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Waitohu Stream

The Waitohu Stream is located in the Kāpiti Region north of Ōtaki. With headwaters in the Tararua foothills, the river drains a catchment area of 54 square kilometres before discharging into the Tasman Sea at Ōtaki Beach.

The stream supports many native fish species; some of these, such as the shortjaw kōkopu, giant kōkopu, lamprey and longfin eel, are nationally threatened.

The Greater Wellington Regional Council carries out routine monitoring at two sites within the Waitohu Stream Catchment area. A monitoring site is also in the Mangapouri Stream, a tributary of the Waitohu Stream. These sites are all monitored as part of a programme specifically designed to measure the health of rivers in the Wellington Region.

The Waitohu Stream Catchment area incorporates a range of land uses, including native and exotic forests, which make up 40 percent of the catchment area, as well as pastoral farmed floodplains, lakes, wetlands, sand dunes and urban areas.

The overall water quality of the Waitohu stream and its tributaries is varied. In the upper catchment, where indigenous forest is the dominant land cover, measures of water quality and ecosystem health are typically very good. However as pastoral and urban impacts increase with the distance downstream, the measure of water quality and ecosystem health deteriorates.

The main pressures on the water quality of the Waitohi Stream are nutrient contamination from human/animal sources, which is exacerbated by low flows during dry summers. 

Sites 3

Monitored sites in the Waitohu Stream catchment

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Scientific Indicators
Scientific data for this catchment

This dashboard shows information on the data collected by the regional councils for water quality indicators, analysed as state and trend.

The state for the catchment is represented by the median concentration for the parameter across all sites within the catchment and then compares that value to the quartiles for all monitored sites in New Zealand.

Click on the parameters state icons to compare this catchment with others in the region.

  • State

    State shows how the median of samples from this site compares to other sites

  • Trend

    Trend shows how the quality of water is changing over time. Depending on the sampling history duration, five and ten year timescales are available:

Can I trust this data?

The Cawthron Institute has worked alongside regional councils to verify the processes and methods used for data collection, laboratory analysis of samples collected and the statistical analysis and interpretation of the results presented.

If all Cawthron ticks are green, then you can trust this data. However, if one or more ticks are orange, then conclusions should be treated with some caution.

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

Can I trust the data?
Data Collection

All samples were collected using approved field protocols and have been analysed in accredited laboratories. Therefore the data shown here has been collected and analysed following best practice.


All samples were collected using approved field protocols and have been analysed in accredited laboratories.

Trend - Adjustment for flow

This data is not flow adjusted. National guidelines suggest that flow-sensitive variables are flow 'adjusted' before trend analysis. Therefore, any trends shown here may be affected by variations in flow across sampling occasions.


E. coli



Black disc





Total Nitrogen


Total Oxidised Nitrogen


Ammoniacal Nitrogen



Dissolved Reactive Phosphorus


Total Phosphorus

Download Data

.ZIP file of indicator readings for all sites in New Zealand

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