The Numedal watercourse system comprises Numedalslågen with tributaries. One of the biggest tributaries is Uvdalelva river, which flows into Numedalslågen at Rødberg. The source of the system is on the Hardangervidda plateau in Hordaland. From there, the water flows through Numedalen valley via Kongsberg before flowing into the sea at Larvik. The catchment area is around 5,500 square kilometres.

Skagerak Kraft is the majority owner of two power plants using water from the Uvdalselva river, Uvdal I and Uvdal II. Furthest up the watercourse system, several lakes are diverted into Sønstevann, which is the only regulation reservoir for Uvdal I and has a fantastic dam. The dam was rehabilitated in 2015 and has won an award for its characteristic and aesthetically attractive design. The water from Uvdal I runs into the Fønnebøfjord, which is Uvdal II’s intake reservoir.

Further south at Lampeland, the Gjuva/Vrenga watercourse flows in from the west and Skagerak Kraft has two power plants located here. South of Kongsberg is Skollenborg Power Plant, of which Skagerak Kraft is part owner.

*The figures refer to plants where Skagerak Kraft holds an ownership interest