Enough freshwater beneath Malta's seafloor to last 75 years, study estimates

There is enough freshened groundwater below the Maltese seabed to provide a supply of potable water for 75 years, a study has revealed.

An international team of scientists has estimated the volume of fresh water offshore the Maltese islands to be around one cubic kilometre.

Offshore freshened groundwater is groundwater with salinity below that of seawater that is stored in sediments and rocks below the seafloor.

The scientists first developed a detailed 3D geological model of the Maltese islands and the adjacent seafloor to reach this estimate. They then used advanced numerical models to simulate how the groundwater system of the archipelago would evolve over time.

The simulation results showed how 18,000 years ago, during the Ice Age, the groundwater system extended across the entire continental shelf of the Maltese islands, which was exposed at the time. As a result of the ensuing sea-level rise, the continental shelf was drowned, and only a quarter of the original groundwater volume was preserved.

At present, offshore freshened groundwater is expected to predominantly occur between Malta and Gozo, and along the coast between Cirkewwa and Valletta, with the largest extensions ooccuring off St Paul's Bay, Salini and St Julian’s. The groundwater body is up to 100m thick and 3km from the coast.

But exploiting these offshore resources is no walk in the park. "The first issue is that most of the groundwater appears to be hosted in low permeability layers, meaning its extraction could be complicated and expensive; and a decrease in precipitation predicted for the coming 100 years, as a result of regional climate change, is expected to diminish offshore freshened groundwater extent by 40%," the scientists said.

The study is a product of the MARCAN project, which is led by Prof. Aaron Micallef from the Department of Geosciences of the University of Malta. It has just been published in the international journal Frontiers in Water. The team involved in this study includes scientists from Italy, USA and Finland.