Climate change, frost, and groundwater recharge in the Midwestern U.S.

The one-dimensional Simultaneous Heat and Water (SHAW) model was used to simulate two continuous 29-year periods representing historical (1970-1999) and future (2040-2069) climate conditions in southern Wisconsin, based on downscaled GCM data from the North American Regional Climate Change Assessment Program (NARCCAP).

Modeling showed that warmer winter and spring temperatures lead to a decrease in runoff and a commensurate increase in recharge. Additional modeling with the frost portion of the model disabled confirmed the importance of soil frost formation to the results. These results held across different climate models and a wide range of soil types.

Groundwater and stream baseflows are critical to many water resource issues (e.g., water supply, wastewater discharge permitting,  fisheries, groundwater flooding). In the midwestern U.S. one of the likeliest impacts of climate change will be increases in groundwater recharge, resulting from both increases in dormant-season precipitation and decreases in snow and soil frost. This research provides quantitative information on these issues.