Urbanization impact on the water resources with major Third World cities: A case study for Nairobi and its environs

Abstract

The expansion of low income urban dwellings (slums and shanty towns) and the high level of unplanned and poorly planned industrial developments have kept the rivers and drainage systems within the city of Nairobi and its environs under high levels of pollution. Recent investigations of the surface waters around Nairobi indicate that rivers Ngong, Mathare, Nairobi and Rui Rwaka become heavily contaminated by heavy metals after flowing through both the industrial area and the low income urban centers. It is observed that both Nairobi and Mathare rivers become especially pol- luted after they flow through Majengo and Mathare slums respectively. The Ngong river on the other hand r eceives oily and toxic heavy metal discharges as it flows through the industrial area, while Rui Rwaka r eceives alcohol, heavy metals and offensive effluents from the breweries factory as it flows through the area of concern. Chemical results of water samples collected from the Ngong River at the industrial area show high elec- trical conductivity and total dissolved solids (TDS) with high pH and temperature compared with the upper r eaches of the river at Ngong Road. Mathare and Nairobi rivers have higher electrical conductivity, and dissolved solids (TDS) due to discharges into them as they pass through the Majengo and Mathare slums r espectively. Rui Rwaka contains high total suspended solids (TSS) after receiving the offensive effluent dis- charges from the Breweries Factory. Water from these rivers is used for drinking and for other domestic pur- poses in those parts of the city and hence the exposure to water borne diseases.