New Zealand’s Precious Groundwater Vulnerable To Contamination

Groundwater monitoring results from regional and unitary councils published by the Land, Air, Water Aotearoa (LAWA) project today show that groundwater quality across the country continues to be affected by land use activities.

LAWA Groundwater Science Lead and Environment Canterbury Science Manager Carl Hanson said the results from 962 monitored sites are freely available on the LAWA website for everyone to access.

“At a national scale, the results show nitrate concentrations have remained fairly steady over the past ten years, and there is a slight increasing trend for E. coli detections.

“E. coli in a sample is a concern for anyone using the groundwater as a source of raw drinking water. If E. coli is found in groundwater, it indicates faecal material is present and a risk that other harmful pathogens are in the water that could make anyone who drinks it untreated very ill.

“The reason for the increase in E. coli detections in groundwater is not clear, but it may reflect increased contamination possibly related to more intensive animal grazing and growing numbers of onsite wastewater disposal systems.

“All groundwater is potentially vulnerable to pathogen contamination, so people should have their well water tested regularly if the water is being used for drinking or preparing food,” said Mr Hanson.

The results represent the water from long-term monitoring wells that sample raw water before any treatment, which could then potentially be used for water supply. Not all wells with data published on LAWA are necessarily used as a source of drinking water.

“Results published on the LAWA website today also show that the vast majority of groundwater sites monitored have nitrate concentrations below the Drinking Water Standards for New Zealand.

“However, there are pockets of high nitrate concentrations with just over 6% of wells monitored exceeding the standards. Higher nitrate concentrations are generally found in areas of intensive grazing or vegetable farming. Long-term nitrate trends in groundwater are variable, with roughly equal numbers of wells displaying improving and degrading trends.

“In good news, it appears seawater intrusion is not widespread, but continued monitoring is important so that we know if the situation changes,” said Mr Hanson.

Recent results and trends for groundwater sites across New Zealand can be freely explored using the LAWA website interactive desktop map: www.lawa.org.nz/explore-data/groundwater-quality

Te Uru Kahika - Regional and Unitary Councils of Aotearoa Chief Science Advisor Dr Chris Daughney said the regular monitoring of groundwater is important for understanding freshwater quality in New Zealand.

“Regional and unitary councils regularly monitor groundwater because pathogens, nitrate, and other contaminants can affect the suitability of groundwater for various uses, not just as a source of drinking water, but also as it’s the primary source of water feeding our rivers and streams.

“Generally, groundwater quality in New Zealand is very good and we want to keep it that way. It underpins our food protection and whole cities and towns in Aotearoa rely on groundwater as a primary drinking water source that is treated before being supplied to households, communities, and businesses.

“The monitoring results published on the LAWA website ‘Groundwater Quality’ topic today show that work must continue to better understand and prevent contaminants entering our underground freshwater.

“It’s incredibly valuable to have this data as it can help to direct efforts, track changes over time, and ultimately inform important decisions about resource management,” said Dr Daughney.

The LAWA website shows groundwater quality information for around 1000 wells located throughout New Zealand. Regional councils and unitary authorities monitor groundwater for a range of water quality indicators, five of which are displayed on LAWA: chloride, electrical conductivity, dissolved reactive phosphorus, E. coli and nitrate-nitrogen.

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