Aplicação e adaptações de métodos de vulnerabilidade intrínseca em climas tropicais - Quadrilátero Ferrífero, Brasil

Abstract

Water is an essential resource for life and plays a central role in most economic activities. However, population growth and the expansion of mining activities, when conducted without proper environmental planning, increase the risks of contamination of groundwater resources. Mapping the vulnerability of aquifers to contamination emerges as an important tool to identify areas more susceptible to contamination and thus promote actions for the preservation and sustainable management of groundwater. Although there are several vulnerability assessment methods, many of them were not developed for tropical climates and do not accurately represent actual risk conditions. Therefore, this study proposes the development of a vulnerability method applicable to multiple aquifers, considering the intrinsic vulnerability assessment in the western portion of the Quadrilátero Ferrífero, specifically in the Moeda Syncline. This region is of great economic significance due to the presence of gold and iron mines, and hydrogeologically important because of the water sources that supply a significant portion of the water consumed by the Metropolitan Region of Belo Horizonte. Of particular note is the Cauê Aquifer, considered the main groundwater reservoir in the Quadrilátero Ferrífero. It plays a crucial role in both the water supply for the population and the management of mining enterprises. For this evaluation, four vulnerability methods were applied: DRASTIC, SINTACS, GOD, and EPIK, each developed to assess different types of aquifers, including fractured, porous, and karst aquifers. The original methods, when applied to the Moeda Syncline, proved to be less effective since they were designed for other contexts, without considering the characteristics of tropical climates. To overcome these limitations, adaptations were introduced based on the physical characteristics of the study area. Based on the results obtained, it was concluded that the methods tailored to each type of aquifer, with the proposed adaptations, demonstrated greater efficiency compared to the original methods. The DRASTIC method, although developed for all types of aquifers, proved effective in identifying the main aquifers susceptible to contamination. Based on the application and adaptation of these four methods, a new method, named GEOGRIC, was developed to assess the intrinsic vulnerability to contamination in multiple aquifers for regional scales in Brazil. The GEOGRIC method, derived from the DRASTIC method, is an acronym for geology (G), epikarst (E), land use and occupation (O), degree of confinement (G), recharge (R), isopachs (I), and hydraulic conductivity (C). This method proved effective when applied to the Moeda Syncline, identifying the most vulnerable aquifers to contamination, particularly the aquifers of the cover layers, Cauê, and Gandarela.