Hydrogeologic Assessment and Simulation of Stream-Aquifer Relations in the Lower Apalachicola-Chattahoochee-Flint River Basin

Cooperator: Georgia Department of Natural Resources, Environmental Protection Division
Year Started: 2000

Current levels of hydrologic information and results of digital ground-water-flow modeling in the lower Apalachicola-Chattahoochee-Flint River Basin are insufficient to describe effects of time-variant irrigation pumping on streamflow. Because of this, existing models cannot accurately predict ground-water or streamflow conditions during a growing season. The Georgia Department of Natural Resources is implementing a hydrologic assessment of the Upper Floridan aquifer in southwestern Georgia to obtain information on aquifer properties, pumping, ground- and surface-water levels, springflow, and streamflow.

As part of this assessment and to further understanding of stream-aquifer relations and the effects of groundwater pumping on streamflow in a karst hydrologic setting, the U.S. Geological Survey (USGS) has engaged in a cooperative effort to develop a ground-water-flow model that can account for stream-aquifer interaction, especially streamflow reduction due to agricultural pumping. Information obtained from the model is vital for the State's management of ground-water resources and for providing early indications of low-streamflow conditions that would affect delivery of water to downstream, out-of-state users.

Objectives

• Develop new data for the Upper Floridan and surficial aquifers through evaluation of well-drilling and aquifer-test information;
• Obtain accurate locations of pumped wells for municipal, industrial, and irrigation purposes;
• Collect and compile ground-water level, stream- seepage, and off-stream spring-discharge data; and
• Develop a transient finite-element model of groundwater flow that incorporates newly collected and existing hydrologic data, having ability to simulate seasonal ground-water levels, stream-aquifer interaction, and pumpage-induced streamflow reduction.

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