ELECTRICAL RESISTIVITY TOMOGRAPHY (ERT) APPLIED TO AN INVESTIGATION OF RIDGETOP WETLAND HYDROGEOLOGY IN THE DANIEL BOONE NATIONAL FOREST, ROWAN COUNTY, KENTUCKY

At least 30 ridgetop perched aquifer-wetland systems have been identified in the Daniel Boone National Forest in Eastern Kentucky. These wetlands are critical for a variety of ecological concerns: they are the breeding ground for very selective species of frogs and salamanders and the home to specific species of trees that may not be indigenous to other types of wetlands. Previous investigations at Eastern Kentucky University have been able to determine a general pattern in the stratigraphy and hydraulic conductivity of the area through a variety of methods. However, the subsurface controls of groundwater flow of these systems is difficult to constrain due to variable bedrock topography and clay layer geometries. In order to constrain how perched groundwater is stored on ridgetops and flows to lowlands and nearby wetlands, geophysical methods such as Electrical Resistivity Tomography (ERT) offer a low impact tool to investigate groundwater flow controls. This study focuses on one well-characterized wetland near Morehead in Rowan County, Kentucky, where core samples have been taken and logged and water table levels have been well monitored. An ERT survey of this wetland and its catchment basin was conducted under aquifer-saturated conditions in February 2020. Using ERT, the resistivities gathered helped to identify what layers were present when paired with cores of the wetlands to determine stratigraphic layers, shapes, and thickness of them. Our goals are to determine how bedrock topography, clay bed geometry, and fractures affect subsurface drainage and to determine the volume of aquifer storage. We anticipate mapping the geometry of an irregularly shaped aquifer as it connects to a wetland and flows as directed by subsurface controls.