Evaluation of the efficency of the fish bypass channel at the power plant Freudenau/Vienna
Abstract
The first fishway along the Danube in Austria was incorporated into the construction plans for the Freudenau power station. It consists of a near-natural circumvention stream with an adjoining nature-like pool pass upstream. This bypass channel has been in operation since 1998. Modern criteria were applied to evaluate its functionality both with regard to its role as a migration aid as well as a habitat. The approach mainly involved a survey of the system using traps in spring 1999 and 2000 as well as in fall 1999. During this period, 41 species successfully ascended through the bypass channel; this is equivalent to 72% of the potential 57 species. Fish that are "indifferent" to currents or that are moderately rheophilic, especially the bleak, white bream, European roach, vimba and zobel traverse the system into the impoundment in the greatest numbers. Only few indiviuals of stagnophilic species migrate into the bypass channel due to the rhithral character of the lower section; note, however, that such species are rare in the tailwater of the power plant. During the spawning season in spring, the indicator species of the free-flowing Danube, nose and barbel, migrate into the bypass channel in massive numbers. Whereas the barbel frequently ascend into the impoundment via the pool pass, only comparatively few nose traverse the entire system. The downstream migration along the bypass channel is negligible. Nonetheless, the very large, slow-moving Kaplan turbines ensure very high survivability for downstream migrating fishes. This migration, which can also take place over the lowered dam gates during high discharges, probably presents only a minor problem at the Freudenau power station compared with most other smaller Austrian dams. Over the course of the year, the bypass channel is colonized by a rich community comprising 42 fish species. Above all, nose and barbel - as rheophilic indicator species - use this area intensively for reproduction and as a habitat for juveniles. The fishway habitat therefore largely fulfils the function of a smaller Danube tributary of the grayling zone. The main problem with regard to functionality is therefore the relatively few spawning nose that migrate up the pool pass and into the impoundment. Downstream of the Freudenau power station, however, lies the longest free-flowing river stretch of the Austrian Danube with extensive, intact spawning sites. At any rate, the qualitative link between the nose population in the upper and lower reaches is guaranteed by the bypass channel. The fact that relatively few nose pass the entire system during the spawning period therefore has lower priority for the evaluation. Overall, based on the special prevailing conditions, the authors conclude that the Freudenau bypass channel can be classified as broadly functional despite the somewhat restricted immigration of stagnophilic species and the problems with the nose.
fish bypass channel river Danube water power plant fish migration
Publikationen
Einstellung und Überprüfung der Funktionsfähigkeit der FAH am KW Freudenau, Fischökologische Ergebnisse Herbst 1999
Autoren: Eberstaller, J., Honsowitz, H., Pinka, P., Krichbaumer, B., Urbanek, St. Jahr: 2000
Forschungsbericht (extern. Auftraggeber)
Einstellung und Überprüfung der Funktionsfähigkeit der FAH am KW Freudenau, Fischökologische Ergebnisse Frühjahr 2000
Autoren: Eberstaller, J., Honsowitz, H., Pinka, P., Krichbaumer, B., Urbanek, St. Jahr: 2000
Forschungsbericht (extern. Auftraggeber)
Mitarbeiter*Innen
Jürgen Eberstaller
Dipl.-Ing. Dr.nat.techn. Jürgen Eberstaller
Project Leader
01.01.1998 - 31.12.2001
BOKU Partner
Externe Partner
Technical University Vienna, Institute of Hydraulics and Water Management
keiner
partner