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Wairau River

The Wairau is a large braided river and is the largest river in the Marlborough region. Its catchment accounts for 25% of the entire Marlborough Region. It starts in the high alpine ranges between the Spenser Mountains and the St Arnaud range and flows for 257km from source to sea. Catchments located on the north banks of the Wairau have a wet climate and are dominated by native forests, south bank catchments have a dry climate and are dominated by pastoral hill country farming, exotic forestry and viticulture. 

Tributaries of the Wairau River are used to generate hydroelectric power with further hydroelectric schemes planned for the future.


Water quality is generally good but there is some deterioration in water quality in the lower reaches. Recent trend analysis carried out by NIWA shows that nitrogen levels are increasing in the lower reaches, whilst phosphorus levels are increasing in the upper reaches.

The Wairau is important for groundwater recharge in the lower plains, where irrigation from groundwater is in high demand. Blenheims drinking water supplies are dependent on groundwater quality in the lower Wairau plains. Stock access to rivers and streams, septic tanks and irrigation are some of the pressures on the sub-catchments of the Wairau, particularly in the lower catchment. A number of spring fed streams arise within the Wairau catchment, including Mill Stream and Spring Creek.

Sites 15

Monitored sites in the Wairau River 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.

State

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.

Bacteria

E. coli
State
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Trend
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Clarity

Clarity

Black disc
State
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Trend
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Clarity

Turbidity
State
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Trend
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Nitrogen

Nitrogen

Total Nitrogen
State
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Trend
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Nitrogen

Total Oxidised Nitrogen
State
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Trend
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Nitrogen

Ammoniacal Nitrogen
State
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Trend
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Phosphorus

Phosphorus

Dissolved Reactive Phosphorus
State
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Trend
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Phosphorus

Total Phosphorus
State
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Trend
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Download Data

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

 LAWA Partners shall not be liable, whether in contract, tort, equity or otherwise, for any loss or damage of any type (including consequential losses) arising directly or indirectly from the inadequacy, inaccuracy or any other deficiency in information supplied irrespective of the cause.  Use of information supplied is entirely at the risk of the recipient and shall be deemed to be acceptance of this liability exclusion.