Background Extreme precipitation events occur frequently under the background of global warming, and it is of great significance to understand the spatial and temporal variation characteristics of extreme precipitation between Toudaoguai and Longmen of Yellow River Basin, and to clarify the variation law and influence mechanism of runoff process for soil and water conservation decision-making in semi-arid and sub-humid regions.

Methods Based on the data of 37 meteorological stations in the Toudaoguai-Longmen section from 1960 to 2021, as well as the data of Toudaoguai and Longmen hydrological stations, this study analyzed the spatial and temporal distribution characteristics of extreme precipitation and the dynamic characteristics of runoff in the section, and used PLSR model to explore the relationship between extreme precipitation events and runoff.

Results 1) In the past 60 years, all the extreme precipitation indices except the consecutive dry days, the consecutive wet days, the max 1-day precipitation and the max 5-day precipitation showed an upward trend, and the upward trend of the interval extreme precipitation intensity index was generally higher than that of the extreme precipitation frequency index. 2) The average annual runoff in the Toudaoguai-Longmen section was 3.98×10⁹ m³, with an average change trend of -94.7×10⁶ m³/a since the 1960s, and the runoff showed a significant decreasing trend with the passage of time. Taking 1979 as the boundary, the annual runoff in the section decreased from 6.19×10⁹ to 2.93×10⁹ m³. 3) The PLSR model based on the annual runoff depth of the same section of each extreme precipitation index before the mutation explained 88.4% of the total variance of annual runoff, and the annual total precipitation, the total heavy precipitation and the total extreme heavy precipitation were the most important variables affecting the runoff change between Toudaoguai and Longmen. At the same time, the impacts of extreme precipitation and human activities on the section runoff were further quantified, and the contribution rate of extreme precipitation to the runoff change was 10.6% after the abrupt change.

Conclusions Relatively less precipitation and highly concentrated extreme precipitation events are the main precipitation factors causing soil erosion in the Toudaoguai-Longmen section. In addition to the impact of human activities, extreme precipitation events will still be an important cause of regional runoff changes after entering the period of soil and water conservation projects and returning farmland to forests.