Hervey Bay is situated just outside the southern boundary of the Great Barrier Reef Marine Park off the coast of subtropical southeast Queensland, Australia. It is bowlshaped with an area of about 4000 km2 and a main opening facing northward. At this location, the continental shelf is about 90-100 km wide and the eastward boarder separating the bay from the open ocean is formed by Fraser Island, the world’s largest sand island.
At its northern end, the bay is about 80 km wide and its average depth is about 20 m. In the south, it is connected with the open ocean via a narrow, about 90 km long and shallow system of channels, the Great Sandy Strait and an eastward facing gap of about 2 km width south of Fraser Island. The Mary, Burrum, and Burnett Rivers drain into the bay. The highly managed Mary and Burnett Rivers are the main sources for freshwater with the Burrum River having only a small catchment area. The Mary River mouth is located at the northern end of the Great Sandy Strait and freshwater is drained into the southern parts of Hervey Bay and southward into the Strait itself. The mouth of the Burnett River is found in the north of the study area.
The climate of the region is classed as subtropical with no distinct dry period. Rainfall is at a maximum from about January to April with an approximate climatological average of 150 mm per month for this period, yet rainfall and correlated runoff are characterised by high interannual variability and since about 1950, rainfall in coastal Queensland declined by about 50 mm per decade.