Hydraulic Performance of Palestinian Water Distribution Systems(Jenin Water Supply Network as a Case Study)

The design of municipal water distribution systems in Palestine is implemented by using universal design factors without taking into consideration the effects of local conditions such as intermittent pumping, which is a way of operating the water distribution systems in most cities of developing world. By this way the water systems are divided into several pressure zones through which water is pumped alternatively and provided a large number of homes with a high quantity of water in a shorter period. This way makes the using of the roof storage tanks is very efficient during the non – pumping intervals, so that the hydraulic performance of the water networks expected to be affected by affecting the pressure and velocities values. To investigate the behavior of the water systems under the action of intermittent pumping, the Jenin water distribution network has been 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, modeling the system by using (WaterCad Program). The outputs show that the network is exposed to relatively high values of pressure and velocity, which have negative effects on the performance of the network. 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, overcoming the problems of high pressures by using pressure reducing valves at specific locations, and assuming steady state analysis, shows the ability of the existing system to serve the Jenin area 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 quality water 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 was calculated to be 2.0, and a value of 75 l/c/d was recorded as average daily water consumption. Studying the reaction of domestic water meter on air in the intermittent water supply networks over a two supply periods in two locations in the system by applying an arrangement consists of a regular and additional water meter, check valves and air release valve shows that the readings of the regular water meter are larger than the measurements of the additional water meter with a range of 5% - 8%. This difference depends on factors of location; consumer’s behavior and pressure drop in the system. The evaluation study of the water hammer in the Jenin distribution system, which has been implemented to investigate the effects of this phenomena shows that the water hammer values increase by increasing the velocity of water in pipes, and the values of shock pressures were within the limits of the shock pressures in water pipes systems.