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<br /> <br />Causes and Impacts of Salinity <br /> <br />I ~ <br />0' Municipal and Industrial Sources of Salinity <br />..J <br />~ J Salts contnbuted 1O the Colorado RIVer System by M&I sources are generallY minor. lOraling about <br />I percent of the Colorado Ri'er Basin salt load (or 3 percent of the salinity) loms estimates ,hat <br />~\&I users increased salintly by about 100 lOns per 1.000 people in the Colorado RIVer Basin <br />(Iorns. et al. 19651. The population reported for 1990 for ,he Upper Colorado Ri,er Basin ""as <br />about 609.000 people. conmbuting about 61.000 lOns per year of salt loading. At the present rate <br />of population grow'h. M&I sources would increase salinity by approximately 133.000 lOns per year <br />by the year !OIO. However. most municipal ""astewater IS relati,e1y low in salt concentration in <br />companson 1O natural. industrial. and agricultural sources. and are no' generally cost effective 1O <br />control. Complete elimination of such waste discharges would be expensive when compared to <br />other s.alimty control melhods.. <br /> <br />Consumptive Use of Water Increases Salinity <br /> <br />Addtlion of salts to ,he river system is no' ,he only cause of increased salimty in ,he Colorado <br />River Basin The consumption (depletion) of water reduces the dilution of saline inflo""s to ,he <br />r"er system. increasing the concentration of saltni,y. Water use is evaluated as part of <br />Reclamation's responSibilities m managing the nver sysrem. The Colomdo R"" Syswn. <br />Co",u"'p,..e Uses and Losses Repon summarizes water use m the Colorado River Basin (Bureau of <br />Reclamation. 199\). Table! on the following page averages the Colorado RI,er Basin uses <br />,including triburanes 1O the Colorado River in the Lower Colorado Ri'er Basm) Work has been <br />recently completed updallng the report through 1990. Work is under""ay to update these estimates <br />through \995. <br /> <br />With the excep,ion of the Central Arizona Project tCAP). the Lo""" Colorado River Basin has <br />already developed most of Its water supply. The CAP is the last major development 1O deplete <br />water from ,he Lower Colorado Ri,er. Agnculture use is the single largest source of deplellons to <br />the Colorado Ri,er. Exports. resenoir evaporation. and M&I uses also account for lesser but <br />sigmflcant depletions. <br /> <br />~lost of the exportS from the Upper Colorado Ri,er Basin are made at higher ele'ations where the <br />salinity concentrations are ,ery low. ThIS loss of high quality water results in the remaining flows <br />downstream becoming more concentrated. Water exported from ,he Upper Colorado River Basin <br />during the period 19a1.n a,eraged about 360.lXlO acre-feet per year laf/yn. Completion of such <br />large projects as the Colorado-Big Thompson. Duchesne Tunnel. RobertS Tunnel. and more recent <br />projects Increased expons to about 70~.OOO aflyr in lQ90. <br /> <br /> <br /> <br />13 <br /> <br />