Sediment dynamics of a large tropical river system: the Burdekin River and Lake Dalrymple, Australia

The Burdekin River Catchment is situated in the dry tropics region of Northern Queensland, Australia and covers 130,000km2. As the second largest catchment in the state it impacts significantly upon the Great Barrier Reef shelf system in terms of water, sediment and nutrient exports, but due to the seasonal nature of rainfall in the region, these impacts are highly episodic. In 1989, the Burdekin Falls Dam was built in order to provide a storage reservoir for irrigation. It was expected to act as a sediment trap, however the reservoir fills and overflows during flood events, which carry large amounts of suspended particulate matter. The reservoir is chronically turbid (>100NTU) and consequently discharge from the dam is no longer clear during the dry season, which may potentially cause adverse affects downstream.\ud \ud Our investigation into the characteristics, source and fate of sediment in the Upper Burdekin catchment and its behaviour within the system has been undertaken within the two major inflowing rivers (Suttor and Burdekin Rivers) and impoundment area during baseflow and stormflow periods. Preliminary results indicate that the high turbidity relates to fine clay minerals of generally