Hervey Bay and Its Estuaries

Although widely recognised for its exceptional biodiversity, little is known about the physical processes and climate characteristics that shape its natural marine environment. Only recently, the Bay has been classified as a large low inflow and predominantly hypersaline system. River runoff and discharge from its many estuaries is very small. It has almost been absent during the Australian Millennium Drought lasting the first decade of the twenty-first century. During other times, freshwater inflow is only significant following flooding as a result of tropical/subtropical depressions, which often is amplified during La Nina events. A positive freshwater balance leads to a net loss of water establishing hypersaline conditions. This appears to prevail throughout the year and is re-established shortly after storm events. Hydrodynamic modelling suggests that predominant southeasterly to easterly trade winds establish a cyclonic water renewal pathway, with Hervey Bay water exiting along the western shoreline. Hypersalinity and the characteristics of an inverse estuarine circulation are evident from observations and modelling.