Mjøsa

Mjøsa is the largest lake in Norway and the fourth deepest in Norway and Europe. It is located in the southern part of Norway, about north of the city of Oslo. Its main tributary is the river Gudbrandsdalslågen flowing in from the north; the only distributary is the river Vorma in the south. Inflows would theoretically need 5.6 years to fill the lake. With an average depth of about , most of the lake's volume is under sea level. The average outflow of the lake (measured from 1931 to 1982) is which is about . Mjøsa contains about of water compared to the in the lake Røssvatnet, the second largest lake by volume in Norway.

With a surface elevation of about , the depth of Mjøsa means that the deepest part of the basin is located approximately below sea level. This is lower than the deepest point of the sea inlet of Kattegat and the lower than the vast majority of Skagerrak off Norway's south coast. Mjøsa retains a larger average depth than both the North Sea and Baltic Sea respectively.