MONITORING DISCHARGE, WATER QUALITY, AND HYDROGRAPH RESPONSE TIME OF A LARGE KARST SPRING IN MIDDLE TENNESSEE

Despite being one of the largest springs in Tennessee, the Boils spring on the Roaring River (546 km²) has never been monitored for flow or water quality. The Boils is a karst spring that has been connected to in-stream swallets on Spring Creek by dye tracing, a straight-line distance of approximately 10 km. We established a stream gage at the Boils and developed a discharge rating curve based on flow data collected at the spring from 2014 to the present. Over that same time period, we have continuously monitored stage, temperature, and conductivity at the Boils using automated loggers. Suspended sediment concentrations were also measured by taking water samples at regular intervals. Flow at the Boils spring was measured using a Marsh-McBirney current meter using the 0.6-depth velocity method. Over the study period, from 2014 to the present, the following averages (and ranges) were determined from monitoring: average discharge = 3.0 m³/sec (range = 0.8 to 5.0 m³/sec), average specific conductance = 298 μS/cm (range = 254 to 307 μS/cm), and average temperature = 15.1°C (range = 6.9 to 23.0°C). For storm events, the lag time between basin rainfall and spring peak discharge ranged from 4 to 12 hours depending on antecedent moisture conditions. Suspended sediment from the spring was very low with values ranging from 4 to 32 ppm. This research provides the first baseline data for one of the largest springs in Tennessee.