Abstract:
Water pollution is a global problem and has been evident for long period of time. The
impact of urbanization on the rivers and streams is increasing with the development of
industry and population size in the city of Addis Ababa. The fast population growth,
uncontrolled urbanization and industrialization, poor sanitary situation, uncontrolled solid
and liquid waste disposal, etc. caused series quality degradation of the river waters in the
city. Therefore, assessment of physico-chemical parameters of selected rivers in the city of
Addis Ababa was conducted. In this study, physico-chemical parameters; EC, Temperature,
pH, Na+, NH4
+, K+ Mg2+, Ca2+, F- , Cl- , NO3
- , SO4
2- , PO4
2- , CO3
2- , HCO3
- of 20 water
samples were analyzed using column separation method collected from rivers flowing
across residential, agricultural, city centers and industrial sites of the study area; with a
view to assess the vitiations in the pattern of the rivers’ physico-chemical water quality
characteristics with respect to the urban land usage as well as to identify the potential
sources of pollution in the respective sites. The results of the physico-chemical parameter
analysis revealed that the rivers flowing across residential areas were characterized by
their relative highest mean levels of EC, pH, Na+, Mg2+, Ca2+, Cl- with 1222.80 μS/cm, 7.80,
185.47 mg/l, 28.08 mg/l and 82.04 mg/l respectively; highly elevated NH4
+, K+, SO4
2-,
HCO3
- levels were the characteristics of the river crossing agricultural site with mean
concentrations of 59.11 mg/l, 44.00 mg/l, 34.68 mg/l and 499.71 mg/l respectively; the
rivers flowing across the city centers were also characterized by their highest mean
concentrations of F-, and PO4
2- up to 1.28 mg/l and 4.90 mg/l respectively; NO3
- was also
recorded in the industrial river water samples with highest mean concentration of 25.26
mg/l relative to the other three sites. The water quality standards set by both WHO and EPA
for potable and surface waters respectively were surpassed by some of the physico-chemical
parameters studied. The level of NH4
+ was found above both of these standards in all the
river water samples collected from the four urban dominant activity sites. However, no
CO3
2- ions were recorded in all the river water samples crossing these sites. The strong pair
wise correlations, the spatial variations and the overall increasing and decreasing trend of
these physico-chemical water quality parameters showed intimate relations with
anthropogenic land use activities along the rivers. However, it was a little difficult to locate
and quantify the extent of these pollutants derived from each land use type.
Key Words: Physico-chemical parameters, Water quality standards, Column separation
method, Urbanization, Anthropogenic activities, Addis Ababa