Índice de vegetação aplicado no mapeamento das macrófitas aquáticas do reservatório de ITAIPU

Abstract

Some species of macrophytes are favored by environmental changes or imbalances in the water body, causing some of them to form dense populations to the detriment of others, reducing biodiversity and causing problems for local water uses. Due to the importance of ecological studies applied to better understand the temporal dynamics of the community of aquatic macrophytes. The present work aims to analyze the distribution of the aquatic macrophytes of the ITAIPU reservoir, using Remote Sensing (SR) and geoprocessing techniques, using threshold values for the SWIR reflectance values and of the Normalized Difference Vegetation Index (NDVI) in a time series of Landsat 8 OLI sensor images. The mapping results showed an overall accuracy of 0.87 with Kappa indices around 0.73, considering the following classes and thresholds: water (NDVI <0.10 and SWIR <0,08); Only exposed (0.10 ≤ NDVI <0.20); Macrophytes A (0.20 ≤ NDVI <0.75); (Macrophytes B NDVI ≥ 0.75). The macrophytes presented smaller area of occurrence in the presence of water levels above 220 m (34.28 km²). On the contrary, in the presence of lower levels, the occurrence of the same in an area of 126.47 km² was detected. In this way, it was concluded that the techniques of SR and geoprocessing, used, have proved to be an effective tool in the mapping of macrophytes capable of assisting in the management of local biodiversity.