New report draws from decades of scientific nitrate information

Environment Southland has released a report that summarises the current state of knowledge on the magnitude and extent of groundwater nitrate contamination in Southland.

Environment Southland General Manager Science Karen Wilson said although the report doesn’t present new data, it brings together a wide range of information to give an integrated view of groundwater quality, nitrate sources, and health risks.

“This science formed the basis of the Southland Water and Land Plan, which was accepted by the Environment Court. The Plan was the first step in responding to Southland’s groundwater nitrate challenges.

“The new report draws on decades of published research, monitoring data, and regional modelling and presents it in a more accessible way, making it easier for communities and decision-makers to understand and respond.”

Nitrate contamination of groundwater in Southland is widespread, reflecting the combined effects of intensive land use and the underlying vulnerability of many of the region’s groundwater systems.

Key findings of Environment Southland’s 2026 regional nitrate assessment include:

• Elevated nitrate concentrations are widespread across multiple groundwater management zones.
• Many sites show long-term deteriorating trends.
• Murihiku Southland’s geology and shallow water table means there is a high proportion of vulnerable aquifers.
• Concentrations frequently exceed 3.5 mg/L and in some locations exceed the New Zealand drinking water standard of 11.3 mg/L.
• Screening analysis indicates that many domestic and public groundwater supplies are located within areas mapped as highly vulnerable to nitrate contamination, representing potential exposure risk and increased reliance on monitoring and treatment.

Groundwater systems can respond slowly to land-use change. Improvements or reductions in nitrogen losses at the land surface may take years to decades to be reflected in groundwater quality.

“This is a challenge shared by other regions across the country and we’re working closely with our regional sector colleagues and other agencies on this issue.”

Read more about nitrate in groundwater and the report, Nitrogen Contamination in Southland Groundwater 2026 report, head to our website www.es.govt.nz/nitrate

To delve into the data and trend information for specific sites across New Zealand go to www.lawa.org.nz.

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For more information call our communications team 0800 76 88 45 or email communications@es.govt.nz