We have filed proceedings against Environment Canterbury challenging its 2021 decision to grant a nitrogen discharge consent to MHV Water Ltd.

MHV Water Ltd. (MHV) operates the largest irrigation scheme in the lower Hinds/Hekeao Plains area, in south Canterbury. They currently hold a discharge consent, issued by Environment Canterbury (ECan) which allows MHV farm-shareholders to discharge contaminants, principally nitrogen, onto land in circumstances where it may enter groundwater. The contaminated groundwater flows towards the coast, emerging in the spring-fed lowland waterways between the Hakatere/Ashburton River and the Rangitata River.

MHV’s shareholders collectively farm more than 58,000 ha and were permitted to discharge up to an estimated 4,467,000 kilograms of excess nitrogen onto the land, in the 2022-23 year.[1]

When ECan issued MHV’s consent, it was already well understood that a history of intensive agriculture in the catchment had significantly increased nitrate contamination in the receiving waterbodies.

We allege that ECan made multiple errors in the course of considering MHV’s consent application, including a failure to properly take into account the potential effects of the discharges on local drinking water supplies.

This case builds on our successful challenge to ECan’s decision to grant a consent to Ashburton Lyndhurst Irrigation Limited (ALIL).

In addition to challenging ECan’s decision to grant the consent to MHV, we are also challenging ECan’s failure to take steps to revoke MHV’s consent after the judgment in the ALIL case was released. We allege that the MHV consent was made based on the same reasoning that was found to be unlawful in the ALIL case.

[1] Estimate calculated using v6.5.2 of OVERSEER.

Why did we take this case?

Water is a public good. No one automatically has the right to pour contaminants or waste into water – or onto land, in circumstances where it may enter water.

ECan should be guaranteeing communities have access to clean drinking water and protecting precious freshwater ecosystems.

Yet many of Canterbury’s aquifers and lowland waterways are already degraded, commonly by pollution allowed from large areas of intensive farming. Between 1990 and 2022, dairy cattle numbers in Canterbury increased ten-fold (1009 percent) from 113,000 to 1.3 million.[1] The Hinds/Hekeao Plains catchment will be dealing with the problem of historical and ongoing nitrate pollution for years to come.

We need ECan to show it is making decisions that will protect the health of our waterways.

[1] Stats NZ “Livestock numbers: Data to 2023”. Updated 12 December 2024. Accessed 16 January 2025. https://www.stats.govt.nz/indicators/livestock-numbers-data-to-2023/

Case timeline

August 2024 - Filed for judicial review

Awaiting a date for court hearing.

