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w Ul I-' 00 portions of units shown below are considered in the Base Case: Unit 1. Grand Valley Stage One 2. Grand Valley (USDA) 3. Meeker Dome 4. Uinta (USDA) 5. Las Vegas Wash (Pittman bypass) Total Tons/Year Removed as of 1984 1/ This number was used in CRSS base case. appears in the Data Table. 17,700 11 27,300 48,000 15,600 7,000 115,600 The 1984 figure The combined salt removal is about 115,600 tons per year at the present time for all completed agency activities. The 7,000 tons reduction as a result of BLM well plugging activities was not included in the 1984 base case, but will be included next year. Figure 7 represents the average base case projection of salinity at Imperial Dam using historical hydrology (1906 to 1983 data base in 15 sequences). The depletion schedule, estimated by Reclamation's Upper Colorado Regional Office in Salt Lake City, Utah, and used in the CRSS model base case projection, is shown in Figure 8. This graphic represen- tation of historical and projected depletions in the Upper Basin was extracted from the 1984 Forum Report and Review. The graph shows that the official Reclamation depletion pro- jections closely approximate the high projection in the 1984 Forum Review. The maximum TDS at Imperial Dam is projected to reach about 1005 mg/L by the year 2010. Using the salinity projections at Imperial Dam, the salt load reductions needed to reduce projected TDS levels to the numeric criteria level of 879 mg/L were estimated and plotted in Figure 9. Figure 9 also shows how a superimposed best-fit logistic curve was plotted to smooth-out the CRSS cyclic data and better define the salt load reduction (target load) for the base case and entire time period. The target load curve, in effect, represents the amount of salt to be removed from the river system to offset expected increases in salinity, above the numeric criteria, caused primarily by increased deple- tions. Thus, about 1.3 million tons per year of salt must 46