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<br />. <br /> <br />. <br /> <br />. <br /> <br />"""" <br />o <br />~n <br />1;,0 <br /> <br />CAUSES OF SALINITY (continued) <br /> <br />the downstream reaches. This concentrat ing effect occurs to a gr~ater <br />degree when the diverted salts return to the river than when they are <br />depleted along with the water. <br /> <br />1. In-basin Depletions <br /> <br />Consumptive use of water for irrigation within the basin is respons- <br />ible for the largest deplet ions while municipal and industrial uses <br />account for a le.sser dep let ion. Evaporat ion from reservo ir and st ream <br />surfaces also produces 1 arge deplet ions. Phreatophytes cause sign if icant <br />water- Losses by evapotranspiration, especially in the Lower Basin below <br />Hoover Dam. In most cases where in-basin depletions occur, the diverted <br />salts return to the river system, adding significantly to the increase in <br />concentration. Only in the case of Large industries such as steam power- <br />plants are the salts depleted along with the water. <br /> <br />2. Transbasin Depletions <br /> <br />The major part of the transbasin depletions are made at higher eleva- <br />tions where the salinity concentrations are very low. This removal of high <br />quality water results in the remaining flows downstream becoming mor-e <br />concentrated even though some salts are rem0ved by the water dclivcr~d to <br />another basin. Many transbasin diversions have been made for several years <br />and an add it ional number will divert in the future. The largest future <br />diversions will be by the Bonneville Unit of the Central Utah Project, the <br />Denver-Englewood and Homestake Diversions, the San Juan-Chama Project, and <br />the Fry ingpan-Arkansas Project, all of wh ich are present ly divert ing some <br />water. <br /> <br />33 <br />