# Cyber-Physical Systems for Water Supply Network Management: Basics, Challenges, and Roadmap
## 1 Introduction  
In contemporary society, the need for potable water is constantly growing. Unfortunately, the accessibility of water is negatively influenced due to a disruption in the water cycle caused by climate change [1]. This makes water scarcity a key issue around the world. As the water scarcity problem deepens on a global scale, the need for water utilities to adopt a technological paradigm shift for effective use of water resources becomes important. The water utilities aim to supply potable water across the nation through large-scale complex water supply systems (WSSs) or water supply networks. The supply of good drinking water conforms to the objectives of the United Nation's Sustainable Development Goals. However, the achievement of this goal may be hindered by several challenges facing the smooth operation of urban WSSs. Strictly speaking, a key challenge facing the operation of WSS is the frequent water loss level that occurs in the system. The water loss due to leaking pipes occurs in all the system, even though the level varies from one system to the other. This creates a lot of further challenges to water utilities. Further challenges that may arise due to losses in the system include the relatively high cost associated with pumping due to leaks, potential adverse effect of water quality, increased water contamination level, financial losses, and improved maintenance cost to repair leaky pipes [2; 3; 4; 5; 6]. When a leak occurs in water supply networks, more energy is needed to sustain the desired level of service [2; 3; 7]. Unfortunately, the energy cost due to the additional pumping of water is a major issue. For instance, the Water Loss Control Committee of the American Water WorksAssociation have suggested that almost 10 billion kWh of energy produced in the United States is wasted annually on water losses [8]. Therefore, managing the WSSs to address these challenges is a major issue. To cope with the above challenges, water utilities have made efforts to make WSSs more intelligent by integrating information and communication technologies. As such, tremendous growth in technology provides possibilities and valuable tools to enhance the systems' operations. As a result, development in technology in sensing and instrumentation, communication and networking, and computing and control is now jointly integrated with water supply system infrastructures to enhance the water system operations. Such a system may be regarded as a cyber-physical water system (CPWS). Cyber-physical systems (CPSs) are integrations of networks, computation, and the physical environment, where embedded computing devices ceaselessly sense, monitor, and control the physical environment [9]. CPSs are very closely related to other emerging research topics, such as the Internet of Things (IoT), machine-to-machine (M2M) systems, ubiquitous, fog, and pervasive computing, but with better control capabilities. Sometimes, they are interchangeably used to mean similar concept. In recent times, CPSs have gained a lot of attention and have enjoyed tremendous growth in various areas of engineering and industrial applications [10; 11; 12; 13; 14; 15; 16; 17; 18; 19; 20; 21; 22]. Due to its relevance in engineering applications, research papers on CPSs may be found in the literature [10; 11; 12; 13; 14; 15; 16; 17; 18; 19; 20; 21; 22]. The existing body of knowledge has focused on the framework, system design, modelling, and technology implementation of CPSs [19; 20; 21; 22; 23; 24; 25; 26]. These papers are very useful, however, they only offer very limited information in the water supply system management perspective. Different from the studies in [25; 26], therefore, the objective of this paper was to relay CPS applications in the water system context and identify the limitations, research gaps, and problems to be solved in the application of CPSs to monitoring water system facilities.