Nature Nugget – The Water Cycle

There are an estimated 326 million trillion gallons of water on the Earth. The Earth is covered with 70 percent water, 98 percent of which is salty. Only a small portion of the Earth’s water is fresh, and 1.6 percent of that is locked up in the polar ice caps and glaciers. Another 0.36 percent of the water is found underground in aquifers and wells. Only about 0.036 percent of the planet’s total freshwater supply is found in lakes, rivers, and streams. The rest of the planet’s freshwater is floating in the air as clouds and water vapor, locked up in the tissues of plants and animals, and sitting on shelves in stores as bottled water and other beverages.

The Earth’s water is always in circulation in a rapid recycling process called the water cycle. This cycle describes the continuous movement of water on, above, and below the surface of the Earth. In the cycle, water can change from liquid, vapor, or ice at various periods. The process starts when the Sun’s heat warms the Earth’s surface waters causing the evaporation of water molecules into the air, changing the water from a liquid to a gas. The rate of evaporation is determined by temperature, humidity, and wind. The oceans supply about 80 percent of the evaporated water that goes into the atmosphere.

Another important source of water entering the atmosphere is through a process called transpiration. Transpiration is the process by which plants release water into the air. The most important sources of transpiration are the great forests of the world, especially the rain forests of the tropics. Transpiration accounts for 10 percent of all evaporating water going into the atmosphere.

As the water evaporates into the atmosphere, it cools and forms clouds. The clouds are groups of tiny water droplets or ice crystals and can come in all shapes and sizes. Water can be carried great distances as clouds, with the help of winds. When conditions are right, the water returns to the Earth in the form of precipitation as either rain, snow, hail, sleet, or freezing rain. After the water returns to the surface of the Earth, it flows into rivers and streams which take it back to the oceans, or it soaks into the ground to water plants and renew underground aquifers. Then the process starts over again. Individual water molecules in an apple you ate yesterday may have fallen as rain halfway around the world last year or may have been frozen in a glacier a thousand years ago.

Without water, life would not exist. Jesus says that He is the source of living water: “If any man thirst, let him come unto me, and drink. He that believeth on me, as the scripture hath said, out of his belly shall flow rivers of living water.” John 7:37, 38.

“The cry of Christ to the thirsty soul is still going forth, and it appeals to us with even greater power than to those who heard it in the temple on the last day of the feast. The fountain is open for all. The weary and exhausted ones are offered the refreshing draught of eternal life. Jesus is still crying, ‘If any man thirst, let him come unto me, and drink.’ [John 7:37, last part]. ‘Let him that is athirst come. And whosoever will, let him take the water of life freely’ (Revelation 22:17). ‘Whosoever drinketh of the water that I shall give him shall never thirst; but the water that I shall give him shall be in him a well of water springing up into everlasting life’ (John 4:14).” The Desire of Ages, 454.

David Arbour writes from his home in De Queen, Arkansas. He may be contacted by e-mail at: