Lake Vattern has an alternately lacustrine and marine postglacial history in the gothiglacial period (12,000-6,000 B. P.) and it passed through an icedammed stage, the Vattern Ice-Lake. Later on it formed a part of the Baltic Ice-Lake, dammed up by the retreating ice-cover. This lake was drained (12,000-6,000 B. P.) and Lake Vattern was converted into a bay of the Yoldia Sea (12,000-6.000 B. P.). Ultimately, the elevation of the landlevel caused Ancient Vattern to become isolated from the sea, but during the Ancylus Period it again established contact with the Baltic. The Baltic at that time was a freshwater lake-the Ancylus Lake. Finally, the Vattern basin was elevated above the surface of the Ancylus Lake and became thus definitely separated as Lake Vattern. This may have happened about 8,000 years ago (Stalberg, 1939).

The basin of Lake Vattern is boat-shaped and is easily affected by changes in wind and atmospheric pressure which results in development of standing waves of from 20 to 25 cm amplitude. Many severe gales occur in the lake due to its shape, which makes it especially sensitive to wind influence. The seiches give rise to strong currents affecting the sedimentation. The distribution of erosion, accumulation and transportational bottoms in Lake Vattern is reflected in the concentration of metals in the sediments. The distribution of these bottom types is also of great importance for the development of bottom fauna. The spawning places of the famous Vattern char (an endemic form of Salvelinus alpinus) is indeed totally dependent on the type of bottom.

The depth, the relatively large water volume, and the transparency of Lake Vattern make it a unique body of water. The ratio of drainage area/lake area is only 2.3, which suggests a low areal loading and hence an oligotrophic status. These properties together with its central position in southern Sweden makes it an extremely good water resource for communities and industries. The lake is also a great natural asset, famous for its beauty.

There are six large and sixteen smaller tributaries to the lake and many small brooks. Lake Vattern discharges into a system of lakes connected to the Baltic via a canal.