Nedre Røssåga power plant

Nedre Røssåga power plant uses the height of fall between Lake Stormyrbassenget and the village of Korgen, while Øvre Røssåga power plant uses the height of fall between Lake Røssvatnet and Lake Stormyrbassenget.

Lake Røssvatnet has a reservoir capacity of 2.35 billion cubic metres, and is Norway's second-largest lake measured by surface area.

The development of the Røssåga power plants involves the municipalities of Hemnes, Hattfjelldal and Grane. The development, which occurred in the 1950s and 1960s, was historically linked to operating the ironworks in Mo i Rana and the aluminium plant in Mosjøen.

A major modernisation and upgrading programme was completed at the Røssåga power plants in 2016.

The modernisation and expansion started in the spring of 2012 and is among the largest hydropower projects in Norway in the 2000s. The total capacity at Nedre Røssåga has been increased from 250 MW to 350 MW. Total annual production increased by around 200 GWh to about 2 150 GWh, equivalent to the consumption of more than 100,000 Norwegian households. For the first time in Norway in decades, some sections of the new waterways were cut using a tunnel boring machine.

The project had a positive environmental impact. In parallel with the increase in power production, conditions were improved for salmon and sea trout in the Røssåga River. Among other things, the river regained a section that supports salmon migration, accounting for 30 per cent of the spawning stock in the entire Røssåga watercourse.

Architect Hans Grinde drew the plans for and participated in the planning of both original Røssåga power plants. Parts of Nedre Røssåga power plant will be preserved as they are, in accordance with a conservation plan drawn up by Statkraft in cooperation with the Norwegian Directorate for Cultural Heritage.