Correspondences Concerning City of Denver's Use of Colorado River Water (2002)

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Ms. Maryanne C. Bach 12/28/2001 Page 3 Denver from reusing return flows from Colorado River water appropriated prior to May 1, 1940 unless acquired after 1940. In lieu of not reusing this water, Denver is not required to make evaporation releases at Antero, Eleven Mile, and Cheesman Reservoirs. Since Denver is effectively replacing these evaporation losses with a portion of return flows from Colorado River water, Denver is claiming successive use credit as shown in Column (2) of Table IV. An error was discovered during preparation of this year's report in the amount of evaporation credit claimed in the report for water year 2000. Evaporation credit was under - reported and thus, the total amount bf successive use was also under - reported. The following table shows the original evaporation credit reported in Table IV of the 2000 report and the corrected evaporation credit and the reported and corrected total successive use. TNY2000 Wl'2000 TNY2000 WY2000! Reported Corrected Reported Corrected Evaporation Evaporation Total Successive Total Successive Credit, Credit, lase, l Ise, acre-feet acre- feet acre- eet acre= eet 8,677 12,740 22,099 26,162 West Slope Storage The following information on Denver Water's west slope storage is provided for your information. Authorized storage in Dillon Reservoir on September 30, 2000, was 239,988 acre -feet and on September 30, 2001, it was 237,972 acre -feet, for a net change of -2,017 acre -feet. Similarly, on September 30, 2000, authorized storage in Williams Fork Reservoir was 73,455 acre -feet and on September 30, 2001, it was 64,051 acre -feet, a net change of -9,248 acre -feet. Successive Use Program Denver's main source of reusable water is the Colorado River basin although a small amount of reusable water originates from the South Platte basin. Reusable water returning to the South Platte River after use is termed reusable return flow. Reusable effluent is reusable return flow from sewered uses that returns to the South Platte via wastewater treatment plants. River conditions during June, July, and August of 2001 were favorable for exchanges frequently allowing Denver Water to exchange all available reusable effluent. Natural flows in the South Platte available for exchange receded in late August and early September. During the water year, Denver reclaimed 31,824 acre -feet of reusable effluent for beneficial use in the Denver metropolitan area. This, volume is 55% of the total Colorado River return flow in water year 2001. Average percent of return flow reclaimed