Scientists are considering the feasibility of boring a tunnel through the Southern Alps to take West Coast water to farms on the Canterbury plains.
"One of the projects that we have mooted is drilling a hole through the Southern Alps, so that we can irrigate the Canterbury plains," GNS Science chairman Con Anastasiou, a Wellington lawyer, told parliamentarians today.
Asked about the proposal after the state science company's presentation to Parliament's science select committee, Mr Anastasiou said: "It's a germ in somebody's mind.
"I can't say anything more than that at this stage."
Green Party MP Catherine Delahunty asked him whether such a project, even if it was technically feasible, would raise questions about Maori views on the transfer of water from one catchment to another.
Mr Anastasiou responded that if tangata whenua did not like the idea, it could be dropped.
And he told NZPA the proposal for a tunnel was potentially delicate, because it was important for GNS Science to talk to South Island iwi.
"One of the real concerns they have is in the mixing of waters, from one river to another, but there is no point in starting a dialogue until we - from a science point of view - believe that it is feasible.
"We know we are going to be challenged, but if we conclude from the science point of view that it can be done, we will go and talk to all of the iwi."
It would be important for GNS Science to start its consultations at the right time, to show respect, present the potential project in the right light, and to outline the opportunities.
Mr Anastasiou agreed one of biggest potential beneficiaries from an extensive new water supply for Canterbury would be the Ngai Tahu iwi, a major stakeholder in the regional economy.
The area of land being irrigated in New Zealand has doubled every decade since the 1960s and irrigation takes up 77 percent of all allocated water.
In Canterbury, which has 70 percent of the irrigated land in New Zealand, there has been increasing competition for water, with supplies over-allocated in some districts.
GNS Science chief executive Dr Alex Malahoff, a Hawaiian university academic, told NZPA that a Hawaiian king used Chinese labourers to dig tunnels by hand through mountains on Oahu in the early 1800s to divert water to areas where it was needed.
In New Zealand, opening of the 8.5km Otira railway tunnel carved out of wet shale and rotten rock beneath the Southern Alps in 1923 marked one of the nation's greatest engineering feats.
The Otira tunnel provides a river-to-river connection, but Canterbury's inland plains are well above sea level, and the tunnel slopes steeply down from east to west at a gradient of 1:33. A tunnel for a gravity-fed waterflow would need to slope the other way.
Water could be pumped sustainably with power from wind turbines, or a West Coast hydro scheme, and on the eastern side of the Alps, gravity-fed to irrigation networks.
Big tunnels to carry water are not new to NZ - Fletcher Challenge bored a $260 million second Manapouri tailgate tunnel over 10km, completing the 33-month job in 2001.
And in Peru, the 20km Olmos tunnel is being bored through fractured rock and across 400 faultlines in the Andes so that up to 2 billion cubic metres of water from the mountains can be used to irrigate the dry Pacific coast.
