Iwi welcome trial of new flood pump allowing native fish a safe passage

Jun 30, 2023

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Roimata Minhinnick of Ngāti Te Ata on site at the Mangawhero pump station. Photo / Supplied

When Ngāti Te Ata was told by Waikato Regional Council that it wanted to put the outlet of a new fish-friendly pump on the iwi's land, they jumped right on board.

"As an iwi, and as a landowner, it was an immediate attraction because of the kaupapa," says Roimata Minhinnick of Ngāti Te Ata.

The Mangawhero pump station is in Aka Aka on the eastern side of the Waikato River in northern Waikato, about 7km from the town of Waiuku. Water pumped through the station enters a lake on the iwi's 10-hectare property before flowing into the Waikato River. The site is adjacent to an old Ngāti Te Ata pa.

The new screw pump is part of Pathways to the Sea, a research and strategy development programme by the regional council to help manage flood pump impediments to fish passage and which will lead to the development of a regional fish passage strategy.

"Just before lockdown, we turned the lake into a tuna [eel] reserve because we weren't finding any tuna in traditional places, including the Mangawhero awa, and those we did find were small," says Roimata.

"We thought there is a problem here and maybe a reserve would help.

"The old pump prevented the migration of tuna, so we’re not surprised at their shortfall in the lake.

"When we were approached by WRC to explore working together to replace the old pump with one that would allow their migration, it was a no-brainer.

"We know the new pump is a success overseas, although testing has been limited to the size of eels abroad, which are smaller."

Waikato Regional Council received $4.48 million from Kanoa – Regional Economic Development & Investment Unit, administered by the Ministry of Business, Innovation and Employment, towards upgrading five pumps in Waikato catchments to enable safe downstream passage of native fish.

That includes developing a monitoring programme to test the success of the 10-metre by 1.6-metre screw pump, which was built in the Netherlands and installed following a cultural ceremony by Ngāti Te Ata in July last year.

If the pump is proven successful, this technology could have significant benefits for tuna populations in pumped catchments throughout New Zealand.

One-hundred and sixty-four shortfin eels were tagged by Niwa ahead of the migration season, which usually begins around the start of February.

A sock net has been attached to the outlet of the Mangawhero pump to capture any fish that pass through, and a passive integrated transponder (PIT) system is in place at the site to assess the behaviour of the tagged tuna at the pump.

All fish captured will be measured and checked for any injuries.

Healthy tuna will be released downstream, to safely enter Ngāti Te Ata's lake and have access to the sea.

Historically, Ngāti Te Ata developed sophisticated sustainable practices of containing, catching and processing tuna.

Roimata says the council's Mangawhero project was an opportunity for Ngāti Te Ata's young people to get involved and learn to take care of their environment, as kaitiaki.

"We’re interested in not just restoring tuna numbers but in improving the water quality in the catchment and revitalising the environment.

"We will be doing some riparian planting around the lake, working with Te Whangai Trust in Pukekohe which helps youth in trying circumstances get back on their feet, and enable schools to get involved."

Pathways to the Sea project manager Michelle White says the issue of fish passage is not unique to the Waikato, "but we do have the largest number of flood pumps in New Zealand, and therefore understanding how we can avoid, remedy or mitigate the impact these assets have on our native fish is a priority for our council."

The council is also working with MacEwans Pumping Systems and Callaghan Innovation to develop a fish-friendly pump to replace existing MacEwans PPF axial pumps – found widely in New Zealand – without the need to make any civil structure modifications to pump stations.

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