Streamflow Flash Droughts in Australia: Occurrence, Characteristics and Impacts

Flash droughts, characterized by their rapid onset, are typically associated with rapid soil moisture depletion caused by insufficient rainfall and heightened evaporative stress. This study broadens the traditional impact-based definition of flash droughts to reveal their significant effects on water resources, specifically through streamflow flash drought events. By analysing perennial catchments across Australia, we identified instances of abrupt reductions in streamflow volumes over short periods. Remarkably, these events can arise from a range of antecedent conditions—wet, normal, or dry— and can potentially have damaging consequences. The severity of impacts varies non-linearly with catchment characteristics, with larger catchments often being more vulnerable. During the onset of these events, streamflow volumes typically decline by a median of 60%, underscoring the intensity of these events. Additionally, such events occur at an average frequency of two per decade across most regions. These findings emphasise the need to enhance the monitoring, forecasting, and management of these events to mitigate the adverse effects on water supply, agriculture, energy production, and other water-reliant sectors.