Most rural streams flow through pasture for most, or all, of their length. Almost half of the land (224,000 hectares) in the Auckland region is covered by pasture. Horticulture covers another 11,000 hectares so some rural streams flow through land used for crops, vineyards, or orchards.

Scrub, exotic forest, native bush, lifestyle blocks and small settlements are also scattered through rural catchment areas.

The health of a rural stream and the types of life (ecology) in and around it are influenced by the following factors.

Riparian vegetation

Rural streams have fewer trees and shrubs growing along their banks than forestry or native bush streams.

When present, the riparian vegetation provides plenty of shade throughout the year. This protects the water from direct sunlight and keeps it at a constant, cool temperature.

All of these benefits are removed wherever the riparian vegetation has been cleared. A lack of shade also encourages algae and other nuisance plants to grow. These decrease the levels of dissolved oxygen in the water and make the stream less suitable for native aquatic organisms.

Land use in the surrounding catchment

At least 35% of the land in a rural stream's catchment is used for rural activities. Exotic forest, if present, covers less than one third of the catchment area and urban development covers less than 5% of a rural catchment area.

Almost all of the land in a rural catchment area has been disturbed in some way by human activities, particularly by land clearance that has removed the original native bush cover.

Stock has an important influence on a rural stream. When they have access to a stream, or cross directly through a stream, they reduce the water quality by stirring up sediment and making the water turbid, and by increasing the amount of bacterial contamination. They also trample and erode the stream banks.

High levels of nutrients (such as nitrogen and phosphorus) and pesticides often leach into the rural streams as a result of the land use activities. These encourage the growth of algal slimes and other nuisance plants that reduce the amount of dissolved oxygen in the water.

All of these factors mean that the water quality and physical environment in rural streams are usually - but not always - better than urban streams, but not as good as native bush or forestry streams.

Typical water quality of a rural stream

The low levels of urban development in rural catchments means the soft-bottomed rural streams in the Auckland region often have better water quality than urban streams, but the land use activities make it worse than forestry and native bush streams.
In particular, rural streams have:

low levels of dissolved oxygen
high water temperatures
increased levels of suspended solids and turbidity
increased levels of nitrogen and phosphorus
high levels of faecal coliforms.

Typical invertebrate ecology of a rural stream

Most rural streams in the Auckland region provide soft-bottomed stream habitats, suitable for invertebrates that prefer slow-moving water.

Rural streams that have particularly poor water quality and / or poor physical habitats may have less than 10 different taxa that are similar to those in urban streams. Take this link for more information about urban stream taxa.

What is being monitored?

The Freshwater Ecology Programme is monitoring the biological health and the physical condition of some streams in the Auckland region.

The Rivers & Streams Water Quality Programme is monitoring the water quality.

When the results from both programmes are combined, they give a good indication of the overall health of a stream and its physical, chemical, and biological condition.

Technical Publications

The ARC has a number of technical publications relating to this subject. Follow this link to see the full list of ARC technical publications.

Continue to Forestry streams

You are here: Home › Environment › Water › Rivers and streams

Page top