Court rules Managed Aquifer Recharge can go ahead in mid-Canterbury
A large-scale project designed to reduce high nitrate concentrations in groundwater has got the green light to expand – with conditions still to be determined.
Managed aquifer recharge – known as MAR for short – was trialled in the Hekeao Hinds plains for five years and showed some success in reducing nitrate concentrations at test sites.
Now a court has ruled that it can go ahead at a much greater scale.
Environment Court dismisses appeal
The trust that manages the mid-Canterbury MAR scheme lodged consent applications in 2023, and an independent commissioner made the decision to grant the necessary consents on behalf of Environment Canterbury in 2025.
Te Rūnanga o Arowhenua appealed the granting of consents on points of water take and use and cultural values.
The Environment Court released its ruling on August 24, dismissing the appeal.
The Court ruled that the granting of a use-only consent was lawful, and the water used for MAR can be done using water taken under the existing Rangitata Diversion Race water take consent, thereby not breaking the Rangitata Water Conservation Order, but ordered parties to propose a revised set of conditions, which will be lodged with the Court by September 21.
How MAR works
Managed aquifer recharge involves the targeted release of clean surface water into the ground at specific locations where it can enter the water table and mix with groundwater.
Irrigation schemes provide water to hundreds of farms across the Ashburton district through a network of canals and pipes fed from the Rangitata Diversion Race, which also powers two hydroelectric plants.
When water is available, this infrastructure can also be used to release water into leaky basins where it will enter groundwater.
The MAR water, which comes from the Rangitata, has very low nitrate, and can help flush high nitrate groundwater through the environment, diluting nitrate concentrations.
However, MAR has an effect limited to the areas downgradient of release sites, and would not affect some key community water sources.
Just one tool in the nitrate toolkit
Managed aquifer recharge was envisaged as part of a suite of solutions to address high nitrate in groundwater in the Hinds Hekeao plains.
As part of Plan Change 2 to the Canterbury Land and Water Regional Plan, farming activities were required to operate at good management practice by 2017, then achieve further nitrogen loss reductions of 36 percent by 2035.
The goal of these reductions together with MAR is to reduce the nitrate concentration in the area’s shallow aquifers to 6.9mg per litre.
For more information on how farmers are reducing their impact on nitrate in groundwater, see our Reducing nitrogen loss webpage.