Changes in nitrate concentration for monitored groundwater sites for the 10-year periods 2014 to 2024 and 2015 to 2025
| Changes in nitrate concentration for monitored groundwater sites |
2023/24 |
2024/25 |
| Percent sites decreasing |
17% |
20% |
| Percent sites increasing |
59% |
62% |
| Percent sites no detectable change |
24% |
18% |
This table shows the percentage of sites with increasing, decreasing or no detectable change in nitrate concentration for two ten-year periods (2014-2024 and 2015-2025). We do not compare trend results between the two 10-year periods because, to meet the target, 50 per cent or more of monitored sites must have decreasing concentration in nitrate for the current reporting year (2015-2025).
Why are we measuring this?
Nitrate contamination in waterways and groundwater is a concern for everyone in Waitaha Canterbury.
While nitrogen is important for plant growth, excessive levels in the form of nitrate in freshwater can harm aquatic insects and fish and promote an excess of weeds and algae. High concentrations in drinking water can be harmful to humans and livestock.
Nitrate can leach into groundwater or rivers and lakes from agriculture, wastewater treatment plants, fertilised lawns, leaky on-site wastewater disposal systems and industrial discharges.
Nitrate is highly water soluble and one of the most common contaminants of groundwater. Once in groundwater, nitrate can persist for years and travel long distances.
How do we measure the result?
Every year, Environment Canterbury collects groundwater samples from over 300 bores and wells (sites) across Waitaha Canterbury. So that we can monitor how concentrations are changing, we generally return to the same sites year after year, sampling sites on a monthly, quarterly or annual basis. We sample for a range of water quality parameters, including nitrate, and from a range of depths and locations. The shallowest well in our network is 3 metres deep, and the deepest is 294 metres.
Sampling follows Environment Canterbury’s standard procedures for the collection of groundwater quality samples, which are consistent with the National Environmental Monitoring Standard for groundwater quality sampling.
To understand if nitrate concentrations in Waitaha Canterbury are increasing or decreasing, data collected as part of our state of the environment monitoring programme are analysed for long-term (10-year) trends.
Our trend analysis follows methodology developed by Snelder et al. (2021) to assess the likelihood that nitrate concentration in individual wells is increasing, decreasing or show no detectable change over time.
What work have we undertaken to contribute to this outcome?
As the regional council for Waitaha Canterbury, we work with ngā Papatipu Rūnanga and our communities to set and implement environmental policies and rules that establish how resources, including groundwater, can be used sustainably. Limits are set for nitrate in groundwater in the Canterbury Land and Water Regional Plan (CLWRP).
Environmental regulation and protection is a core service of Environment Canterbury. To help achieve outcomes, we undertake targeted consent compliance monitoring around the region. Consenting helps sustainably manage and protect our natural environment and resources. We aim to deal with environmental risks before they become incidents and cause damage. We work with land managers, individuals and industry to improve compliance and ensure positive long-term environmental outcomes.
Our state of the environment monitoring programme enables us to measure and report on changes in freshwater quality, including reporting on nitrate in groundwater. Monitoring and reporting help us know whether the actions we’re taking to address degrading water quality are having the desired effect.
Who else plays a role?
Central government sets national policy direction for local authorities to implement through laws, national policy statements and national environmental standards. Regional plans contain rules and standards to give effect to national direction and maintain and protect Waitaha Canterbury's natural resources.
Consent holders are responsible for complying with the conditions in their resource consent for the sustainable management of our natural and physical resources.
Many landholders and water users go well beyond just adhering to the rules and strive to improve environmental outcomes for water through best management practices and active restoration. Many community organisations are involved in riparian and wetland restoration work and contribute to our understanding of the environment through citizen science.
We all have a role to play in looking after our groundwater.
Where can I find more information?
Read our annual groundwater survey report for 2024.
The Land Air Water Aotearoa (LAWA) website is a collaboration of organisations with a common aim: to tell the story of our environment. Environment Canterbury, along with all regional/unitary councils, is a founding partner. Data for monitored groundwater sites are updated annually on the Groundwater topic on LAWA.
Data for monitored groundwater sites are updated annually on the Groundwater topic on LAWA.
Our resource consents web page has information for resource consent applicants and holders.
