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<br />.. <br /> <br />000316 <br /> <br />e <br /> <br />e <br /> <br />; <br /> <br />DRAFT <br /> <br />,) <br />, jJ pa-' JY <br />e~~~.~ <br /> <br />1. Study Period. The Preliminary BO uses the 1975-91 water years for the study period. Is this acceptable <br />or do we want to use another period of record? u..~ ex~ p..tur ,<<oJ . <br /> <br />WORKING LIST OF ASSUMPTIONS <br />AND GROUND RULES <br />(MARCH 31, 1999) <br /> <br />. <br /> <br />(Most of the analysis in the Preliminary BO is done on a wet year (1986), dry year( 1989) and an average year <br />(1982); the entire 1975-91 study period was not generally used in the BO's analysis. Is this what we want to <br />do? Or, do we want to use the entire study period? <br /> <br />2. Baseline Hydrology. The Preliminary BO uses the Cl Scenario. The Cl Scenario uses historic gage data <br />With the exception that irrigation demands are calculated from average irrigation efficiencies for the study <br />period, 1975-1991. The Cl run alsQ includes backcasting of 1996 water year demands throughout the entire <br />study period.. The average annual depletions for these existing demands are used for every year. Depletions <br />from demands that were in place for a potion of the 1975-91 period were included in the Cl run for the entire <br />study period. Depletions from new demands such as Ruedi Round 1 and 2 are also included. This list of all <br />the projects that were included in the backcasting at their 1996 demand levels is on page 3 of Appendix D. <br /> <br />The Service has indicated (memo from Henry Maddux to Randy Seaholm, February 2, 1999) that the baseline <br />hydrology should be the Cl run with the existing flow related RIPRAP items included. The Service also <br />fudicated in this Memo that "Category 1" items should not be included in the baseline because they may be part <br />of the solution. (Should this be Category 1 instead of Category 2?). <br /> <br />Dowe want to use the C 1 Scenario including the RIPRAP items as our base case for purposes of estimating <br />the quantitative effects of the various alternatives for yielding water for the fish? Or, do we want to: (1) modify <br />C 1 to make it more to our liking, or (2) use something entirely different? If we are going to accept C I for use <br />as our baseline hydrology, it will be important that everyone is satisfied with the depletion levels listed in <br />Revised Appendix A for existing projects with backcasted demands. <br /> <br />3. Model and Time Step. StateMod will probably be the model of choice for that modeling which can be <br />accomplished with a monthly time step. It is suspected, however, that a daily time step model will be necessary <br />during certain periods in order to meet the overall objectives. For example, it will not be possible with a <br />monthly time step model to determine the contribution to increased spring peak flows that can be expected <br />from implementing a specific 3.ltemative for providing more water to the fish. In order to determine the <br />. . <br />contribution to the spring peak, a daily time step will probably be necessary. Furthermore, in order to <br />determine whether an alternative will violate a channel flow capacity constraint (e.g. the 1100 cfs on the <br />Fryingpan below Ruedi) it will be necessary to have flow data on a daily basis. In both these examples, we <br />would only need daily flow data for a relatively short period (a few weeks, perhaps one month) and not for an <br />entire year. <br /> <br />The Service (February 2, 1999 memo from Henry Maddux to Randy Seaholm) indicates there may be the need <br />for some daily modeling in May and June. <br /> <br />We will first have to determine if the additional cost and brain damage associated with a daily time step model <br />is worth the effort and, if the answer to this question is yes, how do we go about achieving a successful and <br />