The new Pouttu fishway enables migratory fish to bypass the dam
A new fishway has just been completed next to the Pouttu regulation dam on the Lapuanjoki River. The project was carried out in collaboration with the Centre for Economic Development, Transport and the Environment (ELY Centre) of South Ostrobothnia, Kone-Kovera Oy, and Pipelife. The construction of the fishway was a technically demanding process, but the result exceeded expectations. Migratory fish can now pass smoothly upstream past the dam.
The Pouttu regulation dam, originally built in 1991, is located about three kilometers downstream from the center of Lapua.
“The dam keeps the water level stable, prevents shoreline erosion, and enables various recreational activities in the area,” explains Pekka Hyytiäinen, water resources specialist at the ELY Centre, who oversaw the fishway construction project.
The design and construction of the fishway were carried out jointly by the ELY Centre, civil engineering contractor Kone-Kovera Oy, and Pipelife, which supplied the necessary culvert pipes. The fishway was constructed using a 1600 mm diameter spiral-welded pipe.
“Pipelife was chosen as the supplier due to their design expertise and deep understanding of suitable pipe materials and implementation methods. Together, we found good compromises and solutions,” says Jarkko Yli-Kojola from Kone-Kovera Oy.
“The fishway consists of four sections of spiral-welded pipe, with a total length of about 40 meters. Plastic lamellas are installed inside the pipe at five-meter intervals to hold it in place, and various sizes of stone material have been added to replicate natural flow conditions. In addition, three light shafts help create an even more natural environment inside the pipe,” explains Joni Vihanta, Product Manager at Pipelife.
A technically demanding project successfully completed
Building the fishway was challenging due to the soft soil at the riverside construction site.
“We used sheet piling and dug down to depths of four to five meters – in some areas, even deeper. Now we can say the pipe is in place and water is flowing,” Yli-Kojola says with satisfaction.
During construction, the site experienced significant flooding followed by a two-meter drop in water levels. Despite this, the slopes of the fishway channel remained intact, confirming the durability of the build.
“The water flows smoothly, and according to fisheries experts, everything looks good. We already spotted bream and perch near the outlet – the fish are finding their way in,” Yli-Kojola smiles shortly after the opening.
A replicable model for future sites
The end result is something everyone involved can be proud of.
“Building the fishway was essential to allow migratory fish to continue their journey upstream. In my opinion, the outcome is excellent. The setting is beautiful – a river flowing through the flat plains with thousands of cubic meters of water passing every minute. The fishway has created a stunning new channel. It’s been a great project to be part of,” says Vihanta.
“It actually turned out better than we expected. The pipe structure seems very promising, and we hope it becomes a model that can be replicated at other sites as well,” Hyytiäinen concludes.