It is the southernmost breeding site for many northern and alpine bird species. Human activities include nature conservation, fishing, livestock grazing, recreation, and tourism. More than 100 archaeological sites dating to the iron-age are present. Ramsar site no. 803. A system of oxbow lakes, bays dotted with islets, small dams and mires.
Vegetation includes flooded marshland, seasonally flooded deciduous forests, mud and sandflats.
An important inland locality for migrating and wintering waterbirds and waders in southern Norway. Several species of waterbirds feed, and numerous nationally rare species breed at the site. Human activities include nature conservation, recreation, fishing and boating. There is a bird observatory at the site. The largest inland delta in Norway includes low islands and land giving way to Lake yeren.