Danube Vilayet, Ottoman Balkans (1860s)

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 , passing through or bordering Austria, Slovakia, Hungary, Croatia, Serbia, Romania, Bulgaria, Moldova, and Ukraine before draining into the Black Sea. Its drainage basin extends into nine more countries. The largest cities on the river are Vienna, Budapest, Belgrade and Bratislava, all of which are the capitals of their respective countries; the Danube passes through four capital cities, more than any other river in the world. Five more capital cities lie in the Danube's basin: Bucharest, Sofia, Zagreb, Ljubljana and Sarajevo. The fourth-largest city in its basin is Munich, the capital of Bavaria, standing on the Isar River.

The Danube is the second-longest river in Europe, after the Volga in Russia. It flows through much of Central and Southeastern Europe, from the Black Forest into the Black Sea. Its longest headstream Breg rises in Furtwangen im Schwarzwald, while the river carries its name from its source confluence in Donaueschingen onwards.

Since ancient times, the Danube has been a traditional trade route in Europe. Today, of its total length are navigable. The Danube is linked to the North Sea via the Rhine–Main–Danube Canal, connecting the Danube at Kelheim with the Main at Bamberg. The river is also an important source of hydropower and drinking water. Many European borders, especially in the Balkans, are also drawn by the Danube's stream. There are more countries along its flow than on any other river (10; the Nile is second with 9).

The Danube river basin is home to fish species such as pike, zander, huchen, Wels catfish, burbot and tench. It is also home to a large diversity of carp and sturgeon, as well as salmon and trout. A few species of euryhaline fish, such as European seabass, mullet, and eel, inhabit the Danube Delta and the lower portion of the river.

Names and etymology

Other names

The river was known to the ancient Greeks as the () a borrowing from a Daco-Thracian name meaning 'strong, swift', from a root possibly also encountered in the ancient name of the Dniester ( in Latin, in Greek) and akin to Iranic 'swift' and Sanskrit () 'swift', from the PIE , 'to flow'. In the Middle Ages, the Greek was borrowed into Italian as and into Turkic languages as ; the latter was further borrowed into Romanian as a regionalism ().

The Thraco- Phrygian name was , "the bringer of luck".

The Middle Mongolian name for the Danube was transliterated as ''Tho-na'' in 1829 by Jean-Pierre Abel-Rémusat.

The modern languages spoken in the Danube basin all use names related to :
german: link=no, Donau ();
ro, Dunărea (; via German);
;
;
;
cz, Dunaj ();
sk, Dunaj ();
pl, Dunaj ();
hu, Duna ();
sl, Donava ();
sh-Latn-Cyrl, separator=" / ", Dunav, Дунав ();
bg, Дунав, Dunav ();
russian: Дунай, Dunaj ();
uk, Дунай, Dunaj ();
gr, Δούναβης ();
it, Danubio ();
es, Danubio; ();
;
rm, Danubi;
sq, Tunë, .

Etymology

''Danube'' is an Old European river name derived from the Celtic ' danu' or ' don'Triad 35. Bromwich, ''Trioedd Ynys Prydein'', pp. 280–285. (both Celtic gods), which itself derived from the Proto-Indo-European . Other European river names from the same root include the Dunaj, Dzvina/ Daugava, Don, Donets, Dnieper, Dniestr, Dysna and Tana/Deatnu. In Rigvedic Sanskrit, ''dānu'' (दनु) means "fluid, dewdrop" and ''dānuja (दनु-ज)'' means "born from ''dānu''" or "born from dew-drops". In Avestan, the same word means "river". The Finnish word for Danube is , which is most likely derived from the name of the river in German, . Its Sámi name means "Great River". It is possible that in Scythian as in Avestan was a generic word for "river": ''Dnieper'' and ''Dniestr'', from ''Danapris'' and ''Danastius'', are presumed to continue Scythian "far river" and "near river", respectively..

In Latin, the Danube was variously known as , , or ''Hister''. The Latin name is masculine, as are all its Slavic names, except Slovene (the name of the Rhine is also masculine in Latin, most of the Slavic languages, as well as in German). The German ( Early Modern German , , Middle High German ) is feminine, as it has been re-interpreted as containing the suffix '' -ouwe'' "wetland".

Romanian differs from other surrounding languages in designating the river with a feminine term, (). This form was not inherited from Latin, although Romanian is a Romance language. To explain the loss of the Latin name, scholars who suppose that Romanian developed near the large river propose that the Romanian name descends from a hypothetical Thracian . The Proto-Indo-European root of this presumed name is related to the Iranic word ""/"", while the supposed suffix is encountered in the ancient name of the Ialomița River, ''Naparis'', and in the unidentified ''Miliare'' river mentioned by Jordanes in his Getica. Gábor Vékony says that this hypothesis is not plausible, because the Greeks borrowed the ''Istros'' form from the native Thracians. He proposes that the Romanian name is a loanword from a Turkic language ( Cuman or Pecheneg).

