Hydraulic Engineering

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2D Hydrodynamic Modeling of Rib River Flooding
(Addis Ababa, 2011-10) Shiferaw, Muluken; Michael, Yonas (PhD)
Flood occurs repeatedly in Ethiopia and cause tremendous losses in terms of property and life, particularly in the lowland areas. The majority of flood disasters’ victims are poor people living in nearby stretch of floodplain. Therefore, the study was carried out to perform floodplain analysis and risk assessment of Fogera and nearby areas. This research involves the integration of 2D Structured Mesh Generator (CCHE-MESH) and hydrodynamic numerical model (CCHE2D model) with Geographic Information Systems (GIS) to develop a regional model for floodplain determination and representation. The study describes the flood extent and depth in the area for flow condition derived from the historical flow data of the Rib River. Triangulated Irregular Network (TIN) was prepared from shape file generated from spot elevations of the floodplain through field survey data and the DEM of the study area in ArcGIS. Triangulated Irregular Network (TIN) is converted to an ASC II format, which is supported by the CCHE-MESH and CCHE2D model. Boundary condition for the inlet is specified as total discharge and discharge hydrograph for steady and unsteady simulation respectively and for the outlet a constant water level of Lake Tana (1788m) is specified as a downstream BC which allows for simulation of the free flow condition at the river outlet. Initial conditions are defined based on information on gauges or through introducing a so called warm-up that precedes the actual simulation period and boundary conditions are generally specified from hydrometric data such as time series data of discharge and stage or simulated discharge hydrograph. Maps of flood Extent, Level, Depth and Velocity are developed using 100 years return period flood. The Flood has the inundation area of 47.13km2 while the simulated flood extent has flood depths less than 5.9m. The depth between 5.9m and 2m is located along the river channel and on the pond which is located south of the rib river. However, the depths below 2m exist largely on the flood plain which extend 4 km and 3 km outside right bank and the left bank of the main river respectively. The simulated water level ranges between 1798.4m ASL at the upstream and 1788m ASL at the downstream end of the main river. The simulation result indicates much of the flooding occur in the middle part of the river where the flow behaviour is mainly dominated by the inflow from the Rib River. Most of the areas around the flood plain are cultivated land with less proportion of Agro-pastoral, Marsh and Pastoral. 85-90% of the flood inundated areas are covered by agricultural land. The remaining 10-15% is covered by Agro-pastoral near inlet to Lake Tana.
Abay Basin Water Allocation Modelling Using Hec Ressim
(Addis Ababa University, 2009-10) Wondye, Fanuel; Seleshi, Yilma (PhD)
Despite 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.
Actual Evapotranspiration Estimation Using Remotely Sensed Data and Hydrological Model: A Case Study Of Gilgelabay Catchment
(Addis Ababa University, 2015) Genet, Abdi; Dereje, Hailu (PhD)
In order to get reliable qualitative and quantitative information about a potential of water resource in a catchment it is important to assess and evaluate the spatial and temporal variation of actual evapotranspiration by applying SEBS algorithm and SWAT hydrological model and eventually compare with MODIS ET. This is one of the motivations for evaluating the spatial and seasonal dynamics of actual ET for the Gilgel Abay catchment using energy balance algorithm and hydrological model. Spatially distributed actual evapotranspiration (ETa) values were estimated using Surface Energy Balance System (SEBS) approach and the Soil and Water Assessment Tool (SWAT). The input data for SEBS and SWAT were acquired from different sources with different spatial and temporal resolutions. The dynamics of ETa was assessed only for the selected dry years (2009) and wet year (2005 and 2007). Moreover, the analysis was based on the nine selected days of those years having a cloud cover less than 30%. The estimated ETa values were also compared with MOD16 ET at sub-catchment scale. SEBS based estimated daily actual ET eventually were compared with MODIS ET and SWAT actual ET estimates to assess the temporal and spatial variability in the catchment. The result showed that the mean value of SEBS daily actual ET during those days reached up to 5.9 mm/d (Jan-01-2005), 5.5mm/d (January 10, 2007) and 5.1 mm/d (March 12, 2007). In distinction as it observed from the results during wet season days the SEBS estimated actual ET is relatively lower and highly variable spatially. The mean actual ET for day of the year [DOY] 253- 2009 is 8.8 mm/d, DOY 336 - 2007 is 5.8 mm/d and DOY 330- 2009 5.1 mm/d which shows the spatial variability resulted due to heterogeneity of the vegetation cover during the wet season. Similarly, the long-term mean annual actual ET derived from previous hydrological studies using SWAT compared well with MODIS ET over the terrestrial part of the catchment. The evaluation of the wet season actual ET from 2000-2010 from MODIS and SEBS was compared with SWAT and the result showed that a good correlation. Thus, overall MODIS ET product showed good agreement with results from the SWAT models both in magnitude and spatial variability
Adama Flood Problem –Flood Risk Mitigation Option for Boku Shenen Area
(Addis Ababa University, 2016-04) Aychiluhim, Merid; Nigussie, Agizew(PhD)
