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.':": "f">!' ~,,<::.';::,~ '. ,,-,tl," " ". ~ \'"" .' ".,.'.;:/., .. . .'.. . J'~ ..,<! . , .":/' ;; I 000313 tit e DRAFT WORKING LIST OF ASSUMPTIONS AND GROUND RULES (MAR0I31, 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 PreliminaIy BO is done on a wet year (1986)> dry year( 1989) and an avenge year (1982); theemi.re 1975-91 stlIdy 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? 2. Baseline Hydrology. The Pre1imioary BO uses the Cl Scenario. The C 1 Scenario uses historic gage data with the exception that irrigation demands are c:aIcuIated from a,,-erage 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 a'\o-erage annual depletions for these existing demands are used for every year. Depletions from danands that were in place for a potion oftbe 1915-91 period were included in the CI run for the entire stady period. Depletions from new dem:ln~o:: 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 Hemy Maddux to Randy Seaholm. February 2, 1999) that the baseline hydrology should be the CI run with the existing flow related RIPRAP items included. The Sendee also indicated in this Memo that "Category 1" items should not be included in the baseline because they may be part oftbe solution. (Should this be Category 1 instead of Category 2?). DO'We.want to uSetbe Cl Scenario as our base case for pwposes of estimating the quantitative effects of the various alternatives for )ielding water for the fish? Or. do we want to: (I) moclii}. CI to make it more to our likiD& or (2) use ~Y1g entirely differeut? Ifwe are going to accept C 1 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. ....: 3. . Model aDd Time Step. StateMod will probably be the model of choice for that modeling which can be accomplished with a moDtbly time step. It is suspeaed, however, that a daily time step modeJ will be necessary during certain periods in order to meet the overall objectives. For example, it will not be possible with a monthly time step model to determine the contribution to increased spring peak flows that can be expected from' implementing a specific alternative for providing more water to the fish. In order to determine the conttibution to the spring peak, a daily time step will probably be'necessary. Furthermore. in order to detennine whether an alternative ~iII violate a channel flow capacity constraint (e.g. the 1100 cis on the Fryingpan below Ruedi) it will be necessary to have flow data on a daily basis, In both these examples, we would only Deed darl}. flow data for a relatively shan period (a few weeks, pe.rbaps one month) and not for an entire )Ur. . The Service (Febnmy 2, 1999 memo ftom Hemy Maddux to Randy Seahohn) indicates there may be the need foi-same'daily modeling in Ma}' and June. We will first have to determine iftbe additional cost and brain damage associated with a daily time step model is worth the effort and, if the answer to this question is yes, how do we go about achieving a successful and