It’s easy to look at a portrait of Earth and think of our home as a water planet. After all, 75 percent of the surface is covered with water. But the thin skin of liquid that surrounds our rocky home is misleading—if you took all the water on the planet and bunched it into a ball, that ball would be less than half the diameter of the Moon. That’s not a huge amount of water.
Plus, the proportion of water that humans can use for daily use is actually pretty small. Most of the world’s water is saltwater in the oceans. Only about three percent of the water is fresh. Half of that is locked in glaciers, the polar ice caps and snow.
Almost all of the rest flows through the world’s lakes, streams, rivers, soils and groundwater. A tiny percentage is water vapor in the atmosphere, driving our weather and climate. That doesn’t leave much for the 7 billion people on the planet, and even less for some populations because all that water isn’t evenly Read more
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