Coral Reef

Imagine you are snorkeling in the warm ocean water around a tropical coral reef. You put on your mask and swim fins. You float around looking at the reef below you. The coral reef looks like strangely shaped rocks sticking up from the ocean floor. Crooked coral that looks like tree limbs twists up from cracks and caves in the reef. A big piece of coral that looks like a brain lies on the bottom. Orange and pink coral shaped like fans wave in the currents. Fish of all different shades and varieties of color swim near the reef.
Coral reefs play an important role in ocean life. Many kinds of plants, fish, and other animals live on and around a coral reef. Even the reef itself is made mostly of tiny coral animals, both living and dead.

RUNOFF: MOVING AROUND ON LAND

Water that falls on land always flows from high places to lower ones. This flow is called runoff. Precipitation that falls on land runs downhill. The water cuts channels as it flows.
Some water seeps into the ground. It fills cracks between rocks. Underground water also flows from places that are full to places that have less water.
Water from land flows into streams. Streams flow down mountains. Streams join together to make rivers and eventually the water flows into storage in the ocean. Then the water cycle starts all over again.

PRECIPITATION: BACK TO EARTH

Water returns to Earth as precipitation—rain, snow, or other moisture. Precipitation requires ice or liquid water. Water vapor can change into tiny ice crystals or drops of water when the air gets cold enough. Clouds are collections of tiny ice crystals or water droplets.
When the ice crystals or drops of water in a cloud get heavy enough, they fall to Earth as precipitation. Rain, snow, sleet, and hail are all forms of precipitation. Most precipitation falls into the oceans and goes right back into storage.

EVAPORATION: INTO THE AIR

Water goes from storage into the atmosphere (the air that surrounds Earth) by a process called evaporation. When water evaporates, it changes from a liquid into an invisible gas. The gas is called water vapor. Water vapor goes up into the atmosphere.
Most of the water that gets into the air evaporates from the surface of the oceans. Water also evaporates from rivers and lakes. Water can also go from ice caps and icebergs into the air. Ice changing into water vapor is called sublimation.

IN STORAGE

The water cycle has four stages: storage, evaporation, precipitation, and runoff. Most of the water on Earth is in the first stage, storage. Water on Earth gets stored in oceans, lakes, rivers, ice, and even underground. The oceans store the majority of this water.

Water Cycle

Maybe you recycle cans, glass, and paper. Did you know that nature recycles, too? One of the things nature recycles is water. Water goes from the ocean, lakes, and rivers into the air. Water falls from the air as rain or snow. Rain or snow eventually find their way back to the ocean. Nature’s recycling program for water is called the water cycle.

COULD WE RUN OUT OF WATER?

Nature recycles water all the time. Water in oceans, lakes, and rivers evaporates, or turns into a gas and rises into the air. The water vapor eventually turns back into a liquid and falls as rain. The water cycle keeps the total amount of water on Earth the same. But most of this water is salt water in the ocean. People need fresh water for drinking and for growing food on farms. Ocean water is too salty to drink. It is too salty to use for watering plants. Some places have more fresh water than others. People who live near big lakes or rivers have more fresh water than people who live in the desert. Places where a lot of rain falls have more fresh water. Places that usually have enough fresh water sometimes have a drought. Very little rain falls during a drought. People run short of water. People everywhere should be careful not to waste water.