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An interesting and little-known fact is that the Danube in Germany does exactly the same for roughly 155 days per year [1], which is called "Donauversinkung" ("

by lqet 8y ago

An interesting and little-known fact is that the Danube in Germany does exactly the same for roughly 155 days per year [1], which is called "Donauversinkung" ("swallowing of the Danube"). Between the towns of Immendingen and Fridingen on the Swabian Alb the water just disappears underground [2]. This started to happen around 300 years ago, and until the 1870s nobody knew exactly where it went. They then did experiments with Uranin and ultimately proved that the water re-surfaces in the Aachtopf [3]. Now, the water from the Aachtopf flows directly into Lake Constance, therefore into the Rhine, and therefore into the North Sea. Normally, the Danube flows into the Black Sea, which essentially means that on roughly 155 days per year, the disappearing water moves the European watershed [4], which I find highly fascinating. E: as the Danube laters flows through the once independent state of Württemberg, and the Rhine through the once independent state of Baden, there was also a nice court battle between them because of the lost water in the 1920s - the "Donauversinkungsfall" [5] ("the court case of the swallowing of the Danube") [1] https://en.wikipedia.org/wiki/Danube_Sinkhole https://en.wikipedia.org/wiki/Danube_Sinkhole [2] https://upload.wikimedia.org/wikipedia/commons/2/20/Donauversinkung.jpg https://upload.wikimedia.org/wikipedia/commons/2/20/Donauver... [3] https://en.wikipedia.org/wiki/Aachtopf#/media/File:AachTopfPano02.jpg https://en.wikipedia.org/wiki/Aachtopf#/media/File:AachTopfP... [4] https://en.wikipedia.org/wiki/European_watershed https://en.wikipedia.org/wiki/European_watershed [5] https://de.wikipedia.org/wiki/Donauversinkungsfall https://de.wikipedia.org/wiki/Donauversinkungsfall

dmix 8y ago
[1] links to the main Wikipedia page on the phenomenon as well: https://en.wikipedia.org/wiki/Stream_capture?oldformat=true https://en.wikipedia.org/wiki/Stream_capture?oldformat=true
sophistication 8y ago
Am I understanding correctly that the Danube always seeps into the ground near Immendingen (since 300 years), but if the conditions are dry enough there is not enough water to flow past this sink hole, so all of it drains into the European watershed? It should be noted that this only the first few hundred meters of the Danube and it's relatively flat there so the exact way the water sheds is probably always subject to changes up there (at least across large spans of time). There are relatively small masses of water that flow up there, so things are not set in stone as much (literally).
- lqet 8y ago
  This is correct. The main sinkhole is roughly 3 km downstream from the source. Disappearing water was first noticed 300 years ago, and the first total disappearance was in the 1870s. It is expected that this process will eventually make a small creek [1] the new source river of the Danube over the next 1,000 to 10,000 years. There is a group of hobby enthusiasts who are digging into the cave system since 1990 [2], expecting to find a cave containing an enormous underground lake, as the amount of water disappearing into the underground is much larger than the amount of water later carried by the Aach. AFAIR, they managed to finally reach the underground river ~15 years ago. arte did a documentary about them, called "Die schwarze Donau" ("The black Danube"). You find it on YouTube, but it's in German. E: here is an image of the underground Danube found by the hobbyists mentioned above after 13 years of digging: http://www.wolfgang-bauer.info/pages/reportagen/schwarze_donau/gfx/gfx_content_breit.jpg http://www.wolfgang-bauer.info/pages/reportagen/schwarze_don... E2: if you are interested in the subject, I highly recommend visiting the Skocjan cave in Slovenia, which was also formed in a karst region by an underground river. I found the visit to be an almost surreal experience [3][4][5]. [1] https://de.wikipedia.org/wiki/Kr%C3%A4henbach_(Donau) https://de.wikipedia.org/wiki/Kr%C3%A4henbach_(Donau) [2] http://www.wolfgang-bauer.info/pages/reportagen/schwarze_donau/schwarze_donau.html http://www.wolfgang-bauer.info/pages/reportagen/schwarze_don... [3] https://cache-graphicslib.viator.com/graphicslib/thumbs674x446/41626/SITours/one-day-karst-and-sunny-vipava-valley-tour-in-bovec-538902.jpg https://cache-graphicslib.viator.com/graphicslib/thumbs674x4... [4] https://cdn.tourismontheedge.com/wp-content/uploads/2011/02/DSC_2293_skocjanske_jame_cerkvenikov_most_big.jpg https://cdn.tourismontheedge.com/wp-content/uploads/2011/02/... [5] http://www.pension-silvia.si/images/activities/the_skocjan_caves/pension_silvia_the_skocjan_caves_05.jpg http://www.pension-silvia.si/images/activities/the_skocjan_c...
  - yread 8y ago
    interesting. You can visit a similar cave system with an underground river (and go on a boat ride) in Czech Republic https://en.m.wikipedia.org/wiki/Punkva_Caves https://en.m.wikipedia.org/wiki/Punkva_Caves

