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. . I. SUMMARY AND RECOMMENDATIONS Operation of the Orchard Mesa tailrace "check" and by-pass channel in the manner described in this report results in an opportunity to re-use power and pumping water for irrigation under junior water rights. If the "check" is not used for this purpose, the junior rights will call for administration of the Colorado River system upstream from Palisade and make substantial withdrawals of stored water in Green Mountain Reservoir. Without the "check" in operation, water passing through the Orchard Mesa Power Plant and water used to provide lift through the Orchard Mesa Irrigation District's hydraulic-turbine pumps is returned directly to the Colorado River below the Grand Valley Irrigation Company's diversion dam. By improving and maintaining the by-pass channel from the tailrace check structure to the Colorado River, all or part of the power/pumping water can be provided above the Grand Valley Irrigation Company's diversion. Depending on final operating capacity of the by-pass channel, a benefit equivalent to 20,000-30,000 acre-feet of reservoir storage may be achieved through operation of the "check." Use of the "check" to provide water to junior rights results in reduced efficiency of the Orchard Mesa Irrigation District's hydraulic pumps, and prevents the District from providing a full water supply to its service area. It also reduces efficiency of the hydroelectric plant, resulting in diminished revenues. While there are circumstances which require the District to operate the "check" by contract, and times the District prefers to use the "check" to maximize power generation opportunities, there is no legal requirement to use the "check" to benefit junior rights. / Historically, and particularly in the 1977 drought year, the Orchard Mesa Irrigation District did utilize the "check" to benefit junior rights without compensation for maintenance or reduced pump/power plant efficiency. Water users in the Colorado River basin, and especially those who depend on Green Mountain Reservoir for late-season water supply, have come to depend on use of the "check" to effectively reduce the downstream river call and insure efficient use of the limited amount of water available. A recent interpretation of river administration policy at the state level indicates that the Orchard Mesa Irrigation District is under no obligation to operate the "check" for junior rights, and that the agreement between Orchard Mesa and the Grand Valley Water Users' Association for sharing shortages by operating the "check" is a private agreement, not administerable by the state. - 1 -