THE IMPORTANCE OF WATER CYCLE

THE IMPORTANCE OF WATER CYCLE

Introduction

The water part of the earth is called hydrosphere or “water sphere”. This covers three-fourths of its surface. Therefore, water covers a larger area of its surface than land. That is why the earth is called “the blue planet”. Water gives the earth its characteristics of blue color as seen from outer space. Water continuously moved in the earth’s surface in a process called “Water Cycle”.

Although there is a continuous cycle of water, you might wonder if there will come a time when we will run out of water. Do you know that 97% of the water found in our surrounding is salty? Thus, only 3% of this water is fresh or potable. This very small amount of fresh water is 67% locked in the form of ice mainly found in Greenland and Antarctic. Therefore, only about 1% of freshwater is found in rivers, lakes, ponds, and in the atmosphere in the form of water vapor.

The Process of Water Cycle

Water may exist in different states namely solid, liquid and gas. Water changes from one state to another state depending on certain conditions. Water absorbed heat, so water level decreases because water evaporates. This process called evaporation. This change from liquid water to water vapor is due to the water absorption. The absorption of heat by water particles make the surrounding cool. As the surrounding air becomes cool and saturated, the air gives off all the water vapor it could no longer hold. The released water vapor turns to water droplets or mist which cools surfaces like rocks, glass, or leaves of plants. The changing of water vapor to water droplets is called condensation.

Water vapor in the air rises to the upper atmosphere. It condenses and forms a cloud. When clouds become too heavy with water vapor the air can no longer support their weight and let go of the water droplets and fall back to the earth surface as rain. The falling of any water from the air to the surface of the earth is called precipitation. Examples of precipitation are rain, snow or hail. When the sun shines, water evaporates again, cools later and condenses and falls back again to the earth surface. Transpiration and respiration also contribute to the water cycle. Transpiration is the release of water from plants. Water is carried from the roots of the plant throughout the plant to the underside of the leaves where it evaporates off into the atmosphere. Animals also release water vapor to the atmosphere when they breathe out. This is called respiration. 

Now, it's time for your learning assessment

Answer the following questions. Good Luck!

Multiple Choice

Choose the best answer

Where does the energy for the water cycle come from?

• A. The Moon

• B. The Spin of the Earth

• C. Electricity

• D. The Sun

Multiple Choice

Choose the best answer

What is the main process by which water moves from land to the atmosphere?

• A. precipitation

• B. evaporation

• C. transpiration

• D. condensation

Multiple Choice

Choose the best answer

What is it called when plants release water that turns into vapor?

• A. transpiration

• B. precipitation

• C. evaporation

• D. condensation

Multiple Choice

Choose the best answer

Where is most of the water on Earth stored?

• A. lakes

• B. rivers

• C. oceans

• D. streams

Multiple Choice

Choose the best answer

Which of the following is a form a precipitation?

• A. rain

• B. hail

• C. snow

• D. all of the above

Multiple Choice

Trace the process of water cycle. Use the given hint to get the correct answer.

a substance that is very important to living things and covers almost 75% of the Earth’s surface

• evaporation

• respiration

• sun

• percepitarion

• water

Multiple Choice

Trace the process of water cycle. Use the given hint to get the correct answer.

water droplets that fall from the sky

• evaporation

• respiration

• sun

• percepitarion

• water

Multiple Choice

Trace the process of water cycle. Use the given hint to get the correct answer.

the energy source that drives the water cycle

• evaporation

• respiration

• sun

• percepitarion

• water

Multiple Choice

Trace the process of water cycle. Use the given hint to get the correct answer.

when animals release water vapor to the atmosphere

• evaporation

• respiration

• sun

• percepitarion

• water

Multiple Choice

Trace the process of water cycle. Use the given hint to get the correct answer.

when energy from the sun causes liquid water to change into water vapor

• evaporation

• respiration

• sun

• percepitarion

• water

Congratulations!

You are now done with the lesson.

Multiple Choice

Choose the best answer

Where does the energy for the water cycle come from?

• A. The Moon

• B. The Spin of the Earth

• C. Electricity

• D. The Sun