Abstract

Headwater streams are important component of riverine ecosystem comprising the majority of the catchment area. These streams are densely networked in the highlands of Ethiopian river basins. Organic and inorganic materials and invertebrates are transported from the headwater streams and they have potential effect on downstream river habitat, water quality and living organisms. In recent years, the understanding of applying biological monitoring system for assessing the ecological health of streams, rivers and associated wetlands is increasing in developing countries including Ethiopia. At a time when anthropogenic activities are increasingly destroying the ecological integrity of riverine ecosystems, monitoring of biological communities is central to assess the health and function of streams for sustainable management. In this study, selected headwater streams in five river basins of Ethiopia were assessed using selected environmental parameters and benthic macroinvertebrate based score system (ETHbios). Streams in the upper section showed near natural ecological condition while after few kilometers in the downstream moderate to bad ecological degradation were measured. The major stressors causing degradation in the downstream sections include continuous human in-stream activities, nutrient loading from farm lands, presence of numerous cattle watering points, and organic and inorganic wastes from industries. Environmental parameters and biotic indices indicated traditional practices of local communities including river bank afforesting and production of perennial fodder grass along river side protect the streams from direct impact of nutrient enrichment.

Key Words: Headwater, Ecological integrity, Biomonitoring, Pollution, Biotic score