Spatio-temporal dynamics and drivers of drying conditions in the HRB: Unraveling the role of precipitation intensity and total precipitation in drying risk

Study region: The Hangbu River Basin (HRB), located in eastern China, is the largest sub-basin of the Chaohu Lake Basin. In recent decades, the HRB has experienced increased drying and spatial heterogeneity in its hydrological conditions, despite no significant trend in total precipitation in the region. To address this, this study integrates 65 years (1959–2023) of meteorological and hydrological data with the Palmer Drought Severity Index (PDSI), the Soil and Water Assessment Tool (SWAT) hydrological model, and multiple trend analysis methods to reveal the basin’s dry-wet characteristics and the driving mechanisms. The specific objectives are to: (i) analyze the spatio-temporal heterogeneity of precipitation and hydrological components within the basin; and (ii) quantify the spatial differences in dry-wet characteristics and elucidate the underlying precipitation patterns that shape the basin’s hydrological regimes. Our results reveal that (1) The downstream area frequently experiences years with high precipitation intensity (independent variable x) but low total precipitation (dependent variable y) (with a smaller linear slope, k = 36), which exacerbates the drying risk; (2) In contrast, the upstream region experiences years with high precipitation intensity and high total precipitation (with a larger linear slope, k = 189), which reduces the drying risk. Our findings highlight that the linear structure of precipitation is a key determinant of regional wet-dry conditions. • Links linear slope of total precipitation and intensity to dryness and wetness. • Downstream region experience more severe drying than upstream region. • ET is higher in the downstream, while WY is lower compared to upstream.