SPRINGSHEDS AND WATER QUALITY IN FORESTVILLE MYSTERY CAVE STATE PARK, MINNESOTA

Karst is an area that contains springsheds in which precipitation (recharging via sinkholes, stream sinks, and soils) enters a conduit system and emerges at a spring or set of springs. Mapping and identifying these springsheds is an ongoing process in Fillmore County, Minnesota. Field surveys, water chemistry and dye tracing were used to identify and classify springs in Forestville Mystery Cave State Park, Minnesota. Water chemistry was used to identify different springsheds. Multiple springs draining individual springsheds were detected. Initial high flow conditions allowed for ephemeral overflow springs to be identified. As the high flow conditions receded, the amount of total dissolved solids (TDS) gradually rose in the spring groups due to longer residence times in the conduit systems. Graphs of alkalinity, conductivity, and calcium plus magnesium versus time illustrate this. Dye tracing was used to map the springsheds and to verify that grouped springs drained specific springsheds.

Nitrate-nitrogen values in the springs ranged from 1.5 to 12.8 ppm. The low values were from forested springsheds. The high values were from springsheds dominated by row crop agriculture. These results confirm that agriculture is the major contributor to nitrate pollution of the area’s trout streams.