Horizontal and vertical compartmentalization in the fissure and karstic aquifers of the Lagoa Santa Karst Environmental Protection Area and surroundings, Minas Gerais, Brazil

Abstract

The study area comprises the Lagoa Santa Karst Environmental Protection Area (EPA) and its surroundings in the metropolitan region of Belo Horizonte. The complex and fragile karstic system of the Sete Lagoas Formation is the main local aquifer and an important reservoir of groundwater for human supply. Based on multidisciplinary studies, a refinement of the Hydrogeological Model of Paula (2019) was made. The study area was expanded to northwest and vertical and horizontal compartmentalization of the aquifers were proposed. The horizontal compartmentalization of the karstic aquifer was based on hydrogeological, hydrodynamic and hydrochemical aspects, where three more karstified compartments were defined. In vertical compartmentalization of the karstic and fissure aquifers, fractures (water inflows), lithological descriptions, cover width and hydraulic conductivity of wells were considered. In the limestones, the more karstified portion extends down to 30 m deep and the crystalline basement acts as an aquifuge at depths greater than 60 m. Six hydrogeologic units were proposed: Granular Aquifer (covers), Aquiclude (pelites of Serra de Santa Helena Formation), Karstic and Fissured-Karstic Aquifer (carbonates of Sete Lagoas Formation), and Fissure Aquifer and Aquifuge (crystalline basement of Belo Horizonte complex).