Case study:Dam removal at Grönkullen, River Rolfsån

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Location: 57° 40' 21.34" N, 12° 35' 56.72" E

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Project overview

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Status	Complete
Project web site
Themes	Fisheries, Habitat and biodiversity, Hydropower
Country	Sweden
Main contact forename	Andreas
Main contact surname	Bäckstrand
Main contact user ID	User:Arolam
Contact organisation	Länsstyrelsen västra Götalands län
Contact organisation web site	http://projektwebbar.lansstyrelsen.se/rolfsan/Sv/folj-atgardsarbetet/Pages/soran.aspx?keyword=gr%C3%B6nkullen
Partner organisations	Municipality of Bollebygds
Parent multi-site project	Case_study:Biologisk återställning i Rolfsåns vattensystem
This is a parent project encompassing the following projects	No

Grönkullen stream (photo. Maria Arola)

Project summary

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Grönkullen hydro power station is located in one of the upstream tributaries of River Rolfså, River Sörån. Restorations took place after the county administrative board wanted to make migration possible for lake dwelling brown trout in lake Lygnern. Because there is a chemical plant and a railway situated next to the river and there is possible consentrations of the chemical in the river investigations were accomplished to find out weather the dam removal has any affection to the stability conditions. Conclusion was that there would not be any significant affection of the dam removal to the stability or water levels of the river. Investigations were made in 2002-2004 and the municipality of Bollebygds bought the plant 2005 to be able to remove the dam.

Restoration was done in 2005. A new river was rebuilt upstream and downstream of the old dam, altogether along a 200 m strech. A small part of the old dam was saved as a memory. Stones and gravel were added to the river bank. Total cost of the restoration was about 5 million Swedish crones (ca. 500 000 euros).

Monitoring surveys and results

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Lessons learnt

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Catchment and subcatchment

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Catchment

River basin district	Skagerrak and Kattegat River basin
River basin	Rolfsån River Basin

Subcatchment

River name	River Rolfsån
Area category
Area (km2)
Maximum altitude category
Maximum altitude (m)
Dominant geology	Organic (i.e. Peat)
Ecoregion	Fenno-Scandian Shield
Dominant land cover	Woodland, Intensive agriculture (arable)
Waterbody ID

Other case studies in this subcatchment: Apelnäs fishway at River Rolfså, Biologisk återställning i Rolfsåns vattensystem, Bosgården nature-like fishway at River Rolfså, Restorations of River Nolån-Hulta dam removal, ´Restorations of River Nolån-Bypass channel in Hulta Hydro power plant, ´Restorations of River Nolån-Fishway in Forsa hydro power plant, Ålgårda nature-like bypass channel at River Rolfsån

Site

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Name	Grönkullen hydro power station
WFD water body codes
WFD (national) typology
WFD water body name	River Sörån
Pre-project morphology	Artificial bed, Artificial channel, Embanked, Over deepened, Over-widened
Reference morphology
Desired post project morphology
Heavily modified water body	Yes
National/international site designation
Local/regional site designations
Protected species present	No
Invasive species present	No
Species of interest	Lake dwelling brown trout
Dominant hydrology
Dominant substrate
River corridor land use	Woodland
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

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Reach length directly affected (m)	200200 m <br />0.2 km <br />20,000 cm <br />
Project started	2002
Works started	2005/08/01
Works completed	2005/10/31
Project completed	2005/10/31
Total cost category	500 - 1000 k€
Total cost (k€)	500500 k€ <br />500,000 € <br />
Benefit to cost ratio
Funding sources

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
Monitoring

Reasons for river restoration

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Mitigation of a pressure	Barriers to fish migration, Hydropower
Hydromorphology	Continuity for organisms, Quantity & dynamics of flow
Biology	Fish
Physico-chemical
Other reasons for the project

Measures

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Structural measures
Bank/bed modifications	Barriers removal, Bed-raising
Floodplain / River corridor
Planform / Channel pattern
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Non-structural measures
Management interventions
Social measures (incl. engagement)
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Monitoring

Hydromorphological quality elements

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quality elements

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

Biological quality elements

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quality elements

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Physico-chemical quality elements

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quality elements

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Any other monitoring, e.g. social, economic

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

Monitoring documents

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Image gallery

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Downstreams from the dam(photo. Maria Arola)

Part of the old dam (photo. Maria Arola)

Removed dam (photo. Maria Arola)

Additional documents and videos

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Additional links and references

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Supplementary Information

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