WaterLittle of Earth’s water is usable in everyday life

Published 9 May 2012

Very little of Earth’s water is usable in everyday life; about 96 percent of water on Earth is saline; of the total freshwater, over 68 percent is locked up in ice and glaciers; another 30 percent of freshwater is in the ground; rivers are the source of most of the fresh surface water people use, but they only constitute about 300 mi3 (1,250 km3), about 1/10,000th of one percent of total water

How much water exists on, in, and above Earth?

About 70 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 earth aquifers.

The U.S. Geological Survey says that 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 the planet’s water supply is constantly moving from one place to another and from one form to another.

The vast majority of water on the Earth’s surface, over 96 percent, is saline water in the oceans. It is, however, 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 to live. Water sitting on the surface of the Earth is easy to visualize, but, the unseen water below our feet is also critically important to life.

Even though we 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 we 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.

Humans should be happy this happens because people make use of both kinds of water. In the United States in 2000, people used about 323 billion gallons per day of surface water and about 84.5 billion gallons per day of groundwater. Although surface water is used more to supply drinking water and to irrigate crops, ground water is vital in that it not only helps to keep rivers and lakes full, it also provides water for people in places where visible water is scarce, such as in the desert towns of the western United States. Without groundwater, people would be sand-surfing in Palm Springs, California. instead of playing golf.

Here are some numbers about the volume of water on Earth:

  • If all of Earth’s water (oceans, icecaps and glaciers, lakes, rivers, ground water, and water in the atmosphere) were 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). 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 one inch of water.
  • The forty-eight 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 were poured on the United States, it would cover the land to a depth of ninety 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. If we really want to find freshwater, however, 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.

Where is Earth’s water located?
The world’s total water supply of about 333 million mi3 of water, over 96 percent is saline. Of the total freshwater, over 68 percent is locked up in ice and glaciers. Another 30 percent of freshwater is in the ground. Rivers are the source of most of the fresh surface water people use, but they only constitute about 300 mi3 (1,250 km3), about 1/10,000th of one percent of total water.