Advancing Bioassessment of Water Quality in Wadeable Rivers and Streams in Ethiopia
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Date
2024-01
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Addis Ababa University
Abstract
Numerous international bilateral, plurilateral, and multilateral treaties and conventions were signed between countries to protect human health and environmental pollution. However, most of the signatory countries fail to implement the treaties or conventions (Willis, 2012). For example, though Ethiopia has endorsed or ratified the Basel, Stockholm, and Rotterdam agreements, its legislations and policies for environmentally sound management of hazardous chemicals and wastes are still in infancy and are inefficient in preventing the illegal dumping of waste as well as contamination of water, soil and air resources (Tadesse, 2009).
This study reviewed the details of problems of surface water pollution in the metropolitan area of Addis Ababa and the upper Awash River catchment. Urbanisation, population growth, industrialisation without proper waste management facilities, unregulated agricultural practices, uncontrolled liquid and solid wastes, and law enforcement difficulties were the major gaps identified. Furthermore, there are significant gaps limiting efforts to address the magnitude of pesticide pollution in the catchment probably due to the shortage of laboratory facilities and the costs associated with the chemicals and equipment. This study forwarded important conclusions and recommendations to the respective stakeholders. To help the bioassessment of wadeable rivers and streams in Ethiopia, a macroinvertebrate kick sampling protocol has been developed using data from minimally impacted sites and testing it along the pollution gradients. Based on the results, the 2-minute RH kick sampling method is the recommended candidate for the bioassessment of wadeable rivers and streams in the country.
Using the developed macroinvertebrate kick sampling protocol in this study, the impacts of the Koka Hydropower dam on benthic macroinvertebrate structure and composition were further investigated. Hydropower has been used for generations to provide reliable, fossil-fuel-free electricity (source of clean energy), water supply for domestic uses and agricultural irrigation, recreational opportunities, several flood-control benefits, as well as a stable system for navigation. However, several disadvantages have also been recognised because of the construction of hydropower dams. It is particularly severe in large dams where there has been extinction of the many fish and other aquatic species, huge losses of forest, the disappearance of birds in floodplains, erosion of deltas, loss of wetland and farmland, and many other irreversible impacts. These impacts can have economic and social (e.g. Community displacement) health implications (consequences). This in turn points towards the need to seek a balance between pros and cons associated with dam construction. Currently, most public and policymakers perceive only the advantages (pros) of the hydropower dam and the impacts mentioned above are largely neglected. To create awareness among stakeholders and to recommend possible solutions to the problem, it was very crucial to conduct the ecological impacts of hydropower dams on the macroinvertebrate communities that include aquatic insects, crustaceans, annelids, mollusks, nematodes, planarians, and other invertebrates as these organisms play a critical role in the transfer of energy from basal resources (bottom layer) (e.g., algae, detritus, and associated microbes) to vertebrate consumers in aquatic food webs, and they serve as the primary food resource for many commercially and economically important fish species. The investigation of the hydropower dam on the structure and composition of macroinvertebrate communities showed that the downstream reach was severely impacted by water pollution compared to the midstream and upstream reaches of the Awash River, however, the results were partly complicated by the nutrient pollution, particularly from the midstream reach. The major factor, amongst others affecting the downstream reach, the water flow change (river velocity) was highlighted as a key variable structuring the macroinvertebrate communities and a variable that can be altered by damming.
Similarly, variation partitioning analysis was used to analyze the unique and shared effects of the three sets of predictor variables (environmental, land use, and spatial factors). The findings revealed that the three sets of predictors' shared variation in macroinvertebrate community composition was greater than their contributions. To put it bluntly, anthropogenic activities have a negative global influence on aquatic habitats. As a result, surface water biomonitoring is becoming increasingly crucial in estimating ecosystem deterioration and achieving environmental sustainability. Therefore, the development of methods kick sampling time) based on Ethiopian ecoregions to employ in the bioassessment of surface water quality has been mandatory. This would contribute to the assessment of water quality in wadeable rivers and streams in Ethiopia
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Addis-Abeba, métropolitain, gestion des déchets, haut bassin d’Awash, qualité de l’eau, Bioassessment of streams and rivers · Fixed sampling time · Single and multihabitat sampling · Macroinvertebrates · Ethiopia