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• Dissolved solids concentrations showed incremental increases of 40 mg/i to 50 mg/1 per <br />mile of flow. These increases represented the inflow of total dissolved solids from <br />groundwater seepage, agricultural drainage, dissolving elements found in the streambed, and <br />the concentrating effect of evaporation of the stream water. <br />Seasonal water quality variations in the streams were evident in the sample results. As <br />streamflow decreased to the baseflow period of fall and winter, the stream source changed <br />from mainly surface runoff caused by snowmelt and rainfall to mainly groundwater seepage. <br />This change is reflected by changes in water quality. Alkalinity, which is a measure of <br />dissolved carbonate and bicarbonate ions, showed somewhat of a direct relation to the <br />proportion of surface runoff and decreased in the fall. Sulfates, which are the product of the <br />oxidation of sulfur minerals and are typically found in groundwater, increased in the fall. <br />These changes usually occurred as surface runoff decreased, rather than as groundwater flow <br />increased. Magnesium and sodium also showed seasonal fluctuations, with magnesium <br />decreasing and sodium increasing in the fall. Chloride concentrations decreased in the fall in <br />a manner similar to other elements, but with somewhat different timing. <br />Iron was present in normal quantities. Since no deposits of "iron boy" were observed along <br />any of the streams, acid drainage problems are not evident or expected. All the cadmium, <br />lead, chromium, and arsenic results were below their respective toxic thresholds of 0.01 <br />mg/l, 0.03 mg/l, 0.05 mg/l, and 1 mg/1 (NAS, 1972). In addition, all the mercury and <br />selenium analyses were below their toxic thresholds of 0.00005 mg/I and 0.23 mg/1, <br />respectively, as indicated by the presence of aquatic fife. Toxicities of zinc and copper vary <br />• widely in water of different hardness. Laboratory experiments and field bioassays have <br />shown high levels of calcium, such as those found in these drainages, to inhibit the toxicity of <br />these metals. Based on hardness and alkalinity [he waters in these drainages are not toxic [o <br />aquatic life. No unusual water quality constituents were detected by this sampling program. <br /> <br />2.04.7-69 <br />