Environmental flow assessment and implications on sustainability of aquatic ecosystems in Ethiopia: A literature review on global and national evidences

As part of water resources management policy, water resources projects undertake environmental flow assessments (EFA) to determine how much water should be maintained or released to the downstream part of rivers to protect the health of aquatic and riparian ecosystems and societal wellbeing. In Ethiopia, EFA is being undertaken mostly in relation to dam projects. Most of dam projects in Ethiopia consider the 95% exceedance probability flow (Q95) as acceptable for downstream releases, which does not consider the variable and dynamic nature of rivers or the impacts on societal livelihoods dependent on ecosystem services. This paper aims to explore the application of EFA in Ethiopia based on global and national experiences. The paper begins with an overview of the water resources and biodiversity that need protection; second, systematic review of the current status of application of EFA methodologies in Ethiopia; and finally, the main types of environmental flow methodologies available globally that can be utilized in different parts of the country were explored, with emphasis on projects and research endeavors. It is found that environmental flow is strongly considered in Ethiopia, which is critical as the country is a custodian to precious aquatic and riparian biodiversity resources which have national and global importance. However, it is found also that there is little research on the topic for advising appropriate EFA methodology application in Ethiopia. Thus, it is suggested a holistic approach of environmental flow assessment that can entertain all other types of methods in tropical highland rivers.