VERBUND Opens Carinthia's Technologically Longest Fish Ladder

The national water management plan by the Austrian Federal Ministry of Agriculture, Forestry, Environment and Water Management sees "accessibility" of the bodies of water as a priority and as the most important goal when it comes to the ecological state of our flowing bodies of water. Thus, it has been planned to make all significant bodies of flowing water in Austria, such as the Drau river accessible by 2021, in order to be able to once more offer animals living in the water conditions of life and for migration akin to real-life nature. In this regard, in previous months VERBUND has constructed a fish ladder according to the latest knowledge in this field, at the weir facility in St. Martin next to the Danube power plant in Rosegg-St.Jakob. Carp, trout, Danube salmon, pike and other animals can cross the cleverly conceived system of chambers to swim around the power plant. The ecological project was opened with a celebration on 27 October and was awarded the "Habitat-Water-Prize" by the state of Carinthia.

25 million euros for environmental protection measures for the power plants in Carinthia
"As part of a multidisciplinary, close cooperation with experts, authorities, fisheries and locals, VERBUND will invest around 25 million euros in environment and nature protection measures in Carinthia alone, as part of the 1^st and 2^nd national water management plan" emphasises Dr. Karl Heinz Gruber, CEO of VERBUND Hydro Power GmbH. "Additional to this is the creation of the accessibility across our ten Drau power plants as well as the close-to-nature structuring and configuration of the backwater areas and free-flowing stretches of water", says Gruber.

It was against this backdrop that the new fish ladder came about in the last months at the Drau power plant in Rosegg-St.Jakob. This connects the 500m long stream of the natural Drau river in the area of the weir facility in St. Martin with the 16.9m high upper water canal of the power plant and is considered to be a master ecological achievement as the longest technical deviation route.

After around a year of construction, altogether 130 pools with 17 calm and spawning zones were created in the impressive structure. Through special slits in the pools, the movement of the water can be kept constantly calm and the current can be directed in an s-bend. This corresponds to the pressure conditions of natural bodies of water. The fish ladder is targeted at the17 fish species known to inhabit this stretch of the Drau river. One of the most significant among them is the Danube salmon, which can grow up to 1m in length and is the fish species to take into consideration when specifying size. However, lake trout, nase and barbell can use the fish ladder to reach their spawning grounds. Fish ladders are an important contribution to the maintenance of the diversity of species.

The very low flow velocity in the 130 pools make it particularly possible for young fish and fish species weaker at swimming, such as bullheads, to have a more effortless swim. The term "fish ladder" reflects its functionality only in part. Ultimately, the structure serves all aquatic animals as a migratory aid. The subsurface in the fish ladder is also a valuable habitat for microorganisms and the smallest creatures such as larvae and animals which serve as sources of food for fish. This is why experts often speak of it as a migration corridor.

The fish ladder on the St. Martin weir was awarded a "Habitat-Water-Sign" prize from the Water Department in Carinthia on Monday, 27 October at 11:30am by subject specialist Reinhard Schinner, representing the councillor Rolf Holub. The constructure was itself not directly accessible to the public following the opening. New, extremely interestingly-designed display charts immediately present at the R1 Drau cycling path on the north side of the river, are located visibly to those riding by and provide information regarding the facts and function of the new fish ladders. The fish-trap and video monitoring and how and to what extent the new "power plant by-pass" is accepted by the water-dwellers will be assessed in the coming months.

Height difference: 16.9m between the natural Drau river and the upper water canal
Total length: 500m
Water flow: 324-362 litres/second
Construction type: enature® MultistrukturSlotFishpass
Pools: 130 enature®Pools
Aperture: 35cm
Calm and spawning grounds: 17
Water level difference: 13cm (between pools)
Layout of the current: meandering
Construction period: June 2013- June 2014
Total investment volume: 1.9 million euros