Flooding is becoming a usual event that occurs in urban and rural areas. It is an interaction between mankind and nature. A city like Adama is nowadays becoming a flood prone area. A flood that comes from the adjacent watershed area seriously affects the low lying areas as seen at Adama – Boku shenen Kebele. Boku Shenen kebele is one of a flood prone area of Adama city every year. Four different watershed catchments that produce flood exist around the kebele. Because of lack of integrated flood risk management system; loss of lives, displacement of people, and destruction of social infrastructures are becoming increasing from time to time. Adama has been vulnerable to flash flooding from rainfall, in particular of the ungagged Kersa and Golba Tegene catchments which pass through South East of the city. It has not been tried to estimate the amount of flood and not recommended mitigation options based on the natural situation of the area previously. Hence, this thesis is to identify peak flood and recommend mitigation options based on the environmental and geological situation of the area that can be affected by extraordinary floods. This thesis tries to consider more options and fills the gaps not covered by others adopting more than four application soft wares like Easy fit, ArcGIS, Global Mapper and AutoCAD. Specially, peak flood discharge estimation and recommend mitigation measures selection method believed to be the gap not properly covered in the previous flood risk mitigation works. The data usage for this thesis tried to make very intensive by considering different data options like gridded (DEM and contour), digitized (soil type, land use and 1:50,000 scale map) and rainfall data. For precipitation modelling, ERA Intensity-frequency-duration curve was used for frequency storm and for the gage weights annual maximum daily rainfall for 24 hours and 6 hours duration storm are used since flood estimation requires a properly recorded data more than 30years from metrological stations. For the study area, I just used a rain fall data of 62years of record from Adama meteorological station. 30m x 30m resolution DEM for catchment was used to delineate the watershed area using GIS. In this thesis, the flood magnitude estimated for a 100years return period was computed by using SCS excel model method for Kersa and Golba tegene catchments and flood mitigation option selected to be detention pond incorporating the designing criteria. Adama Flood Problem-Flood Risk Mitigation Option for Boku Shenen Area 2016 Detention pond/dam was designed for both catchments. For Golba Tegene catchment, after analyzing the area of the reservoir/pond, having 8m of dam height 130962 m3 volume of flood can be absorbed/held which a 25 years design flood is. The spillway was designed for 100years return flood and can spill maximum of 5.586m3/s routed discharge. For Kersa catchment, a controlled local pond type of 3m height at 8584m2 and hence 26421m3 volume flood could be held which is also a 25years design flood. It also has spillway and controlled outlet gate that can discharge a maximum of 0.78m3/s. After the junction point of the two gullies a maximum of 6.36m3/s discharge could pass through the existing gully. However the existing gully was modified so as to accommodate safely the maximum 6.36m3/s discharge. In doing so, this thesis will help and become an input in flood risk mitigation process. It will benefit the study area community directly where as any others can be benefited indirectly.
Adopting Landscape Infrastructure to Integrated urban Stormwater and Wastewater Management
(AAU, 2017-06) Feyisa, Nibo; Agizew, Nigussie (PhD)
The main goal of this study is to evaluate the existing urban wastewater and storm drainage management system and made recommendation on best selected alternative option of integrated urban wastewater and storm drainage management system. Any technical wastewater and stormwater management system adopted in urban drainage based on prior quantitate design discharge estimation. This study contributes a lot to understanding of the integrated urban water management system key technique to minimize the diffuse pollution load into natural stream, to reduce point source/wastewater discharges and to preserve the hydrologic regime of natural drainage systems. Wastewater and stormwater flow discharge are analyzed based on the three-part methodology. The rainfall of 100, 50, 25, 10, 5 and 2 year annual exceedance probability meteorological method was simulated SCS unit hydrograph rainfall-runoff using HEC-HMS. The calibration result indicates basin parameters were used in HEC-HMS model is improved. Different scenarios for landcover change were evaluated for all rainfall frequency models. The frequency storm of 25 year return period produced the maximum peak discharge at the outlet found 209m 3 /s in 1995, 238.1m 3 /s, in 2002 and 262.6m 3 /s in 2009. The hydrological response indicated that with urban area increase by 24.95%, an increase in peak flow. This study shows that peak discharge increase in 13.87% in period 2002, 25.64% in 2009 compared to period of 1995 as reference. The storm drainage management infrastructures are not updated – not sufficient to the peak discharge. Flooding impact on streets, and public property damage were reported in every year. The wastewater generation from domestic, industrial, public and intuitional have direct relation water supplied and 80% of water used is changed to wastewater. Monthly billed volume of consumed water from 2011 to 2016 was evaluated to determine domestic per capita demand. The average per capita demand is found 26.74l/cap/day. Per capita demand by mode of service were found 89.2L/cap/day for High Consumption, 41.48 L/cap/day medium consumption , 21.06 L/cap/day low consumption, and 9.88 L/cap/day very low consumption. From these demand estimation the total wastewater flow rate are found 2898.9m 3 /day (0.0334m 3 /s). Only 255m 3 /day (4%) of sewer facilities is existed for wastewater management system. These infrastructures are limited to only to onsite sewer line connected to the flash toilet, off-site pitlitrine discharged to treatment plant. GIS specific landscape Suitability assessed where specific practice to place, i.e. integrated urban water management system like stormwater best management practice and Wastewater Generation Reduction. The evaluated stormwater best management practices selected is Sediment Basins, Sand Filters Pervious landscape Pavements, Bio Basins, Infiltration, Ponds and Lakes, Swales & Buffer Strips, Bio Swales, Constructed Wetlands. For wastewater reduction the selected are Stormwater Harvesting/Reuse, Rainwater Tanks, Changing Landscape Form and Water Use Education Programs.
