Modification of the Madeira River morphology following large hydropower projects detected by satellite data

Le résumé fourni par la source

Abstract Estimating suspended sediment concentration (SSC) in river channels is essential for understanding hydro‐sedimentological processes, managing water quality, and conserving aquatic ecosystems. This study evaluated different empirical equations to estimate SSC in the lower Madeira River and analyzed its hydro‐sedimentary dynamics based on MODIS Terra/Aqua sensor images. The equations were validated with in situ data, and continuous SSC time series were then estimated at three stations along the lower Madeira River between 2003 and 2025. The results demonstrate that equations based on the spectral ratio between NIR and RED bands consistently outperformed single‐band formulations. Temporal analysis revealed a statistically significant reduction in SSC in the reaches immediately downstream of the Madeira River Hydroelectric Complex (MHC) after the start of its full operation in 2015, with decreases of approximately 29% at the Porto Velho station and 10% at the Fazenda Vista Alegre station. In contrast, no significant trend was identified at the Urucurituba station, near the confluence with the Amazon River. The decrease in SSC due to dams was associated with the intensification of erosive processes in the reaches immediately downstream of the MHC, while the region between Fazenda Vista Alegre and Urucurituba showed an increase in the deposition process for suspended sediment after 2015, possibly due to increased upstream erosion, the Amazon River backwater effect, and climate change, which has increased the frequency of extreme hydrological events.

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