Hydrochemical peculiarities and groundwater quality assessment of the Birimian and Tarkwaian aquifer systems in Bosome Freho District and Bekwai Municipality of the Ashanti Region, Ghana

• Published in: Environmental Earth Sciences
• Main Authors: Okofo Boansi, Louis, Anderson, Nana Akyerefi, Bedu-Addo, Kenneth, Armoo, Ekua Afrakoma
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2021
• Subjects: Birimian aquifer system; Groundwater quality and contamination and the application of GIS; Natural baseline chemistry; Thematic Issue; Inverse geochemical modelling; Chloro-alkaline indices; Carbonic acid
• Online Access: https://repository.publisso.de/resource/frl:6444172; https://doi.org/10.1007/s12665-021-10081-2

The Birimian and Tarkwaian aquifer systems are the main sources of water supply for the Bosome Freho District and Bekwai Municipality inhabitants in the Ashanti region of Ghana. A hydrogeochemical assessment was carried out to ascertain the natural baseline chemistry of the groundwaters and the factors influencing groundwater chemistry in these two areas. A multivariate statistical tool consisting of principal component analysis (PCA) and hierarchical cluster analysis (HCA) together with hydrochemical graphical plots was applied on 64 groundwater samples. The Q–mode HCA results were used to explain the changes in groundwater chemistry along the flow paths where three spatial groundwater zones and water types were delineated. The first type consists of Ca–Mg–HCO₃ freshwater (recharge zone), which transitions into Ca–Na–HCO₃ or Na–Ca–HCO₃ mixed waters (intermediate zone) and finally evolves to the third type of Na–Ca–Mg–HCO₃–Cl water (discharge zone). The study also reveals that the natural process influencing water chemistry is groundwater–rock interaction from carbonate and silicate weathering/dissolution, aided by carbonic acid from precipitation and releases concentration of Na⁺, Ca²⁺, Mg²⁺, and HCO₃⁻ into the groundwaters significantly. The chloro-alkaline indices also reveal cation exchange as the principal natural factor that controls groundwater chemistry in the area. Inverse geochemical modelling shows the dissolution of primary minerals such as dolomite, plagioclase, halite, gypsum, and precipitation of calcite and chlorite along the groundwater flow path. Anthropogenic activities have little influence on groundwater chemistry. The quality of groundwater in the Bosome Freho District and Bekwai Municipality is suitable for irrigational use and drinking water consumption. The results obtained so far will contribute to research paucity in the study area and serve as a guide for decision-makers for improved water resources management.