Present ground-water use in Ohio, approximately 650mgd (million gallons per day) amounts to about 5 percent of the water that enters the ground-water reservoirs. The largest ground-water supplies are developed where natural concentrations of water occur, chiefly in the watercourse aquifers, which consist of sand and gravel of glacial origin (outwash) in the valleys of the major streams. Other important aquifers are glacial outwash in upland areas and in the buried Teays Valley system, the limestone and dolomite aquifers in western Ohio, and sandstone and shale aquifers in the eastern half of the State.

Future outlook is that more of the increasing water demand will be met from ground-water sources. Ground-water supplies will be developed at many new sites, and aquifers in areas already heavily pumped will be made to yield more water by the drilling of additional wells and recharging the aquifers artificially. Large quantities of ground water in storage, virtually unexploited, could be used for temporary low-flow augmentation of streams. Management of ground-water resources will be needed to help solve supply and distribution problems, and to resolve conflicts between users. Among future problems will be those arising from underground disposal of wastes, a practice which is expected to grow substantially from enforcement of water-quality standards for streams, set under the Federal Water Quality Act of 1965.