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Shag River

The Shag River/Waihemo rises in the Kakanui Mountains, before flowing almost 90 km in a south-easterly direction to the coast, entering the Pacific Ocean just south of Shag Point/Matakaea.  It drains a total catchment area of 550 km2. .

 The Māori name for the Shag River is Waihemo (Wai=water, hemo=to go to ground), possibly a reference to the very low flows observed in the lower reaches of the river during summer

The Shag River and its tributaries (McCormick’s Creek, Deepdell Creek, Sweetwater Creek, Coal Creek and Shingly Creek), are located within a catchment that encompasses valley flats, gently rolling hills and steeper mountain ranges. Much of this land is highly fertile, and pastoral and arable farming is practised over wide areas with a smaller amount of forestry and horticulture.A notable feature of the catchment is the presence of a large goldmine at Macraes Flat.

Average annual precipitation in the Shag catchment is 595mm.

Recreational activities in the Shag River/Waihemo include swimming, whitebaiting and trout fishing.   

The most significant active recreational pursuit carried out on the Shag River/Waihemo is angling and the river supports a regionally important trout fishery. The lower Shag River also supports a regionally significant whitebait fishery.

There are four species of introduced sports fish found in the Shag catchment. Brown trout are easily the most common species of fish in the catchment. Eel species and Galaxias species are also present throughout the length of the Shag River catchment. Freshwater crayfish occur in the upper reaches of the main river and in Deepdell and Tipperary creeks.


Sites 2

Monitored sites in the Shag 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.


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


Samples are collected bimonthly at this site. Proposed national guidelines suggest monthly sampling is required for trend analysis. Therefore, any trends shown here are less robust than those calculated from data collected monthly. New Zealand's councils are currently reviewing their sampling procedures and aim to adjust their sampling frequency to monthly. This will increase the robustness of the trend analyses.

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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