Abstract

This study was conducted on the hydrochemistry of shallow groundwater and surface water in the Ndop plain, North West Cameroon. The objectives were to determine the physico-chemical characteristics of water, controls on water chemistry and suitability for drinking and irrigation. Forty-six shallow groundwater and 26 surface water samples were investigated. Field measurements of physical parameters were preceded by chemical analyses of the samples for major ions and F^-. About 69% of the water sources had pH values below 6.5, classifying the water as barely acidic. Electrical conductivity (<282 µS/cm) and total dissolved solids (<183 mg/l) were low suggesting low-mineralised and freshwater. The relative abundance of major ions (meq/l) was Na²⁺>Ca²⁺>Mg²⁺>K⁺ for cations and HCO₃^->>NO₃^-≥Cl^->SO₄^2- for anions. Major ion concentrations were low, and within the WHO guidelines for drinking water, but F^-concentrations were much lower (<0.39 mg/l) and below guideline value. Main water types and proportions were Na-HCO₃ (53 %), Ca-HCO₃ (35 %) and a mixed Na-Ca-HCO₃ (11%). Predominant processes influencing water chemistry were incongruent dissolution of silicate minerals and cation-exchange of Na⁺ in rocks for Ca²⁺ in water. The low major ion concentrations indicated low water-rock interactions and short residence time. The analysed water was suitable for irrigation.

Key words: Water chemistry, hydrochemical controls, drinking-irrigation quality, Ndop plain, Cameroon.