Water Resource

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    ASSESSMENT OF THE RUN OF THE RIVER HYDROPOWER POTENTIAL AT THE DOWN STREAM OF KOKA DAM AND FORECASTING THE LEVEL OF FLOODING AT SELECTED SITE (CASE STUDY OF AWASH RIVER BASIN, ETHIOPIA)
    (Hawassa University, 2023-10-26) ASHENAFI AYZA ASELE
    Energy demand is increasing exponentially. This is because of rapid population growth, urbanization, the higher standards of living, industrial and agricultural expansion. Nevertheless, the available energy supply is not reliable due to sedimentation problem. So, it is advisable to use the nearby available natural resources (i.e. river and suitable topography) for potential assessments without adverse effect to cope with increasing and diversified energy demands. This study aims to investigate the assessment of river run of hydropower potential at 50km downstream of Koka Dam. To achieve the goal, Stream flow data were collected from 1991-2016 and height information was quantified from contour map and 3D spatial analyst tool in ArcGIS. Initially, the study was identified three possible potential sites and from these sites; site one was selected as the most prioritized site using MCDA method. The study included the Flood level forecasting at mostly prioritized site for further precaution using HEC-GeoRAS for preprocessing of geometric data and HEC-RAS for post processing of hydraulic modeling. Following the aforementioned model, methods and data the study computed the theoretical power at site one was (8981kw and 4197kw), technical power was (6960kw and 3253kw) and the annual energy output was (60.9GWh/year and 28GWh/year) are the maximum and minimum power at Q30 and Q95 respectively. The most preferred site had dependable flow of 19.71m3/s and is occur 95% of the year and the design flow was 42.17m3/s and is occur 30% of the year. The flood inundation area and the maximum flood depth at mostly prioritized river station 1100 where the study starts head measurement (i.e. upstream full reservoir level) and around 1km upstream of R.S. 1100 (i.e. at R.S.2050) were (145.79m 2 , 4.96m) and (204.09m 2 , 5.62m) respectively for 100 year return period. The validation of spatial information for site one tested were 0.71 for RMSE and hydraulic model performance for R.S.1100 and R.S.2050 were (0.7, -8.29 and 0.97) and (0.83, 5.92 and 0.96) for ENS, PBIAS and R for return period of 100 year and show the applicability of the model was good. To encapsulate we can get the site at 50km downstream of Koka Dam that have the capacity to produce annual energy of 60.9GWh/year. Consequently, it is possible to minimize the problem of highly increased and diversified electric demands at the target area. Hence, it is recommended that the government at national as well as local level or any other agency should look over it in detail and finding to implement thorough investigation of the area
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    FLOOD MAPPING ON GREAT AKAKI RIVER IN ADDIS ABABA, AKAKI KALITY SUB-CITY
    (Hawassa University, 2019-12-19) BERHANU BALTA HADARO
    In recent years, the patterns of flood across all continents have been changing and becoming more frequent, intense and leading the people to face risks. Therefore, the risk should be investigated and quantified properly. The objective of this thesis was to develop flood inundation maps of Great Akaki river in Addis Ababa, Akaki Kality sub-city. Streamflow, digital Elevation model (12.5*12.5 m) resolution and land use data were used as an input for the RAS mapper in HECRAS model. The 2D-HECRAS and ArcGIS models were used for mapping the flood extent, depth and velocity for various return periods. The Mann-Whitney and Wald-Wolfowitz statistical tests were used to hydrological data test. The basic assumption in statistical flood frequency analysis for its homogeneity, independency and stationarity of the time series at 5% significance level. The Easy fit 5.0 software was used to fit and identify the parent probability distribution for the streamflow data. The frequency analysis result depicts that Log-Normal probability distribution with 3 parameters best fitted the flood time series. The estimated quintiles for 2, 5, 10, 25, 50 and 100 years return periods were found to be 210.29, 333.04, 453.16, 626.19, 769.75, and 925.41 m3 /s respectively. The 2D-HECRAS model output indicated that about 86,123,156,228,285, and 350 ha land has been inundated for an event of 2, 5, 10, 25, 50 and 100 years of return period respectively. The 100 years flood magnitude inundated about 78, 272 and 34 ha of irrigated command area, swamp area and population settlement respectively. Flood risk map was developed based on hazard and vulnerability indicators. A preliminary alignment of structural flood protection dike was identified with length of 1.5km at downstream and 0.5 km at upstream of bridge which would make 95% of the settlement area on the left bank safe. The study has shown that the middle and lower part the study area is more inundated than upper parts. Therefore, the affected areas were whether to be free of infrastructure development, investment and residence of people or construct flood protection structure in order to avoid the risk of flooding in the area especially closer to the Great Akaki River.
