Source: Radio New Zealand
Nitrate levels have been testing high in Waimate district water supplies (file photo). HENDRIK SCHMIDT
Nitrate levels are inching up in a small South Canterbury town where some council water supplies were previously off limits for extended periods twice following breaches of the drinking water standards.
On Friday, the Waimate District Council reported the Lower Waihao and Waikakahi East Rural Water Scheme had reached 8.8 mg/L of nitrate-nitrogen (N03-N).
The legal limit is 11.3 mg/L.
Nitrate contamination in drinking water above 5mg/L has been linked to an increased risk of preterm birth.
The New Zealand College of Midwives advised pregnant people to consider an alternative water source if their primary water source is above this level for nitrate.
Some international research has drawn links to bowel cancer at far lower nitrate levels, and some health advocates have advocated for New Zealand’s maximum to be lowered.
Two weeks ago, Greenpeace water testing in Waimate found the supply was at 6.07mg/L of nitrate.
Waimate District Council’s own testing on 20 November found the supply was 6.35 mg/L.
“The Lower Waihao Scheme has consistently tested around 5 mg/L since April, but nitrate levels have shot up in the space of less than a month,” Greenpeace Aotearoa spokesperson Will Appelbe said.
“The council has done what they can in an attempt to reduce the contamination, but this is the ambulance at the bottom of the cliff. The only way to permanently improve nitrate contamination is to address the source of the pollution: the intensive dairy industry,” he said.
In late 2022, around 650 Waimate households were told their tap water was unsafe after nitrate levels in the Waihao and Waikakahi East rural water schemes exceeded the maximum allowable value.
Again, in December 2024, residents were advised not to drink the water after it breached the limit. At the time, the council provided water tanks, and diluted the supply with water from the Waitaki River.
However, the council reported the presence of didymo algae and sediment when the river was high meant that was not viable long term, and after ruling out plans for an expensive denitrifcation system has been granted a consent to tap a new, lower nitrate water source, with work expected to start in 2026.
In September, the outgoing canterbury regional council narrowly voted to declare a nitrate emergency at the final meeting of its triennium.
Government ministers and farming groups called the move a stunt, but Earth Sciences New Zealand research found the region had the highest percentage of elevated nitrates in groundwater in the country.
The council’s most recent annual groundwater testing found nitrates had increased during the past ten years in 62 per cent of test wells.
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– Published by EveningReport.nz and AsiaPacificReport.nz, see: MIL OSI in partnership with Radio New Zealand
