Even though it is probably true that in more recent times the water planning and management procedures used in most parts of the world appear to have been reasonably adequate, it is now becoming increasingly questionable. A sustainable approach is now required. Yet, it is quite one thing to say “sustainable” in every breath, and another to create a sustainable system when the definition is so vague. A number of questions will certainly have to be answered if water resources experts are to become successful ‘sustainable water resource developers’. Unified concepts for designing, operating, and maintaining water resource systems that could assure planners of a sustainable product are still to be developed.