Opposing forces try to win day over minimum flows in Lindis Catchment

The Lindis River in spring flow.

The debate between water experts over the way forward for the Lindis River catchment resumed in an Environment Court appeal in Cromwell yesterday without any sign of who is gaining the upper hand.

On one side are the expert witnesses called by lawyers for the Lindis Catchment Group (LCG) and Otago Regional Council and on the other the experts called by lawyers for Otago Fish & Game Council.

The debate, to be resolved by Judge Jon Jackson and his two commissioners, is over what amount of water can be taken from the river for irrigation while maintaining an acceptable amount of water for wildlife, including trout.

The current level of irrigation leaves the lower part of the river dry for up to 15km at times over summer.

Expert witnesses are being cross-examined on thousands of pages of written evidence, maps, diagrams and graphs, and various future scenarios are being compared.

One scenario is the ORC's plan change 5A decision being appealed by the LCG.

It requires a primary maximum allocation for irrigation of 1200litres per second, with a minimum flow of 900litres per second at the Ardgour Rd flow monitoring site, and is supported by Fish & Game but no longer by the ORC.

The LCG's proposal is for a primary allocation of irrigation water of 1639litres per second, with a minimum flow of 550litres per second, with water taken from bores (referred to as the "gallery'' scenario) rather than from existing water races. This scenario is backed by the ORC but not considered satisfactory by Fish & Game.

And there is the "future races scenario'', which includes a primary allocation of 2255litres per second with a 900litres per second minimum flow.

National Institute of Water and Atmospheric Research (NIWA) hydrologist Roderick Henderson was called by the LCG and said that a flow of 550litres per second at Ardgour Rd ''should allow'' 100litres per second of flow at the confluence of the Lindis River and the Clutha River.

Also, he said, the galleries scenario would mean the river was at its minimum flow 15% of the time compared with 41% if water races were still used.

LCG consultant ecologist Matthew Hickey said the gallery proposal would reduce the maximum amount of water that could be taken from the catchment each year from 43million m3 to 19million m3.

"LCG anticipates that this has benefits by reducing the duration of time spent at minimum flow, maintaining flows that provide for fish passage more often, as well as providing surety of supply levels that allow investment in efficient [spray] irrigation infrastructure.''

For Fish & Game, senior Lincoln Agritech Ltd, hydrogeologist Jens Rekker said the galleries scenario would result in a flow rate of 60litres per second at the Clutha confluence and "drying out of the lower losing reach would become a possibility if groundwater pumping depletion is higher than currently estimated''.

He considered modelling revealed the plan change 5A decision ''consistently provides for higher flow rates and generally better habitat and fish passages'' than the galleries proposal.

mark.price@odt.co.nz