An integrated framework for assessing future river basin sustainability using a CMIP6 multi-model ensemble in Australia

Climate change is reshaping drought patterns across Australia, increasing pressure on water-resource security and highlighting the need for more informed and adaptive river-basin management. This study presents a comprehensive assessment of Australia’s future drought-related sustainability from 2031 to 2060 using a Quantile Delta Mapping-corrected, Taylor skill score-weighted multi-model ensemble, derived from ten CMIP6 global climate models (GCMs) under three emission scenarios (SSP245, SSP370, SSP585). The framework applies the standardized precipitation index (SPI) at 3- and 12-month timescales, bias-corrected using Quantile delta mapping, and integrates the reliability-resilience-vulnerability (RRV) methodology to evaluate drought persistence and systemic responses. The ensemble significantly reduced inter-model spread and precipitation biases relative to individual GCMs across diverse climate zones. Trend analysis revealed that decreasing and strongly decreasing annual precipitation trends together cover 57.2% of Australia under SSP245 and decreasing trends affect 59.2% under SSP370, whereas under SSP585 shows no clear trend, indicating greater uncertainty under extreme warming. Projections show intensification in drought duration and severity, particularly under SSP370 and SSP585, with the most spatially consistent increases concentrated across southwestern and southern Australia. RRV indicators revealed comparatively high reliability across most of Australia, but substantially lower resilience for SPI-12 than SPI-3 and increased vulnerability under SSP585, with the most persistent adverse conditions occurring in southwestern and southern Australia. The integrated sustainability performance index indicated that the combined Unhealthy and Very Unhealthy ” area ranges from approximately 35–36% under SSP245 to 44–45% under SSP585, with Southwest Coast, South Australian Gulf, and southern and western parts of the Murray–Darling Basin emerging as the clearest cross-timescale hotspots. The findings may support the identification of drought-prone basins and inform basin-scale water planning, risk assessment, and climate adaptation across Australia.