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. . Desalination If there were an inexpensive filtering or distillation method to remove salt from high- salinity water, desalination would be an obvious solution to the problems of the Salton Sea. The process could be used to reduce the salinity of the water already in the Salton Sea, or to desalinate ocean water being pumped from the Gulf of California as part of a "pump-in, pump-out" scheme. If desalination is used to freshen the water in the New, Alamo, and Whitewater Rivers and the water allowed to flow into the Salton Sea, this reduces the quantity of salt going into the Sea but does not solve the problem because salt is not being removed from the Sea. Furthermore, if the desalinated water is diverted instead of flowing into the Salton Sea, this will lower the Sea's elevation and increase its salinity thereby making the problem worse. One desalination proposal was developed last year by U.S. Filter. They proposed treating New and Alamo River water prior to entering the Salton Sea and diverting about 160 T AF/year for recycle. The saline water, 45 T AF/year, would be disposed of, in addition to 22 T AF/year of water which would be pumped out of the Salton Sea for a total water loss to the Sea of 227 TAF/year (160 + 45 + 22). U.S. Filter estimates that the total project capital cost would be between $750 million and $1.0 billion. The impact of the above proposal on the salinity of the Salton Sea is an increase to about 120 ppt at 30 years, which is 20 ppt higher than doing nothing. Furthermore, the elevation of the Sea under this scenario would decrease to -250 feet with a corresponding reduction in surface area of over 30%, to about 260 square miles. Another proposal, by the Metropolitan Water District (MWD), would divert approximately 450 T AF/year of Alamo (390) and Whitewater (60) River water. Mter desalination, the water would be delivered to the Colorado River Aqueduct. MWD estimates the capital cost would be $1.1 billion with operation costs of $58 million/year. Once again, from the point of view of remediating the Salton Sea, this makes the Sea smaller and saltier. In summary, while desalination can be used to produce fresh water for urban household use, in our opinion desalination approaches to reduce the salinity of the Salton Sea would be prohibitively expensive. Pump-In, Pump-Out Another concept that has received attention consists of pumping water from an external source to the Salton Sea and pumping water from the Sea to an external location. The advantage of such a concept is that it has the potential to allow simultaneous control of salinity, elevation, and surface area. The obvious source for pump-in water is the Gulf of California which, of course, is at ocean water salinity. However, for this concept to be practical for salinity control without a reduction in the level of the sea, the salinity of the pump-in water needs to be considerably less than that of ocean water. If the pump-in water is at ocean water salinity, very large quantities of water must be pumped, both in and out. For example, pumping in 400 TAF/year of ocean water and pumping out 500 T AF/year of Salton Sea water is required for the Salton Sea to approach ocean water salinity. Figure 2. Even with this large amount of water exchange, the elevation would decrease by about 23 feet. Figure 3. Our estimate is that the capital cost for such a system would be about $1.7 billion, with another $30 million per year in operating costs (assuming electricity costs of 3.5 i/kWh). Since it is unlikely there will be a source of low-salinity pump-in water, a variation of this concept is "pump-out" only. Pumping out a relatively smal1150 TAF/year of Salton Sea 3