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Actual Operations Under Criteria - Water year 1988 The initial plan of operation for water year beginning October I, 1987, and ending September 30, 1988, was based on forecasted reservoir inflow conditions for October through January and average inflow conditions through the rest of the water year 1988 and scheduled releases from Lake Powell of 11.2 million acre-feet (MAF). T4is plan of operation would have created 5.05 MAF of vacant space in the Colorado River reservoir system by the end of September 1988, of which 1.8 MAF would have been in Lake Powell. With this plan of operation the contents of Lakes Powell and Mead would have been within 1.4 MAF of each other at the end of September 1988. The April through July forecast of runoff into Lake Powell made on January 1, 1988, waS 6.8 MAF or 83 percent of the long term average. The long term average is calculated by the Bureau of Reclamation using 80 years of natural flow data (1906-1985) and current depletion levels. Accordingly, releases from Glen Canyon Powerplant averaged about 14,000 cubic feet per second (efs) or 42 percent of maximum powerplant capacity for January through February. The monthly April-July forecasts increased slightly for February then decreased each month until on June 1, the forecast was 5.1 MAF or 63 percent of the long-term average. In response to these forecasts and to insure filling Lake Powell, powerplant releases averaged 11,400 cfs for March, 9,100 cfS for the months April through June, and 11,700 cfs for July. Climatic conditions for the water year 1988 were very dry for much of the Upper Colorado Region and surrounding areas. The western states were dominated by high pressure zones throughout the year resulting in lower than normal precipitation. The amounts of precipitation for the water year ranged from much below normal (less than 50 percent) over the Upper Green River Basin to near or slightly above normal in the San Juan drainage. Lake Powell inflows remained below average through the spring runoff with a snowmelt runoff peak of 34,900 cfs being ohserved on May 22, 1988. The actual unregulated April'July runoff into Lake Powell was 4.8 MAF in 1988, or 59 percent of average. Unregulated runoff is the inflow to Lake Powell adjusted for the change in storage of the upstream reservoirs discussed in this report. The lake reached its maximum elevation on July 5,1988 of3,69331 feet, or 95.75 percent full. The total unregulated runoff flow into Lake Powell for the water year was 8.2 MAF or 68 percent of the long-term average. Water supply for the San Juan River above Navajo Dam for the water year was also 68 percent, while the Gunnison River above Blue Mesa Dam was 56 percent, the mainstem Colorado River above Grand J unction, Colorado was 75 percent, and the Green River above Flaming Gorge Dam was at 54 percent of the long'term average. Total releases from Glen Canyon Dam were 823 MAF while the regulated inflow for the year was 8.6 MAF. As required by Section 602 of Public Law 90-537, the operation of the Colorado River system is coordinated with Federal and State agencies that have interest in the Colorado River. The Annual Operating Plan (AOP) for water year 1988 was prepared by the Bureau of Reclamation in consultation with representatives from the Governors office of the seven Basin States, the Upper Colorado River Commission, the International Boundary and Water Commission, the U.S. Corps of Engineers, and Western Area Power Administration. Tbese same representatives are consulted as river operations under the AOP are modified as required during the year as runoff predictions are adjusted to snowpack and climate variability. These consultations are with a technical forum for resolving operational issues on the Colorado River. 2