New Zealand’s first homegrown fish-friendly flood pump, commissioned by Waikato Regional Council, has successfully passed a 1.2-metre long shortfin eel on its way to the sea.
The prototype pump, which has been developed to replace existing MacEwans PPF axial pumps, was installed at the council’s Huntly golf course pump station in December for testing.
The new pump kicked into action at the end of January with the arrival of heavy rain, with seven tuna and eels passing through into a net attached to its outlet.
Pathways to the Sea programme manager, Michelle White says the largest tuna was 1.2 metres in length and weighed 4.2kg, while the other six ranged in size from 664mm to 878mm.
The eels were released in the lower catchment and are now free to safety make their way out to sea to breed, she said.
“This was an awesome first result. The big eel was a resident shortfin eel that had been living in the catchment for decades. This eel is a developing migrant and was in perfect condition after going through the pump,” said Ms White.
The council, which owns and operates more than 120 pump stations, began its efforts to ensure safe fish passage in 2015 with an investigation that showed there could be significant mortality of tuna over 600mm in length as they travel through existing flood pumps during migration to the sea.
In response to the finding, Council set up its Pathways to the Sea research and development programme to improve downstream fish passage at pump stations.
It approached MacEwans Pumping Systems to develop a fish-friendly pump and says the New Zealand company jumped at the opportunity.
MacEwans Pumping Systems general manager, Tom Bailey says the challenge to build a fish-friendly pump opened his eyes to the life cycle of New Zealand short and long-finned eels, which breed only once, at the end of their life, and at sea.
“We’d been approached by councils to build fish-friendly pumps for a couple of years, but to have Waikato Regional Council willing to be involved, and have funding for the project, that made the decision a much easier one,” says Mr Bailey.
“I was so pleased with that big eel coming through! This has been a five-year endeavour with many challenges along the way, like COVID-19 and labour shortages, so to have this result the first time the pump operated is such a relief.”
He says the fish-friendly prototype has been designed to retrofit pumps with 24-inch impellers that MacEwans installed widely across New Zealand between the 1960s and 1980s.
“If this pump proves to be a success over the entire migration season, we’ll also look at changing out larger 30-inch impeller to fish-friendly.”
Features of the new pump that make it fish-friendly include a slower rotational speed, having just two blades compared to four, and ensuring more space between the impeller (rotating blades) and stator (outer cavity).
The development of the pump, with design assistance by Callaghan Innovation, included the creation of a scale-sized pump and testing using 3D-printed rubber eels – scaled equivalents of 800mm, 1.2m and 1.5m eels.
High-speed videography showed even the 1500mm eels made it through in one piece.
Council Integrated Catchment Management Director, Greg Ryan says the development of the pump is exciting and “innovation in action”.
“There has been a huge amount of research that has got us to this point and early indications are that this pump is working as we expected it to,” said Mr Ryan.
“Our flood control schemes were built many, many years ago to safeguard lives and properties and enable productive use of the land. They knew what they knew back then when they put in this infrastructure, and not what we know now. The impact of these old pumps on these taonga species is something we want addressed.”
The council installed the country’s first fish-friendly pump at Orchard Road, Te Kauwhata in 2017, and another at its Mangawhero pump station in 2021. Two fish-friendly pumps are also due to be rolled out at Council’s Churchill East Pump station, Hampton Downs, at the end of the month.
“We’re replacing our pumps as they come to their end of life with fish-friendly ones, but no-one was building them in New Zealand, so we’ve been having to look overseas for them,” said Mr Ryan.
“With a MacEwans fish-friendly pump, we’ll be able to retrofit our pump stations at a much lower cost as we won’t have to ship in pumps from overseas or completely redesign the infrastructure to accommodate them.”
The council is monitoring the fish friendliness of the pump until May, when the tuna migration season ends.
Waikato Regional Council contributed $280,000 towards the research and development of the pump, which includes $120,000 from Waikato-Tainui. Council’s Pathways to the Sea programme also has funding from other regional councils, MPI Sustainable Farming Fund, Waikato River Authority and Waikato Ecological Enhancement Trust.