USING TIME DOMAIN REFLECTOMETRY AND 2-D DIFFERENTIAL ERT TO MONITOR CHANGES IN SOIL MOISTURE IN MANTLED AGRICULTURAL SINKHOLES

We are utilizing a combination of Time Domain Reflectometry (TDR) and 2-D Differential Electrical Resistivity Tomography (ERT) to monitor spatial and temporal changes in soil moisture within agricultural sinkholes. Preliminary results from a field site in southwestern Virginia show that 2-D Differential ERT is capable of modeling changes resulting from infiltration after a storm event. TDR profiles in sinkholes show heterogeneity in soil moisture to depths of 7.5m, and also capture wetting and drying variations related to infiltration and later drainage after rain events. Coupling TDR with 2-D Differential ERT is allowing us to test for correlations between soil moisture variations and Differential ERT changes. If these two changes can be correlated over time, this will allow variations in soil moisture to be extrapolated over much larger areas in both 2-D and 3-D.

Because soil moisture is an important modeling parameter in vadose hydrology, this technique is a promising new method for obtaining spatially comprehensive data in 2-D, 3-D, and at depths greater than what has traditionally been available. If successful, the data collected using this technique can be used to create conceptual and numerical models of hydrology in thickly mantled sinkholes.