How much water do we have on earth? In the grand scheme of things, not a whole lot according to this illustration from the Woods Hole Oceanographic Institute:
The United States Geological Survey estimates the blue sphere in the photo would be about 860 miles (about 1,385 kilometers) in diameter with a volume of about 332,500,000 cubic miles (1,386,000,000 cubic kilometers.) The sphere counts the amount of water in our oceans, lakes, rivers as well as in animals, plants and other life forms.
As the population of the earth approaches 7 billion people, the fresh water resources contained within that blue sphere will become even more scarce. Are we on the verge of a global water crisis?