Forest & Bird is unhappy about a proposed plan that would see Environment Canterbury's help irrigation company AIC stall minimum water flow rules on the Hurunui River.

A conservation organisation is taking legal action against Environment Canterbury (ECan) over its potential role in a plan that would allow an irrigation firm to delay introducing minimum water flows on the Hurunui River.

New rates of minimum flow were brought in by ECan five years ago as a long-term requirement under the Hurunui and Waiau River Regional Plan (HWRRP) to safeguard the river's ecological needs.

But Amuri Irrigation Company (AIC) wants to delay complying with the measures until 2025 while it investigates building a dam to help irrigation in North Canterbury.

IAIN MCGREGOR/STUFF The Hurunui in North Canterbury attracts thousands of people, many of whom, like Pete Dormer, left, and Guy Higginson, enjoy fishing from its stony banks.

Forest & Bird is furious about the potential delay – and is concerned about the possibility of ECan entering into a "partnership" with AIC, saying it would be "unlawful" and against the council's role as an independent regulator.

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The organisation is taking ECan to the Environment Court to ask a judge to decide on the legality of any support from the council for the delay and its role in any potential partnership with AIC – the details of which are not yet clear.

IAIN MCGREGOR/STUFF Conservationists Forest & Bird are concerned about Environment Canterbury's role in plans to delay bringing in minimum water flows on the Hurunui River.

Forest & Bird regional manager Jen Miller said: "We say that ECan is simply not acting out its statutory responsibilities to implement the minimum flows in its own plan, but instead is entering into side agreements with an irrigation company.

"We consider that to be inappropriate and not something that it is able to do and that's what we are seeking some sort of declaration from the court about."

In an affidavit submitted to the court, Miller cited examples of side agreements between councils and consent holders failing in the past, saying: "The concern is that the council will end up entering an agreement with AIC, but the agreement will be unenforceable … and AIC will not be required to keep its side of the agreement."

IAIN MCGREGOR/STUFF Irrigation firm AIC wants to put off bringing in environmental measures on the Hurunui - and ECan could help it.

Miller also argued that a side agreement would keep the public in the dark about its details and suggested it would effectively bind any future councils to any deal that is made, hindering ECan's ability to review consents or change the agreement.

"Forest & Bird has been critical of the way in which the governance arrangements have allowed for increases in irrigation and degradation of water quality.

"The proposed contract or side agreement will likely have effect for many years, possibly until 2025.

"This will preclude a fully democratically-elected council from reviewing the consents. Put another way, the non-democratic council is seeking to bind a fully-elected council to not reviewing the consents."

AIC wants to delay introducing minimum water flows because it says doing so now would impose significant financial costs on both the company and the wider farming community.

Instead it is offering to fund a host of environmental measures while it examines the dam's feasibility, including improving wetlands, habitats for riverbed birds and reducing nitrogen run-off into the rivers.

If the delay is approved it would mean the requirements of the HWRRP would not have been met during the entire lifespan of the region's 10-year plan.

An ECan spokeswoman said: "ECan is aware of the Forest & Bird application to the Environment Court. We are not commenting at this time as the matter has been filed with the court."