Hydraulic Engineering

Permanent URI for this collectionhttps://etd.hu.edu.et/handle/123456789/69

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Start date: 2020

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    EVALUATION OF THE EXISTING URBAN WATER SUPPLY SYSTEM: A CASE OF HARGEISA CITY, SOMALILAND
    (Hawassa University, 2020-12-17) MOHAMOUD MOHAMED ISMAIL
    Urban water supply and demand challenges are widespread problems in most of the developing countries such as Somaliland. This thesis paper focuses on the evaluation of the existing urban water supply system of Hargeisa, capital city of Somaliland. The main objectives of this study is to spot the issues of Hargeisa water system by assessing the current status of the water supply system in the town, evaluating the Hydraulic performance of the WSS and eventually propose remedial measures. The current status was evaluated rely on the difference in the supply and demand of the town by forecasting its population while the water losses was used the difference between the production and consumption data. Moreover, to investigate the existing water supply and distribution system, an EPANET software was used to develop the model. The model can be used to customize the high pressure and low pressure zones in junctions and the level of velocity through pipe. The model run was performed for average, maximum, peak and low demand situations to investigate the system model. The analysis result shows that the supplied water in the town is only covering 13.5% of the demand. Hence, this result indicates that there’s a high gap between the demand & supply. In Addition, from three years obtain data of production and consumption the average loss became 9.75%. Moreover, the result and discussion shows that there are totally different issues of the system like high pressures and low pressure whereas, the utmost pressure occurred at gravity main pipe line in night demand was 85.92m which is above the suggested value and also in the low hour demand (LHD), 100% of the velocity in the pipes is less than 0.5m/s. To handle the problems, it needs providing extra pumps to increase the production, rehabilitate the prevailing well sources, maximizing the capacity of distribution pipe line by putting new pipes
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    EVALUATION OF SMALL SCALE HYDROPOWER WITH DIFFERENT DEVELOPMENT APPROACH AT UPSTREAM OF GIDABO RIVER FOR RURAL ELECTRIFICATION
    (Hawassa University, 2023-12-07) HABTAMU HAILU
    Hydropower is considered as one of the most desirable source of electrical energy due to its environmental friendly and extensive potential available throughout the world. The main objective of this study has to evaluate the small scale hydropower potential for rural electrification of Gidabo river, estimation of discharge to power generation for each selected sites, study energy demand for rural community and finally to prioritize and rank the best suitable site based on multi criteria decision analysis. The materials such as, RET Screen model with the objective to make complete pre-feasibility studies, GPS also used to estimate elevations at different points and ArcGIS was used to delineate watersheds and to determine heads by developing contours. The study method, conducted by reviewed different literatures related with power potential assessment and the collection of hydrological and meteorological data after collected those data, then analyzing data’s by using different software models, after analyzed the data making prefeasibility study for site selection, and transferred flow data for ungauged sites by using area ratio method then calculated power produce potential for each sites then develop flow and power duration curves to select design flows and ranked potential sites based on multi criteria decision analysis to select best suitable sites ,finally energy demand forecasted by using end use method. There was six (6) potential study sites had been selected by using Geographical Positioning System (GPS) of field surveying along the river and represented each site by code with respect to the discharge, power, head, nearest town and road accessibility. Analytical hierarchy process was chosen in combination with GIS as a method of multi criteria decision making to prioritize and select best hydropower site. ArcGIS, MCDA, GPS and Google earth were used for visualization, data analysis and interpretation. Based on multi criteria decision analysis of suitability index value (SI)the site code A@D$ become first choice and site code A@C$ become the last . The total annually energy potential of the selected site code A@D$ was estimated about 33146.0 MWh, 24076.16MWh and 5263.18 MWh for 30 %, 50 % and 90 % of time exceedance respectively. All six potential sites in the study area are classified as small scales hydropower based on installed capacity and also medium based on head. Finally, the forecasted of energy demand for community and load analysis was performed by using end-use method, for this study consider residential, Community and commercial load analysis to energy demand forecasting and evaluation. Generally, this research will give a piece of information about the study area for those concerned body for future work also additional works and for the implementation of SHP Plants
