Hydraulic Engineering
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Item Water Resource System Modeling and Hydro-economic Trade-off Analysis of Abbay River Basin, Ethiopia(Addis Ababa University, 2024-08) Andargachew Melke; Yilma Seleshi (Prof.)This study was aimed at analyzing the hydro-economic trade-off and synergy between water, hydropower, and irrigation in the Abbay River basin by considering multiple development scenarios. The study scoped in assessing the water potential of the basin and analyzing the trade-off and hydro-economic benefit between irrigation development and hydropower generation. Multi-statistical performance criteria proved that the ArcSWAT model has the capacity to reproduce flows that agree with the measured flows and was found to be applicable over the Abbay River basin. The result revealed that the performance of the model improved as the basin was partitioned into sub-basins. The evaluation of different flow segments showed that the ArcSWAT model performed better for peak and high flows than mid and low flows. Overall, the model generates flow data that closely matches the measured flows in the Abbay River basin, which can be utilized as inputs to assess the trade-offs between hydropower and irrigation development. The hydro-economic trade-off analysis was undertaken to provide insight regarding the benefits received from hydropower and irrigation development scenarios. The research demonstrated the holistic development of water resources for both energy generation and irrigation purposes, thereby maximizing economic benefits while ensuring sustainable water resource management. HEC-ResSim model was found to be adequate for evaluating the power generating capacity of multiple hydropower cascade systems under various irrigation water diversion scenarios. The findings revealed that by focusing solely on hydropower projects without incorporating irrigation development, the Abbay river basin would generate up to 38 TWh of annual energy from GERD, Karadobi, Bekoabo, and Mandaya cascades, with GERD accounting for 39% of the total output. Under full integration of irrigation development with four hydropower cascades, annual system energy generation was reduced by 12%. The hydro-economic trade-offs between hydropower generation and irrigation development within the Abbay River basin. By analyzing various development scenarios, the study reveals how prioritizing one objective, either hydropower or irrigation, impacts the overall economic benefits. A key reference point is the absence of irrigation development, which serves as a baseline to assess the benefits of different scenarios. The results demonstrate that as irrigation benefits increase, hydropower benefits decrease, and vice versa. For instance, with no irrigation development, annual benefits from a series of cascade hydropower projects range from $1.3 billion to $3.1 billion USD, depending on the number of projects However, expanding irrigation reduces hydropower benefits by approximately 5% for every unit increase in irrigation benefits. When full irrigation development is achieved, annual irrigation benefits reach $3.6 billion USD, surpassing hydropower benefits by 17%. The analysis highlights that while trade-offs exist, pursuing both hydropower and irrigation concurrently results in greater combined benefits than focusing on either objective alone. The study concludes that integrated development of hydropower and irrigation within the Abbay River basin yields optimal economic outcomes, with combined annual benefits reaching nearly $6 billion USD, 94% higher than those from hydropower alone. Assessing the long-term economic benefits of hydropower and irrigation development in the Abbay River basin, taking into account the variability in returns over time was another basic points addressed in this research. Four scenarios are explored, each involving different combinations of dams (GERD, Karadobi, Bekoabo, and Mandaya) and a consistent irrigation area of 1.2 million hectares. The analysis shows a clear upward trend in economic benefits over time. Scenario 1, which includes only the GERD and 1.2 million hectares of irrigation, generates a present benefit of $4.5 billion USD, projected to rise to $26 billion USD by 2050. Scenarios with additional dams show progressively higher future benefits, with Scenario 4, incorporating all four dams and 1.2 million hectares of irrigation, yielding the highest returns of $34 billion USD by 2050. The study underscores that while present economic benefits are modest, substantial gains are realized in the long term, particularly as more dams are added to the development plan. The findings suggest that comprehensive development of hydropower and irrigation in the Abbay River basin offers significant economic advantages, especially in the long run, with the full cascade of dams providing the greatest benefits. The study also revealed that simultaneous development of hydropower and irrigation is advisable rather than prioritizing hydropower projects exclusively over the Abbay River basin.Item Deep Learning Approach to Estimate Streamflow from Remote Sensing Data(Addis Ababa University, 2024-02) Eyob Betru; Fiseha Behulu (PhD)Streamflow measurements that are reliable, precise, and continuous are essential for water resource analysis, planning, and management. However, there are relatively limited available hydrological data globally. The limited number of gauging stations worldwide is a common challenge, even worse in developing countries such as Ethiopia. As a result, novel research methodologies that can simulate river flow using multiple data sources are crucial. Remote sensing is one of the data sources that is considered a promising alternative. It has shown remarkable progress to date and in the future, such as the Surface Water and Ocean Topography (SWOT) mission, a satellite built to precisely observe nearly all the water on our planet's surface launched on December 16, 2022. Artificial intelligence, analogically "the new electricity" as a tool, has enormous potential to support the big challenge we face in monitoring our water resources. Hence, this study aims to integrate remote sensing and deep learning approaches for continuous streamflow time series generation. This will be achieved by collecting remote sensing-based precipitation products, vegetation indices and ground-based hydrometeorological data. Various types of single, hybrid, and ensemble deep learning models with the conceptual hydrological model are applied as a tool to model these univariate and multivariate types of data in different agroclimatic conditions, including the upper Tiber River basin (Italy), Abay River basin (Gummera subcatchment, Ethiopia), Awash River basin (Borkena subcatchment, Ethiopia), and