Kurunkoski hydropower dam removal, Finland

Introduction

Kurunkoski is a harnessed rapid situated in River Torsanjoki, the main tributary of River Hiitolanjoki, in the southeast part of Finland.

Project context and opportunity

Endangered migratory fishes from Lake Ladoga are currently able to reach Kurunkoski, but their migration halts at the hydropower dam. Removing the dam and replacing it with a small bottom sill upstream will allow unrestricted movement of wildlife, water and sediment in the river. It will also enable the restoration of a white water rapid in River Torsanjoki, creating valuable habitat for fish reproduction and other freshwater flora and fauna. Water quality in the Torsanjoki and in upstream lakes and streams is categorised as good or excellent.

Project aims

The goal of the project is to restore the natural reproduction of salmonid fish in Kurunkoski and to open a free migration route to the water bodies upstream of the current dam. The catchment area above Kurunkoski Dam covers 228 km². The stream network that will be turned into free-flowing river stretches from 63 km (main stems only) to 175 km (including smaller tributaries).

Project achievements

The hydro power plant has been stopped and its dam – standing 3 metres high and 17 metres wide – has been removed. As part of the restoration works, this has given rise to a 200-metre whitewater rapid with a total descent of 4 metres. This will serve as an important reproductive habitat for the local brown trout, as well as for the migratory salmonid populations from Lake Ladoka: namely the land-locked salmon (Salmo salar, m. sebago) and brown trout (Salmo trutta, m. lacustris). The land-locked salmon of the Hiitolanjoki river system represents the only naturally reproducing population of its kind remaining in Finland, and is critically endangered.

Whitewater rapids have become an increasingly rare habitat type across southern Finland, owing to a long history of river damming and dredging. As a result, a wide range of riverine biodiversity – particularly the invertebrates on which juvenile salmonids depend – has also come under serious threat. Dam removals such as this one are a vital tool in the fight against the loss of nature.