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-* / ' These relationships are shown on Table 1. The first column of numbers shows the effect of an activity on the excess salt discharged from the Palo Verde Subarea. The second column shows the amount of this excess salt contained in Sundesert Plant diversions. The third column shows the amount of salts from other subareas contained in Sundesert Plant diversions. The last column indicates the reduction in salinity at Imperial Dam caused by each activity. Assuming an annual flow of 6 million -----~_._--~--"'_.~--,---".-..,..~-,,-,_." . .-- --. -- --,' . --"ac!,~-!eet reaching Imperial Dam~ the salinity decreases by 1 milligram per liter for each 8,160 tons of salt removed. This complicated display was made to portray the interaction between excess salt discharged from the Subarea and excess salt removed from the river system by the Sundesert Plant. For example, the second 17,000 acre-feet diverted contain less salt than the first 17,000 acre-feet. This is because the Outfall Drain would contain less excess salt after the 6-month rotation cycle begins. Remaining Potential As indicated on Table 1, the Sundesert Plant would reduce the di scharge of excess salt from the Palo Verde Subarea by 12,300 tons, and would remove 10,900 tons of the excess salt discharged from the Subarea. This would decrease the excess salt from the Subarea that enters the river from 144,000 tons to 120,000 tons per year. These relationships are shown on Table 2. A basic premise in considering methods to reduce salt loading is that the di scharge of excess salt from the Palo Verde Subarea is proportional to the amount of water that percolates through the saline aquifer and discharges in drains. The water originates as agricul- tural leaching water and canal seepage, and a reduction in these would reduce the net salt discharge. For example, if the lateral seepage in the Palo Verde Subarea were eliminated and the on farm efficiency were increased to 60 percent, the amount of water percolating through the soil would be reduced from the 1974 estimate of 66,000 acre-feet to about 26,000 acre-feet, a reduction of about 60 percent. A corres- ponding reduction in salt discharge could be expected. 002B68 24'"