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<br />Pacific Southwest Inter~Agency Committee Meeting on 10 Dec 1980 <br /> <br />Briefing on "Lake Mead Flood Control Operating Criteria" <br /> <br />Joe Evelyn <br /> <br />Corps of Engineers <br /> <br />Section 7 of the 1944 Flood Control Act <br /> <br />Prior regulations were effective 8 July 1968 <br /> <br />. <br /> <br />What triggered the new evaluation? <br /> <br />a) Needle valve and paradox gate removal at Hoover Dam <br />b) Lake Powell was .filling <br />c) No flood control releases in about 20 yrs. but a signi- <br />ficant level of development activity along the river in <br />u.S. and Mexico. <br /> <br />. <br /> <br />Study Objective: <br />To determine the "best" flood control operating plan for <br />Hoover Dam. <br /> <br />Planning Considerations: <br />Flood control, water supply, hydropower; water quality, <br />operation and maintenance costs, environmental aspects <br />(fish and wildlife, recreation, plant life), s~cial <br />aspects, and impacts in Mexico. <br /> <br />Alternatives Evaluated: <br />9 alternatives with 1 Jan; storage allocations ranging <br />. from 4.5. to 7..5 MAF and various patterns' of release. <br /> <br />Comparison of results: <br />A principle finding was that given the general structure <br />of the flood control operating Plan, the net benefits <br />generated by the various alternatives was relatively <br />insensitive to the choice of 1 January flood con- <br />trol storage. <br /> <br />Selected plan - Study Alternate 1 <br />5.35 MAF of 1 Jan. flood control storage <br />Releases based on steps of 19, 35, 40, and 73 thousand cfs <br />Space building period 1 Aug to 1 Jan <br />Space building releases limited to 28,000 cfs <br />Releases based on controlling maximum (19 times out of 20) <br />forecasted inflow to lowest possible step <br />Minimum flood control storage of 1.5 MAF <br />Lake Mead virgin inflows are adjusted for appropriate <br />depletions (transbasin diversions, net water use, and <br />reservoir evaporation) <br />Credit is given for effective storage space in upstream <br />reservoirs <br />Flood releases will be limited to 40,000 cfs insofar as possible <br /> <br />B-6 <br />