How does the water cycle work? (A helpful illustrated guide)

Suppose, you have a glass of water. You put it outside for an hour or two on a sunny day. And, viola, the water is gone!!! 

Probably, many of us have experienced it in different forms. For example, you put wet clothes out and they dry up automatically.

So, where is the water going? Is the water gone for good? Can we get it back? These types of questions are pretty common.

The answer is hiding under one fascinating natural process that is happening every day. Do you know what it is? Yes, it is the water cycle.

• The above scenarios are just some of the phenomena that contribute to this amazing water cycle. In this article, we’ll be discussing everything you need to know about the water cycle to its entirety.

So, let’s go-

What is the water cycle?

• The water cycle is a natural set of processes that governs the perpetual flow of water at its different states all over the world. 

Water is one of the primary elements of our life. We can’t think of a single day without it. We need it every day not just for drinking, but for so many other purposes.

But, we’re so accustomed to using water that we don’t even bother how we’re getting it. 

That’s why many of us don’t know how the water travels from water sources, how it reaches us, and how it returns to its sources.

• As you can realize, the process is cyclic. That means the water that we consume, will always find its way back to nature, and then, again back to us.

This has been going on since the world was born. But, the complete process isn’t always straightforward.

So, let’s learn about it step by step.

What are the steps behind the water cycle?

If you look online or any books, you will find that there are so many steps behind the whole water cycle.

Most of the geologists picture the water cycle as a combination of six, continuous steps. The steps are as follows-

• Evaporation
• Sublimation
• Transpiration
• Condensation
• Precipitation
• Surface Runoff
• Infiltration

But, to make our understanding better, we’d like to divide the water cycle into three different phases.

The phases are as follows-

1. The first stage- when water makes its way into the atmosphere as steam
2. The second stage- when water gets back into the ground as liquid or solid form
3. The third stage- when water travels to the common water bodies

Now, let’s discuss these various phases further.

The first stage: When the water travels to the atmosphere

Being a cycle, we cannot identify one of the processes as first, second, or third. All these are happening in cyclic order.

But, still, for better comprehension, we need to label one as first or second.

• In our discussion, the first stage denotes the stage when water moves from the surface to the atmosphere.

So, we know what’s in the atmosphere, right? There is air. The air is a mixture of nitrogen, oxygen, and other gases. On the other hand, water is in liquid form.

As a result, the common question is “How does water get into the air?” Is it magic? No, it is science. We know the water can remain in three different states.

We mostly see water in liquid form.

• Naturally, in the mountains and artificially, inside our refrigerators, we see the solid form, which we call ice. 

And, as you boil the water, it turns to its gaseous form, which we call vapor.

• Now, many of us believe that to turn water into steam or vapor, we need to boil it. That’s not necessarily true.

So, let’s find out how water turns to vapor and makes it into the atmosphere.

Evaporation in the water cycle

• Many of us know that the water turns to steam at 100^o Celsius. But, it doesn’t reach that point in our nature unless you’re in a volcano.

So, how do our wet clothes dry out? There is a process called evaporation. 

• Evaporation means the process in which water molecules at various surfaces turn into vapor spontaneously.

How does this pan out? The water molecules at the surfaces continue to store heat over time. As a result, at the surfaces, the molecules will be at a higher temperature.

Now, with higher temperatures, the molecules will attain more velocity. In turn, it will get out of the surface and turn into vapor. 

With time, more and more water molecules continue to turn to vapor. This process is known as evaporation. 

So, this is the answer to the puzzle that we mentioned earlier. When you put out a glass of water under the sun, it will vanish. Also, when we put our wet clothes out, it dries out.

All of these happen due to evaporation. This is an integral part of the whole water cycle.

• Water from lakes, rivers, and oceans continue to turn into vapor at huge quantities all over the world. This is only possible due to evaporation.

So, you see, this accounts for the huge amount of vapor that is required to produce the clouds. Therefore, evaporation works as the principal driving force behind the water cycle.

• Why? That’s because more than 70 percent of the world’s surface is covered by water. So, water from these open sources continues to evaporate and contribute to the water cycle.

