Assessment of urban river water pollution with urbanization in East Africa

Sophia Shuang Chen,Qiushi Shen,Cheng Yu,Qun Gao,Ismael Aaron Kimirei

doi:10.1007/s11356-021-18082-1

Abstract

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.

Highlights

Water pollution resulting from human activities has become a matter of global concern
Based on t-test of the 27 paired samples, the parameter values between dry and wet seasons do not show statistically significant difference reaching the level of p < 0.05 except for few parameters such as temperature, dissolved oxygen (DO), oxidation reduction potential (ORP), turbidity, nitrite ( NO2−), and ammonium ( NH4+)
The temperature values in wet period are a bit higher than those recorded in dry period, and turbidity values are relatively higher during the wet season than those in the dry season resulted from the increased sediment entering the water body with the flood during the rainy season

Summary

Introduction

Water pollution resulting from human activities has become a matter of global concern. Deterioration of surface water in less developed countries is caused mainly by urban population–related pollution rather than by agricultural or industrial pollutions (Capps et al 2016), considering that about 3.2 billion people live in cities, accounting for about 42% of the world’s total population (UN, 2019). Such a large population is still growing rapidly, it is bound to bring about a great pressure on the water quality degradation of rivers, that may endanger the health of residents along the line. Some other researches reported the water pollution in coastal area of Zanzibar resulted from the expanding of population and industrial activities and investigated the baseline concentrations of nutrients (Van Bruggen, 1990), nutrient dynamics and community response to nutrient loading (Johnstonc and Suleiman, 1997), and pesticides and groundwater pollution (Mmochi, 1998; 1997)

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Conclusion