Eastern Kentucky University
Application of Electrical Resistivity Tomography (ERT) to Wetland Hydrogeology: An assessment of the efficacy of array configurations
Grade Level at Time of Presentation
Junior
Major
Environmental and Applied Geology
Minor
Geography, GIS
KY House District #
81
KY Senate District #
34
Faculty Advisor/ Mentor
Dr. John White
Department
Department of Physics, Geosciences, and Astronomy
Abstract
Electrical Resistivity Tomography (ERT) is a geophysical technique used to measure and map the resistivity of the subsurface. Resistivity (expressed in units of Ohm-meters), the inverse of conductivity, is an intrinsic property of earth materials that is a function of their material composition, void space, and water content. ERT is frequently used for mineral and groundwater exploration, but this technique can be used for any study that requires information of the near-surface environment. Resistivity is determined by applying a known direct current on one electrode pair (labeled C1 and C2) and taking measurements of the voltage potential on another electrode pair (labeled P1 and P2), which is used to create a modeled pseudosection from the data collected. The two most commonly used electrode array configurations are Schlumberger and Dipole-Dipole. In this study, we test the efficacy of various array configurations to determine which one is best suited to help us understand the hydrogeology of geographically isolated wetlands (GIWs). GIWs are ecologically significant systems that provide numerous benefits to the surrounding area such as water storage, water quality improvement, sediment and carbon retention, and flood protection, to name a few. Using twenty-eight electrodes with varying spacing, we were able to conduct these two array configurations on the 977N (natural) wetland in the Daniel Boone National Forest, as well as on an oxbow bend in Taylor Fork Ecological Area. Our models suggest that the Schlumberger array provides the most accurate results. Results from the dipole-dipole array are noisy and provide a chaotic image of the subsurface whereas the Schlumberger modeled pseudosection strongly agrees with existing core data.
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 in units of Ohm-meters), the inverse of conductivity, is an intrinsic property of earth materials that is a function of their material composition, void space, and water content. ERT is frequently used for mineral and groundwater exploration, but this technique can be used for any study that requires information of the near-surface environment. Resistivity is determined by applying a known direct current on one electrode pair (labeled C1 and C2) and taking measurements of the voltage potential on another electrode pair (labeled P1 and P2), which is used to create a modeled pseudosection from the data collected. The two most commonly used electrode array configurations are Schlumberger and Dipole-Dipole. In this study, we test the efficacy of various array configurations to determine which one is best suited to help us understand the hydrogeology of geographically isolated wetlands (GIWs). GIWs are ecologically significant systems that provide numerous benefits to the surrounding area such as water storage, water quality improvement, sediment and carbon retention, and flood protection, to name a few. Using twenty-eight electrodes with varying spacing, we were able to conduct these two array configurations on the 977N (natural) wetland in the Daniel Boone National Forest, as well as on an oxbow bend in Taylor Fork Ecological Area. Our models suggest that the Schlumberger array provides the most accurate results. Results from the dipole-dipole array are noisy and provide a chaotic image of the subsurface whereas the Schlumberger modeled pseudosection strongly agrees with existing core data.