Fish friendly pump big enough for small shark

A new fish-friendly screw pump to be installed in Aka Aka, near Waiuku, is big enough to pass a small shark, laughs Waikato Regional Council project manager Richard Dodera.

The Archimedes screw pump, which is 10 metres in length and 1.6 metres in diameter, is the first of its kind in New Zealand. Built by FishFlow Innovation in the Netherlands, the pump is waiting to be installed at the new Mangawhero pump station which is nearing completion after being held up by COVID-19 alert levels affecting Auckland and the Waikato.

“It’s an impressive piece of kit,” says Richard, “even for someone like me who has been working around different types of pumps for a while now.

“This pump will push out up to 520 litres per second during a flood event and we expect it will provide safe passage for long and short-fin eels. It’s so big you could probably put a shark through one if we had them in our catchments.”

The Archimedes screw pump is the first of five pump upgrades for the Waikato region. The current infrastructure is due for replacement and the old flood pumps do not enable safe downstream passage for native fish.

The council received $4.48m in funding from Kānoa – Regional Economic Development and Investment Unit (formally the Provincial Development Unit) for the $7m upgrade project as part of the Government COVID-19 response to help stimulate the construction and environmental industries and economy. The project is expected to create 29 jobs over 3.5 years, including in the construction of purpose-built pump stations to house the new pumps.

FishFlow Innovation is a worldwide leader in innovative fish-friendly products for passage and deterrence.

Richard says a work colleague had visited the Netherlands and told him about the new technology.

“He said it might be worth checking out, so we had a look at it online and got in touch with the people. We soon realised that their technology might be what we were looking for, especially for the regulations of fish passage.”

The cost of the construction of the pump in the Netherlands and its transportation was about $150,000.

“In the long run, the screw pumps end up being cheaper than the old axial flow pumps because of the operational costs over their lifetime. That is the level of detail we look at – the whole-of-life cost. They’re light, so don’t require a lot of power to operate; they’re very simple so don’t require much maintenance; and another massive win is they don’t require a weed screen that needs regular clearing.”

Integrated Catchment Management Committee co-chair Stu Husband says the Dutch have been fighting floods and sea level rise for many thousands of years and their engineering expertise is well sought after around the world.

“They [FishFlow Innovations] say these pumps are 100 per cent fish friendly, which is something we here in New Zealand haven’t quite mastered yet for our mature longfin eel species, although there is some good work going into that.”

The regional council has about 182 pump stations in the Waikato which help protect our communities’ lives and livelihoods. It is currently developing a regional infrastructure fish passage strategy which will identify priority pumped catchments for fish passage and the appropriate measures to do so, such as fish-friendly pumps.

The council has also partnered with MacEwans Pumping Systems to develop fish-friendly impellors for retrofitting currently installed older pumps.