Water promenade for fish & Co

The Nussdorf weir was built in 1899 as a flood defence structure for the city of Vienna. The small-scale power plant in Nussdorf has provided energy for the inhabitants of Vienna since 2005. For fish & Co., however, this has as yet always been the final stop. Fish who, on their way up the Danube, have opted for the Danube Canal are not able to migrate back to the Danube through the weir and power plant. The new fish ladder will remove this barrier and reconnect the Danube and the Danube Canal, restoring its status as one traversable habitat. Federal Minister Alois Stöger, councillor Ulli Sima and section manager Wilfried Schimon, as well as high-ranking representatives of governmental agencies, power plant partners and participating firms today launched construction activities for the fish ladder with a symbolic groundbreaking.

Hydropower plants and obstructing structures put a strain on a body of water's ecosystem, as the continuity of the river is interrupted. The natural life cycles of numerous aquatic creatures and organisms require migration into other sections of the river. This is why the traversability of bodies of water plays a key role in the renaturation of obstructed waters. "We have to ensure that water habitats remain intact," Federal Minister Andrä Rupprechter emphasised on the occasion of the groundbreaking. "One important improvement measure is rendering the waters traversable for fish. With the 1st National Water Management Plan, we have already removed 1,000 obstructions to migration across Austria. In the case of this project here in Nussdorf, we are implementing an especially large and important project together with many supporting partners," continued Rupprechter.

And this project, too, shows that ecological and business interests can be brought together. "The fish bypass in Nussdorf creates a passable connection between the Danube and the Danube Canal, and is one of many measures implemented by the Action Programme Danube, in which shipping, ecology and flood protection work together in harmony. In this way, we preserve the ecological functionality of the Danube and simultaneously fulfil the specifications of the EU Water Framework Directive," underlined Federal Minister Alois Stöger.

The Nussdorf joint-venture power plant was constructed in 2005 by VERBUND, Wien Energie and EVN and generates around 28 GWh of electricity annually with an output of 4.8 MW. "Electricity generation and environmental protection are not opposed to one another in Vienna - quite the contrary. We are betting on environmentally-friendly energies and, with the current fish ladder project here at the Nussdorf small-scale power plant, we are demonstrating that it is possible to effectively integrate the production of energy with the preservation of nature," explained Vienna's environmental councillor Ulli Sima.

VERBUND will take over preliminary financing of 50% of the construction costs during the construction phase. Board Member Günther Rabensteiner makes it clear that hydropower and ecology are sustainably compatible: "We are demonstrating our commitment with an investment programme of around € 250 million for the construction of fish bypasses like this one, both in new power plant projects as well as in existing facilities. And this is not only for legal reasons, in accordance with the EU Water Framework Directive and the National Water Management Plan, but also simply as an ecologically responsible and sustainable producer of green energy."

The Nussdorf fish ladder has been scaled for specimens up to 1.5m long on the basis of the wels catfish, a predominant fish species of the Danube, and will cover an altitude differential of around 3.6 m under mean flow conditions. It will have an overall length of ca. 322 metres and will be composed of a string of 37 water basins and an open channel area with a near-natural design. "Fish have to be able to migrate, bodies of water made passable and habitats linked. The fish ladder for the transverse structure in Nussdorf is thus an important measure for the fish fauna of the Danube, and one completely welcomed by fisheries," added Georg Holzer, chair of Vienna's Committee for Fisheries.

Architectural Gem on the Danube Canal

What sets the Nussdorf fish ladder apart is its location in an historically significant ensemble from the era of Otto Wagner. Just as unique is the tunnelling underneath such an historical construction as the famous Schemerl Bridge (Schemerlbrücke) with its two lions gazing up the Danube.
The restoration of traversability for fish conforms with the specifications of the EU Water Framework Directive and the National Water Management Plan, and the planning of the fish ladder took place in accordance with the guidelines of the Ministry of Agriculture, Forestry, Environment and Water Management (BMLFUW) regarding the construction of fish ladders. Planned and approved by the authorities during the years 2012 to 2015, construction will now take place from November 2015 to December 2016.

The project is a collaboration between DHK and VERBUND Hydro Power GmbH and is supported by funding from the Federal Ministry of Agriculture and Forestry, Environment and Water Management (BMLFUW), the Federal Ministry for Transport, Innovation and Technology, the city of Vienna and the Vienna Committee for Fisheries, as well as the Lower Austrian Fishery Association (NÖ Landesfischereiverband).