T8 Impacts of Land Use and Climate Change on Water Resources Sustainability I

Sunday, 31 October 2010
8:00 AM - 12:00 PM
Mile High Ballroom 1AB

EVALUATING THE EFFECTS OF CLIMATE CHANGE on GROUNDWATER RECHARGE IN SOUTHWEST WISCONSIN

Paper number: T8-4
Program: Technical Sessions
Time: 8:40 AM – 8:55 AM

Authors

Abstract

Record precipitation in 2007 and 2008 contributed to widespread groundwater flooding near Spring Green, WI, and caused over $17 million in economic losses. Local citizens and government agencies, concerned that climate change could increase groundwater recharge and the frequency of such flooding are investing over $8.5 million to mitigate high water table conditions. To help them plan for long term changes, we combined future climate models with a soil water balance model and groundwater flow model to evaluate expected changes to recharge and the water table elevation through the year 2100. Eight statistically-downscaled global circulation models (GCMs) for the future periods of 2046-2065 and 2081-2100 provide precipitation, temperature, and relative humidity for a soil water balance model that produces spatially and temporally variable simulations of recharge. Recharge is then applied to a transient groundwater flow model of the region to simulate the water table. Model simulations of 1981-2000 provide a base case for comparison.

Under the base case, annual recharge averages 35.8 cm across the model domain. Despite a predicted increase in precipitation of 5.8 cm by 2100, simulated average annual groundwater recharge decreases 1.5 cm by 2065 and decreases an additional 3.8 cm by 2100. Increasing annual temperatures increases evapotranspiration (calculated by a Thornthwaite-Mather method), driving the decrease in recharge. However, the range in predicted recharge is large. The GCM producing the highest recharge (CCCMA) predicts no appreciable change to recharge by 2100, while the lowest recharge model (MIROC32) results in a decrease of over 19 cm per year. The frequency distribution of annual recharge simulated by the soil water balance model becomes more positively skewed during both future periods, suggesting years of high groundwater levels may indeed become more common despite lower recharge on average. These results suggest that preserving current land use in Spring Green (row crops, and commercial and residential developments) may require implementation of the proposed engineering solutions to enhance groundwater discharge during periods of high recharge.