A premises in the Ashburton Business Estate, where the Ashburton District Council is in the process of allowing a bottled water company to extract 40 billion litres of water.

A council in the drought-prone Canterbury plains is selling the right to extract 40 billion litres of pure, artesian water to a bottled water supplier.

The Ashburton District Council is selling a section in its business estate, known as Lot 9, for an undisclosed sum. It comes with a valuable resource consent that allows abstraction of water from aquifers beneath the town.

The council has refused to publicise information about the deal, which is understood to be with an overseas company.

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It has outraged some residents, who say water is desperately needed locally.

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The area's artesian water is increasingly popular in overseas markets such as China, with its New Zealand origin often featuring in branding and marketing.

The consent allows the holder to take 45 litres of water a second from local aquifers, totalling more than 1.4 billion litres a year.

It expires in 2046, meaning the buyer will gain access to more than 40 billion litres of Ashburton's pure water.

It was approved in 2011 by Environment Canterbury and includes a recharge consent, meaning all water taken must be replaced from other sources.

In a statement, the council confirmed it was in the process of selling the site.

"The parcel of land includes an existing consent for water abstraction from local aquifers," it said.

"The prospective buyer is interested in setting up a water-bottling plant."

Council chief executive Andrew Dalziel would not answer questions about the sale, citing commercial sensitivity. Standing orders prevented councillors from discussing the sale, which is expected to be finalised in June.

It is understood there has been no consultation with ratepayers or other interested parties, such as iwi, about the deal.

Sir Mark Solomon, chairman of Te Runanga o Ngai Tahu, said it was "disappointing" the iwi had not been informed.

"Twenty years ago the Ashburton region had reasonably good water quality, but it is now an over-allocated catchment and faces some of the most pressing water quality challenges in our takiwa [tribal region]," he said.

"It seems incredible that the council wouldn't think more broadly about the future of its existing consents."

Ashburton resident Jen Branje is leading community opposition, and said the lack of transparency raised alarm bells.

"We live in a drought-prone area – farmers aren't given consent to bore for water for their crop-growing, so why on Earth are we selling it off-shore?"

The Ashburton groundwater zone is over-allocated, meaning water allocated to consent holders exceeds the amount available for use.

New groundwater consents are difficult to acquire, making existing consents more valuable.

Branje said a lack of consultation did not give locals faith the sale was in their best interest.

"This whole thing has gone on behind the ratepayers' backs. No-one has any clue about it whatsoever.

"It's a blimmin' lot of water, and it shouldn't be allowed to go off-shore. If anything, that water should be sustaining our own economic backbone."

Ashburton often has issues supplying water during the summer. In some areas, water restrictions banned residents from using hoses to water their gardens.

When applying for the consent, the council came to an arrangement with meat processor Silver Fern Farms, allowing it to deepen its bore if Lot 9's water abstraction caused groundwater levels to reduce.

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