Lake flow release to clean up river

18:56, Feb 23 2014

Opuha Water will release a major flow from Lake Opuha this week in an effort to clean the lower Opihi River of toxic algae and didymo.

More than 40 cubic metres per second of water, about four times the average flow of the river, will be released for several hours on Thursday.

The company attempted a similar-sized release last summer, but chief executive Tony McCormick said it was not as successful as had been hoped.

"We couldn't quite get it up to that peak flow that really rolls the rocks over and cleans things up [at the confluence near Raincliff Stream]," he said.

Mr McCormick said it would work with the National Institute of Water and Atmospheric Research (Niwa) and Environment Canterbury (ECan) on the water release.

"We want to collect as much data as possible to ensure we know what's under there, but also how we can best clean it up," he said.


Mr McCormick advised people to stay clear of the lake during the high flows.

"It's not going to be a massive torrent, but we want people to exercise some common sense," he said.

In the past few summers, there have been health warnings near parts of the Opihi and Opuha Rivers due to outbreaks of toxic algae.

Currently, both were declared safe for swimming, but Mr McCormick said it was keen to assist with improving the water quality.

He said the company was still planning to lodge consents for its $1.5 million upgrade of the dam's weir system, but would consult with local iwi before it did so.

The Timaru Herald