The spatiotemporal variations in suspended sediment concentration (SSC) in the lower reaches of the Yellow River exhibit significant variability and are influenced by reservoir operations. Understanding the spatiotemporal distribution characteristics of SSC in water holds crucial implications for environmental protection and reservoir operation management. Based on daily-scale SSC monitoring data from four hydrological stations in the lower Yellow River, this study established an SSC remote sensing model applicable to Landsat series satellite data. The independent variable of the model, Rrs(NIR)/(Rrs(G) + Rrs(R) + Rrs(SWIR)), demonstrated sensitivity to water bodies with different SSC values. Distinctive spatiotemporal characteristics in sediment transport were observed across the lower Yellow River. Spatially, the SSC values in the Sanmenxia and Xiaolangdi reservoirs were notably lower than those in other river sections, averaging 1008.42 ± 602.83 mg/L and 1177.89 ± 627.95 mg/L, respectively. Over time, the majority of the river sections (96%) exhibited decreasing trends in SSC during 1984–2022, particularly in the downstream Xiaolangdi reservoir, with average SSC values of 4265.58 ± 1101.77 mg/L in the 1980s and 1840.80 ± 2255.15 mg/L in the 2020s. Seasonal variations in SSC were prominent, with higher summer concentrations, averaging 5536.43 ± 2188.77 mg/L (2020s summer) and 814.11 ± 158.27 mg/L (2020s winter). Reductions in SSC during 1984–2022 primarily occurred in summer, weakening its seasonal variability in the lower Yellow River. Water discharge emerged as a critical factor influencing suspended sediment transport, with SSC increasing in high-water-flow months. Following the construction of the Xiaolangdi reservoir, the relationship between SSC and water discharge at different stations underwent notable alterations. This study enhances our understanding of the spatiotemporal dynamics of suspended sediment transport in the lower Yellow River, providing valuable insights for utilizing long-term Landsat series data in the dynamic monitoring of river sediment transport.

The study of river sediment is a broad and complex field. One of the very important parameters is suspended particle size (SPS), which is indispensable for understanding water–sediment dynamics. As one of the most serious soil erosion areas in the world, the Loess Plateau delivers a large amount of sediment to the Yellow River and its numerous tributaries. Studies on riverine SPS in the Loess Plateau have received extensive attention. In this study, we investigate the spatiotemporal variations of SPS in the Loess Plateau rivers and analyze the driving factors along with their relative importance. Through the analysis of SPS data from 62 hydrological stations, the results indicated the spatial distribution of SPS was similar in the 1980s and 2010s, with both coarser particles mainly distributed in the northern rivers and finer particles mainly distributed in the southern rivers. During the 1980s to the 2010s, the mean SPS on the Loess Plateau decreased from 33 μm to 20 μm, with mean reductions of 42.0%, 29.4%, 46.3%, and 36.8% in the northern, western, southwestern, and southeastern basins, respectively. The most significant changes in SPS were observed in the Kuye, Wuding and Jalu River basins in the northern region, with decreases ranging from 27 to 73 μm. In the 1980s, topography (slope) and human management, followed by precipitation, were the key factors affecting SPS variability, contributing 25.7%, 25.9% and 24.0%, respectively. In the 2010s, the explanatory power of topographic slope on SPS variability declined by 16.6%, and other natural factors no longer significantly influenced SPS variability. The results of this study can serve as a reference for integrated basin management and sustainable ecosystem development in river catchments around the world.