Vulnerabilidade ambiental e impacto na produção de sedimentos da bacia hidrográfica do rio Itacaiúnas (BHRI) - Província Mineral de Carajás, Sudeste da Amazônia

Abstract

The development of environmental vulnerability studies in a regional context and in particular in the Amazon requires a huge human, logistical and economic effort, which when incorporated into current technologies for data acquisition and processing (remote and in situ) and publicprivate partnerships, makes such research possible. This framework was what enabled the development of this thesis in the Itacaiúnas River Watershed (IRW), which has around 42.000 km² and is located in the area called “arc of deforestation in the Amazon”. Area of many socioeconomic-environmental conflicts related to the development of the region and its different types of use and occupation of the territory. Within this context, we developed this research whose main objective was to assess how environmental vulnerability relates to the current production of suspended sediments at the IRW. First, the areas of greater or lesser vulnerability were defined and identified, having the year 2019 as a timeframe, through recognized methodologies developed for this type of study in the Amazon region. Using geoprocessing routines in ArcGIS 10.8.1 software, five thematic maps and environmental vulnerability were built (geology, geomorphology, soils, use and occupation and climate) and finally using map algebra the map of BHRI's environmental vulnerability was generated. The results showed that the BHRI is moderately stable/vulnerable in an area of 28,058 km² of extension (68% of the basin), moderately stable in 8,961 km² of extension (with 22% of the basin) and moderately vulnerable in 4,314 km² (10% of the basin). of the basin). In parallel, the study on the production of sediments at the BHRI, was based on data acquired by the hydrometeorological monitoring project by the Instituto Tecnológico Vale – ITV. Monitoring takes place in 16 hydrosedimentological control sections distributed in the six main sub-basins that make up the BHRI, with four annual campaigns (high water levels, rising water levels, falling water levels, low water levels) that took place between 2015 and 2019, and aimed at building and comparing the curves- sediment key and sediment production between these different sub-basins, data already published in the Brazilian Journal of Water Resources (RBRH) in 2021. Finally, seeking to respond to hypothesis of this study, we carried out comparative analyzes of the relationship between the environmental vulnerabilities observed and the production of sediments, identifying and demonstrating which areas, which environmental factors and how much sediment is produced in the different sub-basins of the IRW. The results obtained allowed to get an integrated and compartmentalized view of the vulnerability and production of sediments at the BHRI that confirm that the ongoing legal mineral activities within protected areas of forests do not generate significant impacts on their vulnerability or on their production of sediments. In turn, the activities related to the use and occupation of the territory in nonprotected areas, promoted an intense replacement of the forest by pastures, generating the areas of greater environmental vulnerability and are directly associated with the greater “inputs” of sediments in the IRW.