LINKING HYDROGEOLOGY AND ECOLOGY USING REFERENCE SPRINGS IN WISCONSIN

The Wisconsin Geological and Natural History Survey is monitoring eight reference springs that are representative of classes of rheocrene springs identified during a recently-completed statewide inventory of springs. In stream ecology studies, reference sites are commonly used to establish benchmark conditions for a stream within a particular region. Similarly, the reference springs are being used to characterize seasonal variability in discharge, water chemistry, and temperature, and to describe spring vegetation and macroinvertebrate communities. The springs discharge at rates of approximately 1 to 4 ft³/second. All of the springs flow perennially, but they lack distinct storm-related or seasonal variations in discharge. Concentrations of major ions in spring waters were nearly constant over the three-year monitoring period, suggesting mixing along groundwater flow paths within spring catchments. Several springs exhibit variations in water temperature that lag behind seasonal changes in atmospheric temperature. The springs discharging from sandstone and carbonate bedrock aquifers have more stable temperatures than springs discharging from shallow sand and gravel aquifers. Vegetation surveys for four of the reference springs were completed in July 2018. Using the Wisconsin Floristic Quality Assessment (WFQA) Methodology, the results are being used to calculate species richness and WFQA metrics for each site. Macroinvertebrate samples collected in June 2018 at all eight sites are being analyzed using multivariate statistics to distinguish what geomorphological and chemical factors most influence macroinvertebrate assemblages in Wisconsin springs.