Note: Teachers notes are in red
This activity will give students a visual indication of the percentage of Earths water that is needed for survival by humans and other animals, as well as by plants. Students will learn the importance of conserving fresh water as well as keeping it clean.
Be a Hydro-Hero!
Everyone everywhere must have fresh water. But does everyone everywhere have enough water? And is that water clean? The world is full of living things that depend on waterhumans and hippos, hawks and hydrangeas, to name but a few. So the planet needs hydro-heroes (hydro means water) to make sure all people and other living things have clean, fresh water for a long, long time!
Subjects: Geography, Science
Relevant U.S. National Geography Standards: 3, 7, 8, 14, 18
Inflatable or soft globe
The class will divide into groups of three or four students. Each group will need the following:
Blue food coloring
Container with about 3 cups (0.7 liters) of water
3 large, clear plastic cups (20 fluid ounces [0.6 liters] or larger)
Markers to label cups
Teaspoon (or other measuring spoon)
Here are the definitions for the three categories of water used in this activity. Depending on students age, explain as much or as little of this information as appropriate.
All the Water in the World: 100 percent of the worlds water, of which slightly more than 97 percent is salt water (oceans, seas) and slightly less than 3 percent is fresh water (polar ice caps, groundwater, rivers, lakes, wetlands, etc.)
All the Fresh Water in the World: Slightly less than 3 percent of the worlds water, of which 77 percent is polar ice; 22 percent is groundwater; and one percent is rivers, lakes, wetlands, etc.
Fresh Water People Can Use: Only 23 percent of worlds fresh water can be used for drinking water, of which roughly 22 percent is groundwater and less than one percent is rivers, lakes, wetlands, etc. Less than half of one percent of the worlds water is available for people to use.
The Blue Planet: Water, Water Everywhere
To demonstrate the amount of water on the Earths surface, hold up an inflatable globe and turn it around several times. Ask: What percentage of Earth is water? Write students responses on the board.
Earth is called the watery planet. If you were an astronaut looking down at Earth from space, our planet would look mostly blue. Everywhere you look theres water! It cleans sidewalks, overflows in fountains, glints in swimming pools, and gushes from taps and showerheads. It seems as though water is the most plentiful and least valuable resource around. From Earths outward appearance, it seems that everyone everywhere should have as much water as they need.
To help you catch on to how much of the Earth is water, your teacher is going to toss a lightweight globe to you and see how many times your index finger lands on water.
Toss an inflatable globe about 20 or so times to students. When students catch the ball, ask them to say what their right-hand index finger is touchingwater or land. Calculate the percentage of times students fingers land on water. Write that number on the board.
What percentage of Earths surface did students originally think was water?
Were students surprised that so much of Earths surface is covered with water?
Should people worry about having enough fresh water to drink when so much water covers Earth?
Can people use all of Earths water for drinking water?
All the Water in the World
This exercise will help students see how much of the worlds water is available for human use. Lead a discussion with students on the many ways in which they and others use water, such as bathing, cooking, washing dishes and clothes, watering lawns and gardens, washing cars, manufacturing goods, growing food crops, fighting fires, cleaning streets, pumping away wastes, operating sewage-treatment equipment that helps purify waste, etc.
Divide students into groups of three or four. Give each group a container with at least 3 cups (0.7 liters) of water in it, three clear plastic containers, one measuring spoon, and a sheet of paper.
In step 1, tell each group to put 100 teaspoons (0.49 liters) of water into Cup 1. Ask, Where are some of the places where you would find water? Tell each group to write down its response on the sheet of paper. Ask, How many teaspoons (liters) of the water in Cup 1 do you think represent salt water, and how many teaspoons (liters) represent fresh water? Tell each group to write down its response.
Much of the Earth is water, but theres a catch. People need a certain kind of water for drinking and other basic activities, such as cooking, washing dishes, brushing their teeth, and flushing toilets.
Youre going to work in a group to learn how much of Earths water is available for people to use. Your teacher will give your group a container of water, a teaspoon or other measuring device, and three cups.
Cup 1 will represent All the Water in the World.
Cup 2 will represent All the Fresh Water in the World.
Cup 3 will represent Fresh Water People Can Use.
Step 1: Taking turns within your group, spoon 100 teaspoons (0.49 liters) of water from the big container into Cup 1. Cup 1 now represents All the Water in the World. Where in the world could you find that water? As a group, write down your answer. Some of that water is salt water. Some is fresh water. Can you fathom how much water is salty and how much is fresh? As a group, write down your answer.
All the Fresh Water in the World
In step 2, tell each group to remove 3 teaspoons (15 milliliters) of water from Cup 1 and put it into Cup 2.
Tell students that Cup 1 now represents all the salt water in the world. More than 97 percent of the worlds water is salty ocean water. Salt water is too expensive and difficult to process for human use. Were surrounded by salt water, but for the most part we cant use it.
Cup 2 represents 100 percent of the worlds fresh water. Less than 3 percent of the worlds water is fresh water. Tell each group to write down its response to the small amount of fresh water.
Step 2: Remove 3 teaspoons (15 milliliters) of water from Cup 1 and put it into Cup 2. The water in one of the cups represents the amount of the kind of water you cant drink and the water in the other cup represents the kind you can. Notice much of a difference between the two cups? When you find out which cup represents the water suitable for drinking, write down your response as a group.
All the Water in the World That People Can Use
Explain that people cant even use all of the worlds fresh waterthe water in Cup 2. Then tell students you would like them to show how much fresh water people can use and how much they cant. Ask: How could you divide the tiny bit of water in Cup 2 to show this amount accurately? Since that would be nearly impossible, suggest to students that they change the ratio of water in the cups. For step 3, have each group pour the water in Cup 1 into Cup 2. (Cup 2 should now hold 100 teaspoons [0.49 liters].) Explain that Cup 2 still represents all of the worlds fresh water. To visually reinforce this change, place one or two drops of blue food coloring in each Cup 2.