Baro-Akobo River basin (Sore and Masha subcatchment, Ethiopia). Finally, by simulating streamflow with consistent top performance in all case study catchments, the results demonstrate the tremendous potential of the ensemble deep learning model. Although vegetation indices also showed much potential as an input for machine learning models, more study is needed to optimize performance with various data assimilation techniques. The findings of this research also provide further evidence for the significance of input data preprocessing, selection, length, and variability in conjunction with the kind of machine learning model we use to simulate streamflow accurately. The study also provides recommendations for further study and development in data-driven rainfall-runoff modelling.Item Investigation of Water Supply Sources Sustainability the Case of Harar Town, Ethiopia”(Addis Ababa Univesrity, 2024-11) Bedasa Abrahim; Yilma Seleshi (Prof.)In the present era sustainable water system is a concept that consuming the provided water sufficiently for a given need by preserving for future needs. In this research the water supply sources sustainability of Harar town was investigated in a more comprehensive approach. using the main and evaluation criteria that determine the sustainability of water supply sources. The sustainability analysis was performed from the experts’ preferences in the field of water sectors by distributing questioners to respond on the preferences of main criteria, evaluation criteria and alternative scenarios. The average aggregation of the experts’ preferences was used to attain final decision of influential evaluation criteria. The influential evaluation criteria used to examine the relative importance of the alternative water supply sources for the town. The water supply sources sustainability were affected by various driving factors such as population increase, climate change and LULC change and it is important to quantify these effects for better understanding of their impacts on the water resources. The water supply sources effects due increasing population in the future is determined by analyzing the demand and supply data until the end of the water supply sources identification period of 2070. On the other hand, the climate change effects also have a considerable effect on the sustainability of water supply sources and that needs special attention to determine the extent of the effects. Similarly, LULC change effects on water supply sources sustainability was quantified. In this research climate change impacts on the water supply sources from historical (1979-2014) to future (2024-207) periods were identified using hydrological model under two emission scenarios. The climate models (CORDEX RCMS) were used in this research to generate the climate variables used for hydrological model simulation. The LULC change effects on the water supply sources were examined under LULC data for period (2001 to 2020). The LULC map that used for this research was developed from Landsat image by employing supervised image classification under ArcGIS software. The quantification of climate change and LULC change process were taken place by SWAT model that requires various spatial and temporal data. During SWAT model setup process the study area watershed of the upper Erer subbasin (466 km2) were produced using the watershed delineation process. Nevertheless, hydrometeorological required for SWAT model are scarce and no continuous data. Despite the inadequacy of hydrometeorological data especially the rainfall distribution is variable both in amount and existence. The occurrence of rainfall on the stations with in a time gap probably affecting the areal rainfall estimation. Hence, in this research the spatiotemporal rainfall distribution implications on areal rainfall estimation characteristics were examined using more comprehensive method that involves the spatiotemporal rainfall distribution and mutual rainfall occurrence for the stations. Moreover, stream flow data were inadequate and continuous data are unavailable in the region. To fill the data gap, the streamflow data was measured on site for the year 2020 to 2021 using the installed staff gauge. The discharge was estimated from stream flow records using the rating curve. The water supply sources sustainability investigation output indicates that most influential evaluation criteria were capital cost (12.33 %), political (7.48 %), seasonality of sources (6.16 %), and availability (5.99 %). The alternative scenario analysis showed that the advanced potable water supply sources scenario was the best, followed by potable water supply and the business as usual is the least preference. The population estimation of the town using the United Nations Medium Variant Population Forecast indicates that the current population of the town was 127,854 and it becomes 929,418 by the year 2070. The daily water demand was higher than supply each year. In the region the increase of population along with other driving factors will deteriorate the future condition of the water supply sources. In this study autocalibration for SWAT model was used to identify sensitive parameters in the study area and manual calibration used to calibrate and validate. The SWAT model performance measures was within satisfactory range of PBIAS ≤ (±25%), R2 > 0.8 and NSE > 0.5. The calibrated and validated SWAT model output indicates that monthly mean temperature varies from 0.04 to 6.250C under RCP-4.5, and varies from 0.03 to 6.59oC under RCP-8.5. The monthly mean precipitation to be decline by 90.71 mm and rise by 211. 22 mm under RCP-4.5 and decline by 84.97 mm and rise by 235.62 mm under RCP-8.5. The LULC change and their effect examination indicates that agricultural lands (3.97%) forest lands (3.99 %), and water bodies (0.60 %) were decreased and settlements (2.30%), shrub land (3.07%) and bare land (3.19) were increased. The LULC change impacts on hydrological response such as surface runoff, ground water flow, and water yields were increased by 6.03, 8.22, and 10.39 %, respectively. While, evapotranspiration was decreased by 3.34%. In this research the climate change and LULC change have significantly affect the hydrological component of the sub basin. In the study area the average annual rainfall amount for Dire Dawa, Harar and Haramaya, Girawa, and Gursum stations are found to be 647, 816, 801, 958, and 840 mm with coefficients of variation of 23, 20, 20, 19 and 31%, respectively. The rainfall distribution at the gauging stations varies significantly both temporally and spatially. The joint probability of rain days estimation approach analysis output indicates that the monthly time step has better performance than daily, decadal and seasonal. The joint