the irrigated acreage has exceeded 

50,000. Several thousand acres are covered with 

phreatophytes.

The delta of the Colorado River extends across the 

long structural trough that contains the Gulf of California and the Salton Sea, which is more than 230 feet 

below mean sea level. The delta has gradually risen to 

about 4$ feet above mean sea level, forming a divide 

which prevents waters of the gulf from reaching the 

Salton Sea basin. Levees along the north side of the 

river and the numerous storage reservoirs in the Colorado River basin now prevent any uncontrolled flow of 

Colorado River water into the Salton Sea basin. However, a large part of the delta and other areas in the 

Salton Sea basin are irrigable by gravity diversion from 

the river. Drainage from the Salton Sea basin collects 

in the Salton Sea and is dissipated by evaporation.

The area between the Salton Sea and the international 

boundary, known as Imperial Valley, consists of a central part underlain by fine sediments and a terrace at 

each side (East Mesa and West Mesa) underlain by 

coarser sediments. The central part includes nearly half 

a million acres of irrigated land, the principal cities of 

El Centro and Brawley, and half a dozen smaller towns.

The area south of the international boundary is an 

extension of Imperial Valley and has sometimes been 

included in the area designated by that term. However, 

the irrigated part of the delta in Baja California is
D8 WATER RESOURCES OF LOWER COLORADO RIVER-SALTON SEA AREA

now generally known as Mexicali Valley. The city of 

Mexicali, which had an estimated population of about 

100,000 in 1964, is the principal city of Baja California 

and the largest in the report area. About half a million 

acres are irrigated with water from the Colorado Eiver 

or from ground-water reservoirs that are recharged 

either by irrigation water or by seepage from the river 

and canals.

Coachella Valley is a picturesque intermontane valley 

northwest of the Salton Sea. The ground-water resources were developed early in this century at many 

places in the valley and are still a principal source of 

supply for the upper part of the valley. Because of declining water levels, Colorado Eiver water was imported to the lower part of the valley beginning about 

1948 and now serves more than 60,000 acres. The principle cities are Banning, at the head of the valley in 

San Gorgonio Pass; Palm Springs, a resort city in the 

upper part of the valley; and Indio, in the lower part 

of the valley. More than a dozen smaller towns are scattered throughout the valley.

WATER-CONTROL AND DISTRIBUTION SYSTEMS

A discussion of problems relating to the lower Colorado Eiver necessarily involves many elements of the 

water-control and distribution systems. Consequently, 

the dams and their associated reservoirs, major canals, 

and an aqueduct are briefly described in the following 

paragraphs. The locations are indicated in figures 1-4.

All figures of reservoir storage capacity in this report 

refer to volumes within surface reservoirs, although 

these volumes are supplemented by the ground-water 

capacity of large volumes of surrounding materials 

within the zone of fluctuation of reservoir levels. The 

effects of such supplemental bank storage, however, are 

not clearly defined because they vary with the physical 

characteristics of the materials and with the rapidity 

and magnitude of reservoir fluctuations. Furthermore, 

the gradual reduction of the volumes within reservoirs 

by the accumulation of sediment tends to offset the gain 

from ground-water (bank) storage.

Glen Canyon Dam and Lake Powell. Glen Canyon 

Dam, 17 miles upstream from compact point, near Lees 

Ferry, Ariz., regulates practically all the natural surface outflow from the drainage area above compact 

point. Lake Powell (total usable capacity 25,000,000 

acre-ft, of which 20,900,000 acre-ft is generally active) 

is the principal reservoir of the Colorado Eiver Storage 

Project, which includes five other reservoirs upstream 

(existing or authorized as of 1968) with a combined 

active capacity of more than 6,000,000 acre-feet. Storage 

in Lake Powell began in 1963; storage in two of the

other reservoirs began in 1962. The rated capacity of 

the powerplant at Glen Canyon Dam is 900,000 kw 

(kilowatts).

The primary purpose of regulating the flow at compact point is to enable greater use of water upstream 

rather than downstream. During years of very low runoff after the initial filling of the lake, most of the flow 

of headwater streams can be utilized above compact 

point and withdrawals from storage can provide for 

the releases to the lower river required by the Colorado 

Eiver Compact. Without Lake Powell, any substantial 

development after 1962 of water supplies for use above 

compact point would not have been practicable because 

of the obligations to release water to the lower river.

Hoover Dam and Lake Mead. Hoover Dam, Ariz.- 

Nev. (originally known as Boulder Dam) is 353 miles 

downstream from compact point and 303 miles upstream 

from Imperial Dam. It was the first large river-control 

project on the Colorado Eiver, and it made possible 

most of the later developments downstream. The river 

has been almost completely controlled below the dam 

since storage began in 1935.

The usable capacity of Lake Mead for flood control, 

irrigation and municipal supply, and power generation 

was 28,000,000 acre-feet in 1935 and 27,200,000 acre-feet 

in 1949 (Thomas, 1954, table 1). The rated capacity of 

the powerplant is 1,344,800 kw. All diversions of Colorado Eiver water to Nevada are made by pumping from 

the lake.

Davis Dam and Lake Mohave. Davis Dam, Ariz.- 

Nev., is 67 miles downstream from Hoover Dam, near 

the head of Mohave Valley. The usable capacity of Lake 

Mohave for power generation, for regulation of the 

variable flow released at Hoover Dam, and for regulation of flow at the international boundary as required 

by a treaty between the United States and Mexico is 

1,810,000 acre-feet. Storage began in January 1950. The 

powerplant has a rated capacity of 225,000 kw.

Colorado River aqueduct. The water pumped from 

Lake Havasu into the Colorado Eiver aqueduct, built 

and operated by the Metropolitan Water District of 

Southern California, is one of several supplies for the 

south coastal basins. The aqueduct was constructed in 

two stages, which were completed in 1941 and 1960, respectively. Pumping to reservoirs began in 1939, before 

completion of the first stage. The Metropolitan Water 

District originally included 11 cities and served 

1,600,000 people, but by 1961 it included 91 cities and 

served 7,500,000 people (Smith and Brewer, 1961).

Parker Dam and Lake Havasu. Parker Dam, 

Ariz.-Calif., is 88 miles downstream from Davis Dam, 

just below the Bill Williams Eiver, and 147 miles up-
LOWER COLORADO RIVER WATER SUPPLY ITS MAGNITUDE AND DISTRIBUTION D9

stream from Imperial Dam. The usable capacity of 

Lake Havasu is 619,400 acre-feet, 'but, except in emergencies, the capacity available for reregulation of 

streamflow is only 180,000 acre-feet because the dam was 

built primarily to create a pool from which water could 

be pumped to the Colorado River aqueduct. Storage began in 1938. The rated capacity of the powerplant is 

120,000 kw.

Headgate Rock Dam. Headgate Eock Dam, Ariz.- 

Oalif., 14 miles downstream from Parker Dam, controls 

diversions to Parker Valley for the Colorado Eiver 

Indian Eeservation. The storage capacity of its reservoir is negligible. Prior to completion of the dam in 

1942, diversions were made by pumping from the river.

Polo Verde Dam. The diversion to Palo Verde Valley is made at Palo Verde Dam, Ariz.-Calif., 59 miles 

downstream from Parker Dam and 89 miles upstream 

from Imperial Dam. The dam, completed in December 1957, replaced a rock weir that had been used since 

1945. No appreciable storage capacity was associated 

with either structure.

Imperial Dam. Diversions at Imperial Dam, 26 

miles upstream from the northerly international (California-Baja California) boundary, supply the Yuma 

and Wellton-Mohawk areas and Imperial and Coachella 

Valleys. Also, much of the water scheduled for delivery 

to Mexico is diverted here and returned to the river 

through the siphon-drop powerplant (near Yuma) or 

Pilot Knob powerplant (near the northerly boundary). 

Diversions began in 1988, but some areas now served 

by diversions made at this point were served until 1954 

by diversions made at Laguna Dam, 5 miles downstream.

Several days are required for water to travel the 

great distances from the regulating reservoirs to Imperial Dam (147 miles from Lake Havasu and 236 miles 

from Lake Mohave). Because of changes in weather 

or other unforeseen circumstances, the need for water 

at Imperial Dam sometimes differs from the amounts 

released several days earlier on the basis of water orders. 

The capacity required for reregulation to avoid water 

shortage or waste is not available in the reservoir above 

Imperial Dam because of sedimentation and the negligibly small operating range of water levels. A small auxiliary reservoir (built in 1965) in Senator Wash, about 2 

miles above Imperial Dam, provides 13,400 acre-feet of 

storage capacity. Water is pumped to the reservoir, but 

part of the power required is recovered by generating 

power from the water as it returns to the river.

Gila Gravity Main Canal. The Gila Gravity Main 

Canal receives water through a settling basin at the 

east end of Imperial Dam and delivers it to the North

Gila Valley, the Wellton-Mohawk Canal system (which 

includes three pumping plants and serves the WelltonMohawk area), the South Gila Valley, and a pumping 

plant that lifts water to the Yuma Mesa, all in Arizona. 

Diversions began in 1943.

All-American Canal system. Water diverted at the 

west end of Imperial Dam passes through desilting 

works into the All-American Canal, which serves areas 

in both Arizona and California and also supplies water 

for the generation of hydroelectric power at several 

plants. Diversions began in 1938, but until 1940 the 

water was used only for priming the canal.

Several small diversions from both the All-American 

Canal and a major branch, the Yuma Main Canal, serve 

the California part of the Yuma area. Most of the water 

diverted into the Yuma Main Canal passes through the 

siphon-drop powerplant. Water for irrigation of Yuma 

Valley passes under the Colorado Eiver in an inverted 

siphon, and the water not needed in Yuma Valley returns to the river through the Yuma Main Canal (California) wasteway.

The All-American Canal extends southward along 

the west edge of the river valley to Pilot Knob, where 

part of the flow returns to the river through Pilot Knob 

powerplant and wasteway. The canal then turns westward along the international boundary into the Salton 

Sea basin. About 16 miles west of Pilot Knob, water is 

diverted into the Coachella Canal to serve the lower part 

of Coachella Valley and the remaining water continues 

westward to serve Imperial Valley. Hydroelectric 

power is generated at several drop structures between 

Pilot Knob and Imperial Valley.

Laguna Dam. Prior to construction of Imperial 

Dam, all diversions to the Yuma area were made at Laguna Dam, 5 miles downstream from Imperial Dam. 

The Dam was completed in 1909, and it served part of 

the Yuma area until 1954. It has no present diversion 

functions, but it may help to prevent excessive streambed scour from uncontrolled local floods, and it affords 

limited capacity for reregulation of flows passing Imperial Dam.

Morelos Dam and Alamo Canal. Morelos Dam, 

Ariz.-Baja California, 1.1 miles downstream from the 

northerly international boundary and 27 miles downstream from Imperial Dam, was built by the Mexican 

Government in 1950 to control diversions to Alamo 

Canal without the use of facilities in the United States.

Prior to 1941 the Alamo Canal (originally known as 

Imperial Canal) supplied both Mexicali Valley in Baja 

California and Imperial Valley in California. Diversions from the Colorado Eiver were made at several 

locations near the site of Morelos Dam and were con-
D10 WATER RESOURCES OP LOWER COLORADO RIVER-SALTON SEA AREA

trolled only by headgates. After construction of the 

All-American Canal, the Alamo Canal continued to 

serve Mexioali Valley, and from 1941 to 1950 water 

could be delivered to the Alamo Canal from the AilAmerican Canal through Pilot Knob wasteway and a 

connecting canal that is now plugged.

Return-flow channels. Surplus water and drainage 

from irrigated tracts near the Colorado River return 

to the river in a large and varying number of surface 

channels. Drainage of most tracts is accomplished by 

tile drains or open ditches, but the Wellton-Mohawk 

area and parts of the Yuma area are drained by pumping ground water. Drainage from the Wellton-Mohawk 

area flowed in a lined channel to the Gila River at a 

point near its mouth from 1961 until 1965, when the 

channel was extended to Morelos Dam. Provision is 

made for directing the flow into the Colorado River 

either above or below the dam as requested by Mexico. 

The surplus water in East Main canal in Yuma Valley 

flows across the international boundary and drainage 

from the valley is pumped from the main drain into a 

canal at the boundary for use in Mexico without return 

to the river.

Proposed developments. The major proposed watersupply developments related to the lower Colorado 

River include (a) high dams for power generation at 

Marble Canyon and Bridge Canyon damsites, between 

Glen Canyon Dam and Lake Mead; (b) facilities for 

diverting an average of 1,200,000 acre-feet per year by 

pumping from Lake Havasu into an aqueduct serving 

central Arizona; and (c) improved efficiency of water 

transport and use through such means as deepening and 

straightening the river channel, lining canals, eradicating phreatophytes, and utilizing ground-water reservoirs that are recharged with Colorado River water.

These items have been proposed independently, but 

recently most of them have been incorporated into 

several plans to meet the water needs of the lower 

Colorado River service area or even larger areas, as 

exemplified by plans of the U.S. Bureau of Reclamation 

(1964 a-c). In addition to items such as those noted 

above, these regional plans generally contemplate ultimate importation of water to make up the deficiency in 

the Colorado River supply. The intent of such plans 

is to assure a sufficient supply of water from the main 

stem of the Colorado River or from new imports to 

satisfy an annual consumptive use of at least 7,500,000 

acre-feet in Arizona, California, and Nevada and delivery of 1,500,000 acre-feet to Mexico.

LEGAIi CONTROLS

The need for specific apportionment of waters of the 

Colorado River system was recognized early in the 

present century. Under the generally applied doctrine 

of prior appropriation, the first beneficial use of unappropriated water established a legal right to continued use. The rapid development of Colorado River 

water supplies for certain areas threatened the future 

supply for other less rapidly growing areas, which 

then sought to establish permanent water rights by 

compact, legislation, and court decree. Also, after construction of the All-American Canal, Mexico sought 

protection from excessive depletion of the river by diversions in the United States.

Interpretation of the law applying to the Colorado 

River is highly controversial and is beyond the scope 

of this report. Nevertheless, knowledge of some of the 

provisions of certain documents is essential to an understanding of the water problems because distribution of 

the water is subject to such provisions. Brief comments 

on four documents are given in the following paragraphs. The full text of the Colorado River Compact 

and the most pertinent parts of the Mexican treaty and 

of the U.S. Supreme Court decree of 1964 are included 

in "Appendix" for convenient reference.

The Colorado River Compact, 1928. The distribution of waters of the Colorado River system between 

the Upper and Lower Basins (service areas) is subject to the provisions of the Colorado River Compact 

of 1922 (sometimes called the Sante Fe Compact). The 

compact was ratified in 1923 by six of the seven States 

involved; it became effective in 1929 by presidential 

proclamation, in accordance with a provision of the 

Boulder Canyon Project Act, and it was ratified by the 

seventh State, Arizona, in 1944.

The compact apportions water from the Colorado 

River system to the Upper Basin and the Lower Basin 

and also provides for the satisfaction of any water rights 

of Mexico that "the United States of America shall 

hereafter recognize * * *". Among the provisions most 

pertinent to the lower Colorado River is that of Article III paragraph (d) : "The States of the Upper Division will not cause the flow of the river at Lee Ferry 

to be depleted below an aggregate of 75,000,000 acrefeet for any period of ten consecutive years reckoned 

in continuing progressive series beginning with the 

first day of October next succeeding the ratification of 

this compact." Other provisions applying to release 

of additional water from the Upper Basin have been
LOWER COLORADO RIVER WATER SUPPLY ITS MAGNITUDE AND DISTRIBUTION Dll

interpreted in different ways and, hence, cannot be reliable guides to the flow of the lower river until some of 

the disputed issues have been settled.

Boulder Canyon Project Act, 1928. In the Boulder 

Canyon Project Act, the Congress of the United States 

authorized several actions including the following: (a) 

Approval of the Colorado River Compact with ratification by only six of the seven States involved, (b) construction and operation of a dam (Hoover Dam) in 

Black or Boulder Canyon for the storage of water and 

of a main canal and appurtenant structures (All-American Canal and Imperial Dam) to deliver water to Imperial and Coachella valleys, (c) contracts between the 

Secretary of the Interior and water and power users for 

the storage and delivery of water, the generation and 

delivery of power, and the collection of revenues to reimburse the United States for costs incurred, and (d) 

an agreement among Arizona, California, and Nevada 

for a specified apportionment of Colorado River water. 

No agreement was concluded, but the specified apportionment was confirmed by the U.S. Supreme Court 

in 1964.

Rio Grande, Colorado, and Tijuana Treaty, 1944. 

The distribution of waters of the Colorado River between the United States and Mexico is subject to provisions of the Rio Grande, Colorado, and Tijuana 

Treaty, signed in 1944 and ratified by both countries in 

1945. The treaty allots to Mexico, "A guaranteed annual quantity of 1,500,000 acre-feet" and, when surplus 

water is available, "additional waters of the Colorado 

River system to provide a total quantity not to exceed 

1,700,000 acre-feet * * * a year." Also, it requires that 

delivery of the water allotted to Mexico be made in accordance with schedules prepared by the Mexican Section of the International Boundary and Water Commission subject to limitations specified in the treaty.

Decree of the U./S. Supreme Court, 1961^, Re: Arizona 

v. California, Colorado River. The distribution of water from the main stem of the Colorado River below 

compact point among the States of Arizona, California, and Nevada is subject to provisions of the U.S. 

Supreme Court Decree of 1964.

The decree provides, "If sufficient mainstream water 

is available for release * * * to satisfy 7,500,000 acrefeet of annual consumptive use in the aforesaid three 

states, then of such 7,500,000 acre-feet of consumptive 

use, there shall be apportioned 2,800,000 acre-feet for use 

in Arizona, 4,400,000 acre-feet for use in California, and 

300,000 acre-feet for use in Nevada."

If surplus water is available, 50 percent of the sur321-230 O 69 3

plus is apportioned to California and 50 percent to 

Arizona, except that Nevada may contract for additional deliveries of up to 4 percent of the surplus, and 

then Arizona's share of the surplus will be reduced to 

46 percent.

If less than 7,500,000 acre-feet of water from the 

main stem of Colorado River is available for apportionment among the three States, "the Secretary of the Interior, after providing for satisfaction of present perfected rights in the order of their priority dates without regard to state lines * * * may apportion the amount 

remaining * * * in such a manner as is consistent with the 

Boulder Canyon Project Act * * * and with other applicable federal statutes, but in no event shall more than 

4,400,000 acre-feet be apportioned for use in California."

STUDIES OF THE WATER SUPPLY

Studies of the water supply in the lower Colorado 

River logically begin with the record of streamflow at 

compact point, nears Lees Ferry, Ariz., for the following 

reasons: (a) Most of the water that reaches the lower 

river is runoff from mountainous areas above compact 

point; (b) since the closure of Glen Canyon Dam in 

1963, the flow below the dam has been subject to regulation in accordance with provisions of the Colorado 

River Compact; (c) the most effective guide to future 

streamflow characteristics is obtained by separating the 

effects of man's activities from those of natural phenomena, and this separation can be achieved more accurately 

and more readily at compact point than at points below 

Lake Mead, especially for the period prior to 1963; and 

(d) the streamflow record (including estimates) for 

compact point is one of the longest in the Colorado River 

basin and has been the subject of many previous studies.

The analysis of streamflow at compact point is based 

on water years ending September 30. Water years are 

commonly used because in most parts of the United 

States September 30 is near the end of the growing season and is usually near the time of minimum storage of 

moisture in various forms.

Below compact point, increases in storage, which are 

chiefly a result of inflow from the upper river, generally 

begin in late spring instead of October. Below Davis 

Dam, the growing season is practically continuous, and 

the minimum water demand is near the end of the 

calendar year. Also, most water users maintain operating records by calendar years rather than water years. 

Consequently, the calendar year was used for analyses of 

all records below compact point and for comparisons 

involving such flows and those at compact point.
D12 WATER RESOURCES OF LOWER COLORADO RIVER-SALTON SEA AREA

Streamflow in the lower Colorado River is modified 

so much by storage reservoirs that annual flows and 

average flows for periods of several years are the most 

significant units in a water-supply study. Although 

short-term flood flows of local origin may cause damage 

in the report area, data concerning such floods are too 

meager for effective analysis.

All streamflow records used in the following analyses 

are from U.S. Geological Survey water-supply papers 

except as otherwise noted.

COLORADO RIVER AT COMPACT POINT, NEAR 

LEES FERRY, ARIZ.

The streamflow at compact point depends on the virgin (natural) flow, the depletion of that flow by activities of man, reservoir storage, and the provisions of the 

Colorado River Compact. This report summarizes data 

on the actual flows, estimated depletions, and the virgin 

flows computed as the sum of actual flows and depletions. Analysis of the virgin-flow data provides estimates of the probable magnitude of future virgin flows, 

but the distribution of such flows can be determined only 

for assumed conditions regarding depletions and operation of reservoirs and for assumed interpretations of 

the compact.

ACTUAL FLOW, 1896-1966

Annual flows of the Colorado River at compact point 

since 1923 have been computed as the sum of flows measured at stream-gaging stations on the Colorado River 

and the Paria River above their confluence. Because 

the streamflow record for Colorado River began in 1921, 

it was necessary to estimate only the relatively small 

flow in the Paria River for 1921-22 to complete the record at compact point since 1921.

The Engineering Advisory Committee to the Upper 

Colorado River Basin Compact Commission estimated 

annual flows at compact point for 1914-20 on the basis 

of records of flow at other points on the Colorado River 

and its major tributaries; the U.S. Bureau of Reclamation (1954) used these estimates and made similar estimates for 1896-1913 for studies of the water supply. The 

estimated flows, particularly those for the earliest 

years, are necessarily less reliable than the computed 

flows for the years since 1921, nevertheless, they are of 

sufficient reliability to assist in defining long-term 

streamflow characteristics at this key point on the Colorado River.

The variations in actual flow reflect variations in both 

virgin flow and depletion as described in the following

sections. Annual streamflow data are listed in "Appendix" (table 6) and are summarized in table 1.

TABLE 1. Summary of annual streamflow, in millions of acre-feet, 

at compact point, near Lees Ferry, Ariz., 1896-1966

[Regulated actual flow after 1962 excluded]

Streamflow Water years Actual 

flow

Virgin 

flow

Minimum annual ___ _ ___.

Maximum annual . _ _ _.

Minimum 5-year mean

Maximum 5-year mean.

Minimum 10-year mean_ _ .

Maximum 10-year mean. _ .

Minimum 30-year mean

Maximum 30-year mean____-

34-year average-. _

67-year average

71-year average __ __

1934

1907

1917

.__. 1931-35

.._. 1905-09

1917-21

.... 1931-40

... 1914-23

.__. 1931-60

1934-63

. 1903-32

.___ 1931-64

.___ 1896-1962

1896-1966

4. 397

22. 00 .

9. 146

17. 69 .

10. 15

16.86

11.28

15.63

13.39

5.64

24.0

10.7

19.4

11.8

18.8

i 13. 2

13. 1

17.3

12. 9

15. 1

14.9

i Minimum to 1962, corresponding to minimum actual flow for the same period. 

