Lake Vanern is the third largest lake located entirely in Europe after lakes Ladoga and Onega, both located in Russia. It is the largest lake in Sweden and in the European Union.
Geography and Formation
Lake Vanern was formed after the last Ice Age nearly 10 000 years ago. When the ice melted, the entire width of the country was covered in water, forming a strait between the Gulf of Bothnia and Kattegat. Because of isostatic rebound the lake became pursed off, still containing species from the last Ice Age, an occurrence that is rarely found in freshwater lakes. The lake can be found in a region with Archaean rocks, but the deposits in the drainage area are mainly made up of moraines, which are generally poor in nutrients.
Lake Vanern is located in the southwest of Sweden, in the provinces of Vastergotland, Dalsland and Varmland. It is surrounded by rocky, wooded shores, except in the south, where the shores are low, forming ideal farming places. The encircling towns and cities, such as Karlstad, Lidkoping, Kristinehamn, Amal, Saffle and Mariestad serve important industries like tanneries, iron works and even paper mills.
The western part of the lake, referred to as Hindensrev, is a long glacial moraine part of the middle Swedish ice marginal zone. From the lake you can dmire Mount Kinnekulle, Vastergotland’s highest plateau, as well as Mount Lugnasberget, one of the smallest plateaus in the country.
The Djuro Archipelago surrounds the island of Djuro in the middle of the lake, and it has officially been declared a national park. Large areas of contiguous forest can be found on the archipelago.
The Kinnekulle ridge is a popular tourist attraction near the southeastern shore of the lake, offering the best view of Vanern. The most popular activities in the region are kayaking, golfing at the 18-holes Mariestad course, boat tripping on the lake and visiting the Falkangen Handicraft Village.
Lake Vanern is fed by a number of rivers, of which its largest contributor is the Klaralven, with 35% of the lake’s income coming from it. The inflow originates from the greatest catchment in the country, which encloses more than 10% of the total surface area of Sweden. It enters the lake near the city of Karlstad, on the northern shore. Other tributaries are the Gullspangsalven, Byalven and Norsalven. Precipitation makes up 25% of the lake’s inflow. The lake drains towards the sothwest into the Kattegat Strait through the Gota River, a major source of hydroelectric power.
Lake Vanern consists of two sub-basins, which are separated by a shallow area. The western body of water is known as Dalbosjon, and its main part belongs to Dalsland, whilst the eastern body is called Varmlandsjon. The northern area belongs to Varmland, and the south to Vastergotland. Lake Vanern was regulated in the middle of the 1930s for hydroelectric purposes. Today all major rivers which discharge into it are regulated.
The lake has a residence time of approximately 10 years. Vanern is large enough to be affected by the rotation of the earth, and thus its induced currents may be influenced by the Coriolis force, which leads to a counterclockwise water circulation. If the lake is stratified, this circulation induces thermocline to deform from its horizontal level. Thermal stratification happens each year, mainly during the summer months. During spring a special kind of horizontal stratification occurs in the shallow areas.
Studies of Vanern’s water quality are conducted annually. A 2002 report showed no decrease in the lake’s water quality, only a slight decrease in its visibility due to the increase of algae. The accumulation of nitrogen presented a problem between 1970 and the 1990s, but has since been regulated and is at a steady level in the present. Only a few bays still have issues with eutrophication and are overgrown with algae and plant plankton.
Birds and Fish
The Lake Vanern area is an important area for birds, the most common sightings being of terns and gulls. Cormorants vanished in the 19th century but have since returned and are now flourishing. Their comeback has caused an increase in sea eagle populations, since they feed on cormorants. Some rare species of birds can also be seen around the lake, such as the black-throated diver, the turnstone with a dozen nests around the lake, and the caspain tern, which only has a dozen specimens left in the region.
The most iconic fish in the lake is the Vanern salmon, which, unlike other species which make it to adulthood in the ocean, are known to never enter the sea during their whole lifecycles. There are two distinct subgroups of this particular fish: the first is named after the lake’s eastern tributary, the Gullspangsalven, and is called the Gullspang salmon. The second is called the Klaralv salmon, and it spawns in Klaralven. The two subgroups are related to the Baltic Sea salmon, which has developen in Lake Vanern for more than 9 000 years. The world’s largest salmon, which weighed more than 20 kilograms was caught in Lake Vanern. There are also three other salmon-like fish living in the lake.
One of the most common species is the smelt, which dominates the eastern Dalbosjon with an average of 2600 smelt found in a hectare. The second most common fish is the vendace, with 200-300 fish per hectare. These fish populations change between the years, depending on the lake’s water level, temperature and the water quality. Other important fish are the trout and zander, and the most important small fish are the stickleback and 5 distinct species of whitefish.
Salmon and trout can be caught all year round in Lake Vanern, while the best time to fish for pike is from March to May, and September to November. The ideal time for ice fishing for pike is between January and March. Perch can be most surely caught between July and October, while rainbow trouts can be encountered throughout the year.
Because of the abundance of many different fish species in Lake Vanern, locals and government officials enforce fishing preservation projects. The main threats which fish species are facing are mainly due to water cultivation in the lake’s tributaries, pollution and M74 syndrome, a kind of reproduction disorder found in salmon. Sport fishing is free and unregulated, and can be done both from the shore and from boats. For commercial fishing, however, one must purchase a permit.
Legends and Historic Facts
There is a story told by a 13th century Icelandic mythographer called Snorri Sturlson in his work, the “Prose Edda”, in which he explains the origin of Lake Malaren. Some believe that he is actually speaking of Lake Vanern. The legend has it, that the Swedish king Gylfi promised Gefjun, a woman, that she would get as much land as four oxen could plough in a day and in a night. Gefjun scammed the ruler, and used oxen from giants, uprooting the land and dragging it to the sea, contributing to the creation of the island of Zealand. The inlets in the lake correspond to the headlands of Zealand, which is actually true of Vanern, and not of Lake Malaren.
The Battle of the Ice of Lake Vanern is a 6th century battle which has been recorded in the Norse sagas. A Viking ship has been found at the bottom of Lake Vanern on the 6th of May, 2009.