Sensitivity of Winter/Spring Hydrologic Processes to Climate Change in a Temperate Climate

Wisconsin's hydrology is dominated by winter/spring processes. While winter precipitation totals are lower than during the summer months, the accumulation of water in snowpack and its subsequent release onto frozen soils during the spring melt event make temperature-related processes responsible for many of the largest floods in the state, and the majority of annual groundwater recharge. We developed warming scenarios based on the downscaled GCM data available from the North American Regional Climate Change Assessment Program, which were then applied to a one-dimensional physical-process hydrologic and thermal model, Simultaneous Heat and Water (SHAW). SHAW was selected as one of the few hydrologic models capable of modeling soil frost formation and melting, and its impacts on infiltration and runoff. Preliminary results suggest that reduced snowpack and frost formation will lead to a significant reduction in surface runoff and a commensurate increase in groundwater recharge. This could have profound impacts on the hydrology and ecology of the region, increasing baseflows, decreasing the variability of streamflows, and raising groundwater levels. Understanding these impacts will be We intend to apply our modeled outputs to the statistics defined in the Indicators of Hydrologic Alteration package developed by the Nature Conservancy as a way to quantify the impacts of air temperature changes on hydrology in the region. As we move forward we will be looking for tipping points and threshold behavior that can help scientists understand the changing system and help guide conservation and development planning.