The Danube flows through the territories of the following countries:
Germany, Austria, Slovak Republic, Hungary, Croatia, Serbia and Montenegro, Bulgaria, Romania, Moldova and Ukraine
Also , the Danube flows through four main eco-regions:
- Central Highlands
- Hungarian Lowlands
- Carpathians
- Pontic Province
There were identified ten section types with characteristic habitat and morphology :
- Section Type 1: Upper course of the Danube rkm 2786: confluence of Brigach and Breg – rkm 2581: Neu Ulm
- Section Type 2: Western Alpine Foothills Danube rkm 2581: Neu Ulm – rkm 2225: Passau
- Section Type 3: Eastern Alpine Foothills Danube rkm 2225: Passau – rkm 2001: Krems
- Section Type 4: Lower Alpine Foothills Danube rkm 2001: Krems – rkm 1789.5: Gönyu˝ / Klizˇská Nemá
- Section Type 5: Hungarian Danube Bend rkm 1789.5: Gönyu˝ / Klizˇ ská Nemá – rkm 1497: Baja
- Section Type 6: Pannonian Plain Danube rkm 1497: Baja – rkm 1075: Bazias
- Section Type 7: Iron Gate Danube rkm 1075: Bazias – rkm 943: Turnu Severin
- Section Type 8: Western Pontic Danube rkm 943: Turnu Severin – rkm 375.5: Chiciu/Silistra
- Section Type 9: Eastern Wallachian Danube rkm 375.5: Chiciu/Silistra – rkm 100: Isaccea
- Section Type 10: Danube Delta* rkm 100: Isaccea – rkm 20 on Chilia arm, rkm 19 on Sulina arm and rkm 7 on Sf. Gheorghe arm* Within this section the Danube divides into the three main branches of the Danube Delta.Each arm also has transitional waters with the following limits: Chilia arm: rkm 20 – 0, Sulina arm: rkm 19 – 0, Sf. Georghe arm: rkm 7 – 0.
