Georgia Geologic Survey Information Circular 74
During 1980, an estimated 121 million gallons of water per day was pumped in a 26-county area in east-central Georgia from sand aquifers of Paleocene and Late Cretaceous age. Maximum withdrawals were at the kaolin mining and processing centers in Twiggs, Wilkinson, and Washington Counties, where water levels have declined as much as 50 feet since 1944-50. In the southern two-thirds of the study area, water levels have shown little, if any, change. Declining water levels and increasing competition for ground water have caused concern over the adequacy of ground-water supplies. This report defines the areal extent and describes the hydrogeology of the Paleocene-Upper Cretaceous aquifers of east-central Georgia, and evaluates the effects of man on the ground-water flow system.
Hydrogeologic data from four test wells indicate that the aquifers consist of alternating layers of sand and clay that are largely of deltaic origin. The aquifers contain discontinuous confining units of clay and silt that are believed to extend for only short distances and are not significant in a regional evaluation. For this reason, the aquifers were grouped into two regional aquifer systems that are bounded by three regional confining units. The Dublin and Midville aquifer systems were each named for a geographic feature near a test well that penetrates sediments which are representative of the geologic and hydrologic characteristics of the aquifer system.
In the northern third of the study area, the confining unit between the Dublin and Midville aquifer systems is absent and the aquifer systems combine to form the Dublin-Midville aquifer system. The aquifer systems range in thickness from 80 to 645 feet and their transmissivities range from 800 to 39,000 feet squared per day. The hydraulic conductivity ranges from 15 to 530 feet per day. Wells yield as much as 3,400 gallons per minute. Chemical analyses of water from 49 wells indicate that water from both aquifer systems is of good quality except in the central part of the study area, where iron concentrations are as high as 6,700 micrograms per liter and exceed the 300 micrograms per liter recommended limit for drinking water.
The principal recharge to the aquifer systems is from precipitation that occurs within and adjacent to the outcrop areas. The principal discharge is to streams in the outcrop area, although in the southern part of the study area, discharge occurs by leakage into overlying units.
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