Dear Umbra,

What percentage of the Earth's water is drinkable? What are the remaining percents in categories, such as salt water, polluted water (polluted with what?), and frozen water? And where can I find these statistics?

Scott
Bozeman, Mont.

Dearest Scott,

About 70 percent of the Earth's surface is constantly wet. Of all that water, only 2.5 percent, or 8.4 million cubic miles, is not salty. Quite a bit of the freshwater is rather stale, since it's been stuck for eons in glaciers, ice caps, and Siberia: 5.9 million cubic miles, to be exact. Still more freshwater is too far from human settlement for our use. The accessible freshwater left over after all these caveats is less than 0.08 percent of the water on the planet. I came across a handy image to help you visualize this number: If all of the Earth's water were in a five-liter container, accessible freshwater would be not quite a teaspoon of that. (For all you metricphobes: a liter is about a quarter of a gallon, so five liters is equivalent to a gallon and a quarter -- say, a jug of cider and a quart of milk, of which you only get a teaspoon of the beverage of your choice.)

Now that's fresh!

Photo: Ann Petersen.

Canada is where I got these stats. Yes, I've moved to Canada, and I hope you all will join me here. It's freakin' cold, but I just couldn't take it anymore down there in eco-nazi, anti-values, Kerry-voting Seattle. Also, there was the allure of Environment Canada, this great nation's counterpart to the U.S. EPA, which provides such useful information on water availability. If you hunt about on the page, you'll find all their references and sources and soon be swimming happily about in data.

Polluted-water statistics are often given in terms of human population. UNESCO estimates that there are 1.1 billion people without sufficient drinking water worldwide. And according to the World Wildlife Fund, 3.3 billion people rely on contaminated water supplies. Just what they're contaminated with, I'm going to leave to your imagination or to another column, because the list of water pollutants worldwide would overwhelm Grist's mainframe.

Moistly,
Umbra

• Comments