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<br />California's flood control reservoirs provide over
<br />5 million acre-feet of seasonally-reserved flood
<br />control storage, an amount that would cover the
<br />entire state to the depth of abouf one-half inch, In
<br />addifion, the state has 6,000 miles of levees,
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<br />Most dams and reservoirs provide water for more
<br />than one purpose, and these purposes often
<br />compete with each another. Water managers must
<br />keep enough reservoir storage space available to
<br />manage floods during the flood season but store
<br />enough water to protect against water shortages
<br />during the dry season. As one water manager put
<br />it, 'The ideal for flood control is an empty reservoir;
<br />for water storage, a full reservoir," Additionally, wafer
<br />releases to benetit fish and wildlife have become
<br />increasingly important and must be incorporated
<br />into operational decisions. Construction and
<br />operation of flood control systems damaged the
<br />riparian environment.
<br />
<br />Water releases from dams augment naturally low or
<br />intermittent stream flows and repel salt water
<br />intrusion from the ocean in low outflow months.
<br />To mitigate the projects adverse impacts to fisher-
<br />ies, water is released below some dams to help
<br />spawning fish, including threatened and endangered
<br />species. Dams and reservoirs also provide recre-
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<br />ational opportunities, including swimming, boating,
<br />and fishing where public health and safety allow,
<br />
<br />All levels of government - local, state and tederal-
<br />have a hand in operating the flood management
<br />systems, Many of the larger projects, such as Shasta,
<br />Folsom and New Melones dams, which are part of
<br />the federal Central Valley Project (CVP), are owned
<br />and operated by the Corps and/or the U,S, Bureau
<br />of Reclamation (Bureau), Some projects, such as
<br />Oroville Dam, are owned and operated by DWR,
<br />Other systems, such as most of the dams within
<br />Los Angeles County, are owned by local agencies
<br />and private entities.
<br />
<br />There is no single formula for balancing the com-
<br />peting needs of each project. There is tremendous
<br />variation in hydraulic conditions, including down-
<br />stream channel capacities and terrain. In addition,
<br />projects operate within various parameters to achieve
<br />certain flood protection levels as well as defined
<br />water supply, recreation and hydropower production
<br />objectives. Operational decisions at each dam are
<br />based on criteria developed by historical storm
<br />analyses, computer model simulations, statistical
<br />risks and downstream impacts. These criteria are
<br />used to determine when and how much water is
<br />released from the reservoirs during storms.
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