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Groundwater samples were evaluated through-out Turkana County (Kenya,East Africa) while looking for drinking water sources.Some samples showed high con-centrations of fluoride with values in the range of 0.15-5.87 mg/L.Almost 50％ of the samples exceeded the WHO and Kenyan potable water standard guideline value of 1.5 mg/L for drinking water quality.The hydrogeo-chemical studies revealed that the dominant cation in water is Na+ and the dominant anion is HCO3-resulting in Na-HCO3 type of groundwater,followed by Ca/Mg-HCO3 or Na-SO4 and Na-C1 in a few cases.Speciation modelling revealed that the groundwater is undersaturated with respect to gypsum and anhydrite,mostly undersaturated with respect to fluorite (6 samples are at equilibrium),and supersaturated or at equilibrium with respect to calcite(CaCO3).Precipitation of calcite favours the dissolution of F-rich minerals in the alkaline medium.Simultaneously,groundwater is enriched with sodium and bicarbonate,probably as a result of chemical weathering of Na-feldspar.Investigated groundwater can be presumably used for drinking purposes from 17 wells,but a detailed investiga-tion of other trace element concentrations is necessary.