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<br />Glenwood Springs area, hot springs increase the chloride and alkalinity concen-, <br /> <br /> <br />trations rapidly and significantly. The Roaring Fork River acts as a diluting <br /> <br /> <br />agent on the Colorado River at Glenwood Springs bringing about a reduction in the <br /> <br /> <br />chlorides and alkalinities. <br /> <br />. <br /> <br />Below Glenwood Springs, sandstone'and shale formations predominate. The <br /> <br />erodable nature of both rock formations and soil of the valley floors is evidenced <br />by the gradual increase of conductivity, hardness, chloride, and sulfate concen- <br /> <br />trations the farther west the sampling location is situated. <br /> <br />The Gunnison River also had a diluting effect on the water quality of the <br /> <br />Colorado River during the sampling period. Below the confluence of the Colorado <br /> <br />and Gunnison Rivers, decreases in dissolved salts and hardnesses were noted in <br /> <br />all samples. A long mixi,ng zone exists through tr.e Grand Junction area where the <br /> <br />water quality of the Colorado River changes dramatically from one side of the <br /> <br />River to the other as evidenced at Station CR-19 (Table 8). At this location <br /> <br />just downstream from the confluence of the two Rivers, the dissolved salt concen- <br /> <br />trations were 20-50% lower on the south side of the River due to the influence <br />of the softer waters of the Gunnison River. <br /> <br />Nitrogen concentrations also increased in the downstream portion of the study <br /> <br /> <br />area. The origin of the ni trogen below Cameo is not known at this time. The <br /> <br /> <br />presence of nitrites indicates the nitrogen has not been in solution for an <br /> <br /> <br />extended period of time since nitrite oxidizes rapidly to nitrate. Many factors <br /> <br /> <br />may increase nutrient concentrations in flowing waters including natural erosion, <br /> <br /> <br />leaching of fertilizers, sewage treatment plant effluents, runoff from livestock <br /> <br />holding areas, and irrigation return flows. <br /> <br />-2- <br />