Seleshi, Yilma (PhD)Wondye, Fanuel2018-06-182023-11-112018-06-182023-11-112009-10http://etd.aau.edu.et/handle/12345678/1226Despite Ethiopia possesses abundant water resources potential, second only to Congo in all of Africa, the country is at critical cross roads with large and increasing population, a depressed national economy, insufficient agricultural production and low no of developed energy sources. 83% of Ethiopians lack access to electricity; only 5 percent of irrigable land and 3% of the hydropower potential in the Blue Nile basin has been developed so far. Nowadays persisting drought and increasing competition for water have left Ethiopia with no more chance other than seeking solutions and assure sustainability of the resource. Even though Ethiopian portion of Blue Nile, Abay possesses a great potential of irrigation and hydropower developments, the financial and political constraints have long hindered the country’s development. This study aims at analyzing the effects of implementing the potential irrigation and hydropower projects that are contemplated in the country. Reservoir system simulation (Hec-ResSim) software has been used to study the out puts of executing different developments in the basin. This has been done by setting up the model and simulating for four scenarios including the base scenario referring to the current situation in the basin. After a curious filtering of all projects mentioned in the basin’s master plan and other project specific reports, 315,431ha (38.7% of total 815,581ha potential) of irrigation and 7,026Mw (89.6% of total 7845Mw potential) of hydropower potential; overall comprising 23 dams having a combined maximum storage capacity of 170.15Bm3 have been preferred to be analyzed and assessed using the model. After categorizing these projects under four scenarios; the simulation has been done based on 33 years (1960-1992) of monthly hydrologic flow series. vi This study under has indicated that If Ethiopia is to develop 315,431ha and 7,029Mw, the resulting decline in the cross border flow will be only 3,382.93Mm3 which is only 7.29% of the currently simulated (under current condition scenario,scenario-1) Abay discharge to Sudan which is 46,396.99 Mm3. Under this condition both Ethiopia and Sudan benefit from regulation of Abay by Ethiopian dams, in that it results in increasing of low flows, giving the whole system uniformity of balance, decreasing water escaping during flood seasons. As concluded from this study regulation works upstream in Ethiopia have resulted in a uniform monthly average flow of 3,584.51Mm3 throughout the year to Sudan. Currently as the base case simulation indicated, Sudan receives monthly average low flow of 1,233.54Mm3 through November to June which then turns to be increasing; August being flood month when 13,456.27Mm3 has been observed. In addition if Ethiopia is to develop 7,029Mw including hydropower projects on the tributaries, then some 38,385.81Gwh/annum of electricity will be produced. Even though Tana-Beles project imposes a big deal of inflow and power out put decline on the main stream hydropower plants, this power decrease was exceeded by the power generated at Tana-Beles power plant. Prior to Tana-Beles project Power output from main stream plants has been 34,284.23 Gwh/annum then increased to 34,736.14 Gwh/annum despite power decrease at Karadobi, Mabil, Mandaya and Border.enUsing Hec ; RessimThesis