A single semi-analytical algorithm to retrieve chlorophyll-a concentration in oligo-to-hypereutrophic waters of a tropical reservoir cascade

Previous studies have shown the challenges in using a single model to estimate chlorophyll-a concentration (Chl-a) in water bodies with widely differing characteristics. A single model based on remote sensing to map the Chl-a distribution across the entire Tietê River Cascade System (TRCS) serves as...

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Autores principales:	Luiz Rotta, Enner Alcântara, Edward Park, Nariane Bernardo, Fernanda Watanabe
Formato:	article
Lenguaje:	EN
Publicado:	Elsevier 2021
Materias:	OLI/Landsat-8 Tietê River Cascade System Trophic state Quasi-Analytical Algorithm Absorption coefficient Ecology QH540-549.5
Acceso en línea:	https://doaj.org/article/b7f1b0c777684ae4892f9cd823451a95
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spelling	oai:doaj.org-article:b7f1b0c777684ae4892f9cd823451a952021-12-01T04:29:01ZA single semi-analytical algorithm to retrieve chlorophyll-a concentration in oligo-to-hypereutrophic waters of a tropical reservoir cascade1470-160X10.1016/j.ecolind.2020.106913https://doaj.org/article/b7f1b0c777684ae4892f9cd823451a952021-01-01T00:00:00Zhttp://www.sciencedirect.com/science/article/pii/S1470160X20308529https://doaj.org/toc/1470-160XPrevious studies have shown the challenges in using a single model to estimate chlorophyll-a concentration (Chl-a) in water bodies with widely differing characteristics. A single model based on remote sensing to map the Chl-a distribution across the entire Tietê River Cascade System (TRCS) serves as a cost and time-efficient alternative to the conventional monitoring by providing trophic status over space and time. The Tietê River contains one of the largest cascade reservoir systems in the world, which sustains important ecological and socio-economic activities in the São Paulo State, Brazil. Surplus nutrients in water draining its surrounding catchments have been the main cause of eutrophication in the reservoirs of the TRCS. To assess the trophic state of the reservoirs, Chl-a has been regularly monitored by sampling points. However, they are limited by operational costs and dependent on weather conditions. Moreover, the current sampling method only produces point-based measurements. In this paper, we calibrate remote sensing images based on the absorption coefficient to map the spatial distribution patterns of Chl-a levels in the reservoirs. Mapping is done by estimating the Chl-a concentration. The absorption coefficients were retrieved from OLI/Landsat images using the Quasi-Analytical Algorithm (QAA). The total absorption (at) in 482 nm and 655 nm retrieved by QAA presented NRMSE of 17% and 18.5%, respectively. Both at (482 and 655 nm) were used in the model calibration and presented a satisfactory result covering all data ranges, with R2 of 0.646 and NRMSE of 15.3%. The proposed model in this study to retrieve Chl-a maps with relatively high accuracy can be incorporated into the operational monitoring system of the TRCS at a low cost that can provide timely information for reservoir managers to carry out necessary actions. This may include mitigating environmental impacts caused by sudden algae blooms.Luiz RottaEnner AlcântaraEdward ParkNariane BernardoFernanda WatanabeElsevierarticleOLI/Landsat-8Tietê River Cascade SystemTrophic stateQuasi-Analytical AlgorithmAbsorption coefficientEcologyQH540-549.5ENEcological Indicators, Vol 120, Iss , Pp 106913- (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	OLI/Landsat-8 Tietê River Cascade System Trophic state Quasi-Analytical Algorithm Absorption coefficient Ecology QH540-549.5
spellingShingle	OLI/Landsat-8 Tietê River Cascade System Trophic state Quasi-Analytical Algorithm Absorption coefficient Ecology QH540-549.5 Luiz Rotta Enner Alcântara Edward Park Nariane Bernardo Fernanda Watanabe A single semi-analytical algorithm to retrieve chlorophyll-a concentration in oligo-to-hypereutrophic waters of a tropical reservoir cascade
description	Previous studies have shown the challenges in using a single model to estimate chlorophyll-a concentration (Chl-a) in water bodies with widely differing characteristics. A single model based on remote sensing to map the Chl-a distribution across the entire Tietê River Cascade System (TRCS) serves as a cost and time-efficient alternative to the conventional monitoring by providing trophic status over space and time. The Tietê River contains one of the largest cascade reservoir systems in the world, which sustains important ecological and socio-economic activities in the São Paulo State, Brazil. Surplus nutrients in water draining its surrounding catchments have been the main cause of eutrophication in the reservoirs of the TRCS. To assess the trophic state of the reservoirs, Chl-a has been regularly monitored by sampling points. However, they are limited by operational costs and dependent on weather conditions. Moreover, the current sampling method only produces point-based measurements. In this paper, we calibrate remote sensing images based on the absorption coefficient to map the spatial distribution patterns of Chl-a levels in the reservoirs. Mapping is done by estimating the Chl-a concentration. The absorption coefficients were retrieved from OLI/Landsat images using the Quasi-Analytical Algorithm (QAA). The total absorption (at) in 482 nm and 655 nm retrieved by QAA presented NRMSE of 17% and 18.5%, respectively. Both at (482 and 655 nm) were used in the model calibration and presented a satisfactory result covering all data ranges, with R2 of 0.646 and NRMSE of 15.3%. The proposed model in this study to retrieve Chl-a maps with relatively high accuracy can be incorporated into the operational monitoring system of the TRCS at a low cost that can provide timely information for reservoir managers to carry out necessary actions. This may include mitigating environmental impacts caused by sudden algae blooms.
format	article
author	Luiz Rotta Enner Alcântara Edward Park Nariane Bernardo Fernanda Watanabe
author_facet	Luiz Rotta Enner Alcântara Edward Park Nariane Bernardo Fernanda Watanabe
author_sort	Luiz Rotta
title	A single semi-analytical algorithm to retrieve chlorophyll-a concentration in oligo-to-hypereutrophic waters of a tropical reservoir cascade
title_short	A single semi-analytical algorithm to retrieve chlorophyll-a concentration in oligo-to-hypereutrophic waters of a tropical reservoir cascade
title_full	A single semi-analytical algorithm to retrieve chlorophyll-a concentration in oligo-to-hypereutrophic waters of a tropical reservoir cascade
title_fullStr	A single semi-analytical algorithm to retrieve chlorophyll-a concentration in oligo-to-hypereutrophic waters of a tropical reservoir cascade
title_full_unstemmed	A single semi-analytical algorithm to retrieve chlorophyll-a concentration in oligo-to-hypereutrophic waters of a tropical reservoir cascade
title_sort	single semi-analytical algorithm to retrieve chlorophyll-a concentration in oligo-to-hypereutrophic waters of a tropical reservoir cascade
publisher	Elsevier
publishDate	2021
url	https://doaj.org/article/b7f1b0c777684ae4892f9cd823451a95
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A single semi-analytical algorithm to retrieve chlorophyll-a concentration in oligo-to-hypereutrophic waters of a tropical reservoir cascade

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