Journal of Applied Science Issue (2) April (2019) 38 THEORETICAL ANALYSIS AND GRAPHICAL REPRESENTATION OF THE SYSTEM CURVE FOR WATER PIPELINE CONNECTING ZAWIA DESALINATION PLANT WITH HARSHA TANKS Abdulmenam A. Abdalla 1 , Ali K. Muftah 2 , Ahmed O. Amhamed 3 1, 2, 3 Mechanical department, Engineering faculty, Sabratha University 1 Abdoali1977@yahoo.com, 2 ali.alkhtabe@yahoo.com, 3 ahmed_dbash@yahoo.com Abstract The flow of water within a pipeline system causes loss of energy due to friction effects. To overcome these losses, energy is added to the water through the pump. So, the right pump selection is important for providing the required flow rate. The first step to select a right pump for any pipeline system is calculating the performance curve of piping system, which is a graphical representation of the energy required to move a given flow rate through a piping system and is used to identify the characteristics of the system's pump. For this purpose, the system curve for the water pipeline connecting the main reservoirs of Zawia desalination plant to the sub-tanks in Harsha has been evaluated and represented graphically in H-Q curve of the selected pump. This water pipeline network consists of sets of pipes connected in parallel and series with a total length of 5 km. The system NPSHA at different water levels in the suction tank at the maximum system flow rate of 800 (m 3 /hr) has been calculated to ensure avoiding cavitations problem in the selected pump. Keywords: pipeline, system curve, pump curve, cavitation Introduction Water is transported and stored to be used within the requirements of everyday life through a network of pipes with a range of equipment needed to process and transport water. This network is called the pipeline system. Due to the dynamic friction losses in the pipes, and differences in level between the beginning and the end of the system, the energy is needed to overcome these losses by adding pump/pumps to afford energy to a water flow. Pipelines system has an important role in various fields of modern life, where the pipeline is used to transport potable water to residential consumers, for drinking, cooking, washing...etc. Pipeline Networks are widely used in agricultural, industrial and commercial applications; For example, transporting of natural gas and oil products. Water supply is also essential for business and industry uses for transportation of natural gas, and oil products. Therefore, the Pipeline usage is increasing significantly in developing nations. The pipeline may extend over long distances and may be above or below ground; it is connected between the supply and delivery points taking into