PDF A Diagram of the Water Cycle - Richmond Public Schools

3.9 A-C Earth Patterns, Cycles and Change: The Water Cycle The sun is the source of energy that propels the water cycle. It's heat causes the surface evaporation that begins the cycle illustrated below.

A Diagram of the Water Cycle

Condensation

Evaporation

Precipitation

Water

The water cycle begins with the sun and wind causing water to evaporate. The water is carried high above the earth's surface on rising currents of air. As the water vapor reaches the cooler air of the sky, it condenses into tiny drops or ice crystals. Eventually thses become large enough that their weight pulls them back to earth in some form of precipitation. The precipitation collects in bodies of water and the cycle begins again.

Sources of Water

? Rivers ? Lakes ? Wells ? Underground water pockets or lakes ? Reservoirs ? usually lakes where water is held for use. ? The ocean ? water from the ocean must be desalinated (unsalted) before it can be

used for drinking or irrigation.

Methods of Conservation

? Installation of faucets and toilets that use smaller amounts of water. ? New irrigation methods that use less water for farming. ? Limited watering of lawns, limited washing of cars. ? Behavior changes ? We can do lots of small things to conserve water ? turn off

the faucet while brushing teeth or washing hands, take shorter showers, use a dish washer, etc. Water Pollution: How does it happen and why is it a problem for us? Every day, poisonous material make their way into our water resources. Here are some examples:

? Heavy rains wash oil, fertilizers, pesticides and waste products from the land into our lakes and rivers.

? Factories allow waste materials to drain into waterways. ? Ships dump waste material and garbage into the sea. ? Landfill waste drains though the soil and into ground water resources.

Now this pollution has a big effect on us. First of all we can't survive without fresh clean water. Our bodies need about a gallon of water a day or we become dehydrated and die. We also need water for irrigation so that we have food to eat. Finally, we depend on life in the lakes, rivers and oceans - on the animals that provide us with food and on the plants that create oxygen in our atmosphere for us to breathe. The bottom line is, we need to keep our water resources as clean as possible for our own health and that of the living things that share our planet.

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