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<br />DOL~66 <br /> <br />. <br /> <br />. <br /> <br />-/ .' <br /> <br />Background <br /> <br />.' . <br /> <br />As the principal water resource in the arid southwest, <br /> <br />the Colorado River is of major importance to each of the <br /> <br />seven Basin states as well as to Mexico. The dams and res- <br /> <br />ervoirs constructed on the river provide for flood control; <br /> <br />rive r <br /> <br />regulation; domestic, <br /> <br />municipal, industrial, and <br /> <br />agricultural water use; hydroelectric power production; rec- <br /> <br />reational opportunities; and fish and wildlife enhancement. <br /> <br />The Colorado River reaches peak flow rates in excess of <br /> <br />100,000 cubic feet per second (cfs) about once every 3 years, <br /> <br />on the average, in the late spring due to snowmelt runoff. <br /> <br />Prior to construction of Hoover Dam, these high flows caused <br /> <br />correspondingly high levels of damage to the river banks and <br /> <br />riparian lands along the Lower Colorado River. Since the <br />completion of Hoover Dam in 1935, the annual snowmelt floods <br /> <br />have been controlled, first by Lake Mead and later by the <br /> <br />upstream reservoirs as they were constructed. During the 48- <br /> <br />year period from 1935 to 1982, releases from Hoover Dam <br /> <br />exceeded 25,000 cfs in only 2 years, and never exceeded <br /> <br />36,000 cfs. This high degree of control was possible from <br /> <br />1935 to 1962 because the low level of downstream consumptive <br /> <br />use requirements did not require a large amount carryover <br /> <br />storage to meet water requirements during an extended dry <br /> <br />period. Under those conditions, it was possible to operate <br /> <br />Hoover Dam to meet demands and keep the water in storage low <br /> <br />enough that the annual snowmelt inflow could be captured <br /> <br />without risking use of the maximum controlled release <br /> <br />-~- <br />~ <br />