Transpiration in the water cycle

The next thing that contributes to the vapor raising to the atmosphere is the transpiration.

So, what’s transpiration? Transpiration is the process in which plants emit streams produced in photosynthesis through the stomata at their leaves.

Sounds wordy, right? So, let’s try to unravel it part by part. Firstly, many of us know about photosynthesis. Even if you don’t know it yet, don’t worry. We’re here.

Photosynthesis is a chemical process in which plants produce Glucose (C₆H₁₂O₆) with Carbon dioxide from the atmosphere and water from the soil.

Apart from Glucose, there are other byproducts like oxygen and steam. This whole process happens in the presence of sunlight and at a particular cell organism, named Chloroplast.

You can see the complete reaction below:

6CO₂ (atmosphere)+ 12H₂O (liquid) =(sunlight+chlorophyll)= C₆H₁₂O₆ + 12O₂ + 6H₂O (steam)

So, you see, for every photosynthesis reaction, we get six molecules of water as steam. There is a huge number of trees and forests out there.

During the sunlight, all these water molecules leave the trees and join the atmosphere. We call this process transpiration or evapotranspiration.

Transpiration plays a major role in the local ecosystem. Through transpiration, trees can control the humidity of its nearby environment.

Therefore, you can see, trees worldwide are contributing to the water cycle every day through transpiration. 

How? The water from the transpiration adds to the vapor in the atmosphere, which is the driving force behind the water cycle.

About 31 percent of the world is covered by trees. That’s why vapor emitting from transpiration has a gigantic contribution to the water cycle.

Sublimation in the water cycle

The next thing that contributes to the vapor quantity in the atmosphere is sublimation. If you know chemistry, you know it is a very interesting chemical phenomenon.

Sublimation is the process in which molecules from a solid turn to the gaseous state skipping the intermediate stage of melting to liquid.

A common example would be dry ice. In this case, CO₂ turns from its solid form to its gaseous form without forming any liquid.

The same thing can happen in the case of ice as well. So, through sublimation, ice can give rice to vapor which adds to the atmosphere.

But, this requires a very special environment. And, that is low atmospheric pressure.

As you rise further from the ground, air pressure starts to fall gradually. As a result, at the top of the mountains, there will be lower pressure compared to sea level.

Therefore, there is a higher chance of sublimation happening. Also, most of the mountains are covered with ice. So, you can guess, a huge amount of sublimation happens on the mountain tops.

The vapor generated through this goes into the atmosphere and by turn, contributes to the water cycle. 

From our above discussion, you can see that evaporation, transpiration, and sublimation are the processes working as the driving force to move vapor into the air naturally.

Apart from those, there are other contributory factors like vapors from industries, but they aren’t that significant.

There are other phenomena like volcanic eruption through which water below ground can come out directly in vapor form.

The second stage: When water comes back to the ground

The second stage is when the water comes back down to earth in liquid or solid form.

It consists of two different phases. The first one is condensation when vapor changes to liquid or solid forms. The second phase is precipitation. In this phase, water travels down to earth.

Now, let’s dive into the details.

Condensation in the water cycle

Condensation marks a transitional phase during the water cycle. In the previous stages, we saw how evaporation, transpiration, and sublimation free vapor into the air.

So, what is condensation? Condensation is a physical process through which a gaseous substance turns to liquid. 

Now, let’s clarify it with an example. Suppose you have a bottle filled with cold water. You put it on the table. And, after sometimes, you see water running down on the sides of the bottle.

So, the natural question is “From where is this water coming?” Is it from inside of the bottle or somewhere else?

The answer is the water that we see on the surface of the bottle comes from the air. We know that air has a certain amount of steam in it. 

This water vapor comes in contact with the cold surface and turns to water droplets. This is what condensation is.

This process also replicates in nature. As you rise from the surface of the earth, the temperature starts to drop. As a result, the air around the ground is hotter than that in the sky.

Therefore, the water vapor, being lighter, starts to climb up. At a high enough altitude, it crosses the dew point and turns to water. The water doesn’t drop then and there.

