Modelo hidrogeológico de fluxo do flanco oeste do Sinclinal Moeda : passado, presente e futuro do aquífero Cauê, Quadrilátero Ferrífero – Minas Gerais, Brasil

Abstract

The Moeda Syncline, on the western slope of the Iron Quadrangle in Minas Gerais, Brazil, is crucial for water supply and iron ore exploration in the region. However, it faces challenges due to extensive exploitation, industrial demand, and climate change. This hydrogeological conceptual study evaluated the water dynamics and aquifers on the western flank of the Moeda Syncline. Aquifer and non-aquifer units were defined through a regional analysis of hydrogeological aspects, and hydrogeological boundaries were established to understand the hydraulic interaction of emerging units. Hydraulic parameters were obtained through pumping tests and aquifer tests, and the water balance was calculated by separating hydrographs. The permanent reserve was calculated, and aquifer interference was assessed through artificial discharge. Additionally, a potentiometric map was developed from the interpretation of data obtained from piezometer monitoring, allowing the identification of a main regional flow from north to south and a secondary regional flow from east to west, as well as determining locations of subsurface inflow. Due to exploitation activities, a lowering of the water table was observed by 90 meters in the northern part, 40 meters in the central part, and 140 meters in the southern part. Regionally, the cone of depression affects not only the Cauê Aquifer but also associated aquifer units. This flow reversal began in October 2009 because the authorized pumping rate exceeded the recharge rate in the Cauê Aquifer. In this context, to understand the behavior of these aquifers over time, numerical flow modeling was used to analyze hydrogeological changes and water availability in the region since September 1999. The model was divided into northern, central, and southern sectors in upper and lower portions, calibrated with observed data, and used to simulate future scenarios, including the continuation of Cauê Aquifer exploitation until 2039. It was concluded that there is a deficit of groundwater in the northern, central, and southern compartments, indicating more water outflow than inflow. The locations most affected by underground exploitation were identified, and it was estimated that by 2039, in a conservative scenario, there would be a lowering of 12 meters in the northern compartment, 10 meters in the central compartment, and 10 meters in the southern compartment on the western flank of the Moeda Syncline.