probability approach is used along with rainfall amount under monthly rainfall for areal rainfall estimation assessment in rainfall-runoff modelling. The efficiency of the hydrological model simulation highly dependent on the accuracy of data used during calibration and validation periods. The rating curve model performance measure values were in acceptable ranges of coefficient of determination of (0.98), root mean square error (4.49) and Nash–Sutcliffe Efficiency (0.97). This indicates that rating curve model was reasonably used to estimate the discharge in the upper Erer subbasin. The overall discoveries from this research can be used as valuable information for regional water authorities and decision-makers including planners in sustainable water resources management.Item Climate Change Impact Assessment on Water Resources Availability (A Case Study for The Selected Catchments in Upper Blue Nile Basin)(Addis Ababa University, 2011-05) Dereje Liben; Semu Ayalew ()PhD(The purpose of this thesis is to assess the significance of the climate change impact on streamflow at local scale (catchment scale) for some selected catchments in Upper Blue Nile Basin. The five catchments included in the study were Koga, Birr, Muger, Guder and Didessa Rivers. The Soil and Water Assessment Tool (SWAT) model is applied to study of the hydrology of the catchments and associated uncertainty with the simulated outputs. The SWAT model was calibrated for the period of 1992 to 2001 and validated for the period of 2001-2005. Model uncertainty was also done to establish the uncertainty bounds of the model, which is also the important boundary limit to evaluate the significance of the impact of climate change. The uncertainty analysis was done by using SUFI2 in SWAT-CUP. In the end, the climate change impact studies on water availability of the catchments were done based on the outputs of the Regional Climate Model (RegCM3) of emission scenario A1B. Overall the calibration and validation of the model was good except for Didessa. It was also shown from the model uncertainties analysis that the percentage of the simulated data within the uncertainty bound is only 24% for Didessa and 20% for Guder (P-factor=0.24, 0.20) which are relatively poor for both catchments. But for other catchments the percentage of simulated flow within the uncertainty limit during calibration and verification is more than 40% (P-factor=0.4). In general in all catchments; the impact of climate change may cause an increase in annual flow in both periods except in Koga and Didessa rivers. The estimation of the annual and monthly average flow volume changes in both period shows, the flow volume incremental range might be 48% to 185%. On the contrary, the decrement range flow in both rivers might be 0.33% to 6.7%. According to the uncertainty analysis carried out, the significance of the climatic change impacts for all catchment was analyzed. As a result it might be possible to conclude that for all catchments the impacts were significant except for Muger. Therefore, it can be deduced that climate change impact for most of the study areas might be the most sensitive than the propagated uncertainty on catchments flow.Item 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.Item 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.Item Hydrological Drought Monitoring, Forecasting, and Projection System Development in Ethiopia(Addis Ababa University, 2024-05) Kassa Abera; Admasu Gebeyehu (PhD)Due to its multifaceted effects and gradual beginning and end dissemination, the concept of drought is very debatable. However, experts divided drought into four categories: meteorological, agricultural, hydrological, and socioeconomic drought, which were characterized according to the lack of precipitation, soil moisture, surface, and subsurface water availability, and the imbalance between supply and demand, respectively. This study is primarily focused on hydrological drought monitoring and forecasting using two hydrological drought indices namely streamflow drought index (SDI) and surface water supply index (SWSI) across eight river basins in Ethiopia. Besides this spatiotemporal variability of meteorological drought in the Abbay river basin was analyzed using the standardized precipitation index (SPI) and reconnaissance drought index (RDI) to compare hydrological and meteorological drought correlation. Meteorological and streamflow data were collected from 50 rainfall stations and 35 streamflow stations from 1973 – 2014. The result indicates several severe and extreme drought events occurred during the 1980s and 1990s compared to the 2000s and 2010s. The most identified severe drought years are 1975, 1981, 1984, 1986, 1991, 1994, and 2010 whereas 1983, 1984, 2001, 2003, and 2010 were extreme drought years. The spatial analysis shows that the Tekeze, Abbay, and Baro river basins have similar characteristics; Awash and Rift Valley river basins show relatively the same character, and Genale Dawa and Wabishebele river basins have a similar drought trend. However, the Omo Gibe River basin has a unique character in that the severe drought occurred in a different year than other river basins. The statistical correlation of RDI and SPI, and SPI and SDI, RDI and SDI were found 0.95, 0.87, and 0.83 respectively, at an annual time scale. It implies that both hydrological and meteorological drought indices have an excellent correlation for long-term time scale and it also indicates the possibility of using SPI and RDI indices instead of SDI in areas having streamflow data scarcity. On the other hand, SDI and SWSI have a good relationship in all river basins except the Rift Valley basin. However, the overall result of hydrological drought analysis using SDI is better than SWSI compared to the previous historical drought events. Climate change-induced hydroclimatic hazards have increased from decade to decade overall in the world. So, projecting drought conditions for the future plays a great role in hydrology. In this regard, in this study, streamflow was forecasted from 2026 to 2099 using an artificial neural network (ANN) model using downscaled precipitation data as input to the model. Recently, ANN has been a suitable forecasting technique in water resource engineering. The future input data was downscaled using the Regional Climate Model (RCM) and the downscaled data have bias corrected using the linear scaling bias correction technique. The ANN model was trained and tested using historically observed precipitation and streamflow data as input and output variables respectively. Then the bias-corrected precipitation data is used to forecast future streamflow. The statistical performance parameters such as the Mean Absolute Percentage Error (MAPE), Root Mean Square