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STATE OF COLORADO <br />Colorado Water Conservation Board <br />Department of Natural Resources <br />1313 Sherman Street, Room 721 <br />Denver, Colorado 80203 <br />Phone: (303)866-3441 <br />Fax: (303) 866-4474 <br />wuu . o~n cU. state. co.us <br />TO: Colorado Water Conservation Board <br />FROM: Steve Miller, Water Supply Protection Section <br />DATE: November 6, 2007 <br />Bill Ritter, Jr. <br />Governor <br />H:uris D. Sherman <br />DNR Executive Director <br />Dan McAuliffe <br />Acting CWCB Director <br />RE: Agenda Item 18b. November 14-15, 2007 Board Meeting <br />Water Supply Planning and Finance Section Referred Non-Reimbursable <br />Investments -Purgatoire River Water Conservancy District/CWCB Water Supply <br />Protection Section Purgatoire River Channel Capacity Improvements <br />Introduction <br />Trinidad Dam, a feature of the Trinidad Project impounds the Purgatoire River upstream of the <br />City of Trinidad providing flood control and irrigation water to the city and lands below, as <br />well as recreation and fishery benefits at Trinidad Lake State park. The project was built by <br />the US Army Corps of Engineers in the 1970's. The US Bureau of Reclamation is responsible <br />for the irrigation components of the project which are managed and repaid by the Purgatoire <br />River Water Conservancy District ("PRWCD"). Pursuant to the Arkansas River Compact the <br />project is considered a post compact development, and may not materially deplete useable <br />Stateline flows beyond historical consumptive uses that occurred prior to 1949. Flood control <br />operations at Trinidad must therefore pass all flood inflows at the maximum possible rate <br />limited only by the safe channel capacity through Trinidad in order to not deprive downstream <br />rights, including John Martin Reservoir, an opportunity to utilize historical flood flows. <br />USBR, the Corps, Kansas, and the PRWCD are currently engaged in a Ten Year Review of <br />project operations including the issue of flood releases and safe channel capacity. <br />Discussion <br />Since construction of the dam the channel below the reservoir has deteriorated due to <br />vegetative encroachment, flow management, and land use changes. It is now believed that the <br />channel cannot carry the design flood release of 5,000 cfs, and it there is uncertainty as to <br />whether the currently designated release rate of 3,000 cfs can be safely carried. The Corps has <br />instructed dam operators to not exceed a 1,000 cfs rate until qualified observers can be on site. <br />This ratcheting down of the release rate is of concern to downstream water users, particularly <br />the State of Kansas, who benefit from high flood flows, but understand the life and property <br />Water Supply Protection • Flood Protection • Stream & Lake Protection • Rater Supply Planning & Finance <br />Water Conservation & Drought Planning • Intrastate Water Management & Development <br />