Ohio's potentiometric surface mapping program began in the late 1990's under the direction of the Ohio Department of Natural Resources Division of Water. This program was initiated by the Ohio EPA for use in their Source Water Assessment Program
Potentiometric surface maps indicate the elevation and horizontal direction of ground water flow. Potentiometric surface maps are being created for bedrock (consolidated formations) and sand & gravel (unconsolidated formations) aquifers.
County based maps are available as PDF files and as GIS ArcView Shape files.