Rio Grande - Rio Grande Reservoir Multi-Use Enlargement_Application Addendum

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ML Travis Smithr Superintendent October 16, 2003 Page 11 Company must divert Priorities No. 361-A and 361-8 for 10 cumulative days or 8 consecutive days prior to the beginning of direct flow storage, must forego storage of 13 percent of the storable flow, and are subject to an 11 percent charge for conveyance losses when the water is released from storage. A maximum of 8,700 acre-feet may be stored per water year. Tables 8 and 9 show the additional water that would have been available to the Rio Grande Canal Water Users Association and Commonwealth Irrigation Company for direct flow storage during the 1946-2002 irrigation seasons. As shown in Table 8, the additional water available to the Rio Grande Canal Water Users averaged 23,297 acre-feet annually and ranged from none in 1977 2002 to 72,065 in 1965. In Table 9, the additional water available to the Commonwealth Irrigation Company averaged 4,433 acre-feet annually. Amounts ranged from none in four different years, most recently in 2002, to the maximum allowed of 8,700 acre-feet in eight years, with the most recent occurrence in 1995. CONCLUSIONS 1. We believe that storage in an enlargement of Rio Grande Reservoir under a post- compact water right would be limited to years when either Project Storage in Elephant Butte and Cabana Reservoirs spills or 'when Colorado achieves an annual credit of 150,000 acre-feet or more. Historically, during water years 1946-2002, Project Storage spined in 1985, 1986, 1987, and 1995, and Colorado did not achieve an annual credit of 150,000 acre-feet or more~ Consequently, water would have been available for storage in a post-compact reservoir only in 1985, 1986J 1987, and 1995 and the amounts, which are shown in Table 4, ranged from 30,850 acre-feet in 1995 to 73~082 acre-feet in 1985. 2~ We believe there would be benefits to Colorado and the Rio Grande water users in having additional reseJVoir capacity available for storage of uCompact waterH. Specifically, we believe additional reservoir capacity would facilitate storage of Compact water to reduce changes in curtailments during the course of the irrigation season, the storage of Compact water during years of high flow to reduce the losses delivering the Compact water to the State Line, and storage of Rio Grande credit water, which would reduce evaporation losses and eliminate the chance of spilr from Project Storage.