The high-level algal warning (Red Alert) has been cleared for the Bogan River at Gongolgon, located 70 kilometres south of Brewarrina.
A red alert level warning (high alert) for potentially toxic blue-green algae was issued in February this year.
Monitoring by WaterNSW has shown that concentrations of blue-green algae have declined, prompting the Red Alert to be lifted.
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.
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. 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