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<br />ELIMl1"\l b. t~-\/ <br />PR - 1 1 "J_~r"'t'"",~_ <br /> <br />..........,,--...~.'.:..,,( <br />\~. '....j 1 ", . <br /> <br />Ie <br /> <br />overgrowth of aquatic plants, however, is possible in the reservoir <br />because of nutrient concentrations introduced into the reservoir. <br /> <br />Mancos River <br /> <br />Irrigation return flow from land on the ute Mountain ute Indian <br />Reservation and a part of the non-Indian land adjacent to the <br />reservation would increase the total dissolved solids concentration <br />and salt loading in the river. Bureau of Reclamation studies <br />(1979) indicate that the salt pickup from the irrigated project <br />land would vary from 0.89 ton per acre in the first year to less <br />than 0.10 ton per acre in the twenty-third year. <br /> <br />As on the La Plata River, unquantifiable increases in the amounts <br />of nutrients, pesticides, coliform organisms, and trace metals <br />(iron, manganese, and aluminum) are probable as the newly irrigated <br />land is agriculturally developed. No problems are predicted with <br />these increases with the anticipated uses of the water. <br /> <br />San Juan River <br /> <br />:e <br /> <br />It is expected that the project would have a small effect on the <br />long-term water quality of the San Juan River. Increases, <br />presently unquantifiable, in nutrients, trace elements, coliform <br />organisms, and pesticides could be attributable to the project. <br />No major problems are anticipated with these increases, because of <br />the present uses of the water and the treatment of domestic water. <br />The average annual salinity in the river at Bluff, Utah, would be <br />increased after 45 years of project operation from a current flow- <br />weighted average of 470 mg/l to 520 mg/l. The following table <br />shows the average annual salt tonnage and flow-weighted total <br />dissolved solids concentration for the Animas, La Plata, Mancos, <br />and San Juan Rivers with and without the project. The project <br />averages represent an average over 45 years of simulated project <br />operation. <br /> <br />Average annual salt tonnage and flow-weighted <br />average of total dissolved solids concentration <br /> <br /> Without With <br /> oro;ect oro;ect <br /> Salt TDS Salt TDS <br /> (tons) (mg/l) (tons) (mg/l) <br /> Animas River at Farmington 215,000 275 167,000 295 <br /> La Plata River at Farmington 20,000 845 27,000 2,530 <br /> Mancos River north of State <br /> line 43,000 1,195 55,000 1,255 <br /> San Juan River at Bluff, <br />I. Utah 1,006,000 470 1,005,000 520 <br /> <br />15 <br />