The Arendal watercourse system extends across ten municipalities in Telemark and Aust-Agder counties. The water runs from Urdevatn and Bordsæ lakes via the larger Nisser and Fyresvatn lakes from the upper part of Telemark, before joining in Nidelva river and flowing into the sea at Arendal.
Arendal watercourse system covers a large area of lakes and rivers spread across ten municipalities in Telemark and Aust-Agder counties. The catchment area is over 4,000 square kilometres in size. The upper part of Arendal watercourse system comprises the lakes Urdevatn, Bordsæ, Nisser, Fyresvatn, Vråvatn, Nesvatn and Birtevatn and their tributaries. Finndøl, which is among the larger rivers, runs into Fyresvatn from Fyresdalsheiene. The rivers Nisserelva and Fyreselva then merge to form Nidelva, which flows out to the sea at Arendal. The watercourse system has a total length of over 200 km.
Skagerak Kraft has ownership shares in five power plants and one pumping station in the upper parts of the Arendal watercourse system. The pumping station is used to pump water from Rolleivstadvatn lake to Nape Power Plant.
The company Arendals Fossekompani was the first to acquire fall rights in the Arendal watercourse system in the 1890s. This was initially done with resale in mind, but the company developed the Bøylefoss waterfall itself in 1914 in order to supply power to the industrial community Eydehavn. Arendal’s local plant owners' association regulates most of the watercourse.
*The figures refer to plants where Skagerak Kraft holds an ownership interest.