Hydrochemical characterization and multivariate analysis of groundwater evolution in the Dabus River catchment, western Ethiopia

Abstract

Groundwater is a fundamental natural resource, particularly in regions underlain by complex aquifer systems, where it serves as a key freshwater supply that supports domestic, agricultural, and ecosystem sustainability. Understanding of hydrochemical evolution of groundwater in heterogeneous volcanic-basement aquifer systems is challenging, particularly in hydrogeological data-scarce regions such as the western Dabus River catchment of Ethiopia. In the Dabus River Catchment, groundwater is primarily used for multi-applications, including drinking and domestic purposes, yet the geochemical processes governing its composition and spatial variability are not well understood. This study aims to investigate the hydrochemical characteristics and geochemical evolution of groundwater in the region using major ion chemistry integrated with multivariate statistical analysis. A total of 47 groundwater samples from hand-dug wells and boreholes were collected during the dry season and analyzed following standard hydrochemical protocols. Hydrochemical facies and controlling processes were evaluated using Piper and Gibbs diagrams, chloro-alkaline indices, and hierarchical cluster analysis (HCA). The results indicate that groundwater in the catchment is mainly fresh with electrical conductivity ranging from 22 to 638 µS/cm and total dissolved solids between 14 and 159 mg/L. Ca2+ and Na+ are the dominant cations, while HCO3− is the predominant anion, indicating a Ca–HCO3 hydrochemical facies with localized evolution toward Na–HCO3 type groundwater. Gibbs diagram analysis suggests that water–rock interaction is the principal mechanism controlling groundwater chemistry, while negative chloro-alkaline indices indicate cation-exchange reactions between groundwater and aquifer materials. Likewise, the cluster analysis reveals three hydrochemical groups representing progressive groundwater evolution along flow paths. These findings provide new insights into groundwater geochemical processes within crystalline and volcanic aquifer systems and establish baseline hydrochemical information for the study area. These findings contribute for groundwater monitoring, sustainable water resource management, and future hydrogeochemical investigations in similar data-limited regions.