Water, Water. Is it everywhere?

NASA has a satellite called GRACE; it is used for gravity recovery and climate experiment. One of the interesting things it can do is predict major flooding, because it can determine saturation of the ground by water and thus its predisposition to flooding.

GRACE recently completed a study of the world's 37 largest aquifers and found that more than a third of them are being used at unsustainable rates — they are being drained far faster than natural processes can restore them. It found that 13 of the 37 aquifers, from California to the Middle East to China, were running out of water. Eight of the 13 were determined to be overstressed, with no replenishment at all. Five were declared extremely stressed or highly stressed, with some replenishment but not enough to sustain their use. An overused aquifer will collapse and no longer retain inflows of water.

The worst one was in the Middle East, the Arabian Aquifer System. It supplies water to 60 million people in the Middle East and was declared in the study to be the most overstressed water supply in the world. The Indus Basin aquifer in India and Pakistan is the second most overstressed system.