Rio Grande - Rio Grande Reservoir Multi-Use Enlargement_Application Addendum

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Mr. Travis Smithl Superintendent October 16, 2003 Pag e 9 the Tres Rios terms and conditions in 1986, 19871 and 1997. The Rio Grande had annual credits in 1997 and 1998 and so credit water would have been available for storage in these years~ The amounts, of the credit water that were available in these years (1948, 1949, 1958, 1970, 1973, 19841 1997, and 1998) was estimated in essentially the same way as the water .available under the Tres Rios terms and conditions, Le., as the flow at Del Norte that exceeded the demands of the ditches. In this situation, however, the water was limited both to the outflow from Rio Grande Reservoi"r on a daily basis and to the Rio Grande's credit on an annual basis. Table 5 shows the monthly and annual storage volumes resulting from this analysis. Credit water was available for storage in 8 years in the period amounting to as much as 99,072 acre..feet in 1948. When spread over the 57-year period, it averaged 4,449 acre-feet annually. Of course, a reservoir enlargement of about 99,000 acre-feet would have been required to realize this full average. If the reservoir enlargement was less than about 99,000 acre~feet, some of the water could not have been captured and the average would have been smalleL DIRECT FLOW STORAGE We understand that an enlargement of Rio Grande Reservoir would provide additional reservoir capacity for Udirect flow storageu. The reservoir capacity could be used for this purpose not only by the District, but also by the Rio Grande Canal Water Users Association and the Commonwealth Irrigation Company. As discussed below, direct flow storage is recognized in decrees held by the District in Case No. W-3980, The Rio Grande Canal Water Users Association in Case No. W-39791 and by the Commonwealth Irrigation Company in Case No. 95CW18. The decree in Case No. W-3980 allows the District to store water available under its direct flow priorities 1903-178, 1903-22E, 1903OR24F, 1903-30F, and 1903-34G in Rio Grande, Santa Maria, and Continental Reservoirs when the flow at Del Norte, after curtailments are deducted, exceeds 2,285 cfs. The District has stored some direct flow water in the reservoirs under this decree since 1989. In this part of our investigationl vve calculated the volumes of additional direct flow water that were historically available for storage in an enlargement These were the volumes that were diverted into the Farmers Union Canal under the appropriate priorities. The calculations were made daily using Division of Water Resources records for the diversions of river water into the