Page 124


Page 124
Colorado River problem
Is Part Of,8
Full text
KELLY ON THE COLORADO RIVER PROBLEM 429 The flooding of the railroad, of the Town of Needles, and of 40,000 acres of supposedly irrigable land was believed to be involved in developing a reservoir capacity limited to 1,500,000 acre-ft. On these premises, it was concluded:* "In view of the existence of several reservoir sites below and of the damage which would occur from the construction of a dam at Blue Canyon (Mohave Canyon), it is believed that this valley near Needles (Mohave Valley) can be more profitably utilized by irrigation from diversion canals (than as a reservoir)." If the premises were correct one could easily agree with the conclusion, which, as it should be, was based on the greatest measure of profit to be obtained from the resources involved. It was not reported as "infeasible" despite Mr. Davis' statement that it was "unanimously regarded as infeasible." For a reservoir, the Valley is unusually well shaped; the floor is quite flat and the banks rise steeply from it so that it can be used without creating much shallow water. With a dam 180 ft. high reserving 4,000,000 acre-ft. for flood control, the depth of water at the upper end of Mohave Valley at maximum draw-down would be about 90 ft., and at the upper end of Cotton-wood Valley about 40 ft. This cannot properly be termed a shallow reservoir. Under the heading, "Wanton Destruction of Valuable Storage" (page 387), Mr. Davis argues that storage at Boulder Canyon must be reserved for silt. On the basis of 100,000 acre-ft. of silt per year, the smaller Boulder Canyon Dam suggested by the writer would hold the entire deposit for a period of 100 years. The power dams above would hold at least as much more. No sufficient study of the silt problem has yet been made; probably storage will always be the cheapest way of taking care of it. If the silt problem were to control, no dam above Boulder Canyon should be built until Boulder Reservoir had filled to the maximum for comfortable operation. Then the next dam up stream should be built and allowed to fill, and so on. Such a program would run over a period of several hundred years and would be intolerable. Although silt will add to the expense of using Colorado water for domestic, irrigation, and power purposes, it will not prevent that use provided sufficient storage can be maintained to regulate the flow. As nearly all the silt enters the river below the San Juan, storage above that point will be little affected, Ultimately, at least in theory, all storage below the origin of silt will fill, and the only regulation of flow will be that which can he obtained above that origin. The silt problem is a strong argument for seeking regulatory storage above the San Juan, but not for excessive storage at Boulder Canyon. It is quite certain that complete desilting at Boulder will greatly accentuate the ever-present tendency to erode banks and to pick up a heavy load of silt from the vast quantities now stored in the bottoms along the 300 miles between that point and Yuma. Under the heading, "Proper Plan of Development" (page 387), it is encouraging to note that Mr. Davis-gives consideration to adapting his Boulder Canyon project to a full development of the lower river. Perhaps he will eventually come to consider also the upper river and to give proper weight to the regulatory storage that can and will be provided, there. The only regulatory ----------------------------------------------------------------------------------------------------------------------------—— * First Annual Report, U. S. Reclamation Service, pp. 113 and 114.

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