Evaluating Groundwater Availability in Support of Georgia's Comprehensive State-Wide Water Management Plan

Georgia’s landmark Comprehensive State-wide Water Management Plan employs advanced water supply planning concepts, including the use of water resource assessments to determine how much water can be consumed from the state’s major rivers, lakes, and aquifers without causing unacceptable impacts. To evaluate the state’s groundwater resources, aquifers were prioritized based on the functional characteristics of the aquifer, existing evidence of adverse affects due to withdrawals, and whether demand forecasts suggest significant increases in withdrawals placed on that aquifer in the years ahead. Three approaches, ranging from a simple water balance to the development and application of a numerical model with transient simulation capabilities, were used to quantify groundwater availability during dry years. Depending upon the available information for each representative aquifer, the most appropriate approach was then used to provide an initial estimate of the sustainable yield of the aquifer. In the regolith-fractured crystalline rock aquifers of the Piedmont and Blue Ridge physiographic provinces, water balances were constructed using available data characterizing both the natural and artificial movement of water. In the Valley and Ridge provinces of northwest Georgia, a more sophisticated water balance was constructed for confined and unconfined aquifers using simulated gradients and aquifer properties to estimate flow through the aquifer for comparison against pumping stress. In portions of Georgia’s Coastal Plain with sufficient hydrogeologic data, calibrated three-dimensional flow models were used to assess the impacts of pumping on heads and streamflow. The results of each assessment are being provided to Georgia’s ten Regional Water Planning Councils to assist in the determination of sustainable yields.