Worried about excess nitrogen in water, Cantabrians are taking matters into their own hands. David Williams reports

The indicator clicks and Peter Trolove pulls his ute to the side of the road in the rural Selwyn district, south-west of Christchurch. He’s not far from his house at Rakaia Huts on a sunny Wednesday morning in May.

“This is the first one on the run; this is Jollies Brook.”

In the back of the ute, Trolove fishes around a chiller bag for a specimen pottle, a fresh label and marker pen. He marches to the waterway holding a long, thin plastic pipe with a wire basket for the pottle – “my patented water gatherer, so I don’t get wet feet”.

Trolove, president of advocacy group Federation of Freshwater Anglers, is collecting samples to test for nitrate, a voluntary monthly task he’s done for the last two years, using a nitrate tester bought by a pub charity grant.

He expects Jollies Brook to have low concentrations: “This should be good because it’s still connected to the Rakaia.”

Peter Trolove samples the Selwyn River at Chamberlains Ford. The result is a very high 9.83mg/L. Photo: David Williams

The retired veterinarian has cut an unlikely figure – mixing with young campaigners and urban types, often – while speaking at a meeting about a huge Canterbury farm consent, and a rally outside the offices of the regional council, ECan.

His concern was sparked by rapid changes he’s seen in rivers he’s fished for years, and the near disappearance of the native Stockell’s smelt over less than a decade.

“I’ve got self-interest – I’m a bloody fisherman, I want those smelt back. I want water put back in the bloody braided rivers so that they can function as braided rivers.”

What has happened to the rivers? He blames the last 30 years of industrialised farming – intensive, irrigated farming, primarily dairying, on Canterbury’s plains. “The nitrate leaching is huge.”

Fish are now absent from many stretches of lowland rivers fed by aquifers, such as the Selwyn and the Hinds, he says.

“I believe that’s because the nitrate levels are so high that the vulnerable egg and fry life-stage of the trout can’t survive. The levels have gone beyond causing harm through macrophytes and changing the oxygen level, it’s straight-out, direct toxicity – they just can’t live.”

Trolove is right about Jollies Brook. It registers 0.61 milligrams per litre of nitrate-nitrogen – well below the World Health Organisation’s (WHO) maximum allowable value for drinking water of 11.3mg/L.

But the same can’t be said for others on the roster of sampling sites, including Ellesmere Speedway’s well (10.6mg/L), Ellesmere Golf Club (9.89mg/L) and the Selwyn River at Chamberlain’s Ford (9.83mg/L).

Back at Rakaia Huts, the samples are put to the test. Photo: David Williams

Drinking water wells have shown high nitrate levels too, sparking concern in certain communities. Federation of Freshwater Anglers and Greenpeace have taken Trolove’s nitrate tester around the province so concerned residents can test their water.

Scientific understanding has improved in recent years. A 2018 Danish study found an increased risk of colon and rectal cancer from high nitrate-nitrogen concentrations (below the maximum allowable value, or MAV) in drinking water. Nitrate in drinking water has also been linked to premature or underweight babies.

That might raise questions about the WHO guidelines’ relevance. The nitrate MAV was set to protect bottle-fed infants from blue-baby syndrome, methaemoglobinaemia, which emerged in 1945. The guideline has been mentioned in WHO documents for decades.

(The MAV is based on no significant health risks to a person weighing 70kg who drinks two litres a day from that water supply for 70 years.)

Local authorities in New Zealand are watching and waiting, it seems. Waiting for the Ministry of Health, or new regulator Taumata Arowai, to act, or for WHO to change its guidelines.

Selwyn’s council posts its annual nitrate tests for drinking water on its website. If a level is greater than half the MAV, as five water sources are, testing moves to monthly.

(Dr Tim Chambers, a senior research fellow at University of Otago, Wellington, says nitrate contamination data is limited due to a lack of regulation, something he hopes Taumata Arowai will change by making testing and reporting mandatory.)

Sign of the times along the Selwyn River, at Coes Ford. Photo: David Williams

Selwyn Mayor Sam Broughton says there’s “ongoing debate” among health researchers on the health effects of nitrate in water. “I support calls for more research on the possible links between nitrate concentrations and human health to ensure the standards we have to meet are safe,” he says via email. “However it’s the Ministry of Health’s role to undertake research and revise or set drinking water standards.”

Ashburton council’s response has been to spend $140,000 on a project called managed aquifer recharge – which adds water to the groundwater system to try and lower nitrate in lowland streams and shallow bores. As for the Danish study, Neil Brown, Ashburton’s Mayor, says: “I’m not a scientist so I don’t know about that.”

ECan groundwater science manager Carl Hanson says water users are notified when concentrations are above the MAV, and it publishes risk maps showing areas with high nitrate concentrations in groundwater.

“We have been working with our communities to set limits on nitrogen losses from farming and other land uses, and to improve farming practices to reduce nitrogen losses.

Asked if ECan can provide examples of its actions or policies leading to a decrease in nitrate levels, Hanson says: “We expect it will be many years before land use changes made today result in clear decreases in nitrate concentrations.

Newsroom asks questions of Dr Cheryl Brunton, Canterbury’s medical officer of health, and she refers us to the Ministry of Health, as the current drinking water regulator. That’s a less forthright stance than her predecessor, Alistair Humphrey, who two years ago called for research to be undertaken into whether Canterbury’s drinking water increased the risk of bowel cancer.

Coes Ford, across the Selwyn River, is another nitrate hotspot. Photo: David Williams

Some aren’t waiting for the science to settle or for authorities to move.

Christchurch couple Kevin Dunn and Sue Hall moved to Kirwee, about half an hour’s drive west of the city, near Darfield, in 2016.

(Kirwee, surveyed in 1877, was named at the suggestion of retired Irish army officer Colonel De Renzie James Brett, a pioneer of Canterbury’s stock water races. The town’s main intersection was known as Brett’s Corner for years.)

“We didn’t know anything about nitrates when we moved here,” Sue says. But the more they read about it the more concerned they became.

“We just felt that the whole thing was going to mud, basically,” Kevin says. “We’re in a situation where there’s a real issue with nitrates, nobody’s going to do anything about it, they can’t reach agreement on anything, and nobody’s going to take responsibility.

“So we thought well the only option really is for us to do it ourselves.”

They’ve installed a $5000-7000 system, including an ion exchange to strip out nitrate. Sitting in a dedicated shed, the system also has a carbon filter, an alkaliser, two fine-particle filters, and a UV sterilisation tube.

In March of this year, Selwyn’s council reported the nitrate level in Kirwee’s drinking water at 5mg/L, from a well 115m deep. When the water emerges from Dunn and Hall’s system it’s 0.5mg/L.

“At least we know we’ve got clean water,” says Kevin, who has an undergraduate degree in chemical engineering.

Dunn and Hall discuss their system with other people in the area but are careful not to “go out there campaigning”. “It’s very much over to them,” Kevin says. People don’t know what to believe, he says, so it’s hard to expect people to spend $1000 or more for an all-in-one unit to remove nitrate when they’re not sure.

(A woman in Temuka, South Canterbury, paid $1500 for a reverse osmosis filter which reduced nitrate from her drinking water bore from 10.6mg/L to 0.84mg/L.)

Dunn and Hall’s view of councils is they have a high responsibility to provide clean drinking water but are ducking the issue. “They’re hiding behind the 11.3mg/L,” Kevin says. “That’s it in a nutshell.”

Dark, slimy mats of cyanobacteria can be harmful to people and are extremely toxic to dogs. Photo: David Williams

John Sunckell is an ECan councillor who owns a 600-cow dairy farm at Leeston, 40km south-west of Christchurch. He says intensive farms have environment plans, and are “giving effect” to rules about nitrogen losses.

“A bunch of work’s happened, I guess, over the last eight or nine years to put in place plans and look to remediate the issues that we have.”

That said, he says it’s a long game – “20 to 30 to 40 years” – to get nitrate levels “back to where we need to be”.

Sunckell’s been on the Selwyn-Waihora zone committee – part of the Canterbury water management strategy, a province-wide attempt to get communities to collaboratively set nutrient limits for waterways – since its inception. (In 2018, lobby groups Forest & Bird and Fish & Game walked away from the zone committees, saying their views were only given token consideration.)

The magic number for Selwyn-Waihora, near Sunckell’s farm, is 6.9mg/L. That’s a nitrate-nitrogen target for groundwater-fed streams at the bottom of the catchment, measured as an annual median. All other river types are 1mg/L. To make matters more complex, the limit for groundwater in the zone’s shallowest wells is 8.5mg/L, measured as a five-year annual average.

