Relationship between hydrochemical patterns and depths of water bearing frac-tures in acid volcanic rocks from serra geral formation

Abstract

This study aimed to evaluate the existence of different hydrochemical patterns of fractured aquifers of the Serra Geral Aquifer System (SGAS), relating these patterns with the depths of the fractures bearing water in the city of Carlos Barbosa-RS. Hydrochemical information from samples collected in 12 wells and 3 springs along two sampling campaigns were used for this work. Schoeller and Stiff diagrams were employed for data analysis, beyond the statistical cluster analysis in order to verify similar patterns between the sampled points. Good correlation between hydrochemical patterns and the depth of the fractures bearing water were observed, allowing the identification of two groundwater groups. One group of wells aggregates samples presenting low concentration of ions associated to fractures depths located less than 30 meters, the second group is constituted by wells presenting high concentration of ions such as calcium, sodium, bicarbonates, and fractures depths located between 50 and 112 meters. The explanation of these differences can be related to the movement of water and water-rock interaction occurs differently depending on the depth of water inflow.