This only happens once in the world.
In the southwest of Baden-Württemberg, in a triangle between the Swabian Alb, the Black Forest and Lake Constance, precisely in the Donaubergland between Immendingen and Fridingen in the Danube valley, the Danube simply disappears into the ground.
Danube seepage does not only occur locally at one point, but at numerous points in this region: it is a regional event.
But, and that’s the special thing: The water from the Danube reappears! South of the Danube seepage, the Danube water returns to the surface in the Aach spring. However, it comes up in a completely different river system, namely the Rhine water system.
The Danube water has passed underground under the European watershed.
Why does the Danube water seep away?
At Immendingen, the young Danube meets the limestone of the Swabian Alb. Year after year, this becomes more and more porous and water-permeable.
Here on the edge of the Swabian Alb between Immendingen and Fridingen, however, the shifts in the geological layers over the course of millions of years and the different composition of the layers of the Alb and Hegau or the Lake Constance region and Alpine foothills also play a decisive role. Here, the Danube can not only seep away, but in some places sink on a large scale.
What’s more, in the long term, the Rhine is literally taking water away from the Danube! This is because the Rhine Graben, and therefore the catchment area of the High Rhine, was formed later than the original Danube system. And it is lower than the Danube system. Clearly, the water flows downhill and therefore prefers to flow in this direction.
Exciting, because it continues unstoppably.
Elaborate dyeing experiments at the end of the 19th century and in the 20th century clearly demonstrated that the water that sinks and seeps away between Immendingen and Fridingen largely resurfaces after days in the Aach spring.
The picture uses (non-toxic) paint to demonstrate that the water at Immendingen simply disappears into the ground in the riverbed.
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By the way, absolutely attractive: the AlbCard – the guest card for the whole of the Swabian Alb – is also available from selected businesses in the Donaubergland.
