Stormwater impact on water quality of rivers subjected to point sources and urbanization – the case of Addis Ababa, Ethiopia
2019
Adugna, Dagnachew | Brook Lemma, | Sahilu Gebrie, Geremew | Larsen, Larissa | Yeshitela, Kumelachew | Bergen Jensen, Marina
Urbanization of a catchment often causes degeneration of rivers. We studied the water quality of three rivers in Addis Ababa based on the impact of stormwater and non‐point sources, and urbanization. Along these rivers several point sources were registered, with direct discharge of industrial and domestic wastes into them. To distinguish the impact of these year‐round point‐sources from stormwater, we analysed physicochemical parameters, nutrients and heavy metals sampled from upstream to downstream sections of each river in the dry and wet season. Dissolved oxygen (DO), NO₂–N, NH₄–N, PO₄–P, (Cr(VI) and Cu) exceeded international standards, pointing to a generally poor water quality of the rivers in both seasons. NO₃–N, Mn and Zn were problematic in dry season only. Although stormwater improved DO, conductivity, PO₄–P, Cr(VI) and Zn, the levels were still critical, pointing to construction sites, agriculture and pit latrines, somewhat offsetting the effect of stormwater dilution. No clear impact of urbanization pressure was found.
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