A huge Canterbury farm consent will likely miss water quality targets – but “science advice is not the only consideration”. David Williams reports

A quiet battle is being waged over a consent for a huge irrigation scheme in one of Canterbury’s worst areas for nitrate contamination in groundwater.

For months, experts and scientists have fired reports back and forth, providing evidence and counter claims, with legal opinions backing certain positions. At the moment, it boils down to this: an independent commissioner appointed by ECan, the regional council, will determine whether MHV Ltd gets a nutrient discharge consent for its shareholders, who farm an area, south of Ashburton.

And the public – other than “affected person” Te Rūnanga o Ngāi Tahu – won’t have any input.

The irrigation company’s chief executive, Melanie Brooks, says the public already had input into what’s known as plan change two of Canterbury’s land and water regional plan, which was notified in 2014 and became operative in 2018.

“We had four years of public consultation around plan change two, so four years of opportunity for the public to be party to that discussion, and it was extensive.”

Brooks says MHV will require its farmers to reduce nitrogen loads, and if water quality deteriorates on certain measures, including nitrates, it will need to take action. “Yes there will be some challenges, but it is achievable and I believe that we can do it.”

This quiet battle is about to get a bit louder, however.

Matamata environmentalist Angus Robson has organised a public meeting in Christchurch tonight – at Burnside High School’s Aurora Centre, at 7pm – to bring the consent to the public’s attention, and encourage people to lobby ECan. He says the regional council barred the public from submitting on the MHV consent in a flawed decision dating back to when government-appointed commissioners were in charge of ECan.

“We’ve got a giant mistake going on here,” Robson says. “We can’t solve it all with the wave of a wand, but we have to start dealing with it – and the way to start dealing with it is not to renew a consent that causes the problem in the first place. It’s to say, we’re not going to keep renewing these consents and still try and think we’re solving the problem. Let’s get serious about the problem.”

(Other big irrigation schemes, Barrhill Chertsey and Ashburton Lyndhurst, have applied for similar consents.)

Let’s rewind the clock to 2010, when Environment Minister Nick Smith sacked ECan’s councillors for failing to create a water plan. Many believed it was a water grab, using government-appointed commissioners to bypass the existing urban-rural divide among councillors and give irrigation interests access to water.

Collaboration did happen. Water committees were established to see if a community consensus could be found on water use. (Some environmental groups walked away, claiming their views were given just token consideration.) But by contrast, there’s the non-democratic decision in plan change two.

The public should get a say in the MHV consent, Robson says, because it has long-term implications for their health and environment, based on nutrient discharges by farmers in the scheme.

Tonight’s meeting comes at a critical time for our international reputation. Australians will soon be let back into the country, quarantine-free, just weeks after an ABC Foreign Correspondent programme laid bare the “shocking reality” about our polluted waterways. According to a freshwater report released last year, the vast majority of rivers in urban, farming and forestry areas are polluted.

Will the economic benefits of the MHV consent trump environmental damage? ECan-appointed hearing commissioner Sharon McGarry is being told science isn’t the only consideration.

A patchwork quilt of irrigated farmland on the Hinds/Hekeao Plains. Photo: Google Earth

By anybody’s estimation, MHV’s scheme is huge.

Created in 2017 by merging the Mayfield Hinds and Valetta schemes, between Canterbury’s Hakatere/Ashburton and Rangitata Rivers, its “command area” is 138,000 hectares, but the actual farmed area is 58,306ha – about two-and-a-half times the size of Abel Tasman National Park.

Nitrogen losses – defined as nitrogen discharged below the root zone of plants, the excess from sources such as cattle manure, fertilisers, and dairy shed effluent – are estimated to be 6000 tonnes a year, or about 16 tonnes a day.

This in an area that’s mostly a water-quality “red zone”, where nitrate-nitrogen levels in an estimated six out of 10 private domestic water bores are above acceptable levels.

(Nitrate’s a compound formed when nitrogen combines with oxygen. It’s highly soluble in water, which means it easily flushes through soil to groundwater.)

There are standards for nitrates in drinking water because of risks (when nitrate is converted to nitrite by bacteria in the gut) to babies of blue baby syndrome – as well as environmental damage. There are other potential health effects, including evidence in overseas studies indicating a link between high nitrates in drinking water and colorectal cancer.

Dr Tim Chambers, a lead author of a preliminary study which found up to 800,000 New Zealanders were exposed to potentially harmful nitrate levels in drinking water, says: “The latest studies that have come out are indicating there could be some health impact from nitrate contamination. The better studies, done more recently, are also those studies that have shown a stronger association.”

