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Projected Plan of Operation - Water Year 1986 A proposed operation plan for water year 1986 for major reservoirs of the Colorado River system was formulated and distrib- uted to representatives of the Colorado River Basin Stales in November 1985. This plan was prepared in accordance with the Operating Criteria published June 4, 1970, in compliance with Section 602, Public Law 90.537. The plan reflects operation for tiood controi, domestic and irrigation use of water, hydroelectric power generation, water quality control, fish and wildlife propagation, recreation, and Colorado River Compact requirements. The water year 1986 plan varied from the plan developed for water year 1985 which was based on the need to develop sufficient reservoir space by January 1, 1985, to reduce the risk of reservoir spills. At the end of water year 1985 all of the reservoirs were at a lower level than the previous year. This condition allowed some flexibility in operations during the first 3 months of water year 1 986. Releases at 45 percent powerplant capacity at Glen Canyon will be made from October to December to finish an environmental study betow Glen Canyon with increased releases during January 1986 in order to develop sufficient vacant reservoir space to reduce the risk of spilling. This also reduces the risk of damaging flood control releases from Hoover, Davis, and Parker Dams, should large runoff forecasts occur during the 1986 runoff period. Releases from January through July will be based upon the runoff forecasts received during that time but will result in greater available space on August 1, 1986, than the minimum flood control requirement of 1.5 mat. The plan calls for a total Glen Canyon release in water year 1986 of 8.7 maf under reasonabie minimum intiow conditions. An annual release of 11.1 maf would be required under most probable inflow conditions, which would fill Lake Powell and also equalize the active contents of Lake Powell and Lake Mead by September 30, 1986. With a reasonable maxim.um inflow during water year 1986, the projected Glen Canyon release would be 16.1 mat. This volume of inflow would require maximum powerplant releases for all ot water year 1986 to avoid the use of Glen Canyon's river oullet works or spillways. The projected operation for most probable runoff conditions for each reservo" in the Colorado River Basin lor water year 1986 is descflbed in the following pages. Charts showing the projected monthly outflows from each reservoir for the three assumed hydroiogic conditions are presented with each reservoir operatibn. Each of these assumptions uses the most current hydrologiC information available by including actual forecasted October through December 1985 inflows. The monthly inflows for the remarnder of the year were based upon the following assumptions: (1) most probable based upon the 1906 through 1983 natural flows developed for the Colorado River Simula. tion System (CRSS) model depleted up to the 1 986 level; (2) reasonable minimum based upon the annual volume of inflow which would be exceeded about 90 percent of the time; and (3) reasonable maximum based upon the annual volume of inflow which would be exceeded about 10 percent of the time. Imperial Dam 5