C.R.C.P. 26(a)(2) Disclosures of The CWCB, Case No. 02CW38

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• feet. Out of the approximately 11.4 maf of water on average that originates in the Colorado River Basin in Colorado, between 2.2 and 2.4 maf is consumptively used by Colorado annually and approximately 9.2 maf on average flows out of the state either • for use in downstream states or for re- regulation at Lake Powell. D.. Fourth, the amount of water available for consumptive use in Colorado is also affected by unresolved legal interpretations of the "Law of the River." For example, whether of not surplus Colorado River System water exists and accordingly whether the Upper Basin has a liability for one -half of the Mexican Treaty delivery obligation every year. 4.4 Water Availability and Consumptive Use Investigations In 1995, the Colorado Water Conservation Board authorized a study of how much water was remaining for development in Colorado, in order to help determine how much water to appropriate for instream flows for the purpose of recovering Colorado River endangered fish. I was one of the principal investigators and authors of that study.. Recognizing many of the factors discussed above, the styidy made a number of conclusions regarding Colorado's entitlement under the "Law of the River." The study estimated that on a long -term average basis, Colorado's consumptive use entitlement is between 3.079 and 3.855 maf/yr. The actual amount available could be less or more in any ten -year period, depending upon hydrology and the determination of unresolved legal questions. The study calculated an "adjusted maximum consumptive use" in Colorado of 2.6 maf/yr based on existing uses, leaving approximately 450,000 af/yr, and potentially up to 1.227 maflyr, available for new development on an average annual basis. The study notes that there were a sufficient number of conditional water rights in existence at that time to more than fully develop Colorado's remaining Compact entitlement. I.1`oever, many of these conditional rights compete for the same water source or seek water from sources were significant new development will be difficult such as in the San Juan. Therefore, it is difficult to determine which rights will ultimately develop. In order to be conservative, we assumed some additional development would occur based on new water rights junior to a potential CWCB instream flow appropriation. The study recommended a "carve -out" or "development allowance" in each basin adequate to assure the flexibility of the state to continue developing Colorado's Compact entitlements. The study concluded that the state could make certain instream flow appropriations without impairing Colorado's ability to develop its Compact entitlement. For the Gunnison River Basin, this proposed instream flow appropriation was 1,655,888 to 1,781,873 maf/yr, or 70 -75% of the estimated average annual undepleted and unregulated flow of the Gunnison River at its confluence with the Colorado River. As an aside, gaged flow represents a regulated and depleted flow brought about by the activities of man. The Colorado Water Conservation Board after considerable discussion over a couple of years elected not to appropriate these instream flows and withdrew applications that had been filed on the 15 -mile reach of the Colorado and on the lower reach of the Yampa River. The volume of water passing at the Gunnison River near Gunnison, Colorado gage • l0 of 17