Contaminant reduction is central to improving water quality, but we also need to take a more holistic approach to better address the overall health of waterways, including things like riparian planting.
Inside Dairy
2 min read
Cate McIntosh has planted the Mt Harding stream on her Methven farm, where eDNA sampling with DairyNZ’s Dr. Belinda Margetts revealed its aquatic life.
Healthy waterways are resilient ecosystems that support wildlife, allow for safe recreational use and benefit surrounding communities as well as the environment.
Current regulations focus mostly on reducing single contaminants, such as nitrogen. However, this approach may not be the most effective for improving waterway health for many of our streams and rivers, and we’re pushing for a stronger emphasis on ecosystem health in both policy and practical actions.
Farmers have made significant progress in adopting good management practices, such as excluding stock and reducing contaminants, to restore water bodies on farm, but there is still work to be done to achieve waterway health in many catchments. A holistic approach combines various tools to enhance the overall health of waterways.
Measures such as riparian planting— which helps create the right instream environment for aquatic insects and fish—can have a significant positive impact on achieving ecological goals.
Riparian planting efforts also help with carbon capture and actively support biodiversity, both of which are important for our international markets.
There are benefits to the sector in being proactive in improving waterway health ahead of regulation, and the gains from restorative actions are far reaching.
The gains from restorative actions are far-reaching.
Fenced-off waterways save farmers time by reducing the need to retrieve stock from those areas. Shade from planting lowers water temperatures and reduces the sunlight that nuisance algae (periphyton) need to grow.
Some councils require lower nitrogen load reductions on farms for waterways that are shaded. Shade also cuts weed growth, reducing maintenance needs and lowering flood risks from clogged channels.
With Mt Harding stream running through her Methven farm, Cate McIntosh recognised the need to support the waterway’s health. She has been chipping away at this for the past eight years, planting two-thirds of the waterway with only a kilometre left to cover.
“I knew direct sunlight wasn’t good on the waterbody and some form of cover and shade are good for the fish and things living in the water,” Cate says.
“I started by planting some plants funded by Environment Canterbury, then began growing my own. I’ve been doing one section at a time to keep it manageable.”
As the plants have become established, management has become easier. She enjoys seeing her efforts pay off with mature plants, fewer weeds, shelter for stock, and thriving birdlife.
Extensive planting is taking place in the Pōkaiwhenua catchment this summer. DairyNZ is working alongside the Raukawa Charitable Trust and Pōkaiwhenua Catchment Group in a holistic, collaborative effort to improve waterway health, aligned with the outcomes desired by the community.
More than 15,000 plants are being planted around Tokoroa’s Whakauru Stream. This work aims to improve water quality so native species can thrive in and around the stream, a tributary of the Pōkaiwhenua Stream.
Monitoring shows good existing numbers of native eels (tuna), freshwater crayfish (kōura) and many more species.
Learn more at pokaiwhenua.org.nz or about catchment groups at dairynz.co.nz/catchment-groups
Riparian planting
Riparian plants act as filters to trap contaminants such as chemicals, nutrients, sediment and bacteria before they enter the waterway. They’re also great for shade, and support a biodiverse habitat.
Managing and protecting wetlands
Wetlands help reduce flooding by acting as a sponge, and they improve water quality by trapping, filtering and removing nutrients and contaminants, especially sediment, nitrogen and phosphorus. They also provide a habitat for biodiversity.
Improving fish passage
Fish need to move up and down waterways to feed, breed and migrate between the sea and freshwater to complete their life cycle. Anything that stops fish movements is called a “fish passage barrier” and should be removed where possible.
Farm management practices
Good management practices reduce the leaching and loss of contaminants that affect both human health and the health of ecosystems and waterways.
Check out dairynz.co.nz/waterways for more information
Dr David Burger
DairyNZ general manager farm solutions and policy
Dr Belinda Margetts
DairyNZ senior freshwater ecologist
This article was originally published in Inside Dairy February-April 2025.