Hydraulic Engineering
Permanent URI for this collection
Browse
Browsing Hydraulic Engineering by Subject "Addis Ababa"
Now showing 1 - 4 of 4
Results Per Page
Sort Options
Item Effect of Shallow Groundwater on City Infrastructural Plan The Case of Addis Ababa(Addis Ababa University, 2020-09) Abdulfeta, Amane; Mebruk, Mohammed (PhD)The main aim of this paper is to Understand and address impact of shallow Groundwater in Addis Ababa city infrastructural development plan which plays a vital role for the present and future urbanization of the city. In this study a three dimensional (3D) steady state GMS based groundwater modeling MODFLOW was used to characterize and assess the shallow groundwater flow. This model develop soil stratigraphy from borehole log data and need the hydrogeology data, recharge and river boundary conditions as its input for aquifer parameter. Thus a simplified two layer conceptual model was created by the perennial rivers in the basin as constant head boundary and the top surface as a recharge boundary from annual rainfall. This conceptual groundwater model includes the river and precipitation as inflow to the groundwater or source and discharging well with depth less than 100m were used as outflow from aquifer or sink. Up on all the given input hydraulic heads was generated and simulated. In the calibration 115 shallow wells were used. The calibration was made to an accepted level of error value of head difference 0-5 meter for each well by the software. The model clearly shows the groundwater hydraulic head and flow direction follows the general topography of the study area. Beside the master plan was analyzed and described by looking into the hydraulic head together with the city infrastructural plan. For selected sites in the city sub-model were developed for further analysis on effect of shallow groundwater on city infrastructural plan.Item Evaluation of Climate Change Impact on Extreme Hydrological Event Case study: Addis Ababa and surrounding catchment(Addis Ababa University, 2011-05) Alemu, Abayneh; Ayalew, Semu(PhD)The global climate may have serious impact on the frequency, magnitude, location and durations of hydrological extremes. Change in hydrological extremes will have implications on the design of future hydraulic structures, flood- plain development and water resource management .This study assesses the potential impact of climate change on extreme hydrological events in Akaki River catchment in and around Addis Ababa area. Projection of the future climate variables is done by using General Circulation Model (GCM) which is considered as the most advanced tool for estimating the future climatic condition. The climate projection analysis was done by dividing the coming 90 years into two time periods. The 1990-1999 was taken as baseline period against which comparison was made. A hydrological model, HEC-HMS was utilized to simulate Runoff in the study area. The performance of the model was assessed through calibration and validation process and resulted R2=0.78 during calibration and R2=0.81 during validation. For the coming 90 years, the mean monthly precipitation may both increase and decrease. The decrease in mean monthly precipitation may be up to 51% in 2030s and the increase may reach up to 131% in 2090s. The maximum and minimum temperature indicated an increasing trend. The simulated result shows that the maximum river flows in the study area will be high and more variable in terms of magnitude, and irregular of occurrence, than they are at present. It is observed that climate change has negligible effect on the low flow condition of the Akaki River flow. According to the evaluated scenarios, climate change has impact on the distributions of hydrological extremes in the study area. The impact of climate change may also cause a decrease in monthly mean flow up to 41% in the 2030s and increase up to 126% in the 2090s. Seasonal mean flow may show increase up to 13% and 15% in Kiremt (JJAS) season for 2030s and 2090s time periods respectively. The increasing of seasonal mean flow in Kermit (JJAS) has its own contribution for occurrence of flooding in Addis Ababa city. The increase in Bega (ONDJ) season flow will have a paramount importance for water harvesting in dam of water supply to Addis Ababa city. It is observed that there may be a net annual increase in mean annual flow volume in Akaki River due to climate change. Key words: Climate change; GCM, SDSM, flood; low flow; HEC-HMS; Addis AbabaItem Hydraulic Modeling and Improvement of Addis Ababa Water Supply System (The Case of Bole Bulbula)(Addis Ababa, 2015-06) Muluken, Saleamlak; Sahilu, Geremew (PhD)In this study, Addis Ababa Water distribution system for case study of Bole Bulbula supply system was assessed. The main objective of this study is to improve the Bole Bulbula water supply distribution system and control its operation, Water CAD software was used as tool to model water distribution system analysis. The modeling effort included both hydraulic and water quality modeling. Simulation results for maximum and minimum pressures were used as base tool to evaluate the hydraulic performance; and simulation result for water age and minimum residual chlorine were used as base to assess water quality transformation in distribution systems. Modeling results showed violation of maximum and minimum pressure requirements. Along with this, water quality simulation results illustrated water quality deterioration due to availability of minimum residual chlorine which is below WHO guideline. The model analysis result shows the different problems of the system. These are aged pipes, oversized and undersized pipes, low and high pressures and water quality status. The system should be modified using the design criteria of velocity, pressure and residual chlorine. High pressures in the existing system caused by customers at too low demand have to be identified and solution is established using pressure-reducing valves. To retrieve the situation there is a need to intervene. Modification in operation and design will improve the current situation of the case study water distribution system. Key Words: Water distribution system, modeling, Hydraulic performance, Water quality, Maximum pressure, Minimum pressure, Water age, Residual chlorine, Bole Bulbula, Addis Ababa.Item Investigation of Hydroelectric Generation Options in Addis Ababa city municipal Wastewater Treatment Plants(Addis Ababa University, 2019-10) Akelile, Tsigeberhan; Geremew, Sahilu (PhD)Energy recovery through local hydropower generation is a way of coping with high electricity expenditures in wastewater systems (WWS). There are some hydropower units operating in wastewater treatment plants, showing that there is an interest for this type of small-hydro, but there is still a lack of awareness of its potential. This study assess the hydroelectric potential in the existing wastewater treatment plants in Addis Ababa city, by introducing energy recovery turbines (pump as a turbine) on the downstream side of wastewater treatment plants. In wastewater treatment plants especially the electro-mechanical equipment consumes a considerable amount of energy in the treatment process. Specially, the newly constructed WWTP in Addis Ababa are totally dependent on electricity to function. Hence, by introducing a wide range of “pump as turbine” configurations that can offer cost-effective means of generating energy decentrally at heads from 2.5 to 300 meters and rates of flow ranging from 10 to 5000 liters per second, it is possible to recover the wasted potential. In this study, industrial centrifugal pump running as turbine were analyzed using Ansys cfx computational fluid dynamics (CFD) software. The pump was simulated in direct and reverse modes and complete characteristic curves of the pump in direct and reverse modes were obtained. The model was built up, starting from the real geometry, with a commercial tridimensional code, which is particularly suitable to simulate pumps. The numerical model was simulated. First, the model results were compared with the data declared by the pump manufacturer and the simulation model showed good accuracy. Then after using the validated model, the reverse mode was analyzed. The boundary conditions were changed in order to running the pump as a turbine. The results that were obtained from the simulation of pump in turbine mode is compared with the result obtained from Chapallaz design method. The results showed good accuracy. During the analysis the selected site has power production capacity between 4.1147 kW depending on the site conditions. Finally a relationship between flow, head and power was developed and sites with flow rate of above 40,000 m 3 /day and head above 25m will be economically feasible sites for hydro-power generation in wastewater treatment plants.