A new study shows that using water from Lake Tekapo to irrigate South Canterbury land would not be economically viable.
Environment Canterbury has released a report on transferring water from Lake Tekapo via Burkes Pass to South Canterbury, for irrigation and environmental uses.
The report factored in hydro-electric power generation that could be lost from the existing Waitaki scheme, possible generation capacity from a new water transfer, and the economic benefits from a boost to South Canterbury irrigation.
Two Tekapo transfer concepts were outlined: a 2 cumec year-round transfer, supporting 11,550ha of irrigated land; and a 10 cumec seasonal transfer, providing for 25,000ha of irrigated land.
Analysis showed neither would produce a net economic benefit or be affordable for any likely land use, based on the various assumptions made.
On a dairy farm, the first concept would need capital input of $64,228 per hectare and result in an estimated loss of $2430 per hectare.
Construction costs were estimated between $264 million and $382 million (equivalent to $22,918 to $33,103 per hectare).
The second concept, also on a dairy farm, would need capital input of $59,530 per hectare and result in an estimated loss of $1857 per hectare.
Construction costs were estimated between $478 million and $691 million (equivalent to $19,152 to $27,664 per hectare).
''While the report shows neither of the Tekapo transfer concepts appear to be economically viable, it provides a comprehensive suite of information useful as a resource to inform further work and ongoing discussions at the Canterbury Water Management Strategy committees,'' ECan commissioner David Caygill said.
The report was part of a wider consideration of water options under the Canterbury Water Management Strategy.
It incorporated more than a century of previous work on the prospect of taking water from the lake to South Canterbury farmland.
Ways of avoiding mixing the alpine water with the rivers were also included.
That could potentially solve water quality and cultural challenges, Mr Caygill said.
''The report will provide water management zone committees with the information they need to make comparisons between the Tekapo concepts and other ideas and proposals for bringing water into the relatively water-short South Canterbury region.
''While the report primarily looks at the economic costs and impacts of the Tekapo transfer concepts, it also takes into account environmental and cultural values that are central to the Canterbury Water Management Strategy.''