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  Environment » Environmental Information » Environmental indicators » Rivers and streams: monitoring and reporting » River biology » Data and trends

Data and trends

The link below points to a file that contains the source data to this indicator's graph and any additional data. The file is in comma separated (csv) format and intended to be opened in spreadsheet software.

Download the data file (1 kb, 1 seconds to download, 56k modem)

Find out more about river biology.

The following conventions apply for the graphs below.  

  • The ecological health of streams based on macroinvertebrates is grouped into the interim classes of 'excellent', 'good', ‘fair’, and 'poor'1.
  • Graphs represent the cumulative percent of wadeable stream length in the region shown by increasing percentage values, based on random site selection of different sizes of streams. 
  • Higher macroinvertebrate and habitat indicators represent better ecological health while very high aquatic plant indicators are indicative of poorer health.
  • The ecological health data for different parts of the region are expressed as the percentage of randomly selected sites sampled during summer over 2012 to 2014, and not as percentage of wadeable stream length (as explained in the technical report- The ecological condition of Waikato wadeable streams based on the Regional Ecological Monitoring of Streams (REMS) Programme)

Ecological health indicators, showing interim condition classes for macroinvertebrate health1, over 2012-14 for Waikato wadeable streams expressed as a percent of regional stream length on developed land:

 Graph river biology


Interim macroinvertebrate health classes over 2012-14 for sites sampled in different parts of the Waikato region (for ASPM):

Graph river biology

 

The following conventions apply for the graphs below.

  • 'Undeveloped' sites are those with catchments that have more than 90 per cent of their area in unmodified vegetation.
  • 'Moderately developed' sites have 51-90 per cent of their upstream catchment area remaining in native forest. 
  • 'Highly developed' sites have 11-50 per cent remaining in forest cover. 
  • 'Very highly developed' sites have less then 10 per cent of their catchment remaining in forest cover. 
  • Urban sites are all located within Hamilton City and were sampled once in 2006. 
  • The ecological health data for other land use classes are from sites sampled over 2005-2008 (see the technical report: Spatial and Temporal Patterns in the Condition of Waikato Streams Based on the Regional Ecological Monitoring of Streams (REMS) Programme). 


Ecological health of the region’s streams declines progressively with increasing levels of catchment development, and is lowest in urban streams influenced by stormwater.

 

 Habitat quality declines markedly with catchment development and is lowest in streams draining catchments almost entirely developed for agriculture. Lower habitat quality is mainly because of the lack of riparian forest cover and increased bank erosion along streams in developed pastoral catchments, although it can also partly reflect the low slope of many lowland stream channels. Habitat quality is rated higher in urban streams than in highly-developed pasture streams because many streams in Hamilton city flow through vegetated gullies.

Long-term trends in macroinvertebrate metrics show that some are declining and some are increasing over time at particular sampling sites. Because the long-term sites have not been randomly selected, conclusions cannot be drawn about regional trends in wadeable stream health. However, across the 37 sites on developed land that we have sampled for at least 10 years (see map), there is an overall decline in MCI which was developed as an indicator of water quality. There was no change over this time in ASPM which integrates a wider range of effects. Overall, across the 5 long-term monitoring sites where riparian management has been carried out there is an overall improving trend in both stream health metrics.

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