WSP10375 - Laserfiche WebLink

Home Browse Search

. . . . . EFFECT OF 1991 FLOW RELEASES FROM RUEDI RESERVOIR ON ENDANGERED FISH HABITAT IN THE IS-MILE REACH BY Douglas B. Osmundson Fishery Biologist George R. Smith Hydrologist U.S. Fish and Wildlife Service Background The IS-Mile Reach of the Colorado River between Palisade, Colorado, and the confluence of the Colorado and Gunnison Rivers at Grand Junction is important habitat for the endangered Colorado squawfish and razorback sucker (Osmundson and Kaeding 1989). Management of the reach during the summer months is primarily aimed at providing quality habitat conditions for adult Colorado squawfish (Kaeding and Osmundson 1989). Using the Physical Habitat Simulation Method (PHABSIM), Hann and Rose (1989) determined that the maximum amount of run, pool, and riffle habitat for adult Colorado squawfish in the IS-Mile Reach occurs at flows of 1000 cubic feet per second {cfs}, while 9S percent of the maximum available habitat occurs at flows between 700 and 1200 cfs. Kaeding and Osmundson {1989} recommended that 700-1200 cfs be provided in the IS-Mile Reach during the July-September period during years of normal or of above normal precipitation. During dry years, when the flow recommendation would be more difficult to meet, 600 cfs was considered an acceptable lower limit for the flow window. In a later report (Osmundson and Kaeding, 1991), the Service recommended extending the same flow recommendations to the end of October for the benefit of adult Colorado squawfish. These fiow recommendations were reviewed by the staff of the Board and ultimately accepted by the Board as being acceptable for appropriating and acquiring water. In 1989, the Bureau of Reclamation began releasing water from Ruedi Reservoir during the summer months to supplement flows downstream in the IS-Mile Reach to help meet the habitat needs of the endangered fish. During 1989 and 1990, 10,000 acre feet {ac ft} of water per year was released from Ruedi Reservoir for this purpose. An additional 10,000 ac ft (a total of 20,000 ac ft) was released from Ruedi Reservoir pursuant to a three party agreement signed by Reclamation, Service, and the Board in September 1991. This report briefly summarizes the extent to which the 1991 Ruedi releases helped meet the targeted July-October flow regime in the IS-Mile Reach and thus benefitted the endangered fish in the IS-Mile Reach.