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River Regulation West Canal Outlet Works. Fontenelle The natural virgin runoff reaching the streams of the Colorado River drainage system above Glen Canyon Dam during water year 1980 waS estimated at about 17.5 million acre-feet. Of this amount, about 4 million acre-feet of water was consumptively used within the Upper Colorado River Basin States. Adjustments in storage in other main stem reservoirs resulted in an inflow to Lake Powell of 13,2 million acre-feet. The release from Glen canyon Dam, based on measurements at the gaging station at Lees Ferry,-Ariz" was 10,920,000 acre- feet. For the 1-year and 10-year periods ending September 30, 1980, 10,967,000 acre-feet and 89,989,000 acre-feet, respectively, passed the compact point at Lees Ferry, " ' 24 The projected release from Lake Powell based on the most probable forecast of runoff is 9,950,000 acre-feet. Releases could vary from a minimum of 8,230,000 acre-feet with most adverse and lower quartile runoff to 11,031,000 acre-feel with upper quartile runoff. When added to the flow of the Paria River, this would result in an Upper Basin delivery ranging from 89,6 to 92 million acre-feet for the 10-year period ending September 30,1981, Normally, daily releases are made from the storage reservoirs in the Lower Basin to meet the incoming orders of the water user agencies. All water passes through the powerplant units. The daily releases are regulated on an hourly basis to meet as nearly as possible the power loads of the electric power customers. Minimum daily flows are provided in the river to maintain fishery habitat. Adjustments to the normal releases are made when con- ditions permit to provide more satisfactory conditions for water oriented recreation activities, to provide transport for river- bpfhe sediment to desilting facilities, and Grand Canyon to assist in controlling water quality. Mini- mum releases 1rom Lake Powell were 1,000 cubic feet per second (ft'/s) during the winter months and were increased to 3,000 fe Is during the summer months. Anticipatory releases and river regulation below Hoover Dam were accomplished in a manner which resulted in a total deliv- ery to Mexico 01 approximately 4.436,000 acre-feet in excess of the Treaty quantity during water year 1980. Of that amount 185,021 acre-1eet of drainage waters were bypassed for salinity control pursuant to provisions of Minute No. 242 01 the Inter- national Boundary Water Commission.