Tuesday, 05 March 2024 15:55

Study sheds light on contamination

Written by  Staff Reporters
The team carried out in-depth investigations in the Piako River headwater and Waitapu Stream catchments. The team carried out in-depth investigations in the Piako River headwater and Waitapu Stream catchments.

A new study shows that analyses how water flows to reach rivers and streams can help reveal what proportion of agricultural contaminants come from past or recent land use practices.

As part of the five-year Critical Pathways programme funded by the Ministry of Business Innovation and Employment (MBIE), Lincoln Agritech’s Hamilton-based scientists studied water and contaminant flows through catchments.

The team carried out in-depth investigations in the Piako River headwater and Waitapu Stream catchments, using several techniques, such as airborne geophysical surveys and high-frequency nitrate measurements.

They also looked at 47 other catchments with varying environmental and land-use characteristics in Taranaki, Waikato, and Hawke’s Bay. Here, they used a modelling method called BACH (Bayesian chemistry-assisted hydrographic separation and load partitioning).

Lincoln Agritech principal scientist, environmental, Roland Stenger says the method was developed a few years ago specifically to extract some useful information from data-sparse catchments, where more sophisticated models cannot be applied.

“The only in parameters needed are a long-term flow record and time series for two water constituents that can be used as tracers: in many catchments, that can be routinely monitored total nitrogen and total phosphorus,” Stenger says.

A tracer is a substance that can be easily tracked as it travels with the water through catchments.

Using one of two tracer combinations (total nitrogen plus electrical conductivity, or total nitrogen plus total phosphorus) the team could calculate how much of a water’s body came from deep groundwater, shallow groundwater, or near-surface water.

That’s important because near-surface water reaches rivers, streams, and lakes within minutes to days, shallow groundwater takes from a couple of months to two to three years, while deep groundwater can take decades to reach waterways.

By understanding where the water came from, water regulators can understand whether measured agricultural contaminants, such as nitrates, are the result of recent practices, or whether they reflect what happened in the past.

In most catchments studied, shallow groundwater was the most important contributor to local streams and rivers, meaning current practices have the greatest impact on the water.

Deeper groundwater, associated with long lag times, was the dominant pathway only on the North Island’s volcanic plateau.

Last month, Stenger presented the findings to Waikato Regional Council’s Environmental Performance Committee. Its freshwater policy team is now exploring how to best use this knowledge.

More like this

Is augmented reality the future of farming?

Imagine a farmer being able to tell a paddock’s pasture cover and dry matter content just by looking at it, or accessing information about a cow’s body condition score in the same way.

Catch crops a valuable tool

Along with several other organisations, Beef+Lamb NZ helped fund the catch crops for reduced nitrate leaching project. Sown as soon as possible after grazing has finished, catch crops have been the subject of a Sustainable Farming Fund project led by Peter Carey from Lincoln Agritech, with support from Brendon Malcolm and Shane Maley from Plant and Food Research and AgResearch.

Science the answer to debate

The previous government issued a call-to-action to New Zealand: double primary production export earnings while maintaining or improving water quality. 

Tool to measure water nitrates

Lincoln Agritech has unveiled an advanced optical nitrate sensor for groundwater which it says will bring a paradigm shift in New Zealand’s groundwater management.



UAE FTA welcome news

The dairy and red meat sectors have welcomed news that New Zealand will begin formal negotiations for a free trade…

Flock House and its secrets

Plans are in place to celebrate the 100th anniversary of the legendary Flock House opening its doors for the first…

$160 billion cargo shipment deal

New Zealand’s major primary industry exporters have secured shipping capability to export $160 billion worth of products over the next…

Machinery & Products

More horsepower for Puma

Case IH's introduction of AFS Connect, an option for its high horsepower tractor ranges, has now been rolled out across…

EU tractor sales hit the brakes

According to numbers sourced from national authorities, 151,800 tractors were registered across Europe in 2023, of which 26,200 tractors (17%)…

GPS in control

In a move that will make harvesting operations easier, particularly in odd-shaped paddocks, Kuhn has announced that GPS section control…

» Latest Print Issues Online

The Hound

True colours

OPINION: The watermelon party (AKA the Greens) try to portray themselves as an upright, self-righteous, caring bunch of woke, bicycle-riding…

Peace at last?

OPINION: Good news for hunters as Forest & Bird have "paused" legal action against the Fiordland Wapiti Foundation and agreed…

» Connect with Rural News

» eNewsletter

Subscribe to our weekly newsletter