H12D-02
Progress in the identification of catchments with co-existent multiple steady states and finite resilience
Abstract:
Hydrology has implicitly assumed that catchments are infinitely resilient to droughts and floods. No matter the magnitude of the climatic disturbance, almost all hydrological models simulate full recovery and hence assume infinite resilience. Recent research shows that catchments can undergo fundamental change during major droughts and this change in behavior is not captured by rainfall-runoff models.Drawing from recent hydrological resilience theory on catchment disturbance and recovery, a data-driven hidden Markov model is proposed for identifying recovery to a different hydrological state following major climatic disturbances. Application to selected unregulated catchments within Victoria, Australia, shows that after the Millennium Drought (~1995-2010) some catchments are yet to recover and have persisted within a functionally different hydrological state compared to that prior to the drought. Conversely, some catchments fully recovered at the cessation of the drought. This provides the first known field evidence that some catchments may have multiple attractors. Additionally, catchments are shown to differ in their resistance to the drought, with some catchments switching to a drought state at the commencement of the meteorological drought while other catchments taking ~10 years to switch to a hydrological drought state. In addition to separating hydrological droughts from meteorological droughts, this research provides a pathway for quantifying catchment resilience and resistance to climatic disturbances.