In July 2017, Canterbury’s regional council sent a compliance monitoring report to the South Island’s largest irrigation scheme, Central Plains Water.

The report, for the company’s water diversion on the Rakaia River about 8km downstream of the gorge bridge, offered thanks for complying with consent conditions “that have been monitored”.

“If you continue to fully comply with all conditions then the frequency of monitoring will reduce to the minimum set for the activity.”

The consent was for a fish barrier (also known as a fish screen), which is a way for irrigation schemes to co-exist with nature by ensuring river intakes don’t trap sports fish, like trout and salmon, and native species such as kōaro and eels.

The compliance report by the council, Environment Canterbury (ECan), noted Central Plains Water had consulted with ECan, Fish & Game, and the Department of Conservation in February 2017 on the fish barrier’s design and certification.

“A proposed fish exclusion monitoring programme needs to be submitted to Environment Canterbury by 22 September 2017.”

The Rakaia intake, and associated fish screen, started operating in September 2015, and consent conditions mandated a monitoring programme be conducted for the first five years of operation to test its effectiveness.

A January 2021 compliance monitoring report was devoid of thanks, and Central Plains’ consent was rated non-compliant.

When ECan’s compliance team visited Central Plains in September 2020, no monitoring programme of the Rakaia fish screen was in place, the report said, and nothing conclusive had been done to prove its effectiveness.

That’s not to say the irrigation company had done nothing.

ECan’s report said it made “several attempts” to initiate a monitoring programme, including submitting a draft monitoring methodology which was “later withdrawn because of health and safety concerns”.

The fish screen’s design was considered by ECan to be novel, “in that both its design and operational effectiveness are unproven”.

The scheme uses what are known as infiltration galleries. They’re made of loosely packed cobbles which prevent fish movement but allow the water to percolate into buried intake pipes. Fish are then swept into a diversion channel and back into the river. At least in theory.

A 2013 report prepared for Central Plains said infiltration galleries were a relatively new fish-excluding technology, and there hadn’t been extensive monitoring to confirm their effectiveness.

“Monitoring of galleries constructed to date has included the release of frozen peas and corn (as a model of juvenile fish) in front of the gallery, or the holding of dyed juvenile hatchery salmon in traps on top of the gallery, with monitoring to see if any passed through the gallery to the header pond.”

ECan’s 2021 monitoring report noted Central Plains had conducted a “peas and carrots” test at the Rakaia intake.

Rock infiltration galleries don’t meet three of seven guidelines for fish screens, the ECan report said.

“The operational effectiveness of the galleries is also considered to be unproven because they are not fitted with an effective self-cleaning mechanism to ensure their structure remains the same while in operation.

“Without an effective self-cleaning mechanism, the galleries will fill with sediment increasing through screen velocities over time.”

Considering the scheme had been operating for five years, an extension to the consent conditions wasn’t appropriate, ECan said. Central Plains’ non-compliance required “immediate action”.

Central Plains Water made a $6.8 million after-tax loss last year, on revenue of $39 million. It has long term debt of $305 million. Photo: Francis Vallance/Flickr/Creative Commons

The context to this saga is Canterbury’s status as a freshwater powerhouse. The region has more than half the country’s irrigation water and hydro storage.

Access to water for irrigation was at the forefront of John Key’s Government move, in 2010, to dismiss regional councillors and appointed commissioners. ECan appointee David Caygill said earlier this year the regime did far more for the environment than for farmers.

However, despite these changes, the region’s waterways are still degrading – with Ōtūwharekai/Ashburton Lakes a prime example.

Those convinced Key’s Government were intent on a water grab will point to Lake Coleridge, which now stores irrigation water, which is released down the Rakaia and taken by irrigation companies like Central Plains, thanks to an amendment to the river’s water conservation order.

Commissioners considering the amendment said of Central Plains’ fish barrier they were satisfied the management regime would reduce the potential extent of fish loss “to an acceptable level”.

