Estimation of Suspended Sediment Concentration in the Middle Negro River (Amazon Basin) using the MODIS sensor

Abstract

Suspended sediment concentration (SSC) plays a fundamental role in the hydrological and geomorphological processes of large tropical rivers. However, SSC monitoring remains limited in the Amazon Basin, particularly in the Negro River, one of the largest rivers in the world. This study develops and validates an empirical model to estimate SSC in the middle Negro River (Amazon Basin) using MODIS surface reflectance data and in situ measurements and proposes a long-term reconstruction of SSC for the region. The results indicate that the Ordinary Least Squares (OLS) regression model presented the best statistical performance. The reconstructed time series from 2003 to 2024 revealed a low average SSC (~5 mg L⁻¹) and a statistically significant negative trend (−0.0536 mg L⁻¹ year⁻¹). The results demonstrate that MODIS data can be successfully applied to SSC monitoring in blackwater rivers despite spectral limitations. The study indicates that, despite the negative trend associated with low SSC availability and current geomorphological dynamics, the middle Negro River remains stable. This study contributes to advancing the application of remote sensing in optically complex environments and to improving the understanding of geomorphological processes in large tropical rivers dominated by sediment limitations.