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<Cl N = N ';/"--~ ~:}~ River (see table 5 for pertinent dats for these projects snd plate 2 for their locations). They control practically all inflow to Lake Mead, except side inflow and flow entering the reach of the Colorado River between Lakes Powell and Mead. Of these projects, Lake Mead is the regulating reservoir for flood control and the only reservoir having specific storage space allocated to flood control. The construction of Hoover Dam resulted in regulation of the Colo- rado River from Black Canyon to the Gulf of Californis. Painted Rock Dam (existing) on the Gila River and Alamo Dam (lUlder construc- tion) on the Bill Williams River will regulate most inflow to the Colorado River below Hoover Dam. Before completion of the upstream dallLS it had been estimated that deposited sediment would deplete the entire storage capacity of Lake Mead in about 450 years. In the future, the Little Colorado and Virgin Rivers will bring in most of the sediment that Lake Mead receives, and depletion of its storage capacity will be much slower. '. 15. Wster is released through Hoover Dam to meet the irrigation requirements for hlUldreds of thousands of acres of agricultural land in the lower Colorado River Valley and the Imperial and C08chelJ.a Valleys. The Colorado River aqueduct of the Metropolitan Water District of southern California supplies water to 93 incorporated cities and large areas of unincorporated territory having a total population exceeding 7,500,000 (1961). Power production from the project has stimulated the industrial growth of the entire Pacific Southwest. The vast Lake Mead National Recreational Area created by the dam is visited by about 4,000,000 people each year. OPERATION 1.6. General. --The following section, which pertains to the flood-control operstion of Hoover Dam, contains a description of the design operation plan and the current operation plan, together with supporting data. Application of the current operation plan to the 1884, 1917, and 1952 spring snowmelt floods and to the maximum probable spring flood, maximum probable rain flood, and standard project rain flood is also discussed in this section. 17. Design operation plan. --The design operation for Hoover Dam is described in the report by E. B. Debler titled, "Hydrology of the Boulder Canyon Reservoir," dated 31 January 1930. Operation by this plan involves drawing the reservoir water surface down accord- ing to a fixed-rule curve. Commencing 1 October, releases are ad- justed so that by 1 April 9,500,000 acre-feet of flood-control stor- age space will be available below elevation 1,229 (top of flood- control pool) to control spring snowmelt floods. In accordance with this plan, 2,500,000 acre-feet of flood-control storage space below 5