Post-earthquake fires often cause more severe losses than the earthquakes themselves, highlighting the critical role of water distribution networks (WDNs) in mitigating fire risks. This study proposed an improved assessment framework for the post-earthquake firefighting functionality of WDNs. This framework integrates a WDN firefighting simulation model into a cloud model-based assessment method. By combining seismic damage and firefighting scenarios, the simulation model derives sample values of the functional indexes through Monte Carlo simulations. These indexes integrate the spatiotemporal characteristics of the firefighting flow and pressure deficiencies to assess a WDN’s capability to control fire and address fire hazards across three dimensions: average, severe, and prolonged severe deficiencies. The cloud model-based assessment method integrates the sample values of functional indexes with expert opinions, enabling qualitative and quantitative assessments under stochastic–fuzzy conditions. An illustrative study validated the efficacy of this method. The flow- and pressure-based indexes elucidated functionality degradation owing to excessive firefighting flow and the diminished supply capacity of a WDN, respectively. The spatiotemporal characteristics of severe flow and pressure deficiencies demonstrated the capability of firefighting resources to manage concurrent fires while ensuring a sustained water supply to fire sites. This method addressed the limitations of traditional quantitative and qualitative assessment approaches, resulting in more reliable outcomes.

The firefighting capacity of water distribution networks following earthquakes is essential for achieving the Sustainable Development Goals on resilient infrastructure and sustainable communities. Isolating broken pipes to curb leakage can preserve water supply, but the effects of such operations on post-earthquake firefighting remain incompletely understood. Here, we develop an improved valve closure decision method for post-earthquake firefighting that balances leakage reduction with water transmission capacity. Using this method as a basis, we examine how ground motion intensity, domestic water curtailment, firefighting flow, the number and spatial distribution of fires, valve layout, and valve closure policy jointly affect firefighting. A case study on a benchmark network shows that the valve closure scheme generated by the decision method reduces leakage by about 60–75% under spatially dispersed fires and the N − 1 valve layout. Compared with no isolation, it also raises delivered firefighting flow from under 20% to over 80% of the design value. On average, these schemes deliver flow 5–10% below the optimal scheme. Valve placement, however, has a strong influence: under the N − 2 layout, alternative placements can alter delivered flow by 10–20%. Adverse conditions—widespread pipe leakage caused by strong ground motion, hydraulic overload from clustered fires or firefighting flow surges, and sharp pressure reductions at fire nodes in low-pressure zones owing to excessive flow or leakage—can prevent the schemes from improving firefighting flow. These findings indicate that effective firefighting requires a combination of rational valve placement and closure schemes with seismic retrofitting of pipes and fire hazard mitigation.