Some stream of conciousness thoughts about water. Part of the Green's Movement's vast set of concerns is water. The US uses "too much", an average of 100-150 gallons a day. The developing world doesn't have enough. It takes 39,000 gallons of water to make a car. There are discussions about upcoming water wars where the presumed dominant commodity is water itself. The issues of water scarcity are water sanitation, water access and resource management.
One wonders whether the 'over-use' of water in the US impacts the rest of the world. Does that glass of water you don't drink at a restaraunt cause someone in Somalia to go without.? Or is it primarily a local problem?
From our limited understanding of chemistry, for the most part water is rarely consumed: a hydrogen bomb probably knocks a kilo or two out of existence and presumably some long lasting compounds bind water and take it out of circulation more or less permanently, but for the most part it used and recycled naturally. You drink you urinate, it evaporates and you drink it again.
So then, water being not destroyed, the issue becomes about contamination and allocation. Contamination by pollutants or simply by running out into the ocean and becoming salty. In the later case, the sun will cause it to evaporate again and, unless weather patterns keep rain off the land masses it will return. But there is still the speed with which the cycle occurs. If it is running off faster than it evaporates, you have problems. Contamination can also be addressed by evaporation, but timing again is an issue. And if the contamination is in the ground water than you need some other technical solution to address the problem.
But water can also end up bound in crops, livestock, and water logged Americans, when other humans need it just to survive. It begins to look like a money velocity problem. So in theory, you could try and keep the velocity of water high and keep it from getting horded in toilets, artificial vegas lakes, green lawns or whatever. A true liquidity crisis. If only the Fed could just run the presses.