[en] Complex spatio-temporal environmental problems call for an integrated assessment of environmental systems due to their interdisciplinary nature. Within this context, the approach of Integrated Water Resource Management (IWRM) at the catchment scale, which is at the heart of advanced European environmental policy such as the Water Framework Directive (WFD), argues for integrated modelling tools and approaches. This paper examines recent technological developments that facilitate integrated modelling and focuses on a novel approach, the Open Modelling Interface (OpenMI), which allows models built by different developers to communicate at runtime. The individual models, when made compliant with the OpenMI standard, can be considered as “components” of an integrated model and seamlessly exchange data. Two OpenMI-enabled integrated modelling case studies are presented and their results critically discussed. The paper concludes with opportunities and challenges towards the design of flexible, component-based models supporting integrated environmental policy in general and the WFD implementation in particular.