"Anthropogenic pollution plays an important part in deteriorating the water quality of rivers all over the world, especially in urban areas of Africa where water quality monitoring is still seriously constrained by the limited test facility and capability.
In this study, for evaluating the impact of urbanization on the river water quality, we investigated four typical urban rivers of Tanzania through the upper-urban-down gradient assessment approach and analyzed by water quality index (WQI) and statistical methods.
The physicochemical indices monitored in these rivers revealed that the contents of those indicators of TN, TP, PO43-, NH4+, CODMn, and NO3- were accumulated significantly in the lower reaches of the cities, which indicated the life-type pollution characteristics in such urban rivers of Africa.
The following main conclusions are achieved from this study. The water quality of 30% of the investigated river sections is in the medium to good status based on the subjective WQI with sensory factors included. Moreover, the sections with obvious water quality decline are mainly limited to the river segments within the urban central area, and severe pollution of water bodies is closely related to large cities, indicating an increasing pollution tendency with the quickly growing population.
Therefore, to help formulate water pollution control policies in response to the rapid urban expansion in African countries, it is necessary to adopt an economical and feasible method to carry out early monitoring of surface water quality timely." This was explained in the study Assessment of urban river water pollution with urbanization in East Africa, published on the Environmental science and pollution research international.
The type of water pollution can be of a chemical, physical or microbiological nature and the consequences can compromise the health of the flora and fauna involved, up to humans, harming the ecosystem and water reserves for drinking use.
There are two main ways through which pollutants reach water: directly or indirectly. Direct pollution occurs when polluting substances are poured directly into watercourses without any purification treatment. The indirect route, on the other hand, takes place when the pollutants arrive in watercourses through the air or soil.