MAN-CAUSED DEPLETION ABOVE COMPACT POINT

Natural processes and the activities of man both 

cause depletion of streamflow in arid regions. As consumptive use is involved in the terms of the Colorado 

River Compact, knowledge regarding the man-caused 

depletion of the natural water supply in the upper Colorado River system is essential for equitable division of 

the water supply between the Upper and Lower Basins.

The principal components of the man-caused depletion are (a) evapotranspiration resulting from irrigation or other uses within the drainage basin, (b) 

diversions to areas outside the basin, and (c) evaporation from reservoirs. Such depletions began before the 

first streamflow records. The irrigated acreage within 

the drainage basin increased from 310,000 in 1896 to 

1,020,000 in 1910 to 1,425,000 in 1960. Water exports increased from relatively insignificant amounts prior to 

1905 to more than 500,000 acre-feet in 1960. Evaporation 

from reservoirs was relatively small prior to 1962, when 

the reservoir storage was less than 2 million acre-feet. 

All these depletions are increasing, and evaporation is 

a much more significant item since the partial filling of 

Lake Powell and other major reservoirs.

The Engineering Advisory Committee to the Upper 

Colorado River Basin Compact Commission used the 

available hydrologic data to estimate the depletion during the 32-year period 1914-45. The U.S. Bureau of 

Reclamation (1954, p. 145) used the committee's data 

to derive a series of annual depletions for the same 

period and used similar data to estimate annual deple-
LOWER COLORADO RIVER WATER SUPPLY' ITS MAGNITUDE AND DISTRIBUTION D13

tions from 1896 to 1913. The Bureau of Keclamation and 

the Upper Colorado Kiver Commission (successor to 

the Compact Commission) made similar estimates for 

later years. Some investigators have used estimates 

slightly different from those described, but the differences generally are insignificant. Although such estimates have been used for many years, no estimates have 

been accepted by the Upper Colorado River Commission 

as official.

Figure 5 shows the estimated depletion in selected 

years plotted against the corresponding virgin flow. 

It shows a progressive but irregular increase of depletion with time and a variation of depletion with virgin 

flow. The lines in figure 5 should be considered as illustrative and approximate rather than definitive. As 

downward extensions of the lines indicate depletion exceeds the supply at very low flows, such extensions cannot be valid.

I960

,1899

.1898 .1897

.1896

10 15 20 

ANNUAL VIRGIN FLOW, IN MILLIONS OF ACRE-FEET

25

FIGURE 5. Approximate relations of annual depletion of streamflow 

to annual virgin flow at compact point, 1896-1962. Points for many 

years omitted to avoid congestion. Adapted from Yevdjevich (1961, 

fig. 6).

The depletions increased rapidly for a few years after 

1963 because of the increased evaporation from reservoirs, and they may increase gradually for an indefinite 

period because of increasing water use. Future depletions probably will not correlate as closely with virgin 

flows as in the past because evaporation will depend 

primarily on the aggregate storage rather than on the 

current virgin flow. The increase in depletions may be 

limited by such factors as a short growing season, relatively small acreage of arable land within the drainage 

basin, and the high cost of diverting water to areas outside the drainage basin. If the increase is not limited by 

such factors, it will be limited by provisions of the 

Colorado River Compact for release of water to the 

lower river.

It is obviously not possible to predict precisely the 

rate at which depletions above compact point will increase, nor the date when they will reach the limit 

imposed by the compact, but the following estimates by 

the U.S. Bureau of Reclamation (1965, p. 236) are illustrative of present forecasts:

Estimated depletion, 

Year in acre-feet

1975 ______________________ 4, 220,000 

1990 ______________________ 5,100,000 

2000 ______________________ 5,430, 000 

2030 ______________________ 5, 800, 000

VIRGIN FLOW, 1896-1966

The U.S. Bureau of Reclamation and the Upper Colorado River Commission have computed the virgin flow 1 

of the Colorado River at compact point by adding the 

previously described depletions to the measured or estimated streamflow for the period 1896-1966. Prior to 

1963, the effects of storage above compact point were 

relatively small, the average depletion was less than 

13 percent of the actual flow, and annual depletions 

seldom exceeded 20 percent of the actual flaw. Consequently, the computed virgin flows are only slightly less 

reliable than the corresponding figures of actual flow. As 

future depletions increase, the need for accurate determination of depletions will increase.

Both actual and virgin annual flows are shown 

graphically in figure 6; they are listed in "Appendix" 

(table 6) and are summarized in table 1. One of the 

most notable characteristics of this record is that mean 

annual flows for periods of about 30 years (1903-32 and 

1931-64) differ.by as much as 4,400,000 acre-feet, or 30 

percent of the 71-year mean flow.

As the amount of water in storage at any time 

depends on the flow during preceding years, progres1 Although the Commission has used these figures, it has not accepted 

any figures of virgin flow as official.
D14 WATER RESOURCES OF LOWER COLORADO RIVER-SALTON SEA AREA

O 15 -

WATER YEARS

Annual flow of the Colorado River at compact point, 1896-1966. A new regime for the actual flow began with the closure of Glen Canyon

Dam in 1963.

sive averages of annual flows for periods of 5 or 10 

years are useful indicators of water-supply conditions. 

The 10-year average is particularly important at compact point because of the provision in the Colorado 

River Compact referring to the aggregate flow in any 

10-year period. Figure 7 shows the progressive 10-year 

average, and also the progressive change in the average 

for the period of record beginning in 1896.

PROBABLE FUTURE VIRGIN FLOW

The principal objective of computing virgin flows 

at compact point is information regarding future flow, 

which is required for most effective planning and operation of the river-control system. Reliable forecasts, the 

most useful type of information, have been limited to 

periods of a year or less and have required current data 

such as the water content of the snowpack in early 

spring. In the absence of long-term forecasts, the most 

useful information concerns the probable magnitudes 

of future multiyear means of the virgin flow.

Conventional methods of probability analysis are 

readily applicable to the annual virgin flows of the 

Colorado River. The cumulative frequency plot in figure 8 indicates only moderate scatter about the straight 

line representing the normal distribution; hence, the 

assumption that annual flows are normally distributed 

about the mean is well supported. The only other 

assumption involved in the application of statistical 

principles to annual flows concerns the true long-term 

mean. In probability theory this true mean is the mean 

for a period of infinite length. In hydrologic studies, 

however, the true mean generally is assumed to be the 

mean for a period of only a few centuries which does 

not reflect the major changes of climate and runoff that 

have occurred during periods of thousands of years.

Statistical analysis of multiyear means involves 

greater uncertainly because annual flows fail to fulfill 

one criterion of a normal distribution (that each item 

is independent) when they are arranged in chronological order rather than order of magnitude as in figure 8.

The record of virgin flows at compact point exhibits 

a tendency for high flows to persist during some periods 

and for low flows to persist during others. Some arrays 

of random numbers exhibit the same tendency, however, 

and a persistence effect is not considered real unless
LOWER COLORADO RIVER WATER SUPPLY- ITS MAGNITUDE AND DISTRIBUTION D15

20

18

16

3:14

3

z 

z

12

10

Progressive average for period 

of record, beginning in 1896

10-year progressive average plotted 

at last year of 10-year period

CM CO ^1 

0* 0* 0*

WATER YEARS 

FIGURE 7. Progressive averages of annual virgin flow at compact point.

the tendency for such grouping is greater in the annual 

virgin flows than is expected in a random array. Hence, 

evaluation of a persistence effect must be made as a probability rather than a certainty.

A persistence effect in virgin flows may be a natural 

result of similar persistence in annual or winter totals 

of precipitation in the upper Colorado Eiver basin. 

Moreover, the lag between precipitation and runoff 

resulting from the natural storage capacity of the 

drainage basin would cause persistence in virgin flows 

even though the distribution of precipitation were random. Multiyear means of flows that are affected by persistence are more variable than corresponding unaffected means. The hydrologic literature exhibits a wide 

range of opinion on the nature and magnitude of persistence in both precipitation and runoff, and available* 

records are not long enough to assure the validity of any 

particular assumption. Because of these uncertainties, 

probability statements derived from multiyear means 

of virgin flow should be considered useful approximations rather than the equivalent of conventional probability statements.

Leopold (1959) presented a semiempirical probability analysis in which he computed the variability of 

multiyear means from records for many streams in the 

United States and Europe. His study indicates that 

multiyear means of virgin flow of Colorado River at 

compact point are much more variable than similar 

means for a random array. The results are not conclusive, however, because of the small number of independent multiyear means in each record (for example, 

there are only three independent 20-year means in the 

61-year record he used for compact point).

Additional information was gained from an intensive 

statistical study of precipitation and runoff in the 

upper Colorado River basin (Brittan, 1961; Julian, 

1961; Yevdjevich, 1961). Julian concluded that winter 

precipitation totals probably exhibit no persistence 

effect. Yevdjevich concluded that the persistence effect 

in annual streamflow data for 14 small drainage basins 

in or near the upper Colorado River basin is relatively 

small. He concluded also that the water in natural storage at the end of a year would significantly influence 

the flow in only one succeeding year.
D16 WATER RESOURCES OF LOWER COLORADO RIVER-SALTON SEA AREA

99 98

PROBABILITY, IN PERCENT, OF ANNUAL FLOW GREATER THAN INDICATED 

90 80 70 60 50 40 30 20 10

10 20 30 40 50 60 70 80 90 

PROBABILITY, IN PERCENT, OF ANNUAL FLOW LESS THAN INDICATED

95 98 99

FIGURE 8. Cumulative frequency diagram of annual virgin flow at compact point, 1896-1964. The dots represent annual 

flows; the straight line represents the normal distribution of items with the same mean and standard deviation as those 

computed from the annual flows.

On the basis of these and perhaps other similar 

studies, several investigators have assumed that the 

virgin flows can be represented by a mathematical model 

implying that a particular annual flow equals a random 

component plus the preceding annual flow multiplied 

by the first-order serial correlation coefficient. If the assumed model is a valid representation of the annual 

flows, this coefficient is a measure of the persistence

effect. Unfortunately, however, the first-order serialcorrelation coefficient computed from available streamflow records is a very imprecise estimate of the true 

(long-term) coefficient. Using calculated or estimated 

coefficients, Julian (1961), Brittan (1961), and others 

have found that such autoregressive or Markov models 

produce fair representations of annual streamflow 

sequences.
LOWER COLORADO RIVER WATER SUPPLY ITS MAGNITUDE AND DISTRIBUTION D17

N. O. Matalas (written commun. 1965) of the Geological Survey used a Markov model with a coefficient 

of 0.20 (pratically the same as his calculated value, 

0,206) to make a probability analysis of the virgin flows 

at compact point for 1896-1964. With this coefficient he 

calculated that the 69 serially-correlated flows were 

equivalent to only 44 uncorrelated (independent) items 

in defining confidence limits for the mean. Table 2 

shows the resulting confidence limits for multiyear 

means at various levels of probability. Limits for 30- 

year means were computed by the author in the same 

manner as Matalas computed other limits. The table 

indicates an 80-percent chance, for example, that a future 20-year mean will be greater than 13,200,000 acrefeet and less than 16,500,000 acre-feet.

TABLE 2. Confidence limits for multiyear means of virgin flow 

at compact point

Length of period

10 years ____ _ _ _ ___ .__ _ _

20 years. ___ _ _____ _____

30 years. _ __ ______

Long term_ ______ _ _____

Probability, 

in percent

______ 80

95 

99 

______ 80

95 

99 

______ 80

95 

99 

______ 80

95 

99

Confidence 

limits, in 

millions of 

acre-feet

12. 0 -17. 8

9. 82-19. 9 

6. 95-22. 8 

13. 2 -16. 5

12. 2 -17. 5 

11. 1 -18. 6 

13. 5 -16. 3

12. 7 -17. 1 

11. 9 -17. 9 

14. 0 -15. 8

13. 5 -16. 2 

13. 1 -16. 7

PROBABLE FUTURE REGULATED WATER SUPPLY

Since 1963 the water supply, represented by the previously described virgin flows at compact point, has been 

modified by the effects of storage in major reservoirs. 

A total capacity of 25 million acre-feet of which 20 

million are in Lake Powell and the remainder in other 

reservoirs upstream is considered available for longterm regulation of the river at compact point (Mosk, 

1959).

The potential effects of such storage are conveniently 

illustrated by comparing cumulative virgin flows with 

cumulative draft from that flow (the sum of all mancaused depletions plus the release to the lower river). 

As such accumulations tend to be very large, more convenient results for graphical analysis are obtained by 

cumulating the departure from a convenient value near 

the mean.

The irregular graph in figure 9 represents the cumulative departure from 15 million acre-feet of annual virgin

flows for the period October 1, 1895, to September 30, 

1966. The upward trend for 1903-29 indicates annual 

flows generally exceeding 15 million acre-feet and the 

downward trend after 1930 indicates flows less than that 

amount.

Figure 9 demonstrates that during the period 1903- 

29 the flow in excess of 15 million acre-feet per year was 

more than sufficient to fill all presently existing reservoirs in the Colorado Kiver System above Davis Dam. 

With a hypothetical annual withdrawal of 15 million 

acre-feet (including reservoir evaporation), the surplus 

would have reached 60 million acre-feet by the end of 

1922 and 74 million acre-feet by 1929. Following 1929, 

flows have been predominately below normal; the average for the 34-year period 1931-64 was 12,900,000 acrefeet. Assuming that the effective storage capacity of 25 

million acre-feet above compact point was full in 1930, 

a uniform annual draft of 13,700,000 acre-feet (as 

shown by the inclined line in fig. 9) theoretically could 

have been maintained during the period 1930-66. The 

reservoirs would have been full in 1952 and empty in 

1964.

Although techniques similar to those illustrated by 

figure 9 have long been standard for analysis of storage 

requirements or effects, the validity of the results 

depends on the sequential occurrence of historical flows. 

Failure to include an estimate of the probability of 

future deficiencies is a critical weakness. To obtain more 

meaningful evaluations, increasing attention is being 

given to application of probability theory to storage 

analyses. Such applications are hampered by the previously described uncertainty regarding effects of persistence in the annual flows an uncertainty that lessens, 

but does not destroy, the usefulness of the results.

In a general study of reservoir storage, Hardison 

(1966) developed some draft-storage relations that are 

applicable to the Colorado Kiver near Lakes Powell 

and Mead. Starting with the assumption of independent (uncorrelated) annual flows, he developed general 

relations of uniform annual draft to storage capacity 

and streamflow variability for each of several probabilities of deficiency and for each of three distributions 

that commonly apply to annual flows (fig. 10). Each 

of the three variables in these relations is expressed 

as a dimensionless ratio draft and storage as ratios 

to the mean annual flow, and variability as an index 

that differs with the type of distribution. The storage 

capacity considered here is the carryover capacity required to smooth out annual fluctuations; it does not 

include storage required to smooth out seasonal 

fluctuations.
D18

70 r

WATER RESOURCES OF LOWER COLORADO RIVER-SALTON SEA AREA

WATER YEARS

FIGURE 9. Graphical storage analysis of the virgin flow of the Colorado River at compact point, 1895-1966. The irregular graph represents the 

cumulative departure of annual virgin flows from 15 million acre-feet. The inclined line represents a uniform annual draft of 13,700,000 acrefeet.

DC Z

21 

CO

0.1 0.2 0.3 0.4 

COEFFICIENT OF VARIATION OF ANNUAL FLOWS

0.5

To apply these dimensionless relations to the Colorado Eiver it is necessary to select relations for the 

proper distribution, which was shown to be normal 

(fig. 8), and a proper index of variability. For normal 

distributions this index is the coefficient of variation 

(ratio of the standard deviation to the mean). In his 

probability analysis of virgin flows, N. C. Matalas used 

14,878,000 acre-feet for the mean and 4,405,000 acrefeet for the standard deviation; the corresponding coefficient of variation is 0.30. For this coefficient and a

FIGURE 10. Dimensionless draft-storage-variability relations. The 

family of curves represents uniform annual draft, in percent of 

mean annual runoff; carryover storage capacity is indicated as a 

ratio to mean annual runoff; and streamflow variability is represented 

by the coefficient of variation of annual flows. This diagram is for a 

2-percent chance of deficiency and for normally distributed, independent annual flows. Similar diagrams apply for other chances of 

deficiency and other distributions. (After Hardison, 1966.)
LOWER COLORADO RIVER WATER SUPPLY ITS MAGNITUDE AND DISTRIBUTION D19

specific level of probability, the relation curves show 

unique values of draft and storage ratios. Conversion of 

these ratios to annual amounts of draft and storage provided the data to define the solid curves in figure 11, 

which therefore would represent the relations of uniform annual draft to carry-over storage capacity applicable to the virgin flow of Colorado River if the annual 

flows were independent.

10 20 30 40 

STORAGE CAPACITY, IN MILLIONS OF ACRE-FEET

50

FIGURE 11. Relations of uniform annual draft to carry-over storage 

capacity for virgin flow of the Colorado River near compact point. 

The solid curves represent relations for independent annual flows 

and for 10-, 5-, and 2-percent chance of deficiency (derived from 

Hardison's dimensionless ratios). The dashed curves represent approximate relations with streamflow persistence (draft from solid 

curves reduced by 6 percent of mean annual flow). The vertical lines 

represent the active storage capacity of Lake Powell and the combined capacity of Lakes Powell and Mead.

Hardison also studied the effect of serial correlation 

of annual flows, which he considered to be a measure 

of the persistence effect. He concluded that, for the 

flow at 180 stream-gaging stations in the United States 

with an average serial-correlation coefficient of 0.17, the 

serial correlation would reduce the draft corresponding to a specific storage capacity by about 5 percent 

of the mean annual flow. If this conclusion is valid, 

the reduction corresponding to the serial-correlation 

coefficient of 0.20, used by Matalas in the analysis 

of virgin flows, is about 6 percent.2 Thus, the dashed 

curves in figure 11, representing approximate relations 

with persistence effect, were derived by lowering the 

solid curves 893,000 acre-feet.

Figure 11 illustrates the well-known principle that 

as storage capacity available for regulation of flow at 

a particular point increases each succeeding increment

2 In a general appraisal of storage requirements in the United States 

(Lof and Hardison, 1,966), Hardison used a reduction of 3 percent 

rather than the 6 percent used herein or the 5 percent he considered 

to be the average. The same correction was applied for all streams and 

the lower value was selected to avoid overcorrection where the persistence effect is small.

of storage is accompanied by a smaller increment of 

the allowable draft. This is true even when evaporation 

from reservoirs is included in the draft, as in figure 

11. The corresponding increments of usable draft (withdrawals in surface channels or pipes) decrease even 

more rapidly because evaporation losses tend to increase with increasing capacity.

The capacity available for carryover storage is somewhat less than the 25 million acre-feet used in figure 9 

because of the requirements for seasonal storage. Hardison's data (Lof and Hardison, 1966, table 7) indicate 

that the seasonal requirement for 2-percent chance of 

deficiency is less than 5 million acre-feet, which is less 

than the capacity of reservoirs above Lake Powell. Assuming the active capacity of Lake Powell (20,900,000 

acre-ft) is available for carryover storage, figure 11 

suggests that the regulated water supply from the upper 

Colorado River basin seldom will be less than 13 million 

acre-feet and will exceed 14 milion acre-feet most of 

the time.

As previously described, the distribution of this regulated water supply from the upper Colorado River 

system (which should not be confused with that from 

the entire Colorado River system) to the upper and 

lower service areas depends on legal considerations, the 

existence of facilities in the upper service area to enable 

beneficial use of its share of the water, and the magnitude of the regulated supply. For example, if the annual 

man-caused depletions above compact point should 

average 5 million acre-feet (about double those prevailing about 1960) when sufficient water is available, 

a regulated annual supply of 14 million acre-feet would 

provide 9 million acre-feet at compact point. Flow 

would be limited to the legal minimum, which conflicting claims place at either 7,500,000 or 8,250,000 acrefeet, whenever the regulated annual supply is equal to 

or less than either 12,500,000 or 13,250,000 acre-feet, 

respectively. Similarly, if these annual depletions above 

compact point should reach the 7,5003 000 acre-feet 

specified in the Colorado River Compact (article III, 

paragraph a, see "Appendix"), the flow at compact point 

would be limited to the legal minimum except during 

wet periods when the total supply (regulated and unregulated) exceeds either 15,000,000 or 15,750,000 

acre-feet.

COLORADO RIVER BETWEEN COMPACT POINT AND 

DAVIS DAM

Between compact point and Davis Dam the flow of 

the Colorado River is modified by highly variable inflows, evaporation from the river and reservoirs, diversions from Lake Mead, and storage in Lakes Mead and

321-230 O 68
D20 WATER RESOURCES OF LOWER COLORADO RIVER-SALTON SEA AREA

Mohave. Since 1935 the modifications have been dominated by the effects of man's activities rather than by 

natural runoff and water loss. Because the effects of 

man's activities change markedly, analysis of long-term 

records of flow in the lower river can add little to the 

knowledge of future streamflow characteristics.

A more fruitful approach to the prediction of future 

water supply is the determination of average gains or 

losses between compact point and the site for which information is desired. The average annual inflow to Lake 

Mead can be closely approximated by adding a relatively small increment to the corresponding flow at compact point, and the average annual flow at Davis Dam 

can be similarly approximated by subtracting a relatively small net loss from the corresponding flow at 

compact point and adjusting the result for the effects of 

change in storage in reservoirs below compact point.

GAINS AND LOSSES

Average gains and losses for various reaches between 

compact point and Davis Dam are determined from 

streamflow records for Colorado River and tributaries 

and from records of diversion and surface storage. (See 

"Appendix," tables 7-9,11.)

Gaging stations have been maintained on Colorado 

River near Grand Canyon, Ariz. (87 miles downstream 

from compact point), since 1922, below Hoover Dam 

since 1933, and. below Davis Dam since 1949. Gains and 

losses in streamflow between these stations are shown in 

table 3. All figures in this table are based on calendar 

years rather than the water years used in the preceding 

analyses of the flow at compact point. The period 1935- 

49, following closure of Hoover Dam but prior to 

closure of Davis Dam, includes the period of filling of 

Lake Mead. Adjustments are made for surface storage 

only; bank storage, although believed to be significant, 

has not been determined with sufficient reliability for 

use in this study. Both Lake Mead and Lake Mohave

TABLE 3. Gains and losses between compact point, and Davis 

Dam, Ariz.-Nev.

Gaging station or increment

Average annual flows and 

Drainage increments (millions of acre-ft) 

area 

(sqmi) 1935-49 1950-62 1923-62

(15 yr) (13 yr) (40 yr)

Compact point.

IncrementGrand Canyon. 

Increment.. 

Hoover Dam (adjusted) 

Hoover Dam (actual)

Increment- ___ 

Davis Dam (adjusted) 2 

Davis Dam (actual)-.-

109,500

28,300

137,800

30,000

167,800

1,500

12.39 

+.31 

12.70 

-.52 

12.18 

10.68

169,300

10.68 

+.20 

10.88

-.44 

10.44 

10.20

-.11 

10.09 

9.960

11.96 

+.31 

12.77

1 Adjusted for change in contents of Lake Mead (storage began in 1935).

2 Adjusted for change in contents of Lake Mohave (storage began in 1950).

(above Davis Dam) were in existence during the period 

1950-62, but storage in Lake Powell (above Glen Canyon Dam) did not begin until 1963. Regulation in Lake 

Powell may influence channel losses between Glen Canyon Dam and Lake Mead.

