Removing the dam of stopped Jyllinkoski hydropower plant on the Karvianjoki River, Finland
River Karvianjoki in the Satakunta region is a 110 km long river flowing to the Baltic Sea, mostly through an agricultural landscape. In its upper reaches, the river has remained relatively natural, excluding the areas around the Jyllinkoski and Vatajankoski rapids, which have long been harnessed for hydropower. The headwaters of the River Karvianjoki include Natura 2000 areas due to their whitewater rapids in a natural state, magnificent riparian forests, grove-like woodlands, and pistons.
The river habitat holds many biological, geological, and recreational values. Several of its smaller tributaries support original brown trout populations. The endangered freshwater pearl mussel (Margaritifera margaritifera) inhabits the waters near the hydropower dams, although with limited chances for natural reproduction due to the poor state of salmonid populations and unsatisfactory water quality. The dams are altering the flow regime and acting as migration barriers for aquatic fauna.
| Project status | Completed |
|---|---|
| Project type | Dam removal: demolition |
| Country | Finland |
| River | Karvianjoki |
| Removal date | July - September 2024 |
| Km opened | 110 km |
| Focal species | Brown trout, freshwater pearl mussel |
| Organisation | WWF Finland |
| Website | Vatajankoski Project |
The removal of the Jyllinkoski hydropower dam is restoring the headwaters of the River Karvianjoki to free flow, strengthening the natural lifecycles of many riverine species by replacing the dam reservoir, dam, and the dry riverbed below the dam with a roaring whitewater habitat. This dam removal also brings the River Karvianjoki one step closer to reconnecting with the sea, which could eventually lead to the return of migratory species such as Atlantic salmon, anadromous whitefish, lamprey, and eel. Restoring Jyllinkoski also provides additional motivation to push for the removal of the Vatajankoski hydropower dam, located downstream of Jyllinkoski.
The removal of the 4.8m high Jyllinkoski hydropower dam will create a 250m long whitewater rapid with a total descent of 11 metres. Taking into account other existing barriers, the removal will open up over 30 km of the river’s main stem downstream of the dam, and approximately 80 km when tributaries are included. Upstream, the dam removal will similarly open around 30 km of the river’s main stem and over 100 km of running water habitats, including tributaries.
The hydropower plant has been decommissioned, and its 4.8 m high dam removed. This removal has created a 250 m long whitewater rapid with a total descent of 11 metres. The rapid, which was destroyed in the 1950s due to damming, has now been restored to a free-flowing state. This restoration supports the reproduction of endangered salmonid species in the river, alongside a wide range of other biodiversity that depends on whitewater rapids for their natural habitat.
Strengthening the viability of the brown trout population in the River Karvianjoki is crucial for the critically endangered freshwater pearl mussel, as its larvae rely on brown trout as their intermediate host.
The newly opened area for free fish migration now extends up to 100 km, including smaller but significant tributaries, or 30 km when measured along the main stretches of the river system.
The removal of the dam is expected to improve the river’s water quality, as the restored rapid increases oxygen concentration downstream. This is becoming an increasingly important factor as climate change raises water temperatures, which has already led to fish deaths in Finland.
Additionally, the removal of the dam will significantly enhance the recreational value and scenic beauty of the region.
The project was officially completed in December 2024.
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