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Omaka River

The Omaka River arises in the Southern Valley hills of South Marlborough. This is one of the dryer areas of Marlborough where annual rainfall can be as little as 600mm. Greywacke is the dominant geology of the steep, rocky hills of the Southern Valleys. 

Many of the streams draining the Southern (Wairu) Valleys are intermittent and tend to dry up in the lower reaches during the summer. As a result groundwater for the irrigation of crops and for domestic drinking water is in high demand on the lower plains. Viticulture is the dominant land use on the plains, historically dairying also occurred, but has nearly disappeared. Over the last ten years viticulture has grown from 900 hectares to over 9,000 hectares.

The high country areas are predominately pastoral with some exotic forestry. The lower tributaries of the Omaka (the Taylor and the Opaoa) flow through Blenheim, the biggest urban centre (approx. 25,000 population) in Marlborough. Water quality in the lower reaches is affected by stormwater runoff from the town. The Taylor River and Lower Opaoa are valued as recreational rivers with swimming and kayaking being popular during the summer months. In addition there are numerous reserves through which the rivers flow which are popular with walkers and picnickers.

Sites 7

Monitored sites in the Omaka 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
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 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.