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• • • • • • • • • • • • • 5 In years classified as dry or moderately dry, the difference between the Action and No Action alternatives, in terms of minimum duration, can have a significant impact on the reservoir elevation. When dry years occur in series, which is often the case, the year to year differences in reservoir elevation caused by the operational regime can compound upon each other as shown in this case. T; ..,,.. 7 rlnflav tha Mnct Tntanca Thri o VPar Drv Cycle Flaming Gorge Model Results Comparison Driest Three Year Cycle Release Hyidrogiaph 151J00 - -- 14000 -Action Alternative 13DOD -NoActior Alternative - - 12000 11000 10000 -- - 9000 8000 ° -- r? 7000 O 6000 5000 4000 3000 2000 1000 D Jan-02 Jul-02 Jan-113 Jul-03 Jan-04 Jul-04 Jan-05 Jul-05 Jan-06 Date When conditions are wet, the Action and No Action alternatives operate Flaming Gorge Dam very differently from when conditions are dry. Spring releases for the Action alternative in wet years are typically larger than those generated for the No Action alternative as a result of attempting to achieve specific targets established for Reach Two. This is evident in Figure 3, which shows the reservoir elevations that occurred during the most intense three year wet cycle found in the inflow hydrology. The higher releases that occur each spring under the Action alternative cause the reservoir to fill less in the spring as compared to the No Action alternative. As a result, the releases under the Action alternative during the baseflow period are not as high as those that occur under the No Action alternative. The No Action alternative is forced to release greater volumes during the baseflow period to achieve the drawdown target established for the following year. This can be seen in Figure 4, which shows the daily release hydrographs that occurred during this three year wet cycle. In November, the release constraints of the No Action Figure 3 Reservoir Elevations Under the Most Intense Three Year Wet Cycle