The cross-regional water diversion project has been widely applied as an important way to relieve water pressure. Study about the tradeoff between multiple regions and multiple water use sectors has caused widespread concern. In this study, an inexact two-stage water resources management model for multi-region water resources planning with a large-scale water diversion project has been developed. The water sources in 11 districts, including independent water sources and public water sources diverted from the project, are considered in the optimization model. Water supply cost and recourse cost are analyzed in the objective function. Based on interval-parameter programming and two-stage stochastic programming, uncertainties in the water resources system are described by both interval values and probability distributions. The result indicates that the water diversion project would greatly change the composition of the water resource system and settle the uneven distribution of regional water resources to achieve district-optimal allocation of water resources. In general, the proposed method can help decision-makers to formulate water management strategies for rational utilization of all kinds of water resources in different regions.