New challenges in water systems include different approaches from analysis of failures and risk assessment to system efficiency improvements and new innovative designs. In water distribution networks (WDNs), the risk function is a measure of its vulnerability level and security loss. Analyses of transient flows which are associated with the most dangerous operating conditions, are compulsory to grant the system liability both in water quantity, quality, and management. Specific equipment, such as air valves are used in pressurized water pipes to manage the air inside associated with the filling process, that can also act as a control mechanism, where the major limitation is its reliability. Advanced tools are developed specifically to smart water grids implementation and operation. The water system efficiency and water-energy nexus, through the implementation of suitable, pressure control and energy recovery devices, and pumped-storage hydropower solutions, provide guidelines for the determination of the most technical cost-effective result. Integrated analysis of water and energy allows more reliable, flexible, and sustainable eco-design projects, reaching better resilience systems through new concepts. The development of model simulations, based on hydraulic simulators and computational fluid dynamics (CFD), conjugating with field or experimental tests, supported by advanced smart equipment, allow the control, identification, and anticipation of complex events necessary to maintain the water system security and efficiency.