Quantitative groundwater tracing and effective numerical modeling in karst: an example from the Woodville Karst Plain of North Florida

摘要

Quantitative groundwater tracing is being used in the Woodville Karst Plain (WKP) of North Florida to characterize the hydraulic complexities of conduit flow for numerical modeling purposes. Accordingly, seven tracer tests were performed along both mapped and unmapped pathways ranging from 2.5 to 19.5 km in length utilizing between 0.7 and 4.5 kg of fluorescent tracer. Tracer recovery curves were measured at one or more points along a flow path for each tracer test. Computed mean velocities through the conduits ranged from 500 to 4560 m/day with peak concentrations between 0.12 and 125 ppb. The data obtained from the tracer tests have been incorporated into a finite element numerical model of groundwater flow in the WKP. Through-conduit velocities and mapped flow paths identified by the first five tracer tests were used in conjunction with cave map data to build discrete conduit pathways into the model framework and set flow parameters within the numerical conduits. Particle tracks generated from the resulting model were then used to highlight flow paths associated with a sinking stream that was the focus of the last two tracer tests. Subsequent tracer test results closely confirmed the model predictions. Current model results indicate that this approach will provide an effective method of realistically simulating spring flows and delineating individual springsheds within the karst basin.