1000 Lakes
Finland is mainly bounded by gulfs of the Baltic Sea. The Baltic Sea with its gulfs is the world's largest area of brackish water. The Baltic Sea is connected with the North Sea by narrow shallow Starits of Denamrk and the Kattegat. The surface layers flow towards the North Sea but the bottom layers into the Baltic Sea. The amount of water flowing out of the Baltic Sea is greater thatn the amount coming in.
The Bothnian Bay, the shallowest of the sea areas forms the northern tip of the Gulf of Bothnia. The Bothnian Bay and the Sea of Bothnia are separated by the shallow Quark, full of islands, which restrict the flow of water between the two. The Sea of Åland is in fact a sound and it is the deepest sea area in Finland (301 m). Between the Sea of Åland and south-western Finland is the broad labyrinthine Archipelageo Sea, in which Åland is the largest island. Finland is in the south bound by the Gulf of Finland, its maximum depth is 123 meters. The Finnish coast is characterized by an huge amount of islands.
The number of lakes larger than 1 ha is estimated to be around 56000. The total shoreline length of the lakes is 130 000 km. The total length of all rivers is estimated to be around 20 000 km. Ympäristöministeriö, 2001)
Largest lake in Finland is Suur-Saima and largest river is Vuoksi. Saimaa is a labyrinthine watercourse whose waters flow slowly from north to south and finally through its outflow channel, the Vuoksi, southeast over the Russian border into Ladoga which is Europe’s largest lake. In places, there is more shoreline here per unit of area than anywhere else in the world, the total length being nearly 15.000 km with 14.000 islands. In Saimaa you can find the Saimaa Ringed Seal, read more about it in the chapter about Nature heritage.
Take a look at pictures of Saimaa in Virtual Finland.
Eutrofication had during the last 30 years changed many waterbodies. Above you can see the same spot taken in 1970-ies and in end of 1990-ies.
About one tenth of Finland is covered by lakes and rivers. The amount of lakes and ponds have been calculated til 187 888 couple. The great majority of lakes are smaller than 1 km² (99%). This makes the zone areas between lakes and land very important for biodiversity. Different kind of lakes have been developed on different kind of ground soils: lakes on rocks, clay, sand and bogs. This difference is seen in the color of the water and their nurtient content. Lakes in southern part of Finland are usually nutrient rich with a large amount of vegetation. Lakes with sand beaches are found in eastern part of Finland and nutrient poor lakes are in Lapland.
The lakes in Finland are very shallow. Humans has also impacted on this by lowering the water level or totally drained several lakes. Sometimes this has resulted in very shallow and good lakes for water birds. The Finnish water law has made a rule for what is a river in Finland. A water body is called a river if one can force the river in the low season of water with a rowing boat (excluded rapids and rocky parts of the river).
Different kinds of mosses are found in lakes. Around rapids are usually found a lot of animals such like water butterflies (Tricoptera), have usually a lot of dragonflies (Odonata).Clean and fast running waters are identified by salamon fishes. Finnish lakes are important for many birds. Kuikka (Gavia arctica), laulujoutsen (Cygnus cygnus), selkälokki (Larus fuscus) ja kaakkuri (Gavia stellata) are speices that have suffered a decreas from human activities. The very endangeroud kiljuhanhi (Anser erythropus) is dependent on the mountain lakes and their surroundings in Lapland for breeding.
The largest problems for lakes in Finland is their eutrophication, especially there are problems with nigrogen and phosporus. The eutropication results in flowering of algaes, muddy color of water, oxygen disappearment and changes in species. Usually there is a loss in biodiversity. Another problem is the acidity of lakes which leds to a lower pH level. The acidity comes from the use of fossile fuels. The sthrength of Finnish lakes to take acidity is low as there is little lime in our rocks. Many lakes are humus rich and in that way naturally acid. At the bottom of such lakes aluminium is dissolved and other poisoned compounds. Most sensitive to acidity is salamon and roach fish.