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r e 000322 e DRAFT WORKING LIST OF ASSUMPTIONS AND GROUND RULES (MARCH 31, 1999) 1. Study Period. The Preliminary BO uses the 1975-91 water years for the study period. Is this acceptable or do we want to use another period of record? Most of the analysis in the Preliminary BO is done on a wet year (1986), dry year(1989) and an average year (1982); the entire 1975-91 study period was not generally used in the BO's analysis. Is this what we want to do? Or, do we want to use the entire study period? COMMENT: · It was the general consensus of the Exec Committee to use the entire period of record available; don't just use 1982, 1986, and 1989 as was done in the Biological Opinion. · Boyle is extending the Colorado River flow data. See Randy about this. Boyle will extend the data beyond the 17 years that were included in the BO. · Also see Ray Tenny's comments on the hydrology for Ute. 2. Baseline Hydrology. The Preliminary BO uses the Cl Scenario. The Cl Scenario uses historic gage data with the exception that irrigation demands are calculated from average irrigation efficiencies for the study period, 1975-1991. The Cl run also includes backcasting of 1996 water year demands throughout the entire study period.. The average annual depletions for these existing demands are used for every year. Depletions from demands that were in place for a potion of the 1975-91 period were included in the Cl run for the entire study period. Depletions from new demands such as Ruedi Round 1 and 2 are also included. This list of all the projects that were included in the backcasting at their 1996 demand levels is on page 3 of Appendix D The Service has indicated (memo from Henry Maddux to Randy Seaholm, February 2,1999) that the baseline hydrology should be the Cl run with the existing flow related RIPRAP items included. The Service also indicated in this Memo that "Category 1" items should not be included in the baseline because they may be part of the solution. (Should this be Category 1 instead of Category 2?). Do we want to use the Cl Scenario including the RIPRAP items as our base case for purposes of estimating the quantitative effects of the various alternatives for yielding water for the fish? Or, do we want to: (1) modifY Cl to make it more to our liking, or (2) use something entirely different? Ifwe are going to accept Cl for use as our baseline hydrology, it will be important that everyone is satisfied with the depletion levels listed in Revised Appendix A for existing projects with backcasted demands. COMMENTS: · It was the general consensus of the Executive Committee to use the Cl model run with the RIPRAP projects included as our base case; i.e. we would make runs with StateMod with everything the same as C 1, except we would add in various alternatives and then compare the results with the original C 1 run. Comprendes? 3. Model and Time Step. StateMod will probably be the model of choice for that modeling which can be accomplished with a monthly time step. It is suspected, however, that a daily time step model will be necessary