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<br />w <br />00 <br />CD <br />,.I::. <br /> <br />~~., Under this scenario, both the initial Forum legislation <br />authorizing five Interior units and the USDA legislation are enacted, and <br />all of the planned and authorized projects are implemented. This alterna- <br />tive is composed of scenario 3 plus Reclamation's agricultural projects on <br />the Lower Gunnison Basin and McElmo Creek Units, industrial use options for <br />the Price, Las Vegas Wash, and Big Sandy River Units, and BLM's Sinbad Valley <br />Unit. Under this alternative, the USDA projects in Big Sandy River and <br />Price River were res coped to reflect the alternative industrial use of <br />saline agricultural drain water. <br /> <br />Figure 9 summarizes the salt tonnage removed under scenario 4, including <br />Interior, USDA, and total program impacts. <br /> <br />"1:~jl"~ ji".!2This alternative is composed of scenario 4 plus all <br />~!e' lIi"ti' "a1''''Reclamation projects now conceived. These are the <br />Glenwood Springs, Dirty Devil, Palo Verde Irrigation District, and <br />Uinta Basin Water Quality Improvement Projects. <br /> <br />Figure 10 summarizes the maximum salt tonnage removed for scenario 5 <br />projects, including Interior, USDA, and total program effects. <br /> <br />Figure 11 shows a comparison between the Forum and Reclamation depletion <br />schedules for the Upper Basin. The low rate Forum projection and the <br />Reclamation schedule bracket the complete range of depletion assump- <br />tions currently under consideration. They diverge a maximum of approxi- <br />mately 430,000 acre-feet per year, or 10 percent, after the year 2000. <br /> <br />Figure 12 displays the effect of depletions on base case projections of <br />salinity at Imperial Dam using the Forum low and Reclamation depletion <br />schedules. The Reclamation schedule approximates the Forum's high depletion <br />schedule. Differences in depletion assumptions have only a minor effect on <br />salinity projections. Although the Reclamation schedule had higher deple- <br />tions, as shown in figure 11, there was relatively little difference in <br />the salinity at Imperial Dam when compared to the Forum assumptions. <br /> <br />As a general assumption, all industrial uses were assumed to have zero <br />discharge of salt and water to the Colorado River system, except at the <br />Four Corners Powerplant. This was necessary because sufficient data <br />are not available for most present uses to determine what, if any, salt <br />load is returning to the system. An improved NPDES inventory would aid <br />in this aspect of modeling the system. <br /> <br />For these simulations, the natural hydrological data base from 1906-1983 <br />was used, with a mean natural flow at Lee Ferry of 15 million acre-feet <br />per year. For each scenario, 15 runs were made, each using a different <br />hydrology starting date to provide 15 estimates of future water quality <br />and quantity. This can be useful in assessing the range of future <br />salinity conditions due to hydrologic variation. <br /> <br />.j <br /> <br />Figure 13 shows the effects of the hydrologic assumptions at Imperial Dam <br />for the worst salinity conditions (3 driest years), the best salinity <br />conditions (3 wettest years), and the mean range of salinity conditions. <br />Note the much wider range of salinity projections contrasted with varia- <br />tions caused by the depletion schedules shown on figure 12. <br /> <br />31 <br />