Utilização de sondagens elétricas verticais na avaliação dos recursos hídricos subterrâneos na Fazenda Alta Floresta II no município de Tailândia-Pa

Abstract

A research was made on the Alta Floresta II farm in the municipality of Thailandia, state of Pará, the studied area is situated to the north of the city, approximately 15 km from the downtown and located between the sedimentary basins of Grajaú and Marajó. The main objective of the study was to perform hydrogeological mapping of the studied area through the identification of the depth and thickness of the aquifer formation with the method of Electro-resistivity (ER) and the analysis of natural vulnerability to contamination, helping to find in the best location to the deep tubular wells in the study area, besides analyzing the behavior of the hydrogeological flow present in the studied area through the elaboration of a potentiometric map. For this research the ER Method was applied using the Vertical Electrical Survey (SEV) technique. They were performed 38 SEVs equidistant 100 m between them that allowed to measure the variations of resistivity in depth in the middle, punctually. The results showed that the ER method attended the objective of the investigation effectively, identifying the Itapecuru Group as the aquifer formation in the studied area. Through the schematic stratigraphic sections, it was observed that the aquifer starts at an average depth of 56 m and has an average thickness of 139 m. From data possession it was possible to determine that SEVs 1, 9 and 10 presented the best sites for the installation of a deep tubular well. However, among them, the most successful point is the SEV_10, which presented the top at 38 m, its base up to the research limit (200 m) and a 162 m water column. Through the vulnerability map it was possible to verify that the susceptibility of the aquifer to natural contamination is predominantly low. The potentiometric map indicated the preferential direction of flow (SW-NE) towards the central part of the Fazenda Alta Floresta II, which is the region where the deepest water level (NA) is concentrated. Therefore, it was possible to respond to project objectives in the study area, as well as to indicate new possibilities for future hydrogeological studies of vulnerability to contamination using geophysical methods of prospecting.