NitrateWatch shining a light on NZ’s groundwater drinking supplies
Anyone who visited Environment Southland’s site at the Southern Field Days would have encountered the friendly faces shining a light on the quality of New Zealand’s groundwater drinking water supplies.
The team from the Crown Research Institute GNS Science headed south from Wellington to showcase their NitrateWatch programme which is testing groundwater samples across the country.
The study focuses on the level of nitrates found in drinking water from private bores and springs which are not usually monitored or tested regularly.
NitrateWatch started as a pilot programme, led by Environmental Scientist Karyne Rogers, looking at nitrate and contaminant levels in Northland drinking water.
After making good headway and some interesting findings, the study was then expanded to include all of New Zealand.
"Our research tells us that groundwater is the most contaminated of all water,” Karyne says
“Surface water, such as the water in lakes and rivers, can be diluted by rain which can help wash out contaminants.”
“But water in the ground is similar to having water held in a sink, there is nowhere for anything to wash away.”
“Groundwater can also be very old and it can be contaminated with nitrates from decades ago.”
One of the key philosophies behind NitrateWatch was the trade-off between providing a free testing service and GNS Science being able to use the test results publicly.
Keeping those results confidential is part of making that approach a workable and community-based one.
“Individual water testing results are confidential, people have asked about the potential impacts on having the water on their properties tested,” Karyne says.
“And we wanted to address that by making them confidential.”
“Our data is published in 10 square kilometre blocks and that gives people an idea about the water quality in their area and whether they need to be testing their own water supplies.”
NitrateWatch’s published results for Southland show some high levels of nitrates, as well as some better results.
“There are definite hot spots in Southland,” Karyne says.
“There are areas where there are not problems, and other where there are problems.”
Some may think that having some areas with high nitrate levels in their water in a proud farming region like Southland is easily explained.
But the team behind NitrateWatch are not making any assumptions about why some high testing levels have occurred.
“Some New Zealanders might say high nitrate levels are from farmer over-stocking or putting too much fertiliser on,” Karyne says
“But we are taking a different approach, we are taking the position that the majority of farmers are following the rules.”
“Our research is pointing to the land and the legacy.”
“Legacy is groundwater that has been contaminated as long as 40 years ago that has sat in the ground.”
“That water may or may not have been contaminated from recent farming practices, but it may have been many years ago.”
“When we talk about land, we mean different parts of New Zealand assimilate or use up nitrate differently."
“That means even if farmers are under stocking their farms or using low amounts of fertiliser, groundwater on their land could still having high nitrate readings.”
More specifically, NitrateWatch’s research show that soil types and geology have a major influence on the contamination levels in groundwater.
That means approaching water contamination may need an approach that directly addresses the soil types above it used for farming.
“A one size fits all approach to nutrient loading thresholds is not the best,” Karyne says.
“Some land shouldn’t have fertiliser applied at normal rates because of the way that land removes nitrates.”
“A whole new approach to looking at the impacts of soil types on water contamination is needed.”
“It may mean that some land might have to be changed from its current use considering the effect it has on groundwater.”
The level of detail in NitrateWatch’s research is such that the source of nitrates found in groundwater tests can be linked back to their source.
Variances in nitrate isotopes can reveal the source of the nitrate contamination, such as through sewage, fertiliser or through natural stores such as trees and leguminous crops.
With the NitrateWatch programme around nine months into its national research, more water sampling would help boost the depth of the research.
GNS Science’s presence at the Southern Field Days helped increase its numbers.
“We gave out over 100 free water testing kits and had a lot of great conversations with people at the Field Days,” Karyne says.
Those wanting to find out more about the results in their area so far can read each region’s testing results on NitrateWatch’s website.
People in an area with high nitrate readings are encouraged to request a free testing kit from NitrateWatch.
While GNS Science and Nitrate Watch do not give out health advice for those with high nitrate levels in their drinking water, they do give people as much information about their situation as possible.
It should be noted that traditional water filters are not the answer.
Karyne points out that while most water filters can collect E.coli and other contaminants, nitrates flow straight through them.
