Murky Blowering Dam closure communication not good enough: mayor, MP

WaterNSW, which manages the dam just south of Tumut, announced through its Facebook page and website on Friday morning Blowering and its foreshores was closed "for maintenance activities".

The sudden closure blindsided Snowy Valleys residents, visitors and community leaders, and the dam remains off-limits until further notice.

Despite updating its original post on Friday afternoon to clarify the closure covered boat ramps, water activities including boating and swimming, the water's edge and vehicle access to the dam wall, WaterNSW did not reveal until Saturday morning it was investigating "a potential water quality issue".

"WaterNSW has temporarily closed Blowering Dam as a precautionary measure to protect the community, while urgent investigations into an unknown, black organic matter observed on the lake surface take place," a statement issued late on Saturday afternoon said.

"Water samples from multiple areas across the dam are being sent for analysis. Laboratory testing is being prioritised with results expected in the coming days."

The detection was first made on the lake surface on Jounama Dam on Thursday afternoon and samples have been sent to Sydney for testing.

WaterNSW said on Sunday they've communicated the dam's closure via social media and the Blowering Dam page on its website.

Snowy Valleys mayor Ian Chaffey said he only discovered the closure when he got a call from a local resident on 8.38pm on Friday.

"At no point in time have I been informed by WaterNSW the dam was shut - the first I heard about it was someone ringing me up as the mayor and asking if I knew why," Cr Chaffey said.

Cr Chaffey said he was disappointed with the lack of information provided, as many locals were left frustrated as they found the dam was closed upon arrival.

"There has been no formal warning on the Snowy Mountains Highway to say the Blowering Dam was shut," he said.

"They could have actually forewarned the public by some VMS board in Tumut or something to that effect."

While there has since been some clarity provided since, WaterNSW could have communicated better with the council, Cr Chaffey said.

Wagga MP Joe McGirr echoed that sentiment and has taken the issue to state water minister Rose Jackson.

"Public safety is the absolute priority and I fully understand that the closure is necessary to allow for testing for a potential water quality issue, but I am concerned that this news was not conveyed more widely to the community when the decision was taken," he said.

"The first that many residents heard of the decision was when they saw closure signs at the dam on Saturday.

"When I became aware of the lack of communication and community concerns, I contacted the minister and expressed my concern."

WaterNSW has since apologised for the short notice and said the closure was a precautionary one to protect the community.

"While this action has been taken as a public health precaution, we apologise for the inconvenience of closing the dam at short notice," executive manager of operations Ronan Magaharan said.

"WaterNSW will reopen access to Blowering Dam as soon as we confirm it is safe to do so."

Those downstream along the Tumut River should not face any issues with their water quality, Snowy Valleys Council's interim manager Steven Pinnuck said he has been assured.

Meanwhile, a blue-green algae bloom on Burrinjuck Dam at Woolgarlo saw a red alert issued for that waterway on Thursday, with WaterNSW advising people against drinking, entering or otherwise coming into contact with the water.

"This red alert warning applies only to untreated water at the identified location and will remain in place until monitoring and test results confirm that the risk is sufficiently diminished. People should avoid consuming untreated water from this waterbody and prevent pets and livestock from drinking this water," WaterNSW said.

The alert remained in place on Sunday.