This paper takes as its starting point today's paradoxical situation where a global water crisis is threatening a world in which water illiteracy is widespread among those expected to cope with that crisis. This creates a huge communication challenge for hydrologists, having to brief decision makers, diplomats and politicians in a manner that is simplistic without being water-reductionistic. The paper proposes some simple explanatory models, to be used for explaining and visualizing fundamental man/water interactions. It also discusses environmental sustainability criteria and their consequences in terms of the capacity to support water dependent populations. Large stress is put on land/water interactions. The paper ends with a conceptual framework based on the water cycle, distinguishing between rural and urban water use, water structures for mobilizing water for such uses, side effects, and key points for societal control mechanisms.