The temporal and spatial evolution of drought-flood abrupt alternation in the Shanmei Reservoir Basin under climate change

Abstract

[Objective] The Shanmei Reservoir Basin, located in a subtropical monsoon climate zone, is frequently affected by tropical cyclones, subtropical high-pressure systems, and complex topography, leading to frequent drought-flood abrupt alternation(DFAA) events that severely threaten regional water security. Accurately identifying and predicting the spatiotemporal evolution of DFAA under global change is crucial for regional disaster prevention and mitigation. [Methods] Shanmei Reservoir Basin was taken as study area. Using the Standardized Precipitation Index with a 12-day antecedent precipitation period(SPI-12d), the spatiotemporal characteristics of DFAA from 1980 to 2018 were analyzed. Additionally, CMIP6 multi-model ensemble projections under SSP2-4. 5 and SSP5-8. 5 scenarios were employed to predict the spatiotemporal evolution of DFAA in the 21st century. [Results] Key findings include:(1) The frequency of drought-to-flood(DTF) and flood-to-drought(FTD) events initially increased significantly and then decreased gradually. DTF intensity rose significantly, while FTD intensity declined. DTF events were concentrated in January, July, and September-December, whereas FTD events mainly occurred from August to November.(2) High-frequency and high-intensity DTF areas were located in the southern watershed, while high-frequency FTD areas were in the northeast and high-intensity FTD areas in the southeast.( 3) Future projections indicate increasing DTF frequency and intensity, with greater increases under SSP5-8. 5. FTD frequency showed insignificant declines under SSP2-4. 5and slight rises under SSP5-8. 5, while FTD intensity decreased. DTF increases were most pronounced in February and December, whereas FTD increases were notable in January, August, and October.(4) The central and southern watershed will face higher risks, with both DTF and FTD frequency and intensity projected to increase. [Conclusion] DFAA impacts in the Shanmei Reservoir Basin are intensifying overall, with the central-southern region as a high-risk zone. DTF poses a greater threat than FTD. These findings provide a scientific basis for DFAA monitoring and response.

Keywords

drought-flood abrupt alternation(DFAA) / climate change / standardized precipitation index(SPI) / Shanmei Reservoir Basin / water safety / spatiotemporal changes / drought