Caracterização e comportamento hídrico das lagoas do sistema hidrogeológico cárstico do Grupo Bambuí na região de Lagoa Santa - Minas Gerais, Brasil

Abstract

The Lagoa Santa Karst Environmental Protection Area (LSKEPA), located in the central portion of Minas Gerais, hosts a complex and interconnected karst hydrogeological system, marked by the occurrence of lakes situated in dissolution features such as dolines and uvalas. Inserted within the São Francisco River basin, the region holds remarkable ecological, cultural, and scientific importance, while also facing increasing anthropogenic pressure. This doctoral thesis aimed to investigate the hydrological behavior of these lakes over the past 35 years, seeking to understand the natural and anthropogenic factors that influence their permanence and dynamics. The research adopted an integrated approach based on multitemporal geospatial data (Landsat imagery), historical rainfall series, morphostructural analyses, local geological and hydrogeological characterization, and the identification and quantification of tubular wells in the region. The study included the identification and classification of lakes based on their hydrological stability (perennial or intermittent), analysis of climatic and geological influences on water levels, and verification of the impacts caused by anthropogenic activities, especially groundwater exploitation. The results demonstrated that the permanence of lakes is strongly conditioned by the geomorphological characteristics of the depressions, prevailing lithology, topographic elevation, connectivity with the karst aquifer system, and the presence of geological structures linking surface water bodies to aquifers in the region. Lakes located in closed, elevated depressions over purer carbonate rocks showed greater hydrological stability. Conversely, those in lower areas or with more lateral development showed greater susceptibility to underground drainage and seasonal fluctuations. Additionally, increasing human intervention was observed: between 1985 and 2020, 715 active wells were identified, 292 of which significantly interfere with the hydrological dynamics of nearby lakes, particularly those with smaller volumes and greater dependency on groundwater. The multitemporal analysis enabled the classification of lakes according to their degree of connection with the aquifer, revealing that rainfall variability alone does not fully explain the observed behaviors. The synergistic action of climate, geology, and anthropogenic water use emerges as a key determinant in defining lakes hydrological behavior. It is concluded that the dynamics of these water bodies are multifactorial and require interdisciplinary approaches for their understanding and management. The results provide technical and scientific support for improving public policies on environmental protection and water resource management in vulnerable karst regions such as the Lagoa Santa Karst.