Lethal ‘blackwater’ in NSW river prompts fears of another mass fish kill

A Menindee Lake outlet in far west NSW, shown during Darling river flood surveillance this month. ‘Blackwater’ can stretch for kilometres, leaving no way for fish and other aquatic life to swim through it. Photograph: NSW SES far west command, western zone

Floodwaters carrying “blackwater” lethal to aquatic life are moving south in the Barwon-Darling river towards the Menindee Lakes, raising fears the situation may cause a repeat of events in 2019 where over a million native fish were killed.

Blackwater events are caused when heavy rains wash leaf litter that has collected on a floodplain into a major river such as the Barwon-Darling, turning it the colour of dark tea.