Water-Resources Investigations Report 96-4179
Ground-water discharge to streams was estimated in the central Savannah River basin near the U.S. Department of Energy, Savannah River Site, and adjacent parts of Georgia and South Carolina using hydrograph-separation techniques and a drought streamflow analysis. The estimated mean-annual ground- water discharge determined from the hydrograph-separation method indicates a greater ground-water contribution to streamflow for Upper Three Runs than for Butler, Brushy, or Brier Creeks. The unit-area mean-annual ground-water discharge ranges from 1.06 to 1.15 cubic feet per second per square mile for the Upper Three Runs basin; and from 0.39 to 0.69 cubic feet per second per square mile for the Butler, Brushy, and Brier Creek basins. The higher unit-area mean-annual discharges in the Upper Three Runs basin implies greater ground-water contribution from underlying Coastal Plain aquifers in that area.
A drought-period stream discharge analysis indicates that streamflow in the Upper Three Runs basin, S.C., receives a greater contribution of ground-water discharge from the intermediate ground-water flow system than the Georgia streams. During the 1986 drought, Butler, Brushy, and Brier Creeks had unit-area ground-water discharges that ranged from 0.004 to 0.16 cubic feet per second per square mile; and Upper Three Runs had unit-area ground-water discharges that ranged from 0.43 to 0.77 cubic feet per second per square mile. The drought stream discharge (estimated minimum ground-water discharge) was 16 to 23 percent of the estimated mean-annual ground-water discharge for the Brier Creek basin, and 41 to 67 percent for the Upper Three Runs basin.
Contribution of ground-water discharge to the tributaries is considered to be mainly from local and intermediate flow systems. The ground-water contribution from the local flow system in the Upper Three Runs basin ranged from 72 percent of the total ground-water discharge in the upper two-thirds of the basin to 100 percent in the lower part of the basin. Discharge from the local flow system in the Brier Creek basin ranged from 78 percent of the total ground-water discharge in the upper part of the basin to 95 percent of the total ground-water discharge in the central part of the basin.
First posted February 18, 2010
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