Lower Waihao nitrate reduction project
Groundwater quality in the Lower Waihao region has declined and it's affecting community and private drinking water supplies.
High groundwater nitrate levels in Lower Waihao – How it happened
Several factors have led to a situation where groundwater nitrate concentrations are high in the Lower Waihao region and landowners still require resource consent for farming land use. Our Land and Water Regional Plan (LWRP, including plan changes 3 and 5) were written at a time when the Canterbury Water Management Strategy (CWMS) was being implemented, balancing goals like setting and meeting environmental limits, increasing irrigated land area and water use efficiency, and meeting drinking water standards.
A 2015 technical report produced to predict results of implementing these plan changes told us that if these plans went ahead, we were likely to see nitrate concentrations exceeding the Maximum Acceptable Value (MAV) in around 15 per cent of wells in the region. Read the 2015 technical report (PDF file, 12MB).
The LWRP and plan changes went ahead after community consultation. However, they proceeded under the assumption that the proposed Hunter Downs Irrigation scheme would be implemented, bringing more water into the area to augment Wainono Lagoon and potentially reducing groundwater nitrate concentrations. It was also assumed that Morven Glenavy Ikawai Irrigation (MGI) would get a collective discharge permit to cover the farms within its command area. Because this didn’t happen, each of the estimated 110 farms operating outside of the Permitted Activity rule limits now needs to apply for a Farming Land Use consent.
What we’re doing about it
Our actions have involved working with other agencies to inform the public about drinking water issues and enable safe drinking water supplies; compliance monitoring and enforcement action for both permitted and consented activities and ensuring landowners in the catchment are applying for land use consents where necessary.
- Our science team are supporting the community by collecting data and providing information on the state and trend of groundwater in the different catchments that make up the region.
- We've worked with Waimate District Council (WDC), Waihao Rūnanga and Morven Glenavy Ikawai (MGI) Irrigation to explore options for an alternative drinking water supply. In August 2025, WDC lodged an application for a new consent to take and use water that will be used to provide the community with lower-nitrate drinking water.
- Our resource management officers have undertaken compliance monitoring of farms located upstream of the Lower Waihao Rural Water Scheme, ensuring consent conditions are being followed, and that permitted activities are being carried out in a way that minimises nutrient loss.
- Our local land management advisors are working with farmers on how to achieve and go beyond good management practice to reduce nitrogen leaching into ground.
- Our consent planners have met with representatives of the around 160 properties that require farming land use consent, providing guidance on how to apply for resource consent, and what nutrient loss mitigations they might want to put in place on farm to make getting consent more likely.
What we’ve learned from our work
Our compliance work has concentrated on checking "point sources" – that is, specific areas and practices that can be significant sources of nitrate, like onsite wastewater systems, effluent ponds and offal pits.
We haven’t seen any leaching from these point sources that could have led to spikes in nitrate concentrations in groundwater.
What this – alongside our science – tells us is that there are not a few specific sources of nitrate entering groundwater that we can control.
Instead, the cumulative effect of intensive farming in the area is adding large volumes of nitrate to the catchment. Irregular heavy rainfall events wash this nitrate through the soil into groundwater, causing spikes in nitrate concentrations, as well as a general trend towards greater nitrate concentrations.
This means that to reverse this trend, we need to ensure farming practices in the region are going above and beyond good management practices in reducing nutrient loss.
As a regulator, we do this by issuing farming land use consents with conditions that ensure nutrient loss is measured, reduced and reported to us.
Resource consenting for landowners in the MGI scheme area
Under rules introduced by Plan Change 3 in 2017, most farms in the MGI Irrigation command area require a Farming Land Use consent.
We did not follow up with farms in the area because in the years since PC3 was introduced, MGI Irrigation was working towards getting a global consent that would cover all farms in its command area, but as MGI is no longer pursuing consent, individual consents are required for all farms above certain limits.
Plan changes created different consent rules and triggers for the different catchments in the area. You can check the consent triggers on our farming land use consent webpage.
Once you've confirmed you need consent, the best next steps are to engage a consultant and talk to us. We provide a free pre-application service where we can talk to you about putting together a solid consent application.
Because you're farming in an environment with degraded water quality, you'll need to demonstrate how your farming operation will mitigate risks to the environment and contribute to further degradation. To help with this, we've come up with some examples of the type of conditions you may wish to consider suggesting as part of your consent application.
Need help?
Contact your local advisors: Email your local land management advisor or talk to a biosecurity expert on pest control.
Access science reports, risk maps, and groundwater survey data to monitor and improve your practices: