Re-parametrization of a Quasi-Analytical Algorithm (QAA) to estimating the inherent optical properties in reservoirs of Tietê River

Abstract

Reservoirs are artificial aquatic ecosystems that modify the hydrodynamics of rivers. The increased retention time and, consequently, elevation of the nutrients availability time lead to eutrophication of the environment and blooms of algae (phytoplankton). Some species of phytoplankton may produce toxic metabolites for animals and humans. Therefore, the monitoring of water bodies has environmental and health importance for the management of water resources. The reservoirs have large areas that hamper the monitoring of water quality through traditional methods such as collection of punctual water samples. Thus, the use of remote sensing data can be useful to assess the quality of water in terms of active optically constituents, i.e., that interact with electromagnetic radiation. Remote sensing of water color aims retrieve the concentration of active optically constituents that modify the optical properties inherent in water, responsible for the change in color of the water. Several models have been developed to estimate the active optically components from remote sensing data. These models have used empirical, semi-analytical and quasi-analytic approaches. Empirical models involve statistical adjustments and are not based on physical fundamentals. On the other hand, the semi-analytical models are based on solutions for the radiative transfer equation. The quasi-analytical algorithms derive the inherent optical properties from remote sensing reflectance measurements. Thus, the objective of the proposed project is to parameterize and calibrate models based on radiative transfer equation to estimate the concentration of chlorophyll-a in a highly productive tropical reservoir. The work will be conducted in Barra Bonita Reservoir, located in the middle course of the Tiete River, State of Sao Paulo. The Barra Bonita reservoir is classified as eutrophic and presents cyanobacteria blooms. Tiete River is one of the most important rivers of the State of São Paulo and has great environmental and economic importance. However, its potential for human use is limited due to poor quality of the water in certain regions. From the proposed work is expected to obtain suitable models for estimating the concentration of chlorophyll-a. In addition, it is expected that the study will contribute to the use of technology to estimate water quality and assist in managing water resources. (AU)