Most Ethiopian cities are characterized by having old water distribution networks uponrnwhich new extensions are linked in order to serve new areas, adding complexity to anrnaging network where full rehabilitation may not be practical due to economic constraints.rnIn this research, the water distribution network of Jijiga City, one of the major Cities inrnSomali regional state, was studied for analyzing and optimizing its design and extensionrntaking into consideration the effect of aging of the network, local conditions such asrnintermittent pumping, which is a way of operating the water distribution systems in mostrntowns of developing world. rnThe main objective of this study is to improve hydraulics performance of Jijiga city waterrnsupply distribution system and control its operation, Water CAD software was used asrntool to model water distribution system analysis. The modeling effort included onlyrnhydraulic performance modeling. Simulation results for maximum and minimumrnpressures were used as base tool to evaluate the hydraulic performance in the distributionrnsystem. The modeling results showed violation of maximum and minimum pressurernrequirements. Along with this, the model analysis result shows the different problems ofrnthe system. These are aged pipes, oversized and undersized pipes, low and high pressuresrnand water demand and supply status. The modeling of the system as continuous supplyrnsystem depending on assumptions considering with future water consumption,rnavailability of water, overcoming the problems of high pressures by using pressurernreducing valves at specific locations, and assuming steady state analysis, shows thernability of the existing system to serve the Jijiga area and to cope the future extension. Thernoutput values of velocities are parallel reasonably to the assumed limits of velocities (0.1rnm/s â€“ 0.3 m/s) to avoid stagnation and quality water problems, also the pressure valuesrnare within the limits of the design pressures in the residential areas. Further evaluationrnhas been carried out to investigate the total average day demand, peak hour demandrnfactors and maximum day demand factor and to study the water supply coverage in Jijigarntown. The peak hour demand factor was calculated to be 1.6, and a value of 25 l/c/d was recorded as average daily water consumption. Present nominal water supply coverage isrncalculated to be 49.6% and actual water supply coverage of the service is computed to bern43.11%. rnGenerally, the model analysis result shows the different problems of the system. Thesernare aged pipes, oversized and undersized pipes, low and high pressures and shortage ofrnwater from the source. The system should be modified using the design criteria ofrnvelocity, pressure and demand required. High pressures in the existing system caused byrncustomers at too low demand have to be identified and solution is established usingrnpressure-reducing valves. To retrieve the situation there is a need to intervene.rnModification in operation, design and finding another reliable water source and injectingrnto the system will improve the current situation of the Jijiga town water distributionrnsystem.