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Manuherikia River

The Manuherikia catchment is located north-east of Alexandra, Central Otago, it is a tributary of the Clutha River/Mata-Au and has a catchment area of 3035 km2. It can be divided into two major catchments, the Ida Valley which is separated from the Manuherikia Valley by the Poolburn Gorge (in the Raggedy Range).


The Manuherikia climate is considered to be the most continental type in the country with cold winters and warm summers. It is away from the effect of the sea and has the surrounding mountains which shelter it from rain-bearing storms. Average annual rainfall in the Manuherikia Valley is between 400 and 500mm.

The low rainfall has led to the development of extensive water storage and irrigation schemes. Three reservoirs have been established in the Manuherikia catchment to provide water for irrigation. Poolburn Reservoir was constructed in 1931, with a capacity of 26 Mm3. Falls Dam was built in 1935 to capture the high rainfall water supply in the northern high-altitude part of the catchment and has a capacity of 11 Mm3. Manorburn Reservoir was built in 1935 and has a capacity of 51 Mm3. 
The irrigation distribution system consists of a network of manually controlled, unlined, open water races. 
The Blackstone Hill, Omakau, Manuherikia, and Galloway irrigation schemes take water out of the Manuherikia River, which is partly controlled by the releases of Falls Dam, and distribute the water through a network of open water channels to irrigate the Manuherikia Valley bottom. The Poolburn Reservoir is used to store water to irrigate Ida Valley. Water from the Manorburn reservoir is partly diverted into the Manuherikia Valley over an open water race to irrigate the upper Galloway Irrigation Scheme. Therest of the Manorburn water is used for irrigation in the Ida Valley.

Land use in the upper catchment of the Manuherikia and Ida Valley’s is primarily extensive sheep and beef grazing. Due to irrigation, the mid and lower reaches of the catchment are dominated by comparatively higher intensity farming with smaller farms and higher stocking rates relative to the upper catchment. In the past few years there has been an expansion of wintering dairy herds and in June 2009 the first dairy platform was established near Omakau. Over the last decade extensive vineyards have been established on terrace sediments in the lower part of the catchment

The most significant active recreational pursuit carried out on the Manuherikia River is angling. The Manuherikia River and tributaries as having high natural value particularly for brown trout fry habitat, trout spawning habitat and adult trout habitat. The Manuherikia River is a popular fishery with local and visiting anglers.

During the summer there is weekly monitoring at some sites. See the Otago Regional Council website for details.

Sites 4

Monitored sites in the Manuherikia 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.

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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