Abstract:
Background: Urbanization is one of the main causes for ecological problems due to the
introduction of pollutants into water bodies. Degradation of water resources with pollutant
effluent occurs by altering attributes that influence ecological integrity of surface water resource
such as water quality, habitat structure, energy source and biotic interactions. Showunga River
crosses Mizan-Aman town and has long been used for a variety of purposes including source of
public water supply, small scale irrigation, recreation, bathing, washing, animal watering, and
sand and stone dredging.
Objective: The main objective of this study is to assess the influences of urban pressure on the
ecological status of Showunga River.
Method: A total of eleven samples were collected along Showunga River by following the
standard methods of American Public Health Association procedures in April 2019 using cross
sectional study design. The assessment involved on-site measurements and collection of water
samples, laboratory analysis of water samples and macroinvertebrates identification to the level
of family using microscope. Kruskal-Wallis multiple comparison test, Pearson correlations,
Excel, SPSS version 24, PAST version 3.18 and STATISTICA® software package were
performed.
Results: The result clearly shows that upstream sites have oxygen level of 7 mgLˉ¹, while
turbidity, BOD, nitrate, phosphate, and chloride concentrations was elevated at midstream sites
where main human activity is undertaken. Macroinvertebrate assemblages were compromised
in the mid-stream sites where diversity of sensitive taxa was diminished due to anthropogenic
disturbances. However, downstream sites showed a gradient of recovery where the most
downstream site, S11, was found to have better macroinvertebrate diversity with improved
water quality than midstream sites.
Conclusion: Physicochemical and biological data revealed that much influence of urban
pressure at the midstream sites (waste water discharge, coffee processing, sand and stone
deranging are main ecological deteriorated), thus necessitated a need for mitigation measure to
save the Showunga River.