On the face of it, ECan has been dealing with high nitrates. In 2012, it imposed “strict” pollution limits on Canterbury farmers via its land and water regional plan. The caveat was, however, levels may rise “for a time” because of the time it takes for pollution to flow through the groundwater.

Under plan change two, MHV was allocated a potential new irrigation area of up to 7817ha.

Since 2013, the scheme’s irrigated area has increased 6200ha and there’s been a 15,000ha-plus shift to using centre pivots. At the same time, the use of nitrogen mineral fertilisers has increased in the Ashburton district, and dairy farming has expanded. Ashburton now has the second-highest number of cows for a district, at 364,384, behind Southland’s 441,740.

MHV’s own expert, Dr Glen Treweek, says modelled nitrogen concentrations flowing in MHV’s “soil drainage waters” have increased 40 percent over the 2009-2013 baseline period.

(However, the new consent would cap nutrient discharges, and there’s thought to be limited scope for further land use intensification and new irrigation. Also looming is a synthetic fertiliser cap imposed by the national environmental standard for freshwater management. Environmental lobby group Greenpeace has called for a ban on chemical nitrogen fertilisers, which Federated Farmers says “would erase one of the greatest scientific and humanitarian breakthroughs of the twentieth century”.)

Brooks, the MHV chief executive, says the increase in nitrogen drainage concentrations has been one of the unintended consequences of the push for more efficient irrigation. Nutrient loads across all MHV farms are required to decrease by 25 percent – compared to a property’s nitrogen discharge allowance – by 2030, when this proposed new consent would expire.

ECan’s experts weigh in

In a “coarse estimate”, ECan’s land resources expert Ognjen Mojsilovic says MHV has probably already achieved modelled reductions of 10-to-15-percent of nutrient loads – but there’s been no corresponding drop in drainage nitrate concentrations. He puts that down to irrigation efficiency, the high proportion of dairy land, and new irrigated land since 2013.

Uncertainties remain over just how much a reduction of nutrient load, through MHV’s audited self-management system with farm environment plans, will lead to a drop in drainage nitrate concentrations.

In her report, Shirley Hayward, ECan’s principal scientist for water quality and ecology, says there’s a high level of uncertainty the proposed nutrient discharge consent will “actually contribute to reducing nitrate concentrations in the surface waterways of the Hinds/Hekeao Plains”. She notes nitrate concentrations in coastal spring-fed streams and drains are well above targets in the land and water plan, “and continue to show deteriorating trends”.

The annual median nitrate-nitrogen concentration in shallow groundwater was 11.9 mg/L in 2018/19, compared to the 2035 target of 6.9 mg/L.

Indicators for aquatic macroinvertebrates (the likes of mayflies, caddisflies, true flies, snails) have shown a general decline over the past two decades, impairing the growth and reproductive ability of sensitive species, and constraining their diversity and abundance.

ECan groundwater scientists Matt Dodson and Lisa Scott express similar concerns to Hayward. “Unless there is a substantial reduction in the nitrogen inputs to farm systems, the net effect on groundwater nitrate-nitrogen concentrations is that they are likely to remain high.

The uncertainties have led to calls for extra management actions to protect community drinking supplies for the Hinds township and Carew School.

MHV is relying on its farmers adopting so-called good management practices, including improved fertiliser use, and the use of groundwater recharge and stream augmentation, to bring down nitrate levels.

But nitrate-nitrogen in groundwater is yet to peak, Dodson and Scott suggest. To reverse high nutrient concentrations, the amount of nitrogen entering the groundwater system will have to “drastically and permanently reduce”.

A submission from Te Rūnanga o Ngāi Tahu says: “Ngā Rūnanga recognises that while the land practices in the MHV Water Limited command area have and will continue to have impacts on the health of freshwater, Ngā Rūnanga accept that MHV Water Limited has committed through its consultative process on the resource consent to work in a collaborative manner and incorporate the values and practices of Arowhenua into new farming trials and practices.”

“We acknowledge that science advice is not the only consideration in plan development.” – Gillian Ensor and Bianca Sullivan

Under the proposed consent, if water quality deteriorates MHV must prepare a remediation and response plan in consultation with Te Rūnanga o Arowhenua.

But there’s no requirement to improve water quality, say Dodson and Scott, and it’s unclear what action would be taken, even if groundwater quality remains stubbornly poor.

Brooks clarifies the “key actions” relate to when and how much water, effluent and fertiliser are applied. These actions “will drive reductions in [leaching] concentrations and improve outcomes”.

