It follows a red alert warning issued on February 26.

Residents are advised not to undertake recreational activities.

"Contact with the water may also pose a threat to livestock and pets," WaterNSW said in a statement on Friday.

WaterNSW said people should not eat crayfish from red alert warning areas.

"Any fish caught should be cleaned and washed thoroughly in uncontaminated water and any internal organs disposed of before consumption," it said.

"The species of blue-green algae identified are potentially toxic and may cause gastroenteritis in humans if consumed and skin and eye irritations after contact.

"Boiling the water does not remove algal toxins.

"People are advised not to enter the water, drink untreated water or bathe in water drawn from the dam while this red alert level warning is in place. Town water supplies remain unaffected and safe to drink."

WaterNSW is also advising livestock owners to check water supplies for blue-green algae and to remove stock from foreshores, where surface scum is visible or blue-green algae are suspected.

"Blue-green algae usually appear as green paint-like scums on the water, near the edges, or as greenish clumps throughout the water," it said. 

"It makes the water appear dirty, green or discoloured and generally has a strong musty or earthy odour.

"People who believe they may have been affected by blue-green algae are advised to seek medical advice."

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