Event Title

Session B8 - Restoration of fish migration at the Afsluitdijk, The Netherlands, a unique challenge

Location

UMass Amherst

Event Website

http://fishpassage.ecs.umass.edu/Conference2012/

Start Date

7-6-2012 2:10 PM

End Date

7-6-2012 2:30 PM

Description

The Netherlands is a low lying country with 2/3 of its area below sea level. The country is protected against the sea by an expanded water defence system consisting of dunes, dikes, dams and storm surge barriers. In the south western part, the province of Zeeland, the coastline was shortened by closing of many estuaries with closure dams during the decades after the 1953 storm surge disaster. Separated marine and fresh water systems were born. Also for safety reasons in the northern part of the country in the former Zuider Sea, a 32 km long closure dam was constructed in 1932: the Afsluitdijk. This dam connects the provinces of North-Holland and Friesland and separates the salt Wadden Sea (an international protected wetland) from the lake IJsselmeer. Nowadays this lake is a very important fresh water reservoir, a source for the preparation of drinking water, which is fed by the river IJssel, a branch of the river Rhine. The surplus of fresh water is drained daily through two large discharge sluices at low tides in the Wadden Sea. During high tides the sluices are closed preventing sea water to enter. Also during very dry summer periods the sluices remain closed for several weeks. It's obvious that this dam is an immense barrier for many migratory fish species. The adults of the strong anadromous counter current swimmers can hardly enter the fresh IJsselmeer due to the very high current velocities in the discharge sluices, already reached several minutes after opening. The anadromous juveniles, together with the katadromous adults are able to reach the Wadden Sea via the open discharge sluices, but during dry periods they have to wait several weeks which might be a problem. Flounder larvae and glass eel want to enter the fresh water at high tides floating in the flood stream (selective tidal transport). Also weak swimmers as smelts and sticklebacks normally use this water movement to enter inland water bodies. At the seaside, just behind the closed discharge sluices huge amounts of fish are gathering, waiting to enter, attracted by the fresh water discharge flow during the previous ebb tide. But it is uncertain if fish are able to stay close to the discharge sluices during the flushing period. And even if fish are able to resist this flow, it is very difficult to create an extra attraction flow in a fish way which can be competitive with the huge discharge flow. The European Water Framework Directive demands an improvement of the ecological quality of water systems. As a result many fish migration routes in The Netherlands have to be restored; also at the Afsluitdijk. This paper describes the ecological demands and design criteria for fish ways at this location as well as several possible solutions to eliminate this fish migration barrier.

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Jun 7th, 2:10 PM Jun 7th, 2:30 PM

Session B8 - Restoration of fish migration at the Afsluitdijk, The Netherlands, a unique challenge

UMass Amherst

The Netherlands is a low lying country with 2/3 of its area below sea level. The country is protected against the sea by an expanded water defence system consisting of dunes, dikes, dams and storm surge barriers. In the south western part, the province of Zeeland, the coastline was shortened by closing of many estuaries with closure dams during the decades after the 1953 storm surge disaster. Separated marine and fresh water systems were born. Also for safety reasons in the northern part of the country in the former Zuider Sea, a 32 km long closure dam was constructed in 1932: the Afsluitdijk. This dam connects the provinces of North-Holland and Friesland and separates the salt Wadden Sea (an international protected wetland) from the lake IJsselmeer. Nowadays this lake is a very important fresh water reservoir, a source for the preparation of drinking water, which is fed by the river IJssel, a branch of the river Rhine. The surplus of fresh water is drained daily through two large discharge sluices at low tides in the Wadden Sea. During high tides the sluices are closed preventing sea water to enter. Also during very dry summer periods the sluices remain closed for several weeks. It's obvious that this dam is an immense barrier for many migratory fish species. The adults of the strong anadromous counter current swimmers can hardly enter the fresh IJsselmeer due to the very high current velocities in the discharge sluices, already reached several minutes after opening. The anadromous juveniles, together with the katadromous adults are able to reach the Wadden Sea via the open discharge sluices, but during dry periods they have to wait several weeks which might be a problem. Flounder larvae and glass eel want to enter the fresh water at high tides floating in the flood stream (selective tidal transport). Also weak swimmers as smelts and sticklebacks normally use this water movement to enter inland water bodies. At the seaside, just behind the closed discharge sluices huge amounts of fish are gathering, waiting to enter, attracted by the fresh water discharge flow during the previous ebb tide. But it is uncertain if fish are able to stay close to the discharge sluices during the flushing period. And even if fish are able to resist this flow, it is very difficult to create an extra attraction flow in a fish way which can be competitive with the huge discharge flow. The European Water Framework Directive demands an improvement of the ecological quality of water systems. As a result many fish migration routes in The Netherlands have to be restored; also at the Afsluitdijk. This paper describes the ecological demands and design criteria for fish ways at this location as well as several possible solutions to eliminate this fish migration barrier.

https://scholarworks.umass.edu/fishpassage_conference/2012/June7/20