Rivers and streams

The Auckland region contains over 10,000 kilometres of freshwater streams and rivers ranging from tiny forest streams to large urban waterways.

Stream water comes from all the seeps, springs, and headwaters high in a catchment area. As these flow downhill they start to join up, eventually creating a permanent freshwater stream that flows out to sea or into a lake.

Many of the region's streams are just a few kilometres long and often flow quite slowly because the land is relatively flat.

Important factors that influence the health of a stream and the types of life (ecology) in and around it are the:

• riparian vegetation - the trees and shrubs that grow along the stream banks. These provide shade that affects the water temperature and also influences the water level in the stream, the degree of flooding and stream bank erosion, and the amount of woody debris and organic material in the stream.
• land use in the surrounding catchment area - the main type of land use around the stream and the amount of land disturbance in the catchment are both very important influences on the overall health of the stream. The land use strongly affects the types and varieties of stream habitat and the amount of riparian vegetation growing along the stream banks.
• rock type - this affects the mineral content of the streams that flow across them and the type of stream bottom that forms. Most of the land in the Auckland region consists of soft clays and sands, hard volcanic rocks, or other types of hard rock.
• stream bottom - this influences the types of aquatic organisms and plants that can live in the stream. Soft-bottomed streams are found on the clays and sands while hard-bottomed streams are found on volcanic and other hard rocks. About 95% of the streams in the Auckland region are soft-bottomed.

The mix of different rock types, stream bottoms, and catchment areas throughout the Auckland region produce a wide variety of freshwater habitats. This, coupled with New Zealand's geographical isolation, means that many of the fish, insects, plants, amphibians, birds, and invertebrates found in and around our streams are unique.

The ARC is monitoring more than 60 streams in the Auckland region. It has classified each stream by the type of catchment area it flows through - urban, rural, forestry, or native bush.