Dam operator defends release
The company operating the Opuha dam is standing by its decision to release a large flow of water today, despite concern from a local angler group.
More than 40 cubic metres per second will be released from the dam this morning in an attempt to clean the Opuha and Opihi rivers of didymo and toxic algae.
However, some anglers are concerned this will merely bring messy material down to the lagoon and make the fish unpleasant to eat.
South Canterbury Anglers Club president Allan Davidson said the last time Opuha Water attempted such a release, the results were a disaster.
"Flushing the system when the river is at minimum flow levels only leads to dumping all the debris and foul-smelling toxic algae to the bottom of the catchment," he said.
"When they dump the water at the top of the river, by the time it gets to the bottom, it's not still ripping through it. It won't even open the mouth of the lagoon. It gets really bad in the Opihi lagoon and the fish become tainted."
Mr Davidson said Opuha Water would be better waiting until there was a natural flood.
"What they're proposing is a stop-gap measure which would actually be counterproductive to the river's wellbeing."
The Herald has received correspondence from anglers echoing Mr Davidson's concerns.
However, Opuha Water chief executive Tony McCormick said the release was necessary.
"We do recognise that it is preferable to have a flushing flow on the back of high natural flow in the river ... but we can foresee an even greater problem in the lower catchment if we don't release a flow," he said.
"We cannot wait until the next period of natural high flows to do this."
Central South Island Fish and Game chief executive Jay Graybill said Opuha Water's planned release would be a useful test.
"It's not going to clear up everything, but it will give an idea of what sort of flow might be required. That in itself is a positive step," he said.
Mr McCormick said the company would extend the large flow release period for 20 hours.
"We've got to keep the foot down. The highest flow we can maintain is about 14 cumecs, and we will do our best to maintain it."
He said Opuha Water hoped the increase in the lake's minimum outflow from 3.5 cumecs to 7.5 cumecs next month would also address some of the issues.
- The Timaru Herald