This drawing shows the size of a sphere that would contain all of Earth’s water in comparison to the size of the Earth. The sphere includes all the water in the oceans, seas, ice caps, lakes and rivers as well as groundwater, atmospheric water, and even the water in you, your dog, and your tomato plant.
Are you surprised that this water sphere looks so small? It is only small in relation to the size of the Earth. Remember, this image is a representation of 3 dimensions, so you are looking at volumes. What it does show is that, in comparison to the globe, the oceans lie in a “thin film” of water on the outer surface.
The data used on this page comes from Igor Shiklomanov’s estimate of global water distribution, shown in a table below the image.
The vast majority of water on the Earth’s surface, over 96 percent, is saline water in the oceans. But it is the freshwater resources, such as the water in streams, rivers, lakes, and groundwater that provide people (and all life) with most of the water they need everyday to live. Water sitting on the surface of the Earth is easy to visualize, and your view of the water cycle might be that rainfall fills up the rivers and lakes. But, the unseen water below our feet is critically important to life, also. How would you account for the flow in rivers after weeks without rain? In fact, how would you account for the water flowing down this driveway on a day when it didn’t rain? The answer is that there is more to our water supply than just surface water, there is also plenty of water beneath our feet.
Just how much water is there on (and in) the Earth? Here are some numbers you can think about:
- If all of Earth’s water (oceans, icecaps and glaciers, lakes, rivers, ground water, and water in the atmosphere was put into a sphere, then the diameter of that water ball would be about 860 miles (about 1,385 kilometers) across, a bit more than the distance between Salt Lake City, Utah to Topeka, Kansas. The volume of all water would be about 332.5 million cubic miles (mi3), or 1,386 million cubic kilometers (km3). The picture at the top of this page illustrates this. A cubic mile of water equals more than 1.1 trillion gallons. A cubic kilometer of water equals about 264 billion gallons.
- About 3,100 mi3 (12,900 km3) of water, mostly in the form of water vapor, is in the atmosphere at any one time. If it all fell as precipitation at once, the Earth would be covered with only about 1 inch of water.
- The 48 contiguous United States receives a total volume of about 4 mi3 (17.7 km3) of precipitation each day.
- Each day, 280 mi3 (1,170 km3)of water evaporate or transpire into the atmosphere.
- If all of the world’s water was poured on the United States, it would cover the land to a depth of 90 miles (145 kilometers).
- Of the freshwater on Earth, much more is stored in the ground than is available in lakes and rivers. More than 2,000,000 mi3 (8,400,000 km3)of freshwater is stored in the Earth, most within one-half mile of the surface. But, if you really want to find freshwater, the most is stored in the 7,000,000 mi3 (29,200,000 km3) of water found in glaciers and icecaps, mainly in the polar regions and in Greenland.