Temporal analysis of the change in vegetation cover around the UHE Coaracy Nunes – Amapá

Abstract

The construction of dams became necessary for national development, in wich the Amazon region, due to its great hydro-energy potential, became the country's hydroelectric frontier. The oldest region reservoir is the UHE Coaracy Nunes-Amapá, built in 1960 and operating since 1975. However, its construction generated several problems, such as loss of territoriality, difficulties in the subsistence of villages and modification of the environment. Therefore, understanding the changes that have occurred in the environment becomes relevant to knowledge, to enable recovery, preservation, conservation and local monitoring actions. In this way, the present study sought to understand if there were changes in the vegetation cover around the UHE Coaracy Nunes from 2000 to 2020. For this, remote sensing data were used. Eleven images obtained from the TM/Landsat-5, ETM+/Landsat 7 and OLI/Landsat-8 satellites were utilized, delimiting the study area with the creation of a polygon (buffer) around the UHE. Digital processing techniques were applied to these images with the support of pixel counting software. The Normalized Difference Vegetation Index (NDVI) was calculated, making it possible to obtain the median. The results obtained demonstrate that the image processing allowed to differentiate its constituent elements (plant cover, exposed soil and water body). The calculation of NDVI medians, for scenes between the years 2000 to 2020, ranged from 0,27 to 0,53 (mean of 0,43 ± 0,09), thus, the statistical analysis showed no relationship over the years (F1,9 = 2,31 and P = 0,16), indicating that during the analyzed period there were no changes in vegetation cover on the ground. This stability may be due to the stagnation of population growth in the city, as well as the presence of the Seringal Triunfo Natural Heritage Private Reserve within the selected area. Another factor that can be attributed to this stability is the pixel count, as the surface of water bodies was not removed. However, the use of Landast satellite images, temporal sequence and the NDVI index proved to be effective tools in remote sensing, enabling the understanding of the dynamics of vegetation cover around the UHE Coaracy Nunes, thus showing its stability in the analyzed period.