Nyngan and Gongolgon have been featured on the WaterNSW map recently, but for all the wrong reasons.

Both locations have been given a "red alert" status for the presence of blue-green algae after the most recent testing undertaken by WaterNSW.

Red alert levels represent 'bloom' conditions. The water may appear green and may have strong, musty or organically polluted odours. The blue-green algae itself may be visible as clumps or as scums. 

Anyone coming across this should consider the "blooms" as toxic to humans and animals. The water should not be used for drinking (without prior treatment), stock watering, or for recreation.

WaterNSW also cautions that 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. Water NSW advise that fish fillet meals from algal bloom affected areas should be limited to one to two servings per week.

Obviously, avoiding fishing in a bloom location is the best way to minimise risk, particularly catching and eating fish from locations with severe blooms that last extended periods of time.

This is the seventh "red alert" result in a row for the Bogan River at Gongolgon with the last water sampling completed on January 9th this year. Nyngan, which has its water tested at the weir pool, had previously slipped back into the less dangerous amber zone before the testing on February 6th confirmed the levels had again risen to dangerous levels.

But what is blue-green algae and why is it so bad?

 Blue-green algae occurs naturally in rivers and lakes and is a microscopic bacteria known as Cyanobacteria. Too much blue-green algae is bad for water quality and make water unsafe for humans and animals to drink. This is due to the toxins the algae produces.

Blue-green algae are more likely to occur when the water levels are low, and the water is warm, full of phosphorous and low in zooplankton.

They can release neurotoxins that kill animals quite quickly or liver toxins that take 24-72 hours to kill stock.

Blue green algae is a risk to livestock. IMAGE: Agriculture WA

In the Murray-Darling Basin, a 2023 study showed an increase in algae along the River Murry but little change in the Basin.

Interestingly, research has shown that significant changes in the type of blue-green algae have appeared along the River Murray and it is suspected this is due to the Millennium drought.

Some species are now more dominant than others compared to before the drought. Basin blue-green algae trends are likely attributable to changes in land and water management practices under a general warming trend.

The blue-green algae is a small organism but a costly one. Research estimates the cost to tourism of blue-green algae alerts is significant. The cost to treat the algae affected water locations between 2019 and 2021 was six times greater than normal.

WaterNSW encourages people who have seen algal bloom or become aware of larger numbers of fish deaths to contact them on 1800 999 457.