The ability of aquifers in North Otago to support more irrigation was the hot topic at an Oamaru meeting called by the Otago Regional Council to discuss changes to the way water is managed in the province.
About 30 people were at the meeting on Tuesday night to discuss a proposed plan change by the council to its "Regional Plan: Water" and outline the process which will be followed.
Most were farmers, who were concerned to ensure aquifers were not over-allocated, affecting their supply of water for irrigation and farm use.
Moeraki constituency councillor Doug Brown said Otago was a dry area and that resource had to be used carefully.
While the focus at present in North Otago is on the Waitaki River, that is controlled by the northern regional council, Environment Canterbury (ECan).
ECan is processing about 150 resource consents to use water in the Waitaki catchment.
The Otago council at Tuesday night's meeting outlined changes it proposed to its regional water plan, which will be publicly notified later this year for submissions, which will close in mid-March.
Groundwater scientist Jens Rekker said there was a finite amount of groundwater which could be allocated before aquifers became depleted.
Maximum allocation volumes would be set for aquifers, and the North Otago volcanic aquifer, which stretches from Deborah through Totara and inland to Robbs Crossing would be the first.
The volcanic aquifer combined the Deborah and Waiareka aquifers which, research had shown, could be treated as one.
Mr Rekker said that three million to four million cubic metres of water a year was used from the aquifer, considerably below the seven million cubic metres a year which it was estimated could be allocated.
In addition, research had shown some consent holders were only using about 20% of the amount they had been allocated.
The council hoped that when consents were reviewed or renewed, annual volumes would be adjusted to better reflect use.
But some farmers questioned whether the figure of what was available in the volcanic aquifer was correct.
Farmers in the Deborah aquifer over past seasons had restrictions on their use and did not agree that twice as much as what was allocated now could be available.
Mr Rekker acknowledged some areas using the aquifer did face restrictions, but said other consents could be granted outside those areas without affecting existing takes.
"It seems unjust to restrict other areas when they won't affect the Deborah aquifer," he said.
Cr Brown said there would be separate consultation over the volcanic aquifer and the community would have a say on how it should be used.