The average annual net losses between compact point 

and Hoover Dam were 210,000 acre-feet during 1935-49 

and 240,000 acre-feet during 1950-62 (obtained by combining increments in table 3). Since construction of 

Davis Dam, the additional loss between Hoover and 

Davis Dams has been 110,000 acre-feet. Hence, for runoff conditions similar to those of 1935-62, the net loss 

from compact point to Davis Dam would be about 

335,000 acre-feet.

Future losses in this reach will be affected by variations in runoff from tributary areas and consumptive 

use of water within those areas. Higher runoff during 

wet periods will tend to decrease the losses, but increasing use of water will tend to increase them. The local 

use of tributary flows has been increasing and is expected to continue increasing for many years. Diversions to Nevada from the Colorado River or Lake Mead 

began in 1932 and gradually increased to 20,000 acrefeet per year in 1955. These diversions may eventually 

equal Nevada's basic allotment of 300,000 acre-feet per 

year. Thus, losses during long relatively dry periods 

may eventually be more than double present losses.

Satisfactory accuracy of the increments in table 3 

is indicated by comparison of each increment with other 

increments and with independent estimates based on 

streamflow records for tributaries and computed evaporation losses.

The Little Colorado River drains approximately 95 

percent of the area between compact point and Grand 

Canyon and contributes nearly 100 percent of the inflow. This river has been measured since 1925 either at 

Grand Falls (96 miles upstream from the mouth) or 

near Cameron, Ariz. (45.4 miles upstream from the 

mouth), and at both places simultaneously for more 

than 8 years. During the periods of simultaneous records, the flow near Cameron exceeded that at Grand 

Falls by about 6 percent. Consequently, annual flows 

near Cameron prior to the period of record were estimated as 106 percent of those measured at Grand Falls. 

Furthermore, occasional measurements of Blue Springs, 

in the canyon of the Little Colorado River below the 

Cameron gaging station, indicate that the flow of the 

river at its mouth exceeds that near Cameron by a nearly 

constant amount of 220 cubic feet per second (159,000 

acre-ft per yr).

Annual contributions to the Colorado River determined in this manner average 350,000 acre-feet and
LOWER COLORADO RIVER WATER SUPPLY ITS MAGNITUDE AND DISTRIBUTION D21

range from 190,000 to 780,000 acre-feet. The average 

annual evaporation loss between compact point and 

Grand Canyon is about 27,000 acre-feet, estimated on 

the basis of data presented by Meyers (1962, table 4); 

hence, the corresponding net gain is 320,000 acre-feet, 

which is close to the 310,000 acre-feet shown in table 3 

for 1923-62. Similar computations indicate a net gain 

of 340,000 acre-feet during 1935-49 (compared with 

310,000 in table 3) and 260,000 acre-feet during 1950- 

62 (compared with 200,000 in table 3).

In the reach between Grand Canyon and Hoover 

Dam, the loss generally exceeds the inflow, which is 

only partly measured. The gross annual loss during 

1950-62 was about 890,000 acre-feet, which included 

837,000 acre-feet evaporated from Lake Mead (measured by either energy-budget or mass-transfer method, 

March 1952-December 1962), 37,000 acre-feet evaporated from the river above Lake Mead (based on data 

presented by Meyers, 1962) and 17,000 acre-feet 

diverted from the lake for use in Nevada. If the net 

loss of 440,000 acre-feet (table 3) is subtracted from 

the gross loss an average annual inflow (including 

precipitation on the water surface) of 450,000 acrefeet during 1950-62 is indicated. If the same gross 

loss occurred during 1935-49, the corresponding inflow 

was about 370,000 acre-feet.

Streamflow records for Bright Angel Creek, the Virgin Kiver, and Las Vegas Wash, and occasional measurements of large springs feeding Tapeats and Havasu 

Creeks in the Grand Canyon together account for 

about 250,000 acre-feet of inflow between Grand Canyon and Hoover Dam, and precipitation on the water 

surface accounts for about 65,000 acre-feet. The balance 

of the computed inflow may reasonably be accounted 

for by unmeasured inflow.

EFFECTS OF STORAGE BELOW COMPACT POINT

Lake Mead enabled virtually complete regulation of 

the Colorado River at Hoover Dam during the relatively dry period from the closure of the dam in 1935 

until 1963. Smaller reservoirs below Hoover Dam reregulate the fluctuating releases associated with power 

generation and aid delivery of water as needed in both 

the United States and Mexico. Since the construction 

of large reservoirs above compact point, much of the 

primary river regulation occurs there, and a substantial 

part of the capacity of Lake Mead has become available 

for additional regulation. Although this extra capacity 

may not be needed for some fairly long periods, the 

streamflow has been sufficient at times to fill all reservoirs (fig. 9).

Since only minor amounts of inflow occur between 

Glen Canyon and Hoover Dams, it is appropriate to 

consider the effects of the combined capacity of Lakes 

Powell and Mead on the uniform annual draft from 

virgin flow and to compare these with the effect of Lake 

Powell alone. For a 2-percent chance of deficiency, 

figure 11 indicates an increase in draft of about 

800,000 acre-feet when Lake Mead is included. For a 

5-percent chance of deficiency, the corresponding increase is about 600,000 acre-feet. As all drafts involved 

in these computations include evaporation, it is necessary to subtract the evaporation from Lake Mead to 

find the net effect on usable draft. Evaporation consumed 806,000 acre-feet per year during 1952-66 and 

may consume a somewhat smaller amount if lake levels 

are lower during future periods.

The net effect on the water supply of storage in Lake 

Mead will be a substantial increase in allowable draft 

during long wet periods; but if Lake Powell is used 

to its full potential, storage in Lake Mead will not appreciably increase the firm supply. In practice, however, the function of river regulation probably will be 

shared by all major reservoirs to maintain maximum 

effectiveness for some of their many other uses.

COLORADO RIVER AND TRIBUTARIES BELOW 

DA VIS DAM

Below Davis Dam the Colorado Eiver is primarily a 

part of a vast distribution system, which is discussed in 

later sections. Aside from numerous desert washes that 

rarely contribute appreciable quantities of water to the 

Colorado Eiver and channels that convey return flows 

from irrigation diversions, there are only two tributaries 

below Davis Dam, the Bill Williams and Gila Eivers.

BILL WILLIAMS RIVER

The Bill Williams Eiver drains about 5,200 square 

miles in west-central Arizona and flows into Havasu 

Lake above Parker Dam. Its drainage basin is sparsely 

populated, and only 9,100 acres were irrigated in 1963, 

chiefly by pumping ground water. A considerable part 

of the runoff occurs during infrequent floods; some of 

the runoff cannot be adequately controlled by Lake 

Havasu under normal operating conditions but will be 

controlled by a reservoir (construction began in 1965) 

on the Bill Williams Eiver near Alamo, about 34 miles 

above Lake Havasu.

The flow of the Bill Williams Eiver has been measured 

at Planet, about 6 miles above Lake Havasu, from 1929 

to 1945 and near Alamo since 1939 (table 8). The records 

of annual flows at the two sites correlate well, and dur-
D22 WATER RESOURCES OF LOWER COLORADO RIVER-SALTON SEA AREA

ing the period of simultaneous records the average flow 

at Planet was about 84 percent of the flow near Alamo. 

On the basis of records at both sites and this relation, 

the average annual flow at Planet for 1929-62 is estimated to be about 70,000 acre-feet. The annual flows 

range from negligible amounts in many years to 400,000 

acre-feet in 1941. A bar graph of the annual flows is 

shown in figure 12.

GILA RIVER

The Gila Kiver, which is the largest tributary to the 

Colorado River below compact point, drains 57,950 

square miles, chiefly in central and southern Arizona but 

including about 5,600 in New Mexico and about 1,100 

in Sonora, Mexico. Its drainage basin includes the major 

cities of Phoenix and Tucson, Ariz., more than 100 

smaller cities, and about a million acres of farm lands 

irrigated with water from the Gila River system and 

the aquifiers underlying the basin. For many years the 

annual consumptive use of water in the basin has greatly 

exceeded the average annual runoff. The high rate of

consumptive use has been sustained by annual withdrawals of ground water several times as great as the 

annual replenishment.

A bar graph in figure 12 represents the annual flow of 

the Gila Eiver near Dome (table 8), in the gap where 

the Gila River enters the lower Colorado River valley. 

This flow does not include return flows from irrigation 

in North and South Gila Valleys or the flow in the Wellton-Mohawk Main Outlet drain, which was constructed 

in 1961 to convey the effluent from drainage wells in the 

Well ton-Mohawk area to the Colorado River. The graph 

illustrates both the extreme variability of the flow and 

the decline caused by development of irrigation within 

the basin. The only flow between 1941 and the wet winter 

of 1965-66 was surface drainage from irrigation in the 

Wellton-Mohawk area or runoff from occasion local 

storms.

Although average annual water use exceeds the average streamflow and the major irrigation storage reservoirs (combined capacity, nearly 3,500,000 acre-ft.) 

seldom fill completely, a recurrence of runoff similar to

I

Bill Williams River 

at Planet, Ariz.

I.

Gila River near Dome, Ariz.

I ul_j . I CM f?> 3- m 

o^ o^ o^ o^

CALENDAR YEARS 

FIGURE! 12. Annual flows of the Bill Williams and Gila Rivers.
LOWER COLORADO RIVER WATER SUPPLY ITS MAGNITUDE AND DISTRIBUTION D23

that of 1916 (i,G65,000 acre-ft.) would almost certainly 

cause considerable spill from several reservoirs. Painted 

Rock reservoir, 126 miles upstream from the mouth, provides nearly 2,500,000 acre-feet of additional capacity 

for control of floods that originate above the dam. 

Release of water from this reservoir or infrequent uncontrolled floods from the 7,300-square-mile drainage 

area downstream can cause appreciable flow into the 

Colorado River at times.

As the confluence of the Gila and Colorado Rivers is 

below all storage reservoirs and below all but one of 

the major diversions (Alamo Canal), there is little opportunity to use any flood flow that may occur in the 

Gila. Thus, the contribution of the Gila River to the 

usable water supply in the Colorado River must be 

considered negligible. The infrequent controlled releases from Painted Rock reservoir may help to supply

the current requirements of Mexico if the resulting flows 

at the mouth of the Gila River can be coordinated with 

releases from the storage reservoirs on the Colorado 

River.

COLORADO RIVER BELOW ALL MAJOR DIVERSIONS

A synthesized record of the flow of the Colorado River 

below all major diversions (fig. 13) illustrates the downward trend of the residual flow, caused chiefly by an 

increasing use of water from the Colorado River. The 

residual flows during 1935-39 were unusually low 

largely because of the initial filling of Lake Mead. The 

low flows during 1959-62 indicate a nearly complete 

utilization of the Colorado River; consequently, future 

increases in beneficial use of water from the basin may 

depend largely on increasing the efficiency of use.

The annual flows shown in figure 13 are about the

25

20

15

10

I

CALENDAR YEARS 

FIGURE 13. Annual flow of the Colorado River below all major diversions.
D24 WATER RESOURCES OP LOWER COLORADO RIVER-SALTON SEA AREA

same as the annual flows into the Gulf of California, 

except those for periods of very low flow when small 

diversions and return flows below Alamo Canal may 

have caused appreciable differences between the respective flows. These residual flows were obtained by subtracting the flow of Alamo Canal from the flow of the 

Colorado Eiver above the canal. The site of the diversion has varied but generally has been within a few 

miles of the present site, 1.1 miles downstream from the 

northerly international (California-Baja California) 

boundary (fig. 3).

Diversion through Alamo Canal began in 1901, but 

continuous records of the diversion (table 10) did not 

begin until 1908, following a period of about 2 years of 

uncontrolled diversion into the Salton Sea. Since 1951, 

a record of the flow above the canal at the northerly 

boundary (table 7) has been maintained by the International Boundary and Water Commission. An equivalent record for 1934-50, computed by adding flows in 

two drains and two wasteways (constructed after 1911) 

to the flows of the Colorado Eiver at Yuma, was published for "Colorado Eiver and Pilot Knob wasteway 

at Eockwood Gate, Calif." (U.S. Geol. Survey, 1954). 

A similar record for 1912-33, compiled for this report, 

required the estimation of small return flows for 12 

years. Prior to 1912, annual flows at Yuma were practically the same as those at the northerly boundary.

DISTRIBUTION OF COLORADO RIVER WATER

Irrigation has been a major goal in the development 

of the lower Colorado Eiver and is still the dominant 

influence on distribution of the water. Other uses are 

increasing, however, and large quantities of water are 

lost by evaporation and nonbeneficial transpiration.

Diversions from the Colorado Eiver below Davis 

Dam serve areas adjoining or near the river in Arizona 

and much of the densely populated area in southern 

California. A large part of the water diverted to areas 

within the Colorado Eiver basin returns to the river 

and can be diverted again, but only a negligible part of 

the water diverted for use outside the basin returns to 

the river.

The net diverson (difference between gross diversion 

and return flow in surface channels) commonly is used 

as an index of the streamflow depletion or consumptive 

use of water associated with a particular diversion. Although such net diversion is a satisfactory index of 

actual consumptive use under favorable circumstances, 

it is a very unreliable index when relatively large quantities of water enter or leave the particular area as 

ground-water seepage or contribute to changes in 

ground-water storage within the area. Furthermore,

there are few adequate records of return flows prior to 

1960 because there was no scarcity of water for then 

current uses.

GROSS DIVERSIONS

Figure 14 illustrates the progressive increase of diversions from the lower Colorado Eiver. It is necessarily 

based on gross diversions because of the scarcity of return-flow data needed to determine net diversions. The 

following paragraphs describe these diversions and their 

relation to the total water supply of the respective areas.

The only major diversion between Hoover Dam and 

Parker Dam is the diversion from Lake Havasu through 

the Colorado Eiver aqueduct to the south coastal basins 

of California. This diversion, which began in 1939, 

supplements other water supplies from both local and 

distant sources.

All water diverted between Parker Dam and Imperial Dam (except for numerous small diversions by 

pumps, chiefly in Cibola Valley) is delivered to Parker 

and Palo Verde Valleys. Diversions to Parker Valley 

began in 1870, but there are no records for years prior to 

1915. Annual diversions were less than 40,000 acre-feet 

per year until after the completion of Headgate Eock 

Dam in 1942, when they began to increase rapidly. Diversions to Palo Verde Valley began before 1900, but 

there are no records for years prior to 1922. These diversions are the only water supplies for the respective 

valleys except for the local ground water, which is 

affected by seepage to or from the river and by irrigation 

of crops with river water.

Diversions from the Colorado Eiver to the Yuma area 

began about 1900 and have been made by several means, 

including gravity diversion at both ends of Imperial 

and Laguna Dams, temporary gravity diversions, and 

pumping. Diversions to the Wellton-Mohawk area, in the 

lower part of the Gila Eiver valley, began in 1952. 

Eecords on which approximate total diversions to the 

Yuma and Wellton-Mohawk areas can be based began 

in 1908. These totals are gross diversions for irrigation; 

they do not include water returned to the river through 

the Yuma Main Canal wasteway or Pilot Knob powerplant and wasteway, most of which was diverted for 

power generation. These diversions, like those to the 

Parker and Palo Verde Valleys, are the only water 

supplies for the Yuma and Wellton-Mohawk areas except the local ground-water supply, which is affected by 

seepage to or from the Colorado and Gila Eivers and 

by irrigation of crops with river water.

Diversions to Imperial and Mexicali Valleys began 

in 1901; continuous records began in 1908. Prior to completion of the All-American Canal in 1940, water was
LOWER COLORADO RIVER WATER SUPPLY ITS MAGNITUDE AND DISTRIBUTION D25

Diversion between Davis and Parker 

Dams via Colorado River aqueduct

Diversions to tracts within the 

Colorado River basin between 

Parker Dam and Mexico

ker and Palo Verde 

Valleys

Diversions to the Salton Sea basin 

and the delta in California and Mexico

Alamo Canal

CALENDAR YEARS 

FIGURE 14. Principal diversions from the Colorado River below Davis Dam, 1908 63.
D26 WATER RESOURCES OF LOWER COLORADO RIVER-SALTON SEA AREA

diverted through the Alamo (Imperial) Canal for use 

on both sides of the international boundary. During 

1916-21, supplemental diversions were made from a 

distributary of the Colorado Eiver at Volcano Lake, 

near the western edge of the delta in Baja California. 

The rapid increases in diversions during the first half 

of this century were interrupted in the drought of 

1931-34 but were resumed after regulation of the river 

was accomplished by closure of Hoover Dam in 1935.

Since 1941 the Ail-American Canal has supplied all 

water used in Imperial Valley in California, and since 

1948 it has also supplied water to the lower part of 

Coachella Valley. The graph for the All-American 

Canal (fig. 14) shows the flow below Pilot Knob powerplant and wasteway; therefore, it does not include water 

diverted through the All-American Canal to the Yuma 

area, water returned to the river at or above Pilot Knob, 

or water lost by evaporation and seepage above Pilot 

Knob. The graph for Alamo Canal after 1941 shows the 

principal diversion to Mexico but does not include small 

diversions from the river below the canal or return flow 

from Yuma Valley used for irrigation near San Luis, 

Sonora.

The Colorado River and the related ground-water 

bodies are the only supplies available in Imperial and 

Mexicali Valleys. Wells in the central part of Imperial 

Valley yield very little water, which is generally of poor 

quality, but usable ground-water supplies underlie parts 

of the East Mesa (fig. 4). Water is withdrawn from 

many wells in Mexicali Valley.

Ground water that originates from precipitation on 

nearby mountains is the principal supply for the upper 

part of Coachella Valley (fig. 4) and was the principal 

supply for the lower part of the valley until importation 

of Colorado River water began about 1948. The Cbachella Valley County Water District has contracted for 

delivery of additional surface water from northern California whenever such supply becomes available.

NET DIVERSIONS

The gross diversions shown in figure 14 for the Colorado River aqueduct and the All-American Canal below

Pilot Knob are good approximations of the streamflow 

depletion caused by these diversions. The gross diversion through the aqueduct generally exceeded the net 

diversion by less than 2 percent. As previously described, 

the diversions to Imperial and Coachella Valleys were 

determined for a point below Pilot Knob wasteway and 

so excluded both the return flows and the unrecovered 

losses from the canal above the wasteway. As some of 

the losses are attributable to this diversion, the streamflow depletions were slightly greater than the indicated 

diversions.

Available records indicate that return flows from 

areas adjoining the river are commonly more than half 

the gross diversions. For example, figure 15 shows the

0.4

u- 0.2

<n

z

2 o

§: 0.4

O

Parker Valley

Return flows

0.2

Diversions

Return flows /-v~\/-~\

Yuma Valley

FIGURE 15. Annual diversions and return flows for Parker Valley and 

Yuma Valley, 1930-63.
LOWER COLORADO RIVER WATER SUPPLY ITS MAGNITUDE AND DISTRIBUTION D27

annual diversions and return flows (hence, the magnitude of net diversions) for Parker and Yuma Valleys, 

for which the longest records are available. The graph 

for Parker Valley illustrates the usual absence of return 

flow when diversions are small and the progressive increase of return flow as the gross diversion increases.

Figure 16 illustrates the approximate depletion of 

the flow of the Colorado Kiver caused by use of water 

from the main stem in the States of Arizona and California and also the principal diversions to Baja California in four selected years. Losses from the river associated with the storage and conveyance of water are not 

included. Accurate determination of these depletions for 

years prior to 1960, particularly those prior to 1941, is 

impossible not only because of a scarcity of return-flow 

records but also because some canals supplied tracts in 

more than one State; nevertheless, quantities that are 

sufficiently accurate for this illustration were estimated 

on the basis or available records of diversions, return 

flows, and irrigated acreage.

The diversions in Alamo Canal for 1915 and 1930 

were prorated between California and Baja California 

in proportion to the irrigated acreage in each State. 

In 1915 about 12 percent of the acreage served by the 

canal was in Baja California, and by 1928 about 32

1915 1930 1945 1960

FIGURE 16.- -Depletion of the lower Colorado River in selected years, 

by States.

percent was in that State (Adams and others, 1930, p. 

86). The percentage for 1930 was assumed to be the same 

as that for 1928.

The bars shown (fig. 16) for Baja California represent the principal diversions to Mexico; they do not 

include the effects of return flow below Morelos Dam, 

diversions from the river below the dam in both Sonora 

and Baja California, or water crossing the ArizonaSonora boundary.

The distribution of Colorado River water in accordance with requirements of the Mexican treaty of 1944 

and the U.S. Supreme Court decree of 1964 will require 

changes in the existing distribution indicated in figure 

16 unless additional water is provided. In 1960, annual 

diversions to Baja California exceeded the guaranteed 

quantity of 1,500,000 acre-feet for Mexico, and depletions in California exceeded the basic allowance of 

4,400,000 acre-feet; but depletions in Arizona were still 

less than half the basic allowance of 2,800,000 acre-'feet.

DISTRIBUTION OF FLOW DURING 1961-63

The pattern of distribution of Colorado River water 

has been changing since the first diversions were made 

and is still changing as new water-supply and irrigation 

projects are completed or old ones altered. As flows for 

a single year may be affected by abnormal circumstances, 

and as average flows for a long period may be affected 

by excessive change of the distribution pattern within 

the period, the distribution is best represented by average flows for a period of only a few years.

