Models in practice: Experience from the water supply system of Athens

The water supply system of Athens is an extensive and complex hydrosystem that lies over an area of around 4000 km2 and comprises multiple resources, surface and groundwater, as well as an extended network of aqueducts and pumping stations. Due to the multiple levels of complexity involved, its operation and management is a really challenging task. The research team ITIA from the National Technical University of Athens has developed an advanced modelling framework, which is implemented within a decision support system; the system is fully operational and continuously improved. An overview of the key philosophical issues is essential to understand the foundation of the entire modelling concept. In this context, we reveal the importance of building models that are holistic and parsimonious, and also account for the inherent uncertainty of the hydrological fluxes, treating them as stochastic processes. Taking advantage of the case study of Athens, the most significant modelling aspects are presented, while their applicability is tested against some representative problems of high practical interest. The presentation is accompanied by a short demonstration of the related software tools, most of which are free and open-source.