Author(s): Lovisa M. Sjostedt; J. Gunnar I. Hellstrom; Anders G. Andersson

Linked Author(s): Gunnar Hellström, Anders Andersson

Keywords: Ecohydraulics; CFD; Fish migration; River Hydraulics

Abstract: Fishways have been built for many years to increase connectivity, however many have low passage efficiency since the fishes have trouble finding the entrance or choose to swim into competing flows instead. It is difficult and expensive to do experiments on-site in rivers and to get a better understanding of the fish's behavior, it is here proposed to use hydraulic modelling as an additional resource. This approach is applied in the river Umealven in northern Sweden, where downstream migration for salmon smolt has been a known problem since the construction of the hydropower plant. Here a technical fishway has been installed upstream of the plant designed for both upstream and downstream migration. To improve passage efficiency, a floating boom was installed to lead smolt to the fishway. A Computational Fluid Dynamics model of a part of this river stretch was created to provide hydraulic parameters, such as velocities, accelerations and turbulent quantities. In the same domain, migrating salmon smolt tracks were integrated into the model and compared with the hydraulic conditions to find correlations with fish behavior. The results show that most of the downstream migration smolts were likely to follow the main flow, that the floating guiding boom influences the flow pattern and hydraulic conditions in the nearby area and changes the swimming pattern of the affected smolts. The simulations also indicate an increase in turbulence kinetic energy, velocity gradients, and accelerations in the area close to the boom. The approach of combining telemetry studies and CFD simulations in this study is to be further developed in the future.

DOI: https://doi.org/10.3850/978-90-833476-1-5_iahr40wc-p0582-cd

Year: 2023