This work aimed to investigate the hydrochemical evolution of groundwater with fluoride (F-) high contents and their association with hydrochemical types in a portion of the Outcrop Zone (OZ) of the Guarani Aquifer System (GAS). The selected area for the survey comprised the municipalities of Restinga Seca, Agudo, Paraíso do Sul and Novo Cabrais, in an area of 2.034 km2, located in the central region of the state of Rio Grande do Sul, southern Brazil. The methodology was based on non-parametric statistical analysis and evaluation of the characteristic ionic relations by means of graphs and diagrams. The used database consisted of a compilation of pre-existing data and collection of additional hydrochemical data. From the results obtained, it was possible to observe that groundwater with F- high contents are highly salinized, accompanied by increases in sodium, chloride and sulfate concentrations. The hydrochemical classification had predominance of sodium-chloride waters followed by sulfate-sodium and bicarbonate-sulphate sodium-chloride types. From the Piper diagram, a clear hydrochemical evolution was observed, which allowed inferring on the trends of cation and anion enrichment. The boron and total bromine parameters, evaluated by spectrophotometry, presented significant levels, where boron demonstrated a positive statistical correlation for F- and bromine.
