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<br />Flood Control <br /> <br />Lake Mead is operated in accordance with updated flood <br />control regulations which are specified in the Field Working <br />Agreement between Reelamation and the Corps of <br />Engineers, signed in 1982. The regulations stipulate the <br />minimum release levels lIeeded from Lake Mead to route the <br />reasonable maximum inflow. The reasonable maximum inflow <br />is the estimated inflow volume that, on the average, will not be <br />exceeded 19 out of 20 times. This volume is derived by adding <br />an "uncertainty" term to the most probable runoff forecast. In <br />1983, unusual hydrometeorological events resulted in <br />unprecedented large forecasting errors. Subsequent <br />reassessment of the estimate of the "uncertaintv" term led to <br />adoption of larger values for use in determining the <br />reasonable maximum inflow in 1984 and thereafter. <br /> <br />Due to the amount of vacant storage space in Colorado River <br />reservoirs, no flood control releases are anticipated in 1993, <br />but in future years, as Lake Mead refills and flood control <br />releases arc again required by the Hoover Dam Flood Control <br />Regulations, consideration \\rill be given to making those <br />releases over the fall and winter months to avoid high flow <br />rates during the January to July runoff season. This <br />distribution of water reduces the chance of bypassing <br />hydroelectric powerplanls below Hoover Dam and avoids the <br />adverse impacts of higher flood control releases on fish and <br />wildlife, recreation, water quality, and river stabilization. <br /> <br />Routine maintenance of bank line protection facilities were <br />carried out during water year 1992. As in the previous years, <br />greater than normal banklinc repair was necessitated in part <br />by increased wave action from boating and other recreational <br />river traffic. During water year 1992, the river channel in the <br />Lower Basin has remained in good balance, neither aggrading <br />nor degrading significantly in any particular reach. <br /> <br />Total Colorado River reservoir system storage at the start of <br />water year 1992 was approximately 42.2 million acre-feet and <br />about 41.2 million acre-feet at the end of the water year, <br />representing a 1.0 million acre-foot decrease in total <br />remaining available reservoir space. <br /> <br />Alamo Dam on the Bill Williams River and Painted Rock <br />Dam on the Gila River (in the Lower Basin) received minor <br />flood inflow during water year 1992. During water year 1993, <br />the Corps of Engineer flood control facilities Painted Rock <br />and Alamo Reservoirs are expected to be operated in <br />coordination with Reclamation project releases and in <br />accordance with established flood control criteria to <br />maximize the available flood control space in their respective <br />reservoirs. <br /> <br />22 <br />