Geography

Classified as an international waterway, it originates in the town of Donaueschingen, in the Black Forest of Germany, at the confluence of the rivers Brigach and Breg. The Danube then flows southeast for about , passing through four capital cities ( Vienna, Bratislava, Budapest, and Belgrade) before emptying into the Black Sea via the Danube Delta in Romania and Ukraine.

Once a long-standing frontier of the Roman Empire, the river passes through or touches the borders of 10 countries: Romania (29.0% of basin area), Hungary (11.6%), Serbia (10.2%), Austria (10.0%), Germany (7.0%), Bulgaria (5.9%), Slovakia (5.9%), Croatia (4.4%), Ukraine (3.8%), and Moldova (1.6%). Its drainage basin extends into nine more (ten if Kosovo is included).

Drainage basin

In addition to the bordering countries (see above), the drainage basin includes parts of nine more countries: Bosnia and Herzegovina (4.6% of the basin area), the Czech Republic (2.9%), Slovenia (2.0%), Montenegro (0.9%), Switzerland (0.2%), Italy (<0.15%), Poland (<0.1%), North Macedonia (<0.1%) and Albania (<0.1%). The total drainage basin is in area, and is home to 83 million people. The highest point of the drainage basin is the summit of '' Piz Bernina'' at the Italy–Switzerland border, at . The Danube River Basin is divided into three main parts, separated by "gates" where the river is forced to cut through mountainous sections:
* Upper Basin, from the headwaters to the Devín Gate.
* Middle Basin, usually called the Pannonian basin or Carpathian Basin, between the Devín Gate and the Iron Gates. It includes the Hungarian plains Kisalföld and Alföld.
* Lower Basin, from the Iron Gates to the river mouth, including the Danube Delta.

Discharge

Mean annual discharge on the hydrological stations (period from 2000 to 2020); 1 - Reni, Isaccea; 2 - Silistra; 3 - Pristol; 4 - Batina, Bezdan; 5 - Nagymaros, Szob; 6 - Bratislava, Wolfsthal; 7 - Untergriesbach

Multiannual average, minimum and maximum discharge (water period from 1876 to 2010)

Simulated water and suspended sediment results from climate-driven decadal study (with STD through specific decade)

Tributaries

The land drained by the Danube extends into many other countries. Many Danubian tributaries are important rivers in their own right, navigable by barges and other shallow-draught boats. From its source to its outlet into the Black Sea, its main tributaries are (as they enter):

File:Donaueschingen Donauzusammenfluss 20080714.jpg, The Danube's source confluence in Donaueschingen: the ''Donauzusammenfluss'', the confluence of Breg and Brigach.
File:Дунайський біосферний заповідник 2.JPG, 0 km, Danube Delta, Ukraine
File:Danube Delta ESA23450088.jpeg, Where the Danube Meets the Black Sea (European Space Agency Sentinel-2 image).
File:The Danube Spills into the Black Sea.jpg, The Danube discharges into the Black Sea (the upper body of water in the image).

Cities and towns

The Danube flows through many cities, including four national capitals (shown below in bold), more than any other river in the world. Ordered from the source to the mouth they are:
*
**Donaueschingen in the State of Baden-Württemberg – rivers Brigach and Breg join to form the Danube
**Möhringen an der Donau in Baden-Württemberg
**Tuttlingen in Baden-Württemberg
** Sigmaringen in Baden-Württemberg
** Riedlingen in Baden-Württemberg
** Munderkingen in Baden-Württemberg
** Ehingen in Baden-Württemberg
** Ulm in Baden-Württemberg
** Neu-Ulm in Bavaria
** Günzburg in Bavaria
** Dillingen an der Donau in Bavaria
** Donauwörth in Bavaria
** Neuburg an der Donau in Bavaria
** Ingolstadt in Bavaria
** Kelheim in Bavaria
**Regensburg in Bavaria
**Straubing in Bavaria
** Deggendorf in Bavaria
**Passau in Bavaria

*
** Linz, capital of Upper Austria
** Krems in Lower Austria
**Tulln in Lower Austria
** Vienna – capital of Austria and the most populous city on the Danube, where the Danube floodplain is called the '' Lobau'', though the ''Innere Stadt'' is situated away from the main flow of the Danube (it is bounded by the Donaukanal – 'Danube canal').
*

**Bratislava – capital of Slovakia
** Komárno
**Štúrovo
*

**Mosonmagyaróvár
** Győr
** Komárom
** Esztergom
** Visegrád – This section of the river is also called Danube Bend.
** Vác
**Szentendre
** Göd
**Dunakeszi
** Budapest – capital of Hungary, the largest city and the largest agglomeration on Danube (about 3,300,000 people).
** Szigetszentmiklós
** Százhalombatta
** Ráckeve
**Adony
** Dunaújváros
**Dunaföldvár
** Paks
** Kalocsa
** Baja
** Mohács
*
** Vukovar
** Ilok
*

