APPLICATION OF ELECTRICAL RESISTIVITY TOMOGRAPHY (ERT) TO WETLAND HYDROGEOLOGY: AN ASSESSMENT OF THE EFFICACY OF ARRAY CONFIGURATIONS

Electrical Resistivity Tomography (ERT) is a geophysical technique used to measure and map the resistivity of the subsurface. Resistivity (expressed as Ohm-meters) is the inverse of conductivity, and is an intrinsic property of earth materials. ERT is frequently used for mineral and groundwater exploration, but this technique can be used in any field in which the user requires information on both the horizontal and vertical subsurface. Resistivity is determined by applying a known current on one electrode pair (A and B) and taking measurements of voltage potential on another electrode pair (M and N), later creating a pseudosection from the data collected. There are many different electrode configurations that can be used; for groundwater studies the two most commonly used are the Schlumberger array and the Dipole-Dipole array. The Schlumberger array is the best method for vertical electrical sounding (VES) of groundwater, but the Dipole-Dipole array is capable of higher resolution imaging. In this study, we compare the efficacy of these two array configurations to determine which one is best suited to help us understand the hydrogeology of geographically isolated wetlands (GIWs) in the Daniel Boone National Forest in eastern Kentucky. These GIWs provide numerous benefits to the surrounding area, such as water quality improvement, sediment and carbon retention, and flood protection. We conclude that the Schlumberger array provides the most accurate results and highest agreement with core data; results from the dipole-dipole array are too noisy to be of practical use.