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Actual Operations Under Criteria - Water year 1990 Climatic conditions in the Colorado-River Basin for water year 1990, as in 1988 and 1989, were again dry. Precipitation for the water year was 80 percent of a~rage, for both the Upper Colorado Basin and the Lower Colorado Basin. Because of the extended drought and the associated soil moisture deficit, spring runoff in the Upper Basin was considerablybelowa""rage. Unregulated April-Julyinflowto Lake Powell was 3.21 million acre-feet, 40 percent of the long-term average. U nregulaled runoff is the inflow to Lake Powell adjusled for the change in storage of the upstream reser",irs. Lake Powell recorded a peak regulated inflow of 26,000 cubic feet per second on June 15, and reached a maximum elevation on July I at 3,650.5 feet, with a corresponding storage of 17.9 million acre-feet. The total unregulated runoff into Lake Powell for the water year was 5.48 million acre-feet. 46 percent of the long-term average. All of the Upper Basin reser",irs recorded below.normal inflows in waler }<'ar 1990. San Juan Ri""r inflow into Navajo Reservoir was 64 percent of the long-term average. Unregulaled inflow of the Gunnison River into Blue Mesa Resermir was 53 percent of normal, while unregulated inflow of the Green River into Flaming Gorge Reservoir was 56 percent of the long term average. Inflow into Fontenelle Resecmir was 67 percent of normal. Upper Basin reser",irs, flaming GOTge, Blue Mesa, and Na vajo, experienced modest rebounds in storage in water year 1990. These increases in storage occurred because releases frorn these reservoirs were primarily constrained to minimum le""ls. Storage in Lake Powell and Lake Mead, however, is down 3.6 and 1.4 million acre-feet from last }<'ar. respcctively. The October I, 1990, system vacant space was approximately 17.6 million acre-feet. Aggregate Colorado Ri""r li"" slorage at the end of the }<'ar was 43.9 million acre-feer. Aggregale storage decreased in warer year \990 by4.6 million acre-feet. Total releases from Glen Canyon Dam (deliveries from lhe Upper Basin ro lhe Lower Basin) for water year 1990 were 8.25 million acre-feet. Calendar year 1990 was an historic one, as it was the first year that a consumptive use of more than the full hasic apportionment for the three Lower Basin slates, 7.5 million acre-feet, was requested. The 1990 operation plan aUo'Wed the 'Water needs of the Lower Basin states to be satisfied~ up to 7.5 million acre-feet ofbeneficiat consumptive use, during the calendar year. During wa1er }<'ar 1990, Mexico received a tola! delivery of aboul 1,390,000 acre-feet it the Norlherly International Boundary (NIB). Of the 1,390,000 acre-feel of Colorado River water reaching the NIB, about 570,000 acre-feet were delivered through the Pilot Knob Powerplant and Wasteway from lhe All-American Canal. An estimated 300,000 acre-feet were released thtough Laguna Dam. The remainder of the flowa1 the NIB was made up of return flows to the Colorado River below Laguna Dam, and returns to the Gila Rher below the gaging station near Dome. 2