Assessment of seawater intrusion vulnerability of coastal aquifers in context of climate change and sea level rise in the central coastal plains, Vietnam

Vietnam’s coastal aquifers face the challenge of saltwater intrusion due to factors like climate change, sea level rise, and over-exploitation. This issue is particularly prominent in the Central Coastal Region, where the plains are narrow and water resources are limited. In order to ensure sustainable management of groundwater, it is crucial to assess the vulnerability of Quaternary aquifers to saltwater intrusion. For evaluation of salt, fresh water distribution in the aquifers, we applied geophysical methods, along with water sampling and analysis from boreholes and wells. Additionally, we employed Geographic Information System (GIS) to delineate vulnerability zones to seawater intrusion. The GALDIT method, incorporating the Analytical Hierarchical Process (AHP), was used to assign weights to key indicators. The results indicate that saltwater intrusion has changed in recent years. In the North-central coastal plains, over half of the area (56.8% or 4061.8 km2) exhibits high vulnerability, while the South-central coastal plains show high vulnerability in approximately one-fifth of the area (18.8% or 1699 km2). Groundwater occurrence and the impact of existing seawater intrusion play pivotal roles in determining coastal aquifer vulnerability to saltwater intrusion. This underscores the significance of narrow, steep plains, and thin aquifers as key influential factors. To mitigate the risk of saltwater intrusion in production wells, it is crucial to consider regulating groundwater extraction in high vulnerability areas. This would limit capacity and minimize the possibility of saltwater intrusion. Effective management and exploitation of groundwater resources are essential for the sustainable development of Vietnam’s coastal regions.