STATEWIDE, SEAMLESS MAPPING OF GROUNDWATER VULNERABILITY AND HYDROGEOLOGIC SETTING IN OHIO

The sustainable management of Ohio’s groundwater resources requires policies founded on reliable, readily available scientific data. As population and public understanding of groundwater as a precious resource expand, city planners, county commissioners, and water utility managers must increasingly address issues of groundwater protection in ways that promote both industrial development and public health. Critical to such efforts are accurate, data-driven assessments of groundwater vulnerability. Groundwater’s vulnerability to contamination is a key factor in many environmental permitting processes and an important consideration in the siting of new developments, industrial centers, and production wells. Understanding its degree and spatial distribution is therefore a crucial step in protecting the integrity of the state’s groundwater resources.

Groundwater Vulnerability (GV) mapping is the process of evaluating an area’s vulnerability to groundwater contamination based upon its hydrogeologic, topographic, and soil media characteristics. GV maps consider the case in which a contaminant is introduced at the land surface and allowed to percolate into the aquifer, be attenuated by natural processes, or be transported out of the area. As the hydrogeologic parameters controlling the fate of the contaminant change, the likelihood of the aquifer’s contamination increases or decreases. In 2019, the Ohio Department of Natural Resources Division of Geological Survey began the process of remapping its existing “Pollution Potential” maps into a new statewide, seamless GV coverage using a highly modified DRASTIC model. Survey geologists standardized mapping methodology; aquifer, vadose zone, and soil media classifications; ratings ranges; and hydrogeologic settings; removing, modifying, or adding values using new data and a more developed understanding of Ohio’s diverse hydrogeology.

In addition to its digital datasets, this project produced two 1:500,000-scale wall maps. The Groundwater Vulnerability Index Map of Ohio visualizes the GV index (relative vulnerability to contamination) of Ohio’s groundwater and the Hydrogeologic Settings of Ohio map depicts the extent and characteristics of the state’s forty unique hydrogeologic settings.