Searching for drinking water under the sea

During these periods, the polar ice sheets increased, while global sea levels sank by more than 100 meters compared to today’s levels. Consequently, shallow coastal waters around the entire world – known as shelf areas – became dry land. As rain or snow fell on these surfaces, the water seeped down into the ground and formed groundwater reserves there. When sea levels rose at the end of the ice age, the shelf regions were flooded again. Since then, the reserves of groundwater deep below the surface have been offshore. “Estimates suggest that around 500,000 cubic kilometers of fresh water are stored in offshore groundwater reserves around the world. This would be enough to fill the Black Sea and is naturally cause for hope, especially in arid coastal states like Malta and other Mediterranean countries as well as South Africa and Mexico,” says Jegen. 

But where these reservoirs are located, how large they are, and whether they can be used as sources of drinking water is still relatively unknown. In order to answer these questions, which are key for Malta’s future, Jegen and two colleagues from GEOMAR, Christian Berndt and Bradley Weymer, teamed up with partners in Malta to launch an interdisciplinary joint project called SMART, which is funded by Helmholtz. The SMART team’s goal is to identify layers of rock that contain groundwater.

To do this, the geophysicist has to carry out searches of the seabed at depths of up to 400 meters. This is the depth at which the hard, highly porous limestone that stores water like a sponge is found. “We don’t just want to find out where these offshore reserves of groundwater are located – we also want to know whether they’re connected to land,” the scientist says. That’s because if a connection does exist, it’s possible that current plants used to pump groundwater on land have already tapped into reservoirs that are actually under the sea.

They work for up to 18 hours a day, and their days begin at five in the morning because the team’s vacation home is located an hour away from the harbor by car. But no one complains. “My group and I usually research the deep seabed and analyze methane hydrates and metal deposits there which could be relevant in the distant future,” explains Jegen. “But searching for offshore groundwater means we’re now working on a topic that has current, direct significance for millions of people. This is applied research, and it really drives us.” The team typically only goes back to bed long after darkness has fallen, returning to their accommodation on one of the long arterial routes leading through expanding suburbs and past densely built-up bays. Tourism and economic growth have come at a price. People in Malta have conflicting outlooks on this boom, Jegen says, sharing her impressions: “On the one hand, it opens up better job opportunities and offers prospects, especially for young people. But the noise, hectic pace, and demand for resources that come with it are overwhelming residents who have lived here for a long time. I found the people to be friendly, relaxed, and open. They love good food, community, and family and still put up elaborate decorations for the processions on Catholic feast days. So tradition and modernity come up against each other in many areas here.”

As far as tradition goes, Jegen enjoys Maltese cuisine in particular. “In culinary terms, the entire Mediterranean region comes together on the island. Only rarely have I enjoyed such a diverse variety of delicious food, and so much of it,” the scientist enthuses. Jegen is actively shaping Malta’s modern side – for example, by working with her SMART colleagues to provide young scientists from various countries with training in marine electromagnetics and seismology. They began by hosting a summer school in Malta that included visits from the world’s leading experts, during which they presented their methods. “After acquiring this knowledge, our young colleagues can push forward with the search for offshore groundwater in their home countries,” Jegen says. 

She is planning to return to Malta herself in December 2020. Together with the SMART team, her aim on this trip will be to conduct a comprehensive search of the country’s shelf areas from on board the METEOR, a German research vessel. The scientists then want to be able to provide clear recommendations as to whether the seabed could potentially offer a sustainable solution for Malta’s water crisis by the project’s end in 2021 at the latest.