The dam is currently at 97.2 per cent capacity with any significant rainfall likely to move algal concentrations downstream in Paterson River should the dam spill.

A Red Alert level warning indicates that people should not undertake recreational activities where they may be coming into direct contact with the water such as swimming, as well as domestic uses including showering and washing.

Contact with the water may also pose a threat to livestock and pets.

People are advised not to enter the water, not to 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.

Warning signs are positioned at key recreational areas and will remain in place while high levels of blue-green algae are present.

Livestock owners are reminded to continue to check stock water supplies for blue-green algae and to remove stock from foreshores where surface scum is visible or blue-green algae are suspected.

People should not eat mussels or 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.

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.

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

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

Blue-green algae occur naturally and can reproduce quickly in favourable conditions where there is still or slow-flowing water, abundant sunlight and sufficient levels of nutrients.

It is not possible to predict how long the algae will remain at high levels.

Regular monitoring will continue, and the alert will be lifted as soon as the high levels of algae dissipate.

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

Updates about blue-green algae blooms and red level warning areas can be obtained by calling 1800 999 457 or visiting – http://www.waternsw.com.au/water-quality/algae