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<br />ie <br /> <br />. <br /> <br />. <br /> <br />,"". "~"""y <br />. ,1 .!. ':-=- <br />,..~.;~\.._~ j <br /> <br />land, which was estimated to average 1,250 mg/l over the first 45 <br />years of irrigation. Salt pick-up from newly irrigated land <br />draining this area would vary from 0.28 ton per acre annually in <br />the first year to less than 0.10 ton per acre annually in the 20th <br />year. No adverse effects on present or proposed project uses are <br />expected with this change. pesticides are not expected to be a <br />problem since baseline levels are at a minimum and improved <br />technology in the application of chemicals would probably enhance <br />their safe use. The nutrient and coliform organisms should not <br />cause serious instream problems, but the nutrient increase could <br />promote sporadic excess aquatic plant growth. <br /> <br />The major impact of project operation would be a salinity increase <br />in the La Plata River; because of the large quantity of salt <br />imported from the Animas River and re-use of project return flow, <br />the level of total dissolved solids at Farmington over a 45 year <br />period would increase from a flow-weighted average of 845 mg/l to <br />2,530 mg/l. Because of this increase the water could be used only <br />for salt tolerant crops on permeable soils with careful management <br />practices. Existing agricultural practices would not be severely <br />impacted because the crops presently grown and those proposed to <br />be grown during project operation would have a high salt tolerance. <br />Return flow from project land in New Mexico would carry <br />approximately 19,630 tons of salt annually, of which 5,050 tons <br />would be salt pickup from the application of irrigation water to <br />full service land and additional irrigation water on supplemental <br />service land. This salt pickup would vary from 1.1 tons per acre <br />in the eleventh year to less than 0.57 ton per acre after 50 years. <br /> <br />Southern ute Reservoir <br /> <br />Heavy metals and pesticides entering the reservoir will be <br />predominatly in suspended form and settle out in the reservoir <br />sediments. The average total dissolved solids concentration <br />predicted in the reservoir would be 670 mg/l. This concentration <br />would not vary significantly on a seasonal or annual basis. <br /> <br />Assuming increased nutrients in the La Plata River from the project <br />in addition to the current river concentrations, a worst case of <br />eutrophic conditions was predicted (Bureau of Reclamation, 1979). <br />Water from Ridges Basin Reservoir, which is low in nutrients, would <br />be imported into the river, diluting the nutrient level. The <br />unquantifiable nutrient loads from irrigated land and Ridges Basin <br />Reservoir leave some doubt as to the trophic state of Southern ute <br />Reservoir due to nutrient loads. The average yearly sediment <br />inflow would be approximately 39 acre feet and consist of 90 <br />percent silt and clay (Bureau of Reclamation, 1979). This periodic <br />sediment inflow would increase turbidity at the reservoir inlet <br />because of the high percentage of small diameter particles. This <br />seasonally high turbidity may cause light to be a physically <br />limiting factor of aquatic biota production (Welsh, 1952), thus <br />decreasing the possibility of eutrophic conditions in the <br />reservoir. The quality of water in Southern ute Reservoir should <br />be adequate for proposed industrial, agricultural, and recreational <br />uses. Periodic <br /> <br />14 <br />