How Much Water Does Earth Have?


All of Earth's Water Collected in a Sphere

As you know, the Earth is a watery place. But just how much water exists on, in, and above our planet? This picture shows the size of a sphere that would contain all of Earth's water in comparison to the size of the Earth.

You're probably thinking I missed a decimal point when running my calculator since surely all the water on, in, and above the Earth would fill a ball a lot larger than that "tiny" blue sphere sitting on the United States, reaching from about Salt Lake City, Utah to Topeka, Kansas. But, no, this diagram is indeed correct.

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 ((c)); Howard Perlman, USGS. Larger version

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.

But, as far as people are concerned, almost all of Earth's water is not usable in everyday life. Water on, in, and above the Earth is never sitting still, and thanks to the water cycle our planet's water supply is constantly moving from one place to another and from one form to another. Things would get pretty stale without the water cycle!

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.

Even though you may only notice water on the Earth's surface, there is much more freshwater stored in the ground than there is in liquid form on the surface. In fact, some of the water you see flowing in rivers comes from seepage of groundwater into river beds. Water from precipitation continually seeps into the ground to recharge the aquifers, while at the same time water from underground aquifers continually recharges rivers through seepage.


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