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Flaming Gorge Dam, forecasted inflows must be incorporated into the decisionmaking process. A description of this process is provided in section 1.5 of the DEIS. Inflow forecasts generated by the National Weather Service each month are used by Reclamation to plan future reservoir operations. These forecasts have some degree of error associated with them which can impact the safe operation of a reservoir. Forecast errors are attributable mostly to hydrologic variability and, to a much lesser degree, the forecasting procedure. For this reason, forecast errors will always be a factor associated with the operation of Flaming Gorge Reservoir. Analysis of the historic forecast errors at Flaming Gorge provide the basis for estimating safe upper limit operating reservoir levels at various times of the year under varying hydrologic conditions. From this analysis, 1% exceedance forecast errors were generated and used in routing studies designed to establish safe upper limit reservoir levels. A 1 % exceedance error can be expected to occur about I% of the time or about 1 year out of every 100 years. Safe operation of Flaming Gorge provides enough storage space in the reservoir at all times throughout the year, such that the volume of a 1% exceedance forecast error can be absorbed by the reservoir. In other words, the safe operation of Flaming Gorge Reservoir must assure that 99% of the foreseeable forecast errors can be successfully routed through the reservoir without uncontrolled spills occurring. For this reason, the reservoir elevation is intentionally drawn down during the fall and winter months. The upper limit drawdown levels established as safe operating parameters for Flaming Gorge Reservoir under various hydrologic conditions were determined through the routing studies, and are shown in table S-2. These upper limit drawdown levels apply to both the No Action and Action Alternatives. Table S-2.-Upper Limit Drawdown Levels for Flaming Gorge Reservoir Unregulated Inflow May 1 Upper Forecast Percentage Limit Drawdown Exceedance Range Level 1 to 10 6023 10.1 to 30 6024 30.1 to 40 6025 40.1 to 59.9 6027 S.13.2 Reservoir Operations Process Under the No Action Alternative S.13.2.1 Operations in May Through July (Spring Period) Under the No Action Alternative, the April through July unregulated inflow forecast and the condition of the reservoir, would be used to establish the magnitude and duration of a spring peak release for the current year. The magnitude of the spring release would normally be from 4,000 cfs to powerplant capacity (about 4,600 cfs), unless hydrologic S-20 -11- Operation of Flaming Gorge Dam Draft EIS