Brasil and Bolivia have water plans projects on the Beni-Madeira river, a major tributary of the Amazon. There are four
main tributaries to the Rio Madeira: the Guapore, the Mamore and the Beni rivers into the Bolivian territory, and the
Madre de Dios River crossing the North of Bolivia, coming from Peru. Most parts of these rivers are very far from the
Andean capital cities of Bolivia and Peru, unreachable for long periods of time. Very few gauging stations are in
operation, either for the Bolivian or the Peruvian part, most of them being located at the Andes piedmont or near the
confluence at the Brazilian border as they form the Madeira river. This situation is exemplary of large transboundary
basins in the tropical part of the world.
We have computed 39 water level time series using ENVISAT altimetry data over the four tributaries of the Madeira and
the Madeira itself. We present a preliminary study mostly conducted onto the Guapore river, in order to assess the quality
of these time series for a variety of situations, but mostly narrow and meandering riverbeds. Comparison between water
levels variation in the mainstream and within the inundations plains and lakes are drawn. We conclude by the
perspectives offered by the combined use of radar altimetry and SAR imagery for the global monitoring of water
resources, in large tropical transboundary basins.