ASSESSING SUSTAINABLE YIELD OF AQUIFERS AS PART OF THE GEORGIA COMPREHENSIVE STATEWIDE WATER MANAGEMENT PLAN

Economic and population growth in Georgia exceed national averages. This is putting increased pressure on Georgia’s water resources, especially those of the metro Atlanta region. Georgia is nearing completion of a comprehensive statewide water management plan mandated by the Georgia General Assembly in 2004, and representing the largest environmental policy initiative in Georgia's history. A central part of the planning process is an assessment of existing groundwater resources in the principal aquifers of the state, and an estimate of sustainable yield. These prioritized aquifers include the Floridan, Claiborne, and Cretaceous aquifers of the Coastal Plain, the Paleozoic limestone aquifer in the Valley and Ridge Province in northwest Georgia, and the Crystalline Rock aquifer of the Piedmont and Blue Ridge provinces. Sustainable yields were determined using numerical models and water budgets that incorporated baseline municipal, industrial, and agricultural withdrawals from existing wells and hypothetical new wells, providing a range of sustainable yields for each of the prioritized aquifers. Metrics used to define sustainable yield included drawdown of groundwater levels between pumping wells, recharge from surface water sources, reductions in aquifer storage, aquifer dewatering, and the ability of an aquifer to recover between periods of higher pumping. Somewhat surprisingly, results indicate that large amounts of additional groundwater are available from the prioritized aquifers of the Coastal Plain. Predictably, the assessments revealed that little additional water is available from the Crystalline Rock aquifer of the Blue Ridge and Piedmont where population growth is highest. These groundwater assessments, along with assessments of surface water quality and quantity, forecasts of future water needs, and other information, have been presented to regional water planning councils, comprised of local lay citizens. The assessments will be used by them and the State of Georgia to develop water management practices that, in theory, will allow current and future water needs to be met without exceeding the sustainable yields of the aquifers.