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the virgin flow. Beginning in 1962, part of this depletion at Lee Ferry was caused by the retention and storage of water in storage units of the Colorado River Storage Project. The horizontal line (at approximately 15 million acre-feet) shows the lo~g-term average virgin flow from 1896 through 1995. Because the Colorado River Compact is administered on the basis of running averages covering periods of ten years, the progressive ten-year average historic and virgin flows are displayed on this chart. The second chart on page 23, entitled Lee Ferry Average Annual Flow for Selected Periods, is a graphical representation of historic and virgin flow averages for several periods of record. The periods of water years selected were those to which reference is usually made for various purposes in documents pertaining to the Colorado River System. Several important hydrologic facts are apparent from these two charts on pages 26 and 27. (1) A vast majority of the high flows occurred prior to 1929. (2) Since the 1924-1933decade, the progressive ten-year average virgin flow has not exceeded the average virgin flow except in the 1941-1950 and the exceptionally wet 1975-1984through 1983-1992 decades. (3) For the period 1896-1921, which is prior to the Colorado River Compact of 1922, the average virgin flow was estimated to be 16.8 million acre-feet per year, which is considerably greater than for any other period selected, including the long-term average. A stream-gaging station at Lees Ferry, Arizona was not installed until 1921. Thus, the virgin flow at Lees Ferry prior to the 1922 Compact is estimated based upon records obtained at other stations, e.g. the stream gage on the Colorado River at Yuma, Arizona for the period 1902-1921. (4) For the longest period shown, 1896-1995, the estimated average annual virgin flow is 14.8 million acre-feet and the average annual historic flow is 12.2 million acre-feet. (5) For the next longest period, 1906-1995, the estimated average annual virgin flow is 15.0 million acre-feet and the average annual historic flow is 12.0 million acre-feet. Many of the early records for this series of years, as well as for the 1896-1995 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 1914-1995 period is 14.7 million acre-feet. This period is an extension of the 1 914-1 965 25