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| dc.contributor.author | WUBNEH, BELETE ABEBE | |
| dc.date.accessioned | 2022-11-30T07:24:17Z | |
| dc.date.available | 2022-11-30T07:24:17Z | |
| dc.date.issued | 2022-02-08 | |
| dc.identifier.uri | http://ir.bdu.edu.et/handle/123456789/14615 | |
| dc.description.abstract | Lake Tana is located in the northwestern tropical highland region of Ethiopia. The Gumara River originates in the afro-alpine vegetation of the Guna mountains above 4000m.a.s.l. and flows to Lake Tana at 1784 masl. Gumara River is ecologically important as it is the migration habitat of fish of the genus Labeobarbus of the cyprinid family. In addition, twelve globally threatened bird species have been identified in Lake Tana and its associated wetlands. Most of the species are recorded in the Shesher and Welala wetlands which are part of the UNESCO Biosphere reserve areas. The riparian area is known to have more than 25 species of herbaceous medicinal plants and other species serving as construction and fuelwood source. Aquatic ecosystems are degrading as a result of changes in the natural flow due to landscape degradation, climate change, and water resources development. The alteration of natural flows affects the several services of the ecosystem for the local people who depend on them. Previous studies confirmed that there are advancements globally that the maintenance of flows in rivers help make water resources uses sustainable. Hence, knowledge about environmental flows is essential in conserving vigorous, prolific, and resilient aquatic ecosystems that benefit flora, fauna, and human beings. A study showed that in Ethiopia, as part of the Environmental Impact Assessment (EIA) especially for projects of water abstraction, environmental flow assessment (EFA) is being undertaken. The Abbay Basin Authority in its sub-basin master plan preparation has suggested that 10%–25% of river flow be allocated for the environment. However, the suggestion did not consider the flow variabilities and downstream uses of rivers and water bodies. In addition, 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 and social impacts at the watershed scale. Therefore, this study aimed to develop a conceptual framework for holistic environmental flow assessment method using an initial examination of flow-ecology-livelihood relationships for tropical highland rivers in the Lake Tana basin of Ethiopia. Flow data of Gumara River from 1973 to 2018 are used for the hydrological analysis. The ecological data were collected at 30 sites along the Gumara River on March 2016 and 2020 to look at linkages with hydrological condition. River hydrology for ecological data sites was estimated using the SWAT model and showed that the low flow decreased over time. The hydrological investigation showed that 1-Day low flows decreased from 1.55 m 3 s -1 in 1973 to 0.16 m 3 s -1 in 2018, and 90-Day (seasonal) low flow decreased from 4.88 m 3 s -1 in 1973 to 2.04 m 3 s -1 in 2018. Both physico-chemical and macroinvertebrate scores showed that water quality was moderate in most locations. The highest fish diversity index was in the lower reach at Wanzaye. Macroinvertebrate diversity was observed to decrease downstream. Both the fish and macroinvertebrate diversity indices were less than the expected maximum, being 3.29 and 4.5, respectively. The normalized difference vegetation index (NDVI) for 30 m and 60 m buffer distances from the river (as proxy to riparian vegetation) decreased during the dry season (March–May). Generally, based on this study, the low flows and large floods have decreased, and floods occur later in the season in the Gumara River. It directly affects the ecosystems and related human livelihoods dependent on ecosystem services. Because of the decrease in low flows and the resulting increase in zero-flow days, the resident fish species in the river are threatened. Historically, fish used the pools along the river to survive in the dry season. However, these pools have dried up due to pump irrigation. Additionally, the flood delayed by about 30 days, which delays the migration of Clarias gariepinus (Catfish) and the Labeobarbus species to the Shesher and Welala flood plain wetlands for spawning. Besides, submerged and emerged herbaceous plants and grasses in the Gumara river are disappearing, and water supply for livestock and humans is becoming problematic. The decrease in large floods makes it easier for the local population to cut the large riparian trees, such as Ficus vasta species for fuelwood and farm tools, and causes the trees to disappear. Sand mining has also become more prominent, significantly affecting the morphology thereby ecology of the Gumara River. Therefore, the relationship between flow vi alteration, the main ecological components, and related human livelihoods helps to understand the impacts of anthropogenic interference on aquatic and riverine ecology. Hence, a flow–ecology– livelihoods conceptual relationship was developed that can help in establishing a quantified relationship by building sufficient historical and spatial data in the river–wetland–lake system to inform science and policy. It is also recommended to select appropriate hydrological models for the basin to solve the shortage of data from monitoring sites and improve the quantification of environmental water requirement. Key words: Lake Tana, Gumara, Environmental flow requirement, Livelihoods, Aquatic Ecosystem services, | en_US |
| dc.language.iso | en_US | en_US |
| dc.subject | CIVIL AND WATER RESOURCE ENGINEERING | en_US |
| dc.title | DEVELOPMENT OF A FRAMEWORK FOR A HOLISTIC ENVIRONMENTAL FLOW ASSESSMENT METHOD FOR TROPICAL HIGHLAND RIVERS IN THE LAKE TANA BASIN, ETHIOPIA | en_US |
| dc.type | Thesis | en_US |
