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<br />N <br />CJ1 runoff. Each of the four years has had a natural flow in <br />W <br />o excess of 20 million acre-feet, with a four year average of <br /> <br />22.6 million acre-feet. Only one other period has had 20 <br /> <br />million acre-feet of natural flow for two or more consecutive <br /> <br />years--1920 and 1921 and only one period (1920-1923) had an <br /> <br />average natural flow exceeding 20 million acre-feet (20.4 <br /> <br />million). During 1983-85 the annual calendar year flow to <br />Mexico exceeded scheduled deliveries by 12.6, 13.8 and 10.1 <br /> <br />million acre-feet respectively. <br /> <br />Storage Changes <br /> <br />upper and Lower Basin reservoir storage has increased <br /> <br />since 1972 as shown on Figure 1. Basinwide storage at the <br /> <br />end of calendar year 1985 was about 15.6 million acre-feet <br /> <br />greater than at the end of 1972. Of the total increase, 10.6 <br /> <br />million acre-feet was in the Upper Basin and 5.0 acre- <br /> <br />feet was in the Lower Basin. The 1985 end of calendar year <br /> <br />storage in the Colorado River system was about 730,000 acre- <br /> <br />feet less than the 1984 value. <br /> <br />Dur ing water year 1986 most of the major reservoirs on <br /> <br />the Colorado River were again filled to capacity and flows <br /> <br />well in excess of demands were released. These continued <br /> <br />large flows produced reductions in salinity concentrations in <br /> <br />all of the major reservoirs. <br /> <br />Historical Uses <br /> <br />Estimated histor ical Lower Basin mainstream and Upper <br /> <br />Basin uses for calendar years 1973 through 1985 are shown on <br /> <br />Table 3. <br /> <br />-3- <br />