Ngā Rerenga ki te Moana | Pathways to the Sea Strategy: Fish passage through pump stations

Report: PS 2023/18

Authors: Michelle White, Alicia Williams (Waikato Regional Council) and Brenda Bartels (2 Awa Ecology)

Flood control and land drainage schemes were extensively installed throughout Aotearoa New Zealand over 50 years ago to maintain ground conditions suitable for agriculture. At the time little consideration was given to the ecological impacts. Today, we recognise the need to operate the schemes within a broader set of objectives. This directive for change has come about because of strong legislative requirements, increased public awareness, large scale fish kill events, community expectations, new research and information, and the availability of new pump technologies.

Studies overseas and in Aotearoa have shown the devastating impacts that traditional pumps can have on native fish, in particular larger species like freshwater tuna. Within the Waikato region, research at Orchard Road and Steiners pump stations clearly demonstrated that traditional pumps inflict high mortality and injury rates. European countries have set a strong statutory response to a significant decline in the eel population. The provision of fish passage through infrastructure is now standard practice (if not mandatory) in some European countries. While the statutory response in Aotearoa has improved, regional councils and scheme managers also need to start implementing measures to improve fish passage through pump stations.

To help combat these effects, the Pathways to the Sea (PTTS) programme was formed in 2019, with the overarching mission to improve the safe downstream passage of fish at Waikato Regional Council (WRC) pump stations. As part of the programme, international research and relevant legislation was reviewed, and mitigation tools and new pumping systems were tested. Mitigation tools tested included trap and transfer, an electric barrier, gravity bypass outlet, and a passive acoustic tool. New pumping systems tested included a modified MacEwans pump, Encased Archimedes Screw pump and Bedford submersible pump. A tuna behavioural study was also undertaken.

This strategy brings together all the research and development undertaken as part of PTTS. Collation of this information guides decision making within an Aotearoa context, providing significant guidance, both internally and externally for other regional councils, territorial authorities, stakeholders and industry.