Integral modelling for water security beyond the water cycle

Water pollution is a critical constraint to water security, impacting natural environment and reducing the resilience of infrastructure. Conventional approaches, often focused on modelling the hydrological cycle, struggle to capture the wider interactions between natural and engineered systems in which water is embedded. However, water systems are closely linked with transport, food and energy, creating feedback that remains poorly understood. In this Perspective, we propose that advancing water security requires integral modelling frameworks that move beyond water-cycle-only approaches. Such frameworks provide a modular, graph-based representation capable of linking physical systems with human behaviour and decisions. We illustrate this conceptually through the Water Systems Integration Modelling framework, showing how its modular development can extend modelling beyond the water cycle. As an example, we outline how tyre wear pollution can be conceptualised through pathways that connect water and food systems. We conclude by highlighting three priorities for future work: developing interdisciplinary processes for cross-sectoral integral modelling, evaluating systemic portfolios of interventions, and extending applications to sectors such as energy, all of which will shape the next generation of integral modelling for water security.