GEOCHEMICAL PROPERTIES OF SEEPAGE-FILTRATION AND FRACTURE SPRINGS IN WISCONSIN

The spatial distribution of temperature differs between many seepage-filtration and fracture springs. In this study, we explore if there are also differences in the spatial distribution of geochemical properties between these two spring orifice geometries. To do this, we studied six springs in Wisconsin, three seepage-filtration and three fracture springs. Spring water geochemistry is important because it influences spring habitat. It is also useful in understanding groundwater residence times and aquifer materials.

At each spring orifice, sampling points were set and mapped at 30 cm intervals. Water samples were collected and analyzed for chloride and nitrate using ion-specific electrodes. A sonde was also used to analyze water pH, conductivity, and temperature at each interval. A single water sample was collected near the spring orifice and sent to the UW-Stevens Point Water and Environmental Analysis Lab for analysis of major cations and anions. A FLIR Vue pro camera captured thermal images at the same location.

Summary statistics show that seepage-filtration springs generally have more variation in the geochemical properties measured. On the other hand, fracture springs show less variation in the measurements of each geochemical property. Additionally, GIS maps created using the Inverse Distance Weighted method show that seepage-filtration springs have a greater spatial variation in geochemistry than fracture springs.

The research shows that springs with more variable distribution of temperature, like seepage-filtration springs, may also have more variation in geochemical properties. Some possible explanations include differences in mineral solubility at different temperatures. Alternatively, the time that the water spends in the spring pool is very different between seepage-filtration and fracture springs. Fracture springs with less variation may be better indicators of groundwater conditions.