An improved groundwater quality indicator, with more comprehensive data, additional measures, and refined methodology, has been released by Stats NZ today.
"This release has greatly improved data coverage, helping us better understand the current state of groundwater and how it's changing over time," environment statistics spokesperson Tehseen Islam said.
"It's a step forward in how we assess and report on groundwater quality."
Groundwater is water stored underground in aquifers - layers of water-bearing rock or sand. It is commonly accessed through wells and can also emerge naturally through springs.
Groundwater plays a crucial role in supporting rivers, lakes, and wetlands, and supplies drinking water to nearly half of New Zealand's population.
Groundwater quality: Data to 2024 draws on data from regional councils, unitary authorities, and two Crown Research Institutes - GNS Science (Institute of Geological and Nuclear Sciences) and ESR (Institute of Environmental Science and Research). It reports on 30 groundwater quality measures, alongside pesticide detections from a national survey.
"Our indicator shows that groundwater quality varies across New Zealand, depending on land use, and underlying geology," Islam said.
"We see areas with good quality groundwater, as well as sites with high levels of contamination."
The indicator uses maximum acceptable values (MAVs) from the New Zealand drinking water standards as a benchmark to assess the state of groundwater quality.
Between 2019 and 2024, MAVs were exceeded at least once at 51.1 percent of sites for at least one of 13 measures.
The results do not represent the quality of New Zealand's drinking water supply. The data analysed includes water from all monitored wells, not just those used for drinking. Drinking water may also come from surface or rainwater sources and is often treated before supply.
Groundwater quality: Data to 2024 has more information on the data, methods, and findings.
Stats NZ publishes and updates environmental indicators on the state of New Zealand's environment as part of a joint environmental reporting programme with partner Ministry for the Environment.
