A GIS based approach to assess the vulnerability of water distribution systems

It is a fact that water distribution systems in most European cities are reaching the end of their lifetime; pipe breaks and leaks have had a significant increase in the last years, and there is no evident reason for the future trend to be inverted in the short-term horizon. The history of water networks rehabilitation leans on the so called re-active approach: first the failure occurs, then comes the intervention. Efforts are recently being undertaken in order to establish a rational framework for maintenance decision-making in water distribution systems, based on a new logic: a rehabilitation carried out before the problem takes place is to be preferred, thanks to its higher effectiveness and to the troubles it is able to prevent rather than cure (pro-active approach). European projects developed during the 5th Framework Programme focused on water asset management (CARE-S and CARE-W) have been looking at risk in terms of economic, social and environmental probability of failure considering that system knowledge is a pre-requisite for obtaining an efficient system management. Nevertheless, the experience demonstrated that availability of data is sometimes the first problem to be addressed and the application of advanced management approaches is sometimes unfeasible because of the lack of a long term monitoring strategy. Data on failure paths in urban networks is piecemeal and not available for feeding complex risk based approaches and a complete damage analysis is not practical (multi-objective approaches; Failure Modes and Effects Analysis; etc.). In reality, risk and its perception permeate the decision making process and, providing better insights of the system, the use of advanced technologies will be able to better support informed decision making about system management and rehabilitation, empowering the existing tools and approaches. As a consequence of our past experiences in applying decision support systems to Italian case studies, the aim of this study was to move backwards: starting from a typical Italian case study, we defined what can be evaluated, analysed or calculated according to what can be obtained from end – users in terms of data quality and quantity. The selected case study is a drinking water system supplying 140.000 inhabitants with a 2200 m3/h water demand and a 700 km length: Reggio Emilia town located in the northern part of Italy.