The Aachtopf () is
Germany
Germany,, officially the Federal Republic of Germany, is a country in Central Europe. It is the second most populous country in Europe after Russia, and the most populous member state of the European Union. Germany is situated betwe ...
's biggest
karst spring
A karst spring or karstic spring is a spring (outflow of groundwater) that is part of a karst hydrological system.
Description
Because of their often conical or inverted bowl shape, karst springs are also known in German-speaking lands as a ''Top ...
, south of the western end of the
Swabian Jura near the town of
Aach. It produces an average of 8,500 litres per second. Most of the water stems from the
River Danube
The Danube ( ; ) is a river that was once a long-standing frontier of the Roman Empire and today connects 10 European countries, running through their territories or being a border. Originating in Germany, the Danube flows southeast for , pa ...
where it disappears underground at the
Danube Sinkhole
Sinkhole in the Danube near Möhringen
Schematic of the sinkhole locations and the route to Aachtopf
Completely dry Danube riverbed
right , Sink hole on the southern bank of the Danube, at the main sinkhole site below Immendingen
Sign i ...
, north near
Immendingen
Immendingen is a municipality in the district of Tuttlingen in Baden-Württemberg in Germany located on the Upper Danube. It is famous for the Danube Sinkhole.
Geography
Immendingen is located on the Upper Danube. On the municipal area are part ...
and about north near
Fridingen
Fridingen () is a town in the district of Tuttlingen, in Baden-Württemberg, Germany. It is situated on the Danube, 10 km east of Tuttlingen, and 23 km west of Sigmaringen. A large hoard of Bronze Age jewellery (mostly armlets and brac ...
. The cave system has been explored since the 1960s, but as of 2020 only a small part has been discovered due to a large blockage after a few hundred metres.
Etymology
The name Aachtopf is compounded from ''Aach'' (meaning "water" in
Old High German
Old High German (OHG; german: Althochdeutsch (Ahd.)) is the earliest stage of the German language, conventionally covering the period from around 750 to 1050.
There is no standardised or supra-regional form of German at this period, and Old High ...
); ''Topf'' can be translated as "bowl" and is commonly used for round, bowl-shaped springs.
Geography
The Aachtopf is a
karst spring
A karst spring or karstic spring is a spring (outflow of groundwater) that is part of a karst hydrological system.
Description
Because of their often conical or inverted bowl shape, karst springs are also known in German-speaking lands as a ''Top ...
, south of the western end of the
Swabian Jura near the town of
Aach. The spring is the source of the river
Radolfzeller Aach
The Radolfzeller Aach (also known as Hegauer Aach) is a right or north tributary of the Rhine in the south of Baden-Württemberg (Germany). It is approximately 32 km long.
Course
The source of the river is the ''Aachtopf'' in Aach, the la ...
, which flows southward into
Lake Constance
Lake Constance (german: Bodensee, ) refers to three Body of water, bodies of water on the Rhine at the northern foot of the Alps: Upper Lake Constance (''Obersee''), Lower Lake Constance (''Untersee''), and a connecting stretch of the Rhine, ca ...
, and empties into the
Rhine
), Surselva, Graubünden, Switzerland
, source1_coordinates=
, source1_elevation =
, source2 = Rein Posteriur/Hinterrhein
, source2_location = Paradies Glacier, Graubünden, Switzerland
, source2_coordinates=
, so ...
.
Origin
The spring marks the southern end of a cave system that transports water from the western end of the Swabian Jura. It produces an average of 8,500 litres per second. Production varies seasonally and in response to the weather, but the spring never runs dry. Most of the water is derived from the
Danube
The Danube ( ; ) is a river that was once a long-standing frontier of the Roman Empire and today connects 10 European countries, running through their territories or being a border. Originating in Germany, the Danube flows southeast for , pa ...
where it disappears underground at the ''Donauversickerung'' (
Danube Sinkhole
Sinkhole in the Danube near Möhringen
Schematic of the sinkhole locations and the route to Aachtopf
Completely dry Danube riverbed
right , Sink hole on the southern bank of the Danube, at the main sinkhole site below Immendingen
Sign i ...
) near
Immendingen
Immendingen is a municipality in the district of Tuttlingen in Baden-Württemberg in Germany located on the Upper Danube. It is famous for the Danube Sinkhole.
Geography
Immendingen is located on the Upper Danube. On the municipal area are part ...
and
Fridingen
Fridingen () is a town in the district of Tuttlingen, in Baden-Württemberg, Germany. It is situated on the Danube, 10 km east of Tuttlingen, and 23 km west of Sigmaringen. A large hoard of Bronze Age jewellery (mostly armlets and brac ...
. The Rhine's steeper gradient on its much shorter route to the North Sea creates stronger
headward erosion
Headward erosion is erosion at the origin of a stream channel, which causes the origin to move back away from the direction of the stream flow, lengthening the stream channel.Essentials of Geology, 3rd Ed, Stephen Marshak It can also refer to ...
than that of the much older River Danube (see the
Danube upper river geology). This
stream capture of the upper Danube and its surface tributaries
is expected to cause the long-term disappearance of the Danube drainage entirely in favour of the Rhine.
