IRA-WDS: A GIS-based risk analysis tool for water distribution systems

This paper presents the development of a new software tool IRA-WDS. This GIS-based software predicts the risks associated with contaminated water entering water distribution systems from surrounding foul water bodies such as sewers, drains and ditches. Intermittent water distribution systems are common in developing countries and these systems are prone to contamination when empty. During the non-supply hours contaminants from pollution sources such as sewers, open drains and surface water bodies enter into the water distribution pipes through leaks and cracks. Currently there are no tools available to help engineers identify the risks associated with contaminant intrusion into intermittent water distribution systems. Hence it is anticipated that IRA-WDS will find wide application in developing countries. The paper summarises the details of the mathematical models that form the basis of IRA-WDS. It also describes the software architecture, the main modules, and the integration with GIS using a tight coupling approach. A powerful GUI has been developed that enables data for the models to be retrieved from the spatial databases and the outputs to be converted into tables and thematic maps. This is achieved seamlessly through DLL calling functions within the GIS. This paper demonstrates the application of the software to a real case study in India. The outputs from IRA-WDS are risk maps showing the risk of contaminant intrusion into various parts of the water distribution system. The outputs also give an understanding of the main factors that contribute to the risk.