**Preface to "Water Systems towards New Future Challenges"**

Water supply (WS) systems collect, store and/or treat, and distribute water among water sources and consumers. They are the transfer of drinking, irrigation, waste, storm, and industrial water from an intake to final users. This important infrastructure is becoming a dynamic environment, where new technologies and the best practices are implemented with the ambition of increasing the safety, efficiency, sustainability, and management. The monitoring system (MS), control technology (CT), managemen<sup>t</sup> strategy (MS), energy saving (ES), eco-innovative solution (EIS), and modeling decision support system (MDSS) have to be improved to obtain technical, economic, and environmental benefits in terms of research, technology, and engineering applications. The water industry is subject to changes regarding the sustainable managemen<sup>t</sup> of urban water systems. There are many external factors, including impacts of the climate change, drought, and population growth in urban centers, which lead to an increase in the responsibility to adopt more sustainable managemen<sup>t</sup> of urban waters. There are many structural challenges facing the development of modern cities, from the water supply to the population and economic activities, to the improvement of urban, industrial, and rural water sectors. Population growth results in an increase in and a concentration of water needs and a consequent need for water management. Under this reality, the use of advanced studies and technologies as well as the adoption of more robust managemen<sup>t</sup> models are necessary to better suit the critical demands in the near future. The concept of the smart water system utilizes advanced information technologies for system monitoring data to achieve greater efficiency in the resource allocation. In addition, to increase the efficiency in water loss control, the prevention and the early detection of leaks allow the development of the best practice in the asset management. A smart system uses real-time data, optimization variables, variable speed pumps, dynamic control valves, and smart meters in order to balance the demand, minimize the overpressure in aging pipelines, and save water and energy. Therefore, a sustainable water–energy nexus (WEN) arises in terms of its water and energy efficiency, reliability, and environmental integration towards smart water grids (SWGs). This is a new method for smart technology, resource management, and sustainable water infrastructure development in the near future to face climate and demand challenges.

> **Helena M. Ramos** *Editor*
