Families drinking bottled water after ‘shock’ nitrate test results
When Martin Hewitt moved to the North Canterbury settlement of Ohoka in the mid1990s, tests of the drinking water from his well showed nitrate levels of 2.4mg/L.
Two weeks ago, a sample from Hewitt’s bore came back at 20.4mg/L. “It was quite a shock, and we’ve been drinking the water for all that time,” he said.
The reading, almost double the maximum allowable value for nitrate nitrogen (11.3mg/L), was the highest reading from about 450 public and private samples recently tested by Greenpeace.
Nitrate-nitrogen (commonly referred to as nitrates) in waterways comes primarily from excess use of nitrogen fertilisers and the nitrogen-rich urine of cows, which can seep through the soil and into waterways and underground aquifers.
High nitrate levels in drinking water have become a known problem for some private bores, which district and regional authorities say they have no obligation to monitor. Thousands of Cantabrians drink water from private water supplies, including nearly 7000 in the Waimakariri District alone.
However, there is mounting alarm over council-controlled water supplies in Selwyn which have shown nitrate levels over 5.65mg/L, which (depending on the supply size) triggers closer monitoring and reporting requirements.
The Greenpeace testing found that nearly a quarter of samples were above the 5mg/L threshold for increased risks of pre-term birth and other reproductive risks. More than half were above 1 mg/L. Some evidence has suggested that nitrates even at this relatively low level could lead to to an increased risk of bowel cancer, but this link remains contested.
Hewitt realises he should have tested his water earlier, especially as surrounding land use changed from predominantly sheep farming to dairying.
He’s worried about the potential longterm health impacts, as well as the effect on his property value. He and his wife have used bottled water for drinking and teeth brushing since finding out.
He has applied to the Waimakariri District Council to connect to the Ohoka water supply, but understood the cost could be $5000 to $10,000.
‘Water we can’t drink’
Charitee and Johnny Adams used to boast about the quality of the water on their Springston lifestyle block, taking bottles with them whenever they travelled.
The couple moved there in 2000, but it wasn’t until neighbours told them of worrying test results in 2021 that they got their water tested, and were shocked when it came back at 11.9mg/L.
They’ve since installed a negative ion water system at a cost of more than $1000 to remove the nitrates.
The couple are encouraging others to get their water tested, and want action from authorities. “We shouldn’t have water we can’t drink.”
Neighbours Brian and Robyn Patchett, who have lived on Bethels Rd for more than 30 years, found that nitrate levels in their well had gone from “virtually nothing” to 10.6mg/L in 2021.
When Brian raised concerns with Environment Canterbury, he said he was told it was his problem. “That’s rubbish. We have absolutely no control over what comes into our well,” Patchett said.
After investigating tapping into a neighbour’s far deeper well, they discovered that its nitrate levels were just as bad.
Families drinking bottled water
When Kirwee resident Simon La Monica learned that nitrate levels topped 4mg/L in the council water supplying his house, he switched the family to bottled water before installing a reverse osmosis filter.
“I’ve got two young children, 5 and 7, and while I care about my health, I care about theirs more.”
La Monica knew there were elevated nitrate levels in the area before moving to the small Selwyn settlement, but was shocked to see how high they were.
As reported by The Press, Selwyn District Council’s own recent testing showed water supplies in Kirwee (5.99mg/L), Darfield 1 (6.3mg/L) and Rolleston’s Illinois Drive bore (7.11mg/L) all above half the maximum allowable value, while Dunsandel and Edendale previously breached 5.65mg/L.
Te Pirita (5.58mg/L), Darfield (5.2mg/L) and Rolleston-Overbury (4.99mg/L) bores were not far behind.
La Monica was not appeased by being under the maximum allowable value, which he noted was set decades ago. “We know so much more than what we did back then.”
He recently tested his treated water, and felt it was “still too high” at 1.02mg/L.
Burnham couple Jean Guest and her husband Geoff Wilson also use bottled water.
She said she “always thought people who drank bottled water had more money than sense”, but after discovering that the well on their property had levels of nitrate over the national standard, the couple felt they had no choice.
She wants the council to help people like them get on town supplies, but is aware that levels in some Selwyn council supplies are also on the rise.
Luis Arevelo and his wife have been drinking and cooking with bottled water since moving to Oxford, and get through 30 to 40 litres a week.
He said high nitrate levels in the area were common knowledge, but it was still a shock when their Waimakariri District Council-supplied water came back at
5.35mg/L. He’s joined a new community-led action group pushing for more transparency and better health outcomes.
A Waimakariri council statement said the council tested public water supplies for nitrates monthly, and all were at less than half the maximum allowable value.
The Selwyn council has budgeted $5.3m to try to find a lower nitrate source, in the hopes of centralising some water supplies, and has put a $405m price tag on doing so.
Its water management plan says it is monitoring eight of its 26 water supplies with “high” or “relatively high” nitrate levels, investigating alpine areas for low nitrate sources, and investigating the cost and feasibility of “nitrate removal technologies” for existing supplies.
ECan declined to comment, but on its website it says it has introduced “some of the strictest farming rules in the country”, and allowed “very few” dairy conversions in recent years.
However, it warns that groundwater quality may not improve for at least another 15 to 20 years, and that in some cases “we can expect the situation to get worse before it gets better”.
Greenpeace spokesperson Amanda Larsson said the town supply results in particular were worrying. “People expect their local council to supply safe drinking water, but nitrate contamination is a growing risk.”
University of Otago research fellow Marnie Prickett said it seemed that local and central government had forgotten the Havelock North drinking water crisis inquiry, which emphasised the importance of source water protection.
Canterbury’s growing nitrate issue
Nitrate infiltration into groundwater has been a growing issue across the Canterbury Plains for decades.
Campaigners argue that the maximum limit of 11.3mg/L, based on 1958 World Health Organisation guidelines, is too high for human and waterway health.
A 2002 ECan technical report by Carl Hanson – now the council’s groundwater science manager – noted that high nitrate concentrations had been observed in the south and west of Christchurch since the 1970s, and that research dating back to the 1980s predicted that new irrigation schemes and more intensive land use could lead to higher nitrate concentrations in groundwater, “threatening its suitability” as drinking water.
The report warned of a “number of bores already testing over half the maximum allowable value” across swathes of the plains, particularly the Ashburton-Pendarves area, the south and west of Christchurch, and the area between the Waimakariri and Ashley rivers.
It predicted that it would take approximately 30 years for the nitrate nitrogen concentration to increase from 5.6 to 11.3 mg/L. However, the combination of rapid land use intensification, a surge in dairying, a vast increase in the amount of irrigation, and the booming population of areas like Selwyn may have contributed to that timeline contracting.