An automated design method for the water networks under uncertain process conditions has been developed. To deal with the uncertainty problem, the installation of buffer tank and the installation of supplementing pipelines are systematically considered in the design of water networks. The cost-effective and feasible distribution and reuse of water within the network is identified from the superstructure-based optimisation model, with which all the operational constraints and fluctuating operating characteristics for water-using operations are fully and simultaneously reflected. The optimisation framework provides rigorous economic evaluation of the network through trade-off between operating and capital costs under uncertainty. The conceptual insight related to the design of water networks is incorporated in developing a reliable solution strategy which can effectively deal with the difficulty in solving the mixed-integer nonlinear programming problem. Case studies are given to validate the proposed model and demonstrate the importance of considering uncertain process conditions in the design and optimisation of water networks. (C) 2011 Elsevier B.V. All rights reserved.