Limestone-Graveyard Creeks Watershed Plan and Environmental Assessment

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C! L 1 �u 05 5 WATERSHED PROBLEMS AND OPPORTUNITIES This section identifies the types of problems which exist in the watershed. The problem areas are identified and the extent of the problems within each area are quantified. Potential opportunities to improve the quality of life and enhance environmental values are also discussed. The problems within the watershed quantity, and irrigation induced rural water quality, and fish and Water Ouality include: water quality, water erosion. Additional problems include wildlife habitat. Local geology and current land use practices are adversely affecting the water quality of the surface drainage and groundwater. Salts are a water and soil quality problem in the basin. During the last several years, there has been an increasing indication of heavy metals in irrigation drainages and the Arkansas River. The Colorado Nonpoint Assessment Report identified sediment and salinity as water quality problems in the reach of the Arkansas River which is impacted by the project. The drains in the project area are major contributors of heavy metals, salts, and sediment. As observed by USGS 3 , dissolved uranium and selenium shows a particularly strong positive correlation with specific conductance. The study shows strong positive correlations with sodium, magnesium, sulfate, and chloride that contribute heavily to total dissolved solids and specific conductance in these waters. Lithium, boron, strontium, iron and selenium are also positively correlated. The combination of natural weathering of heavy metal bearing soils and sediments, extensive soil leaching by irrigation waters and evaporative concentration in a semiarid climate produce concentrations of dissolved heavy metals may threaten local water supplies. The Department of Interior also has studied water quality of the Arkansas River in the vicinity of the project. 2/ Concentrations of sulfate, boron, and uranium were present in waters that drain from irrigated land underlain by marine shales. Selenium was the only inorganic trace constituent associated with irrigation drainage that was found at significantly elevated concentrations in water, bottom sediment, and biota. Selenium is an element which is subject to bioaccumulation in the food chain. Selenium becomes concentrated in green plants as they take up water. 4/5/6/ As drains within the irrigation system pick up water, selenium concentrations can become high and a health hazard for humans and other animal life. The Colorado Department of Public Health and Environment dissolved selenium standard for aquatic life, which pertains to Class I and Class II streams, is 17 micrograms /liter. The EPA STORET data set had 17 values collected from 1988 through 1992 for the Lamar, Colorado gaging site. The mean value was 12.9 micrograms /liter. The data show the levels of dissolved selenium are high, and on occasion, exceed the 14