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28 <br />26 <br />24 <br />22 <br />20 <br />w 18 <br />t- <br />J <br />cc <br />a 16 <br />cn <br />f- <br />Z <br />J 14 <br />Q <br />d 12 <br />W <br />J <br />J <br />g 10 <br />8 <br />6 <br />4 <br />2 <br />0 <br />EXPLANATION <br />Carbonate plus bicarbonate aMo <br />Sulfate <br />rn <br />¦ Chloride <br />Calcium 0) <br />Magnesium T <br />D Sodium plus potassium <br />(1966 - 83) Period of record <br />used for analysis 71 <br />N M <br />T <br />L to <br />- N , <br />to <br />T v <br />C" Cl) <br />C? n <br />Cl) On1 to <br />w <br />' W <br />O <br />O?1 0) L <br />00 <br />00 <br />JnEaFm <br />2 3 5 6 7 8 10 11 12 15 19 20 21 <br />SITE NUMBER (TABLE 3, PL. 1) <br />Figure 7. Mean chemical composition of dissolved solids at selected sites in Grand region. Cations on left, anions <br />on right. <br />Alva B. Adams Tunnel at East Portal near Estes Park, Colo. (site 1) <br />The gaging station at site 1 (table 3, pl. 1) monitors <br />water exported from Grand Lake. Although samples collected <br />at this site do not represent an actual streamflow, they do <br />represent the water quality in the headwaters of the Colorado <br />River. During 1976-83, the flow-weighted dissolved-solids <br />concentration averaged 29 mg/L (table 5), the lowest of any <br />site in the entire Upper Colorado River Basin. Chemical com- <br />position is predominantly calcium and bicarbonate. About <br />9,000 tons of dissolved solids is removed annually from <br />Grand lake through the tunnel. However, the principal effect <br />of this diversion is to remove relatively pure water from the <br />stream system. <br />22 Characteristics and Trends of Streamflow and Dissolved Solid <br />Colorado River at Hot Sulphur Springs, Colo. (site 2) <br />The streamflow at site 2 (table 3, pl. 1) is about 32 <br />percent of its preintervention quantity, mainly because of <br />exports through the Moffat Water Tunnel and the Alva B. <br />Adams Tunnel (fig. 8A). The mean annual flow-weighted <br />dissolved-solids concentration is 70 mg/L and the mean <br />annual streamflow is 196,000 acre-ft (table 5). Monthly <br />dissolved-solids concentration is relatively constant, vary- <br />ing between 59 and 89 mg/L. Calcium and bicarbonate are <br />the predominant ions throughout the year. From 1947 to <br />1983, annual monotonic-trend analyses indicated a signifi- <br />cant increase in median annual dissolved-solids concentra- <br />tion of 0.4 mg/L per year (table 6). This trend represents <br />s in the Colorado River Basin