Author(s): Raf Baeyens; Johan Coeck; Jenna Vergeynst; Ans Mouton; Ine Pauwels
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Abstract: Pumping and hydropower stations serve the essential need for power generation, shipping, irrigation and water level control worldwide. However, they may seriously impact the aquatic ecosystem due to habitat deterioration, fragmentation and the direct physical impact on organisms. Specifically fish that pass such structures may be killed or severely injured. Therefore scientists and engineers seek for high capacity pump and turbine types that minimize the physical impact on passing fish. For instance, pumps and turbines with Archimedes screws are assumed to be more fish friendly than widely used propeller type pumps and turbines. In the Albeit Canal in Belgium, the first Archimedes screw hydropower plant was built, and more are to follow. The hydropower plant consists of three open Archimedes screws with a 10 m head and maximum capacity of 5 m3. s-1 each. In this study the impact ofthe Archimedes screws was assessed at three different modes ofoperation (3, 4 and 5 m3. s-1). To evaluate the impact, mortality and injury of 900 European eel (Anguilla anguilla), 900 roach (Rutilus rutilus), 900 bream (Abramis abramis) and 900 rainbow trout (Oncorhynchus mykiss) was quantified after forced passage through the Archimedes screws. Injury was defmed as ‘heavily injured' (cuttings, bruises, bleeding, swelling or scale loss > 25%), 'slightly injured' (fin damage or scale loss < 25%) or ‘not injured'. In general, around one third ofthe fish died and 10% got injured due to turbine passage. Of the injured fish more than half were heavily injured. Nearly all dead or heavily injured fish showed bruises and some were decapitated. Furthermore, 10% of the individuals that survived the turbine passage, died within one week due to observed or hidden (internal) injuries. Additionally, differences were obselved between species, and between modes of operation. Although Archimedes screws are assumed to be fish friendly, this study indicates considerable fish mortality, mainly caused by fish being squeezed between the screw and its housing as indicated by the decapitations and bruises. Adaptations to the screws that prevent this, might thus further improve the fish friendliness of Archimedes screw hydropower plants.
Year: 2018