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Danube in Ulm
The Danube (Bulgarian Dunav,
German Donau, Greek Ister, Hungarian
Duna, Latin Danubius, Romanian Dunărea, Serbian and Croatian Dunav,
Slovak Dunaj, Ukrainian Dunay) is the second-longest river in
Europe (the Volga being the
longest).
It is the only major European river to flow from west to east.
It rises in Germany in the Black
Forest as two smaller rivers called Brigach and Breg, which join in Donaueschingen and are called Donau henceforth, flowing south-east for a distance of about 2850 km (1770 miles), to the Black Sea in
Romania where the Danube Delta
is.
A map showing the Danube
The Danube is an important international waterway. It flows through ten countries (Germany, Austria, Slovakia, Hungary, Croatia, Serbia, Bulgaria,
Romania, and Ukraine), with tributary
rivers in seven other countries. It flows through the following large cities:
After the construction of the German Rhine-Main-Danube
Canal in 1992, the river is part of a trans-european waterway from Rotterdam on the North Sea to Sulina on the Black Sea (3500 km). The amount of goods transported on the Danube increased to
about 100 million tons in 1987. In 1999, transport on
the river was made difficult by the NATO bombing of 3 bridges in Serbia. The clearance
of the debris was finished in 2002. See also the Danube-Black Sea Canal.
The Danube is mentioned in the title of a famous waltz by Austrian composer Johann Strauss, An der schönen, blauen
Donau (On the Beautiful Blue Danube).
Geology
Although the headwaters of the Danube are relatively small today, geologically, the Danube is much older than the Rhine, with which its catchment area competes in today's southern Germany. This has a few
interesting geological complications. Since the Rhine is the only river rising in the Alps
mountains which flows north towards the North Sea, an invisible line divides
large parts of southern Germany, which is sometimes referred to as the European Watershed.
However, before the last ice age in the Pleistocene, the Rhine started at the southwestern tip of the Black Forest, while the waters from the Alps that
today feed the Rhine were carried east by the so-called Urdonau (original Danube). Parts of this ancient river's bed,
which was much larger than today's Danube, can still be seen in (now waterless) canyons in today's landscape of the Swabian Alb. After the Upper Rhine Valley had been
eroded, most waters from the Alps changed their direction and began feeding the Rhine. Today's upper Danube is but a meek
reflection of the ancient one.
Since the Swabian Alb is largely shaped of porous limestone, and since the
Rhine's level is much lower compared to the Danube, today, subsurface rivers carry much water from the Danube to the Rhine. On
many days in the summer, when the Danube carries little water, it completely oozes away noisily into these underground channels
at two locations in the Swabian Alp, which are referred to as the Donauversickerung (Danube Sink). Most of this water
resurfaces only 12 km south at the Aachtopf, Germany's most yielding wellspring
with an average production of 8,000 liters per second, north of Lake
Constance -- thus feeding the Rhine. The European Water Divide thus in fact only for those waters that pass beyond this
point, and only during the days of the year where the Danube carries enough water in the first place.
Since this enormous amount of underground water erodes much of its surrounding limestone, it is estimated that the Danube
upper course will one day disappear entirely in favor of the Rhine, an event called stream capturing.
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