Fresh water found beneath the Gulf of Corinth seabed

An international team has mapped “offshore freshened groundwater” — low-salinity water stored in sediments beneath the Gulf of Corinth — and explained how it formed. The peer-reviewed study, published in Hydrogeology Journal, shows that long ice-age sea-level drops allowed rain and river water to seep into coastal and shelf sediments, where part of it is still preserved today. 

Figure of the pysiographic map of the Gulf of Corinth (GOC) and its surroundings. Black dashed line (labeled Fig. 5) shows the location of N-S trending profile where the 2D geological model is constructed.

What the scientists found:

• Low-salinity water occurs roughly 20 to 600–700 metres below the seafloor in the gulf’s central basin, and about 15 to 150 metres below the seafloor in the eastern Alkyonides area.

• Computer simulations of the last 800,000 years confirm that these waters were mainly emplaced during ice ages, when sea level was much lower.

• Laterally continuous sediment layers in the basin may hold up to about 250 cubic kilometres of this freshened groundwater. 

Why it matters:

Greece, like many Mediterranean countries, faces growing pressure on water resources. Mapping where offshore freshened groundwater occurs — and understanding how geology protects it — gives authorities a clearer picture of the subsurface. The study provides evidence to guide future research and careful policy discussions.

Figures of statistical modelling of 3D salinity in the central sub-basin (Fig. 9b) and present-day salinity model on the profile (Fig. 11).

How the study was done:

The team combined information from scientific drilling in the gulf with seismic reflection profiles and computer models that track changes in water salinity through time. Together, these methods reveal where freshened water is most likely to be stored and how it has moved since the ice ages. 

Article details:

“Geological and sea level controls on offshore freshened groundwater in a rift basin: Gulf of Corinth, Greece,” Hydrogeology Journal, published 19 September 2025.

Authors:

Dr Senay Horozal, Prof. Aaron Micallef, Michele De Biase and Francesco Chidichimo.

Open-access article available via Springer Nature. 

Media contact: 

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