A palaeoclimatic rainfall history from lake broadwater, Southeast Queensland, Australia

A palaeoclimatic Holocene rainfall history is reported for Lake Broadwater in southeast Queensland, Australia. This naturally occurring semi-permanent freshwater lake is part of the Condamine-Balonne Catchment on the Darling Downs. It is an important natural habitat for waterbirds and other wildlife, but it dried-out completely during the Australian Millennium Drought from 2001-2008. Lake sediments were sampled to a depth of about 1.7 m from the centre of the lake in March 2007. A detailed chronology developed from radiocarbon (C) dating indicates that sedimentation was fairly constant into the lake and averaged ~0.16 mm year since about 11 kyr cal B.P. An interpretation of the palaeoclimatic record indicates higher rainfall and moist conditions prevailed from ~11 kyr to ~3.5 kyr cal B.P., followed by lower rainfall, decreasing further from ~2.2 kyr cal B.P to the present day. This change to drier conditions most likely reflects an increase in frequency and/or intensity of El Niño– Southern Oscillation (ENSO) cycles which began in the mid–late Holocene and has been identified from other proxy records elsewhere in eastern Australia. The change to a lower rainfall regime suggests large-scale ocean/atmospheric circulation changes affecting not only coastal regions, but also inland regions of eastern Australia including the northern parts of the Murray–Darling Basin