Agricultural Water Management Modeling and Analysis Under Climate Change and Land Transformation (A Case Study of Lower Omo Ghibe Basin)
(Addis Ababa University, 2018-05) Natan, Molla; Daniel, Fikreselassie (PhD)
Human activities and climate factors both affect the availability of water resources and the sustainability of water management and that in turn affect agricultural water management especially in already dry regions, water has become scarcer with increasing requirements from growing population, economic development. Although progress has been made in understanding variability of runoff, the impacts of climate variability and human activities on agricultural water management (actual evapotranspiration) and (discharge accumulated in the river network) remain less well understood. South omo Gibe basin which is one of the sub basin in Ethiopia has suitable land water resource for agriculture for both farm and livestock and currently huge investment are found on irrigation project, and from these the dominant is state owned irrigation like kuraz sugar development irrigation project in the sub basin which planned to irrigate sugarcane on 175,000 hectare of land. According to works design and supervision enterprise that prepare design document of the project the water requirement of the plant is modeled with cropwat considering only atmospheric water demand and put the yield in figure in its report. However now a time In south Omo Gibe sun basin a frequent happening of high and low rainfall, less work on soil conservation practice and deforestation are observed as causes of changing of climate and land degradation that make the need for improved and resilient agricultural water management to have greater yield of the crop with environmental sustainability and so efforts towards improved and resilient agricultural water management is must. Therefore, the main objective of the research presented here is to study the effect of climate change specifically drought and land degradation on water demand and crop yield in the area of study and compare the existing crop oriented model used for the design of crop water requirement of the crop in the project area with agro hydrological model for better irrigation management under climate change and land transformation. To achieve this purpose, an available code that takes into account the interaction between soil, water, atmosphere and plants SWAP model is used after assessing the challenges in the sub basin and identifying adaptation strategy for improved agricultural water management and compared with Cropwat model. consequently, it is tried to analyze the impact of future climate changes and land transformation water demand for irrigation and relative crop yield in the Kuraz irrigation project area. From the result of the performance of the two model SWAP model result of actual evapotranspiration and irrigation water requirement is greater than the designed crop water requirement of cropwat model output which can be calibrated with yield of sugarcane. And the comparison of the two models shows that SWAP model outputindicate the actual evapotranpiration and irrigation water requirement is greater than the CROPWAT model output f the designed irrigation water requirement that can make conform with yield reduction of sugarcane the in project area as a calibration method due to shortage of data. Even though the reduction of sugarcane is happen due to technical inefficiency as I can get the result of research paper on irrigation management practices in kuraz irrigation project, climate change and land degradation plays large effect in this technical inefficiency of irrigation water management more than different tillage practices. in this research due to shortage of data to measure soil moisture and ground water data in the project area I used the yield reduction data from analysis of technical efficiency sugarcane production. From this result neglecting other factors that decrease the yield of sugarcane and considering the effect of climate change and land degradation only, it shows the need of irrigation water will be high to maintain good yield of sugarcane in the future. Today, the sugar corporation supplies 300 m 3 /sec which is the minimum release discharge from Gibe III hydropower project. This means that the corporation should focus on works that increase the amount of water for irrigation in the future. Consequently, taking into account all the simplification and the uncertainties in the model, it is safer for the corporation to increase the water supply capability in the future, particularly using a better approach of soil and water management integrated with sub basin scale soil and water conservation practices should be followed, in order to cope the increasing water demand in the future.
am Breach Modelling and Flood mapping, a Case Study of Ribb Dam
(Addis Ababa University, 2021-01) Fasika, Worku; Daneal, Fikreselassie (PhD0
The spontaneous dam breach phenomenon and the resultant flooding that happened in the world history leads to the requirement of establishing a dam safety plans and hazard management strategies. In this regard, the dam breach pre-event analysis will be the prerequisite work. This thesis addressed a pre-event analysis of a dam breach scenario for Ribb dam located in Amhara regional state, Ethiopia. Deterministic and probabilistic approach for the modelling of the dam breach is used. Overtopping and piping failure modes are assessed and the resulting flood inundation is mapped. A 1.5 PMF inflow hydrograph and a base inflow hydrograph are used as upstream boundary condition, while Lake Tana makes the downstream boundary condition. Fourteen 2D simulations are carried out and of which ten are for different breach parameters, two are for uncertainty analysis on breach parameters, and two are sensitivity analysis on Manning’s roughness coefficient ‘n’. HEC-RAS Ver 5.0.7 hydraulic model is employed, and McBreach is used for probabilistic dam breach modelling. In this study, five deterministic non-physical empirical methods and probabilistic breach modelling are assessed and compared. The five deterministic non-physical empirical methods have resulted in peak flow values between 67,570m 3 /s and 113,153m 3 /s for overtopping and between 22,269m 3 /s and 40,926m 3 /s for piping modes of failure respectively. For both modes of failure, MacDonald and langridge-Monopolis and Frohelich (1995a) produced the lowest and highest peak discharge respectively. The 1% and 90% exceedance probability peak discharge for overtopping failure mode is 104,379m 3 /s and 77,521m 3 /s respectively. The Manning roughness coefficient ‘n’ sensitivity analysis showed a 0.11 to 39.9 percentage increase in flood depth and 2.20 to 20.67 percentage decrease in velocity for an increase of the Manning roughness coefficient by 30%. In addition, the Manning roughness coefficient ‘n’ sensitivity analysis showed a 0.00 to 15.32 percentage decrease in flood depth and 10.81 to 28.09 percentage increase in velocity for a decrease of the Manning roughness coefficient by 30%. The study highlighted the dam breach and its corresponding flooding could be potentially catastrophic and high priority should be given to monitoring and surveillance of the dam.
