Cold water curtain assessed by deep water divers
STAFF at Water NSW will now consider their next action after reviewing the state of the cold water pollution curtain at Burrendong Dam. Damaged last year after an extremely wet winter led to an influx of 900,000ML of water into the lake and volume rose from 11 to 135 per cent, the curtain has since not been fully functional.
A team of special deep water divers undertook the task of plunging 35m into Burrendong’s depths to assess the damage and will report their findings to senior management at the State-run facility.
The task, which was carried out in deep, dark, cold waters, was not without its dangers.
“There is an element of risk and we closed release while they were diving,” a spokesperson said.
“The dive was to investigate why the curtain failed,” he explained.
“It was quite a significant undertaking. Divers went down to where the curtain is anchored and spent six hours a day for seven days, requiring a decompression chamber upon resurfacing.
“They will now come back with how to proceed and a report will be sent to senior management.”
The aim is to get as much functionality back as possible, with the curtain’s job to restrict cold water supply which affects the river ecosystem downstream from the dam.
“The amount of cold water is restricted so that only the warm water is released.
“Our intention is to reinstate the curtain, get it back into a functional state,” the spokesman said.
He said water fluctuation levels will be minimal, which will be good news for river users, particularly in the coming warmer months.
“There will be very high demand for irrigators as the season has been exceptionally dry.
“Water levels will fluctuate in the immediate vicinity of the dam but downstream there would be no change – the availability will still be the same, the volume will still be the same.”
It will be better for aquatic life in the river once the curtain is fully reinstated, with the warmer currents better for breeding.
“We are not an authority on fish breeding season but the longer the curtain is out of action, the longer the potential benefits aren’t being experienced.”
The cold water pollution curtain cost between $3.4 and $4M and is the first of its kind in operation.
About the curtain
Cold water pollution can occur when cold water from the bottom of a dam is released into the river. This can have a negative impact on native fish species. Waternsw is working to mitigate the effects of cold water pollution as part of its ongoing efforts to reduce environmental impacts of operations. The project involved construction of a floating-curtain temperature control structure around the intake tower at Burrendong Dam. The flexible structure sits just below the water level to allow warmer surface water to be released downstream through the outlet valve. The curtain can move up and down with the water level via a chain and pulley mechanism to function regardless of the water level of the dam.