ECan survey shows nitrate levels rising in majority of rural Canterbury wells

Environment Canterbury released its 2025 Annual Groundwater Quality Survey on November 4, revealing that nitrate concentrations are climbing in 59 percent of monitored rural wells. The survey analyzed samples from 358 private water supplies across the region. The findings show that nitrate-nitrogen levels have increased over the past decade in more than half of the sites where long-term data was available.

Specifically, 38 wells, representing 10.6 percent of the total, recorded concentrations above the national drinking water maximum acceptable value of 11.3 milligrams per litre. This figure marks a slight increase from the 10 percent of wells that exceeded the limit in 2024. For the remaining sites, 24 percent showed decreasing trends, while 17 percent displayed no clear directional change in their nitrate levels.

The new data arrives shortly after the regional council voted to end a formal nitrate emergency that had been in place since September 2025. In that month, ECan members voted 9-7 to halt further investigations into funding for the treatment of private water supplies affected by nitrate contamination. The decision concluded the emergency status but left many rural households relying on wells with rising contaminant levels.

Greenpeace, which had argued the crisis persisted, cited the new survey as proof that the situation has not improved. Niamh O’Flynn, the organization's programme director, stated that the results were predictable. She noted that thousands of residents in the region cannot safely drink water from their taps while the intensive dairy industry, which she identified as the primary source of pollution, continues to expand.

Local politicians on the council are also questioning the pace of progress. Councillor Genevieve Robinson pointed out that ECan has a performance target requiring at least 50 percent of monitored sites to show decreasing nitrate trends. The new data falls short of that benchmark. Robinson asked where measurable improvements are coming from and who bears the cost when environmental goals are repeatedly missed.

Dr. Elaine Moriarty, the water and land science manager for ECan, explained that groundwater responds slowly to changes in land management. She noted that in areas with deep aquifers, the water sampled today may have entered the ground years ago. This lag means that improvements in surface practices can take a long time to appear in monitoring results, making annual surveys essential for tracking long-term shifts.

The survey also linked groundwater quality to the health of local surface waterways. More than half of the shallow groundwater samples taken in areas connected to rivers and streams contained nitrate levels above the 2.4 mg/L bottom line for surface water. This indicates that groundwater is contributing to ecological impacts in streams and rivers.

The report included positive findings regarding bacterial contamination. The number of wells where E. coli was detected dropped from 49 in 2024 to 23 in 2025. The survey also featured a one-time assessment of lead concentrations. Lead was found in some samples at very low levels, but no wells exceeded the established drinking water standard for the element.

The next step for the council involves continuing its annual monitoring program to track these trends. ECan will use the data to identify where risks remain and to provide communities with information about the state of their water supplies. The organization will maintain its efforts to improve groundwater quality despite the slow pace of visible results.