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Waiwhakaiho River adjacent to Lake Rotomanu

This river drains an extensively developed farmland catchment and flows through six kilometres of urban New Plymouth upstream of this popular recreational area which is about 700m from the sea. Large flocks of seagulls and ducks are present in the lower reaches between Merrilands Domain and this site, near the coastal walkway and Te Rewa Rewa Bridge. Investigations have shown that bathing guideline exceedances at this site are caused by birdlife.

This site is used mainly for whitebaiting (in season), and walking.

For all sites, the Council advises:
Avoid for three days after heavy rain, if the river is high, or if you cannot see the bottom clearly.

Recreational bathing surveys over the last two summers showed that 31% (2018-2019) and 27% (2019-2020) of samples met the freshwater microbiological water quality guidelines prepared by the Ministry of Environment in conjunction with the Ministry of Health (MfE, 2003) and did not exceed the ‘Action’ level (>550 E.coli cfu/100mls).

The State of the Environment technical report showing the freshwater recreational monitoring results is available at

The Council also monitor ecological health at this site. We use an ecological index based on the macroinvertebrate communities (tiny animals including insects, crustaceans, mulluscs, worms and leeches) found in waterways to measure ecological health. 

Macroinvertebrate data for Taranaki shown on LAWA may vary from some data reported elsewhere by the Taranaki Regional Council. This variation is because the level of macroinvertebrate identification used by the TRC has some minor differences from that used by other Councils and LAWA, affecting the taxonomic richness and % EPT taxa scores. Taranaki Regional Council also uses Macroinvertebrate Community Index (MCI) scores which have been modified to reflect the conditions experienced in Taranaki, while the scores shown here are based on the National MCI scores. For more details, the full state of the environment report is available at



Can I Swim Here?
Ecological data for this site

This dashboard shows the results from macroinvertebrate sampling at this site.  It displays three ecological indicators: macroinvertebrate community index, taxonomic richness and percent EPT. 

For sites where State is 'N/A' or Trend is 'Not Assessed', there are not enough data to calculate a State and/or Trend result.  Click on an indicator to see the available historical data.


Select trend period for MCI

  • 10 years
  • 15 years
  • MCI

    5-year median: {{medians.MciMedian}}


    {{medians.MciState.Text | uppercase}}

    The Macroinvertebrate Community Index uses aquatic macroinvertebrates to assess the health of streams in New Zealand.

    MCI sample history at this site

    MCI for Waiwhakaiho River adjacent to Lake Rotomanu
    MCI score

    What do the NOF icons mean?

    Macroinvertebrate community indicative of pristine conditions with almost no organic pollution or nutrient enrichment.
    Macroinvertebrate community indicative of mild organic pollution or nutrient enrichment. Largely composed of taxa sensitive to organic pollution/nutrient enrichment.
    Macroinvertebrate community indicative of moderate organic pollution or nutrient enrichment. There is a mix of taxa sensitive and insensitive to organic pollution/nutrient enrichment.
    National bottom line: MCI score 90
    Macroinvertebrate community indicative of severe organic pollution or nutrient enrichment. Communities are largely composed of taxa insensitive to inorganic pollution/nutrient enrichment.
  • Taxonomic richness

    The median of the last 5 years of data

    {{medians.TaxaMedian || 'N/A'}}
    Taxonomic richness is the number of different taxa present in an ecological community identified to the best possible level.

    Taxa richness history at this site

    Taxa richness for Waiwhakaiho River adjacent to Lake Rotomanu
    Number of taxa
  • Percent EPT richness

    The median of the last 5 years of data

    EPT are macroinvertebrates that are sensitive to water pollution. These are Ephemeroptera (mayfly), Plecoptera (stonefly) and Trichoptera (caddisfly).

    EPT history at this site

    Percent EPT richness for Waiwhakaiho River adjacent to Lake Rotomanu
    EPT %
Can I trust this data?

The Cawthron Institute has worked alongside regional councils to verify the processes and methods used for macroinvertebrate data collection, processing of the data in the laboratory, quality control in the field and laboratory and the statistical analysis and interpretation of the results presented.

For more details on each tick, see our 'Can I Trust this Data?' Factsheet.

Can I trust the data for this site?
Data Collection

Macroinvertebrates are sampled at this site as part of council's stream health monitoring programme.

Sampling - Frequency

Macroinvertebrate sampling is done annually or more frequently at this site.  Annual sampling provides enough data points for state and trend analyses to be calculated with sufficient statistical power for trend detection.

Sampling - Protocols

This site is a hard-bottomed site and appropriate sampling protocols have been applied.  Data shown here have been collected using current best-practice based on Stark et al. (2001).

Sampling - Habitat

Macroinvertebrate sampling is done in riffle habitat at this site. Data shown here are therefore following best practice as described in Stark et al. (2001).

Sampling - Stand-down period

Macroinvertebrate samples are collected within the first two weeks after a flood greater than three times the median flow at this site. Stark et al. (2001) suggest a minimum of two weeks 'stand-down' period after a flood greater than three times the median flow. Therefore, data shown here is not following best practice and conclusions based on this data need to be treated with caution.

Processing - Protocol

Samples at this site have been processed following sampling protocol P1 (semi-quantitative - coded abundance). Data shown here is not following best practice as described by Stark et al. (2001), but are still considered robust.

Quality Control - Field

Field data collected at this site had no quality control applied to it.

Quality Control - Lab

Data processed at this site has had one of the three Laboratory Quality Control Protocols (i.e., QC1, QC2,Q C3) applied. Data shown here is more robust than data with no laboratory QC applied.

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