The state of North Rhine-Westphalia and RWE Innogy officially inaugurated pilot plant for fish protection


Source: RWE AG

North Rhine-Westphalian Environment Minister, Johannes Remmel, and Dr. Hans Bünting, CEO of RWE Innogy, today officially inaugurated the fish protection pilot plant at the hydropower station of Unkelmühle. The power plant on the Sieg river has been converted into a pilot plant for fish protection as from 2011 to allow upstream and downstream fish migration at this point of the Sieg river. An ecological and technical monitoring programme, scheduled to run up to 5 years, will now investigate the effectiveness of the implemented measures and any possible further improvements. Moreover, the programme seeks to ascertain in how far plants of this kind are compatible with the cost-efficient generation of renewable energy from small-scale hydropower plants.

Johannes Remmel: 'The use of renewable energy sources should not be irreconcilable with living bodies of water in North Rhine-Westphalia. We therefore aim to maintain and enhance the biological diversity in our streams and rivers and to reintroduce migratory fish species which have formerly been indigenous to the state of North Rhine-Westphalia. The salmon is a good example for the success of our long-standing efforts. To date, more than 3,900 salmon have returned from the ocean to North Rhine-Westphalia, in particular the Sieg river. We plan to increase this number even further in the future by improving fish protection at existing hydropower plants.'

Dr. Hans Bünting added: 'Hydropower is an important element in the energy transition. It is able to compete with conventional power generation and, moreover, can be controlled and managed easily. That is why we have been happy to allow our Unkelmühle hydropower plant to be used as a pilot plant for this long-term test. The test will provide us with important information on how to ensure the cost-efficient operation of hydropower plants while making them more environmentally friendly at the same time. RWE has gathered experience in the operation of hydropower plants in accordance with fish protection requirements over many years. We are therefore greatly pleased to cooperate with the state of North Rhine-Westphalia in this field.'

The planned project is part of the migratory fish programme of the state of North Rhine-Westphalia which is aimed at improving the Sieg river for fish species that depend on different habitats in a river landscape for spawning, nursing and feeding and migrate between river and sea. These are salmon and eel in particular.

As the first plant of its kind in the Sieg system, the Unkelmühle hydropower plant is well-suited as a testing site as its size and capacity are typical for hydropower plants in North Rhine-Westphalia. Moreover, the power plant is situated on a river in which salmon and eel populations are very well documented. Their return to these waters had only become possible after substantial improvements in terms of water quality and fish passage.

Illustration - Pilot plant
Illustration - Pilot plant

Technical details of the pilot plant

Fine screens: To test and improve, if necessary, the effective passage and protection of salmon and eel on the Sieg river (passing fish around hydropower plants without them being injured), the pilot plant was equipped with a novel type of fine screen which has a bar spacing of 10 mm. The narrow space between the bars is to prevent that fish migrating downstream are caught in the turbines and injured. A sophisticated biological monitoring process is to test the effectiveness of the measures taken to protect salmon and eel. Moreover, it will be examined during routine operation what effect the narrow bar spacing of the screen has on the hydropower plant's energy generation. After completion of the monitoring programme, the results will be analysed to assess in how far such measures and the efficient generation of energy in hydropower plants mutually influence each other.

Downstream fish migration facility: At the Unkelmühle plant, several possibilities are being tested of how to help fish to bypass the power plant's turbines and migrate upstream or downstream: A passing chute above the screen is provided for the migration of fish, such as salmon, which swim near the surface. So-called eel pipes are intended for fish that rather move along the water’s bottom. Moreover, a 'Bottom Gallery' is being tested for eels. Transverse to the inlet channel, a flap-like device at the bottom catches the eels by alternating opening and closing and passes them around the hydropower plant.

Upstream fish migration facility: As early as 1990, a brick ramp and a so-called Denil fishway were installed at the Unkelmühle hydropower plant to allow the fish to pass from the downstream to the upstream water. Today, Unkelmühle has an upstream fish migration facility consisting of 27 step-like pools, meeting current requirements. This fishway allows the fish to overcome the height difference of 3 m.

Monitoring: The various migration paths have been equipped with measuring devices. The migrating fish are counted and partly examined by expert staff. In addition, the salmon and eels are tagged with miniature transmitters and monitored telemetrically in order to allow detailed tracking of their migration paths near the hydropower plant.

Unkelmühle hydropower plant
The run-of-river hydropower plant is situated in the community of Windeck on the Sieg river. With an installed capacity of 420 kilowatts, the power plant, which was commissioned in 1924, has been generating enough electricity to power more than 500 households every year in a climate-friendly way.

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