Examining past and projecting future: an 800-year streamflow reconstruction of the Australian Murray river

Abstract Managing water security and sustaining ecosystem functions under future warming poses substantial challenges for semi-arid regions. The Murray–Darling Basin (MDB) is particularly vulnerable given the considerable demand that underpins Australia’s agricultural production contribution to national economy. Understanding drought risk requires a robust assessment of natural variability in length, frequency, magnitude. In absence long instrumental records, past characteristics can be inferred from paleo-records. We reconstruct over 800 years Murray River streamflow using suite tree-ring chronologies regions with strong climate teleconnections MDB. reconstruction (1190–2000 CE) captures broad spectrum variability, not fully represented contributing an improved understanding occurrence rate multi-year droughts. found Millennium Drought, which occurred 2000s, was most severe (joint duration, magnitude, peak) during 800-year reconstruction. return period this event estimated ∼2500 years. However, droughts early-1200s were longer duration similar magnitude Drought. used models assess how probability might change future. Compared baseline, project increase severity. While within uncertainty range projections, driest forecast shows significant likelihood compared variability. Our results highlight need management strategies rely solely on data as it may represent current risks. Ensuring resilient MDB will require policy broader anthropogenic than currently recognised.