59 research outputs found
The water quality degradation of upper Awash River, Ethiopia
Benthic macroinvertebrate based assessment of water quality in the upper Awash River, along the river course of about 500 kms was conducted on quarterly bases between September 2009 and August 2010. This paper reports the complete identification of macroinvertebrates together with measurements of physico-chemical parameters and heavy metal concentrations which were considered as a tool for assessing the water quality status of upper Awash river, Ethiopia. Benthic animals and water samples were collected from three different sampling sites located in the upper Awash River, and analyzed to evaluate stressor sources and the general stream water quality. The percentage abundance of families of various macroinvertebrates taxonomic groups was identified from all sites. Accordingly, Koka bridge site of the upper Awash River had low water quality status which is likely to be due to poor farming, untreated effluents from factories and poor provision of sanitation facilities to the riparian communities. Apparently, the concentrations of the selected nutrients and heavy metals did not differ significantly among the sampling sites (ANOVA, P > 0.05), presumably due to pollution of the whole stream reach by the catchment nutrient sources. Ten orders of benthic macroinvertebrates consisting of 36 families were identified. The highest family richness was observed in Ginchi, slightly impacted site (1) whilst the least faunal diversity was observed in Koka Bridge (7 families) indicating the effect of water quality class differences among the sampling sites.Key words: Macroinvertebrates, organic pollution, heavy metals, water quality, anthropogenic impact, upper Awash Rive
Longitudinal river zonation in the tropics: examples of fish and caddisflies from endorheic Awash river, Ethiopia
Primary Research PaperSpecific concepts of fluvial ecology are
well studied in riverine ecosystems of the temperate
zone but poorly investigated in the Afrotropical
region. Hence, we examined the longitudinal zonation
of fish and adult caddisfly (Trichoptera) assemblages
in the endorheic Awash River (1,250 km in length),
Ethiopia. We expected that species assemblages are
structured along environmental gradients, reflecting
the pattern of large-scale freshwater ecoregions. We
applied multivariate statistical methods to test for differences in spatial species assemblage structure and
identified characteristic taxa of the observed biocoenoses
by indicator species analyses. Fish and
caddisfly assemblages were clustered into highland
and lowland communities, following the freshwater
ecoregions, but separated by an ecotone with highest
biodiversity. Moreover, the caddisfly results suggest
separating the heterogeneous highlands into a forested
and a deforested zone. Surprisingly, the Awash
drainage is rather species-poor: only 11 fish (1
endemic, 2 introduced) and 28 caddisfly species (8
new records for Ethiopia) were recorded from the
mainstem and its major tributaries. Nevertheless,
specialized species characterize the highland forests, whereas the lowlands primarily host geographically
widely distributed species. This study showed that a
combined approach of fish and caddisflies is a
suitable method for assessing regional characteristics
of fluvial ecosystems in the tropicsinfo:eu-repo/semantics/publishedVersio
Variable residence time-based model for BOD removal in free-water surface wetlands
Constructed wetlands have been increasingly used for treatment of secondary wastewater containing various contaminants. This paper presents a Variable Residence Time (VART)-based model, called VART-BOD model, for simulation of BOD removal processes in constructed wetlands with free water surface (FWS). Mathematically, the VART-BOD model describes a free water surface wetland with three vertical layers, including vegetated water column layer, advection-dominated upper root layer, and diffusion-dominated lower root layer. Biogeochemically, the VART-BOD model simulates various BOD removal processses and mechanisms, including monod kinetics of bacterial growth, mass exchange between water column and root layers, advection, dispersion, and diffusion. A unique feature of the VART-BOD model is the incorporation of a dynamic diffusion-dominated root-zone. The VART-BOD model was tested with data collected from two distinct FWS wetlands: Gustine Wetland, USA and Manzala Wetland, Egypt. Testing results showed that the coefficient of determination (r2) and root mean square error (RMSE) values vary in the ranges of 0.73â0.99 and 0.41â8.70 mg/L, respectively, for Gustine Wetland cells while r2 = 0.98 and RMSE = 0.72 mg/L for Manzala Wetland. The VART-BOD model is a reliable and efficient tool for designing constructed wetlands and for understanding effects of various processes and mechanisms on the treatment efficiency of wastewater in constructed wetlands
Levels of outpatient satisfaction at selected health facilities in six regions of Ethiopia
No Abstract. Ethiopian Journal of Health Development Vol. 22 (1) 2008: pp. 42-4
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