ECan’s performance as a regulator has been heavily criticised, including for choosing not to publish a contentious, draft scientific report, leaked to Newsroom in 2021, which found the conservation order was being breached, and some consent conditions were being exceeded.

Last year, the council said systematic monitoring of water-take consents from the Rakaia was underway. That’s a departure from the norm, though, with ECan admitting this year: “Historically there has been very little dedicated water-take compliance activity undertaken on the Rakaia River, beyond that carried out in the ordinary course of compliance monitoring more generally.”

A fresh source of grievance with the regional council is its withdrawal from Environment Court proceedings it sought in February.

Not ineffective, just unproven

Central Plains chief executive Susan Goodfellow defends the company’s record – including a comment last year by her predecessor, Mark Pizey, the company was “of the view that they are in compliance with all the consents they hold”.

Goodfellow says the company has been monitoring its Rakaia intake but hasn’t been able to demonstrate the fish screen’s effectiveness.

“The results of the monitoring undertaken during this period, using the methodology available at the time, were inconclusive. 

“Please note that the results did not state that the fish screen performance was ineffective, rather, it was that we could not prove effectiveness.”

(But that’s exactly what the consent required: monitoring over the first five years of operation “to establish the effectiveness of the fish barrier in achieving the performance objectives specified.”)

Central Plains has developed a new monitoring programme, Goodfellow says, in consultation with NIWA (National Institute of Water and Atmospheric Research), and Fish & Game. A fresh consent application has been lodged – which mentions the company has also consulted with Te Taumutu Rūnanga and ECan.

The new application noted how Central Plains attempted to comply with the conditions of its existing consent.

In 2016, peas and corn were used during a trial as substitutes for live juvenile fish.

(In saying that, experts state “peas and corn do not reflect the behaviour of native fish”.)

ECan observed the trial and, upon receiving the results, said Fish & Game agreed to the method before the scheme was built, and there was no requirement under the consent to report the trial’s results.

In 2018, NIWA investigated what equipment could be used to assess the effectiveness of the fish barrier. “NIWA considered that a live fish trial was possible, but trapping could only cover a very small area of the canal so would be unlikely to provide much certainty.”

(A complication to excluding fish was the addition of stage two of the Central Plains scheme, which doubled the peak inflow rate from the Rakaia. The fish barrier was expanded with a third culvert and 12 infiltration galleries. Work was completed in 2018.)

The proposed new monitoring programme, detailed in a Tonkin & Taylor report, involves population monitoring at the so-called header pond; monitoring the fish bypass; and using baby peas and corn for “passive particle testing”.

A set time period hasn’t been proposed for the monitoring programme, but it has been suggested two years’ worth of data be collected. “This will enable a robust and thorough assessment of the fish barrier’s effectiveness.”

Acknowledging progress

Lyndon Slater, of North Canterbury Fish & Game Council, says it was a concern that testing the fish barrier’s effectiveness had been left so long but it’s satisfied Central Plains is now developing a monitoring regime.

“Fish screening is absolutely important.”

It was agreed when the consent was granted the fish screen would be effective, Slater says.

Central Plains might be paying for choosing an experimental design. “Theoretically there would have been options which may have been easier to assess compliance with.”

Checking the fish screen’s efficacy should be simple, Slater says: “Does it or doesn’t it exclude fish? Is it effective or not?”

Judith Earl-Goulet, ECan’s general manager of operations management, says Central Plains’ new consent application is being processed.

“While they are presently non-compliant, they are working towards resolving this through the above application with the intention of implementing the monitoring programme if and when the application is granted.”

Goodfellow, of Central Plains (CPWL), says the new consent seeks to “extend the period of monitoring” – which seems to jar with ECan’s compliance monitoring report from 2021, which said an extension wasn’t appropriate.

“Subject to approval from Environment Canterbury, CPWL intend to install the infrastructure required for the proposed new monitoring programme during the off-season (winter 2024).”

David Williams is Newsroom's environment editor, South Island correspondent and investigative writer.

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