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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I' <br />I <br />I <br />I <br />I <br />'I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />o <br />en <br />N <br />-.J <br /> <br />- <br /> <br />-202- <br /> <br />APPENDIX 2 <br /> <br />DESCRIPTION OF PL 93-320 SALINITY CONTROL <br />PROJECT IN UPPER COLORADO RIVER BASIN <br /> <br />NONPOINT SOURCE SALINITY CONTROL PROJECTS <br /> <br />The Granq Valley <br />The Granq Valley (Figure 2-1) is locateq in west <br /> <br />central Coloraqo near the western edge of Mesa County, and <br /> <br />receives an average annual precipitation of only 210 rom. <br />Grand Junction, the largest city in Colorado west of the <br />Continental Divide, is the population center of the valley. <br />The valley was carved in the Mancos shale formation by the <br />Colorado River and its tributaries. The Colorado River <br /> <br />enters the valley from the east, is joined by the Gunnison <br /> <br /> <br />River at Grand Junction and then exists to the west. <br /> <br />Salinity Contribution-- <br />The Grand Valley was identified as an important agri- <br />cultural source of salinity in the Colorado River Basin <br />through a water and salt mass balance. Iorns et al. (1965) <br />evaluated stream gaging records for the 1914 to 1957 period, <br />concluding that the net salt loading (salt pickup) from <br />irrigation ranged from about 450,000 to 800,000 Mgm annually. <br />Similar analyses by Hyatt et al. (1970), Skogerboe and <br />Walker (1972), and the WOI, Geological Survey (1976) sub- <br /> <br />stantiated this range of salt loadings. Most studies indi- <br /> <br />cate an average, long-term salt pickup rate of between <br /> <br />600,000 to 700,000 Mgm/yr. This mass of salts is added <br />