Analysis & Evaluation of Hydraulic Parameters in Akake Well Fields of Addis Ababa
(Addis Ababa University, 2016-05) Dereje, Endalkachew; Mebruk, Mohammed (PhD)
Declining water levels caused by withdrawals of water from well in Akaki , the southern part of Addis Ababa have raised concerns with respect to the ability of the aquifer system to sustain production . As the aquifer of akaki in particular is heavily used in this area , understanding the hydraulic parameters of the area is essential for efficient sustainable management of the groundwater resource . A single well test was conducted to estimate the hydraulic parameters of the aquifer. An overview of the hydraulic parameters estimated for the 12 wells in the study clearly show strong evidence of inappropriate estimation. Thus this study was conducted to identify the possible miss-interpretation of the observed time-drawdown , step-drawdown , timeresidual drawdown based parameter estimation . After data quality checking , appropriate data correction for partial penetration and unconfinedness (if exists) were conducted. Then the standard methods like Theis curve fitting, Cooper-Jacob methods for timedrawdown data & Theis recovery method for time-residual drawdown data were used for parameter estimation. Beside Aquifer test v3.5 software was also used to verify the results of the original study. Evaluation and analysis result showed that out of the 12 well analyzed , 11 transmissivity values used in the well yield estimate were overestimated (on an average of twenty times ) and one underestimated (fivefold) , such highly over estimated transmissivity value misleads the designers & operators in fixing the well yield . Therefore, in this evaluation it is recommended to conduct multiple well test to determine the actual hydraulic parameters of the aquifer in order to obtain the safe yield of the wells which is intended to prolong the productivity of the aquifer and to delay excessive loss of saturated thickness .
Aquifer Property Evaluations and Sensitivity Analysis of Akaki well Field, Central Ethiopia
(Addis Ababa University, 2018-10) Hawi, Gudeta; Asie, Kemal (PhD)
Groundwater is essential resource which used in many aspects of life activities. Ethiopia has abundant potential of groundwater resource and in resent two decades the development of this project is increased. Addis Ababa water demand highly increases due to fast population growth, urbanization and industrialization. To supply this need the Akaki ground water well is one of the well field which can meet more than 30% of water supply demands in Addis Ababa. However, a number of wells in Akaki well field get dry and become unproductive. Therefore, this study aims to evaluate and analyses the performance and aquifer parameters (transmissivity and storativity) using the theoretical model: Cooper-Jacob method and Theis Recovery method with corrected observed time-drawdown, step-drawdown, time-residual drawdown or recovery data. The evaluated result shows, most of aquifer transmissivity is underestimated and few of it overestimated when it compared with WWDSE report. Again, to analysis sensitivity of the aquifer of the study area it modelled by MODFLOW through different scenarios of-50%, -25% decrement and +25% and +50% increment of discharge and hydraulic conductivity. Also, by discounting general boundary head, constant head, rivers and Akaki well phase IIIA extraction analysis are taken. Accordingly, the aquifer system of Akaki well fields is more sensitive for the probable change of the hydraulic conductivity special during the reduction of ability to permit water through it. Concerning on the water budget of each scenario for ignorance of water packages, the simulated head of area is more sensitive for Akaki river ignorance and as the Akaki well field phase IIIA stop water pumping the other well field phase start to rise, this show the cone of depression is extended up to the phase IIIA field area and this implies there is the well interference between the phases. Those result suggest that un safe yield of water rate costs the high depletion of the water level which cause to the drying of wells and ground water depletion where ground water extracted at rate faster than it can recharge (hydrological imbalance) and sustainability of the resource is under risk.
