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 Page Page Abstract_ _ _______________________________________ Dl Distribution of Colorado River water_______________ D24 Introduction. ______________________________________ 2 Gross diversions._______________________________ 24 The lower Colorado River and environs_____________ 2 Net diversions________________________________ 26 Water-control and distribution systems____________ 8 Distribution of flow during 1961-63---_---__------ 27 Legal controls._________________________________ 10 Water use and water loss____-----__--_-_-_---__- 29 Studies of the water supply._________________________ 11 Colorado River at compact point, near Lees Ferry, Conveyance losses from large canals _______ 30 Ariz___________________________________ 12 Lower Colorado River area Davis Dam to Actual flow, 1896-1966___________________ 12 Mexico ____________-____-_____--_-__--_-- 30 Man-caused depletion above compact point. ___ 12 Salton Sea basin. _________________-_-_-_---_ 33 Virgin flow, 1896-1966____________.___ 13 Interrelation of surface water and ground water. _______ 34 Probable future virgin flow_________________ 14 Deficiency of the Colorado River supply...____-_----_- 34 Probable future regulated water supply______ 17 References _____________-___-_---_--_-___--------_-- 36 Colorado River between compact point and Davis Appendix.____________---_---_---------_----------- 37 Dam.___________________________________ 19 Colorado River Compact, 1922.____-_-______-__-- 39 Gains and losses.___________________________ 20 Rio Grande, Colorado, and Tijuana Treaty, 1944___ 42 Effects of storage below compact point- _______ 21 Colorado River and tributaries below Davis Dam_ 21 Decree of the U.S. Supreme Court, 1964, Arizona v. Bill Williams River_______________________ 21 California, Colorado River--.....--------------- 45 Gila River.._______________________________ 22 Tables of basic data ___-___________-____--_-- 49 Colorado River below all major diversions.___. 23 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 the principal diversions to Mexico (via the Alamo Canal) were entirely on (a) the virgin flow at compact point (Lee Ferry), 240,000 acre-feet and 1,800,000 acre-feet, respectively. As a near Lees Ferry, Ariz., (b) the depletion of that flow caused by result of such increases in water use and the predominately be­ storage above compact point and use of water in the upper low average runoff since 1930, flow into the Gulf of California Colorado River service area, and (c) the provisions of the has diminished to negligible quantities in recent years. Future Colorado River Compact for release of water to the lower distribution of the available water supply in accordance with the river. U.S. Supreme Court decree of 1964 will permit a large increase in The computed average annual virgin flow at compact point the amount of Colorado River water used in Arizona and will for the 71 water years 1806-1966 is 14,900,000 acre-feet, but require a decrease in the amount used in California, at least for the 34 years, 1931-64, it is only 12,900,000 acre-feet. During during periods of below-average runoff. the decade 1953-62 the virgin flow was depleted about 2 mil­ The beneficial use of water below compact point is accom­ lion acre-feet per year by diversion and use in the upper service panied by large losses, some avoidable and some unavoidable. area. These depletions increased sharply after 1962 and probably Evaporation from the Colorado River and from reservoirs con­ will continue to increase for many years. sumes more than a million acre-feet per year, and nearly worth­ Probability and storage analyses indicate that the water supply less native vegetation consumes more than half a million acre- derived from the Colorado River system above compact point feet. Seepage from large canals between Imperial Dam and the to meet all demands for depletion above that point and release to areas served amounts to about half a million acre-feet, some of the lower river can be sustained at about 13 million acre-feet, which is being recovered or is recoverable. Considerably more and that 14 million acre-feet will be available most of the time. than a million acre-feet per year drains to the Salton Sea. Al­ The division of this gross supply between the upper and lower though drainage is necessary to maintain productivity of the service areas depends in part on the existence of facilities to land and is also essential to the continued existence of the sea, enable use of the water in the upper service area and on pro­ much of this water can be considered a loss from the standpoint visions of the Colorado River Compact. The actual flow at com­ of irrigation. Annual deliveries of water to Mexico during 1961- pact point probably will exceed compact requirements most of 63 exceeded treaty requirements by about 400,000 acre-feet, which the time until the upper service area's development of water can be considered a loss to the United States. supplies progresses considerably and also during subsequent With no new importation of water to the lower Colorado periods of abundant runoff. River and with natural water yields similar to those of 1931-64, Below compact point, the losses associated with storage and any new diversions from the river will depend chiefly on redis­ transport of water exceed the inflow from