The Colorado River Study

Document: Department of the Interior Information Sheet, "Paper By Floyd E. Dominy, Commissioner of Reclamation, Department of the Interior, for Delivery at the American Water Works Association Conference in Detroit, Michigan, June 7, 1961," June 7, 1961, page 2The Colorado river flows between Arizona and California into Mexico and the Gulf of California, but its headwaters are 1,400 miles upstream in the high mountain country of Colorado. It drains an area of 242,000 square miles--one-twelfth of the area of the continental United States--and 2,000 square miles in Mexico. The Salton Sea Basin, below sea level, in southern California which includes the fertile Coachella and Imperial Valleys is outside the natural drainage basin of the Colorado River but is dependent on the river for its entire water supply. The vast metropolitan area of southern California also receives a major share of its water supply by pumping from the Colorado through a 300 mile aqueduct. The Colorado River Basin has a lower average rate of precipitation than any other river basin in the Nation except for a few closed basins without outlet to the sea. However, the annual precipitation varies widely in different parts of the basin. Along the Mexican border near its mouth it averages only about 2.5 inches while in the higher mountains in Colorado, Wyoming, and Utah, the average is around 40 inches. The runoff of the river also varies greatly, not only from season to season but from year to year. For example, the maximum yearly runoff at Lees Ferry, which is the division point between the upper and lower basins, was in 1917 when 21,825,000 acre-feet of water was recorded. Contrast this with 1934 when the minimum flow of record was only 4,397,000 acre-feet. For you uninitiated, an acre-foot represents 325,850 gallons of water. The low average precipitation and the rugged terrain that characterize much of the Colorado River Basin account for the relatively slow development rate of the past. The average population density in the basin is only about one-tenth of the national average. In this basin agriculture and irrigation are almost synonymous. Successful crop production, with reliance only upon rainfall, is of negligible importance. Yet most irrigation developments are relatively costly and complex. With one or two notable exceptions, the larger irrigation undertakings have required participation of the Federal Government through the Bureau of Reclamation. Great strides have been made in the half century of Federal participation but the job is still far from completed. It is natural that irrigation in the Colorado River Basin began on the largest scale in the broad fertile valleys near the river's mouth in California and Arizona where a year-round growing season prevails. It was a simple matter to divert the water from the rim of the Imperial Valley for the irrigation of lands on the valley floor which is below sea level. As irrigation expanded, however, problems multiplied. In 1905 the Colorado, swollen by flood waters from the Gila, broke through a cut in its bank and for 16 months poured its entire flow into the Imperial Valley causing millions of dollars in damage. By great effort the break was repaired and the river returned to its regular course. 2Epson Perfection 4870 Photo, 400 dpi, 8 bit, 2,195,427 byte