Resilience of Water Supply Systems: The Case Study of Valle Umbra, Italy

Water systems are increasingly exposed to stress conditions that challenge their ability to maintain adequate service levels over time. In this context, resilience has emerged as a key concept for assessing system performance. This study proposes a quantitative framework to assess water supply system resilience under varying operating conditions by integrating hydraulic simulation results with system-level performance indicators. Unlike traditional approaches, resilience is not defined solely by topological redundancy or by the response to pipe failures, but by the capability of dendritic systems to cope with stress conditions caused by resource shortages and demand increases. The proposed indicators were applied to real-world water supply systems managed by Valle Umbra Servizi S.p.A. (VUS) in the Umbria region of Italy. The resilience indices are derived from mass and energy balances evaluated exclusively under feasible operating conditions, i.e., excluding the energy that cannot be mobilized due to pipe transfer capacity constraints; this prevents the inclusion of surplus terms that are not effectively usable for system operation. The significance of these indices was tested by analyzing system improvements and interconnections between two operating water supply systems managed by VUS. The interconnection along the Flaminia road results in a 36.8% increase in resilience compared with the interconnection along the Monti Martani, according to one of the proposed indices. The proposed approach is general and transferable and can support water utilities and decision-makers in identifying critical components and prioritizing interventions aimed at enhancing system resilience.