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<br />... ' <br /> <br />01201 <br /> <br />, <br />United States Department of the Interior <br />u.s. GEOLOGICAL SURVEY <br />SOUTHWEST BIOLOGICAL SCIENCE CENTER RECEIIIED <br />GRAND CANYON MONITORING AND RESEARCH CENTER A <br />2255 NORTH GEMINI DRJVE, MS-9394 f'R :2 5 2001: <br />FLAGSTAFF, ARIZONA 86001 eN ;) <br />~orado ~ <br />928 556-7094 Telephone at.rCons"""H <br />928 556.7092 Fax on Boarrf <br /> <br />April 20, 2005 <br /> <br />MEMORANDUM <br /> <br />To: <br /> <br />Glen Canyon Dam Adaptive Management & Technical Workgroup <br />Representatives and Science Advisors <br /> <br />From: <br /> <br />Ted S. Melis, Integrated Science Program Manager & (acting Chief) <br /> <br />Subject: <br /> <br />Distribution of article by Korman et aI., entitled "Modeling effects of discharge on <br />habitat quality and dispersal of juvenile humpback chub (Gila cypha) in the <br />Colorado River, Grand Canyon" <br /> <br />The attached article has been accepted by the GCMRC as a final report relating to one element of the 2000 <br />Low Summer Steady Flow experimental trealment (LSSF). This information relales to a fishery modeling <br />effort Ihat explored Ihe relationship between Glen Canyon Dam operations (steady and fluctuating flows) <br />and downstream physical habitat availability along the rivcr. The study also utilized a multidimensional <br />flow-field model, originally developed 10 support sediment Iran sport research, to assess the potential for <br />sub.adult humpback chub in Ihe main channel of the Colorado River ecosystem to access, low.velocity, <br />near-shore habitats below Ihe Little Colorado River confluence during LSSF flows, Thesc simulations <br />assumed varied swimming abilities associated with fishes of varied life-stages (larval, young-of.year and <br />juvenile) leaving Ihe spawning tributary and entering the Colorado River. <br /> <br />Take Home Message: Suitable shoreline habitat (as determined for humpback chub during the EIS) <br />declined with rising stage, but Ihese changes were highly variable from reach to reach and were <br />particularly sensitive to local morphology. Hourly variation in discharge from the dam substantially <br />reduced the amount of persis lent shoreline habitat in all reaches. Dam operations tended to reduce habitat <br />availability in fall and winter, but habitat availability was actually increase during spring months, Success <br />in finding low-velocity habitats is greatly increased when fish have even rudimentary swimming mobility, <br /> <br />Examole of Integrated Science: These simulations provide an example of how numerical tools can be used <br />to support integrated science planning for future flow.based experimcnlal treatments, Combined usc of the <br />stage and unsteady-flow algorithms in this research demonstrates that the same flow simulations can <br />providc insighl into questions about the timing and magnitude of dam releases with respect to benefiting <br />both native fish and fine sediment below the dam. <br /> <br />Please review this report and feel free to conlact me at (520) 556.7282, with any questions you have, Mr. <br />Korman and Dr. Wiele can be reached at (604) 737-83\4, (520) 670-6671, ext. 277, respectively. Both <br />authors will make presentations on Ihis research at the May 2005, Technical Workgroup meeting (as part <br />ofGCMRC's Knowledge Assessment workshop, convened in support of experimental planning), <br />