Using a Physically-based Model to Examine the Potential Effects of Climate Change on Ecologically Relevant Aspects of Streamflow Regime

Wednesday, 17 December 2014
Nazmus Shams Sazib1, David G Tarboton1, Sulochan Dhungel2 and Charles P Hawkins3, (1)Utah State University, Logan, UT, United States, (2)Utah State University, Civil and Environmental Engineering, Logan, UT, United States, (3)Utah State University, Department of Watershed Sciences, Logan, UT, United States
Climate change may affect ecologically relevant aspects of the streamflow regime. We used TOPNET, a physically based semi-distributed hydrologic model, to model 16 ecologically important aspects of the flow regime at eight watersheds that represented the range of streamflow regimes within the conterminous USA. The physical-based modeling was conducted to determine if previously developed statistical models could be used to predict shifts in flow regimes associated with climate change (stationarity is dead). TOPNET inputs were derived from Daymet climate data, SSURGO soil data, and National Land Cover (NLCD) data. USGS streamflow data were used to calibrate and validate each model for a separate period of record. The models were then driven by downscaled future climate data to project near (2046-65) and far (2076-95) future changes in the 16 streamflow regime variables. For most of the watersheds, the model performed well in calibration and validation and streamflow regime variables derived from calibrated flow compared well with those from the observed flow. A number of flow regime variables quantified magnitude aspects of the streamflow regime, and magnitude tended to increase with future climate change. Watersheds that exhibited increases in precipitation also exhibited increases in the number of high-flow events. We also found changes in timing quantified by the time of the water year by which 50% of the total flow has occurred. Snow-fed streams had earlier timing, whereas rainfall-driven systems had little change of time of 50% flow. These predictions of changes in streamflow regime variables due to climate change help understand how climate change may impact stream flows and hence stream ecosystems. Such considerations are important for water management and mitigation of the impacts of climate change on ecosystems .