Causes of Historical Changes in Groundwater Recharge Rates in Southeastern Wisconsin

BACKGROUND/NEED
Recharge is the process by which rain, snowmelt and surface waters infiltrate to and replenish groundwater. As such, it is the ultimate source of all of our groundwater resources. Yet it is also very difficult to measure, because of its diffuseness. Information on the rates of recharge is usually sparse. To date there has been very little examination of how recharge rates vary through time in response to climatic or land-use changes, making long-term planning difficult for groundwater-dependent communities.

The spatial distribution of recharge in SE Wisconsin was examined during a previous Groundwater Research Program project, showing that it can be quantitatively linked to a number of topographic, hydrogeologic and land-use properties. That work has successfully provided recharge influxes for regional groundwater flow models of southeastern Wisconsin and Fond du Lac County. It has assumed, however, that the recharge rates are static, which they clearly are not. As areas undergo droughts or extended wet periods, recharge undoubtedly varies. As regional or global climate changes, so too will recharge. The question is, how much?

OBJECTIVES
The purpose of this work was to define how recharge rates change through time in response to precipitation changes, to ascertain what factors control that response, and then to develop a mechanism for predicting future recharge changes.