280 Introduction Increasng competton among stakeholders for lmted water resources, combned wth the relatve absence of new and cheaper water resources, have led to the need for sustanable water resources systems. Sustanable water resources systems are desgned and managed to contrib�te to the aims and objectives o the socety, now and n the future, whle mantanng ther ecologcal, envronmental, and hydrologcal ntegrty (ASE, 1998; U�ESO, 1999). To have s�stainable water resources systems, t s necessary to rank �ater reso�rces projects, especiall inter-basin �ater transfers: • To cope �ith limited �ater, nancial and h�man reso�rces; • To allow for mult crtera decson�makng instead o single criterion decision-making; • To avod the opportunty costs of delay n decision- making; • To resolve conict among stakeholders; and s; and • To simpli the administration o projects. o projects. Besdes techncal functons, the choce among alternative �ater reso�rces projects is generall based Fuzzy Multiple Attribute Decision Making on Water Resources Projects Case Study: Ranking Water Transfers to Zayanderud Basin in Iran Mahdi Zarghaami, Reza Ardakanian, Department of Civil Engineering, Sharif University of Technology, Tehran, Iran, and Azizolah Memariani Department of Industrial Engineering, Bu-Ali Sina University, Hamedan, Iran Abstract: In this study, in order to create a decision-making model on water resources projects, a hierarchy of criteria has been developed by public participation. The Value Management methodology has been used for extraction of the effective criteria and attributes in the scope of Integrated Water Resources Management (IWRM). The hierarchy is generic for water resources management in the Islamic Republic of Iran. Since the evaluations of alternatives with respect to some attributes are uncertain and vague, fuzzy set theory has been used. By merging fuzzy set theory and multi-attribute decision-making a new Decision Support System (DSS), namely FDM, has been developed to compare different alternatives. As an innovation, FDM accepts evaluations of alternatives with respect to the attributes as crisp variables, fuzzy variables, and linguistic variables. FDM embodies an expert system whose duty is to choose an appropriate method among the SAW, Fuzzy SAW, TOPSIS or Fuzzy TOPSIS based on the characteristics of the problem. The central and Southeastern regions of Iran are considered arid regions, suffering from water shortages. In this paper, water transfers to the Zayanderud basin in Iran have been modeled by FDM. Successful application of this DSS in this study allows for its application by water authorities in other case studies. Keywords: inter-basin water transfer, hierarchy of criteria, multi attribute decision making, fuzzy set theory, DSS. Internatonal Water Resources Assocaton Water International, Volume 32, Number 2, Pg. 280�293, June 2007 © 2007 Internatonal Water Resources Assocaton