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<br /> <br />Canal and from Mexico through the Alamo and New Rivers, and the tonnage <br />removed from the Valley to Salton Sea. Until 1949, the amount removed each <br />year was less than that brought in. However, commencing in 1949, there has <br />been a favorable salt balance. As the drainage system is extended the per- <br />centage of gain should increase. <br /> <br /> Tons of Salt Tons 01' Salt Gain or <br />Year into LV. into Salton Sea Loss <br />1948 2,744,000 2, 630J 000 4.15% loss <br />1949 2,659,119 2,800,165 5.30% gain <br />1950 2,793,780 2,931,431 4.93% gain <br />1951 3,189,765 3,213,686 0.75% gain <br /> <br />III - QUALITY OF COLORADO RIVER WATER <br /> <br />Areas Served by Lower Colorado River <br /> <br />The water for all purpOSe$ in Imperial Valley and Mexicali Valley _ <br />domestic, irrigation, and industrial - is supplied from Colorado River. There <br />is no potable underground supply. In Coachella Valley, the underground water <br />is mostly of good quality and, prior to completion 01' the All~American Canal, <br />was the sole source of supply. HmTever, it is sufficient for only 12,000 to <br />15,000 acres, whereas under full development about 100,000 acres will be <br />irrigated. The supply for the additional 85,000 acres will have to be from <br />Colorado River. In addition, the Colorado will supply water to 400,000 <br />acres in: other irrigation projects on the lower river in the United States, <br />and over 1)000,000 acre-feet a year for domestic and industrial use on the <br />coastal plain of Southern California. <br /> <br />Salinity of Colorado River Water <br /> <br />Prior to control 01' the River by Hoover Dam, the salt content of <br />the water varied from 150 parts pel' million during flood season to 1000 parts <br />per million during low flow periOds. In droughts, as in 1924 and 1934, the <br />content reached 2000 parts per million during short periods. Storage of <br />flood watel'S behind Hoover Dam created a gigantic mixing bowl, so nmT ther.e <br />is little variance in the salt content 01' the lower river. For several years <br />it has averaged 700 parts per million, or roughly one ton of salt per acre- <br />foot 01' water, a satisfactol'y quality for irrigation and domestic purPoses. . <br />No difficulty would be anticipated with water 01' this quality on.the projects <br />below HOOVer Dam. <br /> <br />Future Quality <br /> <br />There is now coming into Lake Mead 12 or 13 million tons of salt <br />annually. It is believed that this tonnage will not change lIll1ch as develop- <br />ment in the Upper Basin proceedeJ although the amount of water carrying it <br />will be decreased by the additional upstream consumption. Substantial <br />changes are likely in the perc.entage.s of various chemicals in the water; <br />for example the percentage of sodium as compared to calci1llll and magnesi1llll. <br /> <br />-29- <br /> <br />