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<br />Flood Control <br /> <br />Lake Mead is operated in accordance with updated flood <br />control regulations which arc spccificd in the Field Working <br />Agreement between Reclamation and the Corps of <br />Engineers, signed in 1982. The regulations stipulate the <br />minimum release le~ls needed from Lake Mead to route the <br />reasonable maximum inflow. The reasonable maximum inflow <br />is the estitnated inflow volume that, on the average, win nol be <br />exceeded 190ut of20timcs. This volume isdcrived by adding <br />an '\.mce:rtainty'term to the most probable runoff forecast. In <br />1983, unusual hydrorneteorological events resulted in <br />unprecedented large forecasting errors. Subsequent <br />reassessment of the estimate of the "uncertainty" tcrm led to <br />adoption of larger values for use in determining the <br />reasonable maximum inflow in 1984 and therea flee. <br /> <br />No Oood conlrolreleascs are scheduled for 1992, but in future <br />years, as Lake Mead refills and flood control rele.ases are <br />again required by the Hoover Dam Flood Control <br />Regulations. consideration will be given to making those <br />releases over the fall and winter months to avoid high flow <br />rales during the January to July runoff season. This <br />distribution of water reduces the chance of bypassing <br />hydroelectric powcrplants below Hoover Dam and avoids thc <br /> <br />ad\erse impacts of higher flood control releases on fish and <br />wildlife, recreation, water quality, and river stabilization. <br /> <br />Routine maintenance of bankline protection facilities were <br />carried out during water year 1991. As in the previous years. <br />greater than normal bankline repair was necessitated in part <br />by increased wa\e action from boating and other recreational <br />river traffic. During \Vater year 1991, 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 ~ar 1991 was approximately 43.9 million acre-feet and <br />about 42.2 million acre-feet at the end of the water year, <br />represenling a 1.7 million acre-foot increase in total remaining <br />available reservoir spa.ce. <br /> <br />Alamo Darn on the Bill Williams River (in the Lower Basin) <br />received minor flood inflow during water year 1991. During <br />water year 1992, Painted Rock (Gila River) and Alamo <br />Reservoirs are scheduled to be operated in accordance with <br />established flood control criteria to maximize the available <br />flood control space in their respective reservoirs. <br /> <br />22 <br />