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obtained at other stations, e.g. the stream gage on the COIOla.... River at Yuma, Arizona for the period 1902-1921. (4) For the longest period shown, 1896-1987, the estimated average annual virgin flow is 15.1 million acre-feet and the aver- age annual historic flow is 12.5 million acre-feet. (5) For the next longest period, 1906-1987, the estimated average annual virgin flow is 15.2 million acre-feet and the aver- age annual historic flow is 12.4 million acre-feet. Many of the early records for this series of years, as well as for the 1896- 1987 period, are based upon the estimates of flows made at other gaging stations, as mentioned in (3) above. This average is about equal to the 15.0 million acre-feet estimated for the 1906-1967 period which was used as the basis for justification of a water supply for the Central Arizona Project authorized in 1968. (6) The estimated average annual virgin flow during the 1914-1987 period is 14,9 million acre-feet. This period is an extension of the 1914-1965 period used in the Upper Colorado Region Comprehensive Framework Studies of 1971. The average annual virgin flow for the 1914-1965 time period is 14.6 million acre- feet. (7) The average annual virgin flow for the period 1914-1945 is 15.6 million acre-feet. This was the period of record used by the negotiators of the Upper Colorado River Basin Compact of 1948. (8) For the period 1922-1987, which is the period of record since the signing of the Colorado River Compact, the average annual virgin flow is 14.4 million acre-feet and the average annual historic flow is 11.3 million acre-feet. Records for this series of years are based upon actual measurements of flows at Lees Ferry. The ten-year moving average flow since 1922 is considerably less than the ten-year moving average flow prior to 1922. (9) For the 58-year period, 1930-1987, the annual average virgin flow dropped to 14.1 million acre-feet. (10) Two completely unrelated ten-year periods of minimum flows have occurred since 1930. During these periods, 1931- 1940 and 1954-1963, the average annual virgin flow amounts to only 11.8 million acre-feet. 28 ~