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Show APPENDIX XII XII-49 Introduction The Colorado River system is composed of portions of seven States-Arizona, California, Colorado, Nevada, New Mexico, Utah, and Wyoming. It has a drainage area of about 242,000 square miles and represents about one-fifteenth of the area of the United States. This report incorporates annual estimates of consumptive uses and losses of water from the system from 1971 to 1975. Wherever available, water use reports prepared in accordance with legal requirements concerning the operation of the Colorado River were utilized. Base data needed to estimate onsite consumptive uses were taken largely from existing reports and studies and from ongoing programs. Where current data were not available, estimated values were developed by various techniques and reasoned judgment. No new surveys or special studies were undertaken for this initial report. In general, methodology followed the techniques normally used within the system for estimating water use. Nothing in this report is intended to interpret the provisions of the Colorado River Compact (45 Stat. 1057), the Upper Colorado River Basin Compact (63 Stat. 31), the Water Treaty of 1944 with the United Mexican States (Treaty Series 994; 59 Stat. 1219), the decree entered by the Supreme Court of the United States in Arizona v. California, et al. (376 U.S. 340), the Boulder Canyon Project Act (45 Stat. 1057), the Boulder Canyon Project Adjustment Act (54 Stat. 774; 43 U.S.C. 618a), the Colorado River Storage Project Act, (70 Stat. 105; 43 U.S.C. 620), or the Colorado River Basin Project Act (82 Stat. 885; 43 U.S.C. 1501). Authority The authority for this report is contained in Public Law 90-537, the Colorado River Basin Project Act of 1968. Title VI, section 601(b)(l) of the act reads as follows: (b) The Secretary is directed to- (1) Make reports as to the annual consumptive uses and losses of water from the Colorado River system after each successive five-year period, beginning with the five-year period starting on October 1, 1970. Such reports shall include a detailed breakdown of the beneficial consumptive use of water on State-by-State basis. Specific figures on quantities consumptively used from the major tributary streams flowing into the Colorado River shall also be included on a State-by-State basis. Such reports shall be prepared in consultation with the States of the lower basin individually and with the Upper Colorado River Commission, and shall be transmitted to the President, the Congress, and to the Governors of each State signatory to the Colorado River Compact. Plan of Study After initial meetings with representatives of the Lower Basin States and the Upper Colorado River Commission, a proposed plan of study was presented for comment. Comments received largely concerned water accounting procedures, particularly the lack of uniformity and consistency within the system. This issue is longstanding and is related to the interpretation and implementation of the legal documentary controlling the operation of the Colorado River. In November 1974, a preliminary report was prepared which included estimates of beneficial consumptive use. Comments received from the States were essentially the same as for the plan of study. In the Upper Basin, the principal comment concerned the use of 1965 data bases developed for the Upper Colorado Region Comprehensive Framework Study, particularly irrigated acreage. In the Lower Basin, the main concerns were the lack of credit for unmeasured return flows originating from mainstream diversions and the failure to quantitatively recognize that ground water overdraft in the Gila River Basin satisfies a major portion of the beneficial consumptive use. To the degree possible, these concerns are addressed within this report. UPPER COLORADO RIVER The major tributary streams selected as reporting areas in the Upper Colorado River Basin are: Green River (Wyoming, Utah, Colorado); Upper Main Stem (Colorado, Utah), and San Juan-Colorado (Colorado, |