Hydrogeological and hydrochemistry characterization of groundwater from São Gabriel Region, RS

Abstract

The present study investigates the hydrogeological and hydrochemical characterization of groundwater in the region of São Gabriel, RS. It was made 55 chemical analysis of groundwater samples collected in 55 deep wells from different locations and different hydrogeological contexts. The municipality of São Gabriel consists mainly of sedimentary rocks of the Paraná Basin. In this way the main aquifers have groundwater with very different chemical characteristics, reflecting different depositional environments and mineralogical compositions. Granitic and gneissic rocks from the Sul-rio-grandense shield comprise the fractured aquifer that occur subordinate in the southern portion of the municipality . Thus, the quality of groundwater in the region changes according to the hydrogeological conditions of each aquifer and to the relationship between them. In this area, Fluorine and Sodium are the main parameters that restrict the use of groundwater for human supply, irrigation and livestock watering. According to the maximum parameters allowed by an ordinance of the Brazilian Ministry of Health, around 30% of the analyzed groundwater samples are inappropriate for consumption regarding to these ions. The main aquifers of the region, in quantitative and qualitative terms, are Aquifer Rio Bonito (ARB) and the Guarani Aquifer System (SAG), located respectively in the southern and northeastern portion of the county. The waters of the wells that capture these aquifers have a good quality, potable and flow rates can be regarded as best in the region.