Hydrogeochemical patterns in the Piauí River Basin: A multivariate statistical approach

Abstract

The Piauí River Basin, located in the state of Sergipe, Brazil, relies significantly on groundwater for human consumption and agricultural activities. However, the quality of these water resources is influenced by geological, anthropogenic, and seasonal factors, highlighting the need to understand the hydrogeochemical processes operating in the region. This study assessed the hydrogeochemical variability of groundwater from 15 wells distributed across karst, fissured, and granular aquifer domains during the dry and rainy seasons of 2022. Seventeen physicochemical parameters were determined, and Hierarchical Cluster Analysis (HCA) using Ward’s method was applied to identify spatial and temporal patterns. The results indicated that groundwater mineralization is strongly influenced by the interaction between aquifer lithology and recharge dynamics. During the dry season, increased concentrations of dissolved ions were observed due to reduced recharge and longer residence time. In the rainy season, recharge and leaching processes acted either as dilution agents or as intensifiers of mineral dissolution, depending on the hydrogeological domain. Well clustering revealed two main groups in each season: wells in the karst domain showed higher concentrations of calcium, bicarbonate, and electrical conductivity, while those in fissured and granular domains exhibited lower mineralization, reflecting differences in recharge influence and lithological composition.