Proceedings of the 2016 Industrial and Systems Engineering Research Conference H. Yang, Z. Kong, and MD Sarder, eds. Analysis of Drinking Water Distribution Systems Using Continuous- Time Discrete-Event Simulation Mohammed Alrezq and Nadiye O. Erdil Department of Mechanical and Industrial Engineering University of New Haven West Haven, CT 06516 Faisal Aqlan Department of Industrial Engineering Pennsylvania State University, The Behrend College Erie, PA 16563 Abstract A drinking water distribution system consists of a network of pipes, treatment plants, storage tanks, pumps, and other hydraulic appurtenances. The system carries water from a well or a centralized treatment plant to the end consumers. Drinking water distribution systems are often studied using analytical models. However, these models do not capture the continuous behavior observed in the system such as continuous material flow from one point to another. This research uses a continuous-time discrete-event (CTDE) simulation model to capture continuous material flow from holding stations to distribution tanks, and finally to the consumers’ taps. A case study from a geographical region in Najran City, Saudi Arabia, is considered. The CTDE simulation model is used to model a water distribution system (WDS) and to analyze the risk of water shortage by testing the impact of tanks’ sizes on eliminating the water shortage. The results of the study show that modeling the WDS using the CTDE simulation model is an effective approach for capturing continuous behavior and the uncertainties that occur in continuous systems and should be considered as an alternative advanced tool that will contribute to improve studying and analyzing WDSs. To improve the performance of the WDS, numerical experiments were carried out and determined that water shortages in some regions can be eliminated by increasing the size of water tanks. Keywords: water distribution systems, water shortage, continuous simulation, discrete-event simulation 1. Introduction The supply of fresh drinking water is essential to all, and water demand increases as populations grow. Water distribution systems (WDSs) are used to transport drinking water from one or more sources such as underground aquifers, rivers, lakes, or other sources to consumers. WDSs are complex systems consisting of multiple components including pipes, distribution tanks, tank districts, reservoirs and pumps. Each system component must work properly to transfer water reliably and efficiently. Analytical models are widely used in studies on designing a new or analyzing an existing WDS. Applications of analytical models in WDS studies range from investigating particular components inherent in the system such as pipe diameter or water leakage, to modeling these systems to manage water supply or systems operations in terms of scheduling, pumping and more. Analytical models involve using Genetic Algorithms, Simulation Annealing, and other methodologies. Although these models are effective tools for studies focusing on optimizing or designing WDSs to achieve a particular goal such as minimizing cost or maximizing profit, they are insufficient tools to model continuous systems and have shortcomings in capturing the uncertainties in WDSs such as fluctuations in supply and demand. In this study, a Continuous-Time Discrete-Event simulation (CTDE) approach is used to model a WDS to address this shortcoming. The CTDE simulation model refers to model a WDS using a continuous-discrete event simulation model. The strong advantage of the CTDE simulation model lies in its capability to model and to capture the changes in flow inherent in systems with continuous behavior. A case study involving a WDS in Najran City, Saudi Arabia, is considered to demonstrate the application of the CTDE simulation model to simulate WDSs and to test its capabilities in improving the WDS’s performance in mitigating water shortage. . The rest of this paper is organized as follows: Section 2 provides a brief review of similar studies in literature. Section 3 frames the case study,