105 Coastal Hydrogeology in an Age of Rising Seas (Posters)
As sea levels rise, understanding hydrogeology is crucial in coastal areas. Seawater intrusion can lead to loss of potable or agricultural water supplies, and water table rise due to increasing sea level can lead to increased flooding and affect infrastructure.
Monday, 20 October 2025
8:00 AM - 5:30 PM
HBGCC, Hall 1
Cutoff Wall Performance for Freshwater Lens Development and Seawater Intrusion Mitigation in Island Aquifers Subject to Sea-Level Rise and Altered Recharge
Paper number: 105-5
Program: Technical Sessions
Time: 8:00 AM – 8:00 AM
Authors
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Yipeng ZhangOklahoma State University, Stillwater, Oklahoma State
Abstract
Sea-level rise (SLR) and regional precipitation patterns lead to freshwater in island aquifers, the main water source for local communities, being at a higher risk of contamination from seawater intrusion (SWI). The freshwater typically forms a thin lens floating on top of the seawater. Installing a cutoff wall is considered a feasible strategy for protecting coastal fresh groundwater from SWI. However, the performance of the cutoff wall in managing freshwater lens (FWL) development and mitigating SWI into island aquifers under SLR and aquifer recharge (RCH) change remains inadequately quantified. This study investigated how water table elevation (WTE), FWL depth and thickness, and SWI extent, measured by changes in aquifer salt mass and fresh groundwater volume, in an island aquifer with a cutoff wall, respond to various conditions of SLR and RCH. The study focused on a simplified two-dimensional island aquifer model based on the hydrogeological conditions of islands in the Bahamian archipelago. Results demonstrate RCH critically influences cutoff wall effectiveness for FWL development and SWI mitigation, with higher RCH amplifying gains in WTE, FWL metrics, freshwater storage, and aquifer salt removal. The difference made by RCH to the cutoff wall performance in these metrics diminishes with increasing wall depth. SLR elevates WTE in a positive correlation manner with its magnitude but negligibly affects the cutoff wall performance in FWL enhancement and SWI mitigation. Cutoff walls are most efficient in low-RCH settings, yielding greater relative improvements in FWL development and SWI mitigation per unit wall depth increase.
Geological Society of America Abstracts with Programs. Vol. 57, No. 6
doi: 10.1130/abs/2025AM-413186
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