Taking action on nitrate
Environment Canterbury media release: 16th September 2025
Most of our region’s drinking water comes from groundwater, so when monitoring shows increasing nitrate concentrations in groundwater there is understandable community concern. We’re determined to reverse these increasing trends.
Nitrate concentrations are increasing in the long term
Nitrogen is an essential element required by plants for growth and is added to land as synthetic fertiliser and animal effluent (both from grazing and applied effluent) to promote the growth of pasture and crops.
When there is too much for the growing pasture and crops it can enter streams and lakes. The excess nitrate in these waterways can then promote growth of plants and algae in the water, choking our waterways. Excess nitrogen in the soil not taken up by plants can leach through into groundwater.
Our most recent groundwater survey found a 10-year trend for nitrate concentrations to be on the increase in 62 percent of monitored sites across Waitaha Canterbury, with 20 percent of sites showing a decreasing trend, and the remainder showing no noticeable change. This is a long-term change over 10-year trends.
Work on lag times (the time between reducing nitrates on the ground and seeing the result in groundwater) in Canterbury suggests that we should be able to see a response within 3-5 years of changing practices when we look in particular places. Recent work has shown that there is evidence of reductions in groundwater nitrate concentrations in some places as a result of changing land use practices, but it is not everywhere and concentrations remain high in many places.
High nitrate concentrations have been linked to risks to human health.
Find out more about the health risks of high nitrate levels.
Why we’ve seen increasing nitrate concentrations
The increase in nitrate concentrations over time has stemmed from more intensive land-use. The principal source of nitrate entering groundwater is from animal urine patches leaching into the ground from pasture grazing and winter grazing.
Other sources include:
- synthetic fertilisers leaching into the ground;
- leaky or inefficient onsite wastewater disposal systems;
- animal effluent applied to land as fertiliser leaching into the ground; and
- industrial use or disposal of animal waste and chemicals.
What we’re doing to address the issue
Regional councils have certain roles and powers under legislation – as well as the ability to work with mana whenua, industry and stakeholders – to act within our mandate to mitigate nitrate losses to the environment.
This means there are actions that Environment Canterbury, as the regional council, is doing to address this issue. But it is not something we can solve on our own, and many other entities are also involved.
The actions we are undertaking include:
- Supporting farmers: Canterbury farmers are making progress in reducing nutrient and other contaminant losses within their farming systems.
Our land management advisors are supporting them with this work, raising awareness and encouraging best practices, including:
- nitrogen use efficiency
- winter grazing
- critical source area management.
- Protecting and promoting wetlands: We’re focused on identifying and protecting Canterbury’s remaining wetlands by providing better information and incentives for landowners to protect existing wetlands, as well as making it easier for landowners to create constructed wetland areas that can act as filters to remove nitrate and other contaminants from freshwater.
- Keeping it local: We’re working with and funding communities at a catchment level to empower them to take the initiative and innovate for water quality solutions.
- Reviewing our planning framework: We’re undertaking a review of our current plans to get a clearer picture of the state of our environment and to measure the effectiveness of our current policies. However, we cannot currently propose new changes to our planning framework due to central government’s changes to the resource management system.
- Improving resource consents: We’re strengthening new resource consent conditions and clarifying our expectations on how consent holders can demonstrate compliance with these conditions. We’re sharing examples of these typical conditions that consent applicants can propose, which can be tailored so they are appropriate for the local environment where the proposed activity will take place.
- Improving compliance work: We’re prioritising compliance monitoring for the highest-risk activities, as well as activities in community drinking water protection zones and other areas with especially sensitive environments or already degraded water quality.
- Taking compliance action: We’re ensuring we take appropriate compliance action when the right thing isn't done – from education and on-farm support through to enforcement when needed.
How we got here
Before 1990, land use in Waitaha Canterbury was less intensive than it is now. The gradual increase in irrigated land area and the associated rise in land use intensity since that time, including a rise in the number of dairy farms, has resulted in more nitrate leaching into our groundwater. Pre-1990, we did see nitrate hotspots from intensive land use, but not as widespread as we now see.
There is also a time lag between an activity occurring on land and the nitrate associated with that leaching into groundwater beyond the root zone of plants. Sometimes it can take years or decades for nitrate to move right through a catchment.
Under the Resource Management Act (RMA), an activity is permitted unless there is clear evidence it will cause harm. The more information and knowledge (with data as evidence) we have over time, the better we can determine if an activity will cause harm.
When the RMA was introduced, our understanding of the environmental risks of nitrate, how it moves through the environment and how long it persists was less, and many consent applications were granted with more permissive conditions.
Under the Canterbury Water Management Strategy, communities had a say on what rules were put in place in our Land and Water Regional Plan.
Waitaha Canterbury is a diverse region, and our varied environment produced different expectations and results – something reflected in the plan changes we’ve made. These sub-regional plans included objectives and limits for most lakes, rivers, groundwater systems or catchments.
Our plans reflect some big compromises made between economic and environmental interests, and no one party got exactly the rules they wanted.
In developing those plans, important trade-offs were made between opportunities for economic development through land-use intensification and the effect it would have on water quality.
Increasing concern on the impact of nitrate
Since our plans were put in place, greater international research into the link between nitrates and human health has led to more public attention and concern over nitrate concentrations in drinking water, and community expectations over how much we should be doing to protect drinking water at source have changed.
Find out more about drinking water in Waitaha Canterbury.
Due to a pause being put on all planning work by central government, we are currently unable to amend our plans to create further protections for water quality, but, as mentioned above, we are taking a range of measures within our power to address the issue.
We’re just one of the agencies acting to protect drinking water quality. Our focus is water quality at source – that means the lakes, rivers, streams and groundwater that may or may not be used for drinking water.
Reticulated drinking water suppliers – typically local councils – are responsible for the water they provide users, while the Ministry for the Environment sets national policy and direction and Taumata Arowai is the Water Services Regulator.
These agencies, together with ngā Rūnanga and key environmental agencies, will all influence how we move forward.
Nitrate is a collective problem and although we can’t quickly undo what has already occurred, all relevant agencies need to work together more effectively towards common and agreed outcomes that reflect today’s thinking.
Looking ahead
The Government is signalling a new direction through resource management reform. We don’t know exactly what shape that will take, but we know we need to be ready.
All the early signs point to the need for a single regional plan. Our Strategy and Planning team is currently gathering information that will inform the foundations of whatever our next regional plans look like.
Keeping your drinking water safe
If you’re on a private drinking water supply:
Make sure your water is tested and treated as necessary.
If you’re a farmer:
Talk to our Water and Land team about how you can minimise nutrient loss.
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