Spatiotemporal changes in hillslope erosion and river sediment caused by extensive soil-water conservation in the Yellow River Basin

The Yellow River used to be known as the most sediment-laden river in the world, but its sediment load has decreased dramatically in recent decades largely due to anthropogenic changes in the Yellow River Basin (YRB). Despite the observed trends, the spatiotemporal changes in hillslope erosion and river sediment and their response to soil-water conservation (SWC) measures remain unclear. To address the knowledge gap, this study conducted a basin-wide simulation of sediment processes in the YRB for the first time using the Geomorphology-Based Ecohydrological Model and analyzed the impacts of various SWC measures on hillslope erosion and river sediment transport. Our results showed a 72.8% decrease in area-averaged erosion modulus and a 90.6% decline in sediment load at Huayuankou station during 2000-2019 compared with that of 1960-1979. An exponential decay relationship was found between hillslope SWC coverage ratio and soil erosion modulus, indicating diminishing marginal effectiveness of further interventions. The relative decrease in soil erosion modulus was the highest in the Wei River and lowest in the Toudaoguai-Longmen (TDG-LM) section for the same increase in hillslope SWC coverage ratio. Annual sediment amount trapped by check dams relative to hillslope erosion increased from 5.9% in 1960-1979 to 29.7% in 2000-2019. By 2019, the cumulative deposited storage of check dams reached 4.74 billion m³, accounting for 54.3% of the total storage capacity. Compared with other tributaries, the sediment deposition proportions in check dams were relatively lower in Wei River. This research offers a reliable tool for understanding the sediment regime change under intensive conservation measures, and provides important insights for sustainable management in the region.