Potentiometric map based on integrated piezometer data with geophysical results, Manaus-AM / Mapa potenciométrico a partir de dados de piezômetros integrados com resultados de geofísica em Manaus-AM

Abstract

The research carried out consisted of a field survey upstream of the Lago Amazônico area and close to the Ecological Effluent Treatment Station (ETEE) of the National Institute for Research in the Amazon - INPA. The objective of the study was to detect possible impacts on the quality of groundwater due to the ETEE and the waters of Lago do Bosque da Ciência, which requires knowledge of the direction of groundwater flow at the site. The geophysical resistivity method, through the technique of vertical electrical sounding with the Schlumberger arrangement, was applied with the purpose of defining the depth of the top of the saturated zone in the study area as well as detecting possible impacts of the effluents of the treatment plant in subsurface. The resistivity method, through measurements by equipment placed on the surface, determines the electrical resistivity of the materials and their subsurface contrasts at different depths. In the area, three piezometers were installed, which enabled the calibration of the interpretation of the results of vertical electrical sounding. The survey of geophysical data provided a volume of information about the subsurface situation of the layout, lithological content and the depth of the water level of the subsurface layers through the seven vertical electrical surveys carried out around the INPA Lake and close to the ETEE. The results of the interpretation of the vertical electrical sounding and water level depth measurements in the piezometers were integrated to produce a potentiometric map to understand the hydrogeological behavior from the point of view of underground flow. The electrical resistivity values, relatively high in the study area, attribute a predominantly sandy lithological constitution, a result that is consolidated with the lithological description of the piezometers. The top of the saturated layer around the lake is deeper compared to the lake, causing its waters to seep into the aquifer. This is because the lake is artificial, constantly receiving water to maintain its level. The potentiometric map indicates a practically radial flow direction, with a slight inclination towards the north. The electrical surveys carried out near the treatment plant showed lower resistivity values, which may be related to the influence of effluents in the subsurface. The study was carried out with resources provided for in Law No. 8,387 and in accordance with Article 21 of Decree 10,521 / 2020 - INPA / SAMSUNG Partnership.