The successful design and optimal operation of vertical slot fishways relies upon an understanding of the ways fishway hydraulics can limit fish passage. Hydraulic performance criteria for vertical slot fishways are well established Australia. Criteria have developed over time, often through in situ evaluations of fishway performance.
Passive Integrated Transponder (PIT tag) data has been collected for up to 20 years at several Murray River fishways. This dataset offers an opportunity to learn about fishway function, but standalone analysis of PIT tag data is difficult as fish movement is driven by a range of external factors, including the time of year, river flows, temperature, and importantly the fishway hydraulic conditions. This study involved the detailed reconstruction of hydraulic conditions within five selected fishway sites, allowing for correlation with PIT tag records. This reconstruction covered around 20 years of fishway operation at each site and involved tens of thousands of simulations of fishway hydraulics. Using this modelling all fish movement events recorded historically can be associated with a detailed estimate of fishway hydraulics at the time of the event.
The available PIT tag data and reconstructed hydraulics information have been analysed in an attempt to validate current hydraulic performance criteria. While the analysis largely supports current design criteria, potential conservatism in two specific areas has been identified. Operation of the fishways studied may be adjusted in light of the analysis undertaken.
The study demonstrates the benefits of combining existing historical datasets with digital modelling and analysis tools. It is hoped the hydraulic database and modelling methodology developed in this project will have ongoing use in the design and optimisation of fishways.