Seawater Intrusion and Groundwater Management in Coastal Aquifers

Coastal aquifers worldwide provide critical freshwater resources for drinking, irrigation and ecosystem support but are increasingly threatened by the landward advance of seawater. Seawater intrusion occurs when groundwater extraction, sea-level rise or reduced recharge upset the natural balance between freshwater and saltwater, allowing a denser saline wedge to encroach beneath the freshwater lens. The process is governed by hydrogeological setting, aquifer heterogeneity and geological history, and may be compounded by geochemical reactions that mobilise palaeo-saline waters or release ions from mineral dissolution. Effective management relies on accurate characterisation of the freshwater–saltwater interface, monitoring of hydraulic heads and salinity, and predictive modelling to explore scenarios of pumping, recharge and climate change. Strategies such as managed aquifer recharge, pumping optimisation, well‐field zoning and regulatory limits on abstraction have shown promise in mitigating intrusion. Integrating geophysical surveys, geostatistical mapping and density-dependent flow–transport simulations allows stakeholders to delineate vulnerable zones, set salinity thresholds for different uses and design adaptive interventions. As pressure on coastal zones intensifies, combining multidisciplinary observations with community engagement and policy frameworks remains essential to safeguard coastal groundwater supplies.

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Seawater Intrusion and Groundwater Management in Coastal Aquifers publication trend

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Technical terms

Coastal aquifer: A groundwater reservoir in coastal zones influenced by interactions with seawater.

Saltwater wedge: Intrusive lens of saline water extending beneath freshwater in a coastal aquifer due to density differences.

Freshwater–saltwater interface: Boundary separating fresh and saline groundwater within an aquifer system.

Managed aquifer recharge: Deliberate enhancement of groundwater by artificial or natural means to counteract depletion.

Monte Carlo simulation: A stochastic method using random sampling to quantify uncertainty in model predictions.

Electrical conductivity (EC): A measure of water’s ion concentration, used as a proxy for salinity levels.

References

1. Modeling stochastic saline groundwater occurrence in coastal aquifers. Water Research (2023).
2. The Issue of Groundwater Salinization in Coastal Areas of the Mediterranean Region: A Review. Water (2021).
3. A global dataset of surface water and groundwater salinity measurements from 1980–2019. Scientific Data (2020).