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Ground-water component of Piedmont streams: Implications for ground-water supply systems and land-use planning

Geological Society of America Abstracts with Programs
By Douglas A.Harned and Charles C. Daniel, III

Abstract

The two components of streamflow--ground-water discharge and overland runoff--can be estimated graphically for a given stream. Additionally, if it is assumed that there is no long-term change in ground-water storage, ground-water discharge is equal to the ground-water recharge.

The stream basins examined are scattered across the North Carolina Piedmont and range in size from about 15 to 1700 square miles. The average amount of ground-water discharge for 10 Piedmont streams is 44 percent of the total runoff (range = 65-32 percent). The rates of ground-water discharge vary with long- and short-term regional rainfall, and with seasonal evapotranspiration rates. During the low evapo- transpiration months of December through March there is approximately 80 percent more ground-water discharge than during the peak growing season months of May to August.

Knowledge of ground water recharge rates aids decision making regarding ground-water supply systems and land-use planning. The fluctuation in annual and seasonal rates of ground-water recharge has ramifications for the long-term production of ground water at the maximum possible sustained yields. Increases in ground-water pumpage which may result in reductions in streamflow are of concern in determining in-streamflow needs.

Protection of ground-water recharge areas from the encroachment of high density impervious cover is a goal in planning surface- and ground- water development. Guidelines to land-use planners can be provided by definition of recharge rates. The amount of land area needed for recharge necessary to adequately sustain ground-water supply for land development can be estimated using the calculated recharge rates. For example, the average daily household water demand for development in a basin near Greensboro, N.C. would require lot sizes of one acre or more to insure long-term sustained yield.

Harned, D.A., and Daniel, C.C., III, 1987, Ground-water component of Piedmont streams-Implications for ground-water supply systems and land-use planning [abs.]: Geological Society of America Abstracts with Programs, v. 19, no. 2, p. 89.