Impacts of Interannual Climate Variability on Direct and Virtual Water Shortage Risks in China

Water scarcity can have far-reaching sectoral impacts beyond where it physically occurred through the propagation of virtual water flows. Both fast (e.g., interannual meteorological variability) and slow physical processes (e.g., phase changes in sea surface temperature [SST] modes) can affect water availability and use, leading to changes in both direct and virtual water scarcity. In this study, we use a two-stage regression to investigate how interannual meteorological variability and SST-phase changes contribute to variations in water shortage in China, both locally (through the Local Water Scarcity Risk index, LWSR) and remotely (through the Virtual Water Scarcity Risk index, VWSR). More specifically, LWSR and VWSR are estimated using the regression-based water stress indices and agricultural water uses under varying meteorological forcings and SST phases, holding the region-by-sector input-output relationships constant. Our findings indicate that interannual meteorological variability affects LWSR on the order of 10–1000% and VWSR on the order of 10% in most sectors and provinces, with a limited portion of impacts attributable to SST-phase changes. In particular, the positive phase of the second investigated SST mode results in significantly higher (on the order of 5%) LWSR and VWSR for nearly all sectors and provinces compared to the negative phase. These results highlight the importance of using longer time series to accurately assess local and virtual water scarcity situations. Decision makers in susceptible provinces and sectors should consider interannual variabilities in LWSR and VWSR and plan for potential occurrences of extreme conditions.