But the targets are not lines in the sand. In fact, it seems they’re easily washed away by nutrient-rich water. Asked what happens if a limit is breached, ECan science director Tim Davie says: “We will then know that more work is needed to reduce nitrogen losses from farms in the zone.”

Sunckell explains Canterbury’s plains have been farmed for 150 years, and more intensively over the last 30 years. There’s plenty of nutrients “in the post”, he says, that has been put into the “receiving environment” and is yet to flow through to water. Reducing nitrogen losses from farms – through better management, fewer animals, and less fertiliser leaching – won’t be felt for many years, he says. “It’s not an immediate thing; we can’t just turn the tap off.”

“To get to any of those numbers we effectively need to take all production agriculture off the plains.” – John Sunckell

The 6.9mg/L limit is a “practical and pragmatic approach”, Sunckell says. The majority of farms have to get “very close” to that number today, he says. “But it’s also a practical application of being allowed to maintain farming of any sort upon the plains.”

So, nitrate pollution is just a fact of farming and people just have to accept it?

“In part, yes,” Sunckell says, while pointing to the zone committee’s nitrate limits and the fact farmers are reducing nitrogen losses.

The debate over nitrate in water is also taking place nationally. Under a new national policy statement brought in last year, farmers are meant to be working toward a national bottom line for nitrate of 2.4mg/L – although the target won’t take effect until 2024 and there’s no set time to achieve it. The limit isn’t as strict as it could be as Environment Minister David Parker deferred for a year the proposed introduction of some measurable nutrient limits.

Advice from the majority of scientists was for a nitrate limit of 1mg/L, something environmental groups are now pushing for. (This limit is measured as “dissolved inorganic nitrogen”, or DIN. Davie, the ECan science director, says nitrate-nitrogen and DIN are likely to be the same in streams. “The other components of the DIN calculation, nitrite and ammonia, are usually undetectable in surface water.”)

This is a big gumboot step too far for farmers.

Following the apocalyptic line he gave the ABC Foreign Correspondent TV programme, Sunckell says it’s impossible for farms to reach 2.4mg/L, let alone 1mg/L. “To get to any of those numbers we effectively need to take all production agriculture off the plains.”

Tools of Peter Trolove’s trade, of sampling streams, rivers, lakes and wetlands. Photo: David Williams

Dr Jenny Webster-Brown was part of the science and technical advisory group on freshwater reforms. A former director of University of Canterbury’s Waterways Centre for Freshwater Management, she is now director of the Our Land And Water national science challenge.

Canterbury, as well as Hawke’s Bay and parts of Southland, are going to find it difficult to meet nitrate waterway limits, Webster-Brown says. She understands why regional councils will be nervous, as they have few levers to achieve them.

However, she believes limits need to be set based on the best scientific evidence, to restore water quality. A level of 2.4mg/L is based on toxicity – “how much nitrate does it take to kill fish, basically” – while 1mg/L is based on protecting the whole ecosystem from over-nutrification, which produces algal growth.

Harking back to high nitrate in drinking water, Webster-Brown says they are part of the same problem. She adds: “That legacy is going to be very hard to turn around in the near future.”

It’s also something she thinks is hard to pin on the Government, as all governments set their nutrient limits for drinking water based on WHO recommendations. “Until that changes, we’re not going to get a change in the drinking water limit.”

Back in the Selwyn district, Trolove, of the Federation of Freshwater Anglers, proves he’s not anti-farmer. He points to a huge shed, used for keeping cows off paddocks in winter.

“A number of these farmers have done this because they know their social licence to pollute is not going to go forever.” These environmentally conscious farmers are the “realists”, he says. The others he writes off as “entitled”.

Trolove spends hours sampling waterways, testing for nitrate, and up the results. Just what does he hope to achieve? Well, Canterbury is the frontline, he says, but there are lessons for the rest of the country.

“I see that we’ve lost our water – this has happened; we’re not going to put it back. But when they want to do irrigation schemes in Hawke’s Bay, Tasman, Wairarapa, we can say to them, ‘Look fellas, this is what you’re going to wear – and here’s the evidence’.”

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

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