Rainfall, runoff, and suspended sediment dynamics at the flood event scale in a Loess Plateau watershed, China

River runoff and suspended sediment play a critical role in the chemical, physical, biological processes of Earth's ecosystems. We assessed the temporal changes in runoff and sediment load at both the annual and event scales in the Gushanchuan watershed in the middle reaches of the Yellow River. A total of 330 events, from 1955 to 2018, were selected to evaluate the relationships between rainfall, runoff, and suspended sediment load at the Gaoshiya gauging station. Significant reductions were examined in the maximum runoff peaks, suspended sediment concentration, total runoff, suspended sediment yield, and ratio of event runoff to annual total, whereas the ratio of event sediment yield to annual total remained relatively stable. Hysteresis analysis suggested that the complex loops, anti-clockwise, and figure-eight loops accounted for 93.7% of the total events in the watershed. High positive correlations were observed between the flood-event sediment yield, runoff volume, maximum runoff peaks, and total rainfall amount. The flow-sediment relationship can be well fitted by the proportional model, and was weaker in 1997-2018 than those in the periods of 1955-1979 and 1980-1996. Runoff during the rising limb of the event significantly contributed to the total runoff and sediment yield. Land use changes and various soil conservation practices were responsible for the decrease in the flood frequency and magnitude. The results of this study provide useful insights into the relationships between rainfall, runoff, and suspended sediment dynamics, and their responses to soil conservation practices.

Automated summary

This study assessed the temporal changes in runoff and suspended sediment load in the Gushanchuan watershed, and found significant reductions in runoff peaks and suspended sediment concentration. The study also revealed the correlations between rainfall, runoff, and suspended sediment dynamics, as well as their responses to soil conservation practices.