Lahnasenkoski Hydropower Dam, River Hiitolanjoki, Finland

One step closer to a free-flowing River Hiitolanjoki

Video 1. Lahnasenkoski, Kangaskoski and Ritakoski dams in River Hiitolanjoki, Rautjärvi, South Karelia, southeast Finland

Barrier removal process
Lahnasenkoski Dam and power plant were located upstream Kangaskoski Dam and were the second barrier along River Hiitolanjoki when moving upstream (latitude: 61.419007, longitude: 29.361142). The dam was 8 meters high (Figure 1), and the power plant had the capacity of 0.8 MW and generated 4500 MWh on average on an annual basis. The latter was designed by the engineer Axel Söderlund and built in 1911. It was the first hydroelectric power plant along River Hiitolanjoki and retained almost its entire original equipment till the end of the 20th century.

Figure 1. Lahnasenkoski Dam and power plant at River Hiitolanjoki, Rautjärvi, South Karelia, southeast Finland (photos by Hanna Ollikainen)

At the dawn of the new century, in 2001, the power plant was acquired by Vantaan Energy Oy and much of its equipment was upgraded. Pieces of the old equipment have been saved and are being exposed in a museum housed at the old power station. Both properties were acquired by The South Karelia Foundation for Recreation Area in 2017 from their owner, Vantaan Energia Oy, and the power plant stopped running on July 31, 2022. The preparatory works at the demolition site began also on the same month, before the decommission of the power plant (Figure 2).

Figure 2. Preparatory works in July 2022, before the demolition of Lahnasenkoski Dam in River Hiitolanjoki (photos by (up) Hanna Ollikainen and (down) Mikko Nikkinen)

The turbines were removed on August 15, 2022 (Figure 3) and the demolition of the dam followed soon after (Video 2; Figure 4). The dam was replaced by a bridge (Figure 5) and the rapids were restored during the months following the demolition (Video 3; Figure 6).

Figure 3. Removal of the turbines of Lahnasenkoski power plant in River Hiitolanjoki in August 2022 (photo by Mikko Nikkinen)

Video 2. Demolition of the Lahnasenkoski Dam in River Hiitolanjoki

“The demolition of the Lahnasenkoski Dam and the restoration project of the rapids was a great success – thanks to good engineering and skilled contractors! As was the first project in Kangaskoski in 2021. We are already enthusiastically preparing the last Hiitolanjoki dam removal that will start in Ritakoski in August.”

Hanna Ollikainen, CEO of South Karelian Foundation for Recreation Areas

Figure 4. Removal of the Lahnasenkoski Dam in River Hiitolanjoki in August 2022 (photos by (up) Hanna Ollikainen and (down) Mikko Nikkinen)

Figure 5. Bridge that replaced the Lahnasenkoski Dam in River Hiitolanjoki (photos by (up) Hanna Ollikainen and (down) Mikko Nikkinen)

Video 3. Markus Tapaninen at the removal site of Lahnasenkoski Dam in River Hiitolanjoki (interview by Niccolo Sala)

Figure 6. (Up) Restoration and (down) restored rapids after the demolition of Lahnasenkoski Dam in River Hiitolanjoki (photos by (up) Mikko Nikkinen and (down) Hanna Ollikainen)

Ecological and community benefits
Even during the demolition works of the Lahnasenkoski Dam, migrating salmon were spotted upstream the work site (Figure 7) evidencing how swiftly this stock can recover given the appropriate conditions of water flow and fish passage.

Figure 7. Salmon spotted at the removal site of the Lahnasenkoski Dam in River Hiitolanjoki (photo by Hanna Ollikainen)

The success of this project was celebrated on October 26 at the Rautjärvi City Hall. Local newspapers as well as the national Finnish television station YLE were present to this event. Representatives of local authorities and organizations involved in this project were also present and addressed to the public, including Hanna Ollinkainen (CEO of The South Karelia Foundation for Recreation Area) (Video 4), Visa Niittyniemi (director of Environment and Nature Resources in ELY center of Southeast Finland), Matti Vaittinen (project coordinator in NOUSU program in the Ministry of Agriculture and Forestry), Harri Anttila (Rautjärvi mayor) (Video 5), Sampsa Vilhunen (WWF Finland) and Finnish actor Jasper Pääkkönen.

Video 4. Hanna Ollinkainen, CEO of The South Karelia Foundation for Recreation Area, at Rautjärvi City Hall discussing the demolition of the Lahnasenkoski Dam in River Hiitolanjoki (interview by Niccolo Sala)

Video 5. Harri Anttila, mayor of Rautjärvi, discussing the demolition of the Lahnasenkoski Dam in River Hiitolanjoki (interview by Niccolo Sala)

Next steps
The demolition of the Ritakoski Dam will be executed in 2023 and this will be the last step of the Hiitolanjoki project. After its completion, Hiitolanjoki will be once more a free-flowing river with restored longitudinal connectivity. The restored rapids of Kangaskoski, Lahnasenkoski and Ritakoski will be reconnected with the already free-running rapids at Uudensillankoski, Rapukoski and Ali-Juvankoski, located further upstream.
The fish production of salmon and trout in the Finnish sections of River Hiitolanjoki following the completion of the three removals is estimated between 5000 and 11000 young fish on an annual basis. That would make River Hiitolanjoki the most important habitat of endangered landlocked salmon in Finland and would enable the development of recreational activities for local community and tourists (e.g., fishing tourism) in the area. A free-flowing River Hiitolanjoki, along with Ladoga Skerries National Park and Saimaa Geopark, will form a natural area with unique characteristics and potential not only in Finland, but also in Europe.

Before & After photo pair

The removal site at River Hiitolanjoki: (left) before and (right) after the removal operations of Lahnasenkoski Dam (photos by Mikko Nikkinen)

The removal site at River Hiitolanjoki: (left) before and (right) after the removal operations of Lahnasenkoski Dam (photos by Hanna Ollikainen)

Written by Foivos A. Mouchlianitis