Regulating inland waters

The water levels and flows in many of Finland's inland waters are regulated with the help of dams, weirs or other structures connected to hydropower plants. A total of 220 water level regulation projects have been carried out in Finland, affecting around 300 lakes, which together account for about a third of the total area of lakes across the country.

Most of this water level regulation work was done between the 1950s and the 1970s in order to reduce flooding, to produce hydropower, to facilitate water transportation, and to improve the water supply. More recently, attitudes towards inland waters have changed as issues like nature conservation and recreational values have become more important.

Water regulation projects aim to adjust water levels and flows to improve their suitability for water users, and to meet various goals related to the state of the environment in general. Meeting these often conflicting requirements can be a difficult task.

Water regulation projects are normally carried out by either energy companies or the regional environment centres. Where projects have considerable impacts over wide areas, the relevant water regulation permit may remain in the possession of the State. Permits must be obtained for all water regulation projects from the environmental permit authorities, according to the provisions of Finland's Water Act.