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""' C\1 ~ N C elevation l,229 is maintained during August and September for use in controll.ing rain floods. The following table specifies the minimum flood-control storage space necessary, for the dates shown, accord- ing to Debler's operation plan: :{5~j.;- Minimum flood- " Minimum flood- Date 'control storage .. Date control storage space below .. space below elevation 1,229 " elevation 1,229 .. " Acre-feet .. Acre-feet 1 August.......: 2,500,000 .. 1 January......: 5,850,000 1 September....: 2,500,000 '. 1 February.....: 7,260,000 1 October......: 2,500,000 .. 1 March........: 8,445,000 1 November.....: 3,175,000 .. 1 April.. .. .. .. : 9,500,000 1 December~.... : 4,463,000 .. .. .. 18. Reservoir capacities required for flood control, as deter- mined by Debler, were based on the best available estimate of the 1884 flood modified to account for changes in hydrologic conditions since 1884. In order to control the 1884 flood under Debler's oper- ation plan, maximum releases of 75,000 cubic feet per second would be necessary. It should be noted that the flood-control storage space includes 1.218 million acre-feet above the top of the spill.way gates in the raised position. With the reservoir water surface at the top of the flood-control pool, a discharge of about 65,000 cubic feet per second would be passing over the spill.ways. 19. Downstream channel. --The channel capacity and downstream structures from Hoover Dam to the Mexican border are shown on plate 3. Maximum nondamage capacity is 30,000 to 40,000 cubic feet per second. The Colorado River Front Work and Levee System, United States Bureau of Reclamation, Region 3, under the direction of the River Control Engineer, is continually improving the channel below Hoover Dam. The ultimate aim is to reach a capacity of 70,000 cubic feet per second. The channel is currently being dredged in the Cibola Valley reach. Future plans include dredging in Topock Gorge, the lower Parker Vall.ey, and Yuma Vall.ey. Because the water impounded behind Davis Dam almost reaches to Hoover Dam, releases from Lake Mead can exceed 40,000 cubic feet per second for short periods. Ex- tended releases above this value are not feasible because the reser- voir behind Davis Dam is relatively small. (total capacity 1,818,300 acre-feet at high water-surface elevation 647.0, including 8,500 acre-feet dead storage) compared to Lake Mead, and usually is main- tained near capacity. 6