Arjo Didessa Reservoir Water Evaluation and Allocation System
(Addis Ababa University, 2018-10) Ebisa, Abiram; Dereje, Hailu (PhD)
The Abay basin is one of the Ethiopian basins endowed with abundant surface water and groundwater resources that require proper management and have to be wisely utilized in a sustainable manner. Didessa River is one of the tributary of Abay basin. Evaluating the seasonal variation of this river will provide management and fair distribution of water resources in Didessa catchment. Currently Arjo Didessa earthen dam is the reservoir found in the Upper Didessa River being utilized for Irrigation uses and in addition to irrigation uses different water users are found in Didessa catchment that will gain water from the same source. For this reason it needs evaluation and planning of the Didessa river water. To address water resources fairly to all users requires technical issues and specialized tools Arc view GIS tool to obtain hydrological and physical parameters and spatial information, Global Mapper to manipulate the DEM data in line with the shape files of the river basin and WEAP (water evaluation and planning) model to assess the consequences of climate change and irrigation expansion on current and future water use practices of Arjo reservoir. Records of hydrology and meteorological data have been statistically tested and arranged as an input data source to fit the model. Meteorological and grid climatic data were correlated with multi-regression and distribution mapping (DM) method respectively. The demand and the supply of water resource, baseline data and the future development activities of the area were compared using the mainly two different scenarios climate change and irrigation expansion. This study analyzed the model calibration, validation and its statistical measure were seen and the result shows that it is very good and the model can simulate the current and the future scenarios. After all of this done, the results revealed that unless the minimum flow requirements are maintained, the future irrigation demands are unmet in more or less. Due to the climate change the volume of reservoir evaporation in the (2016-2030) period was increased by 1.5%, in 2031-2050 periods was increased to 3.1%, and 2051-2080 period was increased to 4.3% when comparing with the current scenario. While compared with the baseline period, the first 15 years reservoir evaporation will increase but the Arjo Didessa Reservoir water has full supplement. There should be more detailed water resource management activity, including sustainable abstractions. In addition to this, the new projects on the study area have to construct for additional demand supply or supply with irrigation expansions
Assesment of Welkite Water Supply System in Gurage Zone, Snnpr, Ethiopia
(Addis Ababa University, 2016-05) Behute, Majer; Sahilu, Germew(PhD)
The thesis paper focused on the water supply system of Welkite town, capital city of Gurage zone of Southern Nation Nationality People Regional State of Ethiopia. The main objectives of this study is to identify the problems of Welkite water supply system by assessing, bursting and leakage problem of the pipe system, evaluate and compare the total demand and supply and to suggest some remedial measure. The demand and supply coverage was evaluated depend on different supply level and the level of leakage evaluated as per the amount of production and consumption. Moreover, to analyze the existing water distribution system, a model was developed by using Water CAD software. The model can be used to identify the zone of high pressure and low pressure in junctions and the level of velocity through pipe. In addition, sample pressure filed data used to compare with the simulated value. The model run was performed for average, maximum, peak and low demand scenarios to analyze the system model. The analysis result shows the domestic and non-domestic water supply coverage of the town is 52%. Hence, this result indicates that there is high gap between demand and supply. In addition, from three years obtain data of production and consumption the average loss become 19.27%. Furthermore, the model analysis result shows that different problems of the system. These are aged pipes, oversized and undersized pipes, high pressures and low pressure. Hence, the maximum pressure occurred at gravity main pipe line in night demand is 284.78m which is above the recommended value and the reason of pipe burst at gravity main pipe line. To handle the problems need providing additional pump to increase the production, rehabilitate the existing bore hole, maximizing the capacity of distribution pipe line and providing separate pipe line for rural community. Moreover, As for bursting of pipe, suitable anchoring, treating the system by using quality joints, changing pipe in same critical points and fixing air release valves should be done. Key Words: Water Cad Model, Non-revenue Water and Calibration.
Assessing Rainwater Harvesting as an Alternative Source of Non-Domestic Water Supply: Case Study at Jemo-1 Condominium
(Addis Ababa University, 2017-06) Mengistu, Daniel; Tsegaye, Wondmyibza
Water supply systems in Addis Ababa provide service to approximately 55% of the demand. Simple mechanisms that address urgent problems had to be used to supply citizens with water. Rainwater harvesting (RWH) systems have been in use since ancient times, and these days its use is increasing. Rainwater catchment systems are simple solutions that can be adopted in many parts of the city; many houses are already equipped with storage tanks and catching rainwater would require only a basic catchment system and make the most from the natural resources available. Rainwater harvesting is one option worth analyzing for Jemo-1 condominium site. The total area of the study catchment is 111,030 m2 which is composed of 333 blocks (the total area of 1 block is 290 m2) and 50 communal (the total area of 1 communal is 266 m2). From this 107,442 m3 of water will be collected in a year but this will satisfy only 18.45 % of the total non-domestic water demand. In this study, household scale rainwater catchment systems were analyzed, where water can be channeled through pipes installed on each building roofs. The pipes transport water to aboveground reservoirs. Precipitation data for Jemo-1 was used to determine the amount of water that can be collected. In the end, all aspects were analyzed to determine whether this could be a solution worth implementing in Jemo-1 to alleviate water scarcity problems as well as the possible positive and negative impacts it would have on the economy, society and the environment. It has also been tried to design the RWH components based on design criteria. Based on the design and analyses performed, it becomes clear that rainwater harvesting is not the only solution that will solve all water scarcity issues in Jemo-1. Storage tanks need to be much larger, precipitation has to be more abundant, roofs need to have a bigger area and tanks need to be cheaper for it to be the major source of water supply in the area. Key Words: Rainwater Harvesting, Jemo-1, Catchment, Non-Domestic Demand, Daily Per Capita Demand, Observatory Station