Error (RMSE), and Coefficient of Determination (R2) were used to evaluate the performance of the ANN model and the result shows ANN has an acceptable value in humid areas than arid areas to forecast streamflow from precipitation data. Finally, the future hydrological drought condition of the country was investigated using SDI based on forecasted streamflow. The finding shows that the 2030s, 2040s, and 2060s are the expected critical and worth drought years in the country. The result of this thesis presents the establishment of hydrological drought monitoring, forecasting, and projection skills. The articles presented in this thesis seek to offer novel perspectives on hydrological drought monitoring, forecasting, and projection, emphasizing existing difficulties and opportunities for the generation of valuable information that can help decision-makers and policymakers in the management of water resources. Overall, the historical and future drought trends of Ethiopia indicate the country is frequently hit by severe droughts. So, appropriate drought mitigation measurement is needed. However, the commonly adopted drought mitigation trend in Ethiopia is a reactive approach which is a short-term drought mitigation technique during the drought event that has occurred. However, this approach will never bring a sustainable solution for drought-victim societies in the country. Therefore, it is better to shift into a new paradigm, a proactive approach which is a long–term drought mitigation system. To do this, the national government should actively promote the construction of water conservation infrastructure like dams and reservoirs, afforestation (green legacy), and the development of a national drought policy.Item Spatial Modelling of Groundwater Recharge Zones for Artificial Recharge: Integrating GIS and Remote Sensing in the Akaki River Catchment, Ethiopia(Addis Ababa University, 2024-05) Feven TamratExcessive extraction, uncontrolled groundwater withdrawal, and unregulated practices are leading to the depletion of groundwater resources in the Akaki Catchment, Ethiopia. The alarming rise in groundwater extraction is driven by urbanization and population growth, which aim to meet the high water demand in the area. Additionally, urbanization has reduced natural groundwater recharge due to deforestation and increased impervious surfaces. A study using a water balance model showed that the mean annual groundwater recharge decreased from 268.6 mm in 1986 to 260 mm in 2015, attributed to changes in land use and land cover in the catchment. To address this issue, implementing suitable artificial recharge structures can effectively increase groundwater levels. This study aims to identify potential zones for artificial groundwater recharge in the Akaki Catchment, Ethiopia, using integrated approach of Geographical Information System (GIS) and Remote Sensing (RS) Technologies with Analytic Hierarchy Process (AHP) to facilitate the implementation of recharge techniques. Nine groundwater recharge affecting factors were used to map the recharge indexes. The thematic layers were prepared from various remote sensing /satellite data, conventional and secondary data and used for groundwater recharge zone map development by assigning weights using AHP method to each thematic layer and features .The weighted sum overlay analysis (WOA ) result showed that the study area can be categorized into three different groundwater recharge potential zones: areas of high groundwater recharge are estimated to cover 1.38 km2 (0.10% of the study area), moderate recharge 1,192.69 km2 (82.75%), and low recharge 247.25 km2 (17.15%). The result was also validated through ROC method and had a prediction of AUC=0.756 and considered as a good prediction. Finally, in this study an effort has been made to recommend the possible types and locations for the selected artificial recharge structures.Item Estimation of Daily Streamflow Using Remote Sensing Data: The Case of Bilate River Sub-Basin, Ethiopia(Addis Ababa University, 2024-06) Cherinet Yacob; Agizew Nigussie (PhD)Most river basins in the world are ungauged. Especially in developing countries, catchments have less coverage of gauging stations. In Ethiopia, most river basins are ungauged. Streamflow data are collected at more than 506 operational gauging stations. Improving data accuracy and reliability of streamflow estimation in poorly gauged stations is mandatory. Different Streamflow estimation methods are developing from time to time. Traditionally, streamflow is directly measured through manual or automated ground based instruments installed within a monitoring station. In fact, there are different methods of Streamflow estimation. This study was conducted to gain better understanding on the use of remote sensing products for streamflow estimation in Bilate River sub-basin, Ethiopia. Four Remote sensed (satellite/reanalysis) precipitation products of different categories, source and resolution, namely GPM_3IMERGM v 07, CHIRPS 4.8 Daily, TRMM 3B42 v7 and ERA5 AG were compared against in situ observations. The main aim was estimating streamflow using bias-corrected remote sensed products and comparing the results with observed flows. Statistical measures such as Bias measurements, Coefficient of Regression, the Root Mean Square Error and the Mean Error were used. Also, Bias Component Hits, Missed and False rainfall and rainfall detection capability analysis and contingency table score such the Critical Index Success, Probability of Detection, Bias Frequency, and False Alarm Ratio were used to compare the satellite precipitation products with the gauge station data. The comparison were made depending on the stations' locations, point-to-pixel and sub basin scale analysis. Eight meteorological stations and five hydrological stations within the catchment were screened as reference data. The result from the comparison of observed daily time series data for 32 years (1991-2022) with satellite precipitation product indicates CHRIPs and IMERG performed better in terms of rainfall depth than TRMM and ERA5. Also, the degree of agreement R2 using the four satellite precipitation products in Bilate river sub basin shows 0.9, 0.87, 0.8 0.77 for IMERG, CHRIPs, TRMM and ERA5 Ag respectively. For model calibration 11 years (2001-2011) and for validation process 4 years (2012-2015) were used to simulate HBV Light model. The model performance was evaluated based on three objective functions namely: Nash Sutcliffe Efficiency Coefficient (NSE), Relative Volumetric Error (RVE), and the Root Mean Square Error (RMSE). Satellite precipitation products IMERG and CHRIPS with ERA5 Ag Satellite (Temperature and potential evapotranspiration) products used as an input for HBV Light model. The calibration