Spring Characterization Methods & Springshed Mapping

Abstract

Southeastern Minnesota's karst lands support numerous trout streams created by coldwater springs emanating from Paleozoic bedrock. While trout streams have been traditionally managed as surface water resources they are fundamentally supported by clear, relatively constant temperature groundwater. In karst areas this groundwater resource is as vulnerable as surface waters to human activities. Designing Best Management Practices (BMPs) to protect groundwater fed springs should improve the overall protection of Minnesota's trout streams. Dye tracing has been the tool of choice for mapping the recharge area or groundwater basin that feed a particular spring. These karst groundwater basins have been termed "springsheds". In order to accelerate springshed mapping, a two~year study was funded by the Minnesota Environment and Natural Resources Trust Fund as recommended by the Legislative-Citizen Commission on Minnesota Resources (LCCMR). To improve the effectiveness of dye tracing we are applying a variety of new tools to increase our knowledge of the underlying karst systems. Techniques being investigated include temperature and discharge monitoring, detailed structural mapping of the aquifers, unit hydrographs, chemical and isotopic studies. These new methods to define the size and geometry of springsheds can be tested against basins previously defined by dye tracing. In previously untraced basins these predictive tools can be used to design more efficient tracing programs. The following paper demonstrates the application of structural mapping to dye tracing.