In-stream flow impact on river water temperatures

The Central Platte River often experiences high water temperatures during s unny, hot summer days. A 128-km reach of the Platte River downstream of two hydropower dams (Kingsley Dam and North Platte/Keystone Diversion Dam) was studied to determine the relationship between river summer water temperatu res and river flow-rate, and the impacts of in-stream flow requirements upo n peak water temperatures. This reach serves as a habitat for eight federal ly listed or endangered species, as well as over 300 species of migratory b irds, including 500,000 sandhill cranes and 7-9 million ducks and geese. Ho urly water temperatures were simulated using a dynamic numerical model (MNS TREM) with and without in-stream flow requirements. It was found that a cle ar relationship exists between river water temperatures and river flow-rate . In addition, it was found that the occurrence of high water temperatures can be attributed to low river flow-rate and can be reduced, but not elimin ated, with minimum in-stream flow requirements.