After the ecological and carbon footprint calculators, there's now a water footprint calculator, allowing you to calculate your own water consumption. The footprint is defined as "the total volume of freshwater that is used to produce the goods and services consumed".
The results are quite enlightening. Though food, especially meat and coffee, appears to be a main culprit of a big footprint, the catch-all category of "industrial" consumption takes up three times as much. (The site offers a wealth of information, but is curiously vague on this category.)
It would seem there's a difference between a water footprint and a carbon footprint, as water, unlike fossil fuels, is a renewable resource. In other words, fossil fuel consumption is a zero sum game, while water consumption is not. This is a bit too theoretical though, because what matters is the availability of water in a given time and place.
Water is a renewable resource, but that does not mean that its availability is unlimited. In a certain period, precipitation is always limited to a certain amount. The same holds to the amount of water that recharges groundwater reserves and that flows through a river. Rainwater can be used in agricultural production and water in rivers and aquifers can be used for irrigation or industrial or domestic purposes. But in a certain period one cannot use more water than is available. A river can be emptied and in the long term one cannot take more water from lakes and groundwater reservoirs than the rate with which they are recharged.
With this in mind, the national water footprints are also interesting. The Netherlands, for instance, while having a water footprint slightly below global average, has 89% of its footprint outside the country. Much of the water imported (in the form of products like fruit, coffee, cotton) comes from countries with serious water scarcity.