Improving the Prediction of Baseflows in the Driftless Area of the Upper Midwestern United States

Abstract:

The Driftless Area of the Upper Midwestern United States is a unique region that was not glaciated during the Quaternary Period. Groundwater discharges in the hilly landscape support over 4,000 miles of coldwater, high-class trout streams that are a destination for anglers across the Midwest. Temperature increases due to anthropogenic climate change are predicted to have a negative impact on the cold water thermal regimes that support species such as brook and brown trout. Previous work has concluded that the hillslopes in the region play an important role in producing the recharge that supports cool groundwater discharges concentrated in the headwaters of these streams.

In this study, we used a set of baseflow measurements recorded by Potter and Gaffield (2001) in the headwaters of a Driftless Area stream and a simple Geographic Information Systems (GIS) analysis to assess the relationship between the percentage of hillslope in a watershed and average unit baseflow. We found that there is a strong correlation between the hillslope percentage and the unit baseflow values from the Potter and Gaffield (2001) study. Further work is needed to verify the findings of this study and to assess the impacts of the underlying geological layers on the production of baseflow, but these results provide a first step in understanding the conditions that produce spatial variability in baseflow conditions in the Driftless Area. Agencies such as the Wisconsin Department of Natural Resources are beginning to plan for climate change adaptation in the region to protect the coldwater fisheries, so understanding the hydrology of headwater streams will be important in helping to identify areas with high, coldwater baseflow discharges that can provided refugia for coldwater species.