Soil Loss and Sedimentation Rates in a Sub-Catchment of the Yellow River Basin in China

Abstract

Soil loss by water erosion is one of the main threats to soil health and food production in intensively used agricultural areas. To assess its significance to the overall sediment production we applied the Water and Tillage Erosion Model/Sediment Delivery model (WaTEM/SEDEM) to the Luoyugou catchment, a sub-catchment of the Yellow River basin within the Chinese Loess plateau. WaTEM/SEDEM considers rill and inter-rill erosion and deposition rates, resulting in sediment yield rates leaving the catchment. Although terraces were established in the 1990s to reduce soil loss, no further soil erosion modeling has been published for this area. Applying 1000 Monte Carlo simulations of the WaTEM/SEDEM, modeled average soil loss by rill and inter-rill erosion for 2020 was 12.4 ± 11.8 t ha-1 yr-1, with sediment yield at the outlet of 52949 ± 11215 t yr-1. Terracing reduced erosion rates, while land cover changes, mainly conversion of forests and grassland partly counteracted the mitigation (combined effect: 50% reduction). Modeled sediment loads by rill and inter-rill erosion account for 17.1% of the total long-term sediment production recorded by flow discharge measurements. Other processes not considered by the model like landslides, gully erosion, riverbank erosion, and sediment production by construction seem to dominate overall sediment yield. Considering years with baseline sediment production only, measured and modeled sediment yield compared well, indicating that the latter processes contribute mainly during extreme events.