This river was harnessed for production of hydropower in the past, but has now been rehabilitated back towards its natural state. This restoration is the result of comparing the benefits for nature and humans with the relative loss of energy production.
Opening the power plant dam removes the barrier and enables access to spawning areas for migratory fish
The old smalli-scale hydropower plant has been turned into a museum. The amount of electricity produced was too small compared to the relative harm caused to the river ecosystems. The old hydropower dam has been opened and now serves as a bridge. There is a café in the old power plant building. The former water intake pipe, located between the dam and the power plant, is now a part of the open air museum.
The water is once again continuously flowing in the old natural river channel, not just when there is too much water for safe generation of hydropower. Trout spawn in the newly inhabitable natural reach which has a suitable channel gradient and benthic substrate.
The bypass divides the water to accommodate the needs of both the powerplant and the river-inhabiting organisms
The lower hydropower plant is still in operation and generates electricity. A natural bypass enables fish and other river-inhabiting organisms to pass the power plant dam.
The natural bypass was constructed with an excavator. The design of the bypass is gently sloping and serpentine. Stones, gravel and other benthic material have been added to the bypass, giving the stream a natural flow diversity of fast flowing sections, whirpools and slow pool-like areas. The natural bypass looks no different than a natural brook. Although water is a valuable resource for the powerplant, the bypass has adequate water flow throughout the year.
The replacement of the regulation dam with a partial dam opens up the river source
Due to the presence of the partial dam, the water levels in the source lake remain at a level that is acceptable for the lake shore inhabitants. The flood regime of the river downstream from the lake has returned to its natural state.
Restoration creates spawning areas
Other rapid areas in the river have also been restored. The previously cleared and straightened river channel is filled with rocks and gravel to provide protection and to create spawning grounds to the river inhabiting organisms. Constructions made out of wood and stone materials have been built in the river, to steer and diversify the flow.
In 2008 the Stream Restoration Society (Virtavesien hoitoyhdistys ry.) built a natural bypass on the site of an old mechanical grain mill on the river of Vihtijoki, in Haimoo. The now landscaped, natural looking stream is a gateway and a natural breeding habitat for trout. Vihtijoki is a part of the Karjaanjoki catchment area and flows into lake Hiidenvesi in Uusimaa county, Finland. Picture: Markus Penttinen