Table 4 and figure 17 summarize the average annual 

flows throughout the distribution system below Davis 

Dam for the period 1961-63. The annual flows during 

the period varied within a relatively narrow range. The 

most notable differences between average flows for this 

period and those for other recent periods are: (a) 

Flow of Gila River near its mouth was markedly greater 

after 1960 because of pumping from drainage wells in 

the Wellton-Mohawk area and in South Gila Valley, 

and (b) return flow through Yuma Main Canal wasteway was markedly less after 1960.
D28 WATER RESOURCES OF LOWER COLORADO RIVER-SALTON SEA AREA

Davis Dam

TO METROPOLITAN WATER DISTRICT 

OF SOUTHERN CALIFORNIA

25

FIGURE 17. Distribution of Colorado River water below Davis Dam, lOGl-'GS. Widths of pattern indicate mean annual flows except

those less than 100,000 acre-feet. Numbers refer to items in table 4.
LOWER COLORADO RIVER WATER SUPPLY ITS MAGNITUDE AND DISTRIBUTION D29

TABLE 4. Average annual flow in the lower Colorado River system,

1961-63

COLORADO KIVEK BASIN

Acrefeet

1. Colorado River below Davis Dam, Ariz.-Nev ____________ 8,438,000

2. Colorado Eiver near Topock, Ariz......._.__.........._....... 8,221,000

3. Bill Williams River near Alamo, Ariz._______________ 19,860

4. Diversion to Metropolitan Water District of Southern California. 1,078,000

5. Colorado River below Parker Dam, Ariz.-Calif. 1 -- ...._......__ 7,128,000

6. Diversion to Parker Valley, Ariz.................................. 463,300

7. Return flow from Parker Valley, Ariz.2 ----_................... 284,900

8. Diversion to Palo Verde Valley, Calif.....__................... 941,900

9. Colorado River below Palo Verde Dam, Ariz.-Calif................... 5,871,000

10. Return flow from Palo Verde Valley, Calif.' .................... 567,700

11. Colorado River below Cibola Valley, Ariz.-.......................... 6,438,000

12. Colorado River above Imperial Dam, Ariz.-Calif..._................ 6,424,000

13. Colorado River below Imperial Dam, Ariz.-Calif____________ 507,400

14. Return flow from North Gila Valley, Ariz.4 ....._..........._. 49,900

15. Gila River near Yuma, Ariz.s..................................... 194,000

16. Return flow from South Gila Valley, Ariz.6 - ...................... 39,520

17. Colorado River at Yuma. Ariz__. _______________ ___ _ 822,600

18. Return flow through Yuma Main Canal wasteway, Calif.. ___ 220,800

19. Return flow from Reservation Division of Yuma project, Calif.'.. 51,500

20. Return flow through Pilot Knob powerplant and wasteway, Calif. 645,400

21. Colorado River at northerly international boundary.. _________ 1,772,000

22. Diversion in Alamo Canal to Mexican" Valley, Baja Calif.......... 1,525,000

23. Return flow from Yuma VaUey.Ariz.s......------.-.-............ 172,200

24. Colorado River at southerly international boundary.. ___ _____ 223,400

25. Total flow to Mexico at southerly boundary ______________ 370,400

26. Total flow to Mexico 10-.....--..............-...-.-.-..-.--..-..-..-. 1,920,000

27. Gila Gravity Main Canal at Imperial Dam, Ariz.-Calif-.............. 871,600

28. Diversion to North Gila Valley, Ariz - . . 87 330

29. Diversion to Wellton-Mohawk area, Ariz......_................. 414,600

30. Diversion to South Gila Valley, Ariz............................. 17,700

31. Diversion to Yuma Mesa, Ariz_ _____ _____________ 310,600

32. Ail-American Canal near Imperial Dam, Ariz.-Calif.._________ 5,048,000

33. Diversion to Reservation Division of Yuma project, Calif."- - __ 95,100

34. Yuma Main Canal at siphon-drop powerplant near Yuma, Ariz-. 573,700

35. Diversion to Yuma Valley, Ariz.'s..._... ._.-_.-_-_-- .___.__ 350,000

36. All-American Canal above Pilot Knob wasteway, Calif__........... 4,284,000

37. All-American Canal below Pilot Knob wasteway, Calif, (diversion to

Imperial and Coachella Valleys). ______.____________. 3,603,000

SALTON SEA BASIN, CALIF.

38. Coachella Canal at head, near Greys Well_....._.................. 529,300

39. Diversion from Coachella Canal to Imperial Valley. _______. 2,100

40. Coachella Canal below 6A check, near Niland-.__________ 380,500

41. Coachella Canal at milepost 87, near Mecca. ______ ______ 355,000

42. All-American Canal below Coachella Canal_____.__..._____ 2,966,000

43. All-American Canal above East Highline Canal u___............. 2,923,000

44. Total delivery to Imperial Valley (items 39 and 43)......-_-. .--... 2,925,000

DKAINAGB TO SALTON SEA

45. Drainage into Imperial Valley from Mexico.............._.......... 130,600

46. Inflow to Salton Sea from Imperial Valley "........................... 1,270,000

47. Inflow to Salton Sea from Coachella Valley ».__--.-- --........... 110,000

1 A decrease of 15,100 acre-feet in the contents of Lake Havasu accounts for 5,000 

acre-feet of this total.

2 Sum of flows in six channels, of which four enter the river above Palo Verde Dam 

and two enter below the dam but above the gaging station (item 9).

3 Sum of flows in 12 channels partly estimated.

4 Sum of flows in six channels three tributary to the Colorado River and three 

tributary to the Gila River.

8 Sum of flows of the Gila River near Dome, Wellton-Mokawk Main Outlet drain, 

and minor flows in two wasteways in the Gila Gravity Main Canal. It includes return 

flow from the Wellton-Mohawk area and some runoff from local storms, but does not 

include return flows from North and South Gila valleys.

8 Sum of flows in three channels 2 tributary to the Gila River and one tributary to 

the Colorado River.

7 Sum of flows in two channels.

 Includes flows from three wasteways to the Colorado River (25,170 acre-ft) and 

water that flowed or was pumped across the international boundary to canals in 

Sonora, Mexico (147,000 acre-ft).

 Sum of flows in the Colorado River and canals. (See footnote 8.)

10 Flow reaching the international boundary (items 21 and 23) was 1.944,000 acre 

feet; flow leaving the boundary (items 22 and 25) was 1,895,000 acre-feet.

11 Sum of flows in several small canals diverting from All-American and Yuma 

Main Canals. About 4,700 acre-feet of his total was diverted from Yuma Main Canal 

below siphon-drop powerplant and is included in item 34.

12 Includes diversion for the City of Yuma.

18 Sum of flows below East Highline Canal and diversions above East Highline 

check.

14 Sum of flows in the Alamo and New Rivers and about 30 other channels.

15 Sum of flows in the Whitewater River and 18 drains.

Additional information concerning the distribution of 

Colorado Kiver water can be derived from the data in 

table 4, but figures so derived must be interpreted with 

caution. For example, the difference of 14,000 acre-feet 

between items 11 and 12 is much smaller than probable 

errors of measurement involved in either item; consequently, it is not a dependable estimate of depletion between Cibola Valley and Imperial Dam. Some applications of table 4 are discussed in the following section.

WATER USE AND WATER LOSS

The use of water from the lower Colorado Eiver 

has been accompanied by large losses, some avoidable 

and others unavoidable. Although the previously described streamflow data afford little direct information 

concerning such losses or the efficiency of water use, information can be obtained from water-budget studies 

based on the streamflow data and computations or 

estimates of evaporation and consumptive use by 

vegetation.

The term "consumptive use" denotes water returned 

to the atmosphere by evaporation and transpiration 

or incorporated in vegetation or industrial products. 

Consumptive use for an irrigated tract includes evaporation from canals and bare soil and transpiration from 

areas of native vegetation that are too small to be considered separately. It should be noted, however, that 

the amount of water required for irrigation of crops in 

an arid region without impairment of the soil productivity exceeds the consumptive use. Sufficient water 

must be applied to remove excess minerals from the soil; 

also, some waste is involved in any practical method 

of applying water to the crops.

A water budget is an accounting based on the fact 

that outflow from a specific area or water body during 

a specific period is equal to the inflow plus the decrease 

(or minus the increase) in storage. The unqualified 

terms "inflow" and "outflow" generally refer to water 

entering or leaving a budget area by any means; but in 

the following budgets, precipitation is accounted for 

by subtracting it from evaporation and transpiration 

instead of entering it as an inflow item. Changes in 

storage include changes in both surface and groundwater storage where applicable. Changes in soil moisture, which must be included in a comprehensive budget 

for a land area, are ignored herein because they are 

unknown and their effects probably are negligible.

The residual required to balance a water budget is affected by the net error in all other budget terms and by 

any term omitted because it was small or unknown. 

Hence, the residual is most reliable as an estimate of 

stream depletion or consumptive use when the ratio of 

residual to probable net error is greatest.

Water budgets for several segments of the study area, 

described in the following sections, have been developed. 

As Colorado Kiver water is the primary concern of 

this report, the budget areas are limited to the river and 

to land where river water or closely related ground
D30 WATER RESOURCES OF LOWER COLORADO RIVER-SALTON SEA AREA

water is consumed. Budgets to determine conveyance 

losses from major canals are treated separately because 

these losses are reflected in budgets for the 

compassing areas.

enCONVEYANCE LOSSES FROM LARGE CANALS

The distribution of water throughout an irrigation 

system involves losses by evaporation and seepage, especially when unlined canals convey water for long distances in desert terrain. Evaporation from large unlined 

canals generally is small in relation to the seepage. 

For example, seepage from the canals listed in table 5 

is roughly 30 times the estimated evaporation.

The disposition of water that seeps from canals 

varies with location and circumstances. Seepage may 

become part of the evapotranspiration loss from the 

encompassing area, or it may become part of a local 

water supply. Thus, the seepage may influence the distribution of water within a specific area as much as it 

influences the overall water loss.

Seepage from canals near the Colorado River contributes to return flow and usually is indistinguishable 

from return flow caused by irrigation. Part of the seepage from the All-American and Coachella Canals enters 

the Salton Sea, and part of it recharges shallow 

aquifers that may contain water of either better or 

worse quality than that of the canal water.

Seepage losses vary considerably because of erosion 

of seepage channels, activities of burrowing animals, 

deposition of sediment, canal maintenance activities, 

and changes in the extent of saturated sediments 

beneath and adjacent to the canals. Seepage from some 

reaches of the All-American Canal system has shown 

a tendency to decline, probably because of changes in 

the extent of saturated sediments.

Table 5 summarizes the losses by evaporation and 

seepage from several reaches of the major canals below 

Imperial Dam. The losses were calculated from the data 

in table 4. The percentages in the last column are used 

as a basis for judging the reliability of the calculated 

losses. Thus, an error of 1 percent in the determination 

of canal flow would produce an error of less than 4 percent in the calculated loss from the upper reach of 

Coachella Canal but would produce an error of more 

than 30 percent in the calculated loss from the upper 

reach of the All-American Canal. In fact, the loss calculated for a nearly identical reach of the All-American 

Canal Imperial Dam to the gaging station above Pilot 

Knob wasteway is 100,000 acre-feet instead of the 

140,000 acre-feet shown in table 5.

TABLE 5. Water losses from major canals, 1961-63

Canal reach

Average annual loss

Length Percentage 

of reach Acre-feet of flow at 

(miles) head of 

reach

Gila Gravity Main Canal 

Imperial Dam to Yuma 

Mesa __ ___________

All-American Canal

Imperial Dam to Pilot

Pilot Knob to East High 

Line Canal 3 __._______.

Coachella Canal

Head to 6A check, near 

Niland_ __-.__--_____.

6 A check to mile post 87, 

near Mecca_ __________

21 i 41, 000

21 140,000

37 150,000

49 150,000

38 25,000

4.7

2.8 

4. 2

28

6.6

> Includes minor amounts of gate leakage or spill at two wasteways. 

2 Below Pilot knob wasteway (item 37 of table 4. 

' First major diversion to Imperial Valley.

LOWER COLORADO RIVER AREA DAVIS DAM TO MEXICO

Davis Dam to Imperial Dam. O. J. Loeltz and C. C. 

McDonald, U.S. Geological Survey (written commun., 

1967), developed water budgets for the reach extending 

from Davis Dam to Imperial Dam and for the two subreaches that meet at Parker Dam. Although the computed residuals for the subreaches are less accurate 

indicators of consumptive use than that for the longer 

reach, they are useful indicators of the distribution of 

such use. Loeltz and McDonald also computed the corresponding annual consumptive use using experimental 

data on rates of consumptive use and acreages of various crops, native vegetation, and water surface. Their 

results are summarized in the following tabulation.

[Mean annual quantities, in acre-ft, 1950-66]

Davis Dam Parker Dam Davis Dam

to Parker to Imperial to Imperial

Dam Dam Dam

Water budget

Inflow:

Measured:

Surface......_....

Unmeasured:

Surface.--.---.--... 

Subsurface__ .....

Change in storage:

Measured-.-.--_--_-._ 

Unmeasured__---....

Outflow:

Measured:

Surface....--._....

Unmeasured:

Subsurface. - 

Residual (consumptive use).

9,581,000 8,578,000

73,000

15,000

-8,000

71,000

16,000

9,581,000

144,000

31,000

-8,000

9,253,000 7,890,000

0

424,000

10,000

765,000

8,565,000

10,000

1,189,000

Consumptive use

Irrigated cropland (3.6 acre-ft per acre). 

Native vegetation.____..___... 

Water surface (6.75 acre-ft per acre)....

11,000

188,000

181,000

440,000

353,000

81,000

451,000

541,000

262,000

TotaL. 380,000 874,000 1,254,000

Average for two methods- 402,000 820,000 1,222,000
LOWER COLORADO RIVER WATER SUPPLY ITS MAGNITUDE AND DISTRIBUTION D31

All measured flows in the water budgets were derived 

from stream flow records in the same manner as items 

in table 4. Records of the flow at (above) Imperial Dam 

prior to 1961, however, were adjusted by deducting 

100,000 acre-feet per year because of unmeasured inflow 

between the dam and the station at Yuma, the record 

for which was used in compiling those records for Imperial Dam. Later records were compiled from flows 

measured at the dam.

All unmeasured flows in the budgets were estimated. 

Although these small quantities are subject to large percentage errors, the errors probably are less significant 

than the small percentage errors affecting the large 

measured quantities. Estimates of surface runoff were 

based on the analysis of runoff made by Hely (Hely and 

Peck, 1964) and records of runoff for nearby desert 

areas. The average annual rate of runoff was estimated 

to be 16 acre-feet per square mile. Unmeasured groundwater inflow was assumed to equal the net recharge to 

aquifers in the area tributary to the Colorado River 

valley, which was estimated on basis of annual precipitation by methods developed by Eakin (1961). In this 

method, annual recharge was computed as a percentage 

of annual precipitation above a base, the percentage 

increasing with annual precipitation.

The measured change in storage is the average annual 

decrease in the contents of Lake Havasu, which is equivalent to an addition to inflow or a deduction from outflow in a water budget. The unmeasured change, chiefly 

in ground-water storage, is unknown but believed to be 

negligible.

The probable reliability of the residuals for the 17- 

year period as estimates of long-term residuals could 

be determined by statistical analysis of residuals for 

annual budgets. However, for the reach from Davis 

Dam to Imperial Dam, the measured quantities in the 

17-year budget account for 86 percent of the total residual. Hence, analysis of the annual residuals computed 

using only measured quantities serves nearly as well. 

Loeltz and McDonald made such an analysis of annual 

residuals for the reach from Davis Dam to Imperial 

Dam and concluded that (a) the annual residuals probably are normally distributed; and (b) at the 95 percent 

confidence level, the computed residual (1,024,000 acreft for measured quantities) is within 69,000 acre-feet of 

the long-term residual.

The consumptive-use estimates in the lower part of 

the tabulation were derived from acreages of each type 

of water-using area and appropriate rates of use by 

each type. Data for the principal areas of cropland were 

obtained from annual crop reports of the Colorado 

River Indian Reservation and the Palo Verde Irrigation

District. Data on other cropland and native vegetation 

were obtained from an inventory of land use in 1962 

(U.S. Bureau of Reclamation, 1963). The area of water 

surface was derived from areal photographs.

The average annual rate of water use by the crops 

usually grown in these areas was estimated to be 3.6 

acre-feet per acre on the basis of studies by Blaney 

and Harris (1952) and Erie, French, and Harris 

(1965). The consumptive use by native vegatation 

above Parker Dam is from a preliminary estimate by 

the U.S. Bureau of Reclamation (1963); the use below 

Parker Dam is equal to the Bureau's preliminary estimate, 327,000 acre-feet, plus 26,000 acre-feet (estimated 

by Loeltz and McDonald, written conimun., 1967) used 

on 6,000 acres in Palo Verde valley, which was not included in the Bureau's land inventory. The net evaporation from water surfaces was derived by subtracting 

the mean annual precipitation, 5 inches (Hely and Peck, 

1964, pi. 3), from the mean annual lake evaporation, 86 

inches, determined by the U.S. Weather Bureau (1959, 

pi. 2).

Although the areas covered by various types of native 

vegetation are known only for 1962, the consumptive 

use during that year probably is close to the mean consumptive use during the budget period. The known increase of irrigated acreage has been accompanied by 

clearing of native vegetation. This tendency for reduction of native vegetation may have been at least partly 

compensated by the well-known tendency for native 

vegetation to spread and increase in density. Loeltz and 

McDonald estimated that consumptive use increased 

0.8 acre-foot per acre when land was cleared and irrigated. The net result probably was a relatively small 

increase of consumptive use during the budget period.

Considering the uncertainties involved in computation of consumptive use and the effect of probable errors 

on the water-budget residual, the results obtained by the 

two methods are in close agreement.

Imperial Dam to Mes&ico. The water-using area 

between Imperial Dam and Mexico includes several distinct units (fig. 3). For water-budget studies, however, 

a simpler division into two units with hydraulic connection only in the narrow gap at the north end of the Gila 

Mountains is more appropriate. These units are the 

Wellton-Mohawk area extending upstream from the 

gap along the Gila River, and the Yuma area along the 

Colorado River.

Because of its separation from the Colorado River 

floodplain, the Wellton-Mohawk area was not included 

in either the detailed ground-water studies by the Geological Survey or the inventory of land use by the Bureau of Reclamation. Furthermore, ground water in the
D32 WATER RESOURCES OF LOWER COLORADO RIVER-SALTON SEA AREA

area has two major sources (the Gila River and the 

Colorado River) rather than the single major source for 

most other units of the study area. The available 

information is insufficient for compilation of a reliable, 

complete water budget.

Marked changes in the hydrologic regimen of the 

Wellton-Mohawk area occurred about 1950, when 

Colorado River water began to replace the local ground 

water as the irrigation supply, and in 1961, when drainage by pumping ground water began. The following 

tabulation of measured inflows and outflow and the 

corresponding residuals illustrate some eff ects of the last 

of these changes and compares the changing regimen for 

the Wellton-Mohawk area with the more stable regimen 

for the Yuma area.

[Mean annual quantities, in acre-ft.]

WelltonMohawk area

Yuma 

area

Combined 

area

Calendar years 1957-69

Measured inflow. -__.--_-__ 332, 800

Measured outflow________ 1, 500

Residual_____________ 331, 000

8, 414, 000 8, 413, 000

7, 771, 000 7, 438, 000

643, 000 975, 000

Calendar years 1961-63

Measured inflow.__________ 414, 600

Measured outflow________ 194,000

Residual_____________ 221, 000

6, 618, 000 6, 424, 000

5, 913, 000 5, 498, 000

705, 000 926, 000

The inflow and outflow figures for 1961-63 were 

derived from table 4, and those for 1957-59 were derived 

from an unpublished compilation for that period. As 

explained in the discussion of water budgets for areas 

above Imperial Dam, the published figures of flow at the 

dam prior to 1961 were adjusted by deducting 100,000 

acre-feet per year.

None of the residuals in this tabulation is a valid 

estimate of consumptive use because of the omission 

of important items, particularly changes of storage. 

Each is a fair estimate of the depletion of Colorado 

River caused chiefly by the use of its water in the area.

Using the same average rate of consumptive use by 

cropland (3.6 acre-ft per acre) as that used for areas 

above Imperial Dam, the average consumptive used by 

cropland in the Wellton-Mohawk area was computed 

by C. C. McDonald and O. J. Loeltz of the U.S. Geological Survey (written commun., 1967), as 168,000 acrefeet per year during 1957-59 and 192,000 acre-feet per 

year during 1961-63. The use by native vegetation is 

unknown but probably substantial.

During 1957-59 nearly all the Colorado River water 

diverted to the Wellton-Mohawk area remained there;

unused water percolated into the underlying aquifer 

which had been depleted by pumping prior to 1950. 

Consequently, the residual nearly equals the inflow. By 

1960 the ground-water level had risen sufficiently to 

cause substantial return flow in surface channels, and 

by 1961 drainage by pumping began. Because of the substantial outflow during 1961-63, the residual was 

markedly less than in 1957-59 even though the inflow 

was greater.

In the Yuma area, the acreages of cropland and native vegetation have been relatively stable for many 

years, and considerable information on the movement 

and storage of ground water (described in a later 

chapter) has been gathered since 1960. Using this 

information and methods previously described, C. C. 

McDonald and O. J. Loeltz of the U.S. Geological Survey (written commun., 1967), compiled the following 

water budget and estimates of consumptive use for the 

calendar years 1951-66.

[Mean annual quantities, in acre-ft, 1951-66] 

Water budget

Inflow:

Measured:

Surface...........

Unmeasured:

Surface. __________

Subsurface. _______

Change in storage: 

Unmeasured:

Subsurface. _______

Outflow:

Measured:

Surface...........

Unmeasured:

Subsurface. _______

Residual (consumptive use).

7, 858, 000

2,000

17, 000

+ 80, 000

7, 232, 000

70, 000

495, 000

Consumptive use

Irrigated cropland.____________________

Native vegetation____________________

Other land areas, including city of Yuma. 

Water surface._______-___--_-________.

.-__-. 367,000

.__.-- 53,000

.-_--- 46,000

.----_ 20,000

Total _----- 486, OOP

Average for two methods._______________________ 490, 000

Measured items in the water budget were determined 

by unpublished compilations similar to table 4. The 

small, unmeasured surface inflow was estimated in the 

same manner as the corresponding items in budgets for 

areas above Imperial Dam. The estimated subsurface 

inflow consists of 10,000 acre-feet at Imperial Dam, 

3,000 acre-feet at the gap where the Gila River enters 

the Colorado River valley, and 4,000 acre-feet from all 

other tributary areas. The subsurface outflow crosses 

the international boundary southward into Sonora and
LOWER COLORADO RIVER WATER SUPPLY ITS MAGNITUDE AND DISTRIBUTION D33

westward into Baja California. The increase in storage 

was caused chiefly by irrigation of the very sandy soils 

on the Yuma Mesa, southeast of Yuma, Ariz.

Studies of variability of the yearly differences between measured inflow to and outflow from the Yuma 

area, made in a manner similar to that previously described for the reach Davis Dam to Imperial Dam, indicated that with 95-percent confidence the 16-year average annual difference is within 37,000 acre-feet of the 

long term mean. As the total residual required to balance 

the water budget is 79 percent of the difference between 

measured inflow and outflow, this range of probable 

error may be reasonably applied to the total residual 

also.

Summary of stream depletions, Davis Dam to 

Mexico. Diversions to the metropolitan areas of southern California through the Colorado River aqueduct 

have increased gradually from a few thousand acre-feet 

in 1946 to about 1,100,000 acre-feet in each year after 

1960. Diversions to the Salton Sea basin through the 

All-American Canal have varied between 3 million and 4 

million acre-feet per year since 1945. The consumptive 

use in areas along the Colorado River was relatively 

stable and near 1,900,000 acre-feet per year during the 

17-year period 1950-66. The flow to Mexico has exceeded 

the guaranteed quantity of 1,500,000 acre-feet per year 

in every year since 1944. The excess averaged nearly 

half a million acre-feet, but the excess has been sharply 

reduced in recent years. Practically no water has flowed 

into the Gulf of California since 1959 without having 

been diverted at least once.

The 1,900,000 acre-feet consumed in areas along the 

Colorado River includes about a million acre-feet used 

by crops, nearly 600,000 acre-feet used by native vegetation (excluding unknown use in the Wellton-Mohawk 

area), and nearly 300,000 acre-feet evaporated from 

water surfaces.

