Sediment reduction in the middle Yellow River basin over the past six decades: Attribution, sustainability, and implications

Understanding the underlying driving forces causing changes in sediment yield is crucial for decision-making and major strategy development for the management of the middle Yellow River basin (MYRB). In this work, we quantified the causes of sediment yield reduction in the MYRB and investigated the sustainability of sediment reduction strate-gies. The sediment yield in the middle Yellow River during 1957-2017 exhibits a significant downward trend. The av-erage sediment yield in 1970-2017 decreased by 798.84 x 106 t compared with that during the 1950s to 1960s, with 27.40 % ascribed to decreased precipitation and 72.60 % attributed to human activities. The sediment yield modulus of all sub-basins within the MYRB has been reduced to <5000 t/km2, demonstrating the dominant influence of water and soil conservation measures. Check dams have limited on-site effectiveness in reducing sediment yield but exhibit a dominant effect in trapping the already yielded sediment and preventing it from being delivered into the lower Yellow River. The strong dependence on the storage capacity of check dams makes the system unsustainable in the long run, since it necessitates ongoing investment in check dam construction to maintain the sediment trapping effect. Promot-ing biological measures such as planting trees and grass to increase vegetation coverage is a more sustainable way to fix the sediment on-site and keep it from being eroded. These efforts should be intensified, with appropriate consideration for local conditions.