As a result Hunter Water will begin on June 3 drawing water from the Tomago Sandbeds in an effort to provide additional security for the region's dams.

The combined total storage currently sits at 67.5 per cent with Grahamstown Dam at 67.3 per cent.

According to Hunter Water investment officer Darren Cleary, sandbeds are a safe and reliable back-up water supply that can provide 20 per cent of the Lower Hunter's drinking water during times of shortfall.

"The Tomago Sandbeds are a critical part of our drought response. During dry periods, there comes a crucial time when we need to start drawing water from the sandbeds, because if we leave it too long, the water simply won't be there later in a drought," he said.

"The safety of our drinking water is paramount. We've done a lot of work over decades to understand how the sandbeds operate and how the water flows, and this includes extensive water quality testing.

"When we look to use the borefields within the sandbeds as part of our water supply, we are extremely rigorous to make sure it is safe for drinking.

"We routinely monitor the water at the borefields, then as it arrives at the treatment plant and again before it goes to our customers' homes. This testing confirms that our drinking water is safe."

Mr Cleary said that Hunter Water had isolated bore stations 7 and 9 located inside the Williamtown Management Area as a precaution.