Modelo hidrogeológico de fluxo do flanco leste do Sinclinal Moeda (Quadrilátero Ferrífero – MG): caracterização, impactos e perspectivas futuras para o Aquífero Cauê

Abstract

The Cauê Aquifer is of great importance for the water supply of the third largest urban agglomeration in Brazil. The Metropolitan Region of Belo Horizonte is located partly in the Iron Quadrangle, where intense exploitation of iron ore occurs, an activity that requires the use of water for mineral processing and mine dewatering. In this context, this work aims to build a hydrogeological flow model of the Moeda Syncline’s eastern limb, pursuing the regional impact evaluation on the groundwater level between the years 1999 and 2019. In addition, it is intended to estimate the lowering predicted over the following 20 years, from 2019 to 2039. Therefore a conceptual and a numerical model of the area were built. The first consisted of defining boundary conditions and aquifer units, calculating hydrodynamic parameters, water balance, renewable reserve and flow analysis. The second, developed using the software Feflow, consisted of model assembly, steady-state calibration, transient-state calibration and water level lowering simulation. The Cauê, Gandarela and Moeda aquifers were considered aquifer units, among which the Cauê Aquifer had the highest hydraulic conductivity (9,45×10-7 m/s on average), as well as the highest recharge rate, with 38,7% of rainfall. The average volume pumped was estimated at 41 million m³/year, equivalent to about 150% of the renewable reserve of the Cauê Aquifer, calculated at 27 million m³/year. As a result of the transient-state calibration, it was estimated that between 1999 and 2019 there was a 13,6% baseflow reduction in the entire area, in addition to an average drawdown of 10,4 meters in the Cauê Aquifer and 2,2 meters in the other units. The most affected sector was Central 2, with a lowering of about 11,6 meters and a 21,6% reduction in baseflow. The simulation for the period from 2019 to 2039 resulted in a lowering of 7,4 meters on average, with the highest impact, once again, in the Central 2 sector, where the lowering was 10,8 meters on average. During this period, it was foreseen a baseflow reduction of 7,6% in the entire area, and of 14,7% in Córrego Fechos, located in the North Sector. In order to integrate all this data and generate more robust models in the future, it is suggested the installation of a monitoring network that guarantees the distribution of instruments throughout the área, and an adequate, constant collection of data, both on surface flow and groundwater level. This would improve the management of water resources, avoiding water scarcity for the population and ecossystems.