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for justification of a water supply for the Central Arizona Project authorized in <br />1968. <br />(6) The estimated average annual virgin flow during the 1914-1998 period is 14.8 <br />million acre-feet. This period is an extension of the 1914-1965 period used in the <br />Upper Colorado Region Comprehensive Framework Studies of 1971. The <br />average annual virgin flow for the 1914-1965 time period is 14.6 million acre-feet. <br />(7) The average annual virgin flow for the period 1914-1945 is 15.6 million acre-feet. <br />This was the period of record used by the negotiators of the Upper Colorado <br />River Basin Compact of 1948. <br />(8) For the period 1922-1998, which is the period of record since the signing of the <br />Colorado River Compact, the average annual virgin flow is 14.4 million acre-feet <br />and the average annual historic flow is 11.1 million acre-feet. Records for this <br />series of years are based upon actual measurements of flows at Lees Ferry. The <br />ten-year moving average flow since 1922 is considerably less than the ten-year <br />moving average flow prior to 1922. <br />(9) Two completely unrelated 10-year periods of minimum flows have occurred since <br />1930. During these periods, 1931-1940 and 1954-1963, the average annual <br />virgin flow amounts to only 11.8 million acre-feet. <br />(10) Fora 12-year period, 1953-1964, the average annual virgin flow amounts to only <br />11.6 million acre-feet. <br />(11) Since Glen Canyon Dam was closed in 1963, the estimated virgin flow for the <br />subsequent 35 years is 14.9 million acre-feet. The estimated historical flow for <br />the same period (1963-1998) is 9.9 million acre-feet. <br />26 <br />