The consumptive use of water by cropland is increasing because of the increase of irrigated acreage and the 

growth of recently planted citrus trees. The largest potential increase of irrigated acreage is in the Colorado 

River Indian Reservation, where about 75,000 acres of 

arable land were undeveloped in 1962 (U.S. Bureau of 

Reclamation, 1963). Most of this land, however, was 

covered with native vegetation that used large quantities of water. Hence, the increase in consumptive use 

by cropland will be at least partly compensated for by 

a decrease in consumptive use by native vegetation.

Flow to Mexico exceeding treaty requirements was a 

natural result of streamflow exceeding existing needs in 

the United States. This flow commonly exceeded requirements, however, even during periods of water shortage

because of insufficient regulating capacity near Imperial Dam, release of relatively high flows for short 

periods to move sediment deposits below the dam, and 

return flows from the Yuma and Wellton-Mohawk areas. 

Better regulation of the flow by use of Senator Wash 

Reservoir and more efficient use of return flows probably 

will tend to keep the excess flows below the relatively 

low level achieved in 1966 (about 200,000 acre-ft).

The potential water salvage by channelizing the river, 

eradicating the native vegetation from nonarable flood 

plains that are not within wildlife refuges, and recovering ground water in the Yuma area has been estimated 

by the U.S. Bureau of Reclamation (1964c) as 510,000 

acre-feet. If this much salvage is achieved, the future 

annual depletions of the Colorado River between Davis 

Dam and Mexico may be nearly 500,000 acre-feet less 

than those of 1961-63.

This potential reduction of depletion below Davis 

Dam approximately balances the potential increase of 

depletion a,bove the dam (p. D20); so the future depletion in the entire reach from compact point to Mexico 

(excluding diversions out of the Colorado River valley) 

may not differ greatly from the 2,200,000 acre-feet indicated for recent years. The proposed diversion to central 

Arizona is not included in the depletion discussed here 

because that diversion would involve removal of water 

from the budget area with no return flow and, consequently, would be similar to diversions to southwestern 

California.

SALTON SEA BASIN

The gross annual diversion for 497,000 acres in Imperial and Coachella Valleys during 1961-63 was 3,603,- 

000 acre-feet (item 37 of table 4), or about 7.2 acre-feet 

per acre irrigated. This rate of use, however, is affected 

by high conveyance losses below Pilot Knob (table 5) 

and the discharge of all unconsumed water to the Salton 

Sea.

These large losses are excluded from the following 

water budget for the irrigated land in Imperial Valley:

[Items refer to table4]

Acre-feet

Measured inflow (items 44 and 45) __ 3,056,000 

Measured outflow (item 46) 1, 270, 000 

Residual ___________ - 1, 786, 000

The residual represents an average consumptive use on 

432,000 acres of 4.1 acre-feet per acre (including uses 

in unplanted areas within the irrigated tract).

A similar computation for the area in Coachella Valley served by Colorado River water indicates an apparent consumptive use of 3.8 acre-feet per acre. This 

figure may differ from the actual consumptive use by 

crops because it includes consumptive use by native
D34 WATER RESOURCES OF LOWER COLORADO RIVER-SALTON SEA AREA

vegetation and an increase in ground-water storage but 

excludes ground-water inflow from adjacent areas.

The principal losses involved in the use of Colorado 

Elver water in the Salton Sea basin are conveyance 

losses from canals and discharge to the Salton Sea, but 

neither of these can be evaluated adequately by itself. 

As stated in the discussion of conveyance losses from 

canals, part of the seepage recharges aquifers and may 

be recoverable (some may be recovered in Mexico), and 

another part reaches the Salton Sea through drainage 

channels. The feasibility of reducing seepage losses is 

under investigation by the Bureau of Reclamation. Although some of the discharge to the Salton Sea represents a loss to the irrigation districts, considerable discharge is necessary to maintain soil productivity. Also, 

the sea is sustained almost entirely by the inflow from 

irrigation districts. Consequenlty, an evaluation of any 

programs that would reduce discharge from the districts 

must consider the effects of such programs on the hydrologic regimen of the Salton Sea (Hely and others, 1966).

INTERRELATION OF SURFACE WATER AND GROUND 

WATER

As the Colorado River traverses extensive deposits 

of saturated alluvium, water levels in the alluvium obviously must affect the regimen of the river. Under conditions of excessive uncontrolled withdrawal of ground 

water from the floodplain the river would lose substantial quantities of water to the underlying alluvium. 

Under such conditions nearly all of the ground-water 

recharge would be derived from the river either by direct 

seepage or by application of river water for irrigation; 

hence, the pumping of ground water from the floodplain 

and adjacent areas can add little to the long-term 

water supply available from the lower Colorado River. 

Prudent use of ground water, however, can markedly 

influence the ultimate disposition of this total supplyLosses by seepage from a particular area or by nonbeneficial use can be decreased by lowering the water level 

in some areas. Withdrawals of ground water add to the 

usable supply for the duration of such withdrawals (except when the water is of very poor quality).

Preceding discussions have indicated that the pumping of ground water is intimately related to irrigation 

drainage and water salvage in some areas and that this 

pumping is increasing. Another potentially important 

use of such pumping is for additional stabilization of 

the water supply available below Davis Dam.

To obtain maximum benefit from such short-term

augmentation of the usable supply by withdrawals from 

storage, ground-water storage capacity should be used 

in the same manner as surface storage drawn upon 

when other supplies are insufficient and replenished 

when other supplies are abundant so long as this can 

be done without serious interference with streamflow.

Storage of water beneath the ground prevents the loss 

by evaporation that tends to nullify the benefits of longterm storage in surface reservoirs. However, many other 

problems concerning the characteristics of the groundwater reservoirs and the economics of well-field development and operation, all of which are beyond the scope of 

this report, are involved. Also, management of groundwater storage may require legal controls or authorizations that do not now exist.

Artificial recharge of aquifers to enable optimum use 

of their storage capacity has been employed experimentally and practically since about 1895 (Todd, 1959), and 

its use is increasing. For example, 32.4 percent of the 

water diverted through the Colorado River aqueduct in 

1960 was used to recharge depleted aquifers in southwestern California (Smith and Brewer, 1961).

Some aspects of the conjunctive use of surface and 

subsurface reservoirs and the management of groundwater basins have been discussed in publications of the 

American Society of Civil Engineers (1961, 1964); an 

investigation of the use of aquifers in San Joaquin 

Valley, Calif., for storage of surplus surface water has 

been described by Davis, Lofgren, and Mack (1964). 

Investigations of several aquifers near the lower Colorado River and of the chemical quality of the water 

therein are in progress (1968).

A rough estimate of the potentially usable groundwater storage capacity between Davis Dam and Mexico 

can be derived as follows. If the area of ground-water 

development is assumed to be 150,000 acres and to have 

recoverable water occupying 15 percent of the volume 

of alluvium, each 10-foot change in the average water 

level within the developed area would correspond to 

225,000 acre-feet (or a change of about 45 ft in water 

level would correspond to 1,000,000 acre-ft). Although 

it would be theoretically possible to reserve most of this 

storage for use during the most critical periods, the 

impossibility of forecasting the magnitude and duration of streamflow deficiencies and the economics of 

well fields preclude such ideal use. However, without 

doubt prudent ground-water development can significantly improve the efficiency of water use and stability 

of the supply.
LOWER COLORADO RIVER WATER SUPPLY ITS MAGNITUDE AND DISTRIBUTION D35

DEFICIENCY OF THE COLORADO RIVER SUPPLY

The potential demand for water in the service area 

of the lower Colorado River system greatly exceeds 

presently foreseeable supplies. Thousands of formerly 

irrigated acres in the Gila River basin near Phoenix, 

Ariz., have been abandoned for lack of water; in vast 

areas rates of water use greatly exceeding the average 

annual replenishment of the supplies are sustained by 

continuing withdrawals from rapidly dwindling 

ground-water storage; other areas could be made productive if water were available.

Despite the evident water shortages, the population 

in parts of the service area has been increasing at phenomenal rates. This has been possible partly because 

water requirements of urban and irrigated areas of 

equal size are roughly the same. Urban growth in the 

south coastal basins in California, however, has 

involved interbasin transfers of water within the watershort Southwest (including that through the Colorado 

River aqueduct), and facilities now (1968) under construction will enable transfer from water-surplus areas 

in northern California. The deficiency of the Colorado 

River supply is not expected to deter urban growth in 

the report area, but it will deter expansion of irrigation. 

The necessary urban supplies will be derived by conversion from irrigation uses if necessary.

As satisfaction of all potential water demands in the 

service area is practically impossible, current planning 

is often based on the arbitrary goal established by the 

Colorado River Compact and the Boulder Canyon Project Act at times when the available streamflow records 

indicated a considerably larger mean virgin flow of 

Colorado River than present records indicate. This 

goal is to provide sufficient water in the lower Colorado 

River, or equivalent imports to the service area, to provide for delivery of Mexico's guaranteed allotment and 

for annual consumptive use of 2,800,000 acre-feet in 

Arizona, 4,400,000 acre-feet in California, and 300,000 

acre-feet in Nevada. These prospective uses in Arizona 

and Nevada are much greater than current uses, but 

the prospective use in California is less than current 

use. Some proposals involve much larger quantities of 

water and much larger service areas.

The regulated water supply derived from the drainage basin above compact point is near 13 million acrefeet during dry periods, such as 1931-64, and 15 million

acre-feet during periods of normal runoff. The additional supply derived from inflow to the Colorado River 

between compact point and Davis Dam probably will 

be less than 500,000 acre-feet (assuming an increase 

in the consumptive use of tributary flows) during dry 

periods and slightly greater during periods of normal 

runoff. Hence, the corresponding gross supplies at 

Davis Dam are near 13,500,000 acre-feet and 15,500,000 

acre-feet.

To obtain the net supply available at Davis Dam the 

probable depletions above the dam must be substracted 

from these totals. These depletions, as estimated by 

the U.S. Bureau of Reclamation (1965, p. 236), are 

listed below.

[Amounts given in acre-ft]

Year 1975 1990 2000 2030

Depletion above compact point .. 

Evaporation from Lake Mead (and

4,220,000 

898,000

100,000

110,000

5, 100, 000 

872,000

150,000

110,000

5, 430, 000 

835,000

200,000

110,000

5,800,000 

853,000

300,000

110,000

Total depletion above Davis

5,328,000 6,232,000 6,575,000 7,063,000

For normal runoff conditions, the corresponding1 net 

supply at Davis Dam would be about 10,200,000 acrefeet in 1975 'and 8,400,000 acre-feet in 2030. For dry 

conditions, the corresponding supplies would be 

8,200,000 acre-feet and 6,400,000 acre-feet.

The amount of water required to satisfy basic allotments below Davis Dam (8,700,000 acre-ft) and the 

losses associated with storage and conveyance of water 

below the dam (about 900,000 acre-ft) is 9,600,000 

acre-feet. The usable part of the small inflow below 

Davis Dam probably is little greater than the excess 

flow to Mexico that will be necessary to effect delivery 

of the guaranteed quantity as requested by Mexico. 

Hence, these two small quantities are ignored in this 

discussion.

Comparison of these figures of supply and demand 

shows that the supply is adequate only for periods of 

near normal runoff prior to about 1980. For dry conditions (exemplified by 1931-64) near the year 2030, the 

deficiency would be about 3,200,000 acre-feet. If depletions above compact point should reach the 7,500,000 

acre-feet specified in the Colorado River Compact, the 

deficiency might be as much as 4,900,000 acre-feet.
D36 WATER RESOURCES OF LOWER COLORADO RIVER-SALTON SEA AREA

REFERENCES

Adams, Frank, Santacruz, Armando, Jr., and Favela, J. L., 19SO, 

Appendix 2 in Report of the American Section of the International Water Commission, United States and Mexico: 

U.S. 71st Cong., 2d sess., H. Doc. 359, 492 p.

American Society of Civil Engineers, 1964, Ground-water management for the nation's future [a symposium consisting of 

4 papers] : Am. Soc. Civil Engineers Proceedings, v. 90, 

no. HY 4, Papers 3985, 3973, 3965, and 3981, p. 51-106.

American Society of Civil Engineers, Irrigation and Drainage 

Div., Committee on Ground Water, 1961, Ground Water 

basin management: Manuals of engineering practice, no. 40, 

160 p., New York.

Blaney, Harry F., and Harris, Karl, 1952, Consumptive use of 

water rates in the lower Colorado River basin, in U.S. 

Bur. Reclamation, Report on water supply of the lower 

Colorado River basin: project plan, rept, 427 p., Boulder 

Cjty, Nev.

Brlttan, Margaret R., 1961, Probability analysis applied to the 

development of synthetic hydrology for the Colorado River : 

Colorado Univ., Bur. Econ. Research, 99 p.

Colorado River Board of California, 1962, Salinity problems 

in the lower Colorado River area, statistical appendices: 

Los Angeles, report, 28 p.; 7 pis.; appendices, 82 p.

Davis, G. H., Lofgren, B. E., and Mack, Seymour, 1964, Use of 

ground-water reservoirs for storage of surface water in the 

San Joaquin Valley, California: U.S. Geol. Survey WaterSupply Paper 1618,122 p., 11 pis.

Eakin, Thomas E., 1961, Ground-water appraisal of Pine Valley, Eureka and Elko Counties, Nevada : Nevada Dept. Conserv. and Nat. Resources Water Resources Reconn. Ser. 

Rept. 2, 41 p.

Erie, L. J., French, Orrin F., and Harris,. Karl, 1965, Consumptive use of water by crops in Arizona: Arizona Univ., 

Agr. Expt. Sta., 44 p.

Hardison, Clayton H., 1966, Storage to augment low flows in 

Proceedings of Reservoir Yield Symposium : Water Research 

Assoc., Mar low, Buckinghamshire, England, 38 p.

Hely, Alien G., and Peck, Eugene L., 1964, Precipitation, runoff, 

and water loss in the lower Colorado River-Salton Sea 

area: U.S. Geol. Survey Prof. Paper 486-B, 16 p., 7 pis.

Hely, Alien G., Hughes, G. H., and Irelan, Burdge, 1966, Hydrologic regimen of Salton Sea: U.S. Geol. Survey Prof. Paper 

486-C, 32 p.

lorns, W. V., Hembree, C. H., and Oakland, G. L., 1965, Water 

Resources of the upper Colorado River Basin technical 

report: U.S. Geol. Survey Prof. Paper 441, 370 p.

Julian, Paul R., 1961, A study of the predictability of streamrunoff in the upper Colorado River basin: Colorado Univ., 

High Altitude Observatory, 98 p.

Leopold, Luna B., 1959, Probability analysis applied to a Watersupply problem: U.S. Geol. Survey Circ. 410,18 p.

Lb'ff, George O. G., and Hardison, Clayton H., 1966, Storage 

requirements for water in the United States: Water Resources Research, v. 2, no. 3, p. 323-354.

Meyers, J. S., 1962, Evaporation from the 17 Western States: 

U.S. Geol. Survey Prof. Paper 272-D, 99 p., 1 pi.

Mosk, Stanley, 1959, Water-Supply of the lower Colorado River 

basin: Sacremento, California Department of Justice, Excerpts from briefs and evidence submitted to Simon H. 

Rifkind, Special Master, Arizona v. California Oct. 1959, 

term, 150 p.

Smith, Stephen C., and Brewer, Michael F., 1961, California's 

man-made rivers: California Univ. Agr. Ext. Service, 26 p.

Thomas, H. E., 1954, First fourteen years of Lake Mead: U.S. 

Geol. Survey Circ. 346, 27 p.

Todd, David K., 1959, Annotated bibliography on artificial recharge of ground water through 1954: U.S. Geol. Survey 

Water-Supply Paper 1477,115 p.

U.S. Bureau of Reclamation, 1953, Memorandum supplement to 

report on water supply of the lower Colorado River basin: 

Boulder City, Nev., 48 p.

 1954, Colorado River storage project: U.S. 83rd Oong., 

2d sess., H. Doc. 364, 332 p.

« 1963, Lower Colorado River water salvage ph.reatophyte control, Arizona-California-Nevada': Boulder City, 

Nev., U.S. Bur. Reclamation reconn. report, 57 p., 5 pis.

 1964a, Pacific Southwest water plan, appendix of August 

1963 as modified January 1964: Washington, 300 p. 14 pis.

 1964b, Pacific Southwest water plan Report: Washington, 240 p., 11 pis.

 1964c, Pacific Southwest water plan supplemental information report on water salvage projects lower Colorado 

River, Arizona-California-Nevada: Boulder City, Nev., 61 p. 

13 pis.

 1965, Serial No. 17, Hearings before the Subcommittee of 

Irrigation and Reclamation of the Commitee on Interior and 

Insular Affairs, House of Representatives, on H.R. 4671 and 

similar bills.

U.S. Geological Survey, 1954, Compilation of records of surface 

water of the United States through September 1950, Part 9, 

Colorado River basin: Water-Supply Paper 1313, 749 p. 1 pi.

 1961-68, Annual series, Surface water records of Arizona: 

open-file repts.

 1964, Compilation of records of surface waters of the

United States, October 1950 to September 1960, Part 9, Colorado River basin: Water-Supply Paper 1733, 586 p., 1 pi.

U.S. Supreme Court, 1964, State of Arizona, plaintiff v. State of 

California, et al., defendants: Decree March 9,1964, No. 8, 

original, 14 p.

U.S. Weather Bureau, 1959, Evaporation maps for the United 

States: U.S. Weather Bur. Tech. Paper 37,13 p. 5 pis.

Witmer, T. Richard, 1956, Documents on the use and control of 

the waters of interstate and international streams Compacts, treaties, and adjudications: U.S. Dept. Interior, 760p.

Yevdjevieh, Vujica M., 1961, Some general aspects of fluctuations 

of annual runoff in the upper Colorado River basin: Colorado State Univ., Civil Eng. See, 48 p.
APPENDIX
Given on the following pages are the Colorado River 

Compact and parts of the Rio Grande, Colorado, and 

Tijuana Treaty, quoted from a compilation by Witmer 

(1956), and parts of the decree by the Supreme Court 

of the United States, reproduced from an original publication of the Court (1964).
COLORADO RIVER COMPACT, 1922

[Quoted from a compilation by Witmer (1956) ]

The States of Arizona, California, Colorado, Nevada, 

New Mexico, Utah, and Wyoming, having resolved 

to enter into a compact under the Act of the Congress 

of the United States of America approved August 19, 

1921 (42 Statutes at Large, page 171), and the Acts 

of the Legislatures of the said States, have through their 

Governors appointed as their Commissioners: 

W. S. Norviel for the State of Arizona, 

W. F. McClure for the State of California, 

Delph E. Carpenter for the State of Colorado, 

J. G. Scrugham for the State of Nevada, 

Stephen B. Davis, Jr., for the State of New Mexico, 

R. E. Caldwell for the State of Utah, 

Frank C. Emerson for the State of Wyoming, 

who, after negotiations participated in by Herbert 

Hoover appointed by The President as the representative of the United States of America, have agreed upon 

the following articles:

ARTICLE I

The major purposes of this compact are to provide for 

the equitable division and apportionment of the use of 

the waters of the Colorado River System; to establish 

the relative importance of different beneficial uses of 

water; to promote interstate comity; to remove causes 

of present and future controversies; and to secure the expeditious agricultural and industrial development of the 

Colorado River Basin, the storage of its waters, and the 

protection of life and property from floods. To these 

ends the Colorado River Basin is divided into two 

Basins, and an apportionment of the use of part of the 

water of the Colorado River System is made to each of 

them with the provision that further equitable apportionments may be made.

ARTICLE II

As used in this compact 

(a) The term "Colorado River System" means that 

portion of the Colorado River and its tributaries within 

the United States of America.

(b) The term "Colorado River Basin" means all of 

the drainage area of the Colorado River System and all 

other territory within the United States of America to 

which the waters of the Colorado River System shall be 

beneficially applied.

(c) The term "States of the Upper Division" means 

the States of Colorado, New Mexico, Utah, and 

Wyoming.

(d) The term "States of the Lower Division" means 

the States of Arizona, California, and Nevada.

(e) The term "Lee Ferry" means a point in the main 

stream of the Colorado River one mile below the mouth 

of the Paria River.

(f) The term "Upper Basin" means those parts of 

the States of Arizona, Colorado, New Mexico, Utah, and 

Wyoming within and from which waters naturally 

drain into the Colorado River System above Lee Ferry, 

and also all parts of said States located without the 

drainage area of the Colorado River System which are 

now or shall hereafter be beneficially served by waters 

diverted from the System above Lee Ferry.

(g) The term "Lower Basin" means those parts of 

the States of Arizona, California, Nevada, New Mexico, 

and Utah within and from which waters naturally drain 

into the Colorado River System below Lee Ferry, and 

also all parts of said States located without the drainage area of the Colorado River System which are now 

or shall hereafter be beneficially served by waters 

diverted from the System below Lee Ferry.

(h) The term "domestic use" shall include the use of 

water for household, stock, municipal, mining, milling, 

industrial, and other like purposes, but shall exclude the 

generation of electrical power.

AETICLE m

(a) There is hereby apportioned from the Colorado 

River System in perpetuity to the Upper Basin and to 

the Lower Basin, respectively, the exclusive beneficial 

consumptive use of 7,500,000 acre-feet of water per 

annum, which shall include all water necessary for the 

supply of any rights which may now exist.

(b) In addition to the apportionment in paragraph 

(a), the Lower Basin is hereby given the right to increase its beneficial consumptive use of such waters by 

one million acre-feet per annum.

(c) If, as a matter of international comity, the United 

States of America shall hereafter recognize in the 

United States of Mexico any right to the use of any waters of the Colorado River System, such waters shall be 

supplied first from the waters which are surplus over

D39
D40 WATER RESOURCES OP LOWER COLORADO RIVER-SALTON SEA AREA

and above the aggregate of the quantities specified in 

paragraphs (a) and (b); and if such surplus shall prove 

insufficient for this purpose, then, the burden of such 

deficiency shall be equally borne by the Upper Basin and 

the Lower Basin, and whenever necessary the States of 

the Upper Division shall deliver at Lee Ferry water to 

supply one-half of the deficiency so recognized in addition to that provided in paragraph (d).

(d) The States of the Upper Division will not cause 

the flow of the river at Lee Ferry to be depleted below 

an aggregate of 75,000,000 acre-feet for any period of 

ten consecutive years reckoned in continuing progressive 

series beginning with the first day of October next succeeding the ratification of this compact.

(e) The States of the Upper Division shall not withhold water, and the States of the Lower Division shall 

not require the delivery of water, which cannot reasonably be applied to domestic and agricultural uses.

(f) Further equitable apportionment of the beneficial 

uses of the waters of the Colorado River System unapportioned by paragraphs (a), (b),and (c) may be made 

in the manner provided in paragraph (g) at any time 

after October first, 1963, if and when either Basin shall 

have reached its total beneficial consumptive use as set 

out in paragraphs (a) and (b).

(g) In the event of a desire for a further apportionment as provided in paragraph (f) any two signatory 

States, acting through their Governors, may give joint 

notice of such desire to the Governors of the other signatory States and to The President of the United States 

of America, and it shall be the duty of the Governors of 

the signatory States and of The President of the United 

States of America forthwith to appoint representatives, 

whose duty it shall be to divide and apportion equitably 

between the Upper Basin and Lower Basin the beneficial 

use of the unapportioned water of the Colorado Eiver 

System as mentioned in paragraph (f), subject to the 

legislative ratification of the signatory States and the 

Congress of the United States of America.

