We all know, or at least hear it said, that our planet is mostly composed of water. About 71% of the earth's surface is composed of this precious liquid, and 96.5% of this total is salt water. But in reality we have very little water on earth. This last sentence seems contradictory but if we compare all the water we have on the planet (oceans, lakes, water in the air, icebergs and snow) with the volume of the whole planet we will see that we do not have much water.
In the image below created by the US Geological Survey we can see this comparison (click on the image to enlarge):
In the image above, the largest water bubble represents all the water that exists on earth in a circumference with a diameter of 1,385 kilometers. The medium bubble represents all the liquid fresh water of the Earth as groundwater, water from swamps, rivers and lakes with a circumference of 272.8 kilometers in diameter, much of it is inaccessible to humans, being in deep soil. The smallest bubble, on the other hand, represents all the fresh water in all the lakes and rivers on the planet, with only 56.2 kilometers in diameter, this one is available for immediate consumption and almost all the water consumed on earth by living beings comes from this tiny bubble.
When looking at the above images the first thing that comes to us head is, this study is wrong, we have so little water on earth. The truth, and we have to have notion of this, is that all the water that exists on our planet is practically on the surface. One of the deepest points of our planet is in the Pacific Ocean and it is only 11 a thousand meters deep, the Marianas Fossil, the rest of the planet's waters are at a much more superficial level.
In the table below you will be able to see how is distributed all the water of our planet.
| Water source | Volume of water in cubic kilometers | Percentage of fresh water | Percentage of total water |
| Oceans, seas and bays | 1,338,000,000 | — | 96.54 |
| Polar caps, glaciers and snow | 24,060,000 | 68.6 | 1.74 |
| Groundwater | 23,400,000 | — | 1.69 |
| Fresh | 10,530,000 | 30.1 | 0.76 |
| Salinas | 12,870,000 | — | 0.93 |
| Soil Moisture | 16,500 | 0.05 | 0.001 |
| Ice | 300,000 | 0.86 | 0.022 |
| Lagos | 176,400 | — | 0.013 |
| Fresh | 91,000 | 0.26 | 0.007 |
| Salinas | 85,400 | — | 0.007 |
| Atmosphere | 12,900 | 0.04 | 0.001 |
| Swamps | 11,470 | 0.03 | 0.0008 |
| Rios | 2,120 | 0.006 | 0.0002 |
| Agogo | 1,120 | 0.003 | 0.0001 |
| Source: Igor Shiklomanov's chapter “World fresh water resources” in Peter H. Gleick (editor), 1993, Water in Crisis: A Guide to the World's Fresh Water Resources (Oxford University Press, New York). | |||
