Nitrate Trends Improving.
Five-Year Trends Show Accelerating Improvement.
For more than a decade, Central Plains Water Limited (CPWL) has tracked groundwater quality through quarterly monitoring of 20 strategically placed wells across irrigated and non-irrigated land. These long-screened bores are sampled using advanced low-flow techniques that capture water from the most vulnerable part of the aquifer, giving a transparent view of change over time.
Lincoln Agritech assessed nitrate data for CPWL recently which repeated an assessment from a year ago and showed that average annual nitrate concentrations were generally lower in the 2016-2025 decade than they were in the decade from 2015-2024.
“Good Management Practices are working at scale through the scheme’s collective management. Independent science confirms nitrogen reductions.”
– Susan Goodfellow, CEO, Central Plains Water Limited.
Lincoln Agritech then looked at the data in five-year increments and found something much more interesting: nitrate levels started dropping in far more wells in the later 5-year period. Between 2016 and 2020, only 10% of wells showed clear signs of falling nitrate levels, but between 2021 and 2025, this jumped to 60% of wells.
The downwards trend appears to have been influenced by both improved land use management and unusual climatic patterns in the early years of the scheme. In 2015 and 2016 there were two very dry winters, which resulted in very low groundwater levels and low nitrate concentrations being recorded in many Canterbury bores by the end of summer 2017. This dry period was followed by a very wet winter which appears to have resulted in a nitrate peak by the end of 2017/early 2018. Nitrate concentrations in many wells have shown a downward trend over the years.
Lincoln Agritech has advised that further investigation is required to fully understand the drivers behind these changes. However, the pattern suggests that both climatic conditions and improved land management practices are influencing nitrate concentrations over time.
This builds on earlier modelling work linking on-farm actions to groundwater outcomes.