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    IMPACTS OF LAND USE LAND COVER CHANGE ON RESERVOIR SEDIMENTATION (THE CASE OF RIBB DAM, IN LAKE TANA SUB BASIN, ETHIOPIA)
    (Hawassa University, 2020-10-21) MEBRATU ESUBALEW ENGIDA
    Land use land cover (LULC) change is the challenge and continuous drivers of environmental change. Understanding the rate and process of change is, therefore, basic for managing the water resources and the environment at large. This study was intended to analyze the LULC changes impacts on sediment load from 2000 to 2018 periods, and select critical (hot spot area) sub basins and recommend best management practice for Ribb watershed of Lake Tana sub basin, Ethiopia. Both climate and hydrometric (flow and sediment) data were collected and analyzed over the period 1990 to 2018. Two time satellite imageries of the Land sat product (2000 and 2018) were used for land use change detection. The hybrid classification technique for extracting thematic information from satellite images were employed by using ERDAS model for classification of LULC. The Soil and Water Assessment Tool (SWAT) model was calibrated and validated to estimate sediment load of the watershed during the period 1992 to 2001 and 2002 to 2007 respectively. To manage the sediment load best management practices (BMP) as a scenario (filter strip, grassed water way and contouring) were implemented on 2018 LU map. The land use change detection result indicate that cultivated land has expanded from 66.87% in 2000 to 75.53% in 2018. Between 2000 and 2018 periods, it was increased by 8.66 %. The rate of increment during 2000–2018 periods were 608.915 ha/year. Similarly, settlement area had also increased by 2.09% from 2000–2018 periods. Similarly, shrub land and bare land also decreased at a rate of 412.868 and 227.651 ha/year, respectively, between 2000 and 2018 periods. Also the water body decreased at a rate of 1.593 ha/year between 2000 and 2018. The SWAT model result depict that the model give reasonable fit of sediment flux with observation during calibration and validation as evaluated with ENS ( 0.63 ) , R2 ( 0.67) and percent bias (17%) during calibration and ENS ( 0.58) , R2 ( 0.71) and percent bias of (12%) during validation period. Moreover, the severity of soil loss rate was increased with the average of 26.89 ton/ha/year from 2000 to 2018 LULC, which indicates that the management practice, was weak within the watershed. The BMP scenarios depict that filter strip was significant amount of LULC conversions practice and soil loss rate had occurred in the watershed from 2000 to 2018 periods, and expected to continue in the future. Thus, appropriate conservation and management practice are very much crucial to safe guard the life of the reservoir
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    EFFECT OF BAFFLE BLOCK PARAMETERS ON HYDRAULIC JUMP CHARACTERISTICS
    (Hawassa University, 2023-08-07) MEKONNEN BEKELE WORKU
    The experimental determination of baffle blocks installed on stilling basins has been also utilized to stabilize the formation of the jump and increase the turbulence, there by assisting in the dissipation of energy. The main objective of this study is to assess the effects of baffle block parameters on hydraulic jump characteristics. Investigate the influence of baffle blocks on hydraulic jump properties of flow over a weir, to evaluate the effects of different shapes and arrangements of baffle blocks on hydraulic jump characteristics and identify the best shape and arrangement of baffle blocks increasing efficiency of energy loss. The experimental work was performed in a rectangular flume with a dimension of (14 m* 0.3 m* 0.45 m) long, wide, and deep, respectively with Steel, different shapes of baffle blocks (Trapezoidal, Rectangular, and Triangular) with the dimension of (0.05 m*0.0375 m*0.06 m) height, width and length bed material. The experiment was being tested with various flow rates for different shapes and arrangements to analyze the effect on the sequent depth ratio, energy loss, Froud number, and efficiency. Each shape and arrangement baffle have five discharges that were used to maintain the upstream depth the relationship between the Froude number and the discharge for different baffle depth and different velocity; where the average value of the depth was varied (10mm - 50mm). Froude number decreases (1.92-1.54) with the decreases in the average value of loss of energy (0.20–0.14), as the sequent of depth ratio decreases (17.85*10-3 –13.41*10-3 ). The relation between Shape of Baffle Block, Energy Dissipation, and efficiency Trapezoidal (32.19, 70.86%), Rectangular (37.35, 83.98%), Triangular (32.03, 67.23%), and Mixed (34.41, 74.08%) respectively. From above clearly shows that rectangular baffle blocks have higher energy dispassion and efficiency which indicate that the energy dispassion and efficiency in row three and four arrangement 4*3*2 and 4*3*2*1 obtained best are energy dispassion (32.77%) and efficiency (83.98%) receptively under rectangular shapes, which is highest from baffle block shapes relatively better than the other baffle block shapes this is due to may be part of energy dissipate increases efficiency. From this observation rectangular baffle blocks are better for energy dissipation since higher efficiency
