2022 – Tube Fishways: A New Fishway in the Pipeline for Large Dams

Nicholas Ostrovsky- Dams Engineer, GHD Pty Ltd (formerly Master’s Thesis Student, UNSW Sydney, Australia),  William Peirson – Adjunct Professor, Water Research Laboratory, School of Civil & Environmental Engineering, UNSW Sydney, Australia and Stefan Felder – Senior Lecturer, Water Research Laboratory, School of Civil & Environmental Engineering, UNSW Sydney, Australia

The construction of dams and other artificial in-river barriers has contributed to the decline in freshwater fish populations world-wide due to damaged river connectivity and disruptions to fish migration. Fishways are structures that can mitigate these harmful effects by providing fish with a safe passage to navigate across barriers without undue stress, delay or injury. Despite feasible but expensive fishway solutions for small barriers, for large dams fishways are rare and often impeded by poor performance and high costs. One potential solution for this problem is the Tube Fishway, an innovative fishway design that utilises an unsteady flow surge to transport fish in pipes over dams at much steeper slopes than traditional fishways.

This study investigates the application of the Tube Fishway at three existing large dams in Australia. First, a numerical model was developed to undertake hydraulic analyses of the Tube Fishway using unsteady pipe flow hydraulics, which was validated using experiments on a small physical model. In parallel, a screening process was undertaken to identify suitable dams for development of conceptual Tube Fishways using site- specific characteristics and local fish population data resulting in the selection of Brogo Dam, Menindee Weir and Tallowa Dam. Finally, the numerical model was used to analyse the hydraulic performance of the proposed Tube Fishways at each of the dam sites.

The hydraulic results of this study indicate that Tube Fishways may be a feasible solution to transport fish over the selected dams. However, further research is needed to ensure that fish can be safely transported across large dams. This new technology could potentially be a low-cost and effective solution to provide fish passage at large dams and help restore Australian freshwater fish populations.