Avaliação do desenvolvimento da vegetação aquática submersa em reservatório por meio da profundidade do disco de Secchi estimada com imagem SPOT-6

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The aquatic macrophytes are among the primary producers in artificial reservoirs and can be classified into four groups: rooted, floating, emergent and submerged. The radiation availability is the main limiting factor in the growth of submerged macrophytes (or submerged aquatic vegetation - SAV). The Secchi depth (SD) is a fundamental variable in limnological studies, and it is an indicator of water transparency. The water transparency is directly related to radiation availability; hence the SD is useful in SAV studies. Therefore, the goals of this study were to estimate the SD using SPOT-6 image and evaluate the development of SAV based on the SD estimated by remote sensing. The study area was a section of the Nova Avanhandava Reservoir, which belongs to the reservoirs cascade of the Tietê River - São Paulo, Brazil. The regression between the centered band at 660 nm and the SD resulted in a R² = 0.73 and a NRMSE = 21.5%. The SD map was made using the atmospherically corrected SPOT-6 image and the calibrated SD prediction model. Two regions with different SD (Class 0.0 - 1.0 m and Class > 5.0 m) were selected to evaluate the SAV height. Therefore, it was observed that under different SD conditions there is a change in both maximum height reached by the SAV and the depth of its occurrence.