results for IMERG R2 =0.7431 and PBIAS=1.08, objective functions NSE= 0.54, RMSE =0.87 and RVE =-1.37 for CHRIPS R2 =0.7474 and PBIAS=4.94, objective functions NSE = 0.51, RMSE =3.59 and RVE = -5.65.Item Development of Intensity Duration Frequency (IDF) Curves for Merawi Town, Ethiopia, Using Stationary Approach(Addis Ababa University, 2024-06) Tebikew Dereje; Yenesew Mengiste (PhD)Planning and management of water resources depend heavily on intensity duration frequency curves because they show the statistical relationship between rainfall frequency and intensity duration. This thesis used the universal extreme value stationary approach, which is implemented in the R statistical programming environment, to give a thorough examination into the development of rainfall intensity duration frequency curves. The study starts out by going over the theoretical understanding of the general extreme value model and how it is applied to the process of creating rainfall intensity duration frequency curves. Next, using specific packages and functions to effectively handle rainfall data, fit the general extreme value distribution, and produce the final intensity duration frequency curves; it explores the step-by-step implementation of the general extreme value stationary approach in R studio. For the duration of the observation periods, the stationary model takes constant parameters into consideration. Estimating the distribution parameters involved applying the maximum likelihood estimator method. Statistical programming software R-studio was utilized to compute the distribution parameters, intensity levels, and fit the GEV stationary model to sample rainfall data. For four neighboring rainfall sites, the National Meteorological Agency in Addis Ababa, Ethiopia, provided the necessary historical rainfall data. Various tests and trends using the rainfall data were looked at. The Man-Kendall trend test at each station's rainfall data showed no patterns. The stationary model was adopted for return levels estimation for all rainfall stations instead of the non-stationary model due to the lack of trend results. The distribution parameters of the parameter model were used to forecast the return levels for each return term of 2, 5, 10, 25, 50, and 100 years. Since the model did not exhibit time-varying variability, it was possible to derive maximum return level outputs directly from the general extreme value fitted to the maximum annual rainfall. The return levels were then plotted on the x-y axis and translated to rainfall intensity using a simple formula. In practice, longer return periods yielded higher values than shorter return periods when computing rainfall intensity. For instance, a 15-minute rainstorm stationary model with a 25-year return period produced an intensity of 178.28 mm/hr, while a 15-minute rainstorm with a 100-year return period produced 261.2 mm/hr of rainfall.Item Estimation of Sediment Yield Using SWAT Model and Reduction Methods (A Case Study of the Middle Awash Multipurpose Dam, Awash River Basin, Ethiopia)(Addis Ababa University, 2024-02) Saba Kidane; Daneal Fikresillassie (PhD)Sedimentation has been one of the critical challenges to create and sustain development opportunities for the poor families in Awash River Basin. Therefore, evaluating and understanding watershed sediment yield is vital to manage sediment related problems. Thus, this study used Middle Awash Multi-Purpose Dam (MAMD) catchment area to estimate sediment yield, to hotspot the most erodible sub-catchment area and assess the appropriate mitigation measurements to reduce the sediment load from the catchment. For the simulation of runoff and sediment yield from the MAMD watershed, the Soil and Water Assessment Tool (SWAT) model was applied. The total watershed has an area of 21,103.16 Km2 and located in Afar Regional State and Oromiya Regional State, Awash River Basin, Ethiopia. The SWAT model is calibrated and validated using SWAT-CUP with uncertainty analysis SUFI-2 (Sequential Uncertainty Fitting) procedure using measured monthly flow and sediment data from Awash and Metehara Gauge Stations. Using a data from 1993 to 2006 for calibration and 2007 to 2013 for validation, both results showed a good match between the measured and simulated flow and sediment. Flow calibration gives a coefficient of determination (R2) and Nash-Stucliffe simulation coefficient (NS) of 0.67 and 0.62 respectively. Flow validation gives R2 and NS of 0.65 and 0.63 respectively. Sediment calibration gives R2 and NS of 0.67 and 0.62 respectively. Sediment validation also gives R2 and NS of 0.69 and 0.69 respectively. Thus, the model performed well in simulating the flow and sediment for the study area. The estimated sediment result shows that the average annual sediment load at the outlet of the watershed was 40.32 ton/year. In this study, sub-basin 14 sub-basins were found to be a sediment prone areas having an annual sediment load that varies from 10.01 to 169.94ton/ha/year. Also, the model was applied to examine the Best Practice Management (BMP) scenario under the change of 25%, 35% and 50% Agricultural land use type to forest land, and other recommended scenarios to reduce the production of sediment. The investigation showed that the conversion of 25%, 35% and 50% of Agricultural land to forest land can reduce the total sediment yield by 26.59%, 34.15% and 45.76%, respectively. The implementation of Filter Strips, Grassed Waterways, Terracing, and Contouring can reduce the mean annual sediment yield at the outlet by 67.19%, 81.80%, 84.30% and 59.25%, respectively. The application of Terracing has high sediment reduction potential than other best management practices.Item Hydro-Economic Modelling of Multi-Objective Cascade Reservoir Operations under Seasonal Streamflow Variability(Addis Ababa University, 2023-10) Bahru Mekuria; Asie Kemal (PhD); Getachew Tegegne (PhD); Assefa M. Melesse (Prof.)Effective river basin management is challenging due to competing demands and environmental constraints. Understanding current reservoir operations is critical for developing alternative policies. This study applies a reservoir operation simulation-optimization technique to identify the best policies by utilizing economical approaches that balance competing objectives and system uncertainty. It may not accurately reflect a hydrologic model's genuine simulation capability to evaluate its performance just in terms of a formal simulation method. Hence, this study examined the effect of subbasin spatial scale on the hydrological model prediction uncertainty for different flow quantiles within the Omo Gibe River basin's sub-basins: Abelti, Wabi, and Gecha watersheds, from 1989 to 2020. The study found that the SWAT model accurately reproduced the observed