The Darling River basin, located in southeastern Australia, features flat grasslands well-suited for livestock farming. In December 1991, approximately 1,600 cattle and sheep grazing in the basin’s pastures died. An investigation revealed that the cause was linked to the river water consumed by the livestock. At the time, the Darling River was experiencing a severe drought that had lasted over a year, leading to water shortages and extreme eutrophication. The algal bloom in the Darling River demonstrates how natural water can turn into a deadly poison under eutrophic conditions when combined with drought and heatwaves.