More groundwater available, study shows

"Substantially" more water could be available for irrigation in the Tarras-Bendigo area than first thought, an Otago Regional Council study shows.

The year-long Bendigo-Tarras groundwater allocation study aimed to establish a possible annual allocation limit for groundwater takes in the area, which has a very dry climate and increasing demands for irrigation water.

Environmental information and science director John Threlfall said the study found that while the groundwater closest to the Tarras community was fully allocated, a lot more was available away from the township, closer to the Clutha River, than had been thought.

"We think there is quite a big amount of water available. It's substantial, enough for irrigation."

Apart from the narrow band of water close to the Lindis River (which was closed to further groundwater takes), two other areas west of the community - the lower Tarras allocation zone and the Bendigo allocation zone - had the potential to allow for more irrigation because they were close to the Clutha River and the groundwater was replenished by drawing on the river.

As a result of the study, staff had proposed limits for groundwater abstraction in the two areas.

These would go out for public consultation.

Consented allocation was now only 12% of the level suggested for the lower Tarras area and 13% for the Bendigo area.

With help from Glass Earth geophysical data, the council staff modelled how the groundwater system would respond to increased takes to gain a better understanding of what was going on underground, Dr Threlfall said.

"It's closer to reality. Before, we would have had to make more assumptions."

Because of that, the council had "erred on the cautious side" when setting allocation limits.

This study had shown it did not have to be so strict, the exception being with the ribbon next to the Lindis itself, he said.

The council had also completed a water resources study for the Cardrona River and a groundwater allocation study for the Wanaka-Cardrona aquifer.

Staff had suggested integrated management of the two would be the best way to maintain the continuity of flow in the river and optimise river recharge to the aquifer.

- rebecca.fox@odt.co.nz