Thematic Maps of the Danube River Basin - ICPDR

2. Climate, Morphology and Hydrological Network
Both the geography and the management of the Danube River Basin are dominated by the natural
hierarchy of the Danube‘s hydrological network. Map 1 showing the Geomorphological Regions
and Map 2 presenting, as a result of the PRP Transboundary Workshops, the Sub-river Basins
reflect and respect this natural order. A detail description of each of the 15 Sub-river basins is given
in chapter 4.
2.1. Geomorphological Regions
The geography of the Danube river basin is very diverse. It includes high mountain chains, large
plains, sand dunes, large forested or marshy wetlands and, very specifically, the karst and the delta.
Similarly, climate and precipitation vary significantly; and they continuously form the basin’s
landscapes.
Generally, the Danube basin is dominated by a continental climate (central and eastern regions).
Only the western parts of the upper basin in Germany are influenced by the Atlantic climate and
the south-west of the basin (ex-Yugoslavian countries) by mediterranean climate. The Alps in the
west, the Dinaric-Balkan mountain chains in the south and the Carpathian mountain bow in the
eastern center are distinctive morphological and climatic regions and barriers.
These mountain chains receive the highest annual precipitation (1,000-3,200 mm per year) while
the inner and outer basins (Vienna basin, Pannonian basin, Romanian and Prut low plains), the
uplands of the Czech Morava and the delta region are very dry (350-600 mm per year). The rivers
with their water and moisture from the wet mountains help to balance evapotranspiration deficits,
typical for the Pannonian plain and the delta, in the dry lowlands. 50 to 70 days of annual snowfall
are recorded at high elevations in the Alps and in the Carpathians, while the plains have just 1-3
days/year of snowfall.
In terms of geomorphology and annual precipitation, 45 regions in the Danube basin can be
distinguished, as presented in map 1 (“Geographical Indicators”).
After the source of the Danube in the wet Black Forest, rainfall gradually increases from the west
to the east, along the Swabian & Frankonian Middle Mountains (average precipitation 600 – 700
mm/year), the Bavarian Forest & Austrian Mühlviertel (over 1,000 mm). There are each 4 prealpine
and alpine regions, with top rainfalls reaching more than 2,000 mm/year at the Arlberg and
the Kitzbühel and Julian Alps. Downstream the Wachau canyon (Bohemian mountains), the
Danube enters the Vienna basin which is, together with the Moravian hills and lowlands, the driest
area (below 600 mm/yr) of the Upper Danube.
The middle part or ”heart” of the Danube Basin is a circle of mountain chains around the huge
Pannonian plain in the center. It is composed of six regions including parts of Austria, Slovakia,
Hungary, Romania, Croatia and Yugoslavia. This inner basin is filled with Miocene marine
sediments, tertiary clays and sands as well as with pleistocene fluvio-glacial and loess deposits.
This results in little variation in the orography (hilly lands and the Danube and Tisza low plains)
and in precipitation (500-750 mm/year).
The Carpathian mountains in the northern and the central-eastern parts of the Danube basin receive
varying rainfall from 750 mm in the foothills to over 1,500 mm in the ridges, and have quite cold
winters (average temperature in January –8 to –10° C). The ridges of the Tatra, the Wood
Carpathians and the Southern Carpathians receive highest precipitation (over 2,000 mm/year
around the highest peaks at over 2,500 m). The Transilvanian tableland is a dry upland (500-700
mm) in between the moist Apuseni mountains (over 1,000 mm) in the west and the Eastern and the
Southern Carpathians (upper reaches of Mures and Olt rivers).