WATERNSW has issued a high alert for blue-green algae at Gulpa Creek in Mathoura.
The red alert, which was also issued for Edward River at Deniliquin, means people should not swim in the water or use it for domestic use including showering and washing.
Contact with the water may also pose a threat to livestock and pets.
Warning signs are positioned at key recreational areas and will remain in place while high levels of blue-green algae are present.
It is potentially toxic and may cause gastroenteritis 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, 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.
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 is suspected.
Blue-green algae usually appears 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.
People should not eat mussels or crayfish from red level warning areas. Any fish caught should be cleaned and washed thoroughly in uncontaminated water and any internal organs disposed of before consumption.
Blue-green algae occurs 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.
The warning may slowly move downstream with water flow, although current results downstream are at amber levels.
Information updates about blue-green algae blooms and red level warning areas can be received from the Regional Algal Coordinating Committee free-call Algal Information Hotline on 1800999457 or visit – www.waterNSW.com.au