Reduced sediment transport in the Chinese Loess Plateau due to climate change and human activities

Highlights: • The sediment discharge in eight catchments located in the Loess Plateau showed a significant decrease since the 1960s. • Sediment discharge in most tributaries had shown abrupt changes since 1996. • The contribution of runoff reduction was greater than the sediment concentration change to the reduced sediment load. • Increasing vegetation coverage was the primary factor driving the reductions in sediment loads. The sediment load on the Chinese Loess Plateau has sharply decreased in recent years. However, the contribution of terrace construction and vegetation restoration projects to sediment discharge reduction remains uncertain. In this paper, eight catchments located in the Loess Plateau were chosen to explore the effects of different driving factors on sediment discharge changes during the period from the 1960s to 2012. Attribution approaches were applied to evaluate the effects of climate, terrace, and vegetation coverage changes on sediment discharge. The results showed that the annual sediment discharge decreased significantly in all catchments ranging from −0.007 to −0.039 Gt·yr⁻¹. Sediment discharge in most tributaries has shown abrupt changes since 1996, and the total sediment discharge was reduced by 60.1% during 1997–2012. We determined that increasing vegetation coverage was the primary factor driving the reductions in sediment loads since 1996 and accounted for 47.7% of the total reduction. Climate variability and terrace construction accounted for 9.1% and 18.6% of sediment discharge reductions, respectively.