Health of Hamilton's streams

Hamilton city’s streams are affected by pollutants from a number of sources. These streams have poor aquatic life and habitat but Environment Waikato and Hamilton City Council are working to improve this.

On this page:

• Pollutants affect water quality
  
• Poor aquatic life and habitat
  
• Working on improvements
  

Pollutants affect water quality

Hamilton city and its surrounding land is drained by a series of streams that flow into the Waikato River. Pollutants from agriculture, commerce, industry and residential areas have reduced the health of these streams.

Contaminants include high levels of fine sediment that smother stream beds. Also present are pollutants such as faecal bacteria, which pose a human health risk, and ammonia, which can be particularly toxic to fish. Leachate draining from old rubbish dumps contributes to high ammonia levels in two Hamilton streams.

Poor aquatic life and habitat

Four years of monitoring by Environment Waikato has found poor aquatic life and habitat.

• Hamilton's streams have only a few pollution-tolerant animals¹.
  
• The streams have poor biodiversity - they don’t have the expected range of sensitive aquatic species, including native fish, and those that do survive are hard to find.
  
• There is a lack of habitat for aquatic plants and animals - in some cases habitat has disappeared completely because stream beds have been realigned and concreted over.
  
• There are few native aquatic plants and a lack of rocks and woody material - this means little shelter or food is available for aquatic animals, particularly where silt covers stream beds.
  
• In some cases, there are no riparian (stream bank) shrubs and trees, which provide shade and keep waters cool. Stream temperatures can sometimes be higher than the stress levels for resident plants and animals. Riparian strips also provide food for some animals, can filter some pollutants before they enter the stream, reduce erosion and buffer flood and drought extremes.

Working on improvements

Riparian habitat in streams can be improved by planting the stream bank, while being careful not to affect urban stormwater systems. We are working with the Hamilton City Council to identify ways to improve the habitat and water quality of the city’s streams.

Footnote:

Wilding, T.K. 1998: The State of Hamilton Streams. Environment Waikato Technical Report 1997/17. Environment Waikato, Hamilton.