Practical solutions for catchments

A whole community approach

Tuna (eels) and kōura (freshwater crayfish) are signs of a healthy waterway, and their presence brings real value to the communities connected to it.

In the Pōkaiwhenua catchment in South Waikato, eDNA sampling has revealed a range of species, including tuna, kōura and cran's bully. With this knowledge in hand, the local community is working to enhance and protect the habitats these species rely on.

Many farms have smaller streams, and shading them can make a real difference to water quality downstream. Streams are classified by size. A first-order stream is the smallest. When two streams join, they form a second-order stream, and so on as they grow.

These lower-order streams are also the cheapest and easiest to plant. When exposed to direct sunlight, these small streams can reach temperatures over 30°C. Planting just one kilometre of stream can reduce water temperature by up to 5°C.

Science tells us that when 60–70% of a stream is shaded by riparian planting, it helps reduce bank erosion, cools the water, suppresses weed growth, improves oxygen levels, and reduces sediment, all of which creates a better habitat for aquatic life to thrive.

DairyNZ partnered with the Raukawa Charitable Trust and the Pōkaiwhenua Catchment Group. The project was grounded in learning and knowledge sharing, with Raukawa’s input helping farmers and project partners understand the historical and cultural context of their land and take a more holistic view of how farm management affects waterways.

It’s also strengthened relationships with hapū (Māori sub-tribes) and supported planting in less productive areas, giving those spaces purpose for native biodiversity and community connection.

As part of the Sustainable Catchments programme, DairyNZ is developing shade values to help you understand what’s needed in your area. We also encourage you to assess the types of streams on your farms – it’s a valuable step towards healthier waterways.

A great place to start is by taking an eDNA sample to find out what’s living in your streams, and working with your local community to help protect it.

Visit dairynz.co.nz/riparian-planting for more about riparian planting.

Edge-of-field-mitigations

Edge-of-field mitigations (for example, wetlands or bio-reactors) are being piloted in the Waimea catchment in Southland to complement farm-level changes and further reduce catchment losses to help meet community aspirations.

While this work is focused on Waimea, the insights and solutions tested here are designed to be practical and adaptable for farms across New Zealand.

Due to its characteristics, the Waimea catchment is prone to accumulating nitrogen (N), and groundwater and surface N levels exceed the standards required in the Southland Water and Land Plan. The overall water quality isn’t where the community wants it to be.

There are also growing concerns about whether current flood infrastructure can keep up, with projections indicating increased risks for flood management downstream.

DairyNZ collaborated with Thriving Southland and the local catchment group to identify appropriate areas to trial edge-of-field mitigations.

Research shows that wetlands can typically reduce N by 20-80%, depending on factors like temperature, retention time and incoming N levels. The research also shows that wetlands are effective at trapping sediment and phosphorus.

On farm, farmers are seeing the wetlands at work during rainfall events, noting the flow is calmer and less forceful. The wetland fills up, and over the following three to four days, water levels gradually recede. It’s a clear, practical example of how wetlands help slow peak flows and reduce pressure downstream.

A key aim of the project is to demonstrate that these tools are practical and effective, and won’t interfere with farm operations, including drainage, which is especially important in regions such as Southland.

Edge-of-field mitigations can often be installed in less productive areas of the farm, making good use of land that’s not currently providing a significant return. As well as helping to reduce N loss, these tools can slow water flow, support biodiversity, and enhance the look and feel of the farm environment.

Find out more about the Waimea catchment project at dairynz.co.nz/waimea

Raising farm system efficiency

Working with more than 30 farms in South Canterbury and Waimea, this project is exploring practical system changes that could be applied on farms nationwide. The goal is to support farmers in maintaining profitability while further reducing nitrogen (N) losses and greenhouse gas emissions (GHG).

The project’s focus in South Canterbury is to help farmers understand opportunities to meet Environment Canterbury’s Plan Change 7, 2028 N-loss reduction targets. In Waimea, it’s about exploring options ahead of possible farm-level N-loss reductions.

The system changes being explored include updating irrigation infrastructure. One farm, for example, is shifting from long return interval systems to low application, short return interval options like pivots, which help reduce water use, improve pasture growth, and lower the risk of nutrient leaching.

Another farm had an underutilised feed pad, so by optimising it, they’re utilising supplements better and reducing losses. They’ve been able to stop growing fodder beet, reducing cultivation and input costs and lessening the risk of nutrient loss over winter.

Stocking rate is an important aspect to review, ensuring it’s optimised for the farm system and the available feed. In some cases, there are clear opportunities to better match stocking rate to feed supply, reducing N losses and GHG emissions while maintaining profitability.

The project typically uses Farmax and Overseer to understand the current farm system and its environmental footprint. Potential system changes are then modelled to assess their feasibility, financial impact, and likely effects on nutrient losses and GHG emissions.

Working intensively within specific catchments allows us to develop credible, practical solutions that can be applied across New Zealand. The focus is on identifying core principles that work no matter where your farm is – real options and approaches you can take away and adapt to your own system.

Learn more about reducing N loss at dairynz.co.nz/reduce-n-loss

About the contributors