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I I I I I I I I I I I I I I I I I I I 002551 developed for use downstream. Prior to construction of the dam, the Colorado River downstream went through recurring cycles of flooding in the spring and drought during the summer and fall, which caused damage to crops and nearby property. Flows ranged from an estimated maximum of 300,000 cfs on July 8, 1884, to a low of 700 cfs recorded on December 28, 1924, with a recorded average flow of nearly 15,570 cfs prior to the construction of Hoover Dam. The dam stores water to a maximum conservation pool of about 27 maf at elevation 1,221.4 feet above msl, and backs water upstream approximately 115 miles creating a surface area of about 163,000 acres at elevation 1,229 feet msl. The dam is 726 feet high and the water depth is approximately 590 feet. The dam is a major source of power generation in the Southwest, and also provides protection to the downstream area from floods and drought. Water stored in Lake Mead provides a source of water for the lower basin States should a drought occur, although sediment accumulation in the upper end of the reservoir is gradually decreasing the water storage capacity. The powerplant generating capacity is approximately 2,080,000 kW with maximum release at approximately 49,000 cfs. The spillways have a maximum release capacity of about 400,000 cfs at 1,232 msl with the drum gates in a closed position. This provides a total release capacity of 449,000 cfs. Flood storage of 1.5 maf is located between elevation 1,219.6 and 1,229 msl. Imperial Dam - Imperial Dam is located approximately 18 miles northeast of Yuma, Arizona. Construction of Imperial Dam and Desilting works by Reclamation began in January 1936 and was completed in July 1938. The dam was constructed to provide a diversion of Colorado River water to the Imperial and Coachella Valleys, the Reservation Division, and Yuma Valley through the All-American Canal on the west side of the dam; and to the Gila Project and the Yuma Auxiliary Project through the Gila Gravity Main Canal on the east side of the dam. Imperial Dam, which raised the water surface above the original river 23 feet to elevation 181 feet msl, was designed to provide a maximum diversion of 15,155 cfs for the All-American Canal; 2,200 cfs for the Gila Gravity Main Canal; and was designed to pass a maximum flood of 180,000 cfs. Imperial Dam created a reservoir that originally had a capacity of 85,000 acre-feet, but as was anticipated, the reservoir quickly filled with sediment. Intermittent dredging and sluicing operations are required to maintain a small reservoir pool of about 1,000 acre-feet in capacity to ensure diversions can be made to the All-American Canal and Gila Gravity Main Canal. Desilting works were provided for both the All-American Canal and Gila Gravity Main Canal. Sediment accumulations are sluiced downstream to the Laguna Desilting Basin where the sediment is removed by dredging and disposed of adjacent to the desilting basin. Parker Dam - Parker Dam spans the Colorado River between Arizona and California Appendix D - 2 , I.