Delineation of a Major Karst Basin with Multiple Input Points, Roaring River, Tennessee

Abstract

Karst aquifers that are dominated by conduit recharge are at high risk of contamination because there is little filtration or sorption of contaminants in the water. Identifying flow paths through conduit aquifers is required in order to delineate basin boundaries and potential areas at risk from groundwater contamination. In this study we report on the first continuous (similar to 1 year) discharge and water quality data set ever collected from the Boils spring on the Highland Rim of middle Tennessee. The Boils drains the Roaring River-Spring Creek system, a State Scenic River and Wildlife Management Area. We also report on the results of a quantitative dye trace that was done to identify surface contributions to this spring. At the Boils, we measured discharge, temperature, and specific conductance for an approximate one-year period. The average annual discharge of the Boils during 2015 was 2.1 m(3)/s, with storm discharge reaching as much as 14 m(3)/s. Conductivity at the Boils spring ranged from 310 mu S at baseflow to 290 mu S during storm events. Water temperature of the spring varied seasonally from 9 to 22 degrees C. The dye trace revealed a direct connection to the Boils from a sink located 9 km away (straight-line distance), with a travel time of about 12 h. A second trace at another sink covered a straight-line distance of 1.5 km in 4 h. The rapid travel times suggest that this aquifer is dominated by conduit flow and that further research to sample water quality is warranted. Our data help to fill an important gap in data about major spring discharge and water quality in Tennessee.