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Mahinga

Managed Aquifer Recharge

The aim of this project is to inject water from the Waipaoa River into the Makauri aquifer to ensure its ongoing use for irrigation of 3,000 hectares of horticultural farmland.

The Makauri aquifer is the largest underneath the Poverty Bay Flats, extending from Kaiteratahi down to Makaraka and spanning both sides of the Waipaoa River.

Recharge of the Makauri aquifer could reverse the declining levels of the aquifer, address saline intrusion, and provide water surety for irrigation, cultural and environmental needs.

The Stage 1 trial began in 2017, jointly funded by Council, Provincial Growth Fund and Trust Tairāwhiti (previously known as Eastland Community Trust).

The results of the first trial showed positive indications of increasing groundwater levels without degrading the quality of water.

Resource consent for Stage 2 trial was granted in August 2018.

The purpose was to further investigate the potential risks associated with injecting larger amounts of water the aquifer.

As part of the resource consent and Trust Tairāwhiti funding conditions, Council engaged with Rongowhakaata Iwi Trust to develop a Cultural Impact Assessment (CIA).

A Mauri Compass Assessment was also undertaken with Te Aitanga-a-Mahaki. Completion of the CIA allowed Council to start the Stage 2 injection trial in August 2019.

A third injection trial was carried out in the winter of 2020. The volumes and quality of water injected into the aquifer during are summarised in the table below:

 

2017

2019

2020

Days available

N/A#

69

146

Number of injection days

N/A#

33

80

Average Injection Rate

  1. l/s
  2. l/s
  3. l/s
  

Average Turbidity

  1. NTU
  2. NTU
  3. NTU
  

Total Volume Injected

73,180 m3

39,174 m3

104,557 m3

#Data not available

At the end of the 2020 trial an independent review of all data was completed in February 2021. This report confirmed that the Makauri aquifer is suitable for recharge of around 600,000m3 per annum. Careful consideration will need to be applied to the construction of any future bores in the multiple aquifer system of the Poverty Bay Flats.

The scientific trial of the project is now complete. Information gained during the trial has been circulated to stakeholders and will be made available here on our website.

Council will continue to engage with stakeholders and iwi to investigate options to improve the availability of water for irrigation and commercial uses, including considering the learnings from the MAR trial.

Funding

The Provincial Growth Fund granted $542k towards the project, and Trust Tairāwhiti a further $488k.
Combined with $160k Council-committed funds in the 2018-2028 Long Term Plan, stage 2 of the trial was fully funded.
As the trial is complete there's no new budget allocation in the 2021-2031 Long Term Plan.

More information about the project