The Central Tablelands Water region will move to Level 4 restrictions on January 1.

CTW director of operations Noel Wellham said they had flushed out a scour outlet at the bottom of the dam, near Carcoar, as a precaution.

Mr Wellham said they were concerned if the dam level dropped to 20 per cent they would not be able to access the water as it would be below the outlet valve.

"We are looking at a worst case scenario," he said.

Mr Wellham said they used the water pressure from the dam last Wednesday to clean silt from the scour outlet on the dam floor to ensure it could be used in the future.

"We have cleaned that part of the dam," he said.

"We have flushed the dam out and got rid of much of the silt."

However the sudden rush of water down the creek sparked comments on social media with people concerned CTW was "hiding" the reason for the flow.

One person who commented, Jenny Cowan, said people had been told different stories.

"What are these people hiding and why so many so-called answers," she wrote on Facebook.

CTW general manager Gavin Rhodes urged people in future to contact the CTW office with any queries.

Farmer George King's property fronts Coombing Creek for about four kilometres and he has welcomed the flow.

"It was wonderful," he said.

"It was a really well-timed environmental flow."

He said another farmer had about a three-kilometre creek frontage.

"Both of us are just over the moon and so are the birds and the frogs," he said.

Mr King said it would also benefit people in town as accessing the lower-down water in the dam would provide more water for longer.

"Coombing Creek is a high value environmental waterway and wetlands, home and stronghold to the endangered Booroolong frog, species of water birds, and platypus," he said.

"This flow has filled the water holes which we expect will maintain the environment for the rest of the summer period."