Hydrogeochemical analysis, geophysical assessment and geological mapping of the recharge zone of the Guarani Aquifer system in Santa Cruz do Sul, Brazil

Abstract

A large part of the Guarani Aquifer is in the state of Rio Grande do Sul (southern Brazil). Aquifer's recharge area is in the central and western regions of the state. So, this work was focused on the municipality of Santa Cruz do Sul. Because there is no water resources plan in the state by 2022, the hydrogeochemical, geophysical properties, and geological characteristics of the aquifer recharge region were evaluated. Field data were gathered, including chemical analysis of water in different wells and geophysical surveys in refraction seismic and geoelectrical methods. In addition, geological information was obtained from the Groundwater Information System (SIAGAS) public database. The different chemical parameters were mapped to perceive some elements' concentrations in Santa Cruz do Sul according to the SIAGAS data. In addition, the seismic refraction data and geoelectric method were processed and interpreted, concatenating all these results with the geology obtained from SIAGAS wells. The existing formations and the static level of the Guarani Aquifer were mapped using geological data. A high concentration of lead in the region which is a possible aquifer was found using geophysical methods. If located in this area aquifer could be used for human, agropastoral, or industrial after treatments.