Impacts of in-stream flow requirements upon water temperature in the central Platte River

The central Platte River experiences high water temperatures during many sunny, hot summer days. This paper investigates whether instituting a minimum streamflow for the river can mitigate the higher water temperatures. A 150-km reach of the central Platte River downstream of two hydropower dams (Kingsley Dam and North Platte/Keystone Diversion Dan), which serves as a habitat for eight federally listed threatened or endangered species, as well as over 300 species of migratory birds, including 500,000 sandhill cranes and 7-9 million ducks and geese was selected for the study. A dynamic water temperature, model, MNSTREM, was used to simulate hourly water temperatures in the central Platte River with and without in-stream flow requirements. It is found that the occurrence of high water temperatures can be reduced but not eliminated with minimum in-stream flow requirements.