Danube Sinkhole

The term "sinking" is more accurate than "seeping", because, instead of just distributing into the soil, the Danube's water flows through caverns to the Aachtopf, where it emerges as the river Radolfzeller Aach, a tributary of Lake Constance and the Rhine, respectively.

[citation needed] The first documented case of the Danube completely disappearing into the hole dates back to 1874.

The "disappeared" water travels south through cracks and fissures, and after 12 kilometers, it re-emerges at the Aachtopf spring at an altitude of about 475 meters.

Aachtopf has an impressive flow rate of 8,500 liters per second and plays a key role as the main source of mineral water in Germany.

[6] In 1927, a case was brought before the Supreme Court of the German Reich between Württemberg and Prussia as the ruler of the Hohenzollern Province on the one hand, and the state of Baden on the other hand, to decide the smoldering controversy over the quantitative impact of the Danube sinkhole, which is known as the Danube Sinkhole case [de] (German: Donauversinkungsfall).

[7] In January 1937, the "Donau-Aach-Gesetz" gave the Reich Minister for Agriculture the authority to decide on necessary measures and who was to pay the costs.

The underground river Danube annually removes about 7,000 tons of lime, that is 2,700 m3 in volume, from the karst system.

Future expansions or collapses in the underground system are conceivable, which would show above ground as sinkholes or ponors.