Spatio-temporal variation of aquatic macrophyte cover in a reservoir using Landsat images and Google Earth Engine

Abstract

The presence of large amounts of aquatic macrophytes in reservoirs can trigger several impacts on the local ecosystem and conventional methodologies used for their monitoring only returns information from the present moment. With that in mind, this study aimed to map spatio-temporal variation of macrophyte cover using Landsat 5, 7 and 8 images between 1984-2021 at Jupiá reservoir, in south east of Brazil, besides determining curves and maps of macrophyte cover permanence. The identification of these organisms in the images, and their distinction from other vegetations, was made through spectral indices (NDVI, GNDVI and GSAVI) and the determination of the characteristic range of each of these classes, which was given by probability distributions. Interannual variations were observed in the spatial arrangement of macrophytes and the area’s growth trend, possibly being caused by the implantation of an upstream reservoir. Although the number of images without interference was a limitation, the construction of a historical series of macrophytes occupation and the determination of permanence curves and maps proved to be satisfactory and could help on the decision-making processes for the management of these organisms.