But not quickly, it seems. In a letter to commissioner Sharon McGarry, MHV lawyer Ben Williams, of Chapman Tripp, says a remediation and response plan would be triggered in year five of the consent, and given the long lag times in groundwater “MHV is doubtful that a useful response regime for groundwater could be developed in the timeframes available”.

Brooks remains bullish. “Any deterioration from where we are now is not heading in the right direction, so whilst we may not formally, as part of the consent conditions, need to immediately put a response and remediation plan in place, we don’t have any option but to.

“We recognise that if we don’t see improved water quality outcomes that we’ve got such a short window to be able to demonstrate this, that it’s as simple as we don’t have an option.”

Planning report writers Gillian Ensor and Bianca Sullivan, in their report to McGarry, state the irrigation scheme’s proposed mitigation is likely to improve groundwater quality, and is “consistent” with requirements in the land and water plan. However, “groundwater targets are likely to take longer than anticipated to be met”.

(MHV admits water quality protection and improvement may not be met “in the short to medium term”, but this failure must be balanced “against the objectives that are focused on enablement, and the wider policy and rule framework that enable schemes and puts in place a framework that contemplates improvement over time”.)

Further on, the Ensor and Sullivan planning report, says, more definitively, “the science is telling us those concentration targets may/will not be achieved”. It goes on: “We acknowledge that science advice is not the only consideration in plan development and suggest that this inconsistency is more appropriately addressed by the next plan process rather than through this resource consent application.”

Dodson and Scott suggested MHV meet interim water quality targets in its environmental management plan, to ensure an improving trend.

However, Ensor and Sullivan said there was no merit in doing that when targets weren’t required to be met, and penalties wouldn’t be handed out for failing to achieve them. Also, the targets may well be “unobtainable by the specified dates”.

MHV’s environmental management plan won’t be finalised until six months after the consent’s issued – so Scott and Dodson were unable to comment on the likelihood it will lead to improvements.

Turning to the positive

There are positive effects of granting the consent, of course. Planners Ensor and Sullivan say they include economic growth, employment, and environmental benefits “because MHV encourage continuous improvement of on-farm practices through ongoing education and support”.

The irrigation scheme’s been proactive in trying to address water quality issues, the report says, through investment in aquifer recharge, stream augmentation and building wetlands. “The alternative to the scheme managing nutrient discharges is for these to be managed by individual farmers through land use consents to farm.”

MHV was acknowledged in the report for reducing its consent term to 10 years – although that was done to ensure it didn’t conflict with the new environmental standard for freshwater – and for adding monitoring and reporting requirements. (It’s unclear if MHV farmers will seek separate consents under a new national environmental standard for freshwater, as the scheme believes its regime is more stringent than the standard.)

While Ecan’s land and water plan seeks to achieve improved water quality in the Lower Hinds/Hekeao Plains, Ensor and Sullivan give MHV’s consent a pass: “We doubt that the impact of improved irrigation efficiency, being increased discharge concentrations, would have been fully understood and considered at the time.”

Overall, the proposed MHV consent is “consistent with the framework” to manage the effects of nutrient discharges from farming, the planning report says – and the proposed activity “should result in some level of water quality improvement”.

If certain issues raised by ECan’s experts are addressed, the consent should be granted, Ensor and Sullivan recommend.

(ECan consent planning manager Aurora Grant says: “The applicant’s right of reply [to a minute sent out by McGarry] has been received by the commissioner, and the hearing will be closed once she has considered it.”)

MHV’s evidence for the consent highlights the existing issue with nitrates in groundwater across the Hinds/Hekeao Plains. Data from 21 bores showed 16, including two deeper than 40m, exceeded the maximum acceptable value for nitrate-nitrogen in drinking water of 11.3 milligrams per litre. The highest reading was 25.6 mg/L.

However, recent publicity about the consent has frustrated MHV boss Brooks, who says it’s a “mistruth” the scheme is one of the country’s “biggest polluters”. “It’s hard to hear that, looking at all the work doing trying to make a difference, all the engagement with different parties.”

Managing nutrients collectively might lead to “big numbers” of nitrogen losses but it’s an effective way to improve water quality, she says. (ECan’s experts might disagree with that sentiment.)

Not all MHV farmers are “on board” with its new regime, Brooks says, but the majority of them are. “Because it’s a catchment, and there’s that peer responsibility, we’re actually seeing some really cool changes and I’d love for that to be celebrated and to help continue the momentum.”

She believes its consent rules should be a model for diffuse nutrient management across the country. “We think that they are robust and they will actually drive change.”

The question is – and this is something that’s almost certain to be raised at the Burnside High’s Aurora Centre tonight – how robust can a consent be if the proposed mitigation measures aren’t strong enough to achieve water quality targets?

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

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