Projected and Realized Climate Change Impacts on Water Temperature in Wisconsin Trout Streams

Here we present stream temperature model projections and empirical monitoring data to show how climate change impacts may be realized in Wisconsin streams. We added a soil-water-balance model to an artificial neural network stream temperature model to generate daily time series estimates of potential groundwater recharge from precipitation, thereby linking precipitation to groundwater and stream temperature. The updated models highlight the relative resilience to climate impacts of Driftless Area streams, which are heavily influenced by inputs of cold groundwater, compared to streams in other areas of Wisconsin. We estimated changes in coldwater thermal habitat suitable for trout under the A1B emissions scenario using 10 global circulation models. Current climate conditions support 57% of stream kilometers across the state as thermally suitable for trout. By mid-century our models project a decrease to 47% (best-case) or 26% (worst-case). Following monitoring efforts that began in 2007 we have experienced significant flooding caused by multiple heavy precipitation events, drought, and wide ranges of air temperatures at various times of the year. We present empirical stream monitoring data to show how thermal refugia and trout populations may persist, albeit at reduced levels, under projected changes in Wisconsin’s climate.