Near these rapids in the River Atna in Norway, settlements from the Stone Age were discovered on the banks. The Atna has formed a few small lakes in its catchment area, only the Atnsjøen is considerably larger. The average depth of this lake is 35m and 80m at its deepest point. About 1,500 tons of erosion material are supplied annually by the river, most of which is deposited as a delta at the lake's inlet. The lake is relatively poor in nutrients, yet there it contains a lot of trout and salmon trout, as well as grayling further downstream .