Abstract
Sediment flows dynamics (erosion, transport and deposition) have been
disrupted in South America (SA), a continent with the highest erosion
and sediment transport rates globally. However, the magnitude and
spatial distribution of the main drivers of changes have been poorly
identified and explored. Here, we performed simulations using a
hydrological-hydrodynamic-sediment model to comprehensively estimate the
spatial and temporal sediment changes and trends in SA from 1984 to
2019. We found that 51% of the main SA rivers experienced significant
changes in simulated sediment transport (QST) over this period, with
36% due to Amazon deforestation and river damming and 15% due to
precipitation changes. We also estimated a 10% reduction in the average
sediment delivery to the oceans. Deforestation was responsible for QST
changes above 80% in some Amazon sites, and hydropower expansion led to
a greater reduction of sediment flows (as high as 80-100%) in the
Tocantins, Uruguay, Upper Paraná, lower São Francisco, Desaguadero, and
Negro rivers. In addition, our results suggest that reservoirs built in
the Amazon region in the last decade are also affecting sediment
transport. Our modeling outputs provide unprecedented information about
the status of sediment dynamics in SA, and a means to develop
evidence-based strategies and transboundary policies related to
continental-wide sediment dynamics and the conservation and restoration
of ecosystems.