Once the Basin Plan and related policies are in place, the Commonwealth Environmental Water Reserve will constitute a significant portion of the water resources of the Murray–Darling Basin. Even in the absence of the Basin Plan, non-trivial water resources will be at the disposal of the Federal government to achieve environmental outcomes. The Basin Plan commits governments to protecting a number of important components of the ecology of the Basin, but it is not at all clear how this is to be achieved. Setting aside some of the gaps in the scientific knowledge about the Basin, this article deals with the institutional arrangements for managing such a large volume of water across an area as large and diverse as the Murray–Darling Basin. We argue in support of a devolved model but caution against a one-size-fits-all approach that could replicate the mistakes of earlier reforms to water property rights.