Assessing Surface Water Potential and Water Demand in Genale Dawa River Basin
(Addis Ababa University, 2015-12) Araya, Tilahun; Kemal, Asie(PhD)
This study is intended to quantify the amount of surface water potential leaving the entire basin (Genale Dawa) as surface runoff and water demand considering the large scale projects in Genale Dawa river basin which covers an area of 168,000 km2. Land use, land slope, soil and hydro – meteorological data were used to characterize the hydrology of the study area. Soil and Water Assessment Tool (ArcSWAT) model was used to determine the surface water potential leaving the entire basin as surface runoff in mean annual basis while for the water demand assessment Water Evaluation and Planning (WEAP) model was used. The estimated mean annual precipitation of the basin is 810.5 mm. The estimated mean annual actual evapotranspiration is 469.8 mm while the estimated potential evapotranspiration is 1304.4 mm. The estimated mean annual runoff leaving the entire basin is 6.37 billion cubic meters which corresponds to 37.92 mm mean annual runoff depth. The source of surface water availability is directly surface runoff generated from the catchments of the area as there are no water islands or lakes in the basin. The water demand assessment was done for only selected large scale irrigation, hydropower and water supply projects. Two large scale irrigation projects, one large scale hydropower project and five water supply schemes were selected. The five water supply schemes were intended to serve 143,865 people in the base year. The water supply demand is very small as compared to the irrigation water demand. The irrigation water demand covers 98.13% of the total annual water demand for all demand sites. Both water supply and hydropower take 1.87% of the total annual water demand in the current account year 2013. But the water supply and hydropower demand coverage increased to 2.84% of the total annual demand in the year 2025 due to fast population growth. Keywords: ArcGIS, ArcSWAT, WEAP, Water Demand, Runoff, Genale Dawa River Basin
Assessing The Effect of Land Use Change on The Hydraulic Regime of Lake Awassa
(Addis Ababa University, 2010-06) Daniel, Shewangizaw; Yonas, Michael (PhD)
For the past years an increase in population pressure, government policy and external influences caused a consistent change in the land cover of the Lake Awassa catchment. This was mainly by deforestation as is the case in many other areas of Ethiopia as well. The effects of land cover changes have impacted the water balance of the catchment by changing magnitude and pattern of runoff, peak flow and ground water levels. This study is mainly focusing on the assessment of hydrological response due to the land cover data of 1965 and 1998 and Geographic information system (GIS) integrated with the hydrologic modeling. The result of remote sensing assessment on the land cover of the catchment indicated that Natural Vegetation decreased by 11,768 ha or 9.06 % between years 1995-1998. This was mainly due to mainly the expansion of agriculture and urban area. Plantation expansion was 20,661 ha or 13.56 % and also urbanization increased by 1,310 ha or 0.89 %. Based on this result, the inflow records were analysed statistically to evaluate if change in the land cover affected the hydrological response of the catchment. The result of the analysis indicated that the average inflow to Lake Awassa in 1998 is 3.15 m3/sec or 99.34MCM, where as in scenarios year 2017 the average inflow result is 3.5m3/s or 110.38MCM. so because of the land cover change the flow increased by 0.35 m3/s that is 11.04MCM.
Assessing Water Conservation and Demand Management Option for Addis Ababa City
(Addis Ababa University, 2010-12) Teklemariam, Mengistu; Hailu, Dereje (PhD)
This research develops water demand (end-use) modelling and forecasting, and assesses water conservation and demand management potential for the city of Addis Ababa. The research methodology consists of four steps: 1) data collection, 2) assessing and reducing water distribution system leakage, 3) developing water demand (end-use) modelling and forecasting, 4) water conservation and demand management analysis. International Water Association (IWA)/American Water Work Association (AWWA)’s water loss analysis software and economical leakage reduction model is used for assessing and reducing water distribution system leakage. The Demand Side Management Least Cost Planning Decision Support System or DSS model is developed and used for water demand forecasting and assessing water conservation and demand management measures. DSS model is Microsoft Excel application model. The non-revenue water (NRW) level in the water distribution system in the city of Addis Ababa is found to be 38.2Million m3/year (39.5% system input volume). The real or physical losses are 26.2Million m3/year (27%) of the total NRW, the commercial/ apparent losses are 10.1Million m3/year (10.5%) and unbilled authorized consumptions are1.9 Million m3/year (2%). The economical leakage reduction model result indicated that 5.7Milion m3/year or about 10% of the water losses is an ‘’economical leakage level’. This show about a 29.5% of water losses can be saved through implementation of the recommended water loss reduction programs for the city of Addis Ababa. The water demand (end-use) modeling and forecasting has identified the city average water use in liter per capita per day is 117 and the projected water demand will be 840, 1,502 and 2,735 Million of liter per day by 2020, 2030, and 2040 respectively. With adaption and implementation of the recommended water conservation and demand management program B in the city of Addis Ababa would reduce the future water demand by 66%. This would postpone up to 2020 and downsize of the need for developing new water sources and infrastructures. Furthermore, the benefitcost analysis result of adapting and implementing the recommended water conservation and demand management program B provides present value benefit of 106,550 million birr and costs present value of 862 million birr to Water and Sewerage Authority of Addis Ababa (AAWSA). The benefit-cost ratio is found to be 120. The cost of water saved is found to be 8,145birr/Million litre which is less than the cost of developing new deep wells and operation and maintenance cost of 300,000birr/Million litres by AAWSA. Therefore, water conservation and demand management provides economically feasible and environmentally sustainable solution for meeting the shortfall supply and projected future water demand in the city of Addis Ababa. The environmental sustainability of water conservation and demand management option is reducing the waste water generated from household and buildings to sewerage system or to the environment.
