Water NSW said a red alert indicates that people should not undertake recreational activities where there’s 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.

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 are safe to drink.

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.

Blue-green algae usually appear as green paint-like scum 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.

People should not eat mussels or crayfish from areas where a red alert is in place, while any fish caught should be cleaned and washed thoroughly in uncontaminated water and any internal organs disposed of before consumption.

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 www.waternsw.com.au/water-quality/algae.