The objective of this paper is to analyze the spatial and temporal variabilities of the water signatures as a function of sediment concentration at the surface. Images acquired simultaneously with 3 campaigns of water measurements, conducted from high water stage to low water stages, are analyzed and discussed. The potential of ETM+ and MODIS for sediment retrieval appears clearly, especially in the red bands, for concentrations in the range of 0 to 100 mg/l, commonly encountered during most of the hydrological cycle. First retrieval attempts give RMSE errors of about 10 mg/l. We show also that phytoplancton blooms, occurring over large areas during decreasing water levels, alter especially ETM+ and should be first detected to separate them from the rest of the retrieval. These results show that Landsat and especially MODIS, because of his higher revisit frequency, are very promising for surface sediment retrieval over the large lakes of the Amazon floodplain.