Hypoxic blackwater presents a fundamental challenge to the management of regulated rivers in the heavily-forested Southern Murray Darling Basin. Hypoxic blackwater events are characterised by high levels of dissolved carbon and low concentrations of dissolved oxygen that can occur when a previously dry part of the riverine corridor (channel or floodplain) is inundated. In this presentation we draw on historical and contemporary accounts of hypoxic blackwater events to explore its impact on aquatic ecosystems, the changing nature of how they have been perceived by humans, and the effectiveness of attempts to mitigate their impact. We also explore the role of hypoxia as a disturbance event, shaping the structure of aquatic populations, and the nature of how the disturbance has changed in extent, severity and frequency as a result of anthropogenic change. Climate change predictions for the Southern Murray-Darling Basin show a possible increase in the severity of heat waves during summer while also increasing the likelihood of intense rainfall that could trigger aseasonal flooding. This altered pattern of high temperatures and rainfall has the potential to interact with river regulation to affect the frequency and severity of hypoxic blackwater events. We use literature and a semi-quantitative modelling approach to distil the drivers of hypoxic blackwater into several key principles to better understand the critical thresholds where climate change, through hypoxic blackwater, might cause irreversible damage to aquatic communities.