We have applied for judicial review of ECan’s decision to grant the MHV discharge consent on the same two grounds as in our successful ALIL case.
We also allege that in granting the consent to MHV, ECan failed to take into account the potential effects of the nitrogen discharge on drinking water supplies.
Notification
Neither community drinking water operators nor owners of private drinking water wells were notified by ECan about the consent application.
We allege that the failure to notify meant ECan did not receive key information that it needed to fully understand the effects of the proposed discharge (additional, ongoing nitrate pollution of groundwater) on community and private drinking water supplies. ECan also did not have information about the costs for drinking water suppliers to mitigate those effects.
Parallels to ALIL case
Previously managed under a joint discharge consent, ALIL and MHV each applied for new nitrogen discharge consents in 2018.They were granted consents in separate decisions by the same ECan Commissioner in 2021.
In both cases, the Commissioner found that the nitrogen discharges from past and current farming practices had caused significant adverse effects on aquatic life.
While the Commissioner acknowledged that section 107(1) of the Resource Management Act 1991 (RMA) prohibits councils from granting discharge consents if the discharge is likely to give rise to “any significant adverse effects on aquatic life”, the Commissioner granted the consent in both cases based on ALIL and MHV’s respective commitments to staged nitrogen reductions. The Commissioner believed the commitments would reduce and with time, remedy the cumulative effects on aquatic life.
In August 2022, we filed judicial review proceedings in relation to the ALIL consent and in March 2024, the High Court released its judgment, which ruled that ECan’s decision to grant the discharge consent to ALIL was based on:
- A material error of law in its approach to s107 of the RMA; and
- A failure to consider the relevant provisions of the New Zealand Coastal Policy Statement and the Canterbury Regional Coastal Environment Plan, which were found to be mandatory statutory considerations in that context.
As MHV’s consent was granted on the basis of almost identical reasoning in relation to s107 of the RMA, we asked ECan whether it would revoke MHV’s consent after the ALIL Judgment was released but the council refused to do so.
We are challenging ECan’s decision not to take any steps to revoke MHV’s consent after the High Court decision in the ALIL proceeding.
What is nitrate pollution and how does it affect water quality?
Plants and animals need nitrogen to grow. Nitrogen is a limiting nutrient which means that its supply determines the growth of organisms. Synthetic nitrogen fertiliser is applied to pastures to feed more cows on a given area of land. Cows then contribute to nitrate pollution through their urine, which is rich in nitrogen. Once excreted as urine, the excess nitrogen that can’t be taken up by plants can leach through the soil. This wasted nitrogen flows into groundwater and surface waterbodies.
High levels of nitrogen in waterways can lead to excessive algae growth and oxygen depletion. This process, known as eutrophication, harms aquatic ecosystems by creating "dead zones" where fish, insects and other wildlife struggle to survive. Aquatic invertebrates and fish can also experience chronic toxicological effects from high nitrate levels, impairing the growth and reproductive ability of sensitive species and thereby constraining species diversity and abundance.
What are ELI’s concerns about drinking water?
Most of the people living in the Hinds/Hekeao Plains area rely on groundwater as their source of drinking water. In 2020 ECan groundwater scientists estimated that 62 percent of private drinking water wells in the area may already exceed the maximum acceptable value (MAV) for nitrate.[1]
Elevated nitrate levels in drinking water sources can pose serious health risks, particularly to infants. The New Zealand Drinking-water Standards set the current MAV for nitrate in drinking water at a level intended to prevent methemoglobinemia or "blue baby syndrome" in infants.
In recent years, there has been research suggesting that nitrate levels lower than the MAV might be associated with increased risk of other health problems, including adverse reproductive outcomes and bowel cancer. While a 2022 report from the Office of the Prime Minister’s Chief Science Advisor concluded:
“the evidence base is not conclusive”, it recommended that “[e] volving evidence on a possible relationship between nitrates and bowel cancer, reproductive outcomes or any other adverse health events should continue to be monitored in New Zealand by the Ministry of Health.”
What is section 107 of the RMA, and is the case affected by the Government’s change to it?
Section 107 of the Resource Management Act (RMA) is a key environmental baseline to protect water quality. It prohibits granting resource consents for activities that would discharge contaminants into water if they cause significant adverse effects, such as foaming, discoloration, or harm to aquatic life. Until recently, exceptions could only be made if the effects are temporary or if the applicant demonstrates exceptional circumstances that justify the discharge.
Following our successful ALIL case, the Government, at the behest of ‘big farm’ lobbyists, passed a rapid law change to amend section 107 of the RMA. The Government evaded usual law-making process, removing any opportunity for the public to have a say.
The resulting subsection added by the Government, s107(2A), creates a new exception that will allow a consent to be granted despite existing significant adverse effects on aquatic life – so long as the consent includes conditions that the consenting authority is satisfied will contribute to a reduction of those effects over the lifetime of the consent.
Our challenge to the consent granted to MHV will be decided based on the law as it was when the consent was granted in 2021. If ECan’s decision then was contrary to s107, asw e are arguing, then the court may decide to overturn the consent and send MHV’s application back to ECan to be reheard. ECan would need to apply the newly amended s107(2A) if reconsidering MHV’s application.
Section 107 remains a critical part of the RMA, as it has been for the past thirty years. While s107(2A) now provides a potential pathway for councils to give consent where significant adverse effects on aquatic life already exist, councils will need to proceed very carefully in choosing whether to exercise their discretion to permit discharges that will prolong adverse effects on aquatic ecosystems that are already in crisis.
We are also arguing that ECan made other mistakes when granting the MHV consent. If the court agrees, then ECan would also need to apply a different approach to various policies concerning the coastal environment and to effects on community and private drinking water supplies if it had to rehear MHV’s application.

[1] Tregurtha, J. and Aitchison-Earl, P. (18 May 2020). “Memo: What % of private drinking water wells, in Ashburton-Rakaia area, are abstracting water with nitrate above the MAV?”. Obtained from ECan via a LGOIMA request.
Statement of claim
Mega-irrigation schemes back to court, as Canterbury water wars heat up | The Post — January 2025