Multiscale temporal variability of flow-sediment relationships during the 1950s-2014 in the Loess Plateau, China

摘要

Flow-sediment relationships provide insights into the erosion and transport of materials within catchments. Investigating the flow-sediment relationships across multiple timescales can reveal trends related to the effects of natural and human-caused changes to catchments. This study chose fourteen main catchments in the Loess Plateau of China, which are the major sediment sources of Yellow River, to extract the temporal patterns of flow-sediment relationships during the 1950s-2014 period. The study revealed quantifiable effects of land use/cover changes (LUCC) on the variability of flow-sediment relationships. The LUCC induced by the soil and water conservation measures (SWCMs) during 1970-1999 and vegetation restoration campaign since 2000 resulted in significant reductions of annual streamflow, sediment yield and sediment concentration. The mean daily sediment concentration under different flow conditions also decreased greatly. The flow-sediment relationships revealed time dependence over different stages and time scales. Before 2000, the annual and monthly flow-sediment relationships could be generally characterized by the linear functions, and the power-law sediment rating curve was able to describe the daily flow-sediment relationship. As vegetation restoration campaign took effect, the flow-sediment relationship became much weaker, which could not be described by a clear relationship. This suggests that the variability of flow-sediment relationships over the entire period was mainly regulated by the vegetation restoration campaign. In addition, the sediment concentration exhibited a linear decreasing relationship with the area under land use/cover treatment. In this way, the study has brought out the roles of ecological restoration measures in controlling the temporal variability of flow-sediment relationships at the catchment scale.