An irrigation expert has told a resource consent hearing that enforced changes to a controversial irrigation scheme in Canterbury will make the project much less reliable.
A hearing to determine if the Central Plains Water Enhancement Scheme will get the go-ahead resumed on Monday.
If approved, the scheme will irrigate 60,000 hectares of arid Canterbury farm land using water from the Rakaia and Waimakariri rivers, and in doing so boost the region's agricultural production.
The Central Plains Water Company was asked to submit a new proposal for commissioners, as its original concept was partly rejected. A new version of the project is going through the resource consent process in Christchurch this week.
The company wants access to water from the rivers and permission to build canals across the Canterbury Plains to funnel it to 300 shareholders.
Irrigation expert Cliff Tipler told the hearing on Monday that enforced changes to the scheme will make the project much less reliable.
Mr Tipler said that half of the shareholders will have access to groundwater and river water, but the other half will only have river water and the reliability of that is very poor.
The Central Plains Water Company says its scaled-down proposal will take significantly less water from the Waimakariri River.
It admits the new proposal will have 50% fewer economic benefits for its shareholders and the wider community, but says those benefits will still be significant.
Its lawyer Matt Casey, QC, says the submissions to be heard from opponents do not consider the changes to the scheme, but merely repeat the concerns the commissioners have already heard.
Opponents are concerned about the effect on the rivers.
The hearing is set to take most of this week.