Waterway Management

Stock exclusion from waterways

The exclusion of livestock from waterways, provides significant benefits for the conservation and sustainability of our natural ecosystems.

One of the primary environmental benefits lies in the substantial improvement of water quality, as preventing livestock from contaminating water sources with faecal matter, pathogens, and sediment reduces the risk of waterborne diseases and ensures cleaner, safer water for both humans and wildlife.

The exclusion of livestock serves as a potent tool in the prevention of erosion along riverbanks, safeguarding the stability of these critical areas and preventing sediment runoff that can degrade water quality. Fencing waterways contributes significantly to habitat conservation by preserving and restoring vital riparian zones, which are essential for diverse species of invertebrates, fish and birds, both as primary habitat and as wildlife corridors.

Fencing is an expensive mitigation strategy in the short term. However, when implemented well and with good stock management practices, fencing effectively excludes livestock from waterways for many years after it is erected. Over a lifespan of 20–30 years the cost-effectiveness of fencing improves, and can sustain good water quality for decades*.

Compliance with environmental regulations also underscores the necessity of stock exclusion, promoting a harmonious coexistence between agriculture and ecological preservation. The exclusion of livestock from waterways represents an indispensable strategy for maintaining the health and sustainability of our water ecosystems, underpinning the broader goals of responsible land and water management.

Within Aotearoa New Zealand, stock must be excluded from rivers, lakes and wetlands within in certain timeframes depending on the type of stock, slope and intensity of grazing according to the Resource Management (Stock Exclusion) Regulations 2020. Excluding stock from waterways can reduce the negative harm caused to mahinga kai values and negative effects on stream bank stabilisation, erosion, and water quality.

Steeply sloping shallow streams 1m or less wide are exempt from these regulations. However, research indicates an average of 77% of the national contaminant load comes from exempt streams in flat catchments dominated by pasture. When looking at on-farm mitigations to reduce contaminant loads from these streams, consider that:

  • Exempt streams are mostly headwaters. Not excluding stock from these waterways can make it more difficult for land stewards downstream to improve water quality.
  • To substantially reduce contaminant losses to exempt streams, mitigations such as stock exclusion are needed, particularly on farms where fencing larger streams is not effective.
  • Where stock exclusion is prohibitively expensive, less costly strategies should be considered, such as reducing fertiliser rates, using less water-soluble forms of fertiliser, and grazing gullies later in the winter. Such measures can also act as a backstop if fencing fails to exclude stock.


Stabilising waterbody banks and channels

The destabilisation of waterbody banks and channels typically occurs when water wears away at the banks of a waterway. While this can naturally occur, human activities can increase the rate of this occurring. Deteriorating water quality, changes in river morphology, and potential effects on agricultural production can all be caused by decreased riverbank stability. This can increase the amount of sediment and nutrients entering waterways, which is exacerbated when combined with unmanaged riparian zones. Waterbody banks can be stabilised by successfully implementing erosion control measures that can reduce the rate of erosion, with often the most effective strategy to plant vegetation to stabilise soil and reduce the impact of flooding and surface run off.

Manage fish passage

New Zealand galaxid native fish
Figure 1: Many native fish like those that belong to the galaxid family, migrate between freshwater and the sea. This means any barriers to their movement can be a big threat to their lifecycles.

To complete their life cycles, many freshwater species in Aotearoa New Zealand must migrate between freshwater and the sea or upstream and downstream. Fish may not be able to reach the habitats they require to complete their life cycle if their movement upstream and downstream is slowed down or stopped entirely. Fish passage refers to the connection between all habitats a freshwater species needs to complete its lifecycle. Therefore, enabling fish migration is essential to ensuring the completion of freshwater lifecycles.

Enhancing Riparian Vegetation

The land on either side of a waterway is known as a riparian zone. Riparian zones can enhance water quality by lowering the amount of nutrients and sediments entering the watercourse when the strips of land are fenced and planted. To gain maximum environmental benefits and increase the chances of successful revegetation, the plants in riparian zones must be maintained. The DairyNZ Riparian Planner provides a step-by-step procedure that outlines the appropriate plant species to utilise, and to plan the fencing and restoration of waterways and wetlands.

The below diagram demonstrates the general approach to successful planting.

Effective planting technique

Source: DairyNZ

Protecting and enhancing wetlands

Wetlands have very high ecosystem, cultural and water quality values. They can serve as carbon sinks, remove excess nutrients and sediment, and support high levels of biodiversity. However due to changes in land use, Aotearoa New Zealand's overall area of wetlands has drastically diminished.

Improve Instream Habitat

Rivers and streams provide unique habitats for native freshwater species. However, due to the alteration of numerous freshwater ecosystems and the degradation of water quality, many native freshwater species in New Zealand are threatened with extinction. As a result, their natural habitats are no longer suited for their survival. Improving instream habitats allows for ecosystems conditions to restore, therefore enabling freshwater population sizes to increase. There are numerous approaches to restore instream habitats, the Department of Conservation has identified a few successful restoration initiatives where habitat improvement has been achieved.

See ORC - Environmental Considerations for Clean Streams.

Environmental DNA (eDNA)

Tiny traces of genetic material, or environmental DNA (eDNA), can now be detected to help understand the current health of the water and the species it supports.