Old Whangārei water test sparks inquiry into nitrates in Hikurangi bores

High nitrates can cause blue-baby syndrome in infants bottle-fed with contaminated water. Photo \ 123rf

A Greenpeace map showing dangerous levels of nitrate in Whangārei water has highlighted the need for more testing of Northland bores.

The charity’s Know Your Nitrate Map was launched last week, with the aim of informing people about safe drinking water, using information provided by district councils and Greenpeace’s own testing.

High nitrate contamination can cause a lack of oxygen in infants bottle-fed with affected water, known as blue-baby syndrome, and is also linked to premature births and colorectal cancer.

While nitrate occurs naturally in the environment, high nitrate levels can be caused by manufactured fertilisers or decaying organic matter.

Greenpeace’s map shows Northland’s Hikurangi to Kauri area has an “extremely elevated nitrate” level of 16.87mg/L - far higher than the international drinking guidelines of 11.3mg/L and more than 10 times the optimal level of under 1mg/L.

Across New Zealand, only three areas have higher nitrate concentrations, and all three are in Canterbury.

But closer inspection shows the Hikurangi results are 27 years old, with the last sample taken from this area in 1996.

These results are very out-of-date, said Greenpeace spokesman Nick Young, and the organisation would like to know why bore monitoring in this area stopped.

The data was provided by Northland Regional Council, which was asked to provide data for all groundwater monitoring bores in the region, including for bores no longer actively monitored, Young said.

The lack of information happens often in Northland, he said, but Greenpeace decided providing the old data with a date was better than no information at all.

“People just don’t know how safe their water is because the testing isn’t being done.”

The organisation encourages people who have a bore to send in samples to its free mail-in service, which will help give a more up-to-date picture.

Greenpeace's Know Your Nitrate Map shows "extremely elevated" nitrate levels in the Hikurangi/Kauri area, indicated in purple.

Northland Regional Council said it will look into the nitrate monitoring from the Hikurangi area and might further investigate the elevated result.

Group manager environmental services Ruben Wylie said it appears the monitoring related to a resource consent application or resource consent.

The council is now retrieving the relevant hardcopy file from its archive to check for additional information, to better understand what could have caused the elevated results and why sampling stopped, he said.

“A decision on whether further investigations are warranted will be made once staff have reviewed the file from archives.”

Across Northland, the council monitors groundwater quality for nitrates and other red flags - like pesticides and heavy metals - as part of its environment monitoring programme, Wylie said.

This monitoring has only identified a few sites with elevated nitrate levels - where further investigations are then done to find the extent and source of the elevated nitrate.

“Landowners are informed and, in the past, our land management team has worked with landowners in surrounding area to reduce potential nitrate inputs.”