Sediment Transfer through the Fluvial System (Proceedings of a symposium held in Moscow, August 2004). IAHS Publ. 288, 2004, 220–225

1 HYBAM (UR154 LMTG), IRD - BP 64 501, F-34394 Montpellier Cedex 5, France

2 INAMHI –700 Iñaquito y Correa, Quito, Ecuador

3 HYBAM (UR154 LMTG), IRD – Casilla 18 1209, Lima18, Peru

Abstract This paper presents the first results obtained by the HYBAM project in the Napo River drainage basin in Ecuador during the period 2001–2002. Three gauging stations were installed in the basin to monitor suspended sediment yields, of which two are located in the Andean foothills and the third station on the Ecuador–Peru border in the Amazonian plain. At the confluence of the Coca and Napo rivers, the suspended sediment yield transported from the Andes Mountains is 13.6 10⁶ t year^-1 (766 t km^-2 year^-1). At the Nuevo Rocafuerte station 210 km downstream, the suspended sediment yield reaches 24.2 10⁶ t year^-1 for an annual mean discharge of 2000 m³ s^-1. These values indicate intensive erosion processes in the Napo Andean foreland basin between the Andean foothills and the Nuevo Rocafuerte station, estimated to be 900 t km^-2 year^-1. These high rates of erosion are the result of the geodynamic uplift of the foreland.

Keywords Amazon Basin; Andes; Ecuador; erosion; hydrology; Napo River; suspended sediment