Interrill and rill erosion tracing on cultivated slopes using 7Be during individual rainfall event

Understanding the processes of interrill and rill erosion is necessary to develop soil erosion prediction models. However, it is difficult to obtain the information using traditional monitoring techniques. In the study, considering deposition at the base of slope area, 7Be was used as a tracer to describe the interrill and rill erosion dynamic during a simulated rainfall event in a slope farmland with a gradient of 25°. The results indicated that the appearance time of significant rill calculated by 7Be content of sediment exuded from the A and B plots was delayed for 45 min and 11 min respectively compared with actual time because of deposition at the base of slope area. Based on the mass balance of 7Be in the eroded soil and in the sediment and the balance of sediment mass, contributions of interrill and rill erosion were separately partitioned to the total soil loss, deposition at the base of slope area and sediment from the plots. In total, the contributions of interrill erosion to the sediment which was delivered out of plot gradually decreased temporally and rill erosion increased. In both plots, the relative errors between calculation values of rill erosion on slopes and deposition in the foot area using 7Be and measurement values of them were low. Therefore, 7Be tracer could accurately quantify the processes of soil erosion.