Multi-objective optimal operation of urban water supply systems

The world’s water resources are rapidly deteriorating due to the combined effects of global warming, climate change, population growth and fast development, posing new challenges to water resources managers. Conflicting objectives and expectations of various stakeholders have led to increasing interests in the consideration and resolution of multiple social, economic, environmental and supply sustainability objectives in the management of water supply systems, especially during extended dry periods. This study attempted to develop and assess the potential of a generic decision support framework to assist in evaluating alternative operating rules for multi-purpose, multireservoir urban water supply systems. The multi-objective outranking approach which facilitated the incorporation of stakeholder preferences in the decision making process is a main focus area in this research. The main elements of the framework are illustrated on a case study of the Melbourne water supply system, demonstrating its capabilities for evaluating alternative operating rules under single or group decision-making situations. Eight performance measures (PMs) were identified under four main objectives to evaluate the system performance related to sixteen pre-selected alternative operating rules. Three major stakeholder groups, namely, resource managers, water users and environmental interest groups were represented in hypothetical decision making situations. An interviewerassisted questionnaire survey was used to derive stakeholder preferences on PMs in terms of preference functions and weights as required by the PROMETHEE/GAIA method and its computer software tool Decision Lab 2000. A total of 97 personnel selected from Melbourne Water and Victoria University participated in the survey expressing their preferences on the eight PMs. Finally, an overall ranking for alternative operating rules is obtained together with other output results, which focused on the best compromises between the objectives considered. The method yields reliable and robust results in terms of varying group compositions considered in the case study. The major innovation of this project is the development of a transparent and intuitive multi-objective decision support framework that has potential to be developed for evaluating alternative operating rules for urban water supply systems.