Understanding E. coli


2 min read

The mission Fieldwork and sampling How are farmers involved? Scenario modelling Meet the scientist Additional resources

There is currently research underway on understanding, managing and reducing E. coli levels to improve water quality. E. coli is an important water quality challenge facing farmers, with many waterways having E. coli levels that exceed national water quality targets. A new multi-year programme of work, led by AgResearch and jointly delivered by DairyNZ, is working with farmers to understand and reduce E. coli losses into waterways.

The mission

E. coli is an important water quality challenge facing farmers, with many waterways having E. coli levels which exceed national water quality targets, the research aims to:

  • Assess how much E. coli is present in dung and soil, how much of this ends up in streams, and how it gets there.
  • Identify practical mitigation options to reduce E. coli losses into waterways and develop management advice that can be shared with farmers nationally on how to reduce E. coli losses into waterways.
  • Study what happens to E. coli in streams to understand if it is flushed out, or stays in the sediment.
  • Develop a model to estimate E. coli reductions in pastoral catchments when mitigations are actioned.
  • Use this model to assess what level of E. coli reductions are possible in pastoral catchments, and use this information to inform regulatory decisions.

Fieldwork and sampling

The first phase of work will focus on developing a water and stream sediment sampling strategy in the Nguturoa catchment in Manawatū-Whanganui. This will help the project team better understand E. coli pathways and concentrations as multiple stream networks flow from the headwaters in the hills, through different land uses to the lowlands. Samples will be used to inform catchment modelling and mitigation strategy design.

How are farmers involved?

The project team are working alongside the Nguturoa Catchment Group which includes dairy, sheep and beef farmers and lifestyle block owners. The catchment group has identified E. coli as the key issue in their catchment. Farmers have been taking water quality samples for a number of years and have provided catchment maps showing fenced and planted areas. Farmers are also helping select stream sampling sites and carrying out sampling.

Scenario modelling

The project will also model E. coli runoff from pasture to the stream network at the AgResearch Invermay farm in Otago, and the long-term impacts of land use retirement at the Whatawhata site in the Waikato.

Meet the scientist

Dr Katrina Macintosh, Senior Scientist Water Quality

Katrina joined DairyNZ four years ago, after working as a university research scientist at Ulster University, and Queen’s University Belfast, in Northern Ireland. She has expertise in phosphorus and leads DairyNZ’s freshwater science research programme.

Research team

Dr Craig Depree, Principal Scientist Water Quality

Craig is responsible for developing DairyNZ’s water quality research programme, and often leads freshwater science evidence preparation in plan change hearings and the environment court. Craig came to DairyNZ after spending 18 years as a water quality scientist at NIWA.

Research team

This study is being lead by Dr Richard Muirhead in collaboration with AgResearch

Last updated: Feb 2024
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