40 years after its construction, the Annabrücke power plant on the river Drava is being upgraded with a brand new fish migration aid. The fish can migrate up and downstream through an elaborate system of 172 pools. As Austria‘s largest hydropower operator, we are aware of our responsibility to protect the environment and have been proving that all requirements can be reconciled with top performance for decades. We are implementing long-term plans to improve the ecology of Austria‘s rivers with our partners wherever possible, even in these difficult times. We are setting new standards in Europe with our measures; in 2018 with the longest fish migration aid and now in 2020 with the tallest fish migration aid,“ says Achim Kaspar, the Managing Board member responsible for generation at VERBUND. VERBUND is investing a total of around EUR 280 million in making its more than 130 hydropower plants more ecological, there­by also making a valuable contribution to stimulating the economy. „Habitat creation and linkage is an essential element in the conservation and enhancement of biodiversity in our water bodies. Since 2009, we have constructed more than 1,000 fish ladders for the National Water Management Plans, and many new ones are in the planning or implementation stages. The new fish migration aid in Annabrücke ascends 26 metres in height, making it the tallest in Europe. The Federal Ministry of Agriculture, Regions and Tourism has funded the project with EUR 450,000,“ highlighted Federal Minister Elisabeth Köstinger on the occasion of the ceremonial opening. State Parliament President Reinhart Rohr also expressed his pleasure: „Things are looking up in Carinthia not only for the fish, but also for environmental protection! During my time serving as the Environmental Officer of the Province of Carinthia until 2010, I initiated the first steps in this area. Now, ten years later, all of Carinthia is proud to be able to open the tallest fish migration aid in Europe. Making use of nature while at the same time respecting its needs is the promising path for a sustainable Carinthia – and with this project we have once taken again a decisive step forward.“

28 million euros towards barrier-free power plants in Carinthia
„Hydropower is rightly considered the cleanest form of energy generation. We strive to keep our facilities up to date with the latest technical and ecological standards, and this of course includes the creation of fish migration passages. Doing so means giving nature back a piece of biodiversity, even on heavily modified bodies of water,“ says Karl Heinz Gruber, Managing Director of VERBUND Hydro Power GmbH. The commissioning of the fish migration aid at the Annabrücke power plant means that 8 of the 10 Drava power plants are once again passable for fish. Complete continuity over a stretch of 260 kilometres should be possible by 2022. „The migration aid currently under construction at the Ferlach power plant is scheduled to go into operation in autumn 2021, and the last one at the Feistritz power plant will be ready by September 2022,“ adds Gruber. VERBUND is investing around EUR 28 million in ecological measures in Carinthia on the Drava and at its Malta and Reißeck stor­age power plants between now and 2022. The fish migration aid Annabrücke accounts for EUR 3.5 million of this, including planning and monitoring measures.

New standards in structural implementation
There is a height difference of 26 metres be­tween the top and bottom of Drava power station Annabrücke. In order for fish to be able to scale this height, an elaborate system of 172 concrete pools and 21 resting pools is needed. The pool structure is specially designed for the range of fish species found in the Drava and has very low flow rates in the individual sections. The double slot ensures that the water movement is always calm. This helps the fish to save energy. The natural riverbed in the fish migration aid is a valuable habitat for microorganisms and tiny creatures such as larvae and other sources of food for fish. The fish migration aid is actually a migration corridor, as all aquatic life can use this route.
The ascent aid is particularly important for fish that migrate over medium distances, which undertake extensive upstream breeding migrations of up to several 100 km to find suitable breeding grounds and then return to their original habitats downstream.

Operational check successful
Each fish migration aid on the Drava is verified through extensive monitoring of fish ecology after its completion. This includes recording fish migration by means of video monitoring in a contact-free, stress-free manner that does not disturb the fish. There is a short video sequence of each fish that passes through the fish migration aids. The exact time, fish species, length and direction (ascent or descent) are determined and recorded in a database. A total of several hundreds of thousands of fish have been recorded so far. This proved that all fish species found in the Drava, including smaller and juvenile fish that are weak swimmers, are already successfully migrating through the fish migration aids. We are particularly pleased with the documented upward migration of the „assessment fish“. Several catfish with lengths over 120 cm have already been registered.