Caracterização hidrogeológica e vulnerabilidade natural das águas subterrâneas no entorno do Centro Nacional de Pesquisa Milho e Sorgo - Sete Lagoas/MG

Abstract

The present research aims at contributing to a better understanding of the hydrogeological system and the natural vulnerability to contamination of the groundwater around the National Research Center on Corn and Sorghum (Centro Nacional de Pesquisa Milho e Sorgo CNPMS), which belongs to the Brazilian Agricultural Research Company (Empresa Brasileira de Pesquisa Agropecuária EMBRAPA), located in the city of Sete Lagoas MG. At first, a general characterization of the study area was made using data from field work and literature. During that reconnaissance stage of the work several visits were made to the site, with hydrogeological interest, such as water courses, lakes, springs, wells and cisterns. Field work involved soil and geological probing using manual and mechanical piercers, measurement of water infiltration in the soil with a Guelf permeameter, follow up on the drilling and mounting of the hydrogeological monitoring wells network, and measurements of groundwater quality and potentiometry in the monitoring wells. The set of data obtained during the initial phase was used to characterize the subsurface hydric circulation model. The conceptual hydrogeological model presented the main hydrostratigraphic units and groundwater flow conditions. From this model the computational hydrogeological model was developed, using the application Visual MODFLOW, which is capable of describing the hydrodynamic behavior of the groundwater around the CNPMS. Preliminary evaluation of the local groundwater contamination vulnerability was made with basis on the qualitative procedure denominated DRASTIC Agricultural Model. The computational hydrogeological model was also used to simulate contamination scenarios defined at several the agricultural areas on the CNPMS. The computational hydrogeological model indicated that the main groundwater flow direction is from the local watersheds towards Jequitibá and Matadouro streams. The DRASTIC Agricultural index showed five vulnerability classes: low, moderate, high, very high and extreme, with a predominance of the very high class (26 Km² or 34% of the assessed area), associated with the regions near the Jequitibá and Matadouro streams.