Sensoriamento remoto aplicado à avaliação da qualidade da água do reservatório Edson Queiroz, Ceará

Abstract

Continuous monitoring of water quality parameter concentrations is essential for proper water resource management. Many techniques are applied to assist reservoir assessment processes, such as remote sensing and GIS. Among the water quality parameters that can be assessed by remote sensing, Chlorophyll-a stands out, a pigment present in photosynthetic organisms and responsible for the apparent color of water. This study aimed to apply remote sensing techniques to estimate the concentration of Chlorophyll-a in the Edson Queiroz reservoir, located in Santa Quitéria, Ceará. The study period of the research corresponds to the years between 2014 and 2022, and the parameter estimates were made with images from the Landsat 8-OLI satellite corresponding to the period. For image processing, the QGIS software version 3.28 with the Semi-Automatic Classification (SCP) add-on was used. In this sense, 10 algorithms of 5 spectral bands of the OLI sensor were applied. The correlation between the predicted concentration of Chlorophyll-a on the date of capture of the scenes and the average values of spectral reflectance obtained through the algorithms was performed. Thus, through data adjustment, the variables with potential for recovery of the parameter were selected, in this case, 7-band models. The equations generated from the model were applied to recover Chlorophylla using spectral reflectance as an independent variable of the equation. The ratio of the B5/B6 bands, Near Infrared - NIR and Mid Infrared - SWIR 1, respectively, proved to be the variable with the best adjustment of the data for recovery of Chlorophyll-a, with R² = 0.9976. Thus, the study highlighted the potential of applying remote sensing techniques to predict the concentration of the analyzed parameter and its temporais and spatial variations, fundamental for the management of water bodies.