Characteristics of heavy rainfall and floods in the Dawen River Basin from 2001 to 2022 and their relationship analysis

Understanding the characteristics of actual heavy rainfall and floods in a river basin, summarizing the characteristics of floods and their response to flood-causing rainfall, and studying the runoff generation and flow rules are of great significance for accurate and detailed simulation and prediction of floods in the basin. Taking the Dawen River Basin as the study area, based on the observed rainfall and flood time series data from 2001 to 2022, the characteristics of episodic heavy rainfall and floods were analyzed. Indicators such as precipitation spatial moments and flood concentration were selected to characterize the characteristics of heavy rainfall and floods. The Kendall rank correlation analysis was used to study the response relationship between heavy rainfall and floods, and the precipitation-runoff relationship in the basin was statistically analyzed. The results show that: (1) The rainfall in the Dawen River Basin exhibits a characteristic of more rainfall in the east and less in the west, and the heavy rainfall events corresponding to floods often cover 1/3 to 1/2 of the entire basin, with the center of heavy rainfall mostly concentrated near large and medium-sized reservoirs in the upper reaches. (2) The total amount of floods in the sub-basin of the North Branch of the Mouwen River is relatively large and is the main source of floods in the Dawen River Basin. The flood characteristics are weakly positively correlated with the intensity of flood-causing rainfall, but negatively correlated with the first-order precipitation spatial moment, indicating that the sub-basin has strong storage capacity. In contrast, the sub-basin of the South Branch of the Chaiwen River shows the opposite trend. (3) The flood runoff in the Dawen River Basin is mainly controlled by storage runoff with some infiltration runoff. In the past 22 years, there has been very little runoff in the Da-Dai section, which is closely related to the special water-rich geological conditions and irrigation water diversion in this section. Therefore, special attention should be paid to this section in hydrological simulation and flood forecasting in the basin.