Case study:Environmental design Mandalsvassdraget

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Location: 58° 14' 40.24" N, 7° 30' 50.40" E
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Project overview

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Status Complete
Project web site
Themes Fisheries, Hydropower, Hydromorphology
Country Norway
Main contact forename Aleksander
Main contact surname Andersen
Main contact user ID
Contact organisation Agder Energi
Contact organisation web site http://https://www.ae.no/
Partner organisations Norwegian Institute for Nature Research (NINA), Sintef, Norce Research, Skandinavisk Naturovervåking
Parent multi-site project
This is a parent project
encompassing the following
projects
No
Removal of weirs in the Mandalselva river in connection to efforts to make earlier unproductive zones accessible as spawning and growing areas for salmon. Foto: Agder Energi

Project summary

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Mandalselva is regulated for hydropower production since 1947 and this has impacted the conditions for Atlantic salmon in this river. The project "Miljødesign Mandalselva" used the concept of Environmental Design as described in the "Handbook for environmental design in regulated salmon river (Forseth and Harby 2013) and was accompanied by thorough research efforts in order to study which measures would be suitable to improve the conditions for salmon and at the same time to take into account hydropower production. This researcj was led by the Norwegian Institute for Nature Research (NINA) and conducted in cooperation with SINTEF Energy, Norce Research and Skandinavisk Naturovervåking. It included i.a. a trade-off analysis between the production of Atlantic salmon and the production of hydropower by examining the use of several physical mitigation measures and changes in release of water. Local stakeholders and public natural resource management were involved by means of a counceling group. As a result, nine weirs in the river were removed and further habitat improving measures were put in place (e.g. installation of gravel habitat).

Monitoring surveys and results

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Monitoring surveys and results are expected to be published soon.

Lessons learnt

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expected soon...


Image gallery


Project area Environmental Design Mandlaselva Barton et al. 2020.jpg
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Catchment and subcatchment



Site

Name
WFD water body codes 022-649-R
WFD (national) typology
WFD water body name Mandalselva
Pre-project morphology Varies in character from low to high gradient within short stretches;
Reference morphology
Desired post project morphology
Heavily modified water body No
National/international site designation
Local/regional site designations
Protected species present Yes
Invasive species present No
Species of interest Atlantic salmon (Salmo salar)
Dominant hydrology The flow regime is characterized by frequent fluctuations in dicharge.
Dominant substrate Reaches alternating between material of glacio-fluvial and moraine sediments
River corridor land use Intensive agriculture (arable)
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) 8888 m³/s <br />88,000 l/s <br />
Average channel gradient category
Average channel gradient
Average unit stream power (W/m2)


Project background

Reach length directly affected (m)
Project started 01.10.2014
Works started
Works completed
Project completed
Total cost category 100 - 500 k€
Total cost (k€) 394394 k€ <br />394,000 € <br />
Benefit to cost ratio
Funding sources Agder Energi

Cost for project phases

Phase cost category cost exact (k€) Lead organisation Contact forename Contact surname
Investigation and design Norwegian Institute for Nature Research (NINA) Torbjørn Forseth
Stakeholder engagement and communication Agder Energi Alexander Andersen
Works and works supervision Agder Energi Alexander Andersen
Post-project management and maintenance Agder Energi Alexander Andersen
Monitoring Norwegian Institute for Nature Research (NINA) Torbjørn Forseth



Reasons for river restoration

Mitigation of a pressure Hydropower
Hydromorphology Quantity & dynamics of flow (minimum flow), Weirs, Substrate conditions
Biology Fish
Physico-chemical Nutrient concentrations
Other reasons for the project


Measures

Structural measures
Bank/bed modifications Removal of weirs (9 weirs), installation of gravel habitat, establishment of shelter in the substrate, sediment harrowing (using an excavator); introduction of larger stones in the riverbed, stream
Floodplain / River corridor Activation of sidearms
Planform / Channel pattern
Other
Non-structural measures
Management interventions Future increase of minimum discharge still under evaluation
Social measures (incl. engagement) Active involvement of local interests groups and land owners
Other


Monitoring

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

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://https://docplayer.me/33318388-Multi-kriterie-analyse-av-kompenserende-tiltak-for-regulerende-okosystemtjenester-ecomanage.html Presentation of research on multi-criteria analysis of different habitat improving measures for Mandalselva (CEDREN/EcoManage project), David N. Barton et al. 2015
http://https://www.sciencedirect.com/science/article/pii/S136481521831291X Article Barton et al. 2020 Multi-criteria decision analysis in Bayesian networks - Diagnosing ecosystem service trade-offs in a hydropower regulated river. Study conducted at Mandalselva

Supplementary Information

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