Hydrogeochemical and anthropogenic influence on the quality of water sources in the Rio del Rey Basin, South Western, Cameroon, Gulf of Guinea

Abstract

This study which focuses on the hydrogeochemical and anthropogenic influence on water sources in the Rio del Rey Basin has provided an insight into the sources of major ions, water mineralisation processes, and the suitability of the water sources for drinking and agricultural purposes. Fifty-one (51) samples (38 groundwater, 9 surface water, 1 tap, 1 reservoir and 2 rainfall events) were analysed for physico-chemical and microbial quality. The pH of groundwater samples ranged from 5.5 to 8. Sixty percent (60%) of the groundwater samples were slightly acidic (5.5-6.4) and were different from the WHO (2004) standard for drinking water. Electrical conductivity values (3-274 μS/cm) and total dissolved solids (7.66 to 248.30 mg/l) for groundwater sources were low and signified low mineralisation and freshwater conditions. The relative abundance of major ions (meq/l) was Na⁺>K⁺>Mg²⁺>Ca²⁺ for cations and HCO₃^->NO₃^->SO₄^2->Cl^- for anions. The main water types were: Na-HCO₃ (45%), Ca-HCO₃ (35%), Na- Ca-HCO₃ (15%), Ca-Mg-Cl (2%) and NaCl (2%). The processes that influenced the water chemistry were incongruent silicate dissolution and cation exchange. The chemical constituents were low and within the WHO (2004) guidelines for drinking water except for high concentrations of NO₃^- (77.28 mg/l) and Br^- (0.08 mg/l) in one open well. Water quality index calculated using the adjusted form of CCME (2001) based on the major and chemical parameters (TDS, pH, F^- and Br^-) for groundwater and surface water data indicated that 90, 6, 2 and 2% provided excellent, good, marginal and poor water quality, respectively for drinking purposes. The evaluation of results showed that 90% of groundwater sources were suitable for agricultural purposes. Total coliform counts indicated that 97% of the groundwater sources were polluted.

Key words: Groundwater chemistry, microbial quality, anthropogenic influence, Rio del Rey Basin.