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    DAM BREACH ANALYSIS OF BISANDIMA DAM, SIDAMA REGINAL STATE, ETHIOPIA
    (Hawassa University, 2023-07-23) TAFESE FONA DEBESA
    Due to the construction of Bisandima dams, the downstream ecosystem is highly changed in that a huge area is covered with irrigation farms, new settlements, and residence areas of inhabitants living on the farms, and fishery communities were formed due to this dam. All these investments and newly settled inhabitants are highly exposed to flooding and they are at risk from the possible failure of this dam. The objective of this study was to model the Bisandima dam breach phenomena and to develop flood inundation maps. In this study dam breach, flood routing was carried out by using unsteady flow routing in HEC-RAS 2D model using geometric data to determine flood-susceptible areas downstream of the dam for the study area. The key inputs required in the dam breach flood routing processes include Precipitation data to determine PMF, digital Elevation model, and land use data were used as input for the HEC-RAS model. Some parametric methods were also used to predict dam breach parameters for use in the model. The breach discharge resulted from the HEC-RAS model for all methods such as Thun & Gillete (1990), Froehlich (2008), Froehlich (1995), MacDonald and Langridge –Monopolis (1984), Xu & Zhang (2009) were 2079.01, 1040.21, 1332.49, 531.91, 592.22 m3 /s and 1796.52, 620.37, 572.02, 530.53, 498.46 m3 /s for overtopping failure and piping failure respectively and also breach outflow at the downstream cross-section were 969.32, 625.48, 699.46, 538.96, 592.38 m 3 /s for overtopping failure respectively. The hazard mapping due to the combined effect of flood depth and velocity showed that an area of 28ha, 9.5ha, 11ha, 3ha, and 0.5ha are under low, medium, high, very high, and extreme hazard respectively for overtopping failure and an area of 20ha, 8ha, 10ha, 2.2ha, and 0.8ha are under low, medium, high, very high and extreme hazard respectively for piping failure. As noticed from the flood inundation map almost all critical areas downstream of the dam are in immediate danger. Based on the finding of the study outcomes the following recommendations are drawn: flood early warring, watershed treatment, provide dike at both sides of the downstream
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    PERFORMANCE ASSESSMENT OF URBAN DRAINAGE SYSTEMS OF YIRBA TOWN SIDAMA REGIONAL STATE, ETHIOPIA
    (Hawassa University, 2023-10-22) SITOTA MATHEWOS RIKBA
    Developing countries experience accelerated urbanization without adequate investment in infrastructure. Yirba town, like other towns of Ethiopia, have a lot of problems including inadequacy and poor-quality drainage infrastructure. The objective of this study is to assess the hydraulic performance of stormwater drainage systems of the study area, to identify stormwater management issues and existing urban drainage system problems, and to identify the best management practices for drainage problem mitigation measures and to achieve these specific objective SWMM5.2 model and LID structural measures were used in the study. Rainfall, infiltration, and physical characteristics of the catchment area were organized as three main inputs for the model. Rainfall depths of thirty one years (1992-2022) of Yirba station were obtained from National Meteorological Agency. According to chi-square test of the best fit probability is Log Pearson type III distribution and that is used to developed IDF curve. Infiltration of the model area is represented by Curve number method. Physical characteristics of the sub catchments including topography of the model area was analyzed using Goggle Earth and ArcGIS software. The calibration and validation of the SWMM5.2 model were done and its performance was tested by the goodness of fit using the coefficient of determination (R2) =0.97 and Nash Sutcliffe Efficiency Coefficient (NSE) =0.90. The total simulation area of sub catchment is 80 ha; the model area is divided in to 45 sub catchments with a drainage network of 38 conduits, 38 junctions and 2 outfalls. From model result 50% of conduits and 55% of junctions are flooded; at the outfall total sub-catchment runoff is 4.35m 3 /s average flow rate, 10.84m 3 /s maximum flow rate and 91.10*103 m3 total volumes of both outfalls. Among the various low impact development (LID) structural measures, infiltration trench and vegetative swale are incorporated and simulated in the model. Based on the simulation of LID's 10-year return period, improvements in terms of reduced peak discharges and increased peak discharge times were observed in sites where LID was used. In terms of a 10-year period, the peak runoff from particular sub catchments of drains is reduced by a minimum of 1.82% and a maximum of 19.91%. In general, the Yirba town urban drainage system performance infrastructure overflow was assessed and managed for the problem occurring using the possible mitigation techniques by improved LID control for all study areas.
