Impacts of climate change and human activities on sediment load in Longchuan River Basin, China

Study region: Longchuan River Basin in the Hengduan mountain region, China. Study focus: With the decrease in annual precipitation, the sediment yield on the slope and sediment delivery ratio (SDR) in the river channel, both play a critical role in runoff and sediment load change. However, the response mechanism of SDR to climate change and human activities remains unclear. The RUSLE model was used to calculate the sediment yield on the slope, and the SDR is quantified by the ratio of sediment load in the channel to the sediment yield on the slope.New hydrological insights for the region: Under climate change, the reduced annual rainfall caused a significant decrease in annual runoff and sediment load in the Longchuan River Basin (LRB), since 2003. The RUSLE model was used to calculate the sediment yield on the slope in LRB, and the sediment delivery ratio (SDR) was calculated by the ratio of sediment load to sediment yield. We found a new approach relevant to the relationship of SDR with annual runoff and sediment yield, which can indicate the response mechanism of SDR to climate change. In anthropogenic activities, reservoir interception is the main reason for the sediment load reduction, instead of the land use and land cover change. With a large reservoir built in the LRB, the average SDR is reduced by 83.04 % and the average trap efficiency of the reservoir is 0.96, which was calculated by the Brune equation. This study provides a feasible method to evaluate the effect of different factors on the runoff and sediment load change in the basin.