However, other measures may be required to ensure the required environmental flows are achieved. For example, reservoir release rules may be necessary to achieve medium or high-flow objectives at the required times, for example to ensure the higher flows required for the movement of sediment, to periodically inundate wetlands, or to trigger fish spawning or migration. Typically, senior right holders benefit from a rent situation and only use a portion of their entitlement, while new comers, who may be able to use water wisely, may be denied access to river water. The prevailing response has been supply augmentation via additional dams and reservoirs.