GEOPHYSICAL APPLICATIONS IN MANAGED AQUIFER RECHARGE: INSIGHTS FROM COASTAL AND KARST AQUIFER SYSTEMS

Managed Aquifer Recharge (MAR) is a critical strategy for enhancing groundwater resources, particularly in regions facing water scarcity. This study explores the application of geophysical techniques in two distinct geological environments: coastal and karst aquifers, where MAR is set to be implemented. In the West Coast Aquifer System of South Africa, geophysical methods such as Electrical Resistivity Imaging (ERI) and Airborne Electromagnetic (AEM) were employed to characterize subsurface lithology, delineate the freshwater-saltwater interface, and propose infiltration basins. These techniques provided crucial insights into the heterogeneity of the aquifer, the movement of the recharge front, and the potential for saltwater intrusion, ensuring the sustainable management of the aquifer. In contrast, the karst system of the Arbuckle-Simpson aquifer in eastern Oklahoma, known for its complex, highly permeable structures, requires a different approach. Here, geophysical tools like the AEM and ERI were utilized to map subsurface cavities, conduits, and fracture zones, which are critical for understanding recharge dynamics. The high-resolution data obtained enabled the identification of preferential flow paths and the assessment of recharge efficiency. The lessons learned from these applications underscore the importance of tailoring geophysical techniques to the specific characteristics of the aquifer system. In coastal aquifers, the challenge lies in balancing recharge with the risk of saltwater intrusion, while in karst aquifers, the focus is on accurately identifying and managing complex subsurface features to optimize recharge. The study highlights the necessity of a site-specific approach to MAR, informed by detailed geophysical investigations, to enhance the effectiveness and sustainability of recharge operations in diverse geological settings.