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From Frankfurt to Basel, deep underground lies a treasure that supplies more than five million people in the region with drinking water. It is Europe\u2019s largest groundwater reserve. It stretches for around 300 kilometres below the surface and feeds, for example, the Upper Rhine and numerous wetlands.<\/p>\n
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But this huge groundwater reservoir is heavily polluted, as a study published in June has shown. Plant protection products, pharmaceutical residues and synthetic industrial chemicals, so\u2011called per- and polyfluoroalkyl substances (PFAS), are contaminating the groundwater; corresponding trace substances have been detected.<\/p>\n
This underground basin with a capacity of 150 billion cubic metres is not only vital for drinking water, it also has an impact on countless animal and plant species. New discoveries are made again and again, such as the groundwater crustacean species \u201cParabathynella baden-wuerttembergensis\u201d. A journey beneath the surface between Germany, France and Switzerland.<\/p>\n
Underground: the invisible river in the Rhine Valley<\/p>\n
The reservoir extends from Frankfurt am Main across the French border to Strasbourg and further south to Basel in Switzerland. The volume of water is hard to grasp \u2013 150 billion cubic metres corresponds to roughly 60 million Olympic-sized swimming pools.<\/p>\n
The groundwater reserve in the Upper Rhine Valley is roughly equivalent in size to three interconnected Lake Constances underground. Lake Constance itself contains around 48 billion cubic metres of water.<\/p>\n
Groundwater is the term used when the surrounding soil is permanently saturated with water. The layers above are not constantly moist; this is known as the unsaturated soil zone. Depending on the season and rainfall, the water table can rise or fall.<\/p>\n
The groundwater used for drinking water is often only a few, or at most a few hundred, metres deep. In some places it flows just about a metre below the surface, slowly northwards. But in the Upper Rhine Graben drilling has already reached 3,335 metres towards the Earth\u2019s core. The so\u2011called \u201cFrankenthal 10\u201d operation was carried out between Mannheim and Worms and is considered the deepest borehole to date.<\/p>\n
The deepest known section of the Upper Rhine Graben is the so\u2011called Heidelberger Loch, where the groundwater lies at a depth of more than 500 metres. Researchers say other areas are as little explored as the deep sea.<\/p>\n
Pesticides and pharmaceutical waste: pollution from harmful substances<\/p>\n
As Europe\u2019s largest groundwater body, the Upper Rhine Valley supplies almost five million people in the catchment area with drinking water. Compared with other major reservoirs in Europe, it is therefore one of the most valuable groundwater systems.<\/p>\n