Investigation of rainfall‐runoff and sediment yield dynamics under varying slope land use patterns in the Three Gorges Reservoir Area of China

Abstract

Field experiments were conducted on various runoff plots within the Zhangjiachong watershed, located in the Three Gorges Reservoir Area, to study rainfall‐runoff processes and sediment yields under different slope land use patterns. A hillslope run‐on model considering vegetation interception was used to simulate runoff generation and concentration. A slope erosion model including raindrop erosion, sheet erosion, and rill erosion was developed to estimate sediment yield and concentration. The parameters of both models were calibrated and validated using observed runoff and sediment yield data. The results show that the runoff simulations in the validation have relative errors below 20% for all runoff plots, except those planted with crops. The saturated hydraulic conductivity of soil was found to be ca. 10% higher on slope lands with hedgerows than those without. In addition, it was about 15% higher on slope lands with crops than on slope lands with tea plants and citrus. The sediment yield was shown to be influenced by both precipitation characteristics and antecedent sediment conditions. There was a significant relationship between sheet erosion, rill erosion, and vegetation coverage, while the amount of raindrop erosion was similar across different runoff plots. The proportions of sheet and rill erosion on slope land with crops were minimal whether hedgerows existed or not. The proportions of the three main forms of soil erosion on slope lands with tea plants and citrus were more or less the same under concentrated rainfall. For more evenly distributed rainfall, raindrop erosion was the primary form on slope lands with hedgerows‐tea plants and citrus. The proportions of sheet and rill erosion significantly increased on slope lands without hedgerows.