Assessment and evaluation of surface water potential and demands in Baro-Akobo river basin, Ethiopia
(Addis Ababa University, 2016-06) Alkasim, Muhammed; Sahilu, Geremew
Baro- Akobo river basin is located in the southwest part of Ethiopia. The objective of this paper is to assess surface water potential using SWAT model and estimation of water demands using the Water Evaluation and Planning (WEAP) model in the Baro-Akobo Basin. According to the result obtained from SWAT model, the basin receives a mean annual rainfall of 1701.6 mm, which is 115.6BM3. The mean annual actual evapotranspiration is 30.8BM3 or 27% of the mean annual rainfall of the basin. The mean annual surface runoff that leaves from the basin is 19BM3 that corresponds to 279.68 mm. Out of the mean annual rainfall of 115.6BM3 and the other 18.6BM3 that is 273.71mm flows as lateral flow. The remaining 2.4BM3 is lost due to percolation for the recharging of the deep aquifer and 42.17BM3 revap from the shallow aquifer and flows as return flow. For calibration, the model was run for a period of six years and the monthly calibration results for R2 and NS were 0.83 and 0.56 respectively that are acceptable by the given ranges. For model validation, the model was run for a period of six years and the model validation results on monthly time step shows the results of R² and NS values were 0.81 and 0.67 respectively which is acceptable by the given ranges too. The water demand estimation portion of this study was done for six water supply, three hydropower and seven irrigation projects in the basin. The water demand result shows there is no shortage of water supply for scenario year 2015 to 2030. The annual overall demand is 4.085BMC. The annual demand for irrigation projects is 4.077BMC. The water demand found by this analysis is about 21.5% of the total surface water potential of 19BMC of surface water potential per year. The SWAT model is very sensitive and needs accurate input data. Using sufficient time and input data the model can simulate good result, which fits the observed stream flow data. In addition to this up to date land use and management data is essential for SWAT model. More efforts required to find best estimation of the surface water potential using SWAT model. The water demands in the basin is very small so further investigation is essential to use the available surface water potential of the basin. Key words: SWAT model, WEAP model, SWAT-CUP, surface runoff and water demands
Assessment and Modeling of Urban Drainage System Performance (A Case Study of Mojo Town)
(Addis Ababa University, 2020-09) Demisu, Tefera; Yilma, Seleshi (PhD)
The drainage system is one of the most important factors to be considered in the urban drainage infrastructure plan. Now inadequate urban stormwater drainage problems represent one of the most common sources of compliant numerous towns of Ethiopia. Drainage problem in mojo town the worst issue of over flooding on the surface runoff at high rainfall season. This difficulty occurred due to inadequate drainage network infrastructure and the increase in the urban pavement on most urban sub-catchments. The objective of this study to identify the critical condition and related problem with a drainage system, assess the hydraulic performance of stormwater drainage infrastructures, and to evaluate alternatives for drainage problem mitigation measures are achieving this specific objective SWMM5.1 model and LID control was used in the study. The calibration and validation of the SWMM5.1 model well-done and its performance was tested by the goodness of fit using the coefficient of determination (R 2 ) =0.97, the Nash –Sutcliffe coefficient (NSE) =0.96, and Relative error (RE) =11.16%. The simulated area of the study subdivide to four outlets of the total area of sub-catchment is 745.2ha joint to drainage system infrastructure of 93 nodes, 101 channels, and one divider are simulated by SWMM 5.1 model. From model result greater than 60% of drainage infrastructure is flooded, at the outfall total sub-catchment runoff is 6.88m 3 /s average flow, 22.44m 3 /s maximum flow and 3 583.07*10 3 m total volume of all outfall. The LID control used in this study for reduced the peak runoff overflow and select the best alternative on the outlet one of the project in the same sub-catchment S1, S2, S3, S5, S6, S9, S10, and S12 were the reduced the total outlet one volume by 28.12% using bio-retention Cell scenario, 25.9% infiltration trench scenario, 26.71% using permeable pavement scenario and also on sub-catchment reduced total volume outfall one reduced by 3.02 % using vegetation swale scenario. All scenarios used two of the highest value of runoff decreased by Bio-retention Cell scenario and permeable pavement for total study applied. by using two selected Lid control total volume of all outfall from 583.07*10 3 3 m is reduced to 425.89*10 3 3 m by 36.92% from the total study. Generally, the mojo town urban drainage system performance infrastructures overflow assessed and controlled for the problem occurred using the best alternative mitigation measures by improved LID control for all study areas.
