Water network synthesis contributes to cost reduction and the conservation of water resources by reducing water consumption. A mathematical optimization model is developed in this study to synthesize an environmentally friendly water network system (WNS) by minimizing environmental impacts of a WNS. The concept of life cycle assessment (LCA) is integrated into the objective function of the model to evaluate the environmental effect scores (EESs) of principal contributors to the environmental impacts of a WNS and to optimize tradeoffs among their EESs. The mass balances are formulated from the superstructure model, and the constraints are formulated to take into account the real situation in industrial plants. A case study demonstrates the effect of the objective function on the configuration and environmental performance of a WNS and validates the mathematical optimization model. This model can be used for the design for environment (DfE) of WNSs in the context of sustainable development.