Inland waterways are large-scale networks that are mainly used for navigation. They require optimal water resource management, particularly when navigation demand is expected to increase in the near future. Moreover, water resource management must be adaptive in the context of global change to face extreme events, such as drought and flood, that are more frequent and of greater magnitude. To deal with the complexity of inland waterways, the increase of navigation demand and extreme events, an adaptive allocation planning of water resource is proposed in this paper. It aims to determine an optimal water allocation plan based on an integrated model of inland waterways, a weighted flow graph, and a quadratic optimization technique. The criterion to optimize is the volume contained in each part of the network at each step time, which leads to guaranteeing the navigation conditions whatever the hazards that can occur. The proposed techniques are implemented and tested by considering the most relevant part of the inland waterways of the north of France around the most vulnerable reach-the Cuinchy-Fontinettes reach. Several scenarios on the increase of navigation demand and on drought and flood periods are built to highlight the performance of the proposed approach. The scenarios show that this part of the inland navigation network should not be strongly affected by these expected modifications. © 2018 American Society of Civil Engineers.