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<br />powerplant. Consequently, only a portion of the acreage would need to <br />be taken out of irrigation. SDG&E has prepared a tentative farm <br />management plan [6] for the acquired land under which various amounts <br />of land would be retired from irrigation or farmed less intensively, <br />depending on the amount of water that needs to be transferred. If the <br />transfer is limited to 4,080 acre-feet, no lands will need to be <br />retired; but approximately 1,778 acres would be put into a 6-month <br />rotation cycle (6 months cropped, 6 months idle). <br />Roughly, two-thirds of the irrigable land acquired by the utility <br />is in the Palo Verde Subarea. Any land in the Subarea retired from <br />irrigation, or irrigated less intensively in the future will tend to <br />reduce the amount of deep percolation in the Subarea, and will cause a <br />corresponding reduction in the amount of salt loading from the <br />Subarea. In this analysis it is assumed that all the acreage to be put <br />into rotation will be in the Palo Verde Subarea. <br />The Sundesert Project wi 11 reduce the Di stri ct I s salt di scharge <br />to the Colorado River in two ways. First, the use of saline drainage <br />water will remove more salt from the system than is contained in the <br />replacement water released at Parker Dam. For example, the 17,000 <br />acre-feet of drainage water for the first unit will have an estimated <br />salinity of 1,725 mg/L (2.35 tons per acre-foot), while the replace- <br />ment water will have an estimated salinity of 747 mg/L (1.02 tons per <br />acre-foot). This arrangement will result in a net removal of approx- <br />imately 22,600 tons of salt from the river system. <br />Second, a reduct ion in i rri gat i on wi 11 reduce deep perco 1 at ion <br />and associated flushing of salts from the soil. Assuming that the <br />excess salt discharge would be reduced in proportion to the reduction <br />in deep percolation, the flushing of salts would decrease by about <br />12,300 tons per year. Further, the diversion of 17,000 acre-feet <br />annually for the second unit and the release of 12,920 acre-feet of <br />replacement water (17,000 minus 4,080) will result in the net removal <br />of an additional 26,000 tons of salt from the river system. <br />It is estimated that the combination of these actions would <br />reduce the salinity of the river at Imperial Dam by 7.5 mg/L, assuming <br />an annual flow of 6 million acre-feet. 002867 <br /> <br />23 <br />