Kolsnaren-Viren FVOF covers the lakes Kolsnaren (area: 1147 ha) and Viren (1190 ha), which are located in western Södermanland and are part of the Nyköpingsån water system.

The association was formed in 1987 after several appeals and various legal challenges, the formation was confirmed by the Swedish Supreme Court in 1990. The water owners' fishing rights with all kinds of gear remain unchanged, all fixed fishing gear must, however, be guarded and marked with the fishing right number. This fishing, however, takes place to a very limited extent.

We have sea charts where we have indicated bottom depths, based on soundings carried out.