Using satellite altimeter radar technology for monitoring changes in water levels at continental scale is a relatively recent advance. Several studies have demonstrated the interest being shown in applying this technology to monitoring the hydrographic patterns of large-scale basins worldwide. The current study presents the inference of time series representing changes in water level for bodies of water by defining virtual gauge stations deduced for two very different rivers in terms of their biophysical and topographic characteristics; the two rivers were the Rio Negro in the Brazilian Amazon Basin and the Caqueta River on the Colombian side. The differences between the two rivers revealed the limits of satellite radar altimeter when applied to continental waters (±20cm and ±40 cm precision for Rio Negro and Rio Caqueta, respectively). However, applying this technology seems very promising, since new missions have been scheduled to be put into orbit by the end of 2008.