Aquifer recharge ‘feasible’

Despite incomplete trial

Despite incomplete trial

A TRIAL to inject water into the Makauri aquifer has been deemed “feasible”, despite less than two-thirds of the target injection total achieved. A report to the council’s environmental planning and regulations committee last week told councillors while the trial was incomplete, there was enough data to show a long-term recharge of the aquifer was feasible.

On July 24, a trial began to pump 100,000 cubic metres of filtered water from the Waipaoa River through a bore on Kaiaponi Farms. On September 13 the trial was halted due to an electrical fault in one of the pumps. The trial was scheduled to end on September 30 but due to the time needed to repair the pump, staff decided to end the trial — with 64,000 cubic metres of water having been injected. The trial also had to be suspended twice for a total of seven days because turbidity in the Waipaoa River was too high.

“Although the trial finished early, enough data was obtained to determine that the MAR is a feasible option to replenish the Makauri aquifer,” the council report said.

The managed aquifer recharge (MAR) trial was carried out to determine if water levels in the aquifer could be increased. The council report says aquifer levels are in decline, and any reductions in water takes will have a “considerable impact on the local economy”. The aquifer is used for irrigating crops, and is worth an estimated $20 million annually to local industry.

The trial highlighted areas where more research was needed before a full-scale aquifer replenishment scheme could be consented and implemented. More research was needed on how much water needed to be injected, the optimal injection rate and the optimal locations for future injection bores. There also needed to be further investigation into the effects of the aquifer recharge on springs and septic tanks, and on water quality.

Funding the first trial

An initial test in June injected 8811 cubic metres into the aquifer. It showed no unexpected effects and after consultation with the MAR Community Liaison Group, staff decided to proceed with the full trial. The majority of the stage one trial was funded with grants of $365,000 from the Ministry of Primary Industries and $200,000 from Eastland Community Trust.

The council’s contribution was higher than expected and by trial completion was estimated to be about $150,000, on top of the staff time and costs of the resource consenting process, which were provided for in the 2015-2025 long-term plan.

Over the next three months council staff will be conducting post-trial monitoring, with a post-trial report detailing the results and recommendations scheduled to be released in January.

Planning for stage two trial

Planning has started for the stage two trial, scheduled to take place in 2018, including for funding and resource consent applications.

Councillor Meredith Akuhata-Brown asked council staff if there were other plans for storing water.

“This winter has been quite wet . . . when we talk about drought concerns, should we not be considering collecting more?”

Environmental and science manager Lois Easton said they were looking at further water storage options.

“The Makauri aquifer only covers part of the Poverty Bay Flats,” she said. “Any solution around that is not going to address all of our long-term water needs. We have planned, this year, more investigation into water storage options, and other natural infiltration methods for shallower aquifers.”

A TRIAL to inject water into the Makauri aquifer has been deemed “feasible”, despite less than two-thirds of the target injection total achieved. A report to the council’s environmental planning and regulations committee last week told councillors while the trial was incomplete, there was enough data to show a long-term recharge of the aquifer was feasible.

On July 24, a trial began to pump 100,000 cubic metres of filtered water from the Waipaoa River through a bore on Kaiaponi Farms. On September 13 the trial was halted due to an electrical fault in one of the pumps. The trial was scheduled to end on September 30 but due to the time needed to repair the pump, staff decided to end the trial — with 64,000 cubic metres of water having been injected. The trial also had to be suspended twice for a total of seven days because turbidity in the Waipaoa River was too high.

“Although the trial finished early, enough data was obtained to determine that the MAR is a feasible option to replenish the Makauri aquifer,” the council report said.

The managed aquifer recharge (MAR) trial was carried out to determine if water levels in the aquifer could be increased. The council report says aquifer levels are in decline, and any reductions in water takes will have a “considerable impact on the local economy”. The aquifer is used for irrigating crops, and is worth an estimated $20 million annually to local industry.

The trial highlighted areas where more research was needed before a full-scale aquifer replenishment scheme could be consented and implemented. More research was needed on how much water needed to be injected, the optimal injection rate and the optimal locations for future injection bores. There also needed to be further investigation into the effects of the aquifer recharge on springs and septic tanks, and on water quality.

Funding the first trial

An initial test in June injected 8811 cubic metres into the aquifer. It showed no unexpected effects and after consultation with the MAR Community Liaison Group, staff decided to proceed with the full trial. The majority of the stage one trial was funded with grants of $365,000 from the Ministry of Primary Industries and $200,000 from Eastland Community Trust.

The council’s contribution was higher than expected and by trial completion was estimated to be about $150,000, on top of the staff time and costs of the resource consenting process, which were provided for in the 2015-2025 long-term plan.

Over the next three months council staff will be conducting post-trial monitoring, with a post-trial report detailing the results and recommendations scheduled to be released in January.

Planning for stage two trial

Planning has started for the stage two trial, scheduled to take place in 2018, including for funding and resource consent applications.

Councillor Meredith Akuhata-Brown asked council staff if there were other plans for storing water.

“This winter has been quite wet . . . when we talk about drought concerns, should we not be considering collecting more?”

Environmental and science manager Lois Easton said they were looking at further water storage options.

“The Makauri aquifer only covers part of the Poverty Bay Flats,” she said. “Any solution around that is not going to address all of our long-term water needs. We have planned, this year, more investigation into water storage options, and other natural infiltration methods for shallower aquifers.”

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