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O{)1259 . . Draft Task 7 Technical Memorandum Results from model scenarios were used in two ways. First, the model was used to test the sensitivity of predicted demands shortages, reservoir contents and instream flows to various operational constraints, new storage facilities and instream flow requirements. Second, model results for each scenario were compared against results of the baseline scenario in order to evaluate which scenario could best meet basin-wide water demands while providing flatwater recreational opportunities and helping to protect the endangered fish. Definition of Model Scenarios In defining model scenarios, particular attention was given to the relative priorities of the existing direct flow rights, the proposed instream flow right, existing and future storage rights and future water demands. The structure of the scenarios was chosen to help answer the following fundamental questions: 1) is there a sufficient legal and physical supply to meet all future demands?, 2) if there is an insufficient legal supply, can the Juniper subordination make up the shortages?, and 3) if there is an insufficient physical and/or legal supply, can reservoir releases (from existing and/or proposed projects) make up the shortages? These questions were addressed by the careful selection of priorities assigned to the proposed instream flow right, to storage in reservoirs and to future demand increments. Model scenarios were defined to help identify the best administrative and/or development strategies to meet various demand levels in the basin. Each model scenario was comprised of a suite of individual model runs and included three possible demand levels. The three demand levels included the baseline (1989 maximum), 201S-level and 2040-level demand conditions (Figure 3). These demand levels are represented in the model by defining demand increments to bring the depleted depleted hydrology of the model up to the baseline or future conditions (Figure 4). Formulation of the size and locations of basin demands was discussed in detail in the Task 2 Technical Memorandum for this Feasibility Study. Several administrative strategies were also investigated and included examining the utility of subordination of the Juniper rights to all existing demands and possibly to 2015- and/or 2040-level demands. Scenarios were structured to facilitate comparison of the strategies of meeting future demands through subordination of the instream flow for endangered fish and meeting future demands by making releases from storage accrued under rights considered senior to the instream flow. The following sections of this Technical Memorandum provide an overView of modeled assumptions, a summary of results of model runs from five water development scenarios and environmental and cost considerations for each alternative. GENERAL MODEL ASSUMPTIONS Priorities of Demands and Reservoirs Diversions to meet demands or to fill reservoirs in the the basin model are made according to the ranks assigned to demand and reservoir storage arcs of the network. These ranks generally map the relative priorities of basin water rights, senior rights having higher ranks. Conceptually, there are four categories of demands and reservoirs in the model, grouped according to the priorities of the water rights which support them. Included are: 1) existing demands and reservoirs with rights which are senior to the Juniper project water rights (1954), 2) existing demands and reservoirs with rights which are junior to 1954, 3) future demands and reservoirs with rights which are senior to 1954, and 4) future demands and reservoirs with rights which are junior to 1954. 4 ,1,._, ~.