The amount of water on Earth hasn’t changed since the planet was formed two billion years ago.
Approximately 97% of the water on Earth is salt water. Only 3% is fresh water. Of that remaining 3%, most is frozen in the polar caps of the Arctic and Antarctica. The remaining 1% is found in lakes, reservoirs, rivers, streams, and beneath the ground.
Water moves around the Earth in a water cycle. In one century, the average water molecule spends 98 years in the ocean, 20 months as ice, about two weeks in lakes and rivers, and less than a week in the atmosphere. Much of the Earth’s water remains locked in glaciers and polar ice for thousands of years.
