Groundwater Vulnerability Assessment to Seawater Intrusion

Groundwater vulnerability assessment to seawater intrusion examines the susceptibility of coastal aquifers to the encroachment of saline water, threatening freshwater supplies. This field integrates hydrogeological characterisation, numerical modelling and index-based mapping to delineate zones at risk and to inform sustainable management. Key drivers include declining water tables, intensified pumping, land-use change, sea-level rise and aquifer geometry. Methods range from simple parametric approaches, such as composite vulnerability indices that combine groundwater depth, hydraulic conductivity, distance to the shoreline, aquifer thickness and anthropogenic loading, to advanced three-dimensional variable-density flow models coupling flow and transport. Geospatial technologies and remote sensing have improved spatial resolution and temporal monitoring, while geophysical methods offer non-invasive delineation of the fresh–salt interface. Recent developments have emphasised seasonality, future climate scenarios and land subsidence, yielding dynamic vulnerability maps tailored to management needs. Outputs guide targeted interventions such as artificial recharge, pumping optimisation and land-use regulation. The global significance of this work is underscored by the vulnerability of densely populated deltas, small island states and semi-arid coasts, where overexploitation of groundwater can rapidly shift an aquifer from safe to impaired. Effective vulnerability assessment thus underpins long-term water security for agriculture, industry and domestic supply in coastal regions worldwide.

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Groundwater Vulnerability Assessment to Seawater Intrusion publication trend

The graph below shows the total number of articles in groundwater vulnerability assessment to seawater intrusion across all publications each year (not limited to Nature Index journals).

Technical terms

Seawater intrusion: The landward movement of saline water into freshwater aquifers, induced by groundwater extraction or sea-level rise.

Intrinsic vulnerability: The inherent susceptibility of an aquifer to contamination, based on geological and hydrological properties, independent of contaminant type.

GALDIT index: A parametric vulnerability index combining Groundwater occurrence, Aquifer hydraulic conductivity, Loading (land use), Distance to shore, Impact of existing seawater intrusion, and Thickness of aquifer.

SEAWAT model: A numerical simulation tool that couples variable-density groundwater flow and solute transport to predict saltwater intrusion under different stress scenarios.

Shannon’s entropy: A statistical measure used in multi-criteria decision making to assign objective weights to parameters based on their information content and variability.

References

1. GALDIT Modification for Seasonal Seawater Intrusion Mapping Using Multi Criteria Decision Making Methods. Water (2022).
2. Actual and Forecasted Vulnerability Assessment to Seawater Intrusion via GALDIT-SUSI in the Volturno River Mouth (Italy). Remote Sensing (2021).
3. Vulnerability of a Tunisian Coastal Aquifer to Seawater Intrusion: Insights from the GALDIT Model. Water (2022).