Forecasting Impacts of Extreme Precipitation Events on Wisconsin’s Groundwater Levels

This proposed project will evaluate the potential for groundwater inundation of low-lying areas under climate patterns forecast for late in this century, providing a direct assessment of climate variability and resulting groundwater levels. Changes in climate, including the frequency and magnitude of precipitation events, will require changes to emergency response systems, infrastructure design, building standards, and land uses. The mid-western U.S. recently experienced record rain and snowfalls. In Spring Green, Wisconsin, the 4,378 acres flooded were several kilometers away from the flood plain of the Wisconsin River, outside of areas currently designated as floodplain by the Federal Emergency Management Agency. Modeling and field investigation indicate that flooding was caused by water table rise above ground surface. This proof of concept project includes application of climate and hydrologic models to this temperate region. Output from regional scale (50 kilometer resolution) climate forecasts developed by the North American Regional Climate Change Assessment Program (NARCCAP) will be used to develop scenarios of infiltration using a grid-based soil water balance model (SWB). Simulation of recharge to the groundwater system and resulting change in water table elevation will include consideration of vadose zone processes through application of the Unsaturated-Zone Flow (UZF) Package (Niswonger et al. 2006) to an existing transient, three dimensional MODFLOW (Harbaugh 2005) model of the study area. Ultimately, applying this series of models to a field site will test the utility of the NARCCAP projections in assessing future groundwater recharge patterns, and test the vulnerability of the selected landscape to recurring episodes of groundwater inundation. The modeling approach is supplemented with a modest field investigation to determine the suitability of the existing hydrogeologic conceptual model to the study area. Several communities in temperate climates currently have a need for this type of hydrologic forecasting.