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    DEVELOPING OPTIMAL RESERVOIR OPERATION (CASE OF KOKA MULTIPURPOSE RESERVOIR, ETHIOPIA
    (Hawassa University, 2023-07-18) GEMECHU SHIFERAW BELACHEW
    Reservoir operation is the most challenging task in the management of water resources systems. Hence, water resources models are needed to minimize these challenges, as much as possible if they are supplemented with sound engineering judgments. In this study, the rainfall runoff simulation HEC-Hydrologic Model System (HEC-HMS) and reservoir simulation model (HEC-ResSim) were applied to the koka multipurpose reservoir to optimize the power fluctuation observed and water scarcity due to reduced water release from the reservoir. Inflow was generated by the HEC-HMS model by using twenty years of daily meteorological data collected from NMA. The generated inflow was calibrated and validated with 16 years of observed flow data from Melka Kunture, Hombole, and Mojo gauging stations. The performance of the model was evaluated by NSE, R2, RMSE, and PBIAS performance indices criteria reviewed in different literature. For example, the NSE value of Melka Kunture, Hombole, Mojo, and Koka Inlet is 0.75, 0.78, 0.63, and 0.8 for calibration, and 0.7, 0.72, 0.53, and 0.75 for validation, respectively. The value of R2 for Melka Kunture, Hombole, Mojo and Koka Inlet is also 0.74, 0.77, 0.64 and 0.77 for calibration and 0.74, 0.75, 0.52 and 0.76 for validation respectively. Although the model slightly underestimates the flow, for both calibration and validation, the model shows acceptable performance to generate an inflow of the upper awash watershed. To simulate the reservoir the inflow generated by the HEC-HMS model, reservoir physical, and operational data were collected from governmental organizations and provided to the model. Since the HEC-ResSim model cannot optimize the constraints directly, trial and error have been applied through a prioritization rule between three main demands; i.e., Hydropower, Irrigation, and Domestic, Municipal and Industrial demands. The best alternative was selected based on the power target, release target, and pool elevation target. Accordingly, from the three alternatives applied in the simulation, ALT-1 gives maximum power and maximum release that supports the downstream water needs. When power demand was given the highest rule priority, the reservoir generate an average energy of 504.76MWh per day or 55GWh per year which is greater than the power generated in ALT- 2 and ALT-3 by 32% and 64%, respectively. The reservoir reaches its minimum elevation of 103.93m in June (except in the drought year of 2003 and 2016) and its maximum elevation of 110.39m in August. Generally, the reservoir can support the downstream water needs safely if the operation will be conducted by the power demand priority rule.
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    ASSESSMENT OF GROUNDWATER POTENTIAL ZONES: THE CASE OF WOGAYI WATERSHED IN THE OMO-GIBE RIVER BASIN, ETHIOPIA
    (Hawassa University, 2023-08-10) WUBISHET SISAY WOLDEYES
    This study was aimed at assessing the groundwater potential of Wegayi watershed in the Omo Gibe river basin. Secondary data: climate, topography, well log information and different thematic layers were used. The thematic layers considered in this study are geology, geomorphology, drainage density, lineament density, rainfall, soil types, slope and land use/cover. Arc GIS and Surfer 20 softwares were used to produce spatial maps of the different thematic layers and water table contours respectively. The geological formation of the catchment was evaluated using existing well logs data of the boreholes. The groundwater flow direction of the catchment was identified by using ground water level maps. The Saaty analytical hierarchy process (AHP) method was implemented to identify the groundwater potential zones based on their relative assigned weights. Eventually, the weights were normalized so as to indicating on their importance in groundwater occurrence. The major lithological units of the area are weathered and fractured basalts. These types of geological formation are recognized to be good groundwater formations. According to the groundwater flow lines and the ground water contour maps produced in the catchment, the groundwater flows from southern and eastern parts of the highlands of the catchment towards the plain areas of the northwestern parts of the catchment. The hydraulic characteristics are variable throughout the catchment. According to the result of groundwater potential map, the major recharge of groundwater occurs in the Easter and southwestern highlands of the catchment, which is said to be recharging zone. However, the area situated in the southeastern, northwestern and northeastern parts of the catchment is discharge zones. The results of AHP indicate that 58.12% moderate, 20.82% high, 21.03% low and 0.032% very low groundwater potential zones have been identified. Finally, it is concluded that the integrated GIS and remote sensing techniques are very efficient and useful for the identification of groundwater potential zones
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    Estimation of Groundwater Recharge Using GIS Based Wetspass-M Model: The Case of Dedaba Watershed, Rift Valley Lakes Basin, Ethiopia
    (Hawassa University, 2024-10-18) JIBRIL WAKEYO WARIO
