In Sao Paulo today, a Latin American megalopolis that is now home to 20 million people, public water supplies are cut off for as long as three days at a time. But despite this draconian rationing, the Cantareira Reservoir sits at 9 percent below dead pool. A level so low that utility managers had to install new pipes into the reservoir bottom to tap water supply dregs. A controversial policy due to the fact that drawing water from so low in the pool both results in fish kills and in much more polluted water going into rivers (like the foaming Tiete) and the drinking and bathing supply.

(The Cantareira Reservoir has been bone dry for more than a year and a half now. Severe water rationing has managed to keep levels about steady for the time being. Image source: UOL.)

At least the dramatic cuts in…