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Wellington Region

Surface Water Zone: Ruamahanga

The Ruamahanga Water Management Zone lies in the central Wairarapa and is defined by the boundary of the Ruamahanga River catchment. With an area of 3,555 square kilometres, it occupies almost half (44 percent) of the total regional land area. The zone encompasses the townships of Featherston, Carterton, Martinborough, Greytown and Masterton, as well as the Wairarapa Valley, where the bulk of the region's intensive farming and horticulture takes place.

The Ruamahanga Surface Water Zone contains several significant tributary catchments of the Ruamahanga River, including the Waipoua, Waingawa, Mangatarere and Waiohine rivers that rise in the Tararua Range and the Tauweru and Huangarua rivers that originate in the eastern hill country. These rivers join the main stem of the Ruamahanga River as it traverses the Wairarapa Valley floor before discharging to the Cook Strait on the south coast. The rivers and streams rising in the Tararua Range tend to have relatively high base flows and frequent freshes whereas rivers coming out the eastern hill country typically have extended periods of very low flow.

Lake Wairarapa and its catchment (including the Tauherenikau River) is also a major part of the Ruamahanga Surface Water Zone.  Flow from the lake to the lower Ruamahanga River is controlled via a Barrage gate in the outlet channel.  Spring-fed streams (such as the Papawai,Otukura and Parkvale) are also a prominent feature of the Wairarapa Valley floor.

Beneath the Wairarapa Valley floor is the most significant and heavily used groundwater resource in the region. The permeable nature of the gravel and sand aquifers near the rivers means that there is a significant amount of exchange between surface and groundwaters in this zone . In addition to water being abstracted directly from rivers, pumping from groundwater bores is also known to further deplete river flow.

Consents to abstract water from rivers and streams in the Ruamahanga Surface Water Zone make up about 83 percent of the total number in the Wellington region and about 68 percent of the region’s abstraction by volume. Unlike the Kāpiti Coast and Hutt Valley areas where most of the water is taken for municipal supply, the large bulk of water taken in the Ruamahanga Zone is used for irrigation. This means that consented water use is highly distributed and the potential for catchment water stress related to cumulative effects is relatively high. 

Management of water resources in the Ruamahanga Surface Water Zone is focussed on treating surface and groundwater as a single, connected system.  While the zone is split into three sub-zones (Upper, Middle and Lower Ruamahanga River) and several tributary river units to help manage low flows and allocation limits, the linkage between these zones is considered at the whole catchment scale. 

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.

    Total run-off to sea has been estimated by aggregating mean flow statistics from the River Environment Classification (developed by the National Institute of Water and Atmospheric Research). 

  • 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.

    Values for water availability have not yet been provided. Greater Wellington Regional Council is in the process (as at June 2015) of notifying a new Regional Plan that will contain proposed allocation limits.  When this Plan is notified the proposed limits will be used to update the empty fields.

  • 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


Monitored sites in this Zone

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