Project: Hafslund Tolga hydropower plant
Location: Tolga, Glomma River, Norway
Cost: 1,8 million EUR
Dates: 2018-2021
Objectives: Establishment of safe fish migration routes past a new hydropower plant.
Measures undertaken: Installed a slanted trash rack with a 15mm light opening to prevent fish swimming into the turbines. Installed two diverters with a total of 2m3/s flow capacity at top of the trash rack to guide fish safely past the intake to below the dam. Up and downstream migration was secured through two fish passages. The main passage is a vertical slot fish ladder with a 5m3/s flow capacity, providing migration opportunities for all present fish species. Additionally, there is a more natural passage with a 3m3/s. At large water flows, migration is also possible over the entire length of
the intake dam. Through minimum flow requirements (12 m3/s in summer and 7 m3/s in winter) water is secured in the fish passages all year round.
Results: Local stakeholders satisfied with the process and solutions. The effects of the measures are monitored through a survey programme. There has been no negative impact on fish populations indicated thus far. Positive fish trends indicated by increases sale of fishing licences.
Challenges:
- The licence application for the plant was met with notable opposition from fishing associations, local stakeholders, and environmental authorities. The objections were
largely related to expected negative impacts on fish and fishing. In order to obtain a licence it was crucial to include solutions maintaining safe upstream and downstream fish migrations; and - Exact monitoring of fish migration in the fish passages will require invasive methods limiting the migration.
Success factors:
- Use of best available competence to develop best possible solutions;
- Implementing environmental solutions in the early project stages, ensuring through planning and beneficial technical solutions;
- No invasive fish counting implemented, but rather a programme monitoring fish populations and fishing activity in the influence area; and
- Obtaining public acceptance by implementing effective measures for fish migration.
Images copyright: Hafslund
