The study was conducted in order to calculate the flow of carboncarried by the Las Piedras river watershed, typical and representative of the South American tropical Andes, strategic reservoir of the hydrological resource. An observational research was performed over 20 months on the hydrological resource by means of a completely random design, stratified by altitude (masl), analyzing the TOC content, the physicochemical properties of the water and hydro-meteorological variables (discharge and seasonal variation). The average concentration of TOC mainly contributed from the high zone was 9 mg.L-1. A TOC flow of 2003.5 Kg.day-1 associated with the discharge and the humid seasonality is carried in average.The analysis related to physicochemical variables allows concluding that the river dissolves CO2 in its waters. This study supplements the behavioral analysis of the Andean rivers and their contribution to the global carbon cycle.