ARTICLE IV

(a) Inasmuch as the Colorado River has ceased to 

be navigable for commerce and the reservation of its 

waters for navigation would seriously limit the development of its Basin, the use of its waters for purposes 

of navigration shall be subservient to the uses of such 

waters for domestic, agricultural, and power purposes. 

If the Congress shall not consent to this paragraph, the 

other provisions of this compact shall nevertheless remain binding.

(b) Subject to the provisions of this compact, water 

of the Colorado River System may be impounded and 

used for the generation of electrical power, but such 

impounding and use shall be subservient to the use 

and consumption of such water for agricultural and 

domestic purposes and shall not interfere with or prevent use for such dominant purposes.

(c) The provisions of this article shall not apply to 

or interfere with the regulation and control by any State 

within its boundaries of the appropriation, use, and 

distribution of water.

ARTICLE v

The chief official of each signatory State charged 

with the administration of water rights, together with 

the Director of the United States Reclamation Service 

and the Drector of the Unted States Geologcal Survey 

shall cooperate, ex-offico:

(a) To promote the systematic determination and coordination of the facts as to flow, appropriation, consumption, and use of water in the Colorado River Basin, 

and the interchange of available information in such 

matters.

(b) To secure the ascertainment and publication of 

the annual flow of the Colorado River at Lee Ferry.

(c) To perform such other duties as may be assigned by mutual consent of the signatories from time 

to time.

ARTICLE VI

Should any claim or controversy arise between any 

two or more of the signatory States: (a) with respect to 

the waters of the Colorado River System not covered by 

the terms of this compact; (b) over the meaning or performance of any of the terms of this compact; (c) as to 

the allocation of the burdens incident to the performance of any article of this compact or the delivery of waters as herein provided; (d) as to the construction or 

operation of works within the Colorado River Basin to 

be situated in two or more States, or to be constructed in 

one State for the benefit of another State; or (e) as to 

the diversion of water in one State for the benefit of another State; the Governors of the States affected, upon 

the request of one of them, shall forthwith appoint Commissioners with power to consider and adjust such claim 

or controversy, subject to ratification by the Legislatures of the States so affected.

Nothing herein contained shall prevent the adjustment of any such claim or controversy by any present 

method or by direct future legislative action of the interested States.
LOWER COLORADO RIVER WATER SUPPLY ITS MAGNITUDE AND DISTRIBUTION D41

ARTICLE VH

Nothing in this compact shall be construed as affecting the obligations of the United States of America to 

Indian tribes.

ARTICLE VIII

Present perfected rights to the beneficial use of waters 

of the Colorado River System are unimpared by this 

compact. Whenever storage capacity of 5,000,000 acrefeet shall have been provided on the main Colorado 

River within or for the benefit of the Lower Basin, then 

claims of such rights, if any, by appropriators or users 

of water in the Lower Basin against appropriators or 

users of water in the Upper Basin shall attach to and be 

satisfied from water that may be stored not in conflict 

with Article III.

All other rights to beneficial use of waters of the Colorado River System shall be satisfied solely from the water apportioned to that Basin in which they are situate.

ARTICLE IX

Nothing in this compact shall be construed to limit or 

prevent any State from instituting or maintaining any 

action or proceeding, legal or equitable, for the protection of any right under this compact or the enforcement 

of any of its provisions.

ARTICLE X

This compact may be terminated at any time by the 

unanimous agreement of the signatory States. In the 

event of such termination all rights established under it 

shall continue unimpaired.

ARTICLE XI

This compact shall become binding and obligatory 

when it shall have been approved by the Legislatures of 

each of the signatory States and by the Congress of the 

United States. Notice of approval by the Legislatures 

shall be given by the Governor of each signatory State 

to the Governors of the other signatory States and to the 

President of the United States, and the President of the 

United States is requested to give notice to the Governors of the signatory States of approval by the Congress 

of the United States.

IN WITNESS WHEREOF, the Commissioners have signed 

this compact in a single original, which shall be deposited in the archives of the Department of State of the 

United States of America and of which a duly certified 

copy shall be forwarded to the Governor of each of the 

signatory States.

Done at the City of Sante Fe, New Mexico, this 

twenty-fourth day of November, A.D. One Thousand 

Nine Hundred and Twenty-two.

W. S. NORVIEL

W. F. McCLURE

DELPH E. CARPENTER 

J. G. SCRUGHAM 

STEPHEN B. DAVIS, Jr. 

R. E. CALDWELL 

FRANK C. EMERSON 

Approved:

HERBERT HOOVER
RIO GRANDE, COLORADO, AND TIJUANA 

TREATY, 1944

[Quoted from a compilation by Witmer (1956). Only those 

parts of the treaty that deal directly with delivery of Colorado 

River water to Mexico, Articles 10, 11, and 15, are reproduced 

herein.

Since the construction in 1950 of Morelos Dam in the limitrophe section of the river, at the head of Alamo Canal the 

water referred to in paragraph (c) of Article 11 and Schedule 

II of Article 15 has been delivered to Alamo Canal through the 

river channel rather than the canal connecting Pilot Knob 

wasteway to Alamo Canal.]

Ill COLORADO RIVER

ARTICLE 10

Of the waters of the Colorado River, from any and all 

sources, there are allotted to Mexico:

(a) A guaranteed annual quantity of 1,500,000 acrefeet (1,850,234,000 cubic meters) to be delivered in accordance with the provisions of Article 15 of this Treaty.

(b) Any other quantities arriving at the Mexican 

points of diversion, with the understanding that in any 

year in which, as determined by the United States Section, there exists a surplus of waters of the Colorado 

River in excess of the amount necessary to supply uses 

in the United States and the guaranteed quantity of 

1,500,000 acre-feet (1,850,234,000 cubic meters) annually 

to Mexico, the United States undertakes to deliver to 

Mexico, in the manner set out in Article 15 of this 

Treaty, additional waters of the Colorado River system 

to provide a total quantity not to exceed 1,700,000 acrefeet (2,096,931,000 cubic meters) a year. Mexico shall 

acquire no right beyond that provided by this subparagraph by the use of the waters of the Colorado 

River system, for any purpose whatsoever, in excess 

of 1,500,000 acre-feet (1,850,234,000 cubic meters) 

annually.

In the event of extraordinary drought or serious accident to the irrigation system in the United States, thereby making it difficult for the United States to deliver 

the guaranteed quantity of 1,500,000 acre-feet (1,850,- 

234,000 cubic meters) a year, the water allotted to 

Mexico under subparagraph (a) of this Article will be 

reduced in the same proportion as consumptive uses in 

the United States are reduced.

ARTICLE 11

(a) The United States shall deliver all waters allotted 

to Mexico wherever these waters may arrive in the bed

D42

of the limitrophe section of the Colorado River, with the 

exceptions hereinafter provided. Such waters shall be 

made up of the waters of the said river, whatever their 

origin, subject to the provisions of the following paragraphs of this Article.

(b) Of the waters of the Colorado River alloted to 

Mexico by subparagraph (a) of Article 10 of this 

Treaty, the United States shall deliver, wherever such 

waters may arrive in the limitrophe section of the river, 

1,000,000 acre-feet (1,233,489,000 cubic meters) annually 

from the time the Da vis dam and reservoir are placed in 

operation until January 1,1980 and thereafter 1,125,000 

acre-feet (1,387,675,000 cubic meters) annually, except 

that, should the main diversion structure referred to in 

subparagraph (a) of Article 12 of this Treaty be located 

entirely in Mexico and should Mexico so request, the 

United States shall deliver a quantity of water not exceeding 25,000 acre-feet (30,837,000 cubic meters) annually, unless a larger quantity may be mutually agreed 

upon, at a point, to be likewise mutually agreed upon, on 

the international land boundary near San Luis, Sonora, 

in which event the quantities of 1,000,000 acre-feet 

(1,233,489,000 cubic meters) and 1,125,000 acre-feet 

(1,387,675,000 cubic meters) provided hereinabove as 

deliverable in the limitrophe section of the river shall 

be reduced by the quantities to be delivered in the year 

concerned near San Luis, Sonora.

(c) During the period from the time the Davis dam 

and reservoir are placed in operation until January 1, 

1980, the United States shall also deliver to Mexico an-, 

nually, of the water allotted to it, 500,000 acre-feet 

(616,745,000 cubic meters), and thereafter the United 

States shall deliver annually 375,000 acre-feet (462,558,- 

000 cubic meters), at the international boundary line, by 

means of the All-American Canal and a canal connecting the lower end of the Pilot Knob "Wasteway with the 

Alamo Canal or with any other Mexican canal which 

may be substituted for the Alamo Canal. In either event 

the deliveries shall be made at an operating water surface elevation not higher than that of the Alamo Canal 

at the point where it crossed the international boundary 

line in the year 1943.

(d) All the deliveries of water specified above shall 

be made subject to the provisions of Article 15 of this 

Treaty.
LOWER COLORADO RIVER WATER SUPPLY ITS MAGNITUDE AND DISTRIBUTION D43

ARTICLE 15

A. The water allotted in subparagraph (a) of Article 

10 of this Treaty shall be delivered to Mexico at the 

points of delivery specified in Article 11, in accordance 

with the following two annual schedules of deliveries by 

months, which the Mexican Section shall formulate and 

present to the Commission before the beginning of each 

calendar year.

Schedule I

Schedule I shall cover the delivery, in the limitrophe 

section of the Colorado River, of 1,000,000 acre-feet 

(1,233,489,000 cubic meters) of water each, year from the 

date Davis dam and reservoir are placed in operation 

until January 1,1980 and the delivery of 1,125,000 acrefeet (1,387,675,000 cubic meters) of water each year 

thereafter. This schedule shall be formulated subject to 

the following limitations:

With reference to the 1,000,000 acre-foot (1,233,489,- 

000 cubic meter) quantity:

(a) During the months of January, February, October, November and December the prescribed rate of 

delivery shall be not less than 600 cubic feet (17.0 cubic 

meters) nor more than 3,500 cubic feet (99.1 cubic 

meters) per second.

(b) During the remaining months of the year the 

prescribed rate of delivery shall be not less than 1,000 

cubic feet (28.3 cubic meters) nor more than 3,500 cubic 

feet (99.1 cubic meters) per second.

With reference to the 1,125,000 acre-foot (1,387,- 

675,000 cubic meter) quantity :

(a) During the months of January, February, October, November and December the prescribed rate of 

delivery shall be not less than 675 cubic feet (19.1 cubic 

meters) nor more than 4,000 cubic feet (113.3 cubic 

meters) per second.

(b) During the remaining months of the year the 

prescribed rate of delivery shall be not less than 1,125 

cubic feet (31.9 cubic meters) nor more than 4,000 cubic 

feet (113.3 cubic meters) per second.

Should deliveries of water be made at a point on the 

land boundary near San Luis, Sonora, as provided for in 

Article 11, such deliveries shall be made under a subschedule to be formulated and furnished by the Mexican 

Section. The quantities and monthly rates of deliveries 

under such sub-schedule shall be in proportion to those 

specified for Schedule I, unless otherwise agreed upon 

by the Commission.

Schedule II

Schedule II shall cover the delivery at the boundary 

lines by means of the All-American Canal of 500,000 

acre-feet (616,745,000 cubic meters) of water each year

from the date Davis dam and reservoir are placed in 

operation until January 1, 1980 and the delivery of 

375,000 acre-feet (462,558,000 cubic meters) of water 

each year thereafter. This schedule shall be formulated 

subject to the following limitations:

With reference to the 500,000 acre-foot (616,745,000 

cubic meter) quantity:

(a) During the months of January, February, October, November and December the prescribed rate of 

delivery shall be not less than 300 cubic feet (8.5 cubic 

meters) nor more than 2,000 cubic feet (56.6 cubic 

meters) per second.

(b) During the remaining months of the year the 

prescribed rate of delivery shall be not less than 500 

cubic feet (14.2 cubic meters) nor more than 2,000 cubic 

feet (56.6 cubic meters) per second.

With reference to the 375,000 acre-foot (462,558,000 

cubic meter) quantity:

(a) During the months of January, February, October, November and December the prescribed rate of delivery shall be not less than 225 cubic feet (6.4 cubic 

meters) nor more than 1,500 cubic feet (42.5 cubic 

meters) per second.

(b) During the remaining months of the year the 

prescribed rate of delivery shall be not less than 375 

cubic feet (10.6 cubic meters) nor more than 1,500 

cubic feet (42.5 cubic meters) per second.

B. The United States shall be under no obligation 

to deliver, through the All-American Canal, more than 

500,000 acre-feet (616,745,000 cubic meters) annually 

from the date Davis dam and reservoir are placed in 

operation until January 1, 1980 or more than 375,000 

acre-feet (462,558,000 cubic meters) annually thereafter. 

If, by mutual agreement, any part of the quantities of 

water specified in this paragraph are delivered to Mexico 

at points on the land boundary otherwise than through 

the All-American Canal, the above quantities of water 

and the rates of deliveries set out under Schedule II of 

this Article shall be correspondingly diminished.

C. The United States shall have the option of delivering, at the point on the land boundary mentioned in subparagraph (c) of Article 11, any part or all of the water 

to be delivered at that point under Schedule II of this 

Article during the months of January, February, October, November, and December of each year, from any 

source whatsoever, with the understanding that the total 

specified annual quantities to be delivered through the 

All-American Canal shall not be reduced because of the 

exercise of this option, unless such reduction be requested by the Mexican Section, provided that the exercise of this option shall not have the effect of increasing 

the total amount of scheduled water to be delivered to 

Mexico.
D44 WATER RESOURCES OF LOWER COLORADO RIVER-SALTON SEA AREA

D. In any year in which there shall exist in the river 

water in excess of that necessary to satisfy the requirements in the United States and the guaranteed quantity 

of 1,500,000 acre-feet (1,850,234,000 cubic meters) allotted to Mexico, the United States hereby declares its 

intention to cooperate with Mexico in attempting to supply additional quantities of water through the AilAmerican Canal as such additional quantities are desired by Mexico, if such use of the Canal and facilities 

will not be detrimental to the United States, provided 

that the delivery of any additional quantities through 

the All-American Canal shall not have the effect of increasing the total scheduled deliveries to Mexico. Mexico 

hereby declares its intention to cooperate with the 

United States by attempting to curtail deliveries of water through the All-American Canal in years of limited 

supply, if such curtailment can be accomplished without 

detriment to Mexico and is necessary to allow full use of 

all available water supplies, provided that such curtailment shall not have the effect of reducing the total 

scheduled deliveries of water to Mexico.

E. In any year in which there shall exist in the river 

water in excess of that necessary to satisfy the requirements in the United States and the guaranteed quantity

of 1,500,000 acre-feet (1,850,234,000 cubic meters) allotted to Mexico, the United States Section shall so inform the Mexican Section in order that the latter may 

schedule such surplus water to complete a quantity up 

to a maximum of 1,700,000 acre-feet (2,096,931,000 cubic 

meters). In this circumstance the total quantities to be 

delivered under Schedules I and II shall be increased 

in proportion to their respective total quantities and the 

two schedules thus increased shall be subject to the same 

limitation as those established for each under paragraph A of this Article.

F. Subject to the limitations as to rates of deliveries 

and total quantities set out in Schedules I and II, Mexico 

shall have the right, upon thirty days notice in advance 

to the United States Section, to increase or decrease each 

monthly quantity prescribed by those schedules by not 

more than 20% of the monthly quantity.

G. The total quantity of water to be delivered under 

Schedule I of paragraph A of this Article may be increased in any year if the amount to be delivered under 

Schedule II is correspondingly reduced and if the limitations as to rates of delivery under each schedule are 

correspondingly increased and reduced.
SUPREME COURT OF THE UNITED STATES

No. 8, ORIGINAL

STATE OF ARIZONA, PLAINTIFF

v.

STATE OF CALIFORNIA, ET AL., DEFENDANTS

DECREE. MARCH 9, 1964.

It is ORDERED, ADJUDGED AND DECREED that

I. For purposes of this decree:

(A) "Consumptive use" means diversions from the 

stream less such return flow thereto as is available for 

consumptive use in the United States or in satisfaction 

of the Mexican treaty obligation;

(B) "Mainstream" means the mainstream of the Colorado River downstream from Lee Ferry within the United 

States, including the reservoirs thereon;

(C) Consumptive use from the mainstream within a 

state shall include all consumptive uses of water of the 

mainstream, including water drawn from the mainstream 

by underground pumping, and including but not limited 

to, consumptive uses made by persons, by agencies of 

that state, and by the United States for the benefit of 

Indian reservations and other federal establishments 

within the state;

(D) "Regulatory structures controlled by the United 

States" refers to Hoover Dam, Davis Dam, Parker Dam, 

Headgate Rock Dam, Palo Verde Dam, Imperial Dam, 

Laguna Dam and all other dams and works on the 

mainstream now or hereafter controlled or operated by 

the United States which regulate the flow of water 

in the mainstream or the diversion of water from the 

mainstream;

(E) "Water controlled by the United States" refers to 

the water in Lake Mead, Lake Mohave, Lake Havasu 

and all other water in the mainstream below Lee Ferry 

and within the United States;

(F) "Tributaries" means all stream systems the waters 

of which naturally drain into the mainstream of the 

Colorado River below Lee Ferry;

(G) "Perfected right" means a water right acquired 

in accordance with state law, which right has been exercised by the actual diversion of a specific quantity of 

water that has been applied to a defined area of land or

to definite municipal or industrial works, and in addition 

shall include water rights created by the reservation of 

mainstream water for the use of federal establishments 

under federal law whether or not the water has been 

applied to beneficial use;

(H) "Present perfected rights" means perfected rights, 

as here defined, existing as of June 25, 1929, the effective 

date of the Boulder Canyon Project Act;

(I) "Domestic use" shall include the use of water for 

household, stock, municipal, mining, milling, industrial, 

and other like purposes, but shall exclude the generation 

of electrical power;

(J) "Annual" and "Year," except where the context 

may otherwise require, refer to calendar years;

(K) Consumptive use of water diverted in one state 

for consumptive use in another state shall be treated as 

if diverted in the state for whose benefit it is consumed.

II. The United States, its officers, attorneys, agents 

and employees be and they are hereby severally enjoined:

(A) From operating regulatory structures controlled 

by the United States and from releasing water controlled 

by the United States other than in accordance with the 

following order of priority:

(1) For river regulation, improvement of navigation, 

and flood control;

(2) For irrigation and domestic uses, including the 

satisfaction of present perfected rights; and

(3) For power;

Provided, however, that the United States may release 

water in satisfaction of its obligations to the United 

States of Mexico under the treaty dated February 3, 

1944, without regard to the priorities specified in this 

subdivision (A);

(B) From releasing water controlled by the United 

States for irrigation and domestic use in the States of 

Arizona, California and Nevada, except as follows:

D45
D46 WATER RESOURCES OF LOWER COLORADO RIVER-SALTON SEA AREA

(1) If sufficient mainstream water is available for 

release, as determined by the Secretary of the Interior, 

to satisfy 7,500,000 acre feet of annual consumptive use 

in the aforesaid three states, then of such 7,500,000 acre 

feet of consumptive use, there shall be apportioned 

2,800,000 acre feet for use in Arizona, 4,400,000 acre feet 

for use in California, and 300,000 acre feet for use in 

Nevada;

(2) If sufficient mainstream water is available for 

release, as determined by the Secretary of the Interior, 

t6 satisfy annual consumptive use in the aforesaid states 

in excess of 7,500,000 acre feet, such excess consumptive 

use is surplus, and 50% thereof shall be apportioned for 

use in Arizona and 50% for use in California; provided, 

however, that if the United States so contracts with 

Nevada, then 46% of such surplus shall be apportioned 

for use in Arizona and 4% for use in Nevada;

(3) If insufficient mainstream water is available for 

release, as determined by the Secretary of the Interior, 

to satisfy annual consumptive use of 7,500,000 acre feet in 

the aforesaid three states, then the Secretary of the 

Interior, after providing for satisfaction of present perfected rights in the order of their priority dates without 

regard to state lines and after consultation with the 

parties to major delivery contracts and such representatives as the respective states may designate, may apportion the amount remaining available for consumptive use 

in such manner as is consistent with the Boulder 

Canyon Project Act as interpreted by the opinion of this 

Court herein, and with other applicable federal statutes, 

but in no event shall more than 4,400,000 acre feet be 

apportioned for use in California including all present 

perfected rights;

(4) Any mainstream water consumptively used within 

a state shall be charged to its apportionment, regardless 

of the purpose for which it was released;

(5) Notwithstanding the provisions of Paragraphs (1) 

through (4) of this subdivision (B), mainstream water 

shall be released or delivered to water users (including but 

not limited to, public and municipal corporations and 

other public agencies) in Arizona, California, and Nevada 

only pursuant to valid contracts therefor made with such 

users by the Secretary of the Interior, pursuant to Section 5 of the Boulder Canyon Project Act or any other 

applicable federal statute;

(6) If, in any one year, water apportioned for consumptive use in a state will not be consumed in that 

state, whether for the reason that delivery contracts for 

the full amount of the state's apportionment are not in 

effect or that users cannot apply all of such water to 

beneficial uses, or for any other reason, nothing in this 

decree shall be construed as prohibiting the Secretary of 

the Interior from releasing such apportioned but unused

water during such year for consumptive use in the other 

states. No rights to the recurrent use of such water 

shall accrue by reason of the use thereof;

(C) From applying the provisions of Article 7 (d) of 

the Arizona water delivery contract dated February 9, 

1944, and the provisions of Article 5 (a) of the Nevada 

water delivery contract dated March 30, 1942, as 

amended by the contract dated January 3,1944, to reduce 

the apportionment or delivery of mainstream water to 

users within the States of Arizona and Nevada by reason 

of any uses in such states from the tributaries flowing 

therein;

(D) From releasing water controlled by the United 

States for use in the States of Arizona, California, and 

Nevada for the benefit of any federal establishment 

named in this subdivision (D) except in accordance with 

the allocations made herein; provided, however, that such 

release may be made notwithstanding the provisions of 

Paragraph (5) of subdivision (B) of this Article; and 

provided further that nothing herein shall prohibit the 

United States from making future additional reservations 

of mainstream water for use in any of such States as may 

be authorized by law and subject to present perfected 

rights and rights under contracts theretofore made with 

water users in such State under Section 5 of the Boulder 

Canyon Project Act or any other applicable federal 

statute:

(1) The Chemehuevi Indian Reservation in annual 

quantities not to exceed (i) 11,340 acre feet of diversions 

from the mainstream or (ii) the quantity of mainstream 

water necessary to supply the consumptive use required 

for irrigation of 1,900 acres and for the satisfaction of 

related uses, whichever of (i) or (ii) is less, with a priority 

date of February 2, 1907;

(2) The Cocopah Indian Reservation in annual quantities not to exceed (i) 2,744 acre feet of diversions from 

the mainstream or (ii) the quantity of mainstream water 

necessary to supply the consumptive use required for 

irrigation of 431 acres and for the satisfaction of related 

uses, whichever of (i) or (ii) is less, with a priority date 

of September 27, 1917;

