Ground-water resources of the lower Apalachicola-Chattahoochee-Flint river basin in parts of Alabama, Florida, and Georgia; SUBAREA 4 of the Apalachicola-Chattahoochee-Flint and Alabama-Coosa-Tallapoosa river basins
Open-File Report 95-321
- Lynn J. Torak and Robin John McDowell
The study area is underlain by Coastal Plain sediments of pre-Cretaceous to Quaternary age consisting of alternating units of sand, clay, sandstone, dolomite, and limestone that gradually thicken and dip gently to the southeast. The Upper Floridan aquifer is composed of an offlapping sequence of clastic and carbonate sediments consisting of the Clinchfield Sand, the Ocala, Suwannee, and Tampa Limestones, and the Marianna Formation. The Intermediate system consists of the Intracoastal, Chipola, and Jackson Bluff Formations, is limited in areal extent to the southern part of the basin in Florida, and constitutes an aquifer of low yield. The aquifer-stream-reservoir (flow) system is defined by surface water in hydraulic connection with aquifers and semiconfining units.
Simulation of the flow system by using the U.S. Geological Survey’s MODular FiniteElement model (MODFE) of two-dimensional ground-water flow indicated that ground-water availability in Alabama is affected most by changes to lateral and vertical boundary conditions to the Upper Floridan aquifer that might occur in that state, and is affected minimally by changes to ground- and surface-water levels in Georgia. Incomplete hydrologic information precludes definitive assessment of groundwater-resource potential, overpumpage, and potential for additional development; however, simulated-increased pumpage at more than 3 times the October 1986 rates caused drying of the Upper Floridan aquifer in parts of Miller and Lee Counties, Ga. Evaluation of groundwater-development potential in the virtually untapped Intermediate system has questionable reliability due to the lack of data.
Increased hypothetical pumpage over October 1986 rates for the Upper Floridan aquifer, located almost entirely in Georgia, indicated reduction in ground-water discharge to streams that reduced flow in the Apalachicola River and to the Bay, especially during droughts. Water budgets prepared from simulation results indicate that discharge to streams and recharge by horizontal and vertical flow are principal hydrologic mechanisms for moving water into, out of, or through aquifers. The Intermediate system contributes less than 2 percent of the total simulated ground-water discharge to streams; thus, it does not represent an important source of water for the Apalachicola River and Bay.
Additional publication details
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- USGS Numbered Series
- Ground-water resources of the lower Apalachicola-Chattahoochee-Flint river basin in parts of Alabama, Florida, and Georgia; SUBAREA 4 of the Apalachicola-Chattahoochee-Flint and Alabama-Coosa-Tallapoosa river basins
- Series title:
- Open-File Report
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- Year Published:
- U.S. Geological Survey
- Contributing office(s):
- South Atlantic Water Science Center
- Report: ix, 145 p.: 11 Plates: 20.29 x 30.44 inches or smaller
- United States
- Alabama, Florida, Georgia
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