Laserfiche WebLink
<br />r- r, ~ <br /><; .j .J ;. <br />74 .. MET R 0 P 0 Lf TAN IV.~ T E R D r -' T R leT <br /> <br />filling will cause an increased futUl'e deposit of silt in the active <br />storage (except as this is prevented or postponed by upstream <br />reservoir construction). The usable storage contents as of October <br />1, 1949 were reduced by 3.1 per cent, or 0.2 per cent per year. <br />The original usable capacity of the reservoir was reduced by 2.8 <br />per cent. or 0.2 per cent per year on the average. <br />Lake Mead storage capacity reduction by sedimentation remains <br />a serious future problem, affecting the long-range security of all <br />lower Colorado River water projects. But as determined by the <br />recent survey the problem and all its implications for the future <br />are so much less alarming and severe than has generall,v been <br />presented publicly by numerous enthusiastic prophets of doom. <br />as hardly to be recognizable as referring to the same reservoir <br />and ri vel'. <br /> <br />Colorado River 'Iuater fJ71al:ity <br /> <br />The outflow from Lake Mead, which furnishes the water supply <br />fo)' Lake Havasu and the Metropolitan Water District aqueduct, <br />as well as numerous other diversion,g, wa~ again much improved <br />and averaged considerably lower in hardness and salinity during <br />the water year to September 30, 1949. This was due to slightly <br />above normal runoff in 1V49 following the near-normal runoff of <br />1947 and 1948, which have offset the effects of previous deficient <br />runoff since 1942 and resulted in great progress in completing the <br />leaching and flushing of gypsum and other dissolved solids from <br />the lower storage strata in Lake Mead. <br />At the aqueduct intake above Parker Dam, monthly :;amples <br />show a total hardness averaging 011 parts per million for ]949 <br />compared with 324 for 1948, 385 for 1947 and a record of 420 <br />in April 1941, just prior to the first filling of Lake Mead. Similarly. <br />total dissolved solids averaged 619 parts pel' million at the aqueduct <br />intake in 1949, compared with 647 in 1V48 and 682 in 1947, which <br />in turn represented a decrease of 160 parts per million from the <br />maximum of April 1941. As regards the major constituents suI. <br />fates ",'eraged 265 parts per million in 1949, or 16 less than in <br />1948 and 31 less than in 1947. Chlorides in 1949 averaged 70 <br />parts per million. or 4 less than in 1948 and 12 less than in 1947. <br />Temperature of the diverted aqueduct water averaged 650, vary- <br />ing from H minimum of 420 in midwinter to a maximum of 840 in <br />July and August 1V49. At Hayfield, the last of the aqueduct pump- <br />ing plants, the water pumped averaged 610 in temperature, varying <br />seasonally from p. to 70 (monthly averages) cooler than Lake <br />