All of the water that is on the earth has always been here. Earth never gets water added to it--nor does water disappear from the earth. Water is constantly recycled in a process known as the hydrologic or water cycle.
Fresh water is more scarce than you might think. 97% of all the water on the earth is in the oceans, and so only 3% is fresh water. About 2.4% of the water on earth is permanently frozen in glaciers and at the polar ice caps. About 1/2 of 1% of the water on earth is groundwater. Only about 1/100 of 1% of the water on earth is in the rivers and lakes. Water is essential to life on earth, so it is important that we protect our water resources.
Nature has a way of keeping the amount of water on the earth relatively constant. A large amount of water evaporates from the surfaces of oceans, rivers, and lakes every day. It forms water vapor that rises into the air until it cools, condenses, and forms water droplets. Millions of these droplets come together to form clouds. When clouds get heavy enough, gravity tugs on the droplets, and the clouds release their water as rain or snow. This precipitation falls into streams and rivers, which flow back to the oceans, seas, and lakes, where the water cycle can begin again.
Sample some of the following activities to learn more about the water cycle.
The following are places to go (some real and some virtual) to find out about the water cycle.
Pay a visit to your nearest aquifer. Aquifers are underground areas where water flows through sand, gravel, or clay. Aquifers are also called groundwater areas. They are sources of fresh water. There are places in the world where users are depleting aquifers and not giving them enough time to replenish themselves as a natural part of the water cycle. When aquifers don ’t have sufficient time to collect more water, the water table drops, and the aqu ifer can be lost forever.
Finally, visit the Dead Sea on the borders of Israel and Jordan. It is also a terminal body of water, and it is even saltier than the Great Salt Lake. The Dead Sea is really a lake—not a sea.
Watersheds are the land areas that catch rain or snow and then drain to specific marshes, streams, river, lakes, or to ground water. Visit the watersheds of Utah. You can actually put in your zip code and find out the watersheds near your school or home.
Visit the Great Salt Lake and watch the water cycle at work. The Great Salt Lake is a terminal lake which means that no rivers flow out of it. Dissolved salt from soil and rocks is deposited in the lake from its tributary rivers. Since no water flows out of the lake, over time, the salt content has become highly concentrated. Because the lake is very large and fairly shallow, it has a greater surface-area-to-volume ratio of water than most lakes which results in high amounts of evaporation.
Visit your school or public library and check out King Bidgood's in the Bathtub by Audrey Wood. It's about a ruler who won't leave the bathtub and attend to his duties. Brainstorm some ways to get King Bidgood out of the tub.
While you’re at it, visit ancient Lake Bonneville. At 325 long and 135 miles wide, it covered about one-third of present-day Utah. The Great Salt Lake is a remnant of this once great lake.
Visit worldwide oceans and discover that 80% of the water vapor in the air comes from the oceans.
Virtually visit ice crystals to learn about some of their interesting characteristics. Rainbows form because raindrops bend the light of the sun which separates the light into its seven bands of color. Ice crystals can also bend the rays of the sun which, instead of creating rainbows, creates large, bright spots called sundogs. When ice crystals fall through the atmosphere at night and bend the moon’s light, these spots are called moondogs.
Travel to the troposphere and look at clouds.
Precipitation---it’s an important part of the water cycle. Visit the rainiest place on earth, which according to the Guinness Book of World Records is Tutunendo, Colombia. It has an average rainfall of 463.4 inches per year. (Compare this to Salt Lake City, Utah which has annual average rainfall of 16 inches in populated areas and 30 inches per year in the mountains.)
Travel with groundwater through the entire course of the water cycle.
Pay a visit to the largest glaciers on each continent. They play an important role in the water cycle of the earth. In North America, the largest glacier is Hubbard Glacier in Alaska. Most of the fresh water on earth, about 68.7%, is held in ice caps and glaciers.
