Few works deal with the use of satellite data to monitor water quality of the Amazonian water bodies, in particular because of the unavailability of appropriated remote sensing sensors and of the dramatic lack of in situ measurements. In these heterogeneous and fast-changing environments, the challenge is to retrieve the parameters of interest when the water optical properties are affected at the same time by the presence of phytoplancton, dissolved organic components and mineral suspended matter. Sensors such as MODIS and MERIS, by joining fine spectral resolution (15 bands for MERIS), high temporal resolution (2 images each day for MODIS) and medium spatial resolution (250 to 500 meters) appear promising.
In this study, we assess the use of MODIS and MERIS data for the monitoring of both Amazonian floodplain lakes and the largest river mainstreams. Making use of a large dataset of water quality measurements we analyzed the spatial and temporal variations of the water signatures in a large floodplain. MERIS allows to identify main water constituents and to retrieve the chlorophyll-a and total suspended solids (TSS) concentrations during the main lake stages. Comparisons of MODIS data with TSS measurements collected every 10 days on the main rivers prove that such sensor allows to finely monitor the surface sediment fluxes. Accuracy of the TSS retrieval using semi-analytical techniques ranges between 5 and 17 mg/l (relative accuracy of about 25 %). We discuss the complementarity of both sensors and the progress made in relation to classical studies based on Landsat data.
Submetido por Jean-Michel Martinez em 11-MAR-2004
Tema Científico do LBA: SH (Hidrologia e Química das Águas)