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<br />I <br />r <br /> <br />. ,....~,~ <br />.' , <br />K...;..~ <br /> <br />CHAPTER 4 <br /> <br />HYDROGRAPHY <br /> <br />COLORADO RIVER AND COLORADO RIVER AQUEDUCT <br /> <br />COOPERATION was continued in 1948-49 with the U. S, <br />Geological Survey, as in previous years since 1935, in securing <br />adequate and accurate runoff and other stream gaging <br />records on the lower Colorado River and its tributaries. Valuable <br />and much appreciated help is also acknowledged in the form of <br />weekly and monthly river operation and evaporation reports of <br />the U, S, Bureau of Reclamation; climatological and runoff forecast <br />reporto of the U. S. Weather Bureau and the Soil Conservation <br />Service; and 1Il1merOUS "ther relmrb "f Federal, State and County <br />organizations on hydrographic data for Southern California or the <br />Colorado River. <br />Using preliminary unpublished data of the U, S. Geological Sur- <br />vey, subjed to later slight revisions, the discharge of the Colorado <br />River at Lee Ferry (the Compact division point between the upper <br />and lower basins) for the "water year" ending September 30, 1949 <br />was 14,360,000 acre-feet. This is about 670,000 acre-feet, or 5 <br />per cent more than for the preceding year, and is the highest <br />runoff in the last "even years, having been exceeded in only four <br />uf t.he last twenty years, <br />This season's l'llnoff is 103 pcr cent of the long-time mean <br />discharge of about 14.000,000 acre-feet at Lee Ferry (with present <br />upstream depletion) for the period 1905-1949. This "available" <br />flow is derived by "upplementing the record since 1922 with U, S, <br />Bureau of Reclamation and U. S, Geological Survey runoff estimates <br />for earlier years (based on records at other Colorado River gaging <br />stations) and then lldjusting for present increases in past upstream <br />depletions, by means of the Reclamation Bureau's studies and <br />computations. <br />The eotimated long-time mean flow, as corrected for present de- <br />pletion. of cour"e varies materially according to the base period <br />selected and the source of depletion and early flow records. Maxi- <br />mum variation is noted in cUl'I'ent publications of the U, S, Weather <br />Bureau (1949 western U. S. forecast), which report a normal flow <br /> <br />~ <br />f <br /> <br />( 65 1 <br />