Hydrogeochemical Processes and Evolution of Groundwater in the Voltaian Aquifer of Krachi East Municipality, Oti Region, Ghana

Groundwater from the Voltaian aquifer serves as a vital resource for the rapidly growing Krachi East Municipality in Ghana. Despite its significance, detailed insights into its hydrogeochemical evolution remain limited. This study adopts an integrated approach, combining hydrochemical analysis, multivariate statistics, and spatial mapping to characterize groundwater quality, identify the processes controlling its chemistry, and evaluate its suitability for domestic and agricultural purposes, using sixteen samples. Major ions and physicochemical parameters were analyzed, and interpretation employed graphical methods, saturation index calculation, and multivariate statistical techniques, including Factor Analysis and Hierarchical Cluster Analysis on centred log-ratio transformed data. Water Quality Index was computed for drinking suitability, while irrigation suitability was assessed using Sodium Adsorption Ratio (SAR), Electrical Conductivity (EC), Sodium Percentage (Na%), and Magnesium Ratio (MR). Results indicate that groundwater is generally fresh (mean TDS: 363.19 mg/L; mean EC: 488.81 µS/cm) and dominated by a Na–HCO₃ facies (81.25% of samples). Gibbs plots suggest water–rock interaction, particularly silicate and carbonate weathering and ion exchange as the primary control on hydrochemistry. Four principal factors, explaining 92.84% of total variance, highlight contributions from both geogenic processes and anthropogenic influences. WQI classification shows 87.5% of samples fall under the “Excellent” category for drinking, meeting WHO standards. However, irrigation assessment reveals potential risks: although salinity hazards are low (EC < 750 µS/cm), most samples exhibit high sodicity (mean Na% ≈ 81.6%; 50% unsuitable) and magnesium hazards (mean MR ≈ 61.2%; 75% above recommended limits). Overall, the Voltaian aquifer provides groundwater of excellent quality for domestic use, but elevated sodicity and magnesium pose long-term threats to soil health and agricultural sustainability. These findings emphasize the need for integrating water quality indices into local management strategies and adopting mitigation measure such as gypsum application and optimized irrigation scheduling to safeguard socioeconomic and environmental well-being.