Seasonal Variations in Groundwater of the Phreatic Aquiferous Formations in Douala City-Cameroon: Hydrogeochemistry and Water Quality

摘要

This study was to determine the seasonal variations of groundwater, the influence of the rock formations on the groundwater solute chemistry and groundwater domestic-agro-industrial quality using hydrogeochemical tools and physicochemical parameters; Ionic ratios, Gibbs diagrams, Piper diagrams, Durov diagrams and water quality indices. From physicochemical parameters; in the rainy season, pH ranged from, 4.6-7.1 ; EC, 0.023-1.63 mS/cm; Temperature, 26.3-29 0) C andTDS, 0.015-1.09 mg/L and in the dry season pH ranged from 5-7.2; EC, 0.01-1.61 mS/cm; Temperature, 24.4-29.5 0) C andTDS, 0.01-1.08 mg/L. Forty groundwater samples; 20 per season, wet and dry were analysed. Themajor ions fell below WHO acceptable limits for both seasons. The sequences of abundance of major ions were, Ca 2 ) >K ) >Mg 2 ) >NH 4) ) >Na ) , HCO 3) -) >Cl -) >SO 4) 2-) >NO 3) -) >HPO 4) 2- ) in wet season and Ca 2 ) >Mg 2 ) >K ) >Na ) >NH 4) ) , HCO 3) -) >Cl -) >SO 4) 2-) >HPO 4) 2-) >NO 3) - ) in dry season. Ion-exchange, simple dissolution and uncommon dissolution processes determined groundwater character. Groundwater ionic content was as a result of ion exchange from rock-weathering. Water types are; MgCl and MgHCO 3 ) in both seasons. Hydrogeochemical facies are; Ca-Mg-Cl-SO 4) , ) characteristic of groundwater some distance along its flow path ) and Ca-Mg-HCO 3) , characteristic of freshly recharged groundwater from precipitation. The groundwater indices of; Sodium Percent (% Na), Residual Sodium Carbonate (RSC) , Kelley’s ratio (KR), Sodium Adsorption Ratio (SAR), Electrical Conductivity (EC), Total Dissolved Solid (TDS), USSL? and Wilcox index were determined, evaluated and found to be suitable for agro-industrial uses in all seasons. Permeability Index (PI) , Water quality index (WQI) and Magnesium Adsorption Ratio (MAR) were not suitable in some areas and in some seasons.