USING GEOPHYSICAL METHODS TO IDENTIFY SUBSURFACE WATER STORAGE AND DRAINAGE PATTERNS IN KARST TERRAIN

The horizontally interbedded limestones and shales in Northern Kentucky harness the potential to support perched aquifers in the subsurface. This subsurface groundwater-saturation can cause seepage springs to develop on the surface. This seepage is evidenced by the development of marshes, lakes and ponds during the wet seasons. Also, anastomosing limestone has been found as float on the hill. Together, the anastomosing limestone can create a competent reservoir for these perched aquifers and the seepages could be coming from these reservoirs. Using electrical resistivity (ER), the degree of this subsurface groundwater saturation can be measured and modeled. A survey was conducted on a farm in Dry Ridge, Kentucky where a spring was known to exist. An ER survey can identify these perched aquifers by modeling the groundwater through dissolved ions trapped in the groundwater.

The seepage spring on the farm was dug out by recent farm owners for irrigation and livestock watering, leaving behind a small structure that allows a small volume of water to flow from a hill on the property. A set of two ER surveys was conducted above this spring with ER races running perpendicular to where the spring flowed from the hill. The goal of these surveys was to produce a 2D cross-section of the hill and to measure the degree of groundwater saturation in the area directly beneath and above the spring. This was done to measure the drainage area feeding the spring and locate other possible reservoirs of groundwater in the hill. Modeled cross sections of the subsurface geology depict a high degree of saturation in the hill at 23.8ft and 47.5ft deep, suggesting that multiple zones of saturation at varying depths exist. With the knowledge of an existing spring, it is possible to create another spring in the area, allowing water from this groundwater-saturated hill to be acquired. This project serves as an analogue for acquiring groundwater in the surrounding area and the preliminary data will be used in the future to locate other perched aquifers.