Causes and consequences of seasonal changes in the water flow of the São Francisco river in the semiarid of Brazil

• Published in: Environmental and sustainability indicators Vol. 8; p. 100084
• Main Authors: Santos, Anderson dos, Oliveira Lopes, Pabricio Marcos, Silva, Marcos Vinícius da, Maniçoba da Rosa Ferraz Jardim, Alexandre, Barbosa de Albuquerque Moura, Geber, Siqueira Tavares Fernandes, Gabriel, Oliveira Silva, Douglas Alberto de, Bezerra da Silva, John Lennon, de Moraes Rodrigues, Joez André, Araújo Silva, Emanuel, Oliveira-Júnior, José Francisco de
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01-12-2020; Elsevier
• Subjects: Environmental degradation; Erosion; Landsat; Multivariate analysis; Remote sensing; Vegetation index; Vegetation index; Multivariate analysis; Environmental degradation; Remote sensing; Landsat; Erosion
• ISSN: 2665-9727; 2665-9727
• DOI: 10.1016/j.indic.2020.100084

The objective of this study was to evaluate the causes and consequences of changes in the water flow of the São Francisco River, on the border between the states of Sergipe and Alagoas, a Brazilian semiarid region. For this, we used images from the Landsat-8 satellite, OLI sensor, with a spatial resolution of 30 ​m. The results found in this study reveal two distinct behaviors in the study region of the Low São Francisco watershed, the first encompassing more homogeneous areas and with greater environmental preservation located in the West and the second encompassing heterogeneous areas with severe environmental degradation in the east of the study region. In general, due to the occurrence of exposed soil, thin vegetation, and regions of the high declivity, the basin has a high and very high degree of vulnerability in 73.8% of its land, with serious risks of desertification. According to the results of the Normalized Difference Water Index (NDWI), there was a drastic reduction in the surface area of water bodies along the São Francisco River channel, evidenced in the period from 2013 to 2018, with the expansion of sandbank areas in 17.7 ​km2. Agricultural and livestock activity was configured as an important factor in increasing land vulnerability. The evidence in this study suggests that changes in land use and coverage induce increases in the sandbank areas within the river channel, even in periods of greater water volume, which causes the silting up of the São Francisco river bed in its low course.
•There was a drastic reduction in the water area of the river.•Agriculture and Livestock activity was a major factor in increasing land vulnerability.•The vulnerability of the land directly impacts or the increase in sandbanks areas.