Hydrogeochemical characterization and evolution of groundwater in parts of the Western and Central Regions of Ghana

Abstract

Groundwater serves as a critical resource for domestic, agricultural, and industrial use across southern Ghana, particularly in rural and peri-urban areas. This study evaluates the hydrogeochemical characteristics and suitability of groundwater in parts of the Western and Central Regions, covering Wassa Amenfi East, Tarkwa-Nsuaem, Twifo Atti Morkwa, and Assin North districts. Forty-eight groundwater samples were collected during the transition between the rainy and dry seasons in August and analysed for major ions, heavy metals, and key physicochemical parameters. Results showed that while most samples were within WHO limits for parameters such as NO₃^-, HCO₃^-, and PO₄^3-, elevated concentrations of EC, TDS, Na⁺, Cl^-, SO₄^2-, F^-, and Mn were observed in mining-influenced areas, indicating salinization and contamination risks. Multivariate analysis (PCA and HCA) identified key hydrogeochemical processes including silicate and carbonate weathering, sulfide oxidation, redox transitions, and anthropogenic pollution from agriculture and sanitation. Groundwater facies were predominantly Ca–Mg–Cl–SO?, consistent with mineralized bedrock influence, while samples in recharge zones showed Ca–Mg–HCO? characteristics. Irrigation indices yielded mixed results: although 58% of samples were classified as “Good” to “Permissible” based on Na%, SAR, and PI, all samples exceeded the RSBC threshold, suggesting potential hazards to soil permeability due to excess bicarbonate. Pollution indices revealed localized zones of moderate nitrate contamination and elevated fluoride levels, with 25% of samples exceeding PIG thresholds, especially in areas with intensive land use. These findings underscore the spatial variability and vulnerability of groundwater quality in the region, driven by both geological and anthropogenic factors.