The Rio Desaguadero is the outlet of Lake Titicaca and flows into Lake Poopo in the endorheic watershed of the Altiplano in Bolivia (alt. 3650 m); its main tributary is the Rio Mauri. Preliminary data lead to hypotheses which consider the Rio Desaguadero as a very particular hydrosystem in organic carbon transport. If most of the particulate carbon comes from margins, the necessity for maintaining interconnexions between the main channel and the wetlands in future regulation projects must be emphasized. -from English summary