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<br />~~ !,_~ .tJ ::~ ; <br /> <br />WATERSHED PROBLEMS AND OPPORTUNITIES <br /> <br />Water Qualitv <br /> <br />There is a concern that the local geology and current land use practices are adversely affecting the <br />water quality of the surface drainage and groundwater. Salts have long been known to be a water <br />quality problem in the basin. However, during the lastseveral years, there has also been an <br />increasing indication of nutrients and trace minerals in irrigation drainages and the Arkansas River, <br />and of its potentially harmful effects on human health,fish and wildlife, and agricultural uses. The <br />Colorado Nonpoint Assessment Report identified sediment and salinity, as well as other water quality <br />problems, in the reach of the Arkansas River which is impacted by the project. <br /> <br />Intensive irrigation of highly fertilized crops dominate the land use in the watershed. Irrigation waters <br />percolate through the soils and flow down gradient through unconsolidated gravels into the <br />groundwater. <br /> <br />There are a number of wells in the area that are high in nitrates. From various data sources, 20 wells <br />in the watershed were found to exceed the state and EPA standards (10ppm); this is approximately <br />1/3 of the wells tested. The Arkansas River's water approaches the state nitrate level standard at <br />times. <br /> <br />Nutrient levels are high not only due to commercial fertilizer application, but also to manure <br />application. There are approximately 40 cattle feeders in the watershed. Management of the <br />combination of nutrient sources is necessary to ensure that the nutrient level applied is at the correct <br />proportions. <br /> <br />According to a Department of Interior study, selenium was found at elevated concentrations in water, <br />bottom sediment, and biota of the Arkansas River. Selenium concentrations in surface water was 1 <br />mlcrogram/liter in Pueblo Reservoir upstream of the project area. Data indicates that the stretch of <br />the Arkansas River from the Highland Canal diversion to the water quality gauge at La Junta, which is <br />affected by the Highline Breaks area, has a significant change in selenium concentrations. Samples <br />taken at these 2 gauges (Nepesta and La Junta) show that the average total selenium concentration <br />increases from 8 micrograms/liter to 17 micrograms/liter between the gauges. EPA data shows <br />similar increases. <br /> <br />Salinity is another serious water quality problem in the Arkansas Valley. There are 3 important <br />factors in the salinity problem: salt pick-up, salt concentration, and the management of water, soils, <br />and <br /> <br />crops. Since no standards exist, this project is not formulated to reduce salinity. Though, it is <br />desirable to control salt loading, high salt levels will remain as long as the water is used. The <br />greatest potential for reducing salinity is through more effectively using water throughout the valley. <br />Irrigation water diverted has a mean TDS of 600 milligrams/liter (obtained from USGS records). The <br />mean TDS in the Arkansas River at La Junta, which is just below the project area, is 1040 <br /> <br />7 <br />