Developing water quality management policies for the Chitgar urban lake: application of fuzzy social choice and evidential reasoning methods

Chitgar Lake is an artificial urban lake located in northwestern of Tehran, the capital city of Iran. It is estimated that the lake becomes highly eutrophic in the near future. In this paper, a methodology is presented for evaluating different water supply and water quality management policies proposed for this lake by utilizing evidential reasoning (ER) and fuzzy social choice (FSC) methods. The ER method can handle different kinds of uncertainties, such as fuzziness and ignorance, involved in analyzing lake water management alternatives. Since the ER method, as a multi-criteria single decision making technique, does not directly consider utilities of multiple stakeholders involved in the system, we also utilize a FSC method to reevaluate various lake water management alternatives. A set of 15 alternatives, rather than existing pattern of water supply for the lake, are proposed for the lake water quantity and quality management. Six assessment criteria are also considered for crisp or fuzzy evaluating the lake management alternatives. To evaluate the alternatives, the results of simulating the lake watershed using the storm water management model (SWMM) and model for urban stormwater improvement conceptualization (MUSIC) have been used. The application of the proposed methodology to the Chitgar Lake problem shows that using multi-criteria single decision making and multi-criteria multi-decision making methods can lead to different rankings for the same set of alternatives. Based on our evaluation, results of the FSC method, which directly incorporates the utility functions of stakeholders, look more promising.