Travel to different areas on earth to see the water cycle in action. Sometimes it’s fast and sometimes it’s slow. In hot deserts, rainwater never flows into rivers which flow into the ocean where the rainwater eventually evaporates and becomes clouds and forms rain again; it evaporates immediately when it hits the ground. In extreme northern and southern parts of the earth, water falls as snow and is compressed into glacial ice. This water may be locked up in a glacier for thousands of years before it rejoins the water cycle.
Spend time with scientists and environmentalist who are trying to solve the problem of acid rain. When chemicals from factories and automobiles react with water vapor in the air, it can form acid rain. Acid rain harms forests and other vegetation, pollutes water, and it can even pit and erode buildings and statues.
Talk with airplane pilots and ask them about the white trails that we sometimes see behind airplanes high in the sky and how they relate to the water cycle. These white trails are called contrails which is short for condensation trails. They are formed when the water vapor from the hot exhaust of an airplane meets cold air at high altitudes and condenses to form cloud droplets.
Send your questions about the water cycle to Ask-a-Hydrologist.
Visit with the people who live near the Bay of Fundy in Canada. This v-shaped bay is between the provinces of New Brunswick and Nova Scotia. The Bay of Fundy has one of the highest and most dramatic tide cycles in the world. The tide enters the bay at its widest section and is then channeled into the increasingly narrower and shallower part of the bay, causing a huge tidal wall of water each day.
Talk to the folks at the EPA. They are experts on global warming. Global warming is an increase in the surface temperature of the earth. This increase in temperature affects the water cycle because the evaporation and condensation are temperature-dependent.
Chat with Daniel Fahrenheit and Anders Celsius and William Thomson Kelvin and find out about their systems for recording the boiling and freezing points of water. At 32 Fahrenheit and 0 Celsius, water changes its state to ice. At 212 Fahrenheit and 100 Celsius, water changes its state to vapor.
Learn about groundwater.
Talk to Drippy the Raindrop. He knows all about the water cycle.
Spend some time with Poseidon who was the Greek god of the sea and Neptune who was his Roman counterpart. The early Greeks and Romans believed that the fresh water that they needed for their crops and their daily lives was controlled by these two gods. They made offerings to Poseidon and Neptune to protect themselves from drought and assure plentiful rainfall.
The artistic representation of raindrop as presented by popular culture is that of a teardrop. Actually, real raindrops bear scant resemblance to this popular fantasy (except after they have ceased to be raindrops by splattering on a window, say). Find out the real shape of raindrops.
The hydrologic cycle recycles the earth's valuable water supply. Learn about evaporation, condensation, precipitation, run-off, infiltration, and transpiration.
Even the ocean can have freshwater springs, and at these springs, fresh water can be taken right off the surface of the sea. When rainwater seeps into the ground, it enters the aquifer which is the porous layer of earth that holds groundwater and is the source of water for man-made wells.
Learn about the earth's magnetic field and how it protects our water resources.
Figure out the part of the water cycle in which snowflakes are formed. Did you realize that a tiny particle, such as a speck of dust, smoke, or salt, is at the center of every snowflake?
All about water - the U.S. Geological Survey's Water Science School information site.
Learn how to make your own mini water cycle in your classroom.
Check out this comprehensive digital library about water in the western United States. You will be swimming in information!
- Branley, Franklyn Mansfield. Down Comes the Rain. New York: HarperCollinsPublishers, c1997.
- Burton, Jane. The Nature and Science of Rain. Milwaukee: G. Stevens, 1997.
- Morgan, Sally. Water. New York, NY: Facts on File, c1994.
- Owen, Andy. Rain. Des Plaines, Ill.: Heinemann Library, 1999.
- Patten, J. M. Liquid To Gas and Back. Vero Beach, FL.: Rourke Book Co., 1995.
- Saunders-Smith, Gail. Rain. Mankato, Mn.: Pebble Books, 1998.
- Wick, Walter. A Drop of Water. A Book of Science and Wonder. New York : Scholastic, c1997.
- Williams, Brenda. Water. Austin, Tex.: Raintree Steck-Vaughn, c1999