hydrograph with over 85% accuracy for the Abelti watershed, over 82% accuracy for the Wabi watershed, and over 73% accuracy for the Gecha watershed. The subbasin spatial scale impacted the reproduction of flow quantiles, and the best scales for peak and low flows were found to be 79-98% and 29-42%, respectively. The study highlights the importance of investigating proper subbasin spatial scales for sustainable management of floods and drought. Furthermore, it suggests an improvement over the existing method of evaluating hydrological models and emphasizes the need to account for hydrologic model uncertainty for a good assessment. This study also addresses the challenge of estimating water resources in ungauged catchments, such as the Omo-Gibe River basin in Ethiopia, which is ungauged in about 70% of its area. The Reliability-weighted (RB) approach, a new method that combines three commonly used parameter transfer techniques (Global mean, Physical similarity, and Spatial proximity), was introduced to predict runoff in regions with unreliable data. The weights are computed using the donor catchment's hydrological model's reliability value during the calibration and validation periods. The RB method outperformed all three regionalization approaches by about 30% for the test catchments, and the proposed strategy's regionalization performance had a metric Nash-Sutcliffe efficiency greater than 0.50 approximately 85% of the time. The study shows that the RB approach is a useful tool for assessing available water resources in ungauged catchments.The Omo Gibe cascade reservoir operations problem was examined and solved using a cutting-edge evolutionary optimization method (Borg MOEA). The Omo Gibe River Basin system faces competing sectoral needs for hydropower generation, flood management, public and private irrigation, flood recession farming, and environmental flows. The results of the model showed reliable and robust optimal solutions, enabling the evaluation of the tradeoffs between revenue generation, minimum environmental flow provision, and reservoir storage conditions. Under the existing scenario, the hydropower can produce up to 4.6 billion ETB, while the irrigation revenue is 720 million, which is expected to increase faster than hydropower revenue in the near-future scenario, up to 9 billion, whereas hydropower revenue will produce 10 billion, creating more competition, higher water usage, and necessitate better resource management. In addition, the renovated Gibe III Power Station's hydropower production can increase by approximately 65% in 2019 compared to the actual hydropower production. The evolutionary algorithm models used for reservoir operations are outstanding. Employing these advanced optimization models with more data can lead to a better understanding and improved reservoir operations.Item Flood Hazard Mapping and Propose Mitigation Measure: a case of Wera District, in Halaba Zone, Ethiopia(2024-02) Martha Ersumo; Dereje Hailu (PhD)For flood prone areas, identifying flood generating factors, mapping flood hazardous zones and propose flood eliminating methods can increase the knowledge, awareness and individual initiatives to prevent themselves and their properties from flood effects by using appropriate flood mitigation measures before and during flood events. Developing Flood Hazard Maps for flood prone area can be developed by integrating geo-spatial information on flood conditioning factors. Based on the AHP and GIS techniques, Flood Hazard Map for Wera District was develop by using Soil data, Lu/Lc data, Drainage Density, Slope, Rainfall and Topographic data of the Catchment. This study aims to map flood hazardous area and propose mitigation measures, for Wera Woreda in Bilate River sub-basin by using GIS, HEC-HMS, AHP, HEC-RAS and HEC – GeoRas software. Depending on the L-momentum Ratio diagram of the three distribution methods, Gumbel Distribution was used for this study to compute peak discharge. Thus, the final peak Discharges for 2,5,10, 25, 50 and 100 years was estimated 119.44, 189.18, 235.36, 293.70, 336.71 and 379.94m3/s respectively. HEC-Geo RAS Software was used to develop river geometry such as: the river centerline, river bank, flow path and cut cross-section for Bilate River. HEC-RAS, hydraulic analysis includes the computation of the water surface profiles. Based on the degree to flooding, the importance of selected factors was ranked to five flood hazard category, namely very low, low, moderate, high and very high flooding. The weight coefficients were determined for each parameter by Analytical Hierarch Process (AHP) and overlay of ranked spatial information result the final flood hazard map of study areas. The flood hazard maps indicate that 60, 91, 93, 58, and 12.5km2 corresponds with very high, high, moderate, low and very low hazard areas respectively for Wera Woreda. For this thesis work, I was try to compare construction of levee along the channel and channel modification as alternatives for remedial measures to protect the flood from study area. From two alternatives, construction of levee along the river was the best alternative for study area.Item Dam Hazard Classification using ENTRO Guideline in the case of Fato Dam, Ethiopia(Addis Ababa University, 2023-07) Firaol Chalchisa; Netsanet Nigatu (PhD)The phenomenon of spontaneous breaches of dams and consequent flooding that have occurred throughout history have made it necessary to design dam safety plans and hazard management measures. In this case, the preliminary job was analyzing the dam breach before the event and ranking these dams based on risk. The pre-event analysis of a dam breach scenario for the Fato dam was the focus of this thesis. A deterministic approach is applied to model the dam breach. The extent of the resulting flood inundation is mapped and overtopping, and piping failure scenarios are evaluated. The upstream boundary condition comprises a 2.3*PMF inflow hydrograph and a base inflow hydrograph, and the downstream boundary condition is made up of a riverbed slope assuming the bed slope and energy grade line slope are equal to HAEC. The main reason why the PMF flood to overtop to dam needed is large is that a large freeboard is provided for the Fato dam about 3 meters here between the spillway crest and the dam crest. Seven 2D simulations were run, five of which are for various overtopping failures and two of which are for piping failure modes. HEC-RAS Version 6.3.1 hydraulic modeling software is used. Furthermore, seven deterministic non-physical empirical are assessed and compared. The five deterministic non-physical empirical methods have resulted in peak flow values between 32,940.26m3/s and 22,404.28m3/s for overtopping and two of them were 20,224.88m3/s and 11,799.72m3/s