Tidal Influences on Groundwater Dynamics in Coastal Aquifers

Coastal aquifers occupy a critical position where terrestrial freshwater interacts with marine systems. Tidal forcing induces cyclical fluctuations in groundwater levels, influencing the position of the freshwater–saltwater interface and the quality of pumped water. These oscillations propagate landwards, attenuating in amplitude and exhibiting a phase shift relative to sea‐level changes. The magnitude of tidal influence depends on aquifer properties such as permeability, porosity and storativity, as well as on the presence of semi‐impermeable layers (aquitards). In unconfined settings, tidal waves generate watertable fluctuations that affect recharge through the vadose zone, while in confined or leaky aquifers, the tidal signal conveys information on leakage rates and barrier integrity. Heterogeneity in hydraulic conductivity and anisotropy further modulate tidal responses, often leading to spatially variable head dynamics. The combined effects of tides, recharge variability and geological layering control salinity intrusion, thermal regimes and contaminant transport. Understanding these processes is vital for sustainable groundwater management, mitigation of seawater intrusion, and adaptation to sea‐level rise in coastal zones worldwide.

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Tidal Influences on Groundwater Dynamics in Coastal Aquifers publication trend

The graph below shows the total number of articles in tidal influences on groundwater dynamics in coastal aquifers across all publications each year (not limited to Nature Index journals).

Technical terms

Aquifer: A geological formation that can store and transmit significant quantities of groundwater.

Aquitard: A low‐permeability layer that restricts but does not entirely prevent fluid flow between adjacent aquifers.

Freshwater–saltwater interface: The transition zone where freshwater and seawater meet, often described by a salinity gradient.

Amplitude attenuation: The reduction in tidal signal magnitude as it propagates through an aquifer.

Phase shift: The time lag between the peak of sea‐level oscillations and the corresponding peak in groundwater head.

Hydraulic conductivity: A measure of a material’s ability to transmit water, dependent on pore structure and fluid viscosity.

Storativity (specific storage): The volume of water released from or taken into storage per unit surface area per unit change in hydraulic head.

References

1. A study on the influence of tides on the water table conditions of the shallow coastal aquifers. Applied Water Science (2018).
2. Tidal Response of Groundwater in an Anisotropic Leaky Aquifer. Water Resources Research (2025).
3. Groundwater Monitoring Systems to Understand Sea Water Intrusion Dynamics in the Mediterranean: The Neretva Valley and the Southern Venice Coastal Aquifers Case Studies. Water (2021).
4. Salinity and Temperature Variations near the Freshwater-Saltwater Interface in Coastal Aquifers Induced by Ocean Tides and Changes in Recharge. Water (2022).
5. Heterogeneous hydraulic properties of an insular aquifer clarified by a tidal response method with simple decomposition techniques. Geologia Croatica (2018).