Fishscreen captures crowd at open day

Rangitata Diversion Race (RDR) Management Ltd chief executive officer Tony McCormick.
Rangitata Diversion Race (RDR) Management Ltd chief executive officer Tony McCormick.
Hundreds of people young and old took up the chance to walk in a dry section of the Rangitata Diversion Race and get up close to the new $17.2m fish screen system before it goes underwater.

The area will be connected to the main water race in May.

Rangitata Diversion Race (RDR) Management Ltd chief executive officer Tony McCormick said more than 500 people had registered to attend a five hour session on April 10.

"This is a fantastically unique opportunity to pretend you’re a fish and get right amongst the fishscreen," he said.

The fishscreen has been installed over the past year at the RDR’s intake at Klondyke where water is diverted from the Rangitata River for use by irrigation schemes, hydro-electric power and stockwater networks.

It is designed to keep fish, including young salmon, trout and natives, from being trapped in the main diversion race.

"The RDR quite fundamentally is the lifeblood of Mid Canterbury," Mr McCormick said.

"We provide water for irrigation for over 100,000 hectares; most of Mid Canterbury is irrigated off the RDR. We run along the top under the foothills there and provide water to three irrigation schemes and then there is also stock water we supply to the council and hydrogeneration at the end."

It’s a 365-days operation.

"There is an enormous amount of enterprise on the back of the water and the farming enterprise it supports in the whole Mid Canterbury region."

Crowds get up close to check out the fishscreen.
Crowds get up close to check out the fishscreen.
"It’s a project to protect the fisheries and to make sure the fish stay in the river where they are meant to be," he said.

Young fish swept into the intake are diverted by the fish screen back into the river to continue their life journey. There is also a channel at ground level for eels which swim along the bottom of the canal.

Local representatives from Iwi and anglers have been among those invited to special viewings of the fishscreen ahead of its operation. As well as representatives from Ashburton District Council (a shareholder in the company that owns and operates the RDR), schemes of other districts, other shareholders and school pupils.

It had impressed many, Mr McCormick said.

The fishscreen is made up of seven cylindrical spheres that rotate, and a portion of flat screen. Made of stainless steel sections are crafted in a ‘wedge wire’ grills pattern to prevent debris build-up, such as leaves and twigs from jamming in the grills. There is an external brush system to clean off any debris.

The shape of the fishscreen — like that of a missile with a rounded head — ensures smooth water flow, which is less turbulent for the fish and helps the screen work better.

It was manufactured by AWMA Water Control Solutions in Australia. It is a North American design adapted to the conditions of the RDR and to meet consent conditions. Covid disruptions had not affected supply timeframes.

As part of the monitoring process once the screen is operational, some fish will be caught at the out-take and assessed to ensure they have safely made the journey.

Nearly $3m had been spent on engineering design and management, which included computer modelling to ensure the fish screen would work as expected.

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