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Lake Powell (Colorado River) Water Year 1985 Lake Powell. which is impounded by Glen Canyon Dam, was operated as part of the Colorado River Storage Project (CRSP) In accordance with governing contracts and laws to provide river regulation. Opll. mum power production, recreation, and lisn and wildlile enhancement during water year 1985. At Ihe start 01 water year 1985, Lake PO'Nel1 had an active content ot 24.35 mal at elevation 3696 feet (97.4 percent full). The most probable operating plan based on the October lorecast called for totai water year re'leases 01 13.75 mat based on an unregulated Inllow of 129 maf The reasonable maximum (upper decile) water supply had scheduled water year releases 01 18.1 maf based on an unregulated Inflow of 18.14 maf. On January 1 the Aprll.July inflow was forecasted to be 11.5 mal (154 percent 01 average). Discharge from Glen Canyon remained at powerplant capacity for January and February. In March the fore. cast dropped to 135 percent and was 138 percenl of normal on April 1. To insure filling Powell by the end of June powerplant releases were lowered to 70 percent of capacity during March and April Weather during March was at normal or slightly above normal over the drainage basin above Lake Powell. By April 2 the weather paltern had changed to above average temperatures and below normal precipitation. The warm weather continued through April with above average preclpl. tation and May had a similar pattern, although there were short periods of cool, wet weather over parts of the basin. As a result of the warmer than average temperatures the snow melt runoff in. creased rapidly from 20,000 ciS on April 1 to 50,000 cfs on April 15, with peak inflow occurring on May 11, 1985. ThiS average daily unregulated peak inflow was 93,580 cfs with a secondary peak of 81,560 cfs occurring on June 14. Between peaks the unregulated Ilows dropped to 55,230 cfs. Regulated peak daily Inflow was 81,000 cIs on May 22, with a secondary peak of 69,000 cfs on June 13. The low flow during this time was 52,000 cfs. On July 1 Lake Powell reached its maximum elevation of 3700.12 leet. The actual unregulated April.July runoff was 11.97 maf which is 160 percent 01 average. Maximum discharge below Glen Canyon was 44.810 cIs and occurred on June 21, as a result of combined powerplant and river outlet tube releases. A total 01 1.03 mal was released through the river outlet tubes in May and June, bypaSSing the powerplant in order to control releases by not having to use the spillway. The total 1985 water year unregulated inflow 10 Lake Powell was 17.5 maf which Glen Canyon Dam 14 ".:';-"'." . is equivalent 10 a reasonable maximum (upper decile) water supply. Total water year releases below Glen Canyon were 19.3 mal 01 which 1.03 mat bypassed the powerplant. Water Year 1"986 Lake Powell began the water year at elevation 3685.70 feet with an active content of 22.76 mal (91 percent full). The plan of operation for the first 3 months of the water year was to maintain releases at about 45 percent powerplant capacity in order to complete an environ. mental study of the riverine system through the Grand Canyon. Beginning in January, assuming an average runofl, dls. charge would go to 90 percent 01 plant capacity and then back to 50 percent of capacity tor February through June. The months of July to September would be operated for power and recreation demands with discharges at 90 percent of plant capacity. Under the most probable inflow operation the reservoir would fill in early July and the total water year releases would be 11.1 maf with unregu- lated inflows of 12.26 mal. The operation lor reasonable maximum inflow (upper decile) is the same as for most probable October through January. From February through August the discharge would be at plant capacity and lowering to 90 percent of. capacity in September. Total water year releases 01 16.1 mal based on an unregulated inflow of 17.4 mal would be required to fill Lake Powell but without bypassing the powerplant. The actual operation will be based on lorecasted inflow projections received monthly. Lake Powell Active Storage' ChartS Reservoir Acre'Feet EI. (Ft.) Maximum Storage 25,002,000 3700 Rated Head 9,428,000 3570 Minimum Power 4,126,000 3490 Surlace Area (Full) 161,390 Acres Reservoir Length (Full) 186 Miles Powerplant Number of Units 8 Total Capacity 1,100,000 Kilowatts . Does not include' .998.000 acre leel Of dead slora\je oclow 3370 feel.