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<br />f'- <br />C,l <br />.-I <br />.-l <br />C. <br />Co <br /> <br />IV. ANNUAL ESTIMATES FOR 1914-1951 PERIOD <br /> <br />The report on the water supply of the Lower Colorado River <br /> <br /> <br />Basin prepared in November 1952 by ,the Bureau of Reclamation <br /> <br />presented data: as averages for the 1914-1945 period and the fore- <br /> <br /> <br />going sections of this supplement have reported analyses based on <br /> <br /> <br />averages for the 1946-1951 period. This section of the supple- <br /> <br />ment describes the derivation of annual estimates of virgin flows <br /> <br />for water years 1914 through 1951 at eight selected points in the <br /> <br />Lower Colorado River Basin; namely: <br /> <br />(1) <br /> <br />(2) <br /> <br /> <br />(3) <br /> <br />(4) <br /> <br />(5) <br /> <br />(6) <br /> <br />(7) <br /> <br /> <br />(8) Colorado River at the International Boundary. <br /> <br />A. Annual Variations in stream Depletions <br /> <br />It is believed that depletions vary with the available water <br /> <br /> <br />supply. In years of abundant supply, there is a tendency to <br /> <br />/ <br /> <br />Colorado River at Lee Ferry, Arizona; <br /> <br />Little Colorado River at Grand Falls, Arizona; <br />Virgin River at Littlefield, Arizona; <br /> <br />Colorado River below Hoover Dam, Ari zona-Nevada; <br /> <br />Bill Williams River at Planet, Arizona; <br /> <br />Gila River at Gillespie Dam, Arizona; <br /> <br />Gila River near Dome, Arizona; and <br /> <br />divert more water than the optimum for the use requirements of <br /> <br />crops with consequent increased losses from evaporation and <br /> <br /> <br />incidental areas and increased storage in ground-water reservoirs. <br /> <br />Conversely, in years of short supply there are declines in water <br /> <br /> <br />use which are' often reflected in decreased crop yields and de- <br /> <br />creases in recharge to the ground-water basins. <br /> <br />18 <br />