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5 period, The model restricts these flows to the range from 800 to 4600 cfs to lower the reservoir elevation to a target of2027 feet above sea level by the beginning of March, These constraints are violated only when the reservoir elevation gets too high for safe operation of the Flaming Gorge Dam (6040 feet above sea level), In March and April, releases are controlled between 800 and 4600 cfs to achieve a reservoir elevation target of 6027 feet above sea level by May. The rule, which operates Flaming Gorge Dam during March and April is identical in both the Action and No Action rulesets, Modeling Assumptions Because of the limitations of the modeling environment, many assumptions were made in the development of the Green River model and the Action and No Action rulesets. The assumptions that are specific to this model are described below: I. Actual historic forecasting of the spring (April through July) Wlfegulated inflow volume for Flaming Gorge is assumed to represent the current and future level of forecast accuracy. Forecasted spring unregulated inflow volumes into Flaming Gorge have been issued by the National Weather Service since 1963. The Green River model generates spring unregulated inflow forecasts with an error distribution that is similar to the historical error distribution. 2. It is assumed that the timing and magnitude of the peak flow of the Yampa River can be predicted accurately at least 10 days prior to its occurrence. To achieve the spring flow objectives of the Action Alternative, while efficiently managing the resources of Flaming Gorge, the peak release from Flaming Gorge must be optimally timed with the peak flows of the Yampa River. The magnitude of the peak release from Flaming Gorge Dam must also be optimally chosen to efficiently supplement flows on the Yampa River. 3. It is assumed that decisions regarding the operation of Flaming Gorge will be made at the beginning of each month. Even when conditions change mid-month, decisions to react to the changing conditions must wait until the beginning of the following month. In reality, operational decisions at Flaming Gorge Dam are made on a daily basis but the Green River model is limited by the monthly timestep process. 4. It is assumed that the natural hydrology of the Green River Basin (from 2002 to 2040) will be similar in the future to the natural hydrology that occurred during the period from 1921 to 1985. 5. Whenever flow objectives for Reach Two are achieved it is assumed that the flow objectives for Reach Three are also achieved,