India, March 27 -- What does it mean for a region to run out of water?

It's a bit like financial bankruptcy, says Kaveh Madani, director of the United Nations thinktank on water, the UN University Institute for Water, Environment and Health (UNU-INWEH).

At first, it feels manageable, with cutbacks, delayed instalments, a little borrowing, and moving things around. But the interest piles up.

Once-full rivers become seasonal, aquifers turn saline; as groundwater levels sink, the ground itself may begin to subside. Pretty soon, one is staring at the bottom of the barrel.

"This is not a water crisis anymore. This is water bankruptcy," Madani says.

Once things reach this point, the familiar remedies of water cuts and water trains make lit...