Estimation of Suspended Sediment Concentration in the Yangtze Main Stream Based on Sentinel-2 MSI Data

Suspended sediment concentration (SSC) is an important indicator of water quality that affects the biological processes river ecosystems and evolution floodplains channels. The in situ SSC measurements are costly, laborious spatially discontinuous, while spaceborne overcome these drawbacks becomes effective supplement for observation. However, observations rivers more challenging than those lakes reservoirs due to their narrow widths broad range SSCs, among other factors. We developed a novel retrieval method suitable rivers. Water was classified as clear or turbid based on Forel–Ule index, optimal models were constructed spectral responses SSCs cases different turbidity. estimated had strong correspondence with measurements, root mean squared error (RMSE) 24.87 mg/L relative (MRE) 51.91%. Satellite-derived showed good consistency obtained from gauging stations (r2 > 0.79). studied spatiotemporal variation Yangtze main stream 2017 2021. It increased considerably May October each year, peak generally occurring July August (ca. 200–300 normal year 800–1000 flood year), it remained stable decreased around 50 November April following year. high east low west, local maxima Chongqing 80–150 mg/L) lower Dongting Lake reaches 80–100 minima downstream Three Gorges Dam 1–20 mg/L). Case studies Yibin reach Reservoir determined special hydrodynamic conditions anthropogenic activities. procedure applied process Sentinel-2 imagery we deficiencies retrieval.