Author(s): Rohan Benjankar; Daniele Tonina; Andrew W. Tranmer; Matthew G. Tiedemann; Peter Goodwin
Linked Author(s): Peter Goodwin, Rohan Benjankar, Daniele Tonina
Keywords: Deadwood River; Hydrodynamic and temperature modeling; Dam release; Flow regime; Dam impact; Thermal regime 1
Abstract: Dam operations have altered the thermal regime of streams worldwide with adverse effects on fish habitat that force aquatic species to change their habitat. However, impact assessment is typically based on comparing dam operations with historic scenarios and does not account for climate variability. Here, we investigate the effect of dam operations on the riverine thermal regime and available wetted areas under three climate scenarios. We constructed a wet, dry and average year based on historic hydrological data to understand whether dam operations may minimize the effect of climate variability. Our study site is a 38km long reach of Lower Deadwood River between Deadwood Reservoir and the confluence with the Payette River. The Deadwood Reservoir is operated as a retention basin for irrigation purposes with releases during the summer months. We developed a hydraulic and temperature model for the stream under two different dam operations, which were compared with a reconstructed unregulated hydro- and thermo-graphs. Results show that dam operations shift temperature and hydraulic cues from summer months into the fall. Extension of warmer water temperatures into the fall season could provide stable and predictable cues for riverine organisms that may use it in lieu of the warm unregulated summer period.