Hydrochemical evolution of groundwater in Soubre and Gagnoa counties, Cote d'Ivoire

A better knowledge of groundwater quality necessarily requires identifying the hydrogeochemical processes that influence groundwater nature. Water resource management may be better handled in this way. Thirty samples were collected and analysed for various ions in this study to investigate the hydrochemical characteristics and processes that regulate groundwater chemistry in Gagnoa and Soubre ' counties. Results indicate that in the study area, groundwater is acidic and fresh. The major anions are abundant in amounts: HCO3- > SO42- > Cl- > NO3- and Na+ > Ca2+ > Mg2+ > K+ for major cations. Piper trilinear plot shows that the main groundwater types are Ca-Mg-HCO3, Ca-Mg-HCO3, Na-Cl, Ca-Mg-Cl and Ca-SO4 indicating the predominance of hydrogen carbonate facies, which are widespread in crystalline aquifers. According to Gibbs diagram, groundwater chemistry is most influenced by rock -water interaction. The ionic ratios indicate that the silicate weathering is due to oligoclase minerals, while the carbonate dissolution is due to carbonate minerals. The calculation of saturation indices indicates that groundwater samples are undersaturated for carbonate (calcite and dolomite) and evaporite (gypsum) minerals. Chloro-alkaline indices indicate the influence of cation exchange. The knowledge of various processes and their effects on groundwater mineralisation in the studied area contribute to efficient groundwater management.