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Typical unit water costs for desalting processes applied to brackish water (up to 5000 mg/L) are shown in figure 8 [3]. The economy of plant size is clearly indicated; however, most salinity control applications will be between 5 and 50 Mgal/d plant capacity. The high costs of distillation processes indicate the relative energy costs incurred in the' process. Membrane processes offer the best hope for decreased costs, with the shaded area showing the cost variability because of pretreatment, membrane types, recovery rate, etc. Figure 9 shows a composite of total estimated annual costs related to a 70-percent recovery membrane desalting plant facility for the LaVerkin Springs Unit. At this comparatively low water recovery rate, a large proportion of costs are devoted to lined evaporation ponds to handle the large volume of brine effluent. Typical unit costs for lined ponds now range from $50,000 to $90,000 per acre. For the LaVerkin Springs study, the evaporation pond cost was $72,000 per acre. Other significant cost categories are indicated by chemicals and pretreatment requirements. For compari son, figure 10 shows the est imated cost breakdown for a gO-percent recovery, membrane desalting plant facility for the Las Vegas Wash Unit. As expected, with reduced brine effluent volume, evaporation pond costs have been significantly reduced. However, as a tradeoff, the relative costs of electrical power, chemical supplies, and pretreatment requirements have increased. Thus, optimization of the high-recovery desalting facility can provide opportunities for cost reduction, but additional design efforts are needed to lower sludge (from pretreatment processes) and brine disposal costs. In judging the relative cost comparisons between salinity control units, a "yardstick" known as "cost-effectiveness" has been developed in lieu of a benefit-cost ratio used in most water resource projects. The cost- effectiveness value for salinity control purposes is the total annualized cost of the project per unit reduction of salinity as measured at Imperial Dam in mg/L of total dissolved solids. Table 4 shows the current cost- effectiveness values for salinity control studies that have provided sufficient design data for cost analysis. Cost-effectiveness values are steadily increasing (meaning a less favorable project), particularly for desalting plants and related structural features. The favorable cost- effectiveness for Paradox Valley is primarily due to the relative high concentration of the brine (260,000 mg/L total dissolved solids) and low flow to be disposed of in deep wells. The economi c benef its of sa 1 i nity control as measured by the economi c detriments which occur in the Lower Colorado River Basin have been under intensive evaluation by a consortium of Basin State universities. In a recent summary report, entitled "Colorado River Salinity - Economic Impacts of Agriculture, Municipal and Industrial Uses," [4] the consortium study established a composite value that reflects all the economic losses in the municipal, industri al, and agricultural sectors of the Lower Basin. The total economic losses because of increasing salinity levels in the Lower Basin are shown as a curvilinear function in figure 11. Over the relevant 14