Assessment of urban river water pollution with urbanization in East Africa

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.

Automated summary

Anthropogenic pollution has significant impact on river water quality, especially in urban areas of Africa. This study evaluated the impact of urbanization on the water quality of four urban rivers in Tanzania through water quality index and statistical analysis. The results showed that the water quality was significantly deteriorated in the lower reaches of the cities, indicating pollution characteristics in urban rivers of Africa. Some river sections had medium to good water quality, but the decline was mainly observed in the urban central areas, indicating a growing pollution tendency with the increasing population. Therefore, timely monitoring of surface water quality with an economical and feasible method is necessary to formulate water pollution control policies in response to rapid urban expansion in African countries.