Assessment of Climate Change Impact on Surface Water Resource Availability of Sibilu River Catchment,Upper Abbay Basin, Ethiopia
(Addis Ababa University, 2024-06) Alemayehu Mamo; Yilma Seleshi (PhD)
Understanding the effects Climate change impact on Surface water resource availability is the key point for sustainable management of natural resource. These changes would happen through changes in rainfall patterns, temperatures, and stream flow. The Coordinated Regional Downscale Experiment (CORDEX) was applied. Two Representative Concentration Pathways (RCP4.5 and RCP8.5) scenario for two future periods of 2050 (2031-2060) and 2080 (2061-2090) was used for climate projection. The projected maximum and minimum temperature will increase under both RCP4.5 and RCP8.5 scenario for near-term and long-term future periods by 1.9 0C, 2.8 0C, 2.2 0C, and 4.1 0C, and 1.9 0C, 2.9 0C, 2.5 0C, and 4.5 0C respectively. The projected potential evapotranspiration will increase by 6.3% to 8.6% for RCP4.5 scenarios and 6.7% to 11.4% for RCP8.5 scenarios under future periods. The projected the rainfall projection during the rainy season decreased by -5.8% to -1.2% for RCP4.5 scenarios and -3.7% to -0.4% for RCP8.5 scenarios under future periods as a result of increased projected temperature and potential evapotranspiration. HBV-Light model was used to simulate stream flow from 1985-2002 periods for calibration and 2003-2011 for validation periods. The model performance showed with R2=0.91, NSE=0.88, and PBIAS=13.43% for calibration and with R2=0.85, NSE=0.77, and PBIAS=15.07% for validation. Future simulated stream flow of the Sibilu River showed a decreasing trend during the rainy season, which has a significant impact on the surface water resource availability of the catchment. The reduction in stream flow volume directly related to decreasing rainfall would be attributed due to climate change impacts.
Assessment of Climate Change Impacts on the Hydrology of Upper Guder Catchment, Upper Blue Nile
(Addis Ababa University, 2011-06) Fentaw, Fikru; Hailu, Dereje (PhD)
Climate changes alter regional hydrologic conditions and results in a variety of impacts on water resource systems. Such hydrologic changes will affect almost every aspect of human well-being. The goal of this thesis is to assess the impact of climate change on the hydrology of Upper Guder catchment located in Northwest of Ethiopia. The GCM derived scenarios (HadCM3 A2a & B2a SRES emission scenarios) experiments were used for the climate projection. The statistical Downscaling Model (SDSM) was used to generate future possible local meteorological variables in the study area. The down-scaled data were then used as input to the Soil and Water Assessment Tool (SWAT) model to simulate the corresponding future stream flow regime in Upper Guder catchment of the Abbay River Basin. A semi distributed hydrological model, SWAT was developed and Generalized Likelihood Uncertainty Estimation (GLUE) was utilized for uncertainty analysis. GLUE is linked with SWAT in the Calibration and Uncertainty Program known as SWAT-CUP. Three benchmark periods simulated for this study were 2020s, 2050s and 2080s. The time series generated by GCM of HadCM3 A2a and B2a and Statistical Downscaling Model (SDSM) indicate a significant increasing trend in maximum and minimum temperature values and a slight increasing trend in precipitation for both A2a and B2a emission scenarios in both Gedo and Tikur Inch stations for all three bench mark periods. The hydrologic impact analysis made with the downscaled temperature and precipitation time series as input to the hydrological model SWAT suggested for both A2a and B2a emission scenarios. The model output shows that there may be an annual increase in flow volume up to 35% for both emission scenarios in three benchmark periods in the future. All seasons show an increase in flow volume for both A2a and B2a emission scenarios for all time horizons. Potential evapotranspiration in the catchment also will increase annually on average 3 - 15% for the 2020s and 7-25% for the 2050s and 2080s for both A2a and B2a emissions scenarios. Key words: Climate Change; Guder Sub-Basin; GCM; SDSM; SWAT; SWAT-CUP; GLUE
Assessment of Flow/Discharge Variability Effects on Bridges and Culverts along the Holeta to Ambo Road, West Shewa Zone, Oromia Region
(Addis Ababa University, 2024-04) Selamawit Banjaw; Asie Kemal (PhD)
This study assessed the effect of variable flow on bridges and culverts along Holeta Ambo Road, West Shewa Zone, Oromia Regional State. In this study, the HEC-HMS hydrological model is used for analysing the flow variability. The simulation uses meteorological gauge stations over a period of thirty-year (1991-2020) for the catchment, which is sourced from Ethiopian metrology agency. The model was calibrated and validated using observed discharge data from three-gauge stations—Berga Nr. Addis Alem, Awash Bello (031020), and Debis Nr. Guder—that was collected by the Ministry of Water and Energy, Addis Ababa. This study uses a calibrated HEC-HMS model to simulate daily flow in 56 drainage structures (bridges and culverts), over a period of 30-years (1991–2020). A coefficient of variance more than 40% is used as the threshold for variable flow. As a result, more than 71% of the structures exhibit a coefficient of variance of more than 40%. The study also develops design rainfall and rainfall intensity–duration frequency using Gen. Extreme Value (GEV). The design rainfall is used as an input in flood frequency modelling in HEC-HMS to estimate the peak discharge. The estimated peak flow is compared with the discharge capacity calculated using Manning’s formula, and the result showed that nearly 38% of drainage structure is prone to flooding. The effect of sedimentation on culvert structure is assessed through comparing the estimated peak flow and discharge capacity before and after sedimentation, and around 13% of the culverts are affected by sedimentation. The scouring effect of structure is computed by comparing the permissible velocity with the velocity calculated using Manning's formula. Consequently, 25% of the structures, particularly the bridges, are affected by scouring. This study reveals the impact of variable flow on drainage structures along the Holeta to Ambo Road, which is prone to flooding, sedimentation, and scouring. It is essential to replace the existing structures with those designed to manage variable flow, improve routine culvert maintenance and prioritizing the replacement of aging structures. These measures ensure the long-term safety, durability and functionality of the road network and structures. Additionally, this study provides the opening size and structure type of the selected drainage structures are used for other study.

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