Characterization and classification of lakes based on geospatial analyses in the karst hydrogeological system of the Bambuí group, Lagoa Santa, Minas Gerais, Brazil

Abstract

The karst of Lagoa Santa is a protected area located near the city of Belo Horizonte, in Minas Gerais state (Brazil), namely Lagoa Santa Karst Environmental Protection Area (EPA), one of the main research areas related to archeology, paleontology, speleology and hydrogeology in the Brazilian territory. The region is comprised by several lakes, because of its complex water system due to karst evolution. In addition, the karstic nature of the rocks in the region allows the existence of several other typical dissolution morphologies, such as: caves, speleothems, sinkholes, uvalas, among others. The morpho-structural characteristics, combined with the local geology, can provide important information about the behavior of lakes in view of the cycles of expansion and retraction of the water surface. Thus, this work aims to understand the water dynamics of the lakes present in the Karst of Lagoa Santa through analysis of spatial data between the years 1984 and 2020. Based on the surveys, 153 lakes were identified in the study region in the last 35 years: 40 perennial lakes, 89 intermittent lakes, 19 new lakes and 5 lakes that dried up completely. Also, this study compares the relationship of each lake with the type of relief depressions (Sinkhole or Uvala), rock masses and the main negative structural lineaments. The data obtained allowed the identification of which characteristics are diagnostic for perenniality or intermittence of existing lakes in the region, as well as the grouping of existing lakes into subgroups with similar geological and morpho-structural characteristics. The most important characteristics to define the water dynamics on lakes are the evolutionary state in karst depressions and the presence of structural lineaments, in which in more evolved depressions (uvalas) the lakes tend to be intermittent and in less evolved depressions (sinkholes) the lakes tend to be perennial. Finally, the water bodies associated with structural lineaments may be the condition for the permanence of water in some depressions, mainly in lakes over non-carbonate formations existing in the region.