[A-HW25] Near Surface Investigation and Modeling for Groundwater Resources Assessment and Conservation

[AHW25-01] From Mountains to Plains: Hydromechanical Interactions Driving Groundwater Recharge and Land Subsidence in the Context of Mountain Block Recharge

*Duc-Huy Tran¹、Shih-Jung Wang^1,2、Chun-Rong Chen³、Yung-Han Yang³ (1.Graduate Institute of Applied Geology, National Central University, Taoyuan, Taiwan、2.Department of Earth Sciences, National Central University, Taiwan、3.Industrial Technology Research Institute, Taiwan)

キーワード：Mountain block recharge, Geological model, Coupled hydromechanical model, Sustainable resource management, Land subsidence, Choushui River Alluvial Fan

Groundwater serves as the primary source of public water supply in plains, making a comprehensive understanding of groundwater recharge essential for sustainable management. Recharge primarily occurs in mountainous regions, foothills, and proximal alluvial fans, necessitating detailed studies of groundwater migration from mountain blocks to plains. Traditional models often fail to fully capture the complex dynamics of these processes, particularly the interactions between hydrological and mechanical factors. This study focuses on the hydromechanical interactions underlying groundwater recharge as a key factor in mitigating land subsidence and managing groundwater resources. Using a coupled hydro-mechanical model based on poroelastic theory, we investigated groundwater flow and deformation across the Douliu foothill and the Choushui River Alluvial Fan in Taiwan. To understand the impact of geological variability on the coupled system, we examined several complex geological models. Simulation results highlighted three key flow regimes: regional, local, and front slope flows, all significant for upstream recharge processes, particularly during the mountain-to-basin transition. Localized flow patterns were obtained within the mountain block when both mountain slopes and the river contributed to recharge. This underscores the mountain block's importance in recharging the plains, with the river significantly influencing groundwater recharge. While unconsolidated sediments experienced natural compaction due to gravity, bedrock showed negligible deformation. Comparative scenarios revealed that vertical displacement in the recharged plains remained consistent, whereas horizontal displacement varied, influencing 2D displacement patterns. These findings offer crucial insights for developing more predictive models of groundwater dynamics, improving groundwater resource management, and addressing land subsidence challenges.