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<br />14.6 million acre-feet. This period is an extension of the 1914-1965 period <br />used in the Upper Colorado Region Comprehensive Framework Studies <br />of 1971. The average annual virgin flow for the 1914-1965 time period is <br />14.6 million acre-feet. <br /> <br />(7) The average annual virgin flow for the period 1914-1945 is 15.6 million <br />acre-feet. This was the period of record used by the negotiators of the <br />Upper Colorado River Basin Compact of 1948. <br /> <br />(8) For the period 1922-2004, which is the period of record since the signing <br />of the Colorado River Compact, the average annual virgin flow is 16.8 <br />million acre-feet and the average annual historic flow is 10.9 million acre- <br />feet. Records for this series of years are based upon actual <br />measurements of flows at Lees Ferry. The ten-year moving average flow <br />since 1922 is considerably less than the ten-year moving average flow <br />prior to 1922. <br /> <br />(9) Two completely unrelated ten-year periods of minimum flows have <br />occurred since 1930. During these periods, 1931-1940 and 1954-1963, <br />the average annual virgin flow amounts to only 11.9 million acre-feet. <br /> <br />(10) For a 12-year period, 1953-1964, the average annual virgin flow amounts <br />to only 11.6 million acre-feet. <br /> <br />(11) Since Glen Canyon Dam was closed in 1963, the estimated virgin flow for <br />the subsequent 41 years is 14.3 million acre-feet. The estimated historical <br />flow for the same period (1963-2004) is 9.8 million acre-feet. <br /> <br />26 <br />