Chemistry and pollution of natural waters in western Kenya

Selected water analyses from the literature and current research in western Kenya are tabulated and the relationships between critical water quality parameters described. The waters are chemically characterised with Na as the dominant cation and bicarbonate as the dominant anion and, while waters of obviously different sources are represented, the available chemical data point to a general classification of bicarbonate-Na-rich waters, even for the saline waters of Lake Magadi. Potassium and chloride are among the less abundant constituents. The concentration level of nutrients (nitrate, phosphate and sulphate) is mostly lower than maximum permissible drinking water levels, and salinity is not yet a serious problem in water bodies that are exploited for domestic and industrial purposes. Fluoride levels are variable with the higher values occurring in waters in and around the Rift Valley. Limited analytical data for in waters from the Eldoret, Kiambu and Nairobi areas indicate concentrations well above world average figures. Mean values of some key water quality indicators such as total dissolved solids, total suspended solids and heavy metals are well below the threshold for contaminated water. These values are however exceeded by several factors in saline waters of lakes and in some springs. Significant organic pollution is reflected by mean values of parameters such as biochemical oxygen demand and faecal coliforms. The present quality of most of the water bodies in this part of the country is considered to be adequate at present for domestic and other purposes, though a gradual decrease in quality is evident from the recent upsurge in industrial activities in the subregion. (C) 1997 Elsevier Science Ltd.