Prime Minister John Key says the government is not ready to intervene to reduce nitrogen levels set for rivers affected by the Ruataniwha Water Storage Scheme, preferring to let the issue go to court first.
He was speaking at his post-Cabinet press conference following the release of a map produced by the state water and atmospheric science agency NIWA showing the ruling by the Board of Inquiry on the Hawke's Bay irrigation scheme on nitrogen levels in the Tukituki River could "devastate farming" if applied across New Zealand.
"All waterways in highly productive fertile plains of the country exceeded the limit," said Irrigation New Zealand chief executive Andrew Curtis, who published a map that the lobby group says shows where the requirement for dissolved inorganic nitrogen levels in fresh waterways not to exceed 0.8 milligrams per litre would have an impact.
The map shows large swathes of existing Waikato, Taranaki, Canterbury, Otago and Southland dairying country are operating above that threshold at present.
The BOI was appointed by the Environmental Protection Authority to rule on the $265 million irrigation project, which was to have been supported by Trustpower, Ngai Tahu, the Crown Irrigation Fund that subsidises privately backed irrigation schemes, and local farmers and other agricultural producers who would use the stored water.
Irrigation NZ argues that at 0.8mg/l, the board has proposed a standard below a level normally regarded as indicating human influence that requires mitigation.
"European numbers are more like 2.5mg/l to 5mg/l and beyond," he said. While 0.8mg/l might be achievable over time, "the technology just hasn't been invented yet".
The board has until June 28 to issue its final decision, after which court challenges may be forthcoming.
"We’re in a delicate time because the BOI has made their decision," said Key. "Whether that means the dam is actually viable or not will depend on where this now goes.
"The reason I’m reluctant to make too many comments is I think it’s highly likely it will be challenged in the court."
Asked whether the government would intervene, Key replied: "We wouldn’t want to at this point. We would rather let it run its process before wading in to offer a point of view there.
"The current setting is going to be far less attractive than it was for some of the equity partners and quite challenging to get up to that standard."
Curtis said the proposed limit would have impacts not just on farmers in the Ruantaniwha catchment area, but potentially throughout the rural community.
"New Zealand has to decide what it wants," Curtis said.
The government has had no request for intervention from the dam's main backer, the Hawkes Bay Regional Council's investment company.