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Cold water curtain failure sends chilly water down Macquarie River, threatening fish recovery

By Lucy Thackray, Saturday October 24, 2020 - 10:26 EDT
ABC image
The cold water curtain at Burrendong Dam was installed in 2014. - ABC

A world-first trial has failed at Burrendong Dam in the NSW Central West, sending cold water rushing down the Macquarie River and threatening the recovery of native fish after the drought.

A $3.4 million 'cold water curtain' was installed in 2014 to try to prevent cold water being released from the bottom of the dam, with warm temperatures required for fish breeding.

Now, Water NSW says the infrastructure has failed and water of just 12.2 degrees Celsius released — plunging water temperatures in the Macquarie River between the dam and Dubbo.  

This shock of cold water is known as "cold water pollution".

"An inspection has revealed some damage to the curtain again. As a result, the trial involving the curtain has been discontinued," Water NSW spokesperson Tony Webber said.

"We're going to remove the curtain from the outlet tower at Burrendong Dam and get an engineering assessment into what the damage is and whether it can be fixed."

Infrastructure trial fails again

The infrastructure has failed three times since it was installed.

"In summer, the dam storage stratifies so water is warmer at the top of the dam and quite cold deeper down," Mr Webber said.

"The objective of the curtain is to only draw water from the surface, which is warmer and closer to the naturally occurring temperature in the river.

"Cold water pollution is a world-recognised phenomenon with dams.

"This was an experiment to try to limit the impact of that cold water on the downstream environment."

Interruption for fish breeding

Local fisherman Matt Hansen was devastated an opportunity for native fish to recover from the drought and recent fish kills could be seriously impacted.

"Breeding season for native fish was in full swing, the surface temperature of Burrendong Dam was sitting at a beautiful 22 degrees over the weekend and springtime really had the fish starting to move and breed," Mr Hansen said.

"Murray cod start to nest and breed at around 18 degrees so the water's very, very chilly for them now — more like winter temperatures.

"Certainly we won't see those cod stimulated to breed while thermal pollution is pouring out of the dam."

Mr Hansen is also the president of the Inland Waterways Rejuvenation Association, a group that has been focusing on rejuvenating fish species after the drought.

"Over the past 12 months we've had volunteers up to their armpits in mud rescuing fish on the Macquarie River … so we'd have some fingerlings to replace the hundreds of thousands of fish that died," he said.

"This [spring] was absolutely critical, so fish remaining in the system could have a strong breeding event."

The end of the trial?

The Member for Dubbo, Dugald Saunders, said it could be time to abandon the trial and look at other options to prevent thermal pollution.

"Not much can be done to warm the water," Mr Saunders said.

"What has become evident is this thermal pollution curtain has had significant problems in its short lifespan.

"The question has to be asked now about what other options there might be."

Water NSW is obliged to try to address cold water pollution when releasing water from dams.

"I would probably be one of those saying it's time to stop throwing good money after bad," Mr Saunders said.

"The structure itself is obviously struggling to cope with the conditions in Burrendong Dam."


© ABC 2020

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