Modern Environmental Science and Engineering (ISSN 2333-2581) January 2020, Volume 6, No. 1, pp. 173-179 Doi: 10.15341/mese(2333-2581)/01.06.2020/017 Academic Star Publishing Company, 2020 www.academicstar.us Preliminary Estimation of Spatial and Temporal Synchronization of Water Demands in the City of Tripoli Salah H. A. Saleh, Mohamed Alsharif, Ali Ahmed Elkebir, and Edawi Wheida Civil Engineering Department/Faculty of Engineering, University of Tripoli, Tripoli, Libya Abstract: Water supply systems represent an essential component of the infrastructure in urban populations worldwide. Water distribution systems are designed by sizing system components so that they meet current and future demands to be provided at minimum required levels of water pressure and quality. The sizing of pipelines is highly dependent on the amount of water demands allocated to distribution nodes of the system under consideration. The current demand allocation practices normally imply that there is perfect spatial synchronization among the aggregated demands, which is not essentially the case in practice. However, the way users react in real-world systems highly depends on many factors that differ from one user to another such as social habits and financial constraints. Recent studies anticipated that low levels of spatial demand synchronization can result in significant savings of the capital cost of water supply systems. In this paper, an investigation on the actual demand spatial synchronization is carried out using field measurements of diurnal demand patterns for different users in a residential area located in the city of Tripoli. Results showed that users react independently and the correlation is far away from the perfect case. Key words: water demand synchronization, demand cross-correlation, diurnal demand pattern 1. Introduction The performance of a water distribution network, whether it is an existing or newly designed, highly depends on an accurate estimation of water demands such that estimated demands during the design stage could be considered similar to those evaluated in the constructed network. This similarity can ensure that the network is properly sized at an acceptable cost and acceptable levels of pressures during peak and off-peak periods. Accordingly, it is crucial to obtain an accurate picture of how the demands are distributed and allocated to nodes before a water distribution network is built or rehabilitated. This requirement is challenging to simulating networks for extended periods as it becomes essential to represent spatial patterns of demand across network nodes for peak and off-peak periods. Corresponding author: Salah H. A. Saleh, Ph.D., Assistant Professor; research areas/interests: water resources engineering. E-mail: ssaleh1974@yahoo.com. The effect of the spatial correlation of demands on the hydraulic performance and cost of water distribution networks have been an active subject among a number of researchers. A chance-constrained optimization model developed by Tolson et al. [6] was applied to a simple network. The study showed that, for a fixed level of hydraulic reliability, network cost increases with the level of cross correlation between demands. Additionally, the results of Tolson et al. pointed out that a higher level of cross correlation between network demands has the effect of producing larger fluctuations in nodal pressure accompanied with more frequent low-pressure failures. The results of Tolson et al. were confirmed by Kapelan et al. [5] and Babayan et al. [1] by the development and testing of multi-objective evaluation models to the New York tunnels problem under correlated demands. Both studies showed that correlated demands increases a network cost at a fixed level of hydraulic reliability.