Click the map for the brief review of what looks to be an important paper published in the current issue of Nature (which requires subscription for the entire article so this review in the Science section of the New York Times is important for non-subscribers).  For some, the constant reminders are tedious.  We appreciate them nonetheless because it is so much easier to forget, ignore, pretend otherwise that water is an infinite resource.  Not only is it finite, but solving this puzzle may be the next most important thing for mankind to get right:

The study underlines a problem that scientists have already pinpointed: that the demand for groundwater in several major agricultural regions of the world is unsustainable.

The analysis showed that groundwater supplies in the Upper Ganges of India and Pakistan, the Central Valley of California and the North China plain are heavily overexploited, something that was already well known before. But the new study also revealed that aquifers in Iran, western Mexico and Saudi Arabia are also being quickly depleted, Dr. Gleeson said.

He said hoped that the study and its way of quantifying the stress on an aquifer would help groundwater managers re-evaluate their policies, In a region with an overexploited aquifer, the water managers could limit how much groundwater is drawn or encourage farmers to use groundwater more efficiently when irrigating their crops, he said.

Altogether, 1.7 billion people live in areas with overextended groundwater supplies. But in an interconnected world where food travels thousands of miles, the impact stretches further, Dr. Gleeson said.

“If our agricultural systems are stressed, where the people are eating that food matters,” he said.