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Ground-water recharge rates--A land-use planning tool for the Piedmont
Conference Proceedings
By Doug A. Harned and Charles C. Daniel, Jr.
Abstract
The number of ground-water users in the Piedmont continues to increase with suburban development that is not tied to available surface-water supplies. To determine the maximum population that can be supplied by ground water, planners must know the amount of ground water that can be withdrawn without exceeding recharge and(or) overdrafting ground water in long-term storage.
In response to requests from county officials for information about ground-water resources in the fractured-rock aquifer system, the USGS conducted studies from 1995 to 1997 to estimate ground-water recharge rates in Guilford and Orange Counties in the central Piedmont of North Carolina. Ground-water flow in streams was estimated by using hydrograph separation and long-term USGS records from 33 gaging stations with drainage areas that range in size from 7.54 to 1,310 square miles. The local minimum method of hydrograph separation by Pettyjohn and Henning (1979) was used to estimate values of daily mean ground-water discharge. Assuming that there has been no long-term change in ground-water storage, ground-water discharge is equal to ground-water recharge. Recharge hydrographs and duration tables were generated for each basin and subbasin within the counties.
The median ground-water recharge for 27 basins and subbasins within Guilford and Orange Counties ranges from 80.7 to 723 gallons per day per acre. The difference in recharge rates generally correlates with hydrogeologic units of the region. The recharge values combined with knowledge about other factors that affect recharge rates, such as land use and slope, can be used by planners to estimate the size of a recharge area needed to meet a water demand. These methods have been used by Guilford County planners to identify lot sizes needed to sustain ground-water supplies for individual homes.
Citation:
Harned, D.A., and Daniel, C.C., Jr., 1999, Ground-water recharge rates-- A land-use planning tool for the Piedmont [abs.],
in Proceedings of the 48th Annual Meeting of The Geological Society of America Southeastern Section, March 25-26, 1999: Athens, GA, 1999 Abstracts with Programs, v. 31, no. 3, p. A-19.
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Available from The Geological Society of America, Inc., 3300 Penrose Place, Boulder, Colo. 80301-9140; abstract in the proceedings of the 48th Annual Meeting of The Geological Society of America, Southeastern Section, March 25-26, 1999, v. 31, no. 3, 1 p. |
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