Danube-Networkers
The Danube seepage near Immendingen / Fridingen
Text / Pictures: Heinz und Christel Pfeiffer
The Swabian Jura is a plateau run through by many rivers. It covers an area of about 8.000 square kilometres. Its highest mountain is called Lemberg at an altitude of 1015 metres. Its uniqueness among the German highlands is due to the fact that the Swabian Jura is karst country. This means that the basic substance of its rocks is limestone soluble in water. With the help of water and oxygen this limestone is dissolved and thus has contributed to the creation of hundreds of underground caves. Seen on geologic maps the underground of the Swabian Jura looks like a Swiss cheese.
These caves going down to a depth of approximately 200 metres run through the whole territory. In these depths divers starting from the Blautopf at Blaubeuren have discovered stalactite caves around 40 metres high and 80 metres large. There are also a large number of caves open to the public.
Ground water is found at a depth of 150 to 200 metres. On its way down rain water is seeping through the different layers of rock thus dissolving the limestone - and this has been happening for millions of years. It is suggested that underneath 200 metres large subterranean lakes can be found.
This geologic phenomenon explains why at Immendingen / Fridingen the waters of the Danube suddenly disappear in the underground. They are seeping into the labyrinth of subterranean caves of the Swabian Jura. Experiments with oil-containing colours have shown that parts of the Danube's waters are running underground in the direction of the south thus reaching the source of the river Ach and Lake Konstanz. From there via the Rhine valley they are streaming into the Atlantic Ocean. The other part of the water is reappearing on the surface a couple of kilometres further down in the bed of the Danube thus reaching the Black Sea after a journey of more than 2800 kilometres. The Danube is the only European river whose waters are streaming into the Atlantic Ocean as well as into the Black Sea.
