POTENTIAL IMPACTS OF CLIMATE CHANGE ON GROUNDWATER DISCHARGE TO STREAMS, CHEQUAMEGON-NICOLET NATIONAL FOREST, WISCONSIN

The Chequamegon-Nicolet National Forest (CNNF), a mixed-use forest in northern Wisconsin, is one of the pilot forests in the US Forest Service’s Watershed Vulnerability Assessment Project. The project, comprising eleven forests across the US, is aimed at quantifying the effects of climate change on watersheds so that the results can be used to inform management decision making. As part of this Watershed Vulnerability Assessment Project, researchers from the Wisconsin Geological and Natural History Survey, the USGS-Wisconsin Water Science Center and the University of Wisconsin-Madison are investigating the effects of climate change on groundwater resources in the CNNF.

Of particular interest to forest managers is how climate changes might affect stream baseflows. Many of the streams in the forest gain significant amounts of flow from groundwater discharge, which provides a persistent source of cold water, a necessity for trout and other aquatic species. Identifying the groundwater contributing areas for these streams helps assess the potential impacts to the streams from alternative land management decisions. We used a newly developed groundwater flow model to delineate capture zones for specific stream segments in the National Forest. Based on climate model outputs and Soil-Water Balance model estimates of potential changes in recharge, we used the groundwater flow model to understand how climate change might alter average groundwater capture zones for different stream segments over the long-term, as well as to identify the maximum extent of capture zones during the year. The groundwater flow model is also used heuristically to understand how baseflow in these streams will respond to worst-case drought scenarios.