The Danube flows eastwards into the
Black Sea
The Black Sea is a marginal mediterranean sea of the Atlantic Ocean lying between Europe and Asia, east of the Balkans, south of the East European Plain, west of the Caucasus, and north of Anatolia. It is bounded by Bulgaria, Georgia, Roma ...
, whereas the Rhine flows northwards to the
North Sea
The North Sea lies between Great Britain, Norway, Denmark, Germany, the Netherlands and Belgium. An epeiric sea on the European continental shelf, it connects to the Atlantic Ocean through the English Channel in the south and the Norwegian S ...
. Therefore, the water of the Aach flows under the
European watershed. This is a relatively common feature of karst stream captures.
The karst spring is connected to a huge cave, which runs northwards. The cave is completely water-filled and can only be explored by
cave diver
Cave-diving is underwater diving in water-filled caves. It may be done as an extreme sport, a way of exploring flooded caves for scientific investigation, or for the search for and recovery of divers or, as in the 2018 Thai cave rescue, other ...
s.
History of exploration
In 1719, F. W. Bräuninger published his hypothesis that the water of the spring originated from the Danube.
On 9 October 1877, the geologist
Adolf Knop
Adolf Knop (12 January 1828, in Altenau – 27 December 1893, in Karlsruhe) was a German geologist and mineralogist.
He studied mathematics and sciences at the University of Göttingen, where he was a pupil of chemist Friedrich Wohler and ...
from
Karlsruhe Technical College laced the water in the Danube basin with 10 kg
sodium fluorescein
Fluorescein is an organic compound and dye based on the xanthene tricyclic structural motif, formally belonging to triarylmethine dyes family. It is available as a dark orange/red powder slightly soluble in water and alcohol. It is widely used ...
, 20 zentner (1000 kg) of salt and 1200 kg of
shale oil
Shale oil is an unconventional oil produced from oil shale rock fragments by pyrolysis, hydrogenation, or thermal dissolution. These processes convert the organic matter within the rock (kerogen) into synthetic oil and gas. The resulting oil c ...
. After 60 hours he was able to detect all three substances in the spring, as evidenced by "splendidly green, salt water with a distinct
creosote
Creosote is a category of carbonaceous chemicals formed by the distillation of various tars and pyrolysis of plant-derived material, such as wood or fossil fuel. They are typically used as preservatives or antiseptics.
Some creosote types were ...
taste".
In 1886, the first attempt to dive down the Aachtopf (and one of the world’s first cave dives) was made, to , at the location of a bottleneck where the water has a strong flow.
In 1960, the first exploration of the cave was made by
Jochen Hasenmayer
Jochen Hasenmayer (born 28 October 1941 in Pforzheim, Germany) is a German speleologist and cave diver from Birkenfeld in Baden-Württemberg, whose spectacular dives have frequently made headlines.
Cave diving
Hasenmayer began his cave divin ...
, a famous German cave diver. from the spring the
syphon opens into a cavern, the "Seenhalle" (Lake Hall). A collapse blocks the cave after . The cave is expected to continue for several kilometres on the other side of the blockage.
In 1990, a local caving club was formed to find the lost cave segment towards the Danube basin by digging a shaft behind the collapse at the bottom of a large
sink hole
A sinkhole is a depression or hole in the ground caused by some form of collapse of the surface layer. The term is sometimes used to refer to doline, enclosed depressions that are locally also known as ''vrtače'' and shakeholes, and to openi ...
. In 1995, members discovered a cavern at deep, which they dubbed the Grey Hall,
and in 2003 another cavern with a lake, which Rudi Martin has described in a report.
The group has published maps of the "Donauhöhle".
As of 2020, exploration is ongoing and the continuation of the cave has not been discovered.
Fauna
In 2015, the only known
cavefish
Cavefish or cave fish is a generic term for fresh and brackish water fish adapted to life in caves and other underground habitats. Related terms are subterranean fish, troglomorphic fish, troglobitic fish, stygobitic fish, phreatic fish and ...
in Europe, a ''
Barbatula
''Barbatula'' is a genus of fish in the family Nemacheilidae native to Europe and Asia.Kottelat, M. (2012)Conspectus cobitidum: an inventory of the loaches of the world (Teleostei: Cypriniformes: Cobitoidei). ''Raffles Bulletin of Zoology, Suppl. ...
'' loach, was discovered in the Danube–Aachtopf system.
References
External links
Aachtopfshowcaves.com.
* 15 min
* 6 min
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{{coord, 47, 50, 48, N, 8, 51, 29, E, region:DE-BW_type:waterbody , display=title 43 min
Springs of Germany
Karst springs
Karst formations of Germany
Landforms of Baden-Württemberg
Caves of Germany
SAachtopf
SAachtopf
Geography of Hegau