Cascading Bias Correction for Assessing the Vulnerability of Water Supply Systems to Multi-Year Hydrological Extremes

Water supply management agencies, especially for large systems, must plan decades in advance to ensure system resilience to extreme hydrological events, in particular droughts and floods. Typically, the envelope within which managers plan for extremes several decades in advance is at least partially determined by Global Climate Models (GCMs). One aspect in which GCMs are deficient is in capturing multi-year variability. As a result, in our study region these models do not capture the magnitudes of the historic driest or wettest multi-year periods on record. Here we propose and demonstrate a method to address this issue at catchment scale for water supply systems, enabling us to develop more realistic scenarios of potential extreme conditions during the twenty-first century.