Statkraft has been testing various water flow regimes in the Suldalslågen river and monitoring their effects since 1990. At the same time, Norway’s most extensive fluvial salmon monitoring programme has been carried out. The Suldalslågen’s river management regime aims to safeguard the needs of the salmon while allowing the river’s hydropower potential to be exploited. Statkraft’s proposed new regime aims to provide a better fish habitat and more favourable temperature conditions than the previous one.

          
          The Suldalsvatnet lake, looking towards Suldalsosen.

New river management regime for the Suldalslågen river – more salmon and more power 
Statkraft has applied to the Norwegian Water Resources and Energy Directorate (NVE) for permission to implement a new river management regime on the Suldalslågen river. The regime also takes into account fish migration, the opportunities for fishing and other users’ interests. 

Statkraft has regulated the flow of water in the Suldalslågen river in accordance with various trial regimes since 1990. The results from Norway’s most extensive fluvial salmon monitoring programme provide the basis for decisions concerning the new river management regime. The proposed new regime is scientifically sound and will safeguard the river’s salmon population and the interests of other users.

The application has been drawn up on the basis of over one hundred scientific reports and many years of research and analysis. The research results show that it is possible to safeguard environmental assets and provide salmon populations with good living conditions in a river that is used for hydropower production.

The starting point for the design of the new regime has been the water flow requirement of the river’s salmon populations. Particular emphasis was placed on habitat and water temperature.

Juvenile fish depend on habitats which provide plenty of cover. Flushing flood events, low and stable winter water flows and medium-high summer water flows are all management measures which improve fish habitats. The survival and growth of juvenile fish is affected by the summer water temperature. A lower water flow rate will result in a higher water temperature in the Suldalslågen river, and the supply of water to the Suldalslågen can be controlled by the operation of Hylen Power Plant.

The new regime will also allow the river’s hydropower potential to be exploited more effectively.

The NVE has opened a three-month public consultation period on Statkraft’s application.
 

Suldalslågen 
The Suldalslågen river is the most water-abundant river in the west of Norway. The river is 22 km in length and runs from the Suldalsvatnet lake (68 m above sea level) to Sandsfjorden. The most common fish species in the river are salmon and trout.

The Suldalslågen is characterised as a winter-warm, summer-cold, oligotrophic river. The Suldalslågen is also famous for having a high proportion of large fish among its salmon population. When it debated Statkraft’s hydropower licence application, the Norwegian Storting (parliament) emphasised the importance of protecting the salmon population. The needs of the salmon have therefore been the focus of all the research and monitoring that has taken place on the river.
  

Ulla-Førreverkene hydropower scheme – various water flow regimes 
In 1974 Statskraftverkene was granted a licence to build the Ulla-Førreverkene hydropower scheme, which was completed in the 1980s. The scheme is one of Norway’s largest, and is one of two which affect the Suldalslågen’s water flow.

In 1988 Statkraft SF applied for permission to test the impact of various water flow regimes in the Suldalslågen, and has implemented several such regimes since 1990. By trying out various regimes and monitoring their impact, the aim was to arrive at a water flow regime which took account of the salmon populations’ needs while allowing the river’s hydropower potential to be exploited.  

During the years in which trial regimes were implemented, Norway’s most extensive fluvial salmon monitoring programme has been carried out. We now have a solid basis for determining a new river management regime. Monitoring of the trial regimes from 1998-2000 and 2001-2003 was carried out in close consultation with the regulatory authorities and research institutions.