1-9 Evaluating Water Table Fluctuation in Karst Aquifers using Electrical Hydrogeology

Session: Advances in Managed Aquifer Recharge

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Understanding water table dynamics in fractured rock systems, particularly in karst aquifers, is a long-standing challenge in hydrogeology due to their complex structure and rapid response to recharge. Traditional monitoring wells often miss spatial variability in these systems, making geophysical methods a useful complementary tool. Time-lapse electrical resistivity imaging (TERI) offers a non-invasive approach to tracking subsurface moisture changes. However, its application in complex hydrogeological settings, such as managed aquifer recharge (MAR) sites, is still evolving. In this study, we applied TERI to monitor short-term water table fluctuations at an active MAR site underlain by a karst aquifer system within a mapped sinkhole conduit. A 56-electrode array with 4-meter spacing was deployed along a fixed transect, allowing for a vertical resolution of approximately 2 meters. TERI revealed systematic changes in subsurface resistivity, in both vadose and phreatic zones. Dry periods were marked by increased resistivity extending to the water table. At the same time, wet conditions produced a resistivity decrease at shallower depths, patterns consistent with drying and saturation of the vadose zone. The apparent movement of the resistivity interface raises the central question of this study: Can TERI reliably capture and quantify water table fluctuations in fractured karst terrains? To validate this interpretation, we integrated TERI with water level data from observation wells along the TERI line. This multi-method approach distinguished actual water table dynamics from other resistivity-influencing factors. The study contributes to the growing use of electrical hydrogeology for MAR, offering insight into how TERI can inform the design, operation, and performance evaluation of recharge interventions in complex aquifer systems.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-11148

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