Georgia Water Science Center
This report is available online in pdf format (1 MB): USGS OFR 06-1148 (
)
Gregory S. Cherry
U.S. Geological Survey Open-File Report 2006-1148, 16 pages (Published 2006)
A regional MODFLOW ground-water flow model of
parts of coastal Georgia, Florida, and South Carolina was used
to evaluate the effects of current and hypothetical groundwater
withdrawal, and the relative effects of pumping in
specific areas on ground-water flow in the Upper Floridan
aquifer near Fort Stewart and Hunter Army Airfield (HAAF),
coastal Georgia. Simulation results for four steady-state
pumping scenarios were compared to each other and to a
Base Case condition. The Base Case represents year 2000
pumping rates throughout the model area, with the exception
that permitted annual average pumping rates for the year 2005
were used for 26 production wells at Fort Stewart and HAAF.
The four pumping scenarios focused on pumping increases
at HAAF resulting from projected future demands and additional
personnel stationed at the facility and on reductions in
pumping at Fort Stewart.
Scenarios A and B simulate 1- and 2-million-gallon-perday (Mgal/d) increases, respectively, at HAAF. Simulated water-level change maps for these scenarios indicate an area of influence that extends into parts of Bryan, Bulloch, Chatham, Effingham, and Liberty Counties, Ga., and Beaufort and Jasper Counties, S.C., with maximum drawdowns from 0.5 to 2 feet (ft) for scenario A and 1 to 4 ft for Scenario B.
For scenarios C and D, increases in pumping at HAAF were offset by decreases in pumping at Fort Stewart. Scenario C represents a 1-Mgal/d increase at HAAF and a 1-Mgal/d decrease at Fort Stewart; simulated water-level changes range from 0.4 to – 2 ft. Scenario D represents a 2-Mgal/d increase at HAAF and 2-Mgal/d decrease at Fort Stewart; simulated waterlevel changes range from 0.8 to – 4 ft. The simulated waterlevel changes indicate an area of influence that extends into parts of Bryan, Bulloch, Candler, Evans, Chatham, Effingham, Liberty, Long, McIntosh, and Tattnall, Counties, Ga., and Jasper and Beaufort Counties, S.C. In general, decreasing pumping at Fort Stewart by an equivalent amount to pumping increases at HAAF reduced the magnitude and extent of drawdown resulting from the additional pumping. None of the scenarios resulted in large changes in the configuration of the simulated potentiometric surface and related ground-water flow directions.
The scenarios simulated vary from the original model only by increasing pumpage less than 1 percent of the total calibrated model withdrawals. The changes in pumpage are located near the center of the original model area. Thus, the scenarios described in this report are considered to be reasonable with no less uncertainty than the original calibrated model.
Abstract
Introduction
Ground-Water Flow Model
Simulation of Ground-Water Pumping Scenarios
Model Limitations
References Cited
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