Improved regional water planning is the foundation of the National Water Initiative (NWI), which states 'water planning is an important mechanism to assist governments and the community to determine water management and allocation decisions to meet productive, environmental and social objectives'. With increasing water scarcity, effective water planning is the mechanism by which communities determine the pool of water available for consumptive purposes, and the environmental outcomes they seek to achieve in their waterways. In surface and groundwater systems that are already over-allocated or stressed, the NWI commits governments to return them to sustainable levels of extraction, and we must define what this means. The NWI also requires the identification and management of systems of high conservation value. The NWI provides the foundation for the market to be used to allocate water between competing consumptive uses. It envisages trade between rural and urban, as well as Governments standing in the market place to recover water from willing sellers in over-allocated systems. The sort of comprehensive water planning envisaged by the NWI is new for Australia, and is being developed in most jurisdictions. While this is still work in progress, there are some key lessons already that are worth considering.