Impacts of climate change and sea level rise on catchment management: A multi-model ensemble analysis of the Nerang River catchment, Australia

Abstract Estimating the most likely impacts of climate change on the hydrological conditions of catchments is essential for efficient future water management. This is particularly important in Southeast Queensland, Australia, which is projected to be significantly impacted by climate change. We have developed an integrated catchment modelling framework for the Nerang River catchment that combines a hydrologic model, a reservoir operation model, and a hydrodynamic river model. The multi-model ensemble is used to investigate eight General Circulation Models (GCMs) of the Coupled Model Intercomparison Project Phase 5 (CMIP5) under two representative concentration pathway scenarios (RCP 4.5 and RCP 8.5) over the baseline period (2000-2009) and one future period (2075-2084). Additionally, the tidal section of the Lower Nerang River was studied under coupled impacts of the RCP scenarios and sea level rise by 0.80 m. The ensemble projections over the future period present slight decreasing tendencies in the median of monthly long-term daily inflow to Hinze Dam in the upper Nerang River. Additionally, the average environmental releases of 7.25 ML/day are expected to reduce over the future period by 6.02% and 5.37% under RCP 4.5 and RCP 8.5, respectively compared to the baseline period. The hydrodynamic model results revealed that sea level rise is projected to have significant impact on water level variations at two river flooding alert sites, Carrara Alert and Evandale Alert. As a result, a 0.80 m sea level rise can increase ensemble water level projections by almost 0.75 m and 0.80 m at Carrara Alert and Evandale Alert sites, respectively, which will cause minor to major flooding events at Evandale Alert site. The outcomes of the present paper can assist the decision-makers and the community of the Nerang River catchment with a robust tool to evaluate climate change scenarios for sustainable future water resources management and allocation.