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FROM'RES. RIGHTS TO:CWCB 002u7;' AUG 12. 1994 1:10PM ~479 P.04 BACKGROUND INFORMATION -- UPPER GUNNISON_RIVER Questions about the use of water from the Upper Gunnison River Basin cannot be considered in a vacuum. The Gunnison is a part of the Colorado River system. Colorado must meet both compact obligations and endangered fish species recovery goals for the ~stem as a whole. If Colorado fails to look at the entire Colo- rado River system, water development in one area might have undesirable compact or endangered species effects for the entire state. Thus, Upper Gunnison River issues must be evaluated in light of the following considerations: 1. gnused C~lorado Ri~er water flowing_out of the state does not mean that .Colorado..,lS losing water to unchecked develop- ment in the Lower Basin. First, water leaving Colorado is cap- tured in 25 miilion acre-foot Lake Powell, where it serves as Upper Basin drought insurance. Because the upper Basin must de- liver 75 MAF to the I.ower Basin every ten years, carryover stor- age in Lake Powell assures that that delivery obligation is met without curtailing existing Upper Basin uses. This is crucial during low-flow years such as 1987-1992 (the six lowest consecu- tive runoff years of record). For example, in 1990, inflows to Lake Powell were only 5.1 MAF -- Lake powell storage made up the rest of the required delivery to the Lower Basin. Second I water releases from Lake Powell are subject to strict statutory and ad- Rlinistrative controls under the 1968 Colorado River Basin Project Act and the 1970 Operating Criteria. The criteria provide for a minimum release of only 8.23 MAF except under carefully defined circumstances. Third, water released from Lake Powell is cap- tured by Lake Mead, where releases are again subject to statutory controls and a Supreme Court decree. Unless a surplus is de- clared -- which has never happened to date -- Lower Basin uses from Lake Mead are limited to 7.5 MAF/year. While California has been using more than its decreed apportionment, it has used Arizona's unused Lower Basin apportionment. The low demand for exp'ensive Central Arizona Project water means California may be able to use Arizona's unused apportionment well into the future. Further, California has acknowledged its responsibility to live within its apportionment and has undertaken a number of conserva- tion measures and transfers in order to work towards that goal. 2. St..~tements that large amounts of Colorado I s compact ~ portionment remain unused may be inaccurate. It is difficult to qua'ntify with preciSion-how much "unused apportionment" remains. Because the virgin flow of the Colorado River was overestimated when the '1922 Compact was negotiated, the reliable supply availa- ble to the Upper Basin (and Colorado, proportionately) is less than the 7.5 MAF/year apportioned by the compact. How much less