A Sweet Briar College Learning Resource
Water in the World Today
Professor Sang Hwang
We live on a water planet, however most of it is covered in salt water, covering about 71 per cent of the earth's surface. The biotic world is also made up mostly of water, 60per cent of tree's weight is water, in animals including humans the figure is about 50-65 per cent water. In terms of human use, only a small fraction is available for our use.
Oceans contain 97 per cent by volume, which is too salty for drinking, irrigation or industrial use. The 3 per cent of earth's total water is considered fresh water. About 2.997 per cent of this fresh water is trapped in polar ice caps and deep within earth surface which is too costly to extract.
Thus only .003 per cent of earth's total available water by volume is available for human use. If the worlds water was contained in 100 liters or 26 gallons, then what is readily available to us would amount to one-half teaspoon.
H20 - The Mystery, Art, and Science of Water
Chris Witcombe and Sang Hwang
Sweet Briar College