Assessing Human Impacts on the Greater Akaki River, Ethiopia Using Macroinvertebrates

Abstract

We assessed the impacts of human activities on the Greater Akaki River using physicochemical parameters and macroinvertebrate metrics. Physicochemical samples and macro­invertebrates were collected bimonthly from eight sites established on the Greater Akaki River from February 2006 to April 2006. Eleven metrics representing richness, composition and tolerance/intolerance measures and which were thought to reveal changes along the river, were considered for the study. There was change in macroinvertebrate community structure as one proceeded from the upper reaches to the lower reaches along the Greater Akaki River. The upper reaches were characterized by greater number and diversity of taxa while the middle and lower reaches were dominated by fewer tolerant taxa. Spearman correlation analysis showed that metrics, expected to decrease with perturbation, had strong negative relationship with nutrients and measures of biological and chemical oxygen demand. Among the nutrients, most of these metrics had strong negative relationship with Ammonia. Change in structural organization of macro­invertebrates was attributed to nutrient enrichment and oxygen depletion. The study revealed that raw sewage and solid waste from residential and commercial centres, and runoff from impervious surfaces are responsible for the impairment in Greater Akaki River.