Comparison of Changing Population Exposure to Droughts in River Basins of the Tarim and the Indus.

Droughts are major, large‐scale, weather‐driven natural disasters, on the rise in the changing climate. We project changing population exposure to drought in two vulnerable, adjacent, basins of large rivers, the Tarim River Basin (TRB) and the Indus River Basin (IRB), for the future horizon 2021–2065. Drought events are assessed based on the outputs of multiple Global Climate Models, by applying the Standardized Precipitation Evapotranspiration Index (SPEI) and the Intensity‐Area‐Duration method (IAD). Future population exposure to droughts is evaluated by combining the drought events under three RCP scenarios (RCP2.6, RCP4.5, and RCP8.5) with the projected population from Shared Socioeconomic Pathways (SSPs), acknowledging the recent two‐child policy in China. Results show that frequency of drought events in both river basins could increase in the future, while increase in the TRB is stronger than in the IRB. The areal coverage of drought events in both river basins is projected to be greater in 2021–2065 than in 1961–2005. Increase of frequency and areal coverage in both basins is especially strong for the class of extreme drought events. According to the ensemble mean of multi‐GCMs, population exposure to droughts was 25.0% and 20.9% of the total population in the TRB and the IRB, respectively, in 1961–2005, and it is projected to increase by over 60% for the TRB and to increase by over 30% for the IRB, in 2021–2065. Plain Language Summary: As a major, large‐scale, weather‐driven natural disaster, drought may occur in all climatic zones and cause significant losses in human and natural systems. Both the Tarim River Basin and the Indus River Basin are vulnerable to drought, but changing characteristics of population exposure to drought is unknown for the two basins under the climate and population dynamics scenarios. We analyze the changing frequency and areal coverage of drought events in 2021–2065 relative to 1961–2005 and then quantify the population exposure to drought in both two river basins. It was found that frequency and areal coverage of drought in both river basins could increase in the future. Increase of frequency and areal coverage in both basins is especially strong for extreme drought events. Population exposure to droughts was 25.0% and 20.9% of the total population in the Tarim and the Indus River Basin, respectively, in 1961–2005, and it is projected to increase by over 60% for the Tarim River Basin and by over 30% for the Indus River Basin in 2021–2065. Key Points: This research combine the Representative Concentration Pathways and the Shared Socioeconomic Pathways scenarios in the drought exposure assessmentThis research project drought events in river basins of the Tarim and the Indus, based on the multiple GCM outputs and the Intensity‐Area‐Duration methodDrought is projected to be more severe in the TRB than in the IRB, while population exposed to droughts in the IRB has been and will be larger than in the TRB [ABSTRACT FROM AUTHOR]