Nitrate Levels in Groundwater Wells

5th February 2019

Over the past week, there has been media coverage relating to nitrate nitrogen concentrations in groundwater within the Amuri Irrigation Company (AIC) scheme. We are working hard to manage our impact on water quality and would like you, as our community, to know what we are doing to reduce our impact.

In 2017, we upgraded our open race network to a more efficient pipe network at a cost of $83M. However more efficient water has largely eliminated leakage from water races leading to less water entering the aquifer which leads to potentially higher nitrate nitrogen concentrations in groundwater. 

Our resource consent requires monitoring of groundwater quality in the tributaries of the Waiau River. If a monitoring well reaches the Maximum Acceptable Value for nitrate nitrogen concentration (MAV), we monitor all drinking water wells within the tributary catchment and advise landowners when well concentrations are above MAV. This happened in 2017 in the Lowry Drain catchment and affected landowners were all advised.

AIC and our shareholders have put significant resource into environmental work to reduce nitrogen losses and protect waterways in recent years. These are the tools we are currently using to achieve better environmental outcomes:

  • Responsible Environmental Governance: The Environmental Subcommittee oversees the implementation of our Environmental Management Strategy;
  • Farm Environment Plan Audits: We have been auditing FEPs since 2016 and now have 83% of farmers are on track to meet Good Management Practice (‘A’ or ‘B’ FEP Audit grade). To achieve these grades, farmers must apply improved winter grazing and cropping practices, fencing off waterways and improving irrigation and effluent management.
  • More Efficient infrastructure: In addition to the 2017 pipe upgrade, farmers have also been upgrading their on-farm systems to spray irrigation.
  • Training and information: We offer education and training to farmers for nutrient management and irrigation efficiency. We are also facilitating soil moisture monitoring and providing weather station data to all our farmers;
  • Dilution pipelines: Last year we installed two pipelines to return surplus water to the Lowry Drain and St Leonards Drain, when available, to try to replicate some of the seepage which has been lost due to our more efficient pipe network.
  • Catchment leadership: 33 independent irrigated farmers from our catchment are members of our collective approach to managing water quality;    
  • Beyond Good Management Practice: To encourage further efficiency and reduce nutrient loss, we are introducing the concept of going beyond good management practice for farmers

Achieving these improvements are a long-term project for AIC and it will take some time for groundwater to respond to on-farm changes. In the meantime, we will to continue to monitor water quality in groundwater, tributaries and mainstem rivers and review and adapt our environmental strategy to respond to changes in the environment.

But we want to do more and soon we hope to apply these additional measures as part of a mitigation package that we have been working on with the Hurunui Waiau Zone Committee:

  • Managed aquifer recharge: We are looking to construct some strategically placed soak pits to introduce clean water into aquifers to reduce nutrient concentrations.
  • Further monitoring: We have identified all domestic supply wells within our scheme area and will be monitoring them for water quality this year. 

Overall, increased efficiency brings many benefits including reduced nitrate leaching in the shoulders of the season, lower sediment run off, reduced faecal contamination and phosphorus load in rivers. It was also the main driver in the Pahau River winning the most improved river award last year for E. coli reduction.

We are focussed on achieving improved water quality and will continue to work with our farmers to deliver results for our community.

If you have any questions regarding any of the matters outlined here, please contact the AIC office on 03 315 8984.

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