Observe effects of noticeable change over time in the following way: after a rain, trace the water path down a road, street, hillside, or around an obstacle such as a large rock or tree. Explain to students that the rainfall goes into the storm drain and is carried out to neighborhood creeks, lakes and rivers. (4.10)
Explore This! Schoolyard Rain Sleuths
Let your students ponder puddles, and uncover what happens to rainwater in and around your schoolyard!
1. When rain is forecast, have the class bring in rain gear and tell them they’ll have a chance to explore water in action. Take them on a walk in the schoolyard and pose this challenge question: What happens to rainwater when it falls on and around our school? Let the group explore a variety of areas: under roofs and near downspouts, parking lots, hard footpaths, playground, walkways, ditches, storm drains, and so on.
Discuss these types of questions: Where do you find the most rainwater? Is it moving or standing still? Do you notice anything being carried with the water? Where do you think it ends up? Collect some runoff in a clear jar to take back to the classroom. Challenge students to keep their eyes peeled for flowing water on roads and other surfaces in their communities.
2. Back in class, discuss students' observations and questions and compare the rainwater runoff in the jar with tap water in another jar. Ask, What differences do you observe?
Ask students to write down what kinds of things rainwater might pick up as it hits roads, roofs, driveways, and other surfaces. Explain that many of these pollutants are invisible. To spark their thinking, share one or two examples (e.g., motor oil, gas, insecticides, laundry detergent, paint, pet waste, cigarette butts). Have them put a check by things they use in their own homes. If students haven’t fleshed out this idea, explain that water that runs off hard surfaces eventually runs into storm drains, streams, rivers, lakes, and oceans. Generate interest in the next topic by explaining that soils and plants have amazing powers to clean up nasty water by simply doing what they do naturally!
Explore This! All But the Last Drop
In most parts of the U.S., kids don’t give water a second thought. But conduct this visual lesson, and they just might tune in!
1. Before launching the activity, ask students to brainstorm all the ways they use water in their lives (for example, for playing, cleaning, drinking, watering the lawn, cooking, washing cars, flushing toilets). Next, ask, Besides personal uses, how else do we use water in this country? If they don’t touch on farming or industry, tell them that it takes about 600 gallons of water to make just one quarter-pound hamburger!
2. Invite the class to explore how much water we have to work with. Fill a wide gallon container (e.g., ice cream bucket) with water and ask them to imagine it contains all the water on earth. Invite a student to put in a few drops of blue food coloring. Launch a discussion by asking, How much of this water do you think is available for people to use?
3. Tell students the next task is to transfer the portion that is fresh water to the clear bowl. (This is in lakes, rivers, groundwater, ice, and living things.) What remains in the bucket will represent salty ocean water, which we can’t use. If you have a globe or world map, have youngsters compare the space taken up by land, oceans, and fresh water bodies. Next ask them how much water they think should be transferred to the bowl. Ask, How did you arrive at your answers?
4. Ask a volunteer to transfer just half a cup of water from the gallon container to the bowl; this represents all the fresh water on earth. Calculate how much salt water is left in the bucket (15 ½ cups). Older students can figure out the percentage of fresh water (less than 3% of all the water on earth). Ask, How does this compare with your suggestions?
5. Explain that the final task is to transfer water from the small bowl to a plate to represent the portion of fresh water that humans can actually use. (The rest of the water in the half-cup is deep in the ground, bound up in soil, or in the atmosphere.) Launch a discussion of how much water should get moved to the plate and list students’ ideas on the board. Have one student use the eyedropper to place just one drop of water from the half-cup onto the plate. Ask, How did this compare with your ideas? Did anything surprise you? What can you conclude from this exercise about water? What questions do you have?