One of the things Compass Data Center's Chris Crosby, Google's Joe Kava and I will regularly discuss is the lack of appreciation for how scarce water is.
How scarce is water on the earth? Consider this image that shows how big all of the Earth's water is compared to the size of Earlth.
Picture of Earth showing if all Earth's water (liquid, ice, freshwater, saline) was put into a sphere it would be about 860 miles (about 1,385 kilometers) in diameter. Diameter would be about the distance from Salt Lake City, Utah to Topeka, Kansas, USA.
Credit: Illustration by Jack Cook, Woods Hole Oceanographic Institution (©); Howard Perlman, USGS.View full size
About 70 percent of the Earth's surface is water-covered, and the oceans hold about 96.5 percent of all Earth's water. But water also exists in the air as water vapor, in rivers and lakes, in icecaps and glaciers, in the ground as soil moisture and earthgwaquifer.html, and even in you and your dog. Still, all that water would fit into that "tiny" ball. The ball is actually much larger than it looks like on your computer monitor or printed page because we're talking about volume, a 3-dimensional shape, but trying to show it on a flat, 2-dimensional screen or piece of paper. That tiny water bubble has a diameter of about 860 miles, meaning the height (towards your vision) would be 860 miles high, too! That is a lot of water.
The Earth's water would be 860 miles in diameter, and the Earth is 7,900 miles in diameter.
Water seems much more scarce now doesn't it.