The Earth is a watery place. But just how much water exists on, in, and above our planet? About 71 percent of the Earth’s surface is water-covered, and the oceans hold about 96.5 percent of all Earth’s water. Water also exists in the air as water vapor, in rivers and lakes, in icecaps and glaciers, in the ground as soil moisture and in aquifers, and even in you and your dog.

Water is never sitting still. 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!

Spheres showing:
(1) All water (largest sphere over the western U.S., 860 miles (1,385 kilometers) in diameter)
(2) Fresh liquid water in the ground, lakes, swamps, and rivers (mid-sized sphere over Kentucky, 169.5 miles (272.8 kilometers) in diameter), and
(3) Fresh-water lakes and rivers (smallest sphere over Georgia, 34.9 miles i(56.2 kilometers) n diameter).

Credit: Howard Perlman, USGS; globe illustration by Jack Cook, Woods Hole Oceanographic Institution (©); and Adam Nieman.

About 71 percent of the Earth’s surface is water–covered, and the oceans hold about 96.5 percent of all Earth’s water. Water also exists in the air as water vapor, in rivers and lakes, in icecaps and glaciers, in the ground as soil moisture and in aquifers, and even in you and your dog.

All Earth’s water in a bubble

The globe illustration shows blue spheres representing relative amounts of Earth’s water in comparison to the size of the Earth. Are you surprised that these water spheres look so small? They are only small in relation to the size of the Earth. This image attempts to show three dimensions, so each sphere represents “volume.” The volume of the largest sphere, representing all water on, in, and above the Earth, would be about 332,500,000 cubic miles (mi3) (1,386,000,000 cubic kilometers (km3)), and be about 860 miles (about 1,385 kilometers) in diameter.

The smaller sphere over Kentucky represents Earth’s liquid fresh water in groundwater, swamp water, rivers, and lakes. The volume of this sphere would be about 2,551,000 mi3(10,633,450 km3) and form a sphere about 169.5 miles (272.8 kilometers) in diameter. Yes, all of this water is freshwater, which we all need every day, but much of it is deep in the ground, unavailable to humans.

Do you notice the “tiny” bubble over Atlanta, Georgia? That one represents fresh water in all the lakes and rivers on the planet. Most of the water people and life on earth need every day comes from these surface-water sources. The volume of this sphere is about 22,339 mi3 (93,113 km3). The diameter of this sphere is about 34.9 miles (56.2 kilometers). Yes, Lake Michigan looks way bigger than this sphere, but you have to try to imagine a bubble almost 35 miles high—whereas the average depth of Lake Michigan is less than 300 feet (91 meters).

Water is on and in the Earth

The vast majority of water on the Earth’s surface, over 96 percent, is saline water in the oceans. The freshwater resources, such as water falling from the skies and moving into streams, rivers, lakes, and groundwater, provide people with the water they need every day 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 do you account for the flow in rivers after weeks without rain? In fact, how do you account for the water flowing down a 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.

• August 29, 2017
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