In Austria, more than a half of all electricity is produced with the help of hydropower plants. To reduce their ecological impact, dams are being equipped with fish passages that support connectivity of habitats of riverine fish species, contributing to hydropower sustainability. The efficiency of fish passages is being constantly monitored and improved. Since the likelihood of fish passages to be discovered by fish depends, inter alia, on flow conditions near their entrances, these conditions have to be monitored as well. In this study, we employ large-scale particle image velocimetry (LSPIV) in seeded flow conditions to analyse images of the area near a fish passage entrance, captured with the help of a ready-to-fly consumer drone. We apply LSPIV to short image sequences and test different LSPIV interrogation area sizes and correlation methods. The study demonstrates that LSPIV based on ensemble correlation yields velocities that are in good agreement with the reference values regarding both magnitude and flow direction. Therefore, this non-intrusive methodology has a potential to be used for flow monitoring near fish passages on a regular basis, enabling timely reaction to undesired changes in flow conditions when possible.
To establish good ecological status in European rivers, firstly there is the question of how to re-establish unhindered migration for fish at barriers. This article documents a project to re-establish longitudinal connectivity at a large epipotamal river at the Schwabeck Hydro Power Plant, Carinthia/Austria, from the selection of an appropriate fish pass system to the final function control. Instead of a standard vertical slot, the innovative enature® fish pass shape with a significant reduction of flow, velocities, energy dissipation rate, and turbulences, but with a clear enhancement of fish passage capability, was chosen. Using 2D hydraulic modelling and a statistical evaluation of fish passage, physical and ecological effects were reviewed, with the clear result that there is no identifiable, positive ecological effect on the number of fish migrating with an increase of concurrent flow in the fish pass. Passability and findability were monitored with the new FishCam, an automatic, precise, and constant (24/7 24 h a day, seven days a week) collection and pre-evaluation field data survey method which does not involve trapping of, contact with, or stress for fish. It was shown that the enature® fish pass enables an unhindered migration for all available fish species. As >99% of fish migrate from April to November, there is no ecological need to operate a fully functional fish pass year-round. Combining all the individual factors together, the fish pass at the Schwabeck Hydro Power Plant is an almost exemplary solution for a fully functioning restauration of the continuum with a minimized loss of generation of electricity.
Analyse der Auffindbarkeit, der Tagesund Jahresgänge der Fischwanderung und die Auswertung von Massenwanderungen.
Zusammenfassung Das Thema Auffindbarkeit von FAH wirft nach wie vor eine Reihe unbeantworteter Forschungsfragen hinsichtlich der Instinktbewegung von Fischen, ausgelöst durch Schlüsselreize, auf. Demzufolge ist eine systematische Abklärung für bestehende und insbesondere für zukünftige FAH Projekte zielführend. Die Auffindbarkeit von FAH wird in verschiedenen Leitfäden, neben der Positionierung der Lage des Einstiegs, primär am Parameter Strömung (Rheotaxis) festgemacht. Aus hydraulischer Sicht hat jedoch die am Einstieg austretende Strömung schon von der Größe des Ausbreitungsfeldes her lediglich eine maximal untergeordnete Wirkung. Andere, äußere, die Wanderung beeinflussende Faktoren wie z. B. Licht, Temperatur, Sauerstoffgehalt, akustische Impulse u. a. m. wurden bislang vollkommen bzw. weitgehend außer Acht gelassen. Felduntersuchungen, die das Aufstiegsverhalten der Grundgesamtheit der migrierenden Individuen mit den Umgebungsreizen zeitgenau in Zusammenhang bringen, fehlen bisher. Ziel dieses Papers ist die systematische Abklärung der Wirkung alternativer Schlüsselreize auf die Auffindbarkeit von Fischaufstiegshilfen im Rahmen eines mehrstufigen Forschungsprojekts der VERBUND Hydro Power GmbH. Bei der hier beschriebenen Studie wurden die Daten des
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