Abstract: An in-depth understanding of watershed runoff generation and flow confluence characteristics holds significant importance for enhancing high-precision flood forecasting and optimizing hydrological mathematical-physical models.Taking the Lushui watershed in eastern Hubei Province as a case study, we systematically extracted geographical elements including soil properties, vegetation coverage, topographic slopes, and rainfall spatial distribution characteristics.Twenty-one typical flood events from 2020 to 2024 were selected to quantitatively analyse impacts of rainfall and underlying surface characteristics′ spatial heterogeneity on runoff generation and flow confluence processes.The results demonstrated that: ① A strong correlation (linear correlation coefficient≈0.9) was observed between rainfall amount and runoff yield in the Lushui watershed, with an average runoff generation coefficient of approximately 0.47.Through analysis of typical flood events, the runoff generation coefficient was found to exhibit a distinct negative correlation with soil thickness.② In the upper watershed area above Maojiaqiao, where thinner soil layers and pronounced topographic relief were identified, the average runoff coefficient reached approximately 0.6, categorizing this sub-region as a high-runoff-yield zone within the basin.③ The basin confluence time of the Lushui watershed was determined to be approximately 12 hours.The flood peak at Chongyang Station was observed to precede that at the Lushui Reservoir by 1~2 hours, while both the Maojiaqiao and Bainiqiao sub-watersheds exhibited confluence times of approximately 9 hours.④ Due to the Lushui watershed′s limited areal extent, low rainfall spatial heterogeneity, and fan-shaped river network configuration, the spatial distribution of rainfall was shown to exert minimal influence on runoff generation characteristics.This hydrological pattern resulted in nearly simultaneous flood peak arrivals (within 3 hours) at the Lushui Reservoir from the Chongyang, Maojiaqiao, and Bainiqiao stations, which contributes significantly to the intensified flood control pressure on the Lushui Reservoir.The research results play an important reference role in understanding the hydrological characteristics of the basin and supporting flood forecasting and dispatching.