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+ runoff was nearly identical to that of 1984 but was also under-forecasted during the winter months. As the spring runoff commenced, it became clear that power plant bypasses were required. These releases were initiated in May and continued into July, resulting in peak releases of 8,000 cfs. Although August and September releases were restricted to provide the test flows not exceeding 2,600 cfs, the reservoir remained full through September and required fairly high releases to evacuate the reservoir. During average runoff years, the forecast is also quite important since a high priority is placed on filling the reservoir each spring. Changes in the forecast can dramatically influence monthly releases. In 1967, spring releases varied from 66,000 acre-feet in March to 195,000 acre-feet in June. In 1988, a declining forecast dropped normal releases from 199,000 acre-feet in January to 75,000 acre-feet in June. Considering the extreme drought conditions of 1988 through 1990, this reduction in releases to conserve reservoir storage was considered very appropriate. Since the average annual inflow to Flaming Gorge is about 1.7 MAF, historic operation has structured monthly releases around firm power commitments within the restraints of optimizing conservation storage. During low runoff years such as 1981 and 1989, or storage recovery years such as 1978, releases from the dam have often been constrained to near the minimum release of 800 cfs. These low releases have adversely impacted incidental project purposes such as power generation and recreation. Runoff forecasts are much less important during these types of years since there is either a substantial vacant storage volume to refill or there is a large unused release capacity that can accommodate forecast increases. The more liberal releases of 1977 to 1978 period which were based upon maximizing power production have been modified to curtail releases in dry periods as occurred in 1988, 1989 and 1990. This was due in part to the large vacant storage that currently exists in Lake Powell. Low release years typically consist of constant low flows interspersed by peaking releases for power system and other emergencies [6]. 3.8 Bibliography [1] U.S. House of Representative Document Number 353, 86th Congress P.L. 87- 590 August 1982 as Amended. [2] U.S. Bureau of Reclamation, Updating the Hoover Dam Documents 1978. Chapter VII, Operating Criteria pp 113-149. [3] U.S. Department of Interior Opinion, Legal Implications of Proposed Changes in Operation of Glen Canyon Dam. Office of the Solicitor Inter Mountain Region, Salt Lake City Utah; June 6, 1988. [4] U.S. Water and Power Resources Service, (Bureau of Reclamation), Project Data Book 1981, pp 355-372. [5] U.S. Geological Survey, Water Resource Papers 1976-1982. [6] Written communications with Randy Peterson, U.S. Bureau of Reclamation, Upper Colorado Regional Office, Salt Lake City, Utah; January 19, 1989. 3-10