(3) The Yuma Indian Reservation in annual quantities not to exceed (i) 51,616 acre feet of diversions from 

the mainstream or (ii) the quantity of mainstream water 

necessary to supply the consumptive use required for 

irrigation of 7,743 acres and for the satisfaction of related 

uses, whichever of (i) or (ii), is less, with a priority date 

of January 9, 1884;

(4) The Colorado River Indian Reservation in annual 

quantities not to exceed (i) 717,148 acre feet of diversions 

from the mainstream or (ii) the quantity of mainstream 

water necessary to supply the consumptive use required 

for irrigation of 107,588 acres and for the satisfaction of
LOWER COLORADO RIVER WATER SUPPLY-ITS MAGNITUDE AND DISTRIBUTION D47

related uses, whichever of (i) or (ii) is less, with priority 

dates of March 3, 1865, for lands reserved by the Act of 

March 3, 1865 (13 Stat. 541, 559); November 22, 1873, 

for lands reserved by the Executive Order of said date; 

November 16, 1874, for lands reserved by the Executive 

Order of said date, except as later modified; May 15, 

1876, for lands reserved by the Executive Order of said 

date; November 22, 1915, for lands reserved by the 

Executive Order of said date;

(5) The Fort Mohave Indian Reservation in annual 

quantities not to exceed (i) 122,648 acre feet of diversions 

from the mainstream or (ii) the quantity of mainstream 

water necessary to supply the consumptive use required 

for irrigation of 18,974 acres and for the satisfaction of 

related uses, whichever of (i) or (ii) is less, and, subject 

to the next succeeding proviso, with priority dates of 

September 18, 1890, for lands transferred by the Executive Order of said date; February 2, 1911, for lands reserved by the Executive Order of said date; provided, 

however, that lands conveyed to the State of California 

pursuant to the Swamp and Overflowed Lands Act 

[9 Stat. 519 (1850)] as well as any accretions thereto to 

which the owners of such land may be entitled, and lands 

patented to the Southern Pacific Railroad pursuant to 

the Act of July 27, 1866 (14 Stat. 292) shall not be 

included as irrigable acreage within the Reservation and 

that the above specified diversion requirement shall be 

reduced by 6.4 acre feet per acre of such land that is 

irrigable; provided that the quantities fixed in this paragraph and paragraph (4) shall be subject to appropriate 

adjustment by agreement or decree of this Court in the 

event that the boundaries of the respective reservations 

are finally determined;

(6) The Lake Mead National Recreation Area in 

annual quantities reasonably necessary to fulfill the purposes of the Recreation Area, with priority dates of 

March 3, 1929, for lands reserved by the Executive Order 

of said date (No. 5105), and April 25, 1930, for lands 

reserved by the Executive Order of said date (No. 5339);

(7) The Havasu Lake National Wildlife Refuge in 

annual quantities reasonably necessary to fulfill the purposes of the Refuge, not to exceed (i) 41,839 acre feet of 

water diverted from the mainstream or (ii) 37,339 acre 

feet of consumptive use of mainstream water, whichever 

of (i) or (ii) is less, with a priority date of January 22, 

1941, for lands reserved by the Executive Order of said 

date (No. 8647), and a prority date of February 11,1949, 

for land reserved by the Public Land Order of said date 

(No. 559) ;

(8) The Imperial National Wildlife Refuge in annual 

quantities reasonably necessary to fulfill the purposes of 

the Refuge not to exceed (i) 28,000 acre feet of water 

diverted from the mainstream or (ii) 23,000 acre feet of

321-230 O 69 2

consumptive use of mainstream water, whichever of (i) 

or (ii) is less, with a priority date of February 14, 1941 ;

(9) Boulder City, Nevada, as authorized by the Act 

of September 2, 1958, 72 Stat. 1726, with a priority date 

of May 15, 1931;

Provided further, that consumptive uses from the 

mainstream for the benefit of the above-named federal 

establishments shall, except as necessary to satisfy present 

perfected rights in the order of their priority dates without regard to state lines, be satisfied only out of water 

available, as provided in subdivision (B) of this Article, 

to each state wherein such uses occur and subject to, in 

the case of each reservation, such rights as have been 

created prior to the establishment of such reservation by 

contracts executed under Section 5 of the Boulder Canyon 

Project Act or any other applicable federal statute.

III. The States of Arizona, California and Nevada, 

Palo Verde Irrigation District, Imperial Irrigation District, Coachella Valley County Water District, Metropolitan Water District of Southern California, City of 

Los Angeles, City of San Diego, and County of San 

Diego, and all other users of water from the mainstream 

in said states, their officers, attorneys, agents and employees, be and they are hereby severally enjoined:

(A) From interfering with the management and operation, in conformity with Article II of this decree, of 

regulatory structures controlled by the United States;

(B) From interfering with or purporting to authorize 

the interference with releases and deliveries, in conformity with Article II of this decree, of water controlled 

by the United States;

(C) From diverting or purporting to authorize the 

diversion of water from the mainstream the diversion of 

which has not been authorized by the United States for 

use in the respective states; and provided further that no 

party named in this Article and no other user of water 

in said states shall divert or purport to authorize the 

diversion of water from the mainstream the diversion of 

which has not been authorized by the United States for its 

particular use;

(D) From consuming or purporting to authorize the 

consumptive use of water from the mainstream in excess 

of the quantities permitted under Article II of this decree.

V. The United States shall prepare and maintain, or 

provide for the preparation and maintenance of, and shall 

make available, annually and at such shorter intervals 

as the Secretary of the Interior shall deem necessary or 

advisable, for inspection by interested persons at all 

reasonable times and at a reasonable place or places, 

complete, detailed and accurate records of:
D48 WATER RESOURCES OP LOWER COLORADO RIVER-SALTON SEA AREA

(A) Releases of water through regulatory structures 

controlled by the United States;

(B) Diversions of water from the mainstream, return 

flow of such water to the stream as is available for consumptive use in the United States or in satisfaction of 

the Mexican treaty obligation, and consumptive use of 

such water. These quantities shall be stated separately 

as to each diverter from the mainstream, each point of 

diversion, and each of the States of Arizona, California 

and Nevada;

(C) Releases of mainstream water pursuant to orders 

therefor but not diverted by the party ordering the same, 

and the quantity of such water delivered to Mexico in 

satisfaction of the Mexican Treaty or diverted by others 

in satisfaction of rights decreed herein. These quantities 

shall be stated separately as to each diverter from the 

mainstream, each point of diversion, and each of the 

States of Arizona, California and Nevada;

(D) Deliveries to Mexico of water in satisfaction of 

the obligations of Part III of the Treaty of February 3, 

1944, and, separately stated, water passing to Mexico in 

excess of treaty requirements;

(E) Diversions of water from the mainstream of the 

Gila and San Francisco Rivers and the consumptive use 

of such water, for the benefit of the Gila National Forest.

VI. Within two years from the date of this decree, the 

States of Arizona, California, and Nevada shall furnish 

to this Court and to the Secretary of the Interior a list 

of the present perfected rights, with their claimed priority 

dates, in waters of the mainstream within each state, 

respectively, in terms of consumptive use, except those 

relating to federal establishments. Any named party to 

this proceeding may present its claim of present perfected 

rights or its opposition to the claims of others. The Secretary of the Interior shall supply similar information, 

within a similar period of time, with respect to the claims 

of the United States to present perfected rights within 

each state. If the parties and the Secretary of the

Interior are unable at that time to agree on the present 

perfected rights to the use of mainstream water in each 

state, and their priority dates, any party may apply to 

the Court for the determination of such rights by the 

Court.

VIII. This decree shall not affect:

(A) The relative rights inter sese of water users within 

any one of the states, except as otherwise specifically 

provided herein;

(B) The rights or priorities to water in any of the 

Lower Basin tributaries of the Colorado River in the 

States of Arizona, California, Nevada, New Mexico and 

Utah except the Gila River System;

(C) The rights or priorities, except as specific provision is made herein, of any Indian Reservation, National

Forest, Park, Recreation Area, Monument or Memorial, 

or other lands of the United States;

(D) Any issue of interpretation of the Colorado River 

Compact.

IX. Any of the parties may apply at the foot of this 

decree for its amendment or for further relief. The 

Court retains jurisdiction of this suit for the purpose of 

any order, direction, or modification of the decree, or any 

supplementary decree, that may at any time be deemed 

proper in relation to the subject matter in controversy.

MR. JUSTICE DOUGLAS dissents.

MR. JUSTICE HARLAN and MR. JUSTICE STEWART dissent 

to the extent that the decree conflicts with the views 

expressed in the dissenting opinion of MR. JUSTICE 

HARLAN, 373 U. S. 546, 603.

THE CHIEF JUSTICE took no part in the consideration 

or decision of this case.
TABLES OP BASIC DATA

In the tables that follow, streamflow data are from the U.S. Geological 

Survey (1954, 1964, 1961-68), except as noted. The details of cooperation in 

collecting previously published data are given in those reports.

TABLE 6. Annual flow of Colorado River at compact point, near Lees Ferry, Ariz., 1896-1966, in millions of acre-feet

Water year

1896

1897

1898

1899

1900

1901

1902

1903

1903

1905

1906

1907

1908

1909

1910

1911

1912

1913

Actual flow

9.760

17.50

13.30

15.25

12.60

12.90

8.740

13.95

14.70

15.00

17.96

22.00

11.76

21.71

12.97

14.62

18.88

12.99

Virgin flow

10.09

18.01

13.82

15.87

13.23

13.58

9.393

14.81

15.64

16.03

19.12

23.40

12.86

23.28

14.25

16.03

20.52

14.47

Water year

1914

1915

1916

1917

1918

1919

1920

1921

1922

1923

1924

1925

1926

1927

1928

1929

1930

1931

Actual flow

19.34

12.50

17.32

21.89

13.65

10.86

19.74

20.72

16.30

16.26

12.48

11.34

14.01

16.59

15.32

19.22

13.07

6.388

Virgin flow

21.22

14.03

19.20

24.04

15.36

12.46

21.95

23.02

18.31

18.27

14.20

13.03

15.85

18.62

17.28

21.43

14.88

7.769

Water year

1932

1933

1934

1935

1936

1937

1938

1939

1940

1941

1942

1943

1944

1945

1946

1947

1948

1949

Actual flow

15.29

9.745

4.397

9.911

11.97

11.90

15.44

9.394

7.082

16.05

17.03

11.26

13.22

11.54

8.744

13.51

13.69

14.36

Virgin flow

17.24

11.36

5.640

11.55

13.80

13.74

17.54

11.08

8.601

18.15

19.12

13.10

15.15

13.41

10.42

15.47

15.62

16.40

Water year

1950

1951

1952

1953

1954

1955

1956

1957

1958

1959

1960

1961

1962

1963

1964

1965

1966

Actual flow

11.06

9.831

17.98

8.805

6.116

7.307

8.750

17.34

14.26

6.756

9.192

6.674

14.79

2.52

2.43

14.97

7.87

Virgin flow

13.07

11.88

20.68

10.68

7.766

9.146

10.79

20.07

16.57

8.597

11.29

8.491

17.33

8.400

10.10

18.60

10.80

NOTE. Records of actual flow for 1896-1913 and records of virgin flow for 1896-1945 are those published by the U.S. Bureau of Reclamation (1954, p. 145,146). Records of 

virgin flow for 1946-66 were furnished by the Upper Colorado River Commission (written commun. 1967).

D49
D50 WATER RESOURCES OF LOWER COLORADO RIVER-SALTON SEA AREA

TABLE 7. Annual flows of the lower Colorado River, 1902-66, in millions of acre-feet

At cornCalendar year pact point, 

Ariz.

1902 

1903 

1904 . 

1905 

1906 

1907 

1908 

1909 

1910-.. ----.

1911 ... 

1912 .......

1913.. -.

1914 

1915 

1916 ..

1917-- -.-.

1918 --.

1919 

1920 

1021.. ........

1922 -. .

1923-. --.

1924 

1925 -

1926 

1927 .

1928 

1929 . 

1030 

1931 

1932 

1933 .

1934- . ---.

1935 

1936... .... ......

1937 

1938 

1939 

1940 

1941.. .......

1942 .

1943 

1944 - 

1945 

1946.... ..--.

1047

1948- ....-.-.

1949 

1950 

1951--...- .

1952.. - .

1953. - .

1954

1955 -.

1956 

1957 

1958 

1959 

I960 

1961 . .

1962 .

1063 

1964 -

1965 .

1966. --

...... ... 19.62 .

.... . 11.96 .

 -... 18.31 ..

 20.96 ..

 13.78 .

... ..... 10.57 .

-.-..... 20.10 .

on >»n

 - 16.09 .

. -... 16.97

-. ... 11.70

-. .-. 12.39

... ..... 13.08

 ... -. 17.56

 .... . 14.73

.----. 19.62

 ..... 12.41

... ..... 6.229

... . 15.17

9 7>>1

----- 3.967

 ..... 10.28

 ..... 12.14

 ..... 12.01

... ..... 15.66

.... 8.872

 . 7.617

... .... . 17.89

 . 14.81

11 44

----- 13.03

11 79

o 779

 . 14.07

19 QA

.- . . 14.62

... 10.81

 . 9.916

17 Q9

... ..... 8.748

o -loo

---.-. 6.981

.-. .... 8.667

........ 18.73

 13.17

.... ... . 7.074

...- 8.804

-.. ... 7.341

 . 14.46

 ..... 81.404

 --- 83.256

..... 89.995

.... .... . 87.710

Near Below Below Near Below Below 

Grand Hoover Davis Topock, Parker Palo Verde 

Canyon, Dam, Dam, Ariz. Dam, Dam 

Ariz. Ariz.-Nev. Ariz.-Nev. Ariz.-Calif. Ariz.-Calif.

17.98 ..

11.99 ..

12.78 ..

13.55 ..

18.24 ..

14.97 ..

19.85 ..

12.76 ..

6.594 ..

15.82 ..

10.04 ..

4.186 

10.62 

12.47

12.54 

15.86 

9.090 

8.035 

18.79

14.92 

11.62 

13.33 

12.11 

9.12

14.35 

13.01 

14.62 

10.84 

9.934

18.11 

8.803 

6.297 

7.286 

8.774

18.91 

13.46 

7.308 

9.154 

7.739

14.84 

«1.629 

83.578 

3 11. 77 

3 8.226

4.513 ..

6.359 ..

5.943 ..

6.018 ..

6.764 ..

8.645 ..

7.973 ..

14.89 ..

15.76 ..

12.72 ..

14.43 ..

12.51 -

10.58 -

10 gfj

13.05 .-

13.57 ..

12.02 

9.87

15.82 

11.30 

10.51 

8.588 

7.813

9.323

11.88 

9.282 

8.996 

8.586

8.615 

8.533 

8.159 

7.792

7.777

19.15 ..

10.83 

9.256

15.76 

11.16 

10.41 

8.836 

7.743

9.008 

11.74 

9.196 

8.763 

8.329

8.453 

8.533 

8.020 

7.735 

8.169

OA QQ

15.22 ..

12.97 -.

20.09 --

91 QQ

18.57 -

19 17

12.70 .-

12.63 ..

18.07 -

14.61 ..

19.39 ..

19 ftA

6.605 ..

15.96 ..

10.19 ..

4.316 ..

6.040 

5.675

5.768 

6.580 

8.314 

7.790 

14.51

15.36 

12.16 

13.87 

11.94 

10.23

10.71 

12.91 

13.32 

10.64 

8.973

15.56 

10.98 

10.14 

8.617 

7.519

8.882 

11.63 

9.059 

8.683 

8.035

8.288 

8.339 

8.006 

7.652 

7.863

6.091 ...

5.629 ...

5.950 ...

6.009 ...

8.417 ...

7.656 ...

14.75 -

15.20 ...

12.08 ...

13.84 ...

12.03 ...

10.14 ...

10.66 ...

12.65 ...

13.06 -

10.47 ...

8.672 ...

15.41 ...

10.65 ...

9.671 ...

S 141

6.869 ...

7.997 

10.89 

8.186 

7.794 

6.975

7.159 

7.251 

6.652 

6.356 

6.682

6.959 

9.858 

7.180 

6.533 

5.760

5.878 

5.974 

5.308 

5.224 

5.388

Below At (above) 

Cibola Imperial "5 

Valley, Dam, 

Ariz. Ariz.-Calif.

7.342 

10.35 

7.689 

7.063 

6.350

6.460 

6.504 

5.948 

5.777 

5.905

11.3 

9.87 

16.1 

17.7

24.8 

12.6 

25.3 

14.1 

17.6

18.2 

12.0 

20.6 

13.1 

18.9

19.9 

13.2 

10.5 

21.1 

19.5

16.9 

18.0 

11.6 

13.0 

12.6

17.5 

14.0 

18.8 

12.0 

6.08

15.3 

9.48 

3.69 

5.601 

4.916

5.315 

5.464 

7.840 

6.979 

14.02

14. 71 

11.35 

13.21 

11.39 

9.486

10.04 

12.04 

12.57 

9.906 

8.053

14.82 

10.05 

9.03 

7.708 

6.266

7.344 

10.50 

7.695 

7.107 

6.293

6.458 

6.522 

5.903 

5.724 

5.849

At At international boundary

Ariz. ' Northerly 2 Southerly

7.960 ....

11.33 

10.12 ....

19. 71 ....

19.48 ....

25.48 ....

13.69 ....

25.97 

14.33 ....

17.84 ....

18.36 

11.77 

20.64 

14.64 

23.14

20.61 

13.15 

10.74 

21.45 

19.44

17.02 

17.84 

11.35 

12.40 

12.20

17.12 

12.78 

17.50 

10.61 

4.831

14.20 

8.016 

2.384 

4.038 

3.465

3.995 

4.170 

6.557 

5.437 

11.73

10.48 

7.272 

6.612 

6.462 

3.804

4.243 

6.260 

6.565 

3.464 

2.764

9.192 

4.095 

3.196 

2.118 

.8812

1.167 

2.951 

.9333 

.7024 

.6830

.8605 

.9243 

.8624 

.7298 

.5888

18.5

12.1 ....

20.97

14.84 ....

23.31

20.74 ....

13.32 ....

10.91 ....

21.6

19.6

17.25

18.14

11.67

12.7

12.6 ....

17.6

13.5

18.4

11.4

5.71

15.1 ....

8.92 ....

3.224 ....

5.007

4.382 ....

4.870 ....

4.915 ....

7.381 ....

6.248 ....

12.74 ...

11.55 ....

8.310

10.10

8.001 ....

5.885 ....

6.370 ....

8.330 ....

8.770

5.810 

3.639

10.15 

5.224 

4.346 

3.058 

1.638

2.853 

5.908 

3.051 

2.338 

1.672

1.810 

1.834 

1.502 

1.524 

1.420

4.417 

2.234

8.648 

3.736 

2.697 

1.659 

.2572

1.089 

3.908 

1.312 

.5441 

.1769

.3081 

.1852 

.098 

.102 

.102

1 Above Yuma Main Canal wasteway.

2 Figures show flow reaching the northerly boundary, including flow diverted to 

Alamo Canal. Figures for years prior to 1951 are sums of flow of Colorado River at 

Yuma and return flows between Yuma and northerly boundary. Figures for 1912-33

and 1950 not previously published. Figures for 1912-13, 1920-21,1925-30 include estimates of minor return flows. 

8 Affected by storage in Lake Powell.
LOWER COLORADO RIVER WATER SUPPLY ITS MAGNITUDE AND DISTRIBUTION D51

TABLE 8. Annual flows of principal tributaries to the lower Colorado River, 1903-66, in acre-feet

Little Colorado River, Ariz. Bright Angel

At Grand Falls Near Cameron Grand Canyon, Littlefield, Ariz. 

Ariz.

1903 ____ --........

1904. _......-----.-. 

1905-.__. _..-_----_.

1908. __ -.-_..... . 

1910 __ ---..._. _ .

1912_-__. __.-_---.-.

1913....... _ . _ _. 

1914-_________...__. 

1915 ___ _ ___ ___..

1917 _____ .....___.

1918-----.... _...... 

1919...... .......... 

1920 ______ ....... 

1921. -_.....---.....

1922 __ ... _ __--_.

1923----.-.......... 

1924. __ ._....__.... 

1925. ___ .......... 

1926-. ___ ...-.-... 

1927 __ .............

1928-.... ._-._.. .

1929---_---________.

1930.....-.-.-. ..._..

1931.- _____ ..__..

1932..-.. ........-_.

1933................

1934................

1935....... __ ..._.

1936................

1937---.... _ ._....

1938... -.--_...._...

1939-- ____ . _ ....

1940.. _..._.........

1941. __ ...... ___ .

1942 __ .___.........

1943 _________ ...

1944 __ ............

1945. __ ... _ . __ .

1946--...-.-........

1947.-...--.....-...

1948................

1949 __ .--_..._..._.

1950 __ ----_..-_...

1951--------........

1952-__. ....----___.

1953_-.-----...._...

1954

1955-.. ---.._.....-.

1956--.. -.-_.._._...

1957---.. ...---_-__.

1958

1959- .---.-_-......

I960---.-. -..._..__.

1961

1962......-.-------.

1963

1964---. .._. .-_--.

1965... ._._.---_ ...

1966 __ .............

------- __ - 173,600 .. 

 .______ 390,100 ..

------- __ - 95,060 ..

-_-.--.----_ 515,600 ..

._--.__-.-._ 181,700 ..

-------- __ 197,900 ..

-_---.-_-_-. 429,800 ..

.... ____ -. 160,400 ..

.----....-.. 37,740 ..

............ 217,900 ..

....... ___ 167,900 ..

---.--._--.. 340,900 ..

--------.-.- 160,300 ..

--.--......_ 83,450 ..

.---..-..... 191,100 ..

............ 587,700 ..

............ 90,420 ..

..-----..... 102,500 ..

............ 132,600 ..

------- ___ 155,600 ..

............ 136,100 ..

. _ ---.-._. 165,700 ..

............ 130,900

............ 261,700

............ 40,190

-----_.---.- 110,200

------------ 149,700

-----.-.-.._ 18,550

---_-_-._.-_ 194,300

.-----....._ 145,400

.-----._..-. 107,300

132,600

285,400

40,400

59,380

347,600

54,420

112,700

191,400

19,260

201,500

151,600

100,800

143,200

33,650

161,300

79,020

168,900

256,300

201,000

22,560 

19,340 

31,750 

34,420

28,950 ..

21,980 ..

20,530

16,550

42,960

16,170

13,770

31,590

25,430

42,890

44,590

25,780

31,630

65,760

28,380

33,490

25,880

26,630

23,200

18,170

19,020

20,760

21,500

15,440

43,800

14,560

16,460

12,790

16,080

27,820

47,040

14,010

18,580

18,700

21,050

14,480

14,630

25,470

28,620

213,600 -.

106,000 ..

384,300 ..

116,300 ..

77,350 ..

162,200 ..

144,400 ..

234,200 ..

281,700 ..

148,700 ..

