Lake Stechlin with its large number of bights was formed by deep melting of dead ice blocks and erosion of melt water channels after the Weichselian stage of the last glaciation. It is situated in the outwash plain immediately to the south of the terminal moraine of the Furstenberger Staffel. Formations of gravel and sand deposits reaching heights up to 84.5 m above the sea level and approaching the shores are towards the northeast of the lake.

Lake Stechlin has an area of 4.3 km2, a maximum depth of 68 m, and is stratified in summer with small hypolimnetic oxygen depletion. Towards the west and southwest, a sand plain follows at heights of 70-80 m above the sea level bordered on the east by a ground moraine. Before 1750, surface in- or effluents were virtually absent. The natural real surface catchment area amounts to 12.4 km2 of which 80% are covered by forests. The actual sub-surf ace catchment area amounts 26.0 km2. The actual water level is 59.7 m above the sea level. Before 1750, it was 60.7 m.

The lake is locally cut deeply into its environs with considerably steep shores on the northwest and northeast sides of the north bay. The Fenchelberg, the highest point (84.5 m a.s.l.) of the Lake Stechlin area, is situated immediately on its northeast shore.

The lake is divided in four basins or bays: the north basin with the maximum depth of the whole lake (68 m); the relatively shallow central basin, 59 m deep; the west basin influenced directly by the cooling water circuit, 41 m deep and separated from the south basin (35 m) by a nearly 1.2 km long peninsula stretching from west to east. During the stagnation phases the hypolimnion of the different basins is not changeable mutually. The volumes of the four basins are: west basin 19,000,000 m3, north basin 37,000,000 m3, south basin 13,000,000 m3, central basin 28,000,000 m3.

The shore of Like Stechlin is bounded by a more or less closed large zone of mixed forests mainly consisting of pines, beeches, willows and alders. Allochthonous input of organic matter - mostly leaves, twigs, pollen and fruits from the surrounding trees - are potentially significant for material balance and production in the lake. Open land borders on the shores up to 4.8% only and the trophic level of the lake water is still oligotrophic. Now the input of cooling water circuit from a nuclear power plant and the man-made surface run-in of water from Lake Dagow influence mainly the ecosystem (1).