<p>Multi-criteria decision-making (MCDM) methods are one of the most powerful current tools for sustainable policies, including environmental impact assessment in construction projects, especially water resource management projects. In the present research, the water treatment plant of Pardis city of Tehran was selected as a case study. The strategies to reduce the adverse effects of this project during the construction and operation phases were developed based on a set of criteria and sub-criteria. The criteria and sub-criteria were weighted using the Analytical Network Process (ANP) method in the next step. The results of the weighting of the criteria and sub-criteria show that the sub-criterion of the project construction cost with a weight of 0.199 at the time of construction and the sub-criterion of reducing the quality of surface and underground water with a weight of 0.128 at the time of operation has maximum importance. In the last step, the strategies to reduce the adverse effects of the design using the concept of Soft Fuzzy Set Theory (FS) in combination with the Analytic Hierarchy Process (AHP) method (FS-AHP method) were ranked for the first time in two periods of construction and operation. The results of the ranking of the alternatives show that the alternative of using light fossil fuels in cars and machinery with a weight of 4.56 at the time of construction and the alternative of creating a central wastewater treatment system with a weight of 7.14 at the time of operation of the water treatment plant have the first rank.</p>