Groundwater is the resource we are depleting, because everything else runs in a circle.  Here is a good worldwide groundwater study, based partly on gravity inversions from the GRACE twin satellites: <a href="http:&#x2F;&#x2F;www.jpl.nasa.gov&#x2F;news&#x2F;news.php?feature=4626" rel="nofollow">http:&#x2F;&#x2F;www.jpl.nasa.gov&#x2F;news&#x2F;news.php?feature=4626</a><p>The conclusion is: Probably the most at-risk aquifer (based on people affected and severity) is in the Gangetic plain in northern India.  There are also critically threatened aquifers in the Arabian peninsula, southeast China, and our own Sacramento Valley.<p>This conclusion is supported by other hydrological modeling groups as well (e.g., the very highly-cited, but older, <a href="http:&#x2F;&#x2F;onlinelibrary.wiley.com&#x2F;doi&#x2F;10.1029&#x2F;2010GL044571&#x2F;full" rel="nofollow">http:&#x2F;&#x2F;onlinelibrary.wiley.com&#x2F;doi&#x2F;10.1029&#x2F;2010GL044571&#x2F;full</a>)