Hydraulic Performance Of Addis Ababa Water Distribution Systems (the Case Of Jan Meda Teferi Mekonnen Belay Zeleke Entoto And Ras Kassa Sub-systems)

The design of water distribution systems in Addis Ababa is implemented by using universalrndesign factors without taking into consideration the effects of local conditions such asrnintermittent pumping, which is the way of operating water distribution systems in most citiesrnof the developing world. By this way the water systems are divided into several pressurernzones through which water is pumped alternatively and provide a large number of homesrnwith a high quantity of water in a shorter period. This way makes the using of roof storagerntanks more efficient during the non – pumping intervals, so that the hydraulic performancernof the water network expected to be degraded by affecting the pressure and velocities values. rn rnTo investigate the behavior of Addis Ababa water distribution system under the action ofrnintermittent supply conditions; the Janmeda, Teferi Mekonnen, Belay Zeleke, Entoto andrnRas Kassa sub water distribution network is taken as a case study and a procedure ofrnmodeling the system as in reality depending on operational factors, ways of operating andrnmanaging the system, representing each cluster of houses by one consumption node, makingrncontrol by check valves, and then modeling the system by using (WaterCad Program). Thernoutputs show that the network is highly exposed to fluctuating pressure and velocity values,rnwhich have negative effects on the performance of the network. As the result ofrnintermittency and insufficient water supply, there is unreliable service and unevenrndistribution of water; a reduced network pressure due to the increased hydraulic losses rnassociated with increased flows and undersized pipe diameters; and increased water leakage.rnThe comparison of pressure results and field measurements at specific locations shows arnreasonable and small difference. rn rnThe modeling of the system as continuous supply system depending on assumptionsrnconsidering with future water consumption, availability of water, enhancement of operationrn& management of the water supply system, overcoming the problems of high and lowrnpressures by hydraulic modifications of distribution system, and assuming steady staternanalysis, the model output shows the ability of the existing system to serve the Janmeda,rnTeferi Mekonnen, Belay Zeleke, Entoto and Ras Kassa sub system and to cope the futurernextension. The output values of velocities are parallel reasonably to the assumed limits ofrnvelocities (0.1 m/s – 0.3 m/s) to avoid stagnation and water quality problems, also thernpressure values are within the limits of the design pressures in the residential areas. rn rnFurther evaluation has been carried out to investigate the daily water consumption, dailyrnpeak factors and to study the variations of water levels in roof tanks under the conditions ofrncontinuous supply by implementing an experiment of monitoring daily water consumptionrnfor different consumers at different locations for a period of 15 days. The average daily peakrnfactor is calculated to be 2.0, and a value of 79 l/c/d was recorded as average daily waterrnconsumption. The result has similarity with a little difference in comparison with the dailyrnwater consumption projected for year 2018 by Tahal Consulting Engineers LTD. Hydraulic performance of the study area water supply system is improved by employingrndesign and operational modifications through a planned augmentations of the water supplyrnand improving the distribution to meet the total demand and extending the supply hours,rnadjusting the oversized & undersized pipes and the pressure zone boundaries, and installingrna new tanks & pumps to overcome pressure related problems of the system, and replacingrnthe aged pipes to reduce leakage rates.

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