Changes in future hydrological drought characteristics and risks in the Lancang River Basin

The Lancang River, the upper reach of the Mekong River, is crucial for downstream water and ecological security. Recent frequent hydrological droughts have severely impacted the production and livelihoods of basin residents. This study, based on 1981-2020 hydro-meteorological data, constructed a SWAT model and innovatively used CMIP6’s SSP1-1.9, SSP1-2.6, and SSP2-4.5 scenarios to analyze hydrological drought characteristics and risks in the Lancang Basin (2026-2065). Results show that under all scenarios, monthly runoff and annual SRI sequences increased, with SSP1-1.9 growing fastest and SSP2-4.5 slowest. Non-drought periods were significantly longer than drought periods. From the perspective of hydrological drought characteristics, compared to the baseline, drought duration, severity, and intensity decreased, most under SSP1-1.9 and least under SSP2-4.5.From the perspective of hydrological drought risk, the Lancang River Basin is mainly in low-risk areas under the SSP1-1.9 and SSP1-2.6 scenarios, and is mainly in low and higher-risk areas under the SSP2-4.5 scenario. All scenarios showed reduced risk compared to the baseline, with SSP1-1.9 declining most. The study indicates a future weakening of hydrological droughts in the Lancang Basin, lowering drought risk and benefiting downstream water security, providing a scientific basis for climate adaptation and water management.