An integrated system dynamics – cellular automata model for distributed water-infrastructure planning

Modern distributed water-aware technologies (including, for example, grey water recycling and rainwater harvesting) enable water reuse at the scale of household or neighbourhood. Nevertheless, even though these technologies are in some cases economically advantageous, they have a significant handicap compared to the centralized urban water management options: it is not easy to estimate a priori the extent and the rate of the technology spread. This disadvantage is amplified in case of additional uncertainty due to expansion of an urban area. This overall incertitude is one of the basic reasons the stakeholders involved in urban water are sceptical about the distributed technologies, even in the cases these appear to have lower cost. In this study, we suggest a methodology that attempts to cope with this uncertainty by coupling a Cellular Automata and a System Dynamics model. The Cellular Automata model is used to create scenarios of urban expansion including the suitability of installing water-aware technologies for each new urban area. Then, the System Dynamics model is used to estimate the adoption rate of the technologies. Various scenarios based on different economic conditions and water prices are assessed. The suggested methodology is applied to an urban area in Attica, Greece.