在沿海地區，地下水的過度開採導致地下水位下降，可能引起海水入侵（seawater intrusion）和地層下陷（land subsidence）的問題。為評估相關影響並提出減輕海水入侵和地層下陷的管理解決方案，文獻中進行了許多研究。然而，過去研究通常僅針對地層下陷或海水入侵個別進行評估，導致解決方案只解決單一的問題。臺灣屏東平原，面臨嚴重的海水入侵和地層下陷問題，因此挑選作為研究區。本研究旨在建立一個耦合模型，能夠同時模擬海水入侵和地層下陷行為，並應用建立模式提出管理解決方案，以助於減緩這兩個問題。研究中以地礦中心的水文地質剖面為基礎，建立了均質到異質的三個二維度剖面地質模型；數值模式則使用COMSOL Multiphysics有限元素軟體平台，結合孔彈性理論（poroelastic theory）與密度相依流體（density-dependent flow）模組，依據地質模型分別建立二維度水力-力學-化學（HMC）耦合模式。結果顯示，本研究成功建立HMC耦合數值模式，並用於模擬海水入侵和地層下陷問題，了解HMC耦合模式交互作用行為。而從均質到異質的地質模型比較中，突顯了地質模型對海水入侵和地層下陷行為的影響差異。隨著地質模型變得複雜，HMC耦合行為也更加複雜且更為顯著。此外，本研究進行了抽水井往內陸移動和海岸帶注入淡水之方案模擬，以評估與定量各方案在減緩海水入侵與地層下陷的有效性。研究結果顯示出，未受控制的地下水開發，將導致海水入侵和地層下陷加劇，即使抽水量很小也是如此，且海水入侵在停止抽水後，海淡水交界面不易退回。本研究提出HMC耦合模式，同時針對海水入侵和地層下陷問題進行模擬與評估，研究成果為制定地下水管理的解決方案奠定了重要的基礎。;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 each 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.
