Vättern, Sweden
Lake Vättern, the second largest lake in Sweden and the sixth largest in Europe, is a remarkable fresh water body located in south-central Sweden. It is distinguished by its long, finger-shaped structure and its significant depth, reaching 128 meters at its deepest point. Despite being approximately one-third the surface area of Lake Vänern, Sweden’s largest lake, Vättern contains nearly half its water volume, demonstrating its profound depth.
Geographic and Hydrological Aspects
Spanning an area of about 1,912 square kilometers, Lake Vättern has a drainage basin of approximately 4,503 square kilometers. Its catchment area is more than double its surface area, indicating the extensive network of rivers and small lakes that contribute to its water volume. The lake is drained by Motala ström and has a surface elevation of 88 meters. Vättern’s perimeter stretches about 642 kilometers, encircling a diverse and scenic landscape.
Geological Formation
Vättern’s formation is attributed to tectonic activities dating back 700 to 800 million years ago in the Neoproterozoic era, making it a graben or a rift valley. The lake basin is partially filled with sedimentary rocks from the Visingsö Group of the same era, including conglomerates, sandstones, arkoses, and carbonates. The area’s geology also reveals a history of multiple glaciations, with the current lake form taking shape around 10,000 years ago after the last glacial period.
Biodiversity and Ecosystem
The lake hosts a variety of phytoplankton and zooplankton, along with a diverse benthos community comprising crustaceans, oligochaetes, dipterans, and bivalves. It is also home to several fish species, including the unique Vättern char, genetically similar to char species in nearby Lake Sommen and Lake Ladoga in Russia. The lake’s biological diversity is a testament to its rich ecological system.
Local and Environmental Significance
Situated within the provinces of Västergötland, Närke, Östergötland, and Småland, Lake Vättern is an important environmental and cultural landmark. Towns such as Vadstena, Jönköping, Hjo, Askersund, Åmmeberg, and Karlsborg are situated along its shores, benefiting from the lake’s resources and beauty. The island of Visingsö, located on the lake, adds to its scenic allure.