Abstract

The confluence between a hydropower tailrace and the old river bed in Stornorrfors in the river Umealven in the northern part of Sweden has shown to be the largest obstacle for upstream migrating salmon and sea trout. Fish are attracted to the high flow rate from the tailrace and will not migrate upstream in the old river bed to the fishway leading past the hydropower dam. By using triangulation from eight antennas in the confluence, the tracks of radio tagged migrating fish can be determined. These tracks are then compared with three-dimensional Computational Fluid Dynamics (CFD) simulations of the confluence. By simulating the most common combinations of turbine flow and spill flow in the old river bed it is possible to find correlations between fish movements and the flow field. It was previously assumed that fish had trouble locating the old river bed, the results of the triangulation however shows that most fish find the old river bed within a few days but do not chose to migrate until several days or even weeks later. The main issue is therefore not how to attract the fish to the old river bed, but rather how to create favorable conditions in the old river bed so that migrating fish are more inclined to take that path upstream.

Published in

Book title: Proceedings of the 11th International Symposium on Ecohydraulics
ISBN: 978-0-7340-5339-8
Publisher: University of Melbourne

Conference

11th International Symposium on Ecohydraulics

Authors' information