Spatial Distribution of Groundwater Availability for Various Pumping Scenarios in Savannah Region

Abstract

Long-term pumping from the Upper Floridan Aquifer (UFA) in the Savannah region, Georgia has lowered groundwater piezometric heads significantly. This resulted in salt water intrusion and brackish water contamination of the aquifer at Hilton Head Island, S.C. The aquifer is a primary source of drinking and industrial process water in the region, thus, various categories of users apply for groundwater withdrawal permits. The Georgia Environmental Protection Division (EPD) wants to develop a long term groundwater management plan which will protect the UFA from further salt water intrusion and also allow additional groundwater withdrawals from the aquifer. To achieve this goal, EPD first developed an “Interim Strategy for Managing Salt Water Intrusion in the Upper Floridan Aquifer of Southeast Georgia (EPD 1997)”. In this interim strategy, EPD has identified an area for enforced protection near the City of Savannah. Thus, since 1997, EPD has not issued permits for groundwater withdrawal from the UFA in the northern-capped area unless such water is reallocated from a permit reduction elsewhere within the northern-capped area (EPD 2004). EPD also initiated a program called Coastal Sound Science Initiative (CSSI) to generate data and information for developing a plan for managing salt water intrusion (EPD 2005). EPD’s goal was to find answers for various questions related with the salt water intrusion problem in the region. Two of these questions were: (i) Can areas having minimal impact on salt water intrusion be identified and what amount of water can be obtained from them?, and (ii) What are the other fresh water sources in coastal Georgia and what amount of water can be obtained from them? In this study, we proposed a coupled simulationoptimization model to determine spatial distribution of additional groundwater availability within the Savannah region. We used this model to investigate spatial distribution of groundwater availability for various management scenarios, such as groundwater is withdrawn from the Lower Floridan Aquifer (LFA) from the UFA, or from the LFA and the UFA simultaneously (UFA+LFA). The results obtained from this analysis will be useful in answering the two questions posed by EPD and also will provide preliminary guidance in long term management and planning goals.