Central European in broader sense comprises high mountains of the Alpine Mountains and the Carpathian Mountains systems as well as mountainous ranges of medium elevation (between about 1000 and 2000 m a.s.l.), e.g. those belonging to the Bohemian massive, still prevailingly of mountainous character. Both types of mountains act as ”water towers”. Their high elevation brings about high precipitation and low evaporation, and the resulting surplus of water balance feeds large European rivers and other important water sources. Beside the mountains, large areas of Central Europe are occupied by highlands or peneplains of lower altitude (say, between 400 and 800 m) in which the surplus of annual water balance is less noticeable.