[A-HW17] Near Surface Investigation and Modeling for Groundwater Resources Assessment and Conservation

[AHW17-07] Coupled HMC Model for the Investigation of the Influences of Geological Model Complexity in Simulating Seawater Intrusion and Land Subsidence

*Shih-Jung Wang^1,2、Huu-Duc Truong¹ (1.Graduate Institute of Applied Geology, National Central University、2.Department of Earth Sciences, National Central University)

キーワード：Coupled HMC model, Seawater intrusion, Land subsidence, Geological model complexity, Groundwater management, Taiwan Pingtung Plain

In the coastal areas, over-exploitation of groundwater results in a decrease in groundwater level, which may cause both seawater intrusion (SWI) and land subsidence (LS). Many projects and researches were performed to evaluate the impact and propose the management solutions to reduce SWI and LS impacts. However, conventional studies often conduct separated assessments for individual effect, resulting in solutions that address isolated issue. The Pingtung Plain, Taiwan, which surfer serious SWI and LS, was chosen as the study area. This study aims to develop a coupled model capable of simulating SWI and LS and propose the management solutions to mitigate both issues. Leveraging the principles of poroelastic and density-dependent flow, our study employs a finite element software of COMSOL Multiphysics to formulate a 2D comprehensive Hydraulic-Mechanical-Chemical (HMC) model. Three geological models ranging from homogeneous to heterogeneous were developed based on a regional geological profile constructed by the Geological Survey and Mining Management Agency, Taiwan. The results show that the HMC model signifies the efficacy and feasibility of simulating SWI and LS. Three geological models established from homogeneous to heterogeneous underscore the significant difference between SWI and LS behavior. Their behavior varies dramatically as the geological makeup becomes complex. Additionally, the study highlights the efficacy of the relocation pumping well and managed aquifer recharge approaches in alleviating the impacts of SWI and LS, which are toward groundwater sustainable development. Unmanaged groundwater extraction can unintentionally lead to increased severity of SWI and LS, even with minor pumping volumes. The HMC integrated model is a valuable method for assessing and enhancing the efficacy of concurrent management strategies targeting both SWI and LS. This study forms the fundamental underpinning for subsequent in-depth investigations and the formulation of optimal solutions for groundwater management in our forthcoming research.