    The Dedaba watershed, located within the Rift Valley Lakes Basin in Oromia, Ethiopia, is experiencing significant changes driven by agricultural expansion, land use and land cover (LULC) changes, and a growing population. These dynamics, combined with insufficient watershed management, have resulted in water resource depletion, pollution, and environmental degradation. The escalating demand for groundwater, driven by the population increase, present a considerable challenge in this region. This study utilized the WetSpass-M (Water and Energy Transfer between Soil, Plants, and Atmosphere under quasi Steady State – Monthly) model, a spatially-distributed water balance model, to assess seasonal and annual groundwater recharge, actual evapotranspiration, and surface runoff in the Dedaba watershed. The model integrates spatially distributed data on precipitation, potential evapotranspiration, temperature, wind speed, soil types, LULC, and topography. These datasets, processed using GIS techniques, allowed for the generation of detailed spatial water balance components. Calibration and validation of the model were conducted using observed groundwater levels and streamflow data, ensuring accurate simulations. The calibrated WetSpass-M model revealed groundwater recharge estimates ranging from 0.46 to 65.4 mm/year, with an average of 37.47 mm/year, representing 3.4% of the total recharge. To understand the impacts of LULC changes on groundwater recharge, the model was applied using LULC data from 1990 and 2020. Results indicated a continuous decline in recharge rates over this period, underscoring the significant influence of LULC on groundwater resources. Specifically, the model estimated recharge at 3.29 mm in January 1990, peaking at 6.03 mm in September, and dropping to 0.13 mm in December. By 2005, these values had decreased, with January at 2.84 mm, September at 5.2 mm, and December at 0.12 mm. The downward trend persisted into 2020, with recharge starting at 2.61 mm in January, peaking at 4.52 mm in September, and reaching 0.12 mm in December. The study highlights the critical need to consider temporal variability and long-term trends in groundwater recharge for sustainable water management in the Dedaba watershed. The analysis of LULC changes shows a rapid urban expansion, reduction of forests and grasslands, and consequent threats to groundwater recharge. Mitigating these risks requires collaborative efforts, including promoting afforestation, water-conserving urban farming, sustainable agricultural practices, and artificial recharge techniques. Future research should incorporate climate change projections to enhance groundwater recharge predictions and improve water resource management strategies.
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    FLOOD RISK MAPPING FOR FLOOD DISASTER REDUCTION IN THE CASE OF TEJI RIVER, AWASH BASIN, ETHIOPI
    (Hawassa University, 2024-07-10) DENEKE GOTA
    Floods pose significant threats globally, causing immense damage to lives, societies, and economies. This study aimed to assess flood hazards, evaluate vulnerabilities, and determine flood risk along the Teji River floodplain. To achieve the objectives of a study, advanced hydrological and hydraulic modeling techniques were analyzed, using data from various sources, including rainfall from the National Meteorological Agency, stream flow data from the Ministry of Water Resources, and land use/land cover data from USGS. The HEC-HMS model accurately calibrated and validated using observed stream flow data, the result of model calibration gives Nash Sutcliffe efficiency (NSE) of 0.78, Percent Bias (PBIAS) of 4.1, coefficient of determination (R2) of 0.79, and Relative Mean Square Error (RMSE) of 5.04. During the validation period, the model gives (R2) of 0.81, NSE of 0.79, PBIAS of 1.89, and RMSE of 1.29. After model calibration and validation, flood hydrographs for different return periods were generated. These hydrographs served as inputs for the HEC-RAS hydraulic model, integrated with GIS software to map flood inundation areas. The resulting flood inundation maps revealed extensive flood-prone areas along the Teji River, with maximum flood depths of 14.6 meters and maximum velocities of 6.5 m/s during a 100-year flood event. Flood hazard maps classified areas into different hazard categories from low to extreme hazard, and 43% of inundated area falling under extreme, very high, and high hazard levels, 57% of inundated area falling under medium, and low hazard levels. Vulnerability analysis considered indicators such as flood depth, velocity, duration, slope, land use, and population density, highlighting 8% of the flooded area as very high and high vulnerability, 27% of the flooded area as moderate vulnerability and 65% of the flooded area as low and very low vulnerability. Combining flood hazard and vulnerability information, a comprehensive flood risk map was developed, identifying 20% of the flooded area as very high and high risk, 27% of the flooded area as moderate risk and 53% of the flooded area as low and very low risk. These high-risk zones were concentrated in the towns of Asgori and Teji, emphasizing the need for mitigation measures and emergency response plans. The flood risk map provided valuable insights for decision-making processes, guiding the implementation of structural and non-structural measures, floodplain zoning, and population relocation. This study's findings contribute to effective flood management, land-use planning, and disaster risk reduction strategies along the Teji Rive