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, . . . . . lIICIQ.o MAR 1 2 '90 COLORADo CON--. WATER BOvATION AR.ro Streamflow Needs of Rare and Endangered Fishes: Yampa River Interim Flow Recommendations FINAL REPORT by U.S. Fish and Wildlife Service, Region 6 Denver, Colorado 80225 March 5, 1990 Introduction The Green River basin is the last remalnlng stronghold of the Colorado squawfish (Ptvchocheilus lucius) and the razorback sucker (Xvrauchen texanus) in native riverine environments. It also supports populations of the humpback chub (Gila ~) and is a recommended recovery area for the bony tail chub (Gila eleqans). Flows of the Yampa River, last free-flowing river containing endangered fish habitat in the Upper Colorado River Basin, are considered critical to the maintenance of usable fish habitat of rare and endangered fishes (Figure I) in the Green River basin (reviewed by Tyus and Karp 1989). Typical flows in the Yampa River begin to rise from winter baseflows in late March and continue to rise through May. The annual peak at Deerlodge Park usually occurs during the end of May and continues into the first week of June. Peak flows at Deerlodge Park typically range from 7,748 to 20,476 cfs (75-25% exceedence values), and the lowest peak flow recorded was 3,821 cfs, and the highest was 33,200 cfs (1977 and 1984, respectively). In early to mid-June flows begin a steady decline through August, subside to base flows in September and continue at baseflow through the remainder of the year. The lowest base flow recorded at Deerlodge Park was 43 cfs on September 5 and 6, 1988. The Recovery Implementation Program (RIP), a cooperative effort between Federal and State governments, water and power users, and conservationists (U.S. Fish and Wildlife Service 1987), outlined procedures to protect four rare and endangered fishes in the Upper Colorado River Basin. One of these is the provision and maintenance of instream flows at certain times, locations, and quantities, as necessary. The Yampa River was subsequently identified by the cooperators as the highest priority area for investigating opportunities to acquire instream water rights for the endangered fishes. A three-step process was recommended to quantify the flow need of the fish in the Yampa River: (1) an evaluation of habitat use, potential limiting factors, and general flow needs relative to the maintenance and recovery of the endangered fishes and supporting aquatic habitat; (2) quantification based on the best available information and knowledge of the identified flow needs with respect to the quantity, duration, and timing of flows; and (3) identification of future studies necessary to refine or corroborate existing flow recommendations developed in Step 2 above. Step 1 has been accomplished with a 1989 publication "Habitat use and streamflow needs of rare and endangered fishes, Yampa River, Colorado" (Tyus and Karp 1989), This report provides Step 2 by providing interim flow recommendations which are based on our best available data and understanding of the Yampa River system and the needs of the fishes in question.