Update on Managed Aquifer Recharge trial in Makauri

Council is taking a cautious approach on the complex and significant trial of Managed Aquifer Recharge (MAR) in the Makauri aquifer.

The project was debated at length in today’s meeting, before Council received a report outlining the status of the trial and confirmed Council’s future role in relation to any MAR scheme will be regulatory.

The success of the first stage of the trial has proven the feasibility of MAR in the Makauri aquifer and work is underway to progress stage two, subject to funding confirmation and resource consent approval.

During the debate Mayor Meng Foon reiterated the significance of the project, as it ultimately relates to the management of a key water resource in the region. Councillors and staff agreed there was still much more work to do to determine the best way to proceed once the trial is complete.

The trial began in 2017, jointly funded by Gisborne District Council, Ministry for Primary Industries and Eastland Community Trust. During the trial 75,000m3 of water was successfully injected into the aquifer.

The MAR project aims to inject water from the Waipaoa River into the aquifer in order to ensure its ongoing use for irrigation of 3000 hectares of horticultural farmland. Once complete, the trial will show if it is possible to increase water in the aquifer with minimal impact on water quality and the environment.

Golders International Consultants have produced a report on stage one of the trial and did not identify any adverse environmental effects.

The second stage of the trial aims to resolve issues highlighted in the first stage and provide information to develop a full recharge scheme. Two new monitoring bores would be drilled to improve the quality of data. The Provincial Growth fund has granted $542,000 in funding for stage two but further funding is still required.

A consent has been lodged with the Bay of Plenty Regional council for council to vary the existing conditions, most notably to take more water during winter from Waipaoa River to inject into the aquifer – up to 365,000m3 per year for the next two years.

Environmental and Science manager Lois Easton says there is a clear distinction between the trial in the Makauri aquifer and any future development of a MAR scheme.

“Council has only committed to the trial to see if a managed recharge will work to increase water in the aquifer with minimal impact on water quality and the environment.

“The information we gain during the trial will be available to any party seeking to develop a MAR scheme, but otherwise council’s role will be regulatory, monitoring any scheme private entities may wish to put in place.”

A company – MAR Limited – has been set up by horticultural interests, including Mangatu Blocks, Kaiaponi Farms, Leaderbrand and some smaller firms. This group is planning how they can use the findings of the trial for future development.

What is the aquifer and why is it declining?

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.

The aquifer is an area of gravel and sand under the flats that is saturated with water. It naturally recharges by water percolating from the river and higher aquifers, a slow process that happens over several decades.

Since the horticultural boom in 1980s, irrigation of crops has remained at a constant level leading to the decline of the aquifer.

It has very little natural recharge from rainwater and river water because of changes to the land such as flood control, vegetation clearance, rainfall and climate changes.

The Poverty Bay Flats is an area of 18,000 hectares and is the single largest area of highly fertile soil in the country. It is among the most productive horticultural areas thanks to a combination of high sunshine, fertile soils and mild temperatures.

The aquifer supplies nearly a third (approximately 1 million cubic metres) of all irrigation water for use on 3000 hectares of irrigated horticultural farmland on the Flats.

Modelling shows that 660,000m3 per year is required to go back in to stabilise the aquifer, with even more required on top of that to enable any expansion of irrigation.

Irrigation would need to be reduced by two thirds of current use to equal natural recharge.

The MAR project aims to identify the feasibility of increasing water held in the aquifer by injecting water from the Waipaoa River.

ENDS

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