Waterlogging Assessment and Characteristic Analysis of Three Typical River Basins in China during 1961–2024

Taking the three typical river basins of Liaohe, Huaihe and Pearl River as the study areas, based on the precipitation observation data of national meteorological stations from 1961 to 2024, and using hydrological regionalization of the basins as the basic unit, the Standardized Precipitation Index (SPI) was adopted to construct an annual waterlogging intensity index of the basin considering monthly precipitation anomalies. On this basis, waterlogging grades were classified. Combined with the Precipitation Concentration Index (PCI) characterizing the temporal distribution of precipitation, the spatiotemporal characteristics of waterlogging and the trend of hazard risk in the three basins were analyzed. The results show that: (1) The annual mean waterlogging intensity of the Pearl River is higher than that of the Huaihe River and Liaohe River, making it more prone to waterlogging.However, the latter two basins experience more frequent occurrences of severe and extreme waterlogging. The spatial differences in waterlogging intensity index and  severe/extreme waterlogging frequency among hydrological regions are small for the Liaohe River, but significant for the Huaihe River and Pearl River. (2)The waterlogging intensity of the three basins all shows significant interannual oscillation and periodic differences during the historical period. The Liaohe and Huaihe Rivers exhibit an increasing trend, while the Pearl River displays a decreasing trend. However, there is no statistically significant step changes or abrupt change points were detected. Since 2020, the waterlogging intensity of the Liaohe and Huaihe Rivers has reached a record high, characterized by a shift toward synchronized, high-frequency waterlogging extreme events. (3)The coverage range of severe and extreme waterlogging in the Liao River Basin exhibits the most pronounced interannual variability, with the highest frequency of years exceeding 70% of the total basin area, followed by the Huai River Basin. Both basins demonstrate distinct decadal clustering characteristics in basin-wide severe and extreme waterlogging events, entering a new high-incidence period after 2020. The Pearl River Basin shows the lowest frequency of basin-wide severe and extreme waterlogging occurrences.（4）A significant upward trend in summer precipitation concentration characterizes both the Liao River and Huai River basins. The concentration degree of summer precipitation in the Liaohe and Huaihe River basins exhibits a significant upward trend. When combined with the enhanced intensity of waterlogging, increased frequency and expanded coverage of severe/extreme waterlogging since 2020, the disaster-inducing risk of waterlogging has been notably elevated. This waterlogging assessment method, integrated with the analysis of precipitation concentration index, can effectively captures the interannual variation patterns and disaster risks of basin-scale waterlogging, offering important reference value for basin-scale climate risk management and disaster prevention and mitigation.