REGIONAL CHARACTERIZATION OF THE ENTRE RIBEIROS AQUIFER, NORTHWEST OF MINAS GERAIS STATE, BRAZIL

Caracterização regional do aquífero Entre Ribeiros, noroeste do Estado de Minas Gerais

Resumen

The Entre Ribeiros Aquifer is a virtually unknown groundwater reservoir located in the northeastern portion of the Paracatu County, northwest of Minas Gerais State, Central Brazil. The reservoir rocks are limestone, marl, siltstone and shale from the base of the Bambuí Group, including the Sete Lagoas and Serra de Santa Helena formations. Karstification processes are limited, since de limestone rocks are lenses interfingered with siltstone, marl and shale. The aquifer is classified as a fissure-karstic type, anisotropic and heterogeneous, confined by a shale layer. The main data obtained from wells dataset include: mean well discharge of 56 m³/h (and outliers up to 100 m³/h), hydraulic conductivity about 10^-7 m/s, transmissivity varying from 10^-3 to 10^-5 m²/s and average storage coefficient 10^-4. The fracturing-karstification interconnected index is estimated about 5% and the saturated thickness is considered as 100 meters. The total area of distribution of the Entre Ribeiros Aquifer is estimated at 5,500 km², what demonstrates its regional importance. In present days, the main use of the water in the region is for irrigation, which arise the concern of overexploitation risk. In this sense it is important to apply management assessment actions, including water level monitoring, water availability estimations, combined use of groundwater and surface water sources and increase of surficial reservoirs. The sustainability of the Entre Ribeiros Aquifer is important to keep the baseflow that feeds the Paracatu River in the rain recession period, and consequently, the São Francisco River discharge.