Rainfall-Runoff regime shifts and thresholds induced by multi-year droughts across Victoria

This thesis investigates persistent shifts in rainfall-runoff relationships in Victorian catchments, where post-drought runoff remains low despite rainfall recovery. Using state-dependent models such as Hidden Markov Models (HMMs) and Non-Homogeneous HMMs (NHMMs), the research examines the role of climatic thresholds in driving transitions between runoff states. It presents evidence of multiple stable states, asymmetric resilience, and improved streamflow prediction using probabilistic models. These findings challenge the assumption of infinite catchment resilience and highlight the importance of incorporating climate-driven thresholds to better forecast streamflow and manage water resources under changing climatic conditions.