Fish descent
Fish descent is the downstream migration of fish, especially in the area of weir and hydropower systems on rivers . The opposite of fish migration is fish migration . The issue of fish migration plays an important role, particularly in the approval of transverse structures and hydropower plants , but also in the course of implementing the EU Water Framework Directive .
state of research
The fish migration is currently being intensively researched because it is also included as a requirement in the European Water Framework Directive . However, just as with the fish pass, the findings and specifications have not yet been sufficiently implemented , especially for older hydropower plants and transverse structures . At non-continuous hydropower plants, if fish do not descend via the fish ladder, they have to pass the floating debris rake and the turbines of hydropower plants on the downstream migration . In the event that the fish can fit through the rake, the descent through the turbine can be associated with significant mortality , depending on the turbine type, size and speed . The fish that cannot fit through the rake due to their body proportions cannot pass the hydropower plant. If fish have to migrate through several hydropower plants on their downward migration path without a descent device, a complete failure of the migration or the population of the fish is to be feared. However - as is often wrongly assumed - the turbine is not the decisive factor for mortality: the success of the fish willing to descend depends primarily on the design of the migration system, i.e. the design of the power plant periphery.
Fish-friendly power plant design
Fine screen and bypass
Modern hydropower plants are therefore already designed in such a way that an injury-free descent is possible for all living things willing to migrate. A suitable design of the rake as a fine rake (slide rule spacing less than 20 mm) and a guidance system for finding the bypass prevent the descent through the turbine chamber. Master screen bypass systems, which are designed according to the current state of biological knowledge, enable the wandering creatures to safely track down the bypass as a way of descent and to swim past the turbine chamber without injury. Numerous field studies and laboratory tests prove the functionality of the system.
Fish friendly turbines
By combining a fish-friendly design of the hydropower plant with a fish-friendly turbine, mortality can also be reduced for the living things that get into the turbine despite the fine rake. Criteria for fish-friendly turbines are among others
- low number of impeller blades (reduction of the likelihood of collision),
- low speeds (reducing the likelihood and speed of collisions),
- blunt leading edges (reducing the risk of injury in the event of a collision) and
- Gap-free turbines, i.e. without gaps between the impeller blade and hub, or minimal gaps between the impeller blade and the outer wall of the turbine (reduction of the risk of injury through trapping).
These criteria are met, for example, by variable-speed propeller turbines . Instead of adjustable impeller blades, variable-speed turbines have fixed blades. Instead of adjusting the blade angle as in Kaplan turbines, the speed is adapted to the fluctuating flow. The complex mechanics for adjusting the impeller blades on the rotating shaft are therefore not required with variable-speed turbines and the number of blades can be set and reduced as required (minimum 3 blades). In addition, the connection between the impeller hub and blades is completely free of gaps.
Modern hydropower screws with an integrated fish lift also enable fish to pass safely in both directions. Another possibility of fish-friendly power plant design is the shaft power plant .
Power plant examples with modern fish descent facilities
Halle-Planena hydropower plant
The Halle-Planena hydropower plant is located on the Saale . The expansion water volume is 50 m³ / s with a fall height of 2.36 m. The hydropower plant has a control screen bypass system, i. H. by means of a horizontally positioned fine rake with horizontal rake bars and a guide wall on the river bed. The alignment of the rake against the current is approx. 45 °. The living beings willing to descend are led along the rake or the guide wall in the direction of a bypass. Using the bypass, they can descend past the turbine chamber into the underwater.
Öblitz hydropower plant
The Öblitz hydropower plant is located on the Saale and was commissioned in 2017. It has a control screen bypass system with a horizontal screen and bypass through which the living beings can descend past the turbine chamber into the underwater. The expansion water volume is approx. 50 m³ / s. Up to 26 species of fish are mapped on site. In addition to the fish descent facilities, fish-friendly propeller turbines are installed.
Shaft power plant Großweil
Individual evidence
- ↑ Dimensioning and design of fish protection and fish migration systems. (PDF) (No longer available online.) Archived from the original on April 20, 2016 ; accessed on May 2, 2015 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ↑ Institute for Applied Ecology (Ed.): Studies on the orientation and search behavior of migrating fish to optimize the dimensioning and arrangement of fish protection facilities in front of hydropower plants . Ethohydraulic studies.
- ↑ a b Marius Heiß: Evaluation of innovative rehabilitation measures targeting downstream migrating Atlantic salmon smolt (Salmo salar) at a hydroelectric power plant in southern Sweden . 2015.
- ↑ Home - Forum Fish Protection & Fish Downstream | Forum fish protection & downstream migration. In: forum-fischschutz.de. Retrieved September 23, 2016 .
- ↑ Master screen bypass system according to Ebel, Gluch & Kehl. (PDF) Retrieved May 2, 2015 .
- ↑ Ecological consideration of the fish migration at HPP Halle Planena. Wasserkraftanlage Planena GmbH & Co. KG, accessed on May 2, 2016 .
- ↑ Dipl.-Hydrol. Arne Gluch: Sustainability in hydropower plants Fish descent downstream fish passage. (PDF) State Office for Flood Protection and Water Management (LHW) Saxony-Anhalt, accessed on May 2, 2016 .
- ↑ Dr. Armin Peter: Downstream migration - Biological improvement of Bypass System. Retrieved May 2, 2016 .
- ↑ Use of the master screen bypass system according to Ebel, Gluch & Kehl on hydropower plants - basics, experiences and perspectives. Springer Vieweg, accessed May 2, 2015 .
- ↑ Werner Dönni, Fischwerk, Kriens Lukas Boller, AquaPlus, Zug: Fish descent: Systems in Germany are convincing. Documentation of two systems on the Saale in Saxony-Anhalt. (PDF) WWF Switzerland, Environment & Resources Department, Water Section, 2010, accessed on February 20, 2018 .
- ↑ Dr. Guntram Ebel: Fish protection and fish descent at hydropower plants. Computing and bypass systems manual . Ed .: Office for Aquatic Ecology and Fishery Biology. 2013, ISBN 978-3-00-039686-1 , 3.2 Fish-friendly turbines, p. 133 ff .
- ↑ Fella Maschinenbau GmbH: DIVE-TURBINE - speed adjustment. In: www.dive-turbine.de. Retrieved May 4, 2016 .
- ↑ See study by B. Zeiringer from the University of Natural Resources and Life Sciences on the fish compatibility of the hydropower screw with an integrated fish lift in Neubruck (Lower Austria), which is operated by the Hydroconnect company.
- ↑ Halle-Planena hydropower plant. Retrieved February 20, 2018 .
- ↑ a b Dr. Guntram Ebel: Fish protection and fish descent at hydropower plants. Computing and bypass systems manual . Ed .: BGF Office for Aquatic Ecology and Fisheries Studies. Halle (Saale) 2013, ISBN 978-3-00-039686-1 , p. 336 ff .
- ↑ Ecological consideration WKA Halle-Planena. Retrieved February 20, 2018 .
- ^ Norbert Finster: Überlandzentrale participates in hydropower plant. Mainpost Regional, August 28, 2017, accessed February 20, 2018 .
- ↑ Picture gallery of the Öblitz hydropower plant. Lower Franconian overland headquarters, accessed on February 20, 2018 .
- ↑ Europe's most fish-friendly hydropower plant goes online. (PDF) zek Hydro, accessed on February 20, 2018 .
- ↑ Öblitz hydropower plant - installation of turbines. (Video) Retrieved February 20, 2018 .
- ↑ Picture gallery of the Öblitz hydropower plant under construction. Retrieved February 20, 2018 .
