Sydney's water monitored after ash run-off

Water for Sydney will once again be drawn from Warragamba Dam after concerns over ash run-off.
Water for Sydney will once again be drawn from Warragamba Dam after concerns over ash run-off.

Water experts are closely monitoring Sydney's main water supply after rain washed ash and debris into the dam, forcing authorities to use alternative water sources for the city.

Heavy rainfalls over the past week have pushed ash and debris from the summer's bushfires into Lake Burragorang, which is a part of Warragamba Dam.

WaterNSW on Friday said sediment, ash and debris were clearly visible on the surface of the lake.

As a result, the water authority temporarily shut off its supply of raw water to the Prospect Water Filtration Plant, which services Sydney, on February 9.

Water was instead drawn from Prospect Reservoir and the Upper Canal while WaterNSW worked to mitigate the potential risks to dam water quality.

Raw water was still supplied to the township of Warragamba and Orchard Hills.

Warragamba Dam will return as the main source of untreated water supply to Sydney over the weekend, a WaterNSW spokesman said.

"Ongoing monitoring has confirmed confidence in the quality of water available from Warragamba," the spokesman told AAP in a statement on Sunday.

Containment barriers have been installed at three locations on Lake Burragorang to limit the amount of ash and debris entering the dam supply while experts continue to monitor the water quality.

More than 320,000 hectares of land around the Warragamba catchment have been ravaged by bushfires this summer.

Australian Associated Press