Estimation of Submerged Aquatic Vegetation Height and Distribution in Nova Avanhandava Reservoir (São Paulo State, Brazil) Using Bio-Optical Modeling

Abstract

Semi-analytical models have been developed to remove the water column influence and then retrieve the bottom reflectance in water bodies in order to study submerged targets. However, the majority of these models were elaborated for oceanic and coastal waters, in other words, there are still limited studies about the retrieval of the bottom response from remote sensing in continental aquatic environments. The reason for that is the complexity of those environments as they present high concentrations of dissolved and suspended constituents, which make it difficult to detect the bottom signal. The objectives of this thesis were: to assess the availability of sub-aquatic radiation in the water column and the total suspended solids concentration (TSS) in the Nova Avanhandava reservoir in order to analyze their influence on the SAV (Submerged Aquatic Vegetation) development; to recover the bottom albedo and generate bio-optical models to estimate the aquatic submerged vegetation height and position in the Nova Avanhandava reservoir; and finally, to use and assess the bio-optical models performance by using multi-spectral imagery (SPOT-6). Hyperspectral data were collected by using the radiometer RAMSES - TriOS. It was found that studies on subaquatic radiation availability measured by the vertical attenuation of downwelling irradiance in the water column can aid in understanding SAV behaviour in tropical reservoirs and, therefore, contribute to its management. SPOT-6 image, acquired on July the 9th of 2013, was atmospherically corrected by the empirical line method...

Modelos semi-analíticos vêm sendo desenvolvidos para remover a influência da coluna da água e, com isso, recuperar a resposta do substrato em corpos águas, com o intuito de estudar alvos submersos. Porém, a maioria desses modelos foram elaborados para águas oceânicas e costeiras, ou seja, ainda são limitados os estudos sobre a recuperação da resposta do substrato a partir de sensoriamento remoto em ambientes aquáticos continentais devido à complexidade desses ambientes, pois apresentam altas concentrações de constituintes suspensos e dissolvidos da água, o que dificulta a detecção do sinal do substrato. Os objetivos do trabalho foram: avaliar a disponibilidade de radiação subaquática na coluna de água e o total de sólidos suspensos (TSS) no Reservatório de Nova Avanhandava, para analisar sua influência no desenvolvimento da VAS (Vegetação Aquática Submersa); recuperar a resposta do substrato e gerar modelos bio-ópticos para estimar a altura e posição da vegetação aquática submersa no reservatório de Nova Avanhandava; e finalmente utilizar e avaliar o desempenho dos modelos bio-ópticos por meio de imagem multiespectral (SPOT-6)....