Without water, life would not exist. Imagine all the amount of water that we all use every day in our lives! Plants and animals also use water every day! Even our factories and machines need water to run on. So, how does water on Earth never run out?
The answer is, Earth has been recycling water ever since it was formed, which was over 4 billion years ago. Water on Earth moves between seas, land and air in an ongoing cycle called the water cycle. During its cycle, water changes its form. It can be in the form of liquid, gas or solid.
There are four different processes that the water cycle goes through: evaporation, condensation, precipitation and collection. Let’s learn about them in detail.
The Sun heats up the water on Earth that is found in rivers, oceans and lakes. When the temperature of water rises, some of the water turns from liquid to gas. This gas is called water vapour, and the turning process is called “evaporation”. Evaporation also occurs in plants. Some water turns into vapour through the leaves of plants. This process is called transpiration. The water vapour rises up in the sky and settles in the atmosphere, then it gathers to form clouds.
Water vapour in the clouds starts to cool down. The air moves the clouds around the globe. When vapour is cool enough, it turns into water again, mostly as rain. The transition from gas to liquid is called “condensation”. So, condensation is the opposite of evaporation.
When too much water vapour gets condensed, water drops in the clouds become too heavy for the air to hold. As a result, they fall down from the sky in the form of rain, sleet, snow or hail. The water falling process is called “precipitation”.
The final part of the water cycle is called “collection”. Water that falls from the sky is collected in many ways, and then it will evaporate back into the air to begin the cycle all over again.
Some water falls directly into oceans, rivers or lakes. Water that falls on the land may flow on the ground until it reaches oceans, rivers or lakes. This water is called “surface run-off”. If the water falls on plants, it may evaporate again from the leaves through transpiration, or it may soak into the soil. From the soil, water slowly moves through the ground until it reaches a river, a lake or an ocean.
In cold places, water that falls from the sky may turn into ice or glaciers. If the temperature rises, ice melts to liquid water and collects into any water body.
So, this is how the water cycle goes:
Heat from the Sun causes water in oceans, lakes and rivers to evaporate and rise up to the atmosphere. Water from plants and trees also enters the atmosphere through the process of transpiration. As water vapour rises high in the sky, it forms clouds and it condenses. When a cloud becomes heavy with water, precipitation occurs. Then, water collects in oceans, lakes and rivers, and the cycle starts all over again.
Why Is the Water Cycle Important?
The water cycle is very important because it ensures that water never runs out on Earth, so that all living organisms can survive. If water did not naturally recycle itself, we would run out of clean water, which is essential to life. In addition, the water cycle has an important role in balancing temperatures and weather patterns on Earth.
Human Activities that Affect the Water Cycle
Humans are responsible for disrupting and changing the water cycle in numerous ways; for example:
- The burning of fuels raises the Earth’s temperature. The increase of temperature causes an increase of evaporation and melting ice and glaciers.
- Using pesticides and other chemicals for farming runs off into rivers and natural water resources and pollutes water.
- Some emissions from industry cause acid rain.
- Deforestation has a huge effect on the water cycle because, as we knew, trees release water vapor into the atmosphere through transpiration. So, if we cut down trees, less water evaporates, and then there is less rain.
- Humans change the flow of water in many ways, such as using irrigation, damming lakes and rivers to generate electricity, and pulling water out of the ground in order to use it.
15 Interesting Facts about the Water Cycle
- The water cycle is also known as the “hydrologic cycle”.
- Water can sometimes change into vapor from ice without first melting into liquid. This process is called “sublimation”.
- The driving energy of the water cycle comes from the Sun. When the Sun heats water on Earth, water evaporates and the cycle goes on.
- 90% of all the water that evaporates into the atmosphere is from oceans.
- Water exists in three different states in the water cycle; liquid, gas and solid. The amount of water in each state varies, but the amount of all water on Earth remains the same.
- Every time water changes from one state to another, or when it moves from one place to another, it either produces or absorbs energy.
- About 97% of water on Earth is salty. This means that only 3% of the Earth’s water is freshwater. 2% of this freshwater is frozen in ice and glaciers. So, we only have access to about 1% of all the water on Earth.
- The atmosphere contains more freshwater than that in all the rivers on Earth combined.
- Water in ice caps and glaciers is the purest form of water available on Earth.
- About 90% of the ice on Earth exists in Antarctica.
- Glaciers cover about 10% of the Earth’s surface. In fact, the sea levels would go up by 70 meters if all the Earth’s glaciers melted today.
- Groundwater gathers salts and minerals from the soil during its journey to the ocean, which is part of the reason why the ocean water is salty.
- Ice is lighter than liquid water, and this is why ice floats in water.
- Even in industries, the water cycle is essential. For example, it may take about 4000 liters of water to produce a car.
- The human brain is made up of 75% water. Likewise, a living tree is 75% water.