O přehradě Oulujarvi

Oulujärvi is the fifth-largest lake in Finland and the largest in Ostrobothnia, sitting at the heart of the Oulujoki river system in North Ostrobothnia. Covering around 900 square kilometres, the lake was brought under regulation in 1951 as part of Finland's post-war industrialisation drive, which harnessed the Oulujoki's significant hydropower potential. Today the river is one of Finland's most intensively regulated waterways, with a series of seven power stations between Oulujärvi and the Gulf of Bothnia. The reservoir holds approximately 2,500 million cubic metres of water and plays a dual role in flood control and energy production. Regulation has dramatically altered the natural flow regime of the Oulujoki, and the original migratory Atlantic salmon population was lost. Ongoing restoration and stocking programmes aim to re-establish fish populations in some tributaries. The lake's shores support several towns, and Kajaani, the regional centre of Kainuu, sits at the eastern tip of the lake system.