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<br />N <br />en <br />C1) <br />t-+........ <br /> <br />Indications from several studies are that physical <br />damages due to salinity may not be strictly <br />proportional over the range of TDS in question. <br />It is believed that a curvilinear function may more <br />adequately approximate the actual situation. <br />However. until more evidence is assembled to <br />support otherwise. estimation of damages for <br />planning purposes will be based on an average <br />value per milligram per liter (linear relationship) <br />for the appropriate TDS interval. <br /> <br />D. Industrial Damages <br /> <br />It is apparent that water treatment costs vary <br />among firms and industries because of the <br />specific nature of water quality requirements. <br />Since the final product or service is subject to <br />satisfying a wide variety of final uses. the quality <br />of input water mayor may not be of major <br />importance. <br /> <br />Based on available information related to <br />industrial impacts. salinity is not believed to be <br />a major problem when compared to the <br />associated damages of municipal and <br />agricultural users. Therefore. appropriate <br />allowances have been made in the municipal <br />damage estimates until more reliable industrial <br />values become available. <br /> <br /> <br />Salt accumulated in tile drains, Imperial Valley, <br />California. <br /> <br />1 <br /> <br />E. Total Economic Impacts Due to <br />Changes in Salinity Levels <br /> <br />Calculation of the total economic impacts of <br />changing salinity levels on the Colorado River <br />must be made with regard to present and future <br />expected levels of TDS. <br /> <br />A summary of total estimated economic impacts <br />both direct and indirect. is given in table 12 for <br />selected salinity levels over the range 800 to <br />1400 mg/L. These impacts represent the <br />negative externalities on a milligram-per-liter <br />basis associated with the different levels of TDS. <br /> <br />V, APPLICATION IN PROJECT <br />ANALYSIS <br /> <br />Applications of the values contained in table 12 <br />must be made with reference to the relevant <br />range of TDS which is from 875 mglL (present <br />limits) to 1225 mg/L which is Water and <br />Power's best estimate of salinity at full <br />development with no mitigation measures <br />employed. The estimates in table 12 are plotted <br />in figure 1 with the relevant salinity range <br />indicated. Given the goal of the salinity control <br />program of maintaining salinity at or below <br />present levels, the total potential economic <br />benefit or damage becomes the area under the <br />curve between 875 and 1225 mg/L (fig. 1). <br />Using the linear least-squares-fit as opposed to <br />the actual exponential function provides an <br />equally valid estimate of the area under the <br />curve-roughly $ 2 57.000 per mg/L direct and <br />$ 343.000 per mg/L total. <br /> <br />In order to simplify subsequent analysis by using <br />a constant number to apply to all proposed <br />salinity schemes. it seems reasonable to use the <br />average economic impact rather than ordering <br />development through time and showing a larger <br />dollar impact for projects later in <br />implementation. Under the assumption that the <br />salinity standards will be met. such an approach <br />becomes valid and rational. given the physical <br />relationships are accurately defined. <br /> <br />Using the information given in figure 1 with <br />current interest rates and 50-year planning <br />horizon. the total magnitude of the salinity <br />problem On the Colorado River is estimated to be <br />about $ 1.8 billion. <br /> <br />16 <br />