A Comparative Study of Flexibility in Water Allocation in the Context of Hydrologic Variability

River flow that is characterized by variability requires commensurate flexibility in allocating water so that water users are able to plan their activities and respond accordingly. An indicator-based assessment method is proposed in this study to evaluate the flexibility of water allocation, based on a concept that a flexible water allocation regime provides greater opportunity for users to freely decide individual water use and leads to more variability and diversity for water consumption among the users. This is demonstrated by using historical water-use data and applying the assessment method in three river basins with different water allocation regimes. These allocation regimes include the seasonal and volumetric water allocation system in the Yellow River of China, duration-based water allocation in Northwestern China, and capacity sharing in southern Queensland in the northern Murray Darling Basin of Australia. Historical water-use variability and diversity are defined and assessed. The result shows that water allocation flexibility varies across the different water entitlement regimes. Duration-based water allocation, a type of allocation that provides the highest degree of water-use autonomy, is ranked as the most flexible regime. Seasonal water allocation, which has the highest level of centralized regulation, shows the lowest flexibility. The proposed indicator based assessment method would be useful for evaluating the flexibility of policy options for water allocation. This could be helpful for improving the capability of water allocation regimes to cope with the changing environment and improving the effectiveness of water allocation systems.