Browsing by Author "Hailu, Dereje(PhD)"

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    Daily Rainfall-Runoff Modelling of Upper Awash Sub Basin Using Conceptual Rainfall Run off Models
    (Addis Ababa, 2010-12) Gobena, Sileshi; Hailu, Dereje(PhD)
    Hydro-meteorological data are very indispensable for the assessment and development of water resource. Upper Awash (UA), part of Awash River Basin, is densely populated and large population growth as well as the expansion of development activities and large farms such as flower farms in the region is expected to put further pressure on the water and associated resources of the area. Moreover, every hydrological process in the upper Awash has effect on the development activities in the downstream of the basin which calls for huge water resource planning and management activities. In this study, a daily rainfall- runoff modeling which is very helpful to further strengthen assessment, planning and management of water resource in the basin was conducted for selected three catchments of Upper Awash Sub Basin using two models namely AWBM and SMAR models among five lumped conceptual models nested in rainfall-Runoff library. Automatic calibration and verification of the models were performed using Genetic Algorithm optimization method together with Nash Sutcliffe criteria and runoff difference as primary and secondary objectives respectively. In connection with this, flow generation, model parameter determination, a comparison of observed and simulated flow as well as comparison of performance of the two models were conducted. The quality of fit between the observed and simulated flow is judged by reviewing plots of the hydrographs. Comparison of the observed and computed flows reveals that except for the extreme peak flows the medium flow and low flows are generally modeled quite satisfactorily. Further more, performance of the models is assessed by using Nash Sutcliffe criteria and comparing the annual total flow volume and the maximum peak flows. Both AWBM and SMAR models predict the flows fairly well with overall Nash Sutcliffe criteria of 0.6 to 0.85 for both calibration and verification periods except for Mojo catchment. As far as the performance of the two models concerned, AWBM gives better results as compared to SMAR model for selected catchments. In addition, Model sensitivity analysis was undertaken to analyze the sensitivity of a particular model parameter with regard to a selected objective function and subsequently the most sensitive parameters for the two models were determined. Finally, based on the results obtained the necessary conclusion and Recommendation were drawn. Generally, conceptual models have given encouraging results in this sub basin but further detail work is required verify the performance of the models under strict quality data situation.
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    Linking Small-Scale Irrigation and Household Food Security in Drought Prone Area of North East Ethiopia: A Case of Alawuha Irrigation Scheme, Gubalafto Woreda, and North Wollo Zone
    (Addis Ababa University, 2011-06) Kebede, Getinet; Hailu, Dereje(PhD)
    In north eastern part of Ethiopia, drought induced food insecurity has been a long-lasting problem. In this thesis, an attempt made to identify household food security status and its determinants in one of drought prone area- Gubalafto Woreda. Moreover, the linkages between Small Scale Irrigation and household food security in provision of food energy assessed. A multi- stage stratified sampling procedure was used to select 115 sample households from both irrigation users and non-users living within the targeted kebeles. A combination of quantitative analysis like descriptive statistics, Household Food Balance Model, binary logit model and qualitative study were used to reach at reliable results by using data gathered from both primary and secondary sources. The survey result revealed that 29 % of sample households were food insecure and 71 % food secure. There is huge gap in food calorie availability ranging from 788- 8405Kca in the study area. Food insecure households were found to have an average of 24% food gap in terms of dietary energy, which is needed to fulfill the national minimum requirements. The average per capita calorie supply for irrigation users was found substantially increased by 889 Kcal, which is about 42 % percent of the minimum requirement of food calorie requires by an individual. The use of SSI was found significantly related to household food security situation in provision of household dietary energy and taking a lion share in the proportion of study areas major consumable from food crops production. The logit model revealed that household size, educational status of household head, number of farm oxen, cultivated land size, engagement in non-farming, access to irrigation and credit service were found significant determinants. Correspondingly, the study disclosed that the long distance between irrigated land to farmers residence, lack of cleaning and maintenance of scheme, free grazing , poor irrigation methods and crop selection were the major constraints in the irrigation farm. SSI is one of the viable solutions to household food supplement and hence promoting of smallholders to produce directly consumable food grains is advantageous. It is important to address those food security determinants and farmers’ views in planning and executing of development policies and programs by all stakeholders to tackle the problem of household food insecurity in the study area
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    Tandem Reservoir Operation of Cascade Hydropower Plants Case of Genale - Dawa River Basin
    (Addis Ababa University, 2014-09) Dejene, Tsegazeab; Hailu, Dereje(PhD)
    Genale – Dawa river basin is one of the twelve river basins in Ethiopia with catchment area of 74,010 Km2 and has the third largest surface area (about 170,000km2) after Wabishebele and Abay River basins. Genale-Dawa river basin has an estimated hydropower potential of 9,300 GWh/year and is expected to contribute about 5.8% of the total estimated potential of the country. Out of the nine large scale hydropower potential projects in the basin, this study deals with the optimal operation of the cascade hydropower plants namely, GD-3, GD-5 and GD-6 that are located on the main river channel of Genale River. The upper most hydropower plant, GD-3, is already under construction and the other two are under study. The latest version of HEC-ResSim (Version 3.1) introduced by U.S. Army Corps of Engineers in 2013 is used to simulate the multi-reservoir system network. The physical and operational data are obtained from previous studies of these projects and used as input in reservoir network module of ResSim Model. Implicit (default) and Explicit (user defined) system storage balance has been used to get the maximum power and energy and plot the optimal guide curve so as to be used by the operator to attain the optimal overall energy generated from the system. The explicit system storage balance has generated a better power and energy for the reservoir system. The study showed that, when the individual hydropower reservoirs deliver energy and capacity into a common power system, operating the projects as system has produce more average energy or firm energy than the sum of individual projects operating independently. The maximum overall average energy of the system found in this study is 4417.7GWh/yr. Comparing with the feasibility study, the proposed model is capable to produce an extra amount of 487.7 GWh average electrical energy (a 12.4% increment) annually. The optimal guide curve denotes that there is a tendency, in the optimal explicit system storage, to leave more water from GD-3 reservoir and prepare the storage to hold more water during high flood seasons. The water released from this reservoir can generate additional power at the downstream power plants. The reverse is true for the operation of the downstream power plants. The pool level of GD-5 is almost in the flood zone except for the first three months, January to March, where the pool level is in the active live storage zone. In GD-6 the reservoir pool level is in the flood zone throughout the year.