179,400

426,800

186,500

179,200

180,500

181,100

168,900

131,400

110,800

163,400

118,000

112,000

267,200

97,540

139,900

133,400

81,700

133,000

272,000

90,650

84,370

107,500

136,800

84,810

86,370

159,200

163,800

Bill Williams River, Ariz.

Near Alamo

81,090

481,500

21,910

21,900

136,300

74,120

20,730 ..

10,510 ..

7,800 ..

58,580 ..

7,150 -.

95,550 ..

157,600 -.

7,260 ..

63,460 ..

35,270 -.

6,980 ..

16,410 ..

61,080 ..

17,080 -.

23,080 ..

6,330 -.

19,080 ..

34,180 ..

32,130 ..

273,800 ..

81,390

At Planet Dome, Ariz.

29,390 

80,590 

113,800

36,710

52,800

130,300

307,100

11,840

12,400

110,400

22,250

253,200

113,000

231,200

68,670

399,200

23,930

14,220

114,900

60,000

60,990 

222,900 

3,665,000 

1,792,000 

633,800

1,112,000 

661,400 

224,000 

267,400 

232,900

73,780 

558,200 

1,946,000 

4,665,000 

1,155,000

329,700 

739,900 

801,000 

478,500 

674,100

589,700 

376,700 

77,870 

387,100 

635,400

22,910

4,870

13,630

110,700

259,500

0

169

5,910

0

153,700

45,900

3,540

0

589,700

0

0

0

0

0

420

0

0

0

6,360

1,160

958

1,460

12,110

308

223

877

3,350

17,770

11,790

3,280

7,210

103

323

39,830
D52 WATER RESOURCES OP LOWER COLORADO RIVER-SALTON SEA AREA 

TABLE 9. Annual diversions and return flows, Lake Mead to Imperial Dam, 1915-66, in acre-feet

Diversions from Lake Mead

, ToLasVegas To Boulder 

and Henderson, City, Nov.* 

Nev.i

1915_ _________________________________________

1916_ _________________________________________

1917__ _________________________ ____ ____ _ .

1918_ _________________________________________

1919_ _________________________________________

1920-- _ _ _ ____ _______ _____ __ ...

1921. _ __ ________________ _ _________________

1922__ __ ____________________________________

1923- _________________________________________

1924. _________________________________________

1925_-_______________________________________.

1926. __________ _ ____________________________

1927_ _________________________________________

1928- _________________________________________

1929 __ _______ _ __________ _ _-_----_-_.__.

1930- _ _ _ __ _ _ _ __ _ __ _ __ _ _ .

1931_ ____________ _ __________________________

1932__ ___________________________________ _ .

1933_ _ _______________________________________

1934__ ___ ___________________________________

1935. _________________________________________

1936-__-_ -. _ __ _ ____ ___ _ ___ _____

1937_ ______________________________________

1938-- ___ _ ________________________________

1939 _ __ ____ __ -_______-_-___-__.______

1940 _ _ _ __ _ __ ___ ___ __ __ _ ___

1941 _ ___ _ __ _____

1942_ __________________________ 2,950

1943 _ _ _ ___ __ ______ __ 16,990

1944___.__ __ __________________ 12,880

1945- __________________________ 6,360

1946- __________________________ 5,392

1947 _________ __ ___ __ _ _ 6,132

1948- __________________________ 4,868

1949 __________________________ 4,511

I960. __________________________ 5,718

1951___ ________________________ 6,764

1952- __________________________ 8,533

1953__ _________________________ 11,050

1954_ __________________________ 17,140

1955. __________________________ 17,750

1956__ _________________________ 21,700

1957. __________________________ 18,020

1958. __-_.___-.-___________.___ 17,780

1959_ __________________________ 16,500

I960- _________________________ 18,070

1961- __________________________ 19,110

1962. __________________________ 21,360

1963. __________________________ 24,490

1964_ __________________________ 22,300

1965. __________________________ 19,890

1966. _________________________________ ____

705 .

700 .

780 .

833

999 

1,038 

1,400 

1,730 

1,585

1,552 

1,682 

1,737 

1,921 

2,047

2,163 

2,303 

2,545 

2,592 

2,742

2,575 

2,743 

2,376 

2,435 

2,593

2,627 

2,369 

2,626 

2,721 

2,992 

2,762

To Metropolitan

Calif.'

172,500

95,710 

30, 700 

31,140 

34,630 

51,630

58,350 

80,400 

85,360 

194,200 

178,600

179,400 

231,400 

175,100 

228,300 

341,200

417,100 

481,500 

595,200 

540,200 

707,900

894,200 

1,103,000 

1,073,000 

1,057,000 

1,137,000 

1,178,000 

1,146,000

Colorado River Indian 

Reservation, Ariz.

Diversion *

7,290 _.

9,380 _.

9,440 ..

16,010 _.

18,500 _.

20,350 _.

15,340 _.

18,620 _.

23,480 _.

25,440 _.

26,000 ..

32,960 ..

27,680 _.

30,330 ..

29,040 _.

27,640 _.

25,000 _.

21,440 _.

18,010 _.

21,190 _.

23,230 -.

30,360 ..

33,600 _.

29,190 ..

25,030 ..

37,390 _.

30,320 _.

56,320 ..

79,130 ..

113,900 _.

101,600 ..

105,700 

124,700 

134,800 

161,000

209,700 

243,600 

278,200 

314,300 

341,900

323,000 

307,600 

320,900 

367,500 

378,000

412,800 

438,600 

466,800 

484,500 

455,600 

416,700 

461,200

Return flow '

13,700 

25,900 

31,600 

42,500

51,400 

81,500 

93,500 

104,800 

109,000

118,900 

112,300 

159, 100 

208,800 

212,500

227,400 

267,700 

288,600 

298,500 

275,700 

253,100 

259,800

Palo Verde Valley, Calif.

Diversion Return flow

131,100 __

180,500 __

225,700 __

212,000 __

213,800 __

169,600 __

201,700 __

179,600 ._

181,500 __

162,500 _.

164,600 _.

194,400 __

194,300 ._

225,400 ._

220,500 ..

226,700 __

253,600 _.

360,200 ._

305,300 __

340,100 __

313,200 __

335,400 _.

331,400 _.

408,700 _.

484,800 _.

558,900 __

652,700 ._

767,700 __

705,800 __

728,800 ._

765,600 __

861,100 .-

811,700 _.

947,100 _.

824,400 _

873,900 __

916,800 __

918,600 __

943,200 

952,800 

929,800 

727,900 

774,000 

799,300

550,000 

580,400 

572,800 

530,100 

424,600 

431,200

1 Pumping began in 1942.

2 Pumping began in 1932. 

8 Pumping began in 1939.

 Figures shown for 1915-36 are for fiscal years ending June 30 (U.S. Qeol. Survey, 

1964). Diversions began in 1870.

 Flow began in 1946.

 Diversions began about 1879.
LOWER COLORADO RIVER WATER SUPPLY ITS MAGNITUDE AND DISTRIBUTION 

TABLE 10. Annual diversions and return flows at and below Imperial Dam, 1908-66, in acre-feet

D53

Gila North All Yuma 

Gravity Gila American Canal

Main Valley Canal at 

Calendar year Canal at Canal at near Laguna 

Imperial Laguna Imperial Dam* 

Dam i Dam * Dam *

Reservation Di- Yuma 

vision of Yuma Main 

Project, Calif. Canal 

Waste; 

Diver- Return way 7

sion flow 6

Yuma Valley, Ariz.

Yuma Return Flow 

Main flow to across above 

Canal river 8 southerly Pilot 

below bound- Knob 

siphon» ary w Waste- way"

All Pilot

American Knob

Canal powerAll Alamo 

Coa- American Canal 

chella Canal at head 

plant Canal below (Morelo 

and at head u Coachella Dam) 1S 

Waste- Canal « way*

1908.......................................................

1909.......................................................

1910............................................ 4,000

1911............................................ 25,290

1912............................................ 69,050

. . ....... ...... 709,700

.. .-..............-.....-.. - . - 800,700

 932,800

..... .................. .... -.- 1,353,000

...........-. ................-....... ......... 1,434,000

............ ................... ..... ...... 1,667,000

........................................ ......... 1,863,000

......................... ............... -..... 1,913,000

.-. .. ..-..-.. - .. . 2,219,000

 . . -... .. . .. . . 2,270,000

......................... ........... . .. 2,719,000

.... ........._... ............... ..- 2,657,000

 2,822,000

. . ..... .......... ........ .......... 2,420,000

................................................... 2,890,000

..... .................. .... .. ..- 3,275,000

75,820 .- -...... .. .-.. ... - - 3,078,000

74,090 ... ...... ..-. - .- - - 3,159,000

75,320 ....._....----..-.--- .----....-----..-. 3,091,000

83,750 ._-....-. .....---- . - - 3,089,000

.... .................. -....... . ... 3,272,000

. ........--..-......-- ---- --.- -- 3,424,000

............................................. .. 3,281,000

. . . ..............-.. .... 2,693,000

53,380 ...... .....-...-.-.--.--.....---------- 2,562,000

1913............................................ 337,400

1914........ ................................. 520,000

1915........ .......................-......... 439,600

1916............................................ 390,700

1917... ...................................... 452,500

1918............................................ 467,400

1919-........................................... 478,100

1920........................................... 468,900

1921............. ............................ 482,000

1922............................................ 546,600

1923............................................ 672,900

1924............................................ 665,600

1925............................................ 647,100

1926............................................ 704,700

1927- . . 949,500

1928 ...................................

1929... .............................

1930......................................

1931......................................

8,920

12,490

13,200

20,190

15,910

17,860

18,950

10,690

11,640

11,740

1933 .........................................

1934............................................

1935............................................

1936 .................... 50,000 ..... ...

1937. . 54,000 .... ...

1938....................... 49,000 793

1939.... 48,000 58,140

1940 46,000 180,900

1941 38,000 1,910,000

1942....................... 40,000 3,965,000

1943. ......... 27,380

1944.. ........ 60,920

1945.... ...... 98,080

1946............. 146,600

1947 ... 144,600

35,000 3,942,000

37,000 4,423,000

36,000 4,452,000

40,000 5,404,000

42,000 5,532,000

1948............. 148,900 .......... 5,558,000

1949.- ..... 134,700 .......... 5,827,000

1950............. 150,200 ....... 6,250,000

1951............. 183,400 ...... . 5,066,000

1952 ......... 281,100 .......... 5,302,000

1953-..-... .. 399,800 ....... 5,467,000

1954. 472,900 75,000 5,278,000

1955............. 578,700 .......... 5,024,000

1956............. 619,500 .......... 4,767,000

1957............. 652,600 .......... 5,524,000

1958............. 728,200 .......... 6,823,000

1959............. 788,900 .......... 5,978,000

1960.--.-........ 794,400 .......... 5,652,000

1961............. 818,400 .......... 5,037,000

1962............. 880,200 .......... 5,068,000

1,182,000

1,234,000

1,320,000

1,293,000

1,330,000

1,368,000

1,226,000

1,368,000

1,370,000

1,300,000

1,169,000

1,243,000

1,314,000

778,400

79,250

77,780

76,210

340,700

90,330

77,960

24,990 35,690

60,390

65,180

77,750

82,250

82,740

85,520

88,250

82,680

77,400

91,460

95,210

91,340

97,800

1963............. 916,200 .......... 5,040,000 ........... 96,220

1964............. 896,200 .......... 4,566,000 ........... 96,500

1965 .. .. 852,600 .......... 4,562,000 ........... 84,770

1966 . 880,000 .......... 4,694,000 ..... 91,890

10,000

12,000

12,000

12,840

13,410

23,640

24,170

41,610

42,930

33,550

32,070

37,990

45,970

55,980

59,560

60,990

61,330

69,400

71,510

76,130

71,180

72,280

69,620

65,100

61,390

54,760

50,440

51,640

51,490

51,310

46,990

40,690

39,290

313,500

185,900

146,800

114,900

152,500

151,300

149,900

176,900

219,600

289,800

307,100

274,500

352,500

496,500

728,000

841,200

815,600

879,700

913,700

890,600

829,800

957,200

905,100

861,500

731,400

776,900

786,600

959,400

1,025,000

1,014,000

1,043,000

794,500

1,012,000

1,040,000

943,000

1,042,000

980,100

854,000

967,400

984,500

1,006,000

851,000

653,300

817,400

1,023,000

1,001,000

754,100

470, 700

75,950

115,900

105,900

131,700

121,700

272,900

283,800

272,100

349,200

298,900

280,300

323,400

343,400

343,300

331,000

265,800

280,000

333,500

350,300

346,900

372,200

405,000

336,000

370,300

400,400

376,900

378,700

388,700

397,200

403,300

396,600

360,700

375,500

385,000

357,700

344,300

330,900

318,100

306,200

338,000

329,400

338,900

351,000

355,900

343,200

335,600

314,300

318,100

59,660

65,280

61,090

97,840

102,300

110,200

108,800

73,070

101,000

77,560

31,580

55,900

36,060

61,050

49,690

83,000

103,400

65,140

92,350

91,060

86,930

76,450

77,420

76,290

81,340

85,260

47,440

35,280

39,760

46,180

37,550

38,740

29,500

34,630

36,520

31,250

28,100

26,250

23,790

25,480

14,630

8,867

7,570

44,410

29,380

34,140

52,180

57,050

91,430

95,790

92,120

95,760

103,600

26,850

133,000

1,217,000

2,502,000

104,100 2,455,000

103,200 2,958,000

82,470 3,459,000

91,600 3,957,000

110,300 3,981,000

127,500 4,028,000

110,200 4,185,000

98,860 4,676,000

105,400 3,651,000

118,100 3,781,000

117,800 3,935,000

118,200 3,711,000

117,400 3,593,000

119,300 3,525,000

132,100 4,162,000

147,500 5,316,000

145,500 4,485,000

145,600 4,386,000

144,900 4,022,000

147,000 4,421,000

149,000 4,398,000

143,200 3,993,000

134,800 3,203,000 .

128,000 3,366,000

21,460

0

780

0

0

408,300

705,700

1,023,000

1,030,000

1,064,000

1,111,000

1,305,000

0

0

24,630

90

115

10,500

805,000

1,945,000

1,036,000

765,000

441,400

794,400

700,400

585,500

2,746,000

2,050,000

3,141,000

3,660,000

3,872,000

3,737,000

3,502,000

3,454,000

2,241,000

955,800

..........--.. .. 1,152,000

17,600 2,445,000 1,107,000

150,000 2,516,000 1,065,000

128,000 2,697,000 1,255,000

109,200 2,633,000 1,297,000

164,800 2,699,000 1,324,000

197,800 2,762,000 1,313,000

346,500 2,939,000 1,434,000

487,900 3,067,000 1,463,000

495,600 3,203,000 1,381,000

525,400 3,353,000 1,524,000

561,800 3,096,000 1,628,000

572,100 2,927,000 1,445,000

547,800 2,907,000 1,396,000

498,200 2,782,000 1,696,000

491,900 2,731,000 1,962,000

492,900 2,840,000 1,747,000

493,300 2,984,000 1,771,000

508,300 2,957,000 1,484,000

554,400 2,951,000 1,489,000

525,300 2,991,000 1,601,000

503,400 2,770,000 1,408,000

501,500 2,624,000 1,427,000

468,100 2,818,000 1,403,000

i Flow began in 1943.

* Served North Gila Valley, Ariz. Flow began about 1912, and the canal was sealed 

about 1954. Annual flows were estimated; those for 1948-53 are not considered to be 

reliable. Figure for 1954 is from unpublished records of the Imperial Irrigation District.

» Flow began in 1938.

« Served all or parts of the Yuma Project (Reservation Division, Calif., and Yuma 

Valley, Ariz.). Flow began in 1910, and the canal was sealed in 1948.

s Sum of several small diversions from All American and Yuma Main Canals. 

The Yuma Canal supplied additional, unknown quantities of water to the Reservation Division prior to 1949. First diversion about 1910.

6 Flow began in 1912. Sum of flows in Reservation Main drain (California drainage 

canal) and Drain 8B (Araz drain), in which flow began in 1948.

' Return of water diverted primarily for power generation or delivery to Mexico 

rather than irrigation in the United States. Flow in the Yuma Main Canal began 

about 1912; in Pilot Knob, 1939.

«Flow began in 1912. Diversions to Yuma Valley by pumping from Colorado River 

at Yuma (the principal supply for the valley from 1907 to 1912) were as follows: 1907 

7,160; 1908 23,160; 1909 48,980; 1910 42,010; 1911 47,280; 1912 26,830; 1913 1,180.

»Flow began about 1913. Sum of flows in Cooper (flow began in 1927), Eleven-mile 

(flow began about 1913), and Twenty-one mile (flow began in 1939) wasteways.

w Flow began about 1914. Sum of flows across boundary in East Main Canal (flow 

began about 1914), Main Drain (flow began in 1917), and West Main Canal (1924-44).

» Flow began in 1939. Subtract flow in next column to obtain the diversion to 

Imperial and Coachella Valleys, Calif.

v Flow in Coachella Canal began about 1944; in All American Canal, about 1940. 

Records furnished by Imperial Irrigation District.

" Flow began in 1901. Figures for 1951-63 furnished by the International Boundary 

and Water Commission. The figures listed above include water diverted from Colorado River at or near the site of Morelos Dam and water delivered through the All 

American Canal and Pilot Knot wasteway. Additional diversions to Alamo Canal 

from Colorado River at Volcano Lake, in Mexico, were made as follows: 1916 17,310; 

1917 142,400; 1918 157,700; 1919 197,500; 1920 274,400; 1921 115,400.

NOTE. Return flow through the Wellton-Mohawk Main Outlet drain began in 

1961. Annual flows, in acre-feet, for the calendar years 1961-66 were as follows: 139,700; 

215,100; 200,700 ;181,000; 186,100: and 216.900.
D54 WATER RESOURCES OF LOWER COLORADO RIVER-SALTON SEA AREA

TABLE 11. Year-end usable contents of reservoirs below compact point, 1934-66, in thousands

of acre-feet

Calendar year

1934... ..___.._.

1935... -_-_-_.__

1936-__-_----__-

1937... ...___.._

1938 _________

1939 ---------

1940 -_--__-__

1941............

1942_.._......_.

1943 -_----___

1944... _...____.

1945 -.-_-_-__

1946 -..._. ...

1947 ---_-_.__

1948.. _-._..._-.

Lake 

Mead«

0 .

3,673 .

3 6, 339 .

12, 248

20, 394

20, 562

20, 320

24, 090

23, 040

21, 670

20, 310

19, 720

17, 904

20, 645

19, 908

Lake 

Havasu 2

0

481. 5

518. 2

411. 0

406. 3

496. 1

579. 1

578.7

576.7

621. 0

603.8

596. 5

Calendar year

1949. __ ..-._

1950______-_-

1951. .__-_-..

1952.........

1953.. ____...

1954___. _ _.

1955_. -_._-__

1956-----_-_-

1957.. ._.._._

1958---------

1959____-___-

1960.. ._.._._

1961-.-------

1962__-______

1963-_---_-_-

1964... -_-_--

1965__ _--_--

1966.- _ _ _

Lake 

Mead '

19, 900

18, 259

17,846

19, 780

17, 000

12, 750

11, 394

11, 951

20,842

21, 973

19, 553

19, 286

18, 025

22, 980

16, 007

11, 136

15, 233

15, 481

Lake 

Mohave

0

1,030

1,596

1,610

1,695

1,701

1,439

1,474

1,595

1,649

1,657

1,620

1,682

1,699

1,553

1,588

1,738

1,574

Lake 

Havasu 2

667.7

614.8

636.0

582.4

615.4

612. 3

605. 5

546. 3

539. 8

547.7

555.2

549.9

541.6

540. 0

534. 8

539. 3

556.7

538.4

1 Figures of contents prior to 1949 are based on a survey completed in 1940; those after Oct. 1, 1949, are based on a 

survey made during 1948-49.

2 Figures of contents prior to 1956 are based on the original survey of Lake Havasu; those after Oct. 1,1956, are based on 

a resurvey of the upper 20 feet in 1957.

3 Usable contents were reduced 3,207,000 acre-feet May 1,1936, by permanent closing of temporary outlet gates.

TABLE 12. Approximate irrigated acreage in principal water-using areas for selected years

[Data for 1914-50 from U.S. Bureau of Reclamation (1953), acreages outside irrigation districts and Indian reservations in 1962 were determined by a land-use survey (U.S. 

Bureau of Reclamation, 1963); acreages in Yuma Mesa and Reservation Division, 1955, and for North and South Gila Valleys, 1960-65, are from unpublished crop reports 

by U.S. Bureau of Reclamation. Acreages for Yuma Valley, 1960, and for Imperial and Coachella Valleys, 1955-60, are from Colorado River Board of California (1962); 

those for Imperial and Coachella Valleys, 1965, from crop reports of respective irrigation districts, and for Colorado River Indian Reservation, 1960-65, from crop reports 

of Bureau of Indian Affairs. Other data from Geological Survey reports on surface water of the United States]

Name of area 1914 1920 1925 1935 1940 1945 1950 1955 1960 1965

Colorado River Indian Reservation, Ariz. _ __ . _ .

Palo Verde Valley, Calif....................... .......

North and South Gila Valleys, Ariz.» _ ................

Wellton-Mohawk area, Ariz.2 .. _____ . ____ ... _ .

Yuma Mesa, Ariz.3 __ .....

Yuma Valley, Ariz __ ... __ . ___ ... ___ ... __ .

Imperial Valley, Calif ________ .. __ ... ____ .

Coachella Valley, Calif.4 ____ ___ . . . _ .

........ 460

........ 30,700

........ 400

........ 19,800

... - 5,370

4,030

30,700

1,080

0

42,900

11,700

5,280

33,600

3,630

670

43,600

12,300

359,000

6,250

26,000

5,440

1,400

45,600

10,300

439,000

3,870

25,000

5,420

1,380

44,700

8,030

404,000

4,230

34,400

8,100

1,470

44,200

7,310

417,000

6,890

41,700

7,070

1,620

45,400

8,150

394,000

0

22,100

55,100

15,300 .

0

9,230

47,400

8,830

430,000

11,100

27,600

70,300

31,000

17,200

45,500

10,200

475,000

47,700

28,000

75,900

17,600

54,100

19,800

45,600

10,600

434,000

55,500

31,900

84,300

16,700

58,000

20,200

46,300

10,600

433,000

59,900

irrigated by pumping from the Colorado River or from wells near the river. Because of differences in methods of reporting irrigated acreage, some of the acreages may not be 

strictly comparable with other acreages in this table or with similar acreages published elsewhere.

1 Acreages shown include those irrigated by pumping from wells in South Gila 

Valley.

2 Acreages shown were irrigated with Colorado River water. This area was irrigated first by diversions from Gila River and later by pumping from wells. In 1943

about 7,800 acres were irrigated with ground water, but use of ground water ceased 

before 1960.

3 Acreages include those in Yuma Mesa Auxiliary Division (unit B).

4 Acreages irrigated with Colorado River water. Ground water was used in other 

parts of the valley.

U. S. GOVERNMENT PRINTING OFFICE : 1969 O - 321-230