The Danube is Europe's second-longest river. It starts in the Black Forest in Germany as two smaller rivers—the Brigach and the Breg—which join at Donaueschingen, and it is from here that it is known as the Danube, flowing generally eastwards for a distance of some 2,850 km (1,770 mi), passing through several Central and Eastern European capitals, before emptying into the Black Sea via the Danube Delta in Romania.
^The Leitha flows into the Mosoni-Duna, a branch of the Danube
^The Rába flows into the Mosoni-Duna, a branch of the Danube
^The Sió is 121 km long. As it flows out from the Balaton lake, measured from the source of the lake's longest tributary, the river Zala, it is 360 long.
^The Sava is 945 km long, but as it originates from two shorter rivers, Sava Dolinka and Sava Bohinjka, with the longer headwater of Sava Dolinka it measures 990 km.
^The Velika Morava is created by the confluence of the Južna Morava and the Zapadna Morava. The Velika Morava proper is 185 km long, but also counting its longer branch, Zapadna Morava, it is 493 km long. The most distant water source in the Morava watershed is the source of the river Ibar, the longest tributary of the Zapadna Morava, which gives the Ibar-Zapadna Morava-Velika Morava river system a length of 550 km.
^The Rusenski Lom is formed by the confluence of the Beli Lom and the Cherni Lom. The Rusenski Lom proper is about 45 km long, but counting its longer branch, the Beli Lom, it is 196.9 km.
References
Mala Prosvetina Enciklopedija, Third edition (1985); Prosveta-Beograd; ISBN86-07-00001-2
Jovan Đ. Marković (1990): Enciklopedijski geografski leksikon Jugoslavije; Svjetlost-Sarajevo; ISBN86-01-02651-6
Atlas svijeta, Fifth edition (1974); Jugoslavenski leksikografski zavod-Zagreb;
Donaukommission - Die Donau von Kelheim bis Sulina [1]
