The Göta Canal built in the 19th century forms a waterway that runs to Vättern wholly rising when proceeding eastward, and then a navigable river linking the east coast with Vänern.

The southeastern part of the Vänern is a depression that appears to have come into being by erosion of Paleozoic-aged sedimentary rock during the Quaternary glaciation that reached to the area.

[8] Because the southern and eastern shores are parts where the Sub-Cambrian peneplain gently tilts towards the north and west, respectively, the lake is rather shallow at these places.

[8] The modern lake was formed after the Quaternary glaciation about 10,000 years ago; when the ice melted, the entire width of Sweden was covered in water, creating a strait between Kattegat and the Gulf of Bothnia.

[9] As a result, there are still species remaining from the ice age not normally encountered in freshwater lakes, such as the amphipod Monoporeia affinis.

[15] Geographically, it is situated on the border between the Swedish regions of Götaland and Svealand, divided between several Swedish provinces: The western body of water is known as the Dalbosjön, with its main part belonging to Dalsland; the eastern body is known as Värmlandsjön, its northern part belonging to Värmland and the southern to Västergötland.

The economic opportunities Vänern offers are illustrated by the surrounding towns, which have supported themselves for centuries by fishing and allowing easy transportation to other cities or west by Göta älv to the sea of Kattegat.

This directly includes: Karlstad (chartered in 1584), Kristinehamn (1642), Mariestad (1583), Lidköping (1446) Vänersborg (1644), Åmål (1643), Säffle (1951), and indirectly Trollhättan (1916).

Sport fishing in Vänern is free and unregulated, both from the shore and from boats (with some restrictions, e.g. a maximum of three salmon or trout per person per day).

The most important large fish in the lake are brown trout (Salmo trutta) and zander (Sander lucioperca).