** Apatin
**Bačka Palanka
**Čerević
** Futog
** Veternik
** Novi Sad – regional capital of Vojvodina
** Sremski Karlovci
** Zemun
**Belgrade – capital of Serbia
**Pančevo
** Smederevo
** Kovin
** Veliko Gradište
** Golubac
** Donji Milanovac
** Kladovo
*

** Vidin
** Lom
**Kozloduy
**Oryahovo
** Nikopol
**Belene
**Svishtov
**Ruse
** Tutrakan
**Silistra
*

**Moldova Nouă
** Orșova
**Drobeta-Turnu Severin
** Calafat
** Bechet
**Dăbuleni
**Corabia
** Turnu Măgurele
**Zimnicea
**Giurgiu
** Oltenița
** Călărași
**Fetești
**Cernavodă
**Hârșova
**Brăila – limit of the maritime sector of the Danube
**Galați – largest port on the Danube
** Isaccea
** Tulcea
** Sulina – last city through which it flows
*
**Giurgiulești
*
** Reni
** Izmail
** Kiliya
**Vylkove

Islands

*Ada Kaleh Island
*Ostrovul Mare, Gogoșu
*Balta Ialomiței
*Belene Island
* Csepel Island
* Donauinsel
*Great Brăila Island
* Great War Island
*Island of Mohács
*Kozloduy Island
* Margaret Island
*Ostrovo (Kostolac)
*Ostrovul Ciocănești
*Ostrovul Mare, Islaz
*Ribarsko Ostrvo, Novi Sad
*Island of Šarengrad
*Szigetköz
*Island of Szentendre
*Vardim Island
*Island of Vukovar
*Žitný ostrov

Sectioning

*Upper Section: From spring to Devín Gate, at the border of Austria and Slovakia. Danube remains a characteristic mountain river until Passau, with average bottom gradient 0.0012% (12 ppm), from Passau to Devín Gate the gradient lessens to 0.0006% (6 ppm).
*Middle Section: From Devín Gate to Iron Gate, at the border of Serbia and Romania. The riverbed widens and the average bottom gradient becomes only 0.00006% (0.6 ppm).
*Lower Section: From Iron Gate to Sulina, with average gradient as little as 0.00003% (0.3 ppm).

Modern navigation

The Danube is navigable by ocean ships from the Black Sea to Brăila in Romania (the maritime river sector), and further on by river ships to Kelheim, Bavaria, Germany; smaller craft can navigate further upstream to Ulm, Württemberg, Germany. About 60 of its tributaries are also navigable.

Since the completion of the German Rhine–Main–Danube Canal in 1992, the river has been part of a trans-European waterway from Rotterdam on the North Sea to Sulina on the Black Sea, a distance of .
In 1994 the Danube was declared one of ten Pan-European transport corridors, routes in Central and Eastern Europe that required major investment over the following ten to fifteen years. 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 three bridges in Serbia during the Kosovo War. Clearance of the resulting debris was completed in 2002, and a temporary pontoon bridge that hampered navigation was removed in 2005.

At the Iron Gate, the Danube flows through a gorge that forms part of the boundary between Serbia and Romania; it contains the Iron Gate I Hydroelectric Power Station dam, followed at about downstream (outside the gorge) by the Iron Gate II Hydroelectric Power Station. On 13 April 2006, a record peak discharge at Iron Gate Dam reached .

There are three artificial waterways built on the Danube: the Danube-Tisa-Danube Canal (DTD) in the Banat and Bačka regions ( Vojvodina, northern province of Serbia); the Danube-Black Sea Canal, between Cernavodă and Constanța (Romania) finished in 1984, shortens the distance to the Black Sea by ; the Rhine–Main–Danube Canal is about , finished in 1992, linking the North Sea to the Black Sea. A Danube-Aegean canal has been proposed.

Piracy

In 2010–12, shipping companies, especially from Ukraine, claimed that their vessels suffered from "regular pirate attacks" on the Serbian and the Romanian stretches of the Danube. However, the transgressions may not be considered acts of piracy, as defined according to the United Nations Convention on the Law of the Sea, but rather instances of "river robbery".

On the other hand, media reports say the crews on transport ships often steal and sell their own cargo and then blame the plundering on "pirates", and the alleged attacks are not piracy but small-time contraband theft along the river.

Danube Delta

The Danube Delta ( ro, Delta Dunării ; uk, Дельта Дунаю, translit=Del'ta Dunayu) is the largest river delta in the European Union. The greater part of the Danube Delta lies in Romania (Tulcea county), while its northern part, on the left bank of the Chilia arm, is situated in Ukraine (Odessa Oblast). The approximate surface is , of which are in Romania. If one includes the lagoons of Razim-Sinoe ( of which water surface), which are located south of the delta proper, but are related to it geologically and ecologically (their combined territory is part of the World Heritage Site), the total area of the Danube Delta reaches .

The Danube Delta is also the best-preserved river delta in Europe, a UNESCO World Heritage Site (since 1991) and a Ramsar Site