by lqet 8y ago

dmix 8y ago

[1] links to the main Wikipedia page on the phenomenon as well: https://en.wikipedia.org/wiki/Stream_capture?oldformat=true https://en.wikipedia.org/wiki/Stream_capture?oldformat=true

sophistication 8y ago

Am I understanding correctly that the Danube always seeps into the ground near Immendingen (since 300 years), but if the conditions are dry enough there is not enough water to flow past this sink hole, so all of it drains into the European watershed? It should be noted that this only the first few hundred meters of the Danube and it's relatively flat there so the exact way the water sheds is probably always subject to changes up there (at least across large spans of time). There are relatively small masses of water that flow up there, so things are not set in stone as much (literally).

lqet 8y ago
This is correct. The main sinkhole is roughly 3 km downstream from the source. Disappearing water was first noticed 300 years ago, and the first total disappearance was in the 1870s. It is expected that this process will eventually make a small creek [1] the new source river of the Danube over the next 1,000 to 10,000 years. There is a group of hobby enthusiasts who are digging into the cave system since 1990 [2], expecting to find a cave containing an enormous underground lake, as the amount of water disappearing into the underground is much larger than the amount of water later carried by the Aach. AFAIR, they managed to finally reach the underground river ~15 years ago. arte did a documentary about them, called "Die schwarze Donau" ("The black Danube"). You find it on YouTube, but it's in German. E: here is an image of the underground Danube found by the hobbyists mentioned above after 13 years of digging: http://www.wolfgang-bauer.info/pages/reportagen/schwarze_donau/gfx/gfx_content_breit.jpg http://www.wolfgang-bauer.info/pages/reportagen/schwarze_don... E2: if you are interested in the subject, I highly recommend visiting the Skocjan cave in Slovenia, which was also formed in a karst region by an underground river. I found the visit to be an almost surreal experience [3][4][5]. [1] https://de.wikipedia.org/wiki/Kr%C3%A4henbach_(Donau) https://de.wikipedia.org/wiki/Kr%C3%A4henbach_(Donau) [2] http://www.wolfgang-bauer.info/pages/reportagen/schwarze_donau/schwarze_donau.html http://www.wolfgang-bauer.info/pages/reportagen/schwarze_don... [3] https://cache-graphicslib.viator.com/graphicslib/thumbs674x446/41626/SITours/one-day-karst-and-sunny-vipava-valley-tour-in-bovec-538902.jpg https://cache-graphicslib.viator.com/graphicslib/thumbs674x4... [4] https://cdn.tourismontheedge.com/wp-content/uploads/2011/02/DSC_2293_skocjanske_jame_cerkvenikov_most_big.jpg https://cdn.tourismontheedge.com/wp-content/uploads/2011/02/... [5] http://www.pension-silvia.si/images/activities/the_skocjan_caves/pension_silvia_the_skocjan_caves_05.jpg http://www.pension-silvia.si/images/activities/the_skocjan_c...
- yread 8y ago
  interesting. You can visit a similar cave system with an underground river (and go on a boat ride) in Czech Republic https://en.m.wikipedia.org/wiki/Punkva_Caves https://en.m.wikipedia.org/wiki/Punkva_Caves