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Marlborough region

Surface Water Zone: Wairau River

The Wairau is Marlborough’s largest river with a catchment of 3430 km2 – about one third of the district’s land area. It rises in the Spenser Mountains, more than 2000 metres high and inland from St Arnaud, and flows for about 150 km down to Cloudy Bay on the edge of Cook Strait. The Wairau is a braided gravel river for much of its length. The mountainous upper part of the catchment has no surface water or groundwater takes and is generally in a highly natural state. 

There are hydroelectric power schemes on two of the Wairau’s tributaries. The Branch power scheme  discharges into the Wairau about 7km downstream from the Branch confluence, causing significant variations in the flow of the Wairau (up to 20% either side of daily mean flow). The second power station is on the Waihopai River, a catchment known for its short intense rainfall and often turbid waters.

Most water takes from the Wairau are between the Branch confluence and SH6 and in the lower reaches of the Waihopai sub-catchment. There are major losses to groundwater in the reach between the Waihopai confluence down to Wratts Road, on average about 7-8 m3/s. As a consequence flows can be very low at Barnetts Bank, SH1,  in dry seasons. Less than 2 m3/s has been recorded at the lower end of this reach. Below SH1 the river divides into two: the tidal, meandering main channel that discharges at the Wairau Bar; and the more direct Wairau Diversion, built in 1963 to reduce flood levels. The main sections of the Wairau River are discussed in more detail below.

Upper Wairau River

The mountainous Upper Wairau catchment upstream of the Wash Bridge is important to the flow of the river due to its geology, high rainfall and winter snow cover.

North Bank catchments

The North Bank of the Wairau is dominated by high rainfall in the Richmond Range and a number of short, steep rivers that contribute significantly to flood events. The major North Bank catchments are the Goulter River, Top Valley Stream, Timms Creek, Pine Valley Stream, Bartletts Creek, Onamalutu River, Are Are Creek and the Waikakaho River. Of these Are Are Creek is the odd one out with its low gradient waterway compared to the mountainous backdrop of the other North Bank streams.

Branch River

The Branch River is the largest tributary of the Wairau River.  It flows generally northwards from high peaks of about 2200 metres to its confluence with the Wairau River.

The Branch River has a catchment area of about 560 km2, and is about 37 km long. It has two similar sized sub-catchments: the main Branch River and the Leatham River.

South Bank catchments

A number of smaller tributaries enter the Wairau River from the southen side between the Branch and Waihopai Rivers.  These waterways are generally ephemeral in their middle reaches when they leave the south bank hill country until they gain some spring flows near where they join the Wairau.

Waihopai River

The Waihopai River is a major tributary of the Wairau with a catchment area of about 800 km2. Its upper reaches extend back to the Acheron Saddle surrounded by peaks of more than 2000 metres.  From there it flows generally north-east for about 60 km, eventually joining the Wairau River just west of Renwick.

Rainfall in the Waihopai catchment varies from about 800mm a year in the lower catchment to more than 1800mm in the headwaters.  The range of flows also fluctuates from less than 1 m3/s to more than 1000 m3/s. 


Water Use
Surface Water in this Zone

Regional councils collect information about how much water is available and manage resource consents for those wishing to take water from rivers and streams. Use the buttons below to view information on: how much water is available, where it comes from and how its used.


Rainfall {{waterAvailable.rainfall}} Runoff to sea {{waterAvailable.runoff}} Surface Water available: {{waterSource.availableToAllocate}} Irrigation
Town supply
  • How much surface water is there in this zone?

    Rainfall and flow in this surface water zone

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    Rainfall and runoff

    Relative breakdown Source Volume
    Rainfall total:
    {{waterAvailable.rainfall }}
    rainfall Rainfall Total {{waterAvailable.rainfall}}
    Runoff total:
    {{waterAvailable.runoff }}
    runoff Runoff to sea {{waterAvailable.runoff}}

    The table above shows the average amount of rainfall the water management zone receives each year and how much of that flows out to sea. These are approximate figures only.

  • Water consents: How much water is consented and used?

    Surface water available to consent

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    Consented water in this surface water zone

    Use the tables below to look at how much water is available compared with how much is actually consented within this water management zone. Click the plus to expand subzones where available

    Comparing consents and use
    Amount available to consent In this surface water management zone:
    {{}} {{}}
    available to consent
    Amount consented
    measured and non measured
    Amount used (measured)
    Amount Units Consented or used as a percentage of available
    Total available to consent {{}} {{}} {{}}
    Total consented {{}} {{}} {{}} {{}}
    Total consented and measured {{}} {{}} {{}} {{}}
    Total measured amount used {{}} {{}} {{}}
    Total measured volume used {{}} {{}}

    The table above shows the amount of water that is available for use compared to the amount that has been consented. The ‘Total Consented’ and ‘Total Consented and Measured’ fields are based on percentages of the ‘Total available to Consent’ field. If this field is not populated no data will be displayed. Some consents require actual use to be monitored and this is presented as 'Total measured volume Used' where available.

    The Wairau-Awatere Resource Management plan includes a three class allocation system for some major rivers including the Wairau and Waihopai Under this system up to two-thirds of all flows above the specified sustainable flow can be allocated, the bulk of this being in the open ended class C, which is intended for takes to storage. Under the NES for freshwater management this open ended class will have to be capped at a suitable limit when the plan is reviewed in late 2015.

  • Water consents: How is consented water used?

    Consents by use in this surface water zone

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    Consented water

    Overall annual volume for {{waterAvailable.year}}
    Relative breakdown
    Activity Percentage of total consented Total volume Number of consents
    {{item.displayText}} {{item.displayText}} - - No data available {{item.breakdownPercentage}}% {{item.totalVolume}} m3 {{item.numberOfConsents}}
    Total {{}}% {{}} m3 {{}}

    The above table shows the proportion of water consented for irrigation, industrial, stock, town supply and other. It excludes hydro electricity. In this region/management zone {{hydroUsage.totalVolume}} m3/year is consented for hydro-electricity and makes up {{hydroUsage.percentageConsented}}% of the total water volume consented for this region/management zone

    It excludes stock water as the taking of stock water in Marlborough is a permitted activity and a resource consent is not required or issued for this activity.

    The town supply activity total includes council operated schemes in both urban and rural settings as well as private communal rural schemes.


Monitored sites in this Zone

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