Hydraulic Performance of Addis Ababa Water Distribution Systems (The Case of Jan Meda, Teferi Mekonnen, Belay Zeleke, Entoto, and Ras Kassa Sub-Systems)
Creators: name: Seifemicheal, Molla
Publisher: name: National Academic Digital Repository of Ethiopia
Year: 2018

description: The design of water distribution systems in Addis Ababa is implemented by using universal design factors without taking into consideration the effects of local conditions such as intermittent pumping, which is the way of operating water distribution systems in most cities of the developing world. By this way the water systems are divided into several pressure zones through which water is pumped alternatively and provide a large number of homes with a high quantity of water in a shorter period. This way makes the using of roof storage tanks more efficient during the non – pumping intervals, so that the hydraulic performance of the water network expected to be degraded by affecting the pressure and velocities values. To investigate the behavior of Addis Ababa water distribution system under the action of intermittent supply conditions; the Janmeda, Teferi Mekonnen, Belay Zeleke, Entoto and Ras Kassa sub water distribution network is taken as a case study and a procedure of modeling the system as in reality depending on operational factors, ways of operating and managing the system, representing each cluster of houses by one consumption node, making control by check valves, and then modeling the system by using (WaterCad Program). The outputs show that the network is highly exposed to fluctuating pressure and velocity values, which have negative effects on the performance of the network. As the result of intermittency and insufficient water supply, there is unreliable service and uneven distribution of water; a reduced network pressure due to the increased hydraulic losses associated with increased flows and undersized pipe diameters; and increased water leakage. The comparison of pressure results and field measurements at specific locations shows a reasonable and small difference. The modeling of the system as continuous supply system depending on assumptions considering with future water consumption, availability of water, enhancement of operation &amp; management of the water supply system, overcoming the problems of high and low pressures by hydraulic modifications of distribution system, and assuming steady state analysis, the model output shows the ability of the existing system to serve the Janmeda, Teferi Mekonnen, Belay Zeleke, Entoto and Ras Kassa sub system and to cope the future extension. The output values of velocities are parallel reasonably to the assumed limits of velocities (0.1 m/s – 0.3 m/s) to avoid stagnation and water quality problems, also the pressure values are within the limits of the design pressures in the residential areas. Further evaluation has been carried out to investigate the daily water consumption, daily peak factors and to study the variations of water levels in roof tanks under the conditions of continuous supply by implementing an experiment of monitoring daily water consumption for different consumers at different locations for a period of 15 days. The average daily peak factor is calculated to be 2.0, and a value of 79 l/c/d was recorded as average daily water consumption. The result has similarity with a little difference in comparison with the daily water consumption projected for year 2018 by Tahal Consulting Engineers LTD. Hydraulic performance of the study area water supply system is improved by employing design and operational modifications through a planned augmentations of the water supply and improving the distribution to meet the total demand and extending the supply hours, adjusting the oversized &amp; undersized pipes and the pressure zone boundaries, and installing a new tanks &amp; pumps to overcome pressure related problems of the system, and replacing the aged pipes to reduce leakage rates.