Ground water in the Ohio Region is a large, important, and manageable resource that should have a significant role in regional water development.

On the basis of a comparison of ground-water withdrawals with estimated ground-water recharge, it appears that the ground-water resources of the Ohio Region probably will not be used at full potential under existing development plans. Annual ground-water use (1960) by municipalities and rural residents was about 1,000 million gallons per day. Average annual regional ground-water recharge is about 35,000 million gallons per day. Therefore, base-year (1960) municipal and rural ground-water use is only about 3 percent of recharge. Annual regionwide ground-water use (1965) by industry also is only about 3 percent of recharge.

Not all ground water in storage is recoverable for development, but estimates of the amounts that can be obtained from storage, under specified conditions, are calculated to show the magnitude of water that is available. Total potable ground water available from storage in the outwash and alluvial aquifers in the Ohio River valley and the subbasins is about 23,000 billion gallons. This about four times the floodcontrol storage of all Ohio Region Corps of Engineers reservoirs constructed, under construction, or in advance planning as of July 1965. Approximately 85,000 billion gallons of potable ground water is available from storage in the region in aquifers other than the outwash and alluvial aquifers. This is about 20 percent of estimated storage in Lake Ontario.

About 5 percent of the region has ground-water resources capable of supplying more than local needs. For example, under certain specified conditions the excess of ground-water recharge over base-year (1960) ground-water use is available for 22 million additional people in the Wabash subbasin; for 4, 1.5, and 12 million additional people, respectively, in the Miami, lower Scioto, and Allegheny subbasins; for 5 million additional people in the Ohio River valley; or for equivalent quantities of water supply for industrial or a~ricultural expansion or other use. A reasonable assumption is that much of the available ground water in these areas can be pumped and transported to reasonably distant points of need.

The Wabash and White subbasins probably have the highest potential of all Ohio River subbasins for additional ground-water development. About 30,000 billion gallons, or about 28 percent of the total potable ground water available from storage in the Ohio Region, is in storage in these subbasins. Estimated average annual ground-water recharge in the Wabash and White subbasins is 7,300 million gallons per day. Annual ground-water use (1960) by municipalities and rural residents of the subbasins of about 220 million gallons per day is only about 3 percent of estimated annual ground-water recharge and only about 0.3 percent of the potable ground water in storage in the subbasins. Also, many high-yield aquifers are present and offer excellent reservoir-manipulation possibilities in conjunction with existing and planned surface reservoirs.

Practically all areas of high population density in the Ohio Region have the potential for development of ground-water resources. The Indianapolis, Ind., area probably has the highest potential.

Assuming that future population growth will be heaviest in the areas paralleling the interstate highway system, much of the increased water demand associated with these growth areas can be supplied by ground water. The areas of population growth in Indiana and southwestern and south-central Ohio are especially well situated in terms of potential ground-water supplies.

Underground space in the Ohio Region, consisting of natural pore spaces and fractures in rocks and sediments, can be considered a regional resource in the sense that it can be included in regional water-pollution control or waste-disposal plans. Much of this space is already occupied by ground water or other fluids which must be displaced for any alternate use. There is a potential for underground waste storage in practically the entire Ohio Region.

Rapid advance of techniques in ground-water hydrology during recent years has provided methods which the hydrologist can use for evaluating planned ground-water development. Therefore, the manager can resolve the inherent problems that historically have bred caution when this part of our total water resource was considered for development.