Lakes are usually bodies of standing freshwater, though they may also be brackish, i.e. slightly salty. They are characterised by the physical features of the lake basin, such as lake area and water depth, as well as the characteristics of the catchment area, such as size and topography.
Lakes in Europe
There are more than 500 000 natural lakes larger than 0.01 km2 (1 ha) in Europe. About 80 % to 90 % of these are small with a surface area of between 0.01 and 0.1 km2, whereas around 16 000 have a surface area exceeding 1 km2. Three quarters of the lakes are located in Norway, Sweden, Finland and the Karelo-Kola part of Russia.
Twenty four European lakes have a surface area larger than 400 km2. The largest, Lake Ladoga (1), covers an area of 17 670 km2 (Map 1) and is located in the north-western part of Russia with the second largest lake in Europe, Lake Onega (2). Both lakes are considerably larger than other European lakes and reservoirs. Nevertheless, they only rank as the 18th and 22nd largest in the World. The third largest European freshwater body is the 6 450 km2 long Kuybyshevskoye reservoir (3) on the Volga. A further 19 natural lakes larger than 400 km2 are found in Sweden, Finland, Estonia and the north-western part of Russia as well as three in central Europe — Lake Balaton (19), Lac Léman (20) and Bodensee/Lake Constance (21) (Map 1).
Lakes & reservoirs in Europe
The formation of Europe’s lakes
Many natural European lakes appeared 10 000 to 15 000 years ago; being formed or reshaped by the last glacial period, the Weichsel. The ice sheet covered all of northern Europe. However, in central and southern Europe ice sheets only stretched as far as mountain ranges. As a rule, the regions comprising many natural lakes were affected by the Weichsel ice. For example, Norway, Sweden, Finland and the Karelo-Kola part of Russia have numerous lakes that account for approximately 5 % to 10 % of their national surface area. Large numbers of lakes were also created in other countries around the Baltic Sea, as well as in Iceland, Ireland and the northern and western parts of the United Kingdom. In central Europe, most natural lakes lie in mountain regions. Lakes at high altitude are relatively small whereas those in valleys are larger, for example Lac Léman, Bodensee, Lago di Garda, Lago di Como and Lago Maggiore in the Alps and Lake Prespa and Lake Ohrid in the Dinarian Alps. Two exceptions are the large lakes lying on the Hungarian Plain — Lake Balaton and Lake Neusiedler.
European countries which were only partially affected by the glaciation period (Portugal, Spain, France, Belgium, southern England, central Germany, the Czech Republic, the Slovak Republic and the central European part of Russia) boast few natural lakes. In these areas man-made lakes, such as reservoirs and ponds, are often more common than natural lakes. Many river valleys have been dammed to create reservoirs; a large number of which have been built in mountain ranges for hydroelectric purposes. In several countries, for example the Netherlands, Germany, France, Czech Republic and Slovakia, numerous small, artificial lakes have been created by other human activities such as peat and sand quarrying, and for use as fish ponds.