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<br />In addi tion to downstream effects, the depth of wi thdrawal in <br />reservoirs has become a significant issue concerning the productivity of <br />reservoir fisheries, eutrophication, nutrient retention, salinity routing, <br />esthetics, and evaporation.(S] At present, there are concerns about <br />evaporation, temperature, and nutrient processes in Fontenelle and Flaming <br />Gorge Reservoirs, Lake Powell, and Lake Mead. <br /> <br />2. Economic <br /> <br />.....,. <br />CO In the Lower Basin, present peak salinity is app.roaching critical <br />en levels for some salt sensitive crops. While the water is suftable for <br />~ irrigact.ing most crops, salinity is hjgh enough that spedal irrigation <br />practices are necessary in some cases. At the present time, salinity is being <br />maintained below the standards. Complete development of apportioned water by <br />the States will result in increases in salinity that would be more detrimental <br />to agriculture without salinity control measures. <br /> <br />A consortium of water resource centers in the States of Arizona, <br />California, Colorado, and Utah cooperated in a study funded by the Office of <br />\later Research and Technology and the Bureau of Reclamation to assess the <br />economic damages caused by various salt concentrations to agricultural and <br />municipal water users. This study is documented in a report, Salinity <br />Management Options for the Colorado River, \later Resources Planning Series <br />Report P-78-003, June 1978.(6] <br /> <br />Based upon the findings of that report, Reclamation has published a <br />summary working document entitled, Col~rado River Salinity--Economic Impacts <br />on Agricultural, Municipal, and Industrial Users.[7] The estimated future <br />annual damages to the Lower Basin water users in 1976 dollars wel'e $343,000 <br />for each 1 mg/L increase in TDS at Imperial Dam when concentrations reach the <br />range of 875 mg/L to 1,225 mg/L. The damage figure is approximately $610,200 <br />per, mg/L in 1986 dollars. These annual damages were calculated using the 1972 <br />salinity standard of 879 mg/L (approved by EPA in 1975) and a projected full <br />development salinity concentration of 1,225 mg/L at Imperial Dam. <br /> <br />The annual municipal damages are divided as follows: Metropolitan <br />\later District, 54 percent; Central Arizona Project, 8 percent; and lower main <br />stem users, 8 percent. T~tal agriculture annual damages are 30 percent. <br />Industrial impairments and Upper Basin dallliig.::s were not cvaluat~d, <br /> <br />Estimating Economic Impacts of Salinity of the Colorado River [33] <br />summarizes findings from a study designed to develop a method of forecasting <br />economic impacts of salinity of the Colorado River upon various users of <br />Colorado River water in the southwestern United Sta~es; One objective was to <br />update, revise, clarify, and ~efine the estimates of economic damages from <br />salinity in the Coloiado R{ver that had been described in earlier studies. <br />Another objective was to provide a better means of estimating present and <br />future salinity damages, basically through the development of a comprehensive <br />and user-friendly personal computer program. A final objective addressed <br />unresolved questions and issues about Colorado River salinity, including areas <br />of damage not previously included in estimates. <br /> <br />The present (1986) damages from salinity are conservatively <br />estimated at $311 million per year. Studies are underway to update the future <br /> <br />IV-4 <br />