for piping modes of failure, respectively. Of the failures, overtopping failure generates the biggest peak discharge, which is 32,940.26 m3/sec using Von Thun & Gillete Equation. Not only the peak discharge results from this equation but also the flood reach to Guder Town is short for it, which is 1.35Hrs. Guder town is the focus of the study since most of the population at risk was situated in this town. Based on this flood inundation map the possible people at risk (PAR) were found to be 9,425 people. And based on the DSO-99-06 manual the Loss of life is found to be 4,713. The study found the dam breach and its corresponding flooding to be catastrophic in Loss of Life therefore its categorized as a very high-hazard dam based on ENTRO guidelines. The author also checks for the level of reduction if EAP is introduced, and the Loss of life is found to be only 10 people. Therefore, the study highlighted the provision of EAP to this dam will reduce the possible loss of life in case the dam fails. Taking this dam as a case study recommended the need for a national-level regulatory framework for different levels of dam life (Design, Construction, Filling, Operation, and Decommissioning).Item Flow Estimation in Zarima May Day Dam watershed using SWAT Model(Addis Ababa University, 2023-03) Haftom Teklay; Yilma Seleshi (Prof.)Estimation of flow on the hydrological regime of river basins is one of the most concerns in the river sub basin of zarima. With plethora of tools available in the literature choosing of an appropriate tool that can quantify and analyze the impact of flow on the hydrological regime in a systematic and planned manner is important. Soil and Water Assessment Tool (SWAT) integrated with Geographic Information System (GIS) based interfaces and its easy linkage to sensitivity, calibration and uncertainty analysis tools made its applicability more simple and has great potential in simulation of the past, present and future scenarios. A number of standards were used to appraise the model set-up, model performances, physical representation of the model parameters, and the accuracy of the hydrological model balance to assess the models that are defined in journal papers. On the basis of performance indicators, the mainstream of the SWAT models were categorized as providing satisfactory to very good. This review debates on the application of SWAT in analyzing land use land cover and run of estimation for the case study of Zarima May Day dam watershed. The Application of SWAT and land use land cover change in simulation models for Zarima May Day dam watershed is to improve accuracy, reduces costs, and allows the simulation of a wide variety of conservation practices at watershed scale. It is also observed that different researchers and/or model versions bring about in different outcomes while a comparison of SWAT model applications on similar case study was applied. This review determines the interactive role of SWAT and GIS technologies in improving integrated watershed management in Runoff Estimation and land use land cover for the topic of the study area.Item am Breach Modelling and Flood mapping, a Case Study of Ribb Dam(Addis Ababa University, 2021-01) Fasika, Worku; Daneal, Fikreselassie (PhD0The 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.Item Flood Change Detection, Attribution and Management Implication in Data-Scarce Watersheds: A Case of Wabi Shebele River Basin, Ethiopia(Addis Ababa University, 2022-03) Fraol, Abebe; Belete, Berhanu (PhD); Semu, Ayalew (PhD)Trends and variability of hydroclimatic extremes have received excessive attention in many hydrological modeling studies. However, many scientists are still uncertain to attribute the proportion of hydrologic variability is driven by climate change/variability and anthropogenic factors, particularly in tropical catchments. Wabi Shebele River Basin in Ethiopia experiences flooding with limited availability of the type data is used as a case study to investigate changes in flood discharges and potential driving factors affecting hydrologic response changes and management implication of understanding flood variabilities. Both statistical non-parametric tests and SWAT hydrologic model are used in flood change detection and attribution process. Among the discharge-based flood indicators, annual maximum series (AMS) and peak over threshold (POT) are used to analysis flood time series. Overview of flood discharge analysis indicates the increasing tendency of flood events throughout the basin since 2000. The seasonality analysis reveals cycles of significant extreme high river flows at five to ten-year intervals in the river basin. Precipitation extremes show an increasing trend in the western and eastern upper basin and a decreasing trend in the middle between 1980-2018. The assessment upon driving forces of floods: rainfall, drainage area, elevation, slope, sand soil, forest, and agricultural land coverage identified as the most influential variables in flood formation of the basin. The correlation analysis between extreme streamflow with precipitation and global climate indices reveals a moderate to high correlation value. The semi-distributed hydrological model (i.e., SWAT) conducted to disentangle the impact of climate change and LULC change on flood hazard showed that precipitation and agricultural land coverage led to increment in flood indices. In the middle and upper parts of the Wabi Shebele basin, streamflow increases with increases in agricultural land, and forest coverage decrease. The simulation of hydrologic response to climate change in the future (i.e., 2041-2060 and 2081-2100) showed that the river basin is likely to experience an increase in flood hazard with an increase in precipitation in the future as temperatures increase less than 2oC. Finally, the study on the implication of flood variability revealed that socio-economic damages follow a similar trend tendency to flood variabilities in the river basin. In such cases, development-based climate adaptation mechanisms and flood risk management strategies need to placed. In transboundary river basins like Wabi Shebele, floods have transboundary consequences which need cooperation between riparian countries for Integrated Flood Management (IMF).Item Estimation of Sediment Yield under the Impact of Climate Change (Case of Mille River Watershed, Lower Awash Sub-Basin, Ethiopia)(Addis Ababa University, 2022-03) Samuel, Tadesse; Bayou, Chane (PhD)Climate change impact and its variability on stream flows and sediment yield are now becoming one of the significant challenges. Hence evaluation of the impact and the trends of the climate change on hydrological process is very important at watershed level. The aim of this study was to assess the impact of