New Zealand’s Groundwater quality steady with contamination in places

Today marks the release of the Groundwater National Picture 2023 by Land, Air, Water Aotearoa (LAWA), offering an updated glance into the state of New Zealand's vital groundwater resources.

This year's summary, now available on the LAWA website, underscores the importance of groundwater in New Zealand; crucial for drinking water, irrigation, industry, and sustaining many streams and lakes.

While the 2023 summary indicates that groundwater conditions aren’t changing drastically year-to-year, it highlights persistent challenges.

LAWA Groundwater Science Lead, and Environment Canterbury Science Manager, Carl Hanson explains, " Our analyses of data from nearly a thousand regional and unitary council monitoring sites provides insights about the health of our groundwater. These findings are now available for public access on the LAWA website.

“At a national scale, most of our groundwater maintains very good quality. However, E. coli is detected in about half of the wells monitored and a range of nitrate concentrations are observed, with a minority exceeding the Drinking Water Standards for New Zealand.

“These findings reflect the impact of land use changes on groundwater quality,” said Mr Hanson.

E. coli detections in groundwater, which signal potential faecal contamination, are a concern for raw drinking water sources. Mr Hanson reminds anyone with a private bore to check their well head is secure and visit official online resources or their council for advice.

However, not all wells tested are necessarily used for drinking. Results do not reflect the quality of New Zealand’s reticulated, treated drinking water supply.

Nitrate levels are mostly stable at the national level but show variable trends across different areas, with higher nitrate concentrations generally in areas with intensive agricultural activities. Concentrations are higher than the Maximum Acceptable Value at 6% of monitored sites, meaning the water from these wells at the time of sampling was deemed a health risk if consumed.

LAWA Project Chair Dr Tim Davie emphasised the importance of groundwater and the relevance of the data available on the LAWA website.

“It’s important to monitor the quality of groundwater because it is widely used to sustain people, production, and is a key part of the water cycle contributing to surface water.

“Like other water resources, it’s at risk from contamination by pathogens and other pollutants which can affect its suitability for different uses. We also know that in coastal areas, seawater intrusion can make groundwater unsuitable for drinking or irrigation​​.

“On the LAWA website, regional and unitary council monitoring programme results are available to communities quickly through the interactive map and in detail at individual well information pages.

“LAWA is a useful resource for anyone getting involved in conversations about land and water planning or who want to know more about the state of our environment,” said Dr Davie.

The 2023 Groundwater Summary draws from data collected from approximately 1,000 well sites across the country, most sampled every three months. This extensive monitoring network is vital for evaluating groundwater quality and identifying trends over time.

Unique to New Zealand, LAWA offers free access to up-to-date, trustworthy environmental data.