AZ vs. CA:24 California Exhibits, Vol. XXIV; Miscellaneous

page 7

PROBLEMS OF IMPERIAL VALLEY AND VICINITY. 7 would constitute a serious menace to the water supply of the present irrigated lands in the Imperial and Yuma valleys unless a large amount of storage be provided. For full development of all the lands that can be reached by gravity and reasonable pumping lifts on the Lower Colorado River large storage capacity will be required, estimated at about. 6,000,000 acre-feet, if provided by a reservoir below the Grand Canyon of the Colorado. If storage is provided above the Canyon, this must be increased by at least 2,000,000 acre-feet on account of the unavoidable losses due to the impossibility of regulating the flow in exact accordance with the needs of irrigation from a reservoir so far distant, and for other reasons. This Capacity can be somewhat reduced if the acreage be reduced by cutting off the more doubtful and less^ desirable areas which have been included. To remove the menace of flood from the Colorado River will require a much larger storage capacity than that above given. Owing to the gradual upbuilding of its deltaic bed and banks the flood menace from the Colorado River is an increasing and ever-rectir-ring problem of great importance. The Gulf of California formerly extended northwestward to a point a few miles above the town of Indio, about 144 miles from the present head of the gulf. The Colorado River, emptying into the gulf a short distance south of the present international boundary, carried its heavy load of silt into the gulf for centuries, gradually building up a great delta cone entirely across the gulf and cutting off its northern end, which remains as a great depression from which most of the water has been evaporated, leaving in its bottom the Salton Sea of 300 square miles, with its surface about 250 feet below sea level. The river flowing over its delta cone steadily deposits silt in its channel and by overflow on its immediate banks^ so that it gradually builds up its channel and its banks and forms a ridge growing higher and higher until the stream becomes so unstable that it breaks its banks m the high-water period and follows some other course. In this manner the stream has in past centuries swung back and forth over its delta, until this exists as a broad, flat ridge between the gulf and the Salton Sea, abou^ 30 feet above sea level, and on the summit of this has formed a small lake, called Volcano Lake, into which the river flows at present, the water then finding its way to the southward into the gulf. The direct distance from Andrade on the Colorado River, where it reaches Mexico, to the head of the gulf is about 75 miles, and the distance to the margin of Salton Sea is but little more. As the latter is about 250 feet lower than the gulf, the strong tendency to flow in that direction needs no demonstration. This, coupled with the inevitable necessity for such an alluvial stream to leave its channel at intervals, constitutes the menace of the lands lying about Salton Sea, called the Imperial Valley. . As tliere i,s no escape of water from Salton Sea except by evaporation, the river flowing into this sea would, unless diverted, gradually fill it to sea level or above and submerge the cultivated land and the towns of Imperial Valley, nearly all of which are below sea level. Any flood waters that overflow the bank to the north must therefore without fail be restrained and not allowed to flow northward into Salton Sea. This is now prevented 93716-S. Doc. 142,67-2--2