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<br />000796 <br /> <br />Colorado River Compact was being negotiated during the wet- <br />test 10-year period of record (18.8 maf fron 1914 to 1923). <br />Records indicate that the negotiators considered the average <br />flow at Lee Ferry to be between 16 to 18 maf which is <br />considerably greater than any other period after that time, <br />including the Bureau's estimated long-tern annual average of <br />14.8 naf and the period of actual record fron 1922 to 1977, <br />which averaged 13.7 naf. <br /> <br />Bureau estimates cb.~len'l~by <br />several groups <br /> <br />Considerable disagreement exists about future annual <br />river flows. Some people contend that because of the <br />highly variable historical flows, it is almost impossible <br />to predict accurate future average annual virgin flows. <br /> <br />The estimate of 14.8 naf, which the Bureau currently <br />uses in studies and planning for future water development, is <br />one of the nore optimistic predictions we noted. As shown <br />below, several other groups estimate the Colorado River's <br />average annual virgin flow as significantly less--up to 1.3 <br />maf less. <br /> <br />--Uppel. Colorado River Connission off icials stated that <br />they consider the gauged records for the 1922-77 <br />perioe] as the mOloe reliable and accept the estimate <br />of 13.7 maf as the future annual virgin flow. <br /> <br />I <br />I <br />~ <br /> <br />--Engineers froll the Lower Basin States testified before <br />the Congress during hearings for a 1968 act 1/ that <br />the virgin flow of the river was between 13.~ and <br />14.0 maf annually. <br /> <br />--Researchers at the Lahoratory of Tree Ring Research, <br />lJniversi ty of Arizona, have Llsed tree rinG (lata to <br />reconstrllct the C:olorarJo River's flO\~ for a 450-year <br />period. Using this data, they estimate the river's <br />nean annual flow to be 13.5 naf + .5 naf. The tree <br />rin'J studies sho,,, that the period 1930 to 1977 is <br />a norrnal period when viewed in the context of the <br />past few centuries. Using the Bureau's historical <br />data for this periorl, the averaqe annIJal virqin flo~l <br />waS 13.2 naf. <br /> <br />l/Colorae]o RivQr Basin Project Act; Pllblic Law 90-537, <br />32 Stat B85 (1968), (43 U.S.C. 1501). <br /> <br />8 <br />