Rio Grande - Rio Grande Reservoir Multi-Use Enlargement_Application Addendum

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Mr. Travis Smith, Superintendent October 16, 2003 Page 8 Grande Reservoir are that it would suffer evaporation at a smaller rate and that it would not be subject to spill from Project Storage. It is noted that Colorado had a credit of 53,200 acre-feet in Project Storage at the end of 1994 that was lost in the 1995 spill. The storage of Colorado credit water would be achieved by holding the water in storage, equal to the amount of the anticipated credit in the compact accounting. To the ~xtent the water is held in the reservoir enlargement, the delivery obligation would be calculated under Article III as if the water had not been held in storage. If the water is released in a subsequent year, it would add to the physica-I water supply in the Rio Grande, but not to the delivery obligation, since the delivery obligation had been paid on the water in the year it was held in storage. We have assumed here that only Rio Grande credit water as determined by the Rio Grande's separate Compact accounting would be available for storage in the reservoir enlargement Under the current Compact administration, curtailment of Colorado water uses should not result in significant credits under the Compact. Consequently, credit water would have' been available for storage in the reservoir enlargement primarily when the existing reservoirs fined or would have filled under current Compact administration. In addition to the years when Project Storage spilled, Rio Grande Reservoir filled or nearly filled in 1948-49, 1952, 1957-58, 1962~ 1965~ 1970, 1973, 1997, and 1998. As noted above, water years 1946-67 were essentially without Compact adn1inistration and some relatively large debits occurred and accrued as a result Inspection of the annual reports of the Rio Grande Compact Commission showed that '. the Rio Grande had annual credits in only 1948, 1949, and 1958. Therefore, credit water would have been available for s~orage in the reservoir enlargement in these three years. As indicated previously, water years 1968-85 was a period of administration under the 1968 Stipulation with New Mexico and Texas and significant curtailments were made to Rio Grande water uses. Our examination of the Compact accounting and our curtailment calculations indicated that Rio Grande Reservoir would have filled in 1970 and 1984 in addition to 1973 and 1985 when the reservoir filled historically. Water would have been available to the reservoir enlargement in 1985 under the Tres Rios terms and conditions as discussed earlier. Therefore, credit water could have been stored in the reservoir enlargement in 1970, 1973, and 1984. r ' ~ l'>\f :~ In the period of current Compact Administration after 1985, Rio Grande Reservoir filled in 1986i 1987 t 1995, 1997, and 1998. Water was available to the reservoir enlargement under