It is the largest lake in the municipality of Oslo, serving as its primary drinking water supply.

The Hammeren Hydroelectric Power Station exploits the fall from Skjærsjøen to Maridalsvannet.

The shores of the lake and substantial areas of woods and fields around it are owned by the city of Oslo to protect the water supply.

Some farms are still operated under city supervision, but others were closed down in the mid-20th century; their remains are marked by historical signs.

They can be reached by a short walk from the Kjelsås trolley, bus, or train stations.