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-------------= 00lG5r! 4.3 Sources and Derivation of Demand Data 4.3.1 Upper Basin The Upper Basin depletions used in the demand data base are essen- tially those depletions presented in the current version of the Upper Colorado Region's report titled "Projected Water Supply and Depletions - Upper Colorado River Basin," or so-called depletion schedule. This schedule represents the Bureau of Reclamation's best estimate of existing and projected depletions of water due to man's activities in the Upper Colorado River Basin. Each State's portion of the schedule was prepared in consultation with the water resource agency of the respective Upper Basin State and has been reviewed by the States. The values in the schedule do not necessarily have the concurrence of the States, however. Since projected depletions change from time to time, the depletion schedule is typically reviewed on an annual basis and updated if necessary. f ; Estimates of present use were developed by updating depletions reported in the Upper Colorado Region Comprehensive Framework Study published in June 1971. This study was a large State-Federal inter- agency effort to formulate framework plans for short- and long-term water resource needs. Included in the study was a report of water uses by State and type of use for a normalized 1965 level of develop- ment. Values from the study have been updated to the 1983 level of development. Projections of water use beyond 1983 are developed from projections supplied by State water resource agencies and from construction schedules of projects authorized for construction or already under construction. Other input data including monthly distribution of demands, return flow values, and salt pickup values are taken from project data. If project data do not exi st, the data values are estimated. As more and better data become available, these values are revised. For example, some revision to the salt pickup values has been made during the past couple of years as more studies have been completed. The demand data base does not include evaporation from major Upper Basin reservoirs because these quantities are simulated in the modeling process. Alternative depletion schedules, such as those developed for the Colorado River Basin Salinity Control Forum, have been developed for use with the model by working directly with members of those organi- zations. . ~ 4.3.2 Lower Basin The Lower Basin depletions used in the demand data base are essen- tially those depletions presented in tables 2 through 8 of the Lower Colorado Region's report titled "Consumptive Use of Diversions from the Main Stem, revi sed September 1982." These water use projections 15