© Craig Chesek

All Earth's lakes and rivers, including the dramatic Godafoss waterfall in northern Iceland, make up less than one-fiftieth of one percent of the water on the planet.

In the many places where water is scarce, people show great ingenuity in getting it: collecting and keeping what little rain falls, drilling wells or--if they can afford it--removing salt from seawater to produce fresh water for drinking or farming. But ingenuity has its limits, and we may be reaching them.

Today, more than one billion people still cannot get enough safe drinking water to keep them healthy. That kind of water scarcity isn't just about too little rain--it's a problem of politics, infrastructure, and sustainable use.