A nickel mine site located in western Turkey requires approximately 135 L/s of water for 15 years. To assess the potential impacts associated with meeting this water supply requirement, we determined alternative water resources, assessed the potential impacts associated with each resource, and selected the most feasible alternative, given the environmental and technical impacts. Three options were considered: surface water, groundwater, and treated wastewater. A low-flow analysis of Gediz River was conducted for the evaluation of using surface water. For the groundwater alternative, a three-dimensional numerical groundwater flow model of the Turgutlu-Salihli aquifer was established using MODFLOW so that the impacts of withdrawal on groundwater resources could be evaluated. The wastewater option was assessed based on the amount of wastewater generated nearby (in Turgutlu). It was determined that each option is capable of supplying the required water to the mine site. However, storage of the river water in a small dam in wet seasons for use in dry seasons and using treated wastewater would have less impact on existing water users and related ecosystems.