Satellite-Observed Spatiotemporal Variations of Suspended Sediment Concentration in the Yellow River over the Past 40 Years: A Recent Shift in the Long-Term Decreasing Trend

The Yellow River (YR) is one of the rivers with the highest suspended sediment concentrations (SSCs) globally. Recent years have seen a notable decline in SSC in the YR, driven by climate change and human activities. However, the limited data from hydrological stations are insufficient to thoroughly characterize the spatiotemporal variations of SSC along the river. To address this issue, this study developed a novel piecewise SSC retrieval algorithm applicable to Landsat series satellite imagery. Based on the algorithm, SSC maps for the YR from 1986 to 2023 were generated, and the spatiotemporal changes, as well as the primary influencing factors, were analyzed. The SSC spatial distribution of the YR is notably characterized by increasing turbidity from the upper reaches to the estuary, with abrupt decreases and increases in SSC observed in certain river segments, related respectively to large reservoirs and major tributary inflows. Interannual variations in SSC reveal 3 distinct phases: a continuous increase from 1986 to 1997, a significant decrease from 1997 to 2016, and a fluctuating trend since 2016. The analysis of influencing factors attributes the temporal changes in SSC primarily to sediment retention by reservoirs, vegetation stabilization of sediment, and sediment trapping by check dams. This study provides comprehensive spatiotemporal characterization of SSC along the entire YR over nearly 40 years and reveals a recent shift in the long-term decreasing trend since 2016. These findings offer valuable scientific insights for the management of the YR basin.