Environmental fragility and risks to water sustainability in the extreme south of Bahia, Brazil: implications for the provision of basic sanitation services

The growing scarcity and gradual decline in the quality of freshwater are a threat to sustainable development and human survival, largely due to environmental degradation and the excessive use of water resources. Thus, the objective was to identify the levels of fragility and potential risks to water subsistence, especially in the provision of basic sanitation services, in the municipalities in the area covered by the Region of Planning and Management of Waters IV (RPMW IV), in the extreme south of Bahia, Brazil. For this purpose, the area was characterized by processing geographic data regarding the physical environment, climate, and land use to produce vector and raster layers. Subsequently, map algebra was applied in a GIS environment to obtain the levels of potential and emerging fragility. Potential fragility ranged from medium to high, totaling around 96% of the study area, with emphasis on the areas at the highest altitudes and coastal regions, with an average precipitation index of 1500 mm year⁻¹. For the emerging fragility, land use and cover were determining factors, especially the removal of forest cover. This cover was reduced by 1200 km² between 1985 and 2021 and the current remnants were restricted to environmental protection areas (around 68%). The results indicate an imminent risk to environmental sustainability, which may affect the provision of basic sanitation services due to the possible deterioration in quality or scarcity of water in the watersheds of RPMW IV.