The planet Earth is unique in the solar system because of its abundance of water. It is one of the reasons that this planet can support life while others cannot. Where does the water come from? Where does it go? What's the story of water?

Water, Water, Everywhere

Water covers 70 percent of the Earth's surface, but 97 percent of it is salt water in oceans and seas. People cannot drink salt water, so even though it seems as if there is an unending supply of water to support human life, only 3 percent of the water on Earth is the fresh water that can actually help people survive. More than two-thirds of the fresh water is frozen at the North and South Poles, which means that the 6 billion people who share this planet have to share less than 1 percent of the water on it.

Create a visual picture of just how little 1 percent is. You can draw a pie chart and color it to look like the Earth. You could use a chart of ten squares by ten squares or a jar with 100 marbles or dry beans. For each method, start with the whole and ask the students how you would go about showing 1 percent. When all of the methods correctly show 1 percent, return to the water discussion. Look at the globe and how much water is covering it. Look at your diagrams and demonstrations that show how much water covers the planet. Then look at how tiny the 1 percent is compared to the 99 percent. It's not very much, is it? That's why people have to take care of the fresh water and make sure it's not polluted or wasted.

Water Cycle

Water is the only substance that can be found in three forms: a liquid (water), a solid (ice), and a vapor (clouds or steam). Water is usually in its liquid form. It turns into a solid when the temperature drops below freezing — 32°F or 0°C. Water becomes a vapor when it is heated and escapes into the air. Water constantly cycles among these three forms.

The water cycle involves three stages: evaporation, condensation, and precipitation. Every day, sunlight warms the water in oceans, rivers, lakes, and streams. Once the water warms to a certain point, it vaporizes and floats up in the air. This is called evaporation. The gaseous water molecules float higher and higher, and the air gets cooler and cooler. Once the air gets cool enough, the water vapors turns back into liquid droplets. This is called condensation, and that's how clouds are made. More and more droplets float up into the cloud until it becomes too heavy to float anymore. Then it rains, which is also known as precipitation.

Have the children sing a fun song about the water cycle. You can make up your own or use the following song written by Lori Ann Phelan:

Water Travels in a Cycle

(Sing to the tune of “She'll Be Coming Around the Mountain”)

Water travels in a cycle, yes it does (use pointer finger to make a big circle)

Water travels in a cycle, yes it does (repeat finger circle)

It goes up as evaporation (moves hands up to the sky)

Forms clouds as condensation (make a cloud overhead with arms)

Then comes down as precipitation, yes it does! (sprinkle with fingers while bringing arms down in front of you)

Muckin' Up the Water

Have you ever been to a place where the water wasn't clean? Where was it? What did you see? Maybe that was garbage floating along a shoreline or oil in water. These are examples of water pollution, but you can't always see it when water is polluted. Most of the pollution mixes into the water invisibly. Where does it come from? Find pictures to illustrate this to your class to emphasize the message.

Farms that don't use sustainable practices are one source of water pollution. If chemicals are sprayed on the plants, rain can cause the chemicals to soak through the ground and into the groundwater. If it rains so hard that the soil can't soak it up fast enough, the water runs off and carries the chemicals with it to the nearest water body. If a farm uses sludge as a fertilizer, the runoff can include manure that can contaminate nearby water sources.

Factories are another source of water pollution. They often have large pipes that lead from the factory to a nearby water source. The factory uses water to make a product, and when they're done with it, it flows down the pipe and out into the water, carrying the toxic leftovers with it. Sometimes the water that enters into the lakes, rivers, and wetlands is too warm for the plants and animals that live there.

Another source of water pollution is from people's garbage and sewage. Cities have water treatment facilities, and they collect a lot of the pollutants from the water — but not all of it. Certain pollutants such as antibacterial soaps pass through the treatment process. The water that is discharged into a local stream or river still has some pollutants in it, and this makes an unhealthy habitat for the plants and animals that live in the water.

One way that people's garbage ends up in water is from storm drains. Storm drains prevent streets from flooding when it rains. Just like a drain in a sink, they let the water drain away from the street and take the rainwater to a local body of water. The problem is that anything in the street gets washed away with the rainwater. That can mean litter, pet waste, pesticides, salt, oil and gasoline from cars, and anything else people leave in the streets.