The earth has a tremendous amount of water , but almost all of it is in the oceans. The oceans cover about 70 percent of the earth’s surface . They contain about 97 percent of all the water on earth , and are the source of most precipitation that falls to earth . Ocean water is too salty to be used for drinking , agriculture , or industry . But the salt is left behind during evaporation , and the precipitation that falls to earth is unsalty water . Only about 3 percent of the water on earth is fresh water and most of it is not easily available to man . It includes water locked in glaciers and ice-caps, more than 2 percent of the earth’s surface . About half of 1 percent of the earth’s water is beneath the earth’s surface . Rivers and lakes contain only about one-fiftieth of 1 percent of the earth’s water .
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