Evolution of Coastal Groundwater Resources and Seawater Intrusion Under Climate Change Based on an Integrated Dynamic Model: A Case Study of Tra Vinh Province, Mekong Delta

Coastal groundwater resources are increasingly threatened by the dual pressures of over-exploitation and climate change. Revealing their evolutionary patterns and developing sustainable management strategies represent a global scientific challenge. This study developed an integrated groundwater flow and solute transport model using the Groundwater Modeling System (GMS) platform, taking Tra Vinh Province in the Mekong Delta as a representative case to systematically evaluate the hydrodynamic processes, water level variations, and salinity evolution of multi-layered coastal aquifer systems under combined anthropogenic and climatic stresses. The model was calibrated against observed groundwater levels from January 2007 to January 2017 and subsequently used to simulate groundwater and salinity evolution, with the available total dissolved solids (TDS) observations used to assess the consistency of the simulated salinity results. Through sensitivity analysis and scenario simulations, the study quantitatively identified the controlling roles of key parameters and the impacts of future climate change (primarily precipitation variations). The research provides three core findings that offer insights for similar coastal settings: (1) Influence of groundwater abstraction: Groundwater-level decline and seawater intrusion were strongly associated with sustained groundwater abstraction, and projected increases in groundwater recharge were insufficient to reverse the declining groundwater levels under the maintained abstraction conditions. (2) Differentiated parameter sensitivity patterns: Groundwater levels are most sensitive to hydraulic conductivity, boundary inflow is most sensitive to boundary conductance, and storage changes are jointly regulated by both parameters. (3) Limited effects of increased recharge: Projected increases in groundwater recharge were insufficient to reverse the continued groundwater-level decline under sustained abstraction, highlighting the importance of considering groundwater abstraction together with recharge in future groundwater management. This study not only provides scientific foundations for management strategies such as abstraction control and recharge management in Tra Vinh Province but also provides insights into the response of a coastal multi-layered aquifer system under combined anthropogenic and climatic stresses. It offers a methodological reference for groundwater resource management in similar intensively exploited deltas and coastal plains.