climate change on the sediment yield of Mille river watershed at the lower Awash sub-basin using both climate and SWAT hydrological model. The climate model variables (precipitation and temperature) were obtained from Coordinated Regional Downscaling Experiment (CORDEX) of RACMO22 RCM climate model under HadGEM2-ES GCM and CCLM4 regional Climate model under ICHEC-ES global climate model with representative concentration pathway (RCP4.5) and (RCP8.5) scenarios. Bias correction was applied to climate variables and average value of the two RCM models arranged before future climate data’s transferred to hydrological model (SWAT) to simulate discharge and sediment for future time period. For model performance evaluation; Coefficient of determination (R2) and Nash Sutcliffe Efficiency (NSE) were used during calibration (1989-1997) and validated (1998-2002) period. The result of calibration and validation flow (R2 and NSE) are 0.68, 0.54 and 0.7, 0.6 respectively. Calibration and validation of sediment also provided a result of 0.81, 0.81 during calibration and 0.8, 0.79 during validation for R2, NSE respectively. Stream flow was simulated for two consecutive thirty years periods of (2031–2060) and (2061-2090) for both scenarios and compared with the base period (1986–2015) to investigate impact of climate change on hydrological process. The result obtained shows that overall mean annual precipitation projected to increase by 3.86% in 2050s and 7.82% during 2070s under RCP 4.5. For RCP 8.5 climate scenario precipitation increase by 4.61% during 2050s and 10.57% during 2070s. The hydrological response of a catchment also show an increment for the increasing precipitation amount such as sediment yield increase by 5.85% and 10.11% during 2050s and 2070s respectively under RCP 4.5 and 8.99% and 14.25% of increment occur in 2050s and 2070s respectively for RCP 8.5 climate scenario. Temperature maximum also shows an increment with a magnitude of 0.11oc and 0.09oc under RCP 4.5 of the 2050s and 2070s on the other hand 0.2oc and 0.15oc increment was observed with in the same period of RCP 8.5. Temperature minimum will be increase for the future over the Mille watershed by 0.09oc and 0.15oc Under RCP 4.5 and by 0.13oc and 0.18oc under RCP 8.5 for the same time horizons of 2050s and 2070s.Overall there will be a variations of precipitation, temperature and sediment yield month to month and season to season. Therefore, it is important to consider this variation of sediment yield and climatic variable to draw appropriate guidelines for planning and management of different water resources project.Item Evaluation of Ring Road Drainage Structure (Case Study Megenagna to Bole Road)(Addis Ababa University, 2021-11) Yisake, Desalegn; Daniel, Fikresilassie (PhD)The Purpose of the study is to assess the Performance of Drainage Structures of the Ring Road from Megenagna to Bole Round About and gives a mitigation measures regarding the drainages structure along the Road. An exploratory method of research has been used in the study. The study uses both primary and secondary instruments of data collection. The primary data collection instruments are observation, measuring the geometry (width and height) of existing cross drainage structures on the site, photographs that show the existing drainage structure conditions. The secondary data sources are Rainfall data, soil type, land use, geological map, and DEM data and QGIS 3.16 (open-source software) uses for watershed delineation of the catchment and extraction of other important geometric characteristics (i.e length of longest flow path, slope, elevation of the river and area of the catchment). Hydrological analyses have been carried out by using Soil Conservation Service (SCS) curve number Method and Rational method, the hydraulic analysis computed using the HEC RAS (open-source software) that to determine water surface elevations at all locations of interest for either a given set of flow data (steady flow simulation). The next step is to check the adequacy of the existing drainage system that suite the site conditions for the computed discharge, thus based on the hydraulics result, the major river exist around imperial not functioned well for the 100-return period, so shall be replaced with the new Bridge as span of 15m and 3.5m, which will accommodate the incoming 100-year discharge. The minor river exists between Ayat hospital and Imperial Round about, it is not having a significant flow and Can be retain as it is, only required maintenance and clearing of the channel. Regarding to the storm drainage all the inlets are not functioned properly due to complete damage of inlets and blockages of by rubbish/dribs. Therefore, this study recommends to maintain all the damaged inlets and clear the drainage system that has been blocked by rubbish/ dribs.Item Evaluation of Hydraulic Parametersi n Case of Akaki Wells on WF02-PW16 aND WF02-PW17 Wells(Addis Ababa University, 2021-10) Solomon, Lake; Daniel, Fikresilassie (PhD)The term groundwater is usually reserved for the subsurface water that occurs beneath the water table in soils and geologic formations that are fully saturated. In recent decades it has become apparent in many countries of the world that groundwater is one of the most important natural resources. So far, in Ethiopia, groundwater is mainly utilized for the water supply purposes. It takes care at present of 70% of rural water supply and plays a major role in several of the largest cities (Addis Ababa, Dire Dawa, Mekelle, Bishoftu, and Harari) and a number of medium-sized towns. As capital of Ethiopian, Addis Ababa has seen greater expansions and urbanization than other major city in the country. The primary objective of this project is evaluation of pumping test data to determine the hydraulic parameter of the Akaki phase IIIA bore holes in case of WF02-PW16 and WF02-PW17 by using Theis curve matching method, Cooper Jacob and recovery method on excel sheet and aquifer test software. Akaki well phase IIIA on WF02-16, WF02-17 Wells is located between 8°45' 20" to 9°13' 17" N latitude and 38°34' 3" to 39°4'10" E longitude in Oromiya Regional State, Akaki Kality Sub city south of Addis Ababa about 20 km from the city center. Akaki well field is one of the water supply projects implemented to alleviate the prevailing unsatisfactory water supply situation at the capital city, which is an important service for one of the most water deficit areas of the city-western & central Addis Ababa. The transmissivity values obtained in this project has great variation from the study of WWDSE which accounts for 5 to 100%. These two wells analyses results have overestimated. The overestimated Transmissivity envisions good aquifer with better yield than the capacity of the aquifer.