17:15 〜 19:15
[AHW26-P04] Exploring the effects of pumping-induced land subsidence on the leaching of saline water from aquitards
キーワード：Saline water leaching, COMSOL, Freshening, Land subsidence, Aquitard
Salty and brackish groundwater has been observed in many coastal areas. In some areas, high salinity in groundwater extends several kilometers inland, particularly in groundwater systems within Quaternary deltas. This phenomenon can limit access to safe freshwater resources and lead to deeper groundwater abstraction under the belief that deeper groundwater is safer and less contaminated (Erban et al., 2013). However, deep groundwater development may cause land subsidence and leaching of saline water trapped in the aquitard into the surrounding aquifers. This study aims to explore how groundwater pumping-induced land subsidence affects the leaching of saline water trapped in aquitards into surrounding aquifers. The study used COMSOL Multiphysics to perform vertical two-dimensional (2D) numerical simulations, calculating flow, solute transport, and deformation. Groundwater flow was calculated using Darcy’s Law. Solute transport in porous media was calculated using the mass conservation equation, incorporating diffusion, advection, and dispersion. Vertical deformation was calculated based on Terzaghi’s theory.
Henry’s problem was used as a benchmark test case for density-driven flow and solute transport. It was then modified to incorporate the interlayered aquifer-aquitard characteristics of the coastal groundwater system. The results showed that the saline water leached from the confining aquitard could be flushed out over time, depending on the aquitard's thickness and permeability. Thicker saline aquitards would take longer to be freshened in comparison to thinner aquitards.
Initial speculations suggest that groundwater pumping alters pore water pressure and hydraulic gradients, leading to aquitard compaction and the leaching of saline water into the underlying aquifer, and affecting groundwater storage and freshening. To further investigate the effects of groundwater pumping on the saline water leaching and freshening processes, the deformation module will be coupled into the modified test case, and the results will be analyzed to incorporate into the study domain.
Henry’s problem was used as a benchmark test case for density-driven flow and solute transport. It was then modified to incorporate the interlayered aquifer-aquitard characteristics of the coastal groundwater system. The results showed that the saline water leached from the confining aquitard could be flushed out over time, depending on the aquitard's thickness and permeability. Thicker saline aquitards would take longer to be freshened in comparison to thinner aquitards.
Initial speculations suggest that groundwater pumping alters pore water pressure and hydraulic gradients, leading to aquitard compaction and the leaching of saline water into the underlying aquifer, and affecting groundwater storage and freshening. To further investigate the effects of groundwater pumping on the saline water leaching and freshening processes, the deformation module will be coupled into the modified test case, and the results will be analyzed to incorporate into the study domain.