Abstract:
Accelerated pollution and eutrophication of rivers and streams because of human activity are a concern throughout the world and severe
in Africa where Ethiopia is case in point. The objective of this study was to assess the urban impact
on the ecological integrity of the Borkena River
at the eastern escarpment of the central Ethiopian
highlands. The water quality status and macroinvertebrate distribution and diversity of the river
were assessed during the dry and wet seasons.
Diversity indices revealed that a severe decline
in the ecological integrity of the Borkena River
downstream of Dessie and within Kombolcha
towns in terms of macroinvertebrate abundance
and composition. Clustering and ordination analysis clearly separated reference sites from urban impacted sites. At the urban-impacted sites, dissolved oxygen was also depleted to 0.5 mg/l and
BOD5 values were reached to a level of above
1,000 mg/l, with extremely low biological diversity
of pollution-sensitive taxa. These patterns are the
result of a combination of rampant dumping of
untreated wastes exacerbated by geologic, topographic, climatic and land use factors.
