The principal hydrochemical features of the Botucatú aquifer system in Sao Paulo State - SE Brasil - was studied from 67 groundwater chemical analysis. Westward, in the Botucatú aquifer system the progressive confining condition, with depth of the top of aquifer layer, increases the groundwater temperature slowly.
Moreover, the residence time increases the water salt content towards the natural flow direction (E-W). As résults ,th'e recent calcium and magnesium bicarbonate groundwater change first to sodium bicarbonate and them to sodium chloride-sul.fate