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~ 3.7 Future Operation As discussed in sections 3.2 and 3.5, the basis for the operation of Flaming Gorge Dam in the past has been the authorizing legislation (1956 and 1968) and the Operating Criteria (1970). The resulting operation can be characterized by the following general guidelines: 1. An appropriate winter drawdown of the reservoir to avoid power plant bypasses or spills. 2. A primary objective to fill the reservoir each spring. 3. The ability to operate the power plant at full capacity to meet firm power commitments. The development of hydrology studies and the project description for the Opinion has developed over the past several years. As the studies draw to a close a need was identified to define a proposed operation which is to be consulted upon. This operation has been defined as the present operation under these three objectives, and the Opinion will address the impacts to endangered fish associated with that operation. Definition of this specific operation is difficult, primarily due to the fact that the reservoir operation is based on forecasted runoff conditions. These forecasts are based on changing climatic conditions and include inherent errors and risks which in turn, affect monthly and daily releases. Rather than develop theoretical analyses of reservoir operation, the results of these operational objectives are perhaps better understood by examining the releases of past years. The release and storage decisions that were made can then be applied to expected future conditions to determine the project under consultation. The following paragraphs describe the operation during wet, average, and dry water years. Examples will also be included to demonstrate the influence that runoff forecasts have on release and storage decisions. Table 3-1 lists the monthly release volumes from 1967 through 1988. As can be seen from this table, monthly releases from Flaming Gorge have historically been highest in the months of July, August, December, and January. These years cover a wide range of hydrologic conditions and for the period following 1985, include restricted summer releases to test endangered fish recovery hypotheses. With respect to releases, wet years include 1983, 1984, and 1986; average years include 1967 and 1987; dry years include 1978, 1981 and 1989. The runoff years of 1983, 1984 and 1986 were some of the highest ever recorded on the Green River and very close in volume. However, antecedent reservoir conditions and changing runoff forecasts produced quite different releases. The runoff of 1983 was accompanied by the largest forecast error in the history of the dam. The extreme runoff in early June was completely unexpected and resulted in peak releases of nearly 13,000 cfs and a July release volume of 623,000 acre-feet. The summer and fall releases were also extremely high in order to evacuate the reservoir for the next spring. The runoff of 1984 was also very high, but because the forecast was much more accurate, high releases near power plant capacity continued from January through May and resulted in much lower summer and fall releases. The 1986 3-9