Análise temporal do uso e ocupação do solo na bacia hidrográfica da microrregião de Irecê-BA

Abstract

The Baixão de São Gabriel River Basin is a sub-basin of the Rio Verde that, in turn, flows into the São Francisco River. In the 1960s it was one of the main areas influenced by the Rural Credit Policy in which a good part of the Caatinga Biome was replaced by crops of corn, castor beans and mainly beans, which led the region to win the title of World Capital of Beans. Due to the non-conservationist planting system and human activities, the basin entered a process of environmental degradation, with suppression of riparian forests, silting of the bodies of water, loss of productivity, accelerated erosion processes, lowering of the water table and desertification. In this context, it is essential to study the use of land in the basin for the development of public policies aimed at environmental recovery and sustainable management of water resources. Thus, this study aimed to perform a temporal analysis of land use and cover between 1987 and 2018, using remote sensing techniques. Eight images from the Landsat satellites and results from the SRTM mission were used to delimit the study area, morphometric characterization, rainfall analysis, supervised classification and NDVI. It was identified that the Watershed of Riacho Baixão de São Gabriel, is spatially distributed over 11 municipalities, presents rivers of order 7, low susceptibility to flooding, predominantly smooth and smooth-undulating relief, with a minimum altitude of 759m and a maximum altitude of 1179m. The average rainfall in the Basin is 606mm, mainly between October and May. In 1987, after the peak of the bean policy, the Basin had 38% of its area with vegetation and 62% destined to agriculture and livestock. In 2018, the caatinga vegetation decreased to 34% and the area destined to agriculture increased to 66%. In that time, large areas with exposed soil were registered, reaching 33% of the Basin in 2018, further intensifying environmental degradation. Even after 50 years of the peak of the bean policy, the planting system is still non-conservationist, intensifying several environmental impacts, thus requiring environmental policies aimed at the conservation of the environment.