Canterbury rural area commander Inspector Peter Cooper says police are helping protesters and Central Plains Water negotiate.

Activists who occupied a locked-down construction site to protest a giant Canterbury irrigation scheme have ditched ideas of staying overnight.

Early on Wednesday morning, nearly 20 protesters from Greenpeace took over a building site near Hororata, where the second stage of the Central Plains Water (CPW) scheme is under construction.

Building work on the $200 million project began in April. When completed, the long-planned scheme would irrigate about 60,000 hectares of farmland on the Canterbury plains.

STUFF Police speak to Greenpeace protesters.

The protesters held banners reading "Stop Big Irrigation #SaveOurRivers". Several protesters hunkered down inside a pipe, while others were chained to machinery, forcing a halt to work for the day. Builders who turned up for work left.

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Activists left mid evening as temperatures dropped, but campaigner Genevieve Toop said Greenpeace had achieved what it intended.



"This is just the start here in Canterbury," she said. "We're putting big irrigation on notice. We will be back."

STUFF Police negotiators talk to the protesters.

The protest was the latest jab in the environmental group's fight against irrigation, which it says will enable more intensive farming, putting further stress on waterways.

It hinted at the protest in an open letter last year, published as a full-page ad in The Press newspaper.

"We're here to send a message that big irrigation schemes like CPW mean more cows, which means more pollution," said Toop from the protest scene.

STUFF The protesters held signs reading "Stop Big Irrigation #SaveOurRivers" and "Stop Big Irrigation #TooManyCows"

"We want to see an end to government subsidies to these big irrigation schemes."

'FALSE AND EMOTIVE'

Central Plains Water chief executive Derek Crombie said Greenpeace used "false and emotive" language and did not understand the situation.

STUFF The activists are protesting the construction of the Central Plains Water scheme, which will take water from the Rakaia River for use in dairy farming

"By taking water from the Rakaia River in a controlled way CPW is protecting the aquifers as farmers no longer have to rely on wells and artesian supplies. Ultimately this will be a great opportunity for aquifer recharge," he said.

The project was not a government subsidy, as Greenpeace mentioned, but a loan from the Crown which must be repaid with interest, Crombie said.

Police were on site to negotiate with the protesters, primarily to ensure health and safety risks were managed, said rural area commander Inspector Peter Cooper.

Toop said protesters were equipped to stay overnight.

CAMPAIGN RAMPING UP

Greenpeace ramped up its campaign against irrigation following its opposition to the planned Ruataniwha dam in Hawke's Bay.

DEAN KOZANIC/STUFF Stage one of the Central Plains Water irrigation scheme was officially opened in September last year.

That scheme was effectively scuppered after the Supreme Court ruled the Government could not swap conservation land to enable development.

There are at least eight irrigation schemes in the works nationwide, three of which are in Canterbury.

Environmental groups have particularly targeted Crown Irrigation Investments, the Government-body which would allocate $400m of public funds into the development of irrigation schemes.

SUPPLIED Greenpeace activists locked themselves inside Canterbury irrigation pipes on Wednesday morning.

Its purpose was to be an early-in, early-out investor to get schemes off the ground.

More than 90,000 people signed a Greenpeace petition to stop Government contributions to the fund.

The scheme's supporters argue it comes with significant economic benefits for the region, including up to $1b for the regional economy and hundreds of direct and indirect jobs.

SUPPLIED The protest comes off the back of a similar campaign in Hawke's Bay.

It would give certainty to farmers in areas prone to drought, and relieve the region's stressed aquifers by replacing groundwater extraction with surface water.

Its environmental credentials have been questioned by freshwater and health experts, however.

The scheme would substantially increase the nutrient load entering the polluted Lake Ellesmere, according to ECan figures.

A health impact assessment led by Canterbury medical officer of health Dr Alistair Humphrey pointed to a likely increase in nitrates in groundwater, and concluded the health effects would likely outweigh the financial benefits.

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