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<br />O()23~2 <br /> <br /> 30 <br /> 28 <br />Z' 2. <br />0 . <br />i= 2. <br />~o: <br />>-UJ 22 <br />Zt: <br />UJ..J 20 <br />Uo: . /SMOOTHED CURVE LINE <br />ZUJ '8 <br />0"- / <br />UOl 18 . . <br />::;:::;: <br />:::><( 14 0/ <br />-0: . . <br />Z'" 12 <br />UJo . <br />..Jo: . . . <br />UJu 10 <br />Ol- . . . <br />6::;: 8 . . <br />UJz <br />>- . <br />..J <br />0 . <br />Ol . <br />Ol . <br />is 2 . . <br /> .. . . <br /> 0 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 <br /> CALENDAR YEAR <br /> <br /> <br />Figure 9.--Concentrations of dissolved selenium at streamflow gaging <br />station 09152500, Gunnison River near Grand Junction, 1975-88. <br /> <br />The water and salinity (dissolved-solids load) budget of the Uncompahgre <br />River from Colona to Delta is described in a report by the U.S. Bureau of <br />Reclamation (1984). That report discusses the quantity and sources of the <br />salt-load increase in the river in the Uncompahgre Project area. The U.S. <br />Geological Survey collected major-ion, dissolved-solids, and boron data at the <br />Uncompahgre River at Delta (gaging station 09149500) from 1958 to 1980. Mean <br />dissolved-solids concentration (120 samples) was 1,498 mg/L, concentrations <br />ranged from 485 to 2,530 mg/L, and most samples were a mixed-cation sulfate <br />water type. Boron concentrations ranged from 0 to 450 ~g/L. The Colorado <br />Department of Health also has collected selected trace-element data for the <br />Uncompahgre River at Delta and Ridgway (table 1). <br /> <br />Water-quality data for the tributaries and canals in the study area are <br />sparce. The U.S. Geological Survey collected water-quality data at two sites <br />on Spring Creek (fig. 1) from 1977 to 1981. One site was upstream from the West <br />Canal and, therefore, upstream from irrigated areas. The other site was near <br />the mouth of Spring Creek and was downstream from irrigated land on the west <br />side of the Uncompahgre Valley. The site near the mouth had greater concen- <br />trations of dissolved solids and nitrite plus nitrate than the upstream site. <br />Except for boron, trace-element concentrations at the sites were about equal, <br />and the concentrations were small. Maximum concentrations of selected trace <br /> <br />23 <br />