Source: Environment Canterbury Regional Council
Our compliance staff are active on the ground in Lower Waihao following elevated nitrate concentrations in a rural water scheme last year.
The ‘do not drink’ notice for the Morven, Glenavy, and Ikawai water scheme, including Waikakahi East, was lifted on December 18 after nitrate levels were successfully reduced.
On 2 December 2024 nitrate concentrations in the Lower Waihao rural community supply well exceeded the Maximum Acceptable Value (MAV) of 50mg/l.
The MAV of 50mg/l for nitrate in drinking water in New Zealand is set by Taumata Arowai, the regulator of water services in New Zealand. This aligns with guidelines set by the World Health Organisations (WHO).
The immediate issue was resolved when Waimate District Council facilitated a temporary alternative supply from the Waitaki River to mix with and dilute the water in the scheme.
This reduced the nitrate concentration in the supply to be below the MAV. The ‘do not drink’ notice was lifted on 18 December. They have since stopped using the alternative supply.
As of Friday 7 February, the scheme recorded a nitrate concentration of 33mg/l. A longer-term solution is currently being worked through.
Our compliance mahi
We conducted compliance visits at key properties in late 2024 and continue to work with landowners in the region to ensure there are no obvious point sources of nitrates and to check that landowners are following the conditions of their resource consent.
We are focused on ongoing compliance and consents work to implement the Land and Water Regional Plan, as well as land management work to improve on the ground practices.
Compliance officers conducted all priority site visits in late 2024. They continue to visit other relevant sites and complete compliance monitoring reports following these visits. Our land management advisors are also working directly with landowners in the region to ensure they are following the conditions of their resource consent.
We are also working with the local irrigation scheme’s members to ensure the necessary consents are in place.
In terms of the cause of the elevated nitrate concentrations, no single source was found for this specific event, and we don’t believe there would be a single source of nitrates that would account for the increased concentrations seen in December.
Private well users should check their supply
Private well users were advised that it remains their responsibility to test water quality to ensure it was safe to drink. We have information available about testing private wells and drinking water safety.
Communication with the community
Waimate District Council continues to update its ratepayers on the issue and we will provide updates through its website and to relevant authorities and community groups.
Te Rūnanga o Waihao is being kept up-to-date directly by our compliance team.
Factors affecting nitrate concentration
In late 2024, several heavy rainfall events in the area caused nitrate in the soil to get flushed down to the groundwater flows causing increased nitrate concentration.
The Lower Waihao supply well is very shallow at 4 metres, and shallow groundwater is prone to contamination from upgradient land use.
Local land use consists of intensive farming and related rural discharges (both from animal and human origin), which are known nitrate sources.
Previous updates
Update: 18 December 2024
The cease water consumption notice for the Lower Waihao Rural Water Scheme (including Waikakahi East) has been lifted.
Nitrate levels have been reduced and Waimate District Council have advised consumers on this scheme they can once again use water for drinking and cooking.
This does not apply to private wells. If you source your drinking water from a private well, it remains your responsibility to test water quality to ensure it’s safe to drink.
Private wells can still have high nitrate concentrations, despite the above-mentioned scheme now being declared safe to drink from.
Update: 3 December 2024
We have been advised by Waimate District Council that nitrate concentrations in the Lower Waihao Rural Water Scheme (including Waikakahi East) have now exceeded drinking water standards.
Waimate District Council is now providing alternative water for residents in this scheme.
This increase follows three large rainfall events over October and November that have caused nitrate in the soil to get ‘flushed’ down to the groundwater flows.
The Lower Waihao drinking water supply is a shallow groundwater well, located in an area of intensive farming. This means that heavy rainfall in the area can impact nitrate concentrations.
Our monitoring has shown nitrate concentrations in shallow groundwater in the area to be increasing over the past 20 to 30 years.
We are supporting Waimate District Council with this issue. This includes encouraging private well owners outside the drinking water scheme to test their water if they use it for drinking.
We are committed to taking further steps to improve water quality in this area. As the land use activity regulator, we have boosted our compliance monitoring in the region to ensure potential sources of nitrate are being well-managed.
This includes on-farm visits to monitor dairy effluent consents in the catchment and checking on permitted activities to ensure they are being carried out within plan limits. We are also working with the local irrigation company on its consenting requirements.
