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t <br />r <br />1995 WATER SUPPLY ASSUMPTIONS <br />For 1995 operations, three reservoir unregulated inflow scenarios were developed and <br />analyzed and are labeled as probable maximum, most probable, and probable minimum. <br />The attached graphs show these inflow scenarios and associated release patterns, end of <br />month contents, and end of month elevations for each reservoir. <br />The National Weather Service Extended Streamflow Prediction (ESP) computer model <br />was employed to develop each of these inflow scenarios. This model uses current basin <br />conditions as well as historical data to predict the range of possible future streamflows. <br />Although there is a wide confidence band associated with streamflow forecasts made a <br />year in advance, the data are valuable in analyzing possible impacts on project uses and <br />purposes. A soil moisture deficit developed within the basin due to the dry conditions <br />that were experienced in 1994. This soil moisture deficit is expected to affect the <br />magnitude of inflows in water year 1995. Therefore the magnitude of inflows in each of <br />the three inflow scenarios are less than the historical upper decile, mean, and lower <br />decile (10 percent exceedance, 50 percent exceedance, and 90 percent exceedance, <br />respectively) for each reservoir for water year 1995. The three inflow scenarios for Lake <br />Powell are shown in Tables 2(a) and 2(b). <br />The volume of inflow resulting from these assumptions was used as input into <br />Reclamation's monthly reservoir simulation model. This model is used to plan reservoir <br />operations for the upcoming 24-month period. Projected water year 1995 inflow and <br />July 31, 1994 reservoir storage conditions were used as input to this model and monthly <br />releases were adjusted until release and storage levels accomplished project purposes and <br />priorities. <br /> <br />1 <br />5 <br />