Response of sediment discharge to soil erosion control in the middle reaches of the Yellow River

Abstract

Under the background of large-scale, high-intensity, comprehensive soil erosion control, the sediment discharge of the Yellow River has undergone profound changes. The quantitative evaluation of the influences of soil and water conservation on sediment discharge is not only an inevitable requirement for the objective assessment of the ecological benefits of soil and water conservation projects, but it is also a prerequisite for gaining a scientific understanding of the causes of the drastic changes in the sediment discharge of the Yellow River. Taking the trunk stream in the Toudaoguai-Tongguan section of the middle reaches of the Yellow River and its 24 primary tributaries as the research objects, the Mann-Kendall test and the double mass curve were used to determine the spatial–temporal changes in the sediment discharge over the past 60 years. The results show the following. 1) The average annual sediment discharge in the Toudaoguai-Tongguan section decreased by 81.1% (P < 0.001) over the past 60 years, with a sudden decrease in 2000. 2) From 1956 to 2000, the Toudaoguai-Wubao section, the Wubao-Longmen section, and the Longmen-Tongguan section contributed 34.76%, 30.60%, and 34.64%, respectively, to the sediment discharge measured at Tongguan station. After 2000, the contribution rates were 11.17%, 38.93%, and 49.9%, respectively. 3) Compared with 1956–2000, the average annual sediment discharge of the primary tributaries during 2001–2016 decreased by an average of 85.61%. Marginal benefit analysis indicates that, once the degree of soil erosion control in the study area reached the critical value of 32%, the marginal sediment reduction benefits of the soil and water conservation measures approached 0. Once the degree of soil erosion control exceeded 50%, the sediment discharge in the river basin decreased to a low level. These research results provide a reference for future directions and priorities in soil erosion control planning and implementation on the Loess Plateau.