Detection and delimitation of small reservoirs in the Cachoeira River Watershed, Bahia, using multispectral images

Abstract

This work used multispectral images from the Sentinel-2 satellite of the Cachoeira River Watershed, in the south of Bahia state. This paper aim to detect, delimit and quantify the area occupied by water reservoirs at Cachoeira River Watershed. For this purpose, the MNDWI (Water Index with Modified Normalized Difference) and NDWI (Water Index with Normalized Difference) indexes were calculated. The detection capability of small water bodies by the methods employed proved to be satisfactory, with a correspondence of up to 78% between the methods, with superior results for the MNDWI index compared to the NDWI. Through this methods a seasonal and spatial changes were observed in the distribution of reservoirs in the Cachoeira River Watershed. The southwestern portion of the basin showed a higher concentration of small reservoirs in the rainy season. In the general context of the hydrographic basin, water reservoirs occupy up to 0.13% of the basin area, while in the southwestern areas of Cachoeira River Watershed this value reaches up to 0.86% of the area occupied by reservoirs.