Formation hydro-mechanisms and emergency response of clustered karst waterlogging in southwestern Guangxi

Clustered karst waterlogging triggered by extreme rainfall exhibits noval characteristics of chain-type disaster propagation, underscoring the urgent need for in-depth investigations into its hydrological mechanisms and emergency response systems. This study focuses on the karst waterlogging events in Baise City, southwestern Guangxi, during the period from September to October of 2025, employing hydrogeological surveys and monitoring, remote sensing interpretation, and hydrochemical tracing to reveal the formation and disaster transfer mechanisms of karst waterlogging under extreme rainfall conditions induced by typhoons. The findings indicate that three typhoon processes accumulated 689 mm of rainfall, with a daily maximum of 169 mm. Intense rainfall induced supersaturation of water volumes within the conduit-fracture spaces of karst aquifers, resulting in a decline rate of waterlogging accumulation of merely 2 to 3 cm·d⁻¹. The flood recession half-life of subterranean rivers extended to 9.8 days, with the recession coefficient decreasing to 0.07 d⁻¹, indicating slower recession than the maximum flood events of 2023 and 2024. These observations demonstrate that under extreme hydrological conditions, the karst conduit system operates under a "full water and slow flow" state, increasing disaster risks. The waterlogging water bodies remained stagnant for up to 35 days, leading to elevated chlorophyll concentrations and CDOM (Chromophoric Dissolved Organic Matter) levels averaging higher than those in groundwater, rivers, and reservoirs, indicating a distinct eutrophication trend. This study proposes a climate-hydrology-water environment transmission mechanism for karst waterlogging disasters,identifying that the blockage of sinkholes,mining actvities,and engineering disturbances induce hydrological cascade responses in subterranean rivers and degrade drainage capacity-key factor exacerbating waterlogging. During emergency response to waterlogging, pumping and drainage played a pivotal role, with a single depression achieving staged intensive pumping of 2.6 million m³ and a total drainage volume of 5.0 million m³—marking an unprecedented scale of dewatering operations.The study proposes a waterlogging mitigation framework centered on subterranean river basin management, emphasizing an integrated solution that combines top-down dredging of the sinkholes-karst conduits-discharge outlets continuum with basin-wide collaborative regulation.