at Aachtopf was described as "gorgeously green lit" by the fluorescein and tasting of creosote. Later, the connection of the individual sinkholes was explored. In 1908 an experiment of downing water in Fridingen in the presence of Baden and Württemberg Government representatives confirmed the assumption of Professor Endrist -Stuttgart that the Fridingen sinkhole not only leads to the Aach, but that large amounts of it could also be artificially induced. A German newspaper in the US reported about the event. In about 1908, a shaft was dug in Fridingen in an attempt to find out where the water of this sinkhole disappears to. 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 ().The Court rendered an interim decision and left the final settlement to an agreement between the parties. In January 1937, the "Donau-Aach-Gesetz" gave the Reich Minister the authority to decide on necessary measures and who was to pay the costs. After WWII, in 1967, a canal was built between Immendingen and Möhringen, which brings water to Tuttlingen during times of low water levels. Outlook As the karst is developing, future sinkhole stretches cannot be accurately predicted. 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. In the long run, today's upper Danube will probably be redirected entirely into the Radolfzeller Aach, and thus to the Rhine. This would mean that other tributaries that are currently insignificant would become the new headwaters of the Danube. The Danube has experienced a similar stream capture further upstream, during the Würm glaciation, when the Feldberg-Danube was captured by the Wutach at the Wutach Gorge near Blumberg. Coordinates The water of the Danube is captured at the sinkholes in Immendingen () and Fridingen () and emerges at Aachtopf (). It flows into Lake Constance at Radolfzell (). The Rhine flows out of Lake Constance () and towards Basel, where it turns north (). When the Rhine captures the headwaters of the Danube