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ARTICLES • Rev. Ambient. Água 15 (2) • 2020 • https://doi.org/10.4136/ambi-agua.2488   copy

Retrieval and mapping of chlorophyll-a concentration from Sentinel-2 images in an urban river in the semiarid region of Brazil

Recuperação e mapeamento da concentração de clorofila-a a partir de imagens do Sentinel-2 em um rio urbano na região semiárida do Brasil

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

Recently, the Poti river mouth region has experienced environmental impacts that resulted in a change of landscape in its dry season, highlighting the eutrophication and proliferation of phytoplankton, algae, cyanobacteria and aquatic plants. Considering the aspects related to water-quality monitoring in the semiarid region of Brazil from remote sensing, this study aimed to evaluate the performance of Sentinel-2A satellite data in the retrieval of chlorophyll-a concentration in Poti River in Teresina, Piaui, Brazil. The chlorophyll-a concentration retrieval and mapping methodology involved the study of the water surface reflectance in Sentinel-2A images and their correlation with the chlorophyll-a data collected in situ during the years 2016 and 2017. The results generated by the Chl-1, Ha et al. (2017)HA, N. T. T.; THAO, N. T. P.; KOIKE, K.; NHUAN, M. T. Selecting the best band ratio to estimate chlorophyll-a concentration in a tropical freshwater lake using Sentinel 2A images from a case study of lake Ba Be (Northern Vietnam). International Journal of Geo-Information, v. 6, p. 290, 2017. https://doi.org/10.3390/ijgi6090290
https://doi.org/10.3390/ijgi6090290... , Chl-2, Page et al. (2018)PAGE, B. P.; KUMAR, A.; MISHRA, D. R. A novel cross-satellite based assessment of the spatio-temporal development of a cyanobacterial harmful algal bloom. International Journal of Applied Earth Observation and Geoinformation, v. 66, p. 69-81, 2018. https://doi.org/10.1016/j.jag.2017.11.003
https://doi.org/10.1016/j.jag.2017.11.00... , and Chl-3, Kuhn et al. (2019)KUHN, C.; VALERIO, A. M.; WARD, N.; LOKEN, L.; SAWAKUCHI, H. O.; KAMPEL, M.; RICHEY, J.; STADLER, P.; CRAWFORD, J.; STRIEGL, R.; VERMOTE, E.; PAHLEVAN, N.; BUTMAN, D. Performance of Landsat-8 and Sentinel-2 surface reflectance products for river remote sensing retrievals of chlorophyll-a and turbidity. Remote Sensing of Environment, v. 224, p. 104-118, 2019. https://doi.org/10.1016/j.rse.2019.01.023
https://doi.org/10.1016/j.rse.2019.01.02... equations show the need for calibrating the algorithms used for the Poti River water components. However, the empirical algorithm Chl-2 shows a correlation has been established to identify the spatiotemporal variation of chlorophyll-a concentration along the Poti River broadly and not punctually. The spatial distribution of this pigment in maps derived from Sentinel-2A is consistent with the pattern of occurrence determined by the in situ data. Therefore, the MSI sensor proved to be a tool suitable for the retrieval and monitoring of chlorophyll-a concentration along the Poti River.

Keywords:
Poti river; remote sensing; water quality

Instituto de Pesquisas Ambientais em Bacias Hidrográficas Instituto de Pesquisas Ambientais em Bacias Hidrográficas (IPABHi), Estrada Mun. Dr. José Luis Cembranelli, 5000, Taubaté, SP, Brasil, CEP 12081-010 - Taubaté - SP - Brazil
E-mail: ambi.agua@gmail.com
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