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Manawatu-Wanganui region

Groundwater Zone: Whangaehu Groundwater MZ

The Whangaehu GMZ extends from Mount Ruapehu via the Whangaehu River to the coast, covering an area of approximately 1,982 square km.  The Whangaehu GMZ is geologically diverse, extending from the volcanic plains in the north-east, through hill country along the Whangaehu Valley to the coastal dunes near the mouth of the Whangaehu River. 


Little is known of the groundwater resources in this part of the region, because of the relatively small number of groundwater bores located in the Whangaehu GMZ. A bore is a hole that allows the extraction of water from an underground layer of water-bearing material (gravel, sand or other favourable rock type). Information collected during the installation of groundwater bores, such as a record of the geology, provides insight into the availability of groundwater throughout the region.

On the southern flanks of Mount Ruapehu, shallow groundwater only accounts for 0.7% of currently consented groundwater in the Whangaehu GMZ.  The water is mainly allocated for irrigation and industrial use, with the remaining bores providing stock water and domestic supply.  Although little is known about groundwater resources in this part of the region at the present time, there is thought to be potential for further development.

Groundwater bores located along the banks of the Whangaehu River draw small volumes from water stored in gravels below the river terraces.  Because these gravels are connected to the river itself, many of these takes are considered to be riparian, meaning they draw a significant portion of their flow from the Whangaehu River.  This is an important aspect of how Horizons allocates water and reflects the important connection between groundwater levels and surface water flow.

Groundwater use increases towards the coast, where water is drawn from deeper sand and gravel layers, which are capable of producing larger volumes of water for irrigation and stock water use.  Groundwater in the coastal area of the Whangaehu GMZ accounts for 63% of the total annual volume of water currently consented in this management zone.

Throughout the Whangaehu GMZ, approximately 392 million cubic meters of water is recharged, or estimated to make its way into the groundwater system, within an average year.  Of this volume, 122 million cubic meters (31%) is available for use.  This means that of all Horizons groundwater management zones, the Whangaehu GMZ has the highest proportion of estimated annual recharge assigned for allocation.  At present however, a very small proportion (0.43%) of the available groundwater allocation volume is consented for annual use, of which 51% is utilised for agriculture and horticulture, 42% for water supply and 7% for industrial use.

Water Use
Groundwater in this zone

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


Groundwater available: {{waterSource.availableToAllocate}} Irrigation
Town supply
  • Groundwater in this zone
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    Groundwater in this zone

    Accurately estimating the total amount of water available in a groundwater management zone is not currently possible. Regional Councils are working with the Ministry for the Environment on the best way to calculate this figure. We will include these figures on LAWA when they become available. In the meantime, for more information about a particular groundwater management zone, contact your regional council.

    Total allocation is calculated as Daily Max Volume over 100 days for irrigation takes and Max Daily Volume over 365 days for all other uses. Estimated Annual Allocated Volume (EAAV) is calculated to determine a conservative maximum usage that may occur in a dry year and assumes that (1) for consents authorising abstraction during the irrigation season the EAAV can be calculated by assuming that, on average over a year, water is used for 100 days at 80% of the maximum consented daily abstraction rate; and (2) for consents for full year abstractions, the EAAV can be calculated by assuming that, over a year, water is used for 365 days a year at 50% of the maximum volume.

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

    Groundwater available to consent

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    Consented water in this groundwater 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 groundwater 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.

  • Water consents: How is consented water used?

    Consents by use in this groundwater zone

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    Consented water in this zone

    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

    Allocation for existing hydroelectricity generation is excluded because, while it is still part of the overall allocation framework, it sits outside of the core allocation limits (i.e. the core allocation limits were set after the existing hydroelectricity take volumes).


Monitored sites in this Zone

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