Hold up Cup 2. Explain that 77 percent of all fresh water is in polar ice sheets. Its impossible to use until this ice melts. Only 23 percent of the water in Cup 2 is available for human use. Remind students how proportionately small the amount of fresh water was to the amount of the worlds total water.
Theres not much of the kind of water people need, is there? And we cant even use all of this small amount of water. (Much of it is hidden or frozen.) How much of the worlds water does your group think people can use? Write down your answer as a group.
Step 3: Pour all the water in Cup 1 into Cup 2. Cup 2 still represents all the worlds fresh water, but the ratio of water has changed. Add some blue food coloring to Cup 2 to help you remember that it represents fresh water.
For Step 4, have each group spoon 23 teaspoons (113 milliliters) of water from Cup 2 into Cup 3. Tell students that the amount of water in Cup 3 represents all the water people can use. Again, remind students how proportionately small the total amount of fresh water is to all the worlds water. Have each group write down its response to that small amount.
Ask: How much of Cup 3Fresh Water People Can Usedo you think is found in lakes and rivers? Have the group write its response on paper.
Hold up Cups 2 and 3. Remind students that the blue water represents 100 percent of the worlds fresh water and that people cant use 77 percent of the fresh water because its in polar ice sheets and glaciers (Cup 2). People can use only 23 percent of the worlds fresh water (Cup 3). Tell students that nearly all the fresh water people can use is groundwater. Groundwater is so deep in the ground that its difficult and expensive to access.
Hold up Cup 3. Tell students that only 1 teaspoon (5 milliliters) in Cup 3 represents the proportion of rivers, lakes, and wetlands in the worldless than half of one percent of all the water in the world!
Step 4: In your group, take turns spooning 23 teaspoons (113 milliliters) out of Cup 2 and putting them into Cup 3. One of the cups represents fresh water that people cant use. One cup represents fresh water people can use. When your groups finds out which cup is which, write down your response.
People can use the water in lakes and rivers. Theres also water underground called groundwater. What proportion of the water that people can use does your group think is in rivers and lakes, and what proportion is in groundwater? As a group, write down your answer.
Do you think the saying What you see is what you get! works for fresh water? How about the expression out of sight!? As a group, write down your answer. Choose someone from your group to tell the class your groups thoughts during this activity.
Ask each group to select a spokesperson. Have that student present the groups reactions to the activity to the class.
Wanted: Clean Fresh Water
The United States has a lot of cheap, clean fresh water. Thats not the case in much of the world, however. In countries where clean, fresh water is scarce, it is highly valued and used sparingly. As global demand for water increases, water reserves for human use are shrinking, making conservation of fresh water one of the most important challenges we face as we enter the 21st century. Pollution is another problem that threatens fresh water.
Assign activities, either online or offline, to reinforce the importance of these threats to fresh water. In addition to the suggestions below, you can find dozens of activities suitable for a range of ages in the sites listed in Other Related Web Sites.
If students have access to a computer, challenge them to identify people who are wasting and polluting water at Whats Wrong With This Picture? at the Environmental Protection Agency site (http://www.epa.gov/kids/whatswrong.htm).
If students dont have access to a computer, you can print out activities, games, puzzles, diagrams, and information from:
Wading Pool for Kids at the Center for Marine Conservation site (http://www.cmc-ocean.org/wading/wading.php3); click on Splash Class.
Kids Water Zone at the New Jersey American Water Works Association site (http://www.njawwa.org/kidsweb/Default.htm).
Water is a limited and precious resource. In North America, people use more of it per person than anywhere else in the world. In some countries, clean, fresh water is scarce. Some people have to walk for hours every day just to get a few gallons of water for basic necessities!
With only a limited amount of water available, its important to keep fresh water clean. The pollution of fresh water can result from fertilizers, pesticides, litter (debris), oil, detergents, soot, animal wastes, sand, salt, and chemicals. Polluted water isnt safe to drink, and its expensive to restore it to cleanliness.
Join the Hydro-Heroes!
You dont need to fly or wear a cape to be a Hydro-Hero! You can be a hero to water just by doing ordinary things, like using less water when you wash the dishes and not throwing trash into storm drains. To keep the planet healthy for the future, we need to keep water as clean as possible. We should do our best to make sure everyone everywhere has enough fresh water. Here are a few things you can do:
Plan a water conservation day at home with your family. Talk with your family about different ways all of you could conserve water. Write these ideas down and practice them for a week. After a week, have a family meeting. Do you think you were successful? Then try to make your new water conservation practices a habit!
Get water-saving tips from Buster Backflow and Mr. Leakey at the Sacramento Area Water Works Association (http://www.sawwa.org/kidsspot.htm).
Find more water conservation tips at the American Water Works Association (http://www.awwa.org/dww/SAVE.htm).
Join the Global Water Sampling Project. Work with other students online at their Web site to test fresh water around the globe (http://k12science.org/curriculum/waterproj/)!
Go to Blue Mountain Greeting Cards (http://www.bluemountain.com/eng/earth/) and send an Earth Friendly greeting card to encourage water conservation!
Partially adapted from an activity by Jeff Cenoz, teacher-consultant, and Learning with Otis from the Missouri Department of Conservation in Jefferson City, Missouri. Also adapted from the 1993 Geography Awareness Week teachers handbook. Copyright © 1993 National Geographic Society.
© 2000 National Geographic Society. All rights reserved.