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MI?81 COLORADO RIVER COMPACT WATER DEVELOPMENT PROJECTION November 2, 1995 FINAL REPORT Page 11 IV. COLORADO'S COMPACT APPORTIONMENT Duringthe 1922 Compact negotiations, it was believed that the long-term average water supply at Lee Ferry, Arizona was greater than 15.0 MAF per year and that there would be at least 7.5.MAF annually available for use in the Upper Basin. Furthermore, it was believed that there was at least enough water originating in the Lowel( Basin to satisfy the Mexican Treaty obligation of 1.5 MAF annually and satisfy an additional 1.0 MAF of annual conswnptive use in the Lower Basin. Under the above asswnptions, Colorado would have at least 3,855,375 acre feet of annual conswnptive use available to it. However, it has become apparent that long term water supply conditions were overestimated and that the average annual water supply at Lee Ferry is ouly approximately 15 MAF, which is insufficient to meet the Mexican Treaty obligation and provide 7.5 MAF of consumptive use to both the Lower and Upper BaSins. .. In addi~on, the 1922 compact made the 7.5 MAF apportionments to each of the Upper and Lower Basins from the waters of the "Colorado River System." The "Colorado River System" isdef/ned in the 1922 compact as "that portion of the Colorado River and its tributaries within the United States of America." However, the 1964 decree in Arizona v. California only allocated 7.5 MAF among the Lower Basin states from the Colorado River mainstem, and.refused to apportion the use of Lower Basin tributaries. Consequently, the Long Range Operating Criteria provide that at minimnm 8.23 M1V be released annually from Lake Powell (7.5 MAF to the Lower Basin plus .75 MAF for one- half the Mexican Treaty obligation less .02 MAF of tributary inflow between Glen Canyon. ' and Lee Ferry). Although the Secretary of the Interior has disclaimed any intent to interpret the "Law of the Colorado River" in promulgating the criteria, the criteria effectively require the Upper Basin to deliver annually one-half of the Mexican Treaty obligation at Lee Ferry. It should be emphasized that the Upper Basin States have never agreed to or concurred with the concept of supplying one-half of the Mexican Treaty obligation each and every year. These varying asswnptions of water supply and interpretation of the Mexican Treaty obligation result in different interpretations of the water supply available to the Upper Basin and Colorado lis shown in Table 2 below. <" ~ .,-'-,,,-,',,. .. . i', ,1 ~ ;", .,',1 "I ,'t: ~, :.; '1; , 'il , 8 ':$ ,'~ . ,i . <'j