Dissolved solids and suspended sediment yields in the Rio Madeira basin, from the Bolivian Andes to the Amazon

The Rio Madeira is the main southern tributary of the Rio Amazonas, and the second Andean tributary of the Amazon drainage basin. Using Bolivian data from the PHICAB programme and Brazilian data from the DNAEE sediment measurement network, downstream trends in the dissolved solids and suspended sediment yields, from the Andes to the Rio Amazonas, have been investigated. The dissolved solids load (36 × 10⁶ t year^-1 at Villabella on the Bolivia-Brazil frontier) increases progressively from upstream to downstream, in line with the discharge. Sediment loads decrease from the piedmont to Villabella (250-300 × 10⁶ t year^-1) because substantial deposition occurs on the flood plain. The significant differences observed in Brazil are probably linked with the sediment load sampling technique and calculation method.