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Flood Control Lake Mead is operated in accordance with updated flood control regulations which are specified in the Field Working Agreement between Reclamation and the Corps of Engineers, signed in 19&2. The regulations stipulate the minimum release le~ls needed from Lake Mead to route the reasonable maximum inflow. The reasonable maximum inflow is the estimated inflow volume that, on the average, will not be exceeded 19 out of20 times. This ",lume is deri",d by adding an "'uncertainty" term to the most probable runoff forecast. In 1983, unusual hydrometeorological events resulted in unprecedented large forecasting errors. Subsequent reassessment of the estimate of the "uncertainty" term led to adoption of larger values for use in determining the reasonable maximum inflow in 1984 and thereafter. No flood control releases are scheduled for 1991, but in future years, as Lake Mead refills and flood control releases are again required by the Hoover Dam flood Control Regulations, consideration will be given to making those releases over the fall and winter months to avoid high flow rates during the January to July runoff season. This distribution of water reduces the chance of bypassing hydroelectric powcrplants below H oo",r Dam and a",ids tbe adverse impacts of higher flood control releases on fish and wildlife, recreation, 'Wilter quality, and river stabilization. Routine maintenance and repair of bankline damage was carried out during \Wter year 1990. As in the previous year. some bankline erosion was experienced in the Lower Basin of the Colorado River. In some river reaches, especia11y tne Mohave Valley, greater than normal bankline repair was necessitated in part by increased wave action from boating and other recreational river traffic. During water year 1990, the river channel in the Lower Basin has remained in good balance, neither aggrading nor degrading significantly in any particular reach. Total Colorado River reservoir system storage at the start of water year 1990 was approximately 48.5 million acre-feet and about 43.9 million acre-feet at the end of the watcr year, reprcscntinga 4.6millionacrc-foot increase in total remaining available reservoir space. Alamo Dam on the Bill Williams Ri"'r (in the Lower Basin) received minor flood inflow during water year 1990. During water year 1991, Painted Rock (Gila Ri",r) and Alamo Resenoirs are scheduled to be operated in accordance with established flood control criteria to maximize the available flood control space in their respective reservoirs. 22