Begna is a river in Buskerud and Oppland counties in Norway. It is formed by the merging of the rivers Otrøelva and Ylja above Lake Vangsmjøsa. It is also the name of the village of Begna located by the river.
The Begna runs from the mountainous area of Filefjell in the southern part of the Jotunheimen range, through the traditional district of Valdres into the lakes Vangsmjøsi, Slidrefjord, Strondafjorden and Aurdalsfjorden, down Begnadalen to Nes in Ådal and Lake Sperillen via the Ådal River and southward to the city of Hønefoss in Buskerud. There the Begna joins the Randselva river before discharges into Lake Tyrifjorden. The Begna is 213 km long and has a high point of about 1850 meters. The Begna drains a watershed of 4875 km² and is the primary river in this watershed. The Norwegian writer, Mikkjel Fønhus lived much of his life and located most of his novels along the Begna in Oppland.
Association for Begna watershed Control (Foreningen til Bægnavassdragets Regulering) is an association under the provisions of the Norwegian Watercourse Act. The association's purpose is to protect members' common interests with regard to the use of water from the Begna basin used for power generation. Power company operate 20 power plants on the Begna and Drammen River below Tyrifjord. The association is responsible for maintenance and operation of dams, gates and stations along the Begna waterway. The plants are mainly located in Valdres.[1]