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, . ,v'. . . . . . meeting the reasonable beneficial Colorado River mainstream consumptive water uses in the Lower Basin as provided by the Operating Criteria, the delivery of firm power in accordance with energy contracts, minimum and specific releases for fish and wildlife and recreational purposes, refilling of vacant system reservoir storage space, potential for flood control releases before shortages may occur, water wasted to the Gulf of California, compliance with the 1944 Mexican Water Treaty and Minute No. 242 of the IBWC, the lack of fully developed water use in the Upper Basin, and in Arizona, and Nevada of the Lower Basin, the ability to store unused water apportionments, guidelines for reservoir filling and draw down recommended for fish spawning periods in Lake Mead, complying fully with compact, decree, statutory, and water delivery obligations, and other short- and long-term effects of 1991 water use decisions. Water Supply Assumptions For 1991 operations, three reservoir inflow scenarios were developed and analyzed; statistically these are approximately the upper quartile, lower quartile, and lower decile inflows and have been respectively labeled the probable maximum, most probable, and probable minimum (see attached graphs of reservoir parameters). Each of these scenarios was adjusted for current soil moisture deficiencies throughout the basin; therefore, each is lower in magnitude than the historical upper decile, mean, and lower decile inflows, respectively. The National Weather Service computer model used to adjust the scenarios was the Extended Stream Flow Prediction model. This model uses current conditions as well as historical data to predict a range of possible future stream flows. Although there is a wide confidence band associated with stream flow forecasts 4 -