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• 2 To get the model to operate Flaming Gorge Dam more realistically while maintaining the monthly timestep framework, a daily model was developed to take monthly results from the Flaming Gorge model and operate Flaming Gorge Dam to react to daily hydrologic conditions. • This daily model operated Flaming Gorge Dam during the spring (May, June and July) to match • estimated Yampa River flows to achieve target flows for Reach Two. While this caused the release results of the daily model to differ from the release results of the monthly model, it did provide a more reactive approach for achieving the recommended flow targets. To maintain some integrity between the daily and monthly models, the only restriction placed upon the daily model was to • match the total volume released during the spring to the total volume released during the spring by • the monthly model. After a targeted duration was achieved, the daily model released the necessary volume for the remainder of the spring to match the monthly model while minimizing additional bypass releases. This enhancement of the Flaming Gorge model greatly reduced the bypass releases that were reported in the October report. Baseflows, under the Action alternative, are dependent upon the classification of the hydrologic conditions in the Upper Green River Basin. In October (2001) the model based this classification on the volume of unregulated inflow into Flaming Gorge that occurred during the • preceding spring. Once this classification was set on August 1st, it could not change during the • baseflow period. The 2000 Flow Recommendations, however, stated that this classification was flexible and could change if hydrologic conditions changed during the baseflow period. The Authors, however, did not describe how this determination was to be made. Comments received from the Authors gave guidance for how this determination could be made in the model and the • model has now been modified to adjust the hydrologic classification during the baseflow period • when conditions warrant a change. Under the Action and No Action alternatives, a volume of water to be released during the spring is calculated based on forecasted inflows and reservoir conditions. From this volume of • water, a peak release hydrograph is developed to achieve the specific parameters of the operational alternative. In the model presented in the October report, both the Action and No Action alternatives extended the peak release hydrograph to the end of July, when possible, depending on the calculated volume to be released during the spring. The 1992 Biological Opinion, however, • states that base flow levels are to be established by July 20~' at the latest. For this reason, the No • Action alternative was modified so that July 20~' is now the maximum date that the spring release hydrograph can be extended to. This modification increases the peak magnitude and the potential for bypasses in the No Action alternative as compared to the No Action results presented in the October report. In October, the Flaming Gorge model, for both alternatives, had a static drawdown target established for the end of April. During the baseflow and transition periods, releases from Flaming Gorge were determined in an attempt to achieve this drawdown target. For both the Action and No Action alternatives, the drawdown target was set to 6027 feet above sea level • independent of the developing hydrology in the Upper Green River basin. In years where the early indications of the developing hydrology are for wet or dry conditions, this target would, in reality, be reset to a more appropriate level. For example, when the early indications are that the spring is going to be wet, Flaming Gorge will typically be drawn down to a target somewhat lower than