The Danube can be used by international cargo shipping from Sulina located at the end of the middle delta arm at the Black Sea in Romania (river km 0), right through to the end of the German Danube waterway near Kelheim (river km 2,414.72)  

The Belgrade Convention of 18th August 1848 applies to the main route between Kelheim and Sulina, and guarantees freedom of navigation on the Danube for merchant ships flying the flags of the riparian states.  
In accordance with the Danube Commission, international freight shipping is free to navigate the Danube waterways which, according to physical-geographical characteristics, are divided into three main sections. These nautical characteristics are shown in the table below:

Nautical characteristics

Navigable sections of the Danube

Upper Danube(Kelheim - Gönyü)

Middle Danube (Gönyü - Turnu-Severin)

Lower Danube(Turnu-Severin - Sulina)

Section length

624 km

860 km

931 km

River km

2,414.72 to 1,791.33

1,791.33 to 931.00

from 931.00 to 0.00

Avg. Gradient per km

around 37 cm

around 8 cm

around 4 cm

Height of drop

around 232 m

around 68 m

around 39 m

Speed of ships


9 - 13 km/h

9 - 13 km/h

11 - 15 km/h

Speed of ships


16 - 18 km/h

18 - 20 km/h

18 - 20 km/h


There are characteristical differences in the distribution of water flow between the three sections of the Danube over the course of the year. These are dependent not only on geological and climatic conditions, but also on the river’s tributaries. The highest water levels generally occur from May to August in the region of the Upper Danube, with the lowest water occurring between October and March. The low-water periods in the Middle and Lower Danube are the months of August to October, with high waters occurring between the months of April and May.

source ViaDonau

Additional information about navigability at the following links:

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