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    PERFORMANCE ASSESSMENT OF STORM DRAINAGE SYSTEM, THE CASE OF WELKITE TOWN ,CENTRAL ETHIOPIA REGION,ETHIOPIA
    (Hawassa University, 2023-10-16) TAMIRAT AMDE
    Most storm water drainage problems investigated with respect to its hydraulic performance.In Wolikite town drainage structures are not well-designed to carryout the runoff due to blockage & capacity on size of the ditch.The objective of this study is ,to assess storm water drainage system performance of the town. The study employed both primary and secondary data collection. To achieve the specific objective HEC-RAS model analysiss has been used to calculate peak discharge and the averge rainfall using log pearson type III, in order to develop the Intensity Duration Frequency (IDF) curve for the rainfall intensities recorded in different duration and analyzed for a period of 1991-2021. Detail evaluation of drainage channels is required to control damages on high storm. For sizing of existing and proposed drainage channels manning formula is used and the hydrological peak flow was determined by using Rational Method. It was found the discharge using rational method is that 1.78mcu , and the result from the HEC RAS model 0.08mcu compared with existing hydraulic capacity of the channels . It shows that study area storm water was higher with respect to the drainage channels to carry the expected runoff during high rainfall events, make incapable to carry the runnoff for drainage ditches of the study area. To resolve these problems BMP’s have been recommended and finally, the analysis from this study permits future work on re design of the town storm drainage ditches and resettlement of flood affected areas and amend land use of the town for residential should be considerd in connection with town master plan development
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    DAM BREACH MODELING and INUDATION MAPPING A CASE STUDY OF JEMA DAM, ABAY BASIN, ETHIOPIA
    (Hawassa University, 2018-08-13) AMDEMARIAM SHIFERIE MULU
    Preparing dam safety plans and hazard management strategies are unquestionably vital, since lots of human lives have been lost and tremendous amount of economic crisis have been recorded from dam failure events throughout the world in history. Setting out risk management, emergency action plans or evacuation planning system to protect both lives and materials during sudden dam failure phenomena and resulting flood waves is highly essential. This thesis analyzed the probable failure of a dam under a set of pre defined scenarios, within the framework of a case study, the case subject being the Jema dam located at Amhara Region of Ethiopia. A probable maximum flood of Gilgel Abay river (tributary of Jema River) has been computed using Hershfield’s technique .Breach parameters prediction, peak outflow hydrograph were determined by HEC-RAS model based on available technical and geometric data. Different maps such as flood areal extent map, flood depth map and velocity map have been produced by HEC-GeoRAS. The worst scenario was found to be scenario three (when Jema dam failed by overtopping with PMF of Gilgel Abay River). Probable maximum flood of Gilgel Abay river by Hershfield’s technique was found to be 1726.28 m3 /s. The maximum breach discharge resulted from HEC-RAS model was 79,886.37m3/sec and the maximum area inundated by this flood in downstream was found to be 41.6km2 . The areal maps show that the part of command area at right side and farm in left side, Bikolo Abay Town and settlement villages to be prone to flooding. The depth and velocity of flood also depict that the downstream rural village near the river bank are under extreme hazard category and the maps reveals that Jema dam is categorized under high hazed dam