Stage 2 of MAR trial underway
The second stage of Council’s Managed Aquifer Recharge commenced this week, aiming to inject up to 365,000m3 from the Waipaoa River into the Makauri aquifer.
Once complete, the trial will determine if it is possible to increase water in the aquifer with minimal impact on water quality and the environment.
During the injection phase, water will be pumped from below the Waipaoa riverbed through existing irrigation pipes to the MAR headworks, approximately 570m from the river.
The water goes through a bank of filters before being fed into an injection pipe that transfers water to the aquifer, around 75m beneath ground level.
Monitoring bores in the aquifer will measure water levels, temperature, conductivity and a range of other water quality parameters as well as some emerging contaminants to determine ground water quality and impacts. Improvements have been made to the MAR headworks to better measure turbidity, or cleanliness of the injected water.
The injection trial will continue until horticultural irrigation is required in spring, and recommence from Autumn 2020.
A mauri compass assessment was undertaken as part of the cultural framework agreed with Te Aitanga a Mahaki. This has developed a mauri monitoring plan to assess cultural effects of the trial.
Rongowhakaata Iwi trust has provided a cultural impact assessment in the context of the aquifer and Waipaoa River, taking into account Rongowhakaata’s association with these water bodies and potential impacts the trial may have on cultural values.
Project manager Dr Graeme Card says once the trial has concluded, the findings will help determine next steps and future use of the aquifer.
“The aquifer supplies nearly a third of water for use on 3000 hectares of irrigated horticultural farmland on the Poverty Bay Flats. Council recognized its importance by undertaking the trial which will give us valuable information to help inform the future management of Tairāwhiti’s precious water resources on the flats.”
The Provincial Growth Fund has invested $542,000 towards it and the Eastland Community Trust has contributed $448,500.
For more information, visit our MAR project page.
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.
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.
Since the horticultural boom in 1980s, irrigation of crops has remained at a constant level leading to the decline of the aquifer.
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.
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.