Difference between revisions of "Case study:Restoration of spawning grounds for trout in Bjornesfjorden (Hardangervidda)"

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{{Project overview
{{Project overview
|Themes=Habitat and biodiversity, Hydropower, Hydromorphology
|Themes=Environmental flows and water resources, Habitat and biodiversity, Hydropower, Hydromorphology
|Main contact forename=Nils Runar
|Main contact forename=Nils Runar

Revision as of 11:06, 4 December 2019

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Location: 60° 9' 0", 7° 46' 10"
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Project overview

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Status Complete
Project web site
Themes Environmental flows and water resources, Habitat and biodiversity, Hydropower, Hydromorphology
Country Norway
Main contact forename Nils Runar
Main contact surname Sporan
Main contact user ID
Contact organisation Statkraft AS
Contact organisation web site http://www.statkraft.no
Partner organisations Uni Reserch Miljø LFI, Numedals-Laugens Brugseierforening (NLB), The Norwegian Water Resources and Energy Directorate (NVE)
Parent multi-site project
This is a parent project
encompassing the following
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Project summary

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The Bjornesfjord was temporarily lowered in 1959 to provide water for hydroelectric powerplants (Noreverkene) in Norway. This resulted in permanent damage to several spawning grounds for the trout since the original spawning -substrate were removed. This meant that the bottom conditions of the affected spawning areas were dominated by more sandy masses and that the areas were no longer suitable for spawning. To compensate for the damage caused to the fish stock in connection with the lowering of water in the fjord, an order was issued for the release of trout. In the period 2002-2006, LFI Uni Miljø, in collaboration with NLB, Statkraft and NVE, carried out restorations of the spawning areas in the Bjornesfjord. The restoration was carried out by laying gravel on the outlet of Lågaros, in the Nøresundet and Meinsbusundet, i.e. areas that were adversely affected by the lowering of the fjord in 1959.

Subsequent surveys in 2007 and 2013 show that the measures worked as intended, with spawning found each year on the newly established spawning grounds. It is therefore concluded that the measures had led to the spawning conditions for the trout population is a step towards the natural state as was the situation before the lowering.

Monitoring surveys and results

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Lessons learnt

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The establishment of flow deflectors (ledebuner/strømsettere) and the laying of rocks, blocks and uprooted trees in areas with low hydromorphological variation, have great potential for the improvement of aquatic environment/habitats - in this example, increased fish production in the adjusted areas.

Higher densities of both “yearlings” and older juvenile fish were found in the habitat-adjusted areas than were found on the reference sites.

All the flow deflectors have led to a better spatial distribution of spawning opportunities for lake trout in the upper part of the Teigdal river.

It could have been advantageous to place several blocks and stones in the riverbed to increase the extent of the measures and thus the quality of the habitat in the sterile areas. An analysis of the total available area in the three habitat-adjusted areas shows that only 2% of this area had been adjusted. An increase will further strengthen the aquatic environment measures and lead to a higher fish production.

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Catchment and subcatchment


Name Bjornesfjorden
WFD water body codes 015-418-L (EU-ID:NO015-418-L)
WFD (national) typology LEH32113
WFD water body name Bjornesfjorden
Pre-project morphology
Reference morphology
Desired post project morphology
Heavily modified water body No
National/international site designation Norway - Nasjonalpark
Local/regional site designations National Park
Protected species present No
Invasive species present No
Species of interest Brown trout (Salmo trutta)
Dominant hydrology
Dominant substrate Cobble, Gravel
River corridor land use Natural open water
Average bankfull channel width category
Average bankfull channel width (m)
Average bankfull channel depth category
Average bankfull channel depth (m)
Mean discharge category
Mean annual discharge (m3/s)
Average channel gradient category
Average channel gradient
Average unit stream power (W/m2)

Project background

Reach length directly affected (m)
Project started 1999/01/01
Works started
Works completed
Project completed 2013/01/01
Total cost category
Total cost (k€)
Benefit to cost ratio
Funding sources Statkraft AS

Cost for project phases

Phase cost category cost exact (k€) Lead organisation Contact forename Contact surname
Investigation and design
Stakeholder engagement and communication
Works and works supervision
Post-project management and maintenance

Reasons for river restoration

Mitigation of a pressure Hydropower
Biology Fish
Other reasons for the project


Structural measures
Bank/bed modifications Creation of fish spawn nursing places, Introduction of spawning gravels
Floodplain / River corridor
Planform / Channel pattern
Non-structural measures
Management interventions
Social measures (incl. engagement)


Hydromorphological quality elements

Element When monitored Type of monitoring Control site used Result
Before measures After measures Qualitative Quantitative

Biological quality elements

Element When monitored Type of monitoring Control site used Result
Before measures After measures Qualitative Quantitative
Fish Yes Yes No No Yes Improvement
Invertebrates Yes Yes No No Yes No change

Physico-chemical quality elements

Element When monitored Type of monitoring Control site used Result
Before measures After measures Qualitative Quantitative

Any other monitoring, e.g. social, economic

Element When monitored Type of monitoring Control site used Result
Before measures After measures Qualitative Quantitative

Monitoring documents

Additional documents and videos

Additional links and references

Link Description
http://uni.no/media/manual upload/LFI 235.pdf Report
http://www.miljodirektoratet.no/globalassets/publikasjoner/m1051/m1051.pdf Measures Handbook for better physical aquatic environment

Supplementary Information

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