It continues to gather around and line up a formation that we call the cloud. Although clouds also consist of other substances, its primary constituent is water.

So, you see, condensation is a significant step in the water cycle as it creates a pathway for water molecules to come back to earth.

Now, let’s find out about precipitation.

Precipitation in the water cycle

The next phase that works to bring the water back to the surface of the earth is the precipitation phase.

Precipitation is the process through which water from the clouds comes down on earth in the form of raindrops, snowing, dew, or other similar formations.

From the previous section, we came to know that the water vapor in the air starts condensing at higher altitudes. This, in turn, forms clouds.

We also mentioned that temperature drops as we start to go further above us. As a result, there is a chance that the temperature might go below the dew point at that height.

As a result, the air cannot hold the water vapor much longer and it starts to drop down in various forms. The common one is the rain. 

In general, rain can occur in various forms. Sometimes it drizzles, sometimes it comes down in storms.

There are other types of rains as well. Snowing is a common type of rainfall encountered in many regions of the earth. In this case, the vapor comes down in the form of ice.

There are also blizzard, snowstorms that occasionally happen during the winter. In all these cases, one thing is common.

In all of these, water vapor comes down to the earth and that water contributes to the water cycle. 

All this happens only due to condensation and precipitation. Therefore, you can guess, these two phases are vital to perpetuate the water cycle.

The third stage: When water travels back to its sources

The final stage that we’d be talking about is when the water flows back into its primary sources. There are two phases involved in this.

The first one is run off through which water finds its way into the surface water sources.

The second one is called infiltration. Through this one, the water enters into the ground and joins the sparsely connected storage of groundwater.

So, let’s find out the details.

Surface Runoff in the water cycle

We know that about 70 percent of the world’s surface is covered with water. As a result, there are so many natural water sources around us.

The primary one is the ocean. We know that there are five different oceans around the world: 

The Pacific Ocean, the Atlantic Ocean, the Indian Ocean, the Southern Ocean, and the Arctic Ocean.

These oceans hold the most amount of surface water of the earth. Apart from this, we also have numerous numbers of local and international rivers all over the world.

Let’s name a few of those. The Amazon in South America, the Nile in Africa, or the Mississippi in North America. These are some of the famous rivers around the world.

These rivers also create branches and subbranches which continue to contain water all around the year. And, that’s not all. There are other sources like the lakes, canals, or the fountains.

All these carry water and they get that water due to condensation and precipitation. It rains everywhere not only over the water bodies alone.

So, water that falls on the ground continues to gather. Eventually, it finds its way into the water bodies through runoff. 

During runoff, when water goes into the lakes, canals, rivers, or ocean, it will pick up minerals from the surface. Due to this, the water picked up from the rivers, or lakes will have a high TDS level.

The water treatment plants work around the clock to bring us water at a safe TDS and pH level.

If you want to know about water treatment plants, you should visit our post here.

Also, if you want to know about TDS levels of water, click on the link here. Besides, check out this post to know more about the pH of water.

Infiltration in the water cycle

Infiltration marks the final phase when water travels back into the underground. This one is very crucial in many geological aspects.  

Infiltration is the process through which water droplets on the surface make their way into the soil and eventually in the huge interconnects of underground water.

As we previously mentioned, raindrops fall all over the surface. Most of the water droplets can make their way into the surface water sources through the drainage and sewerage.

But, some of the droplets can’t find the way. Those seep into the soil and keep on moving. In turn, they reach their intended destination and increase groundwater.

Groundwater is the water that is buried underneath the surface of the earth. One might question their impact on the water cycle.

Although groundwater is under the surface, people are using technologies to dig through the soils and get the water out.

In many countries, groundwater is used for agricultural purposes as well. In this case, they use deep tube wells and submersible pumps.

After the water reaches the surface, it can directly influence the water cycle. That’s why infiltration is very significant in the completion of the water cycle.

Conclusion

Throughout the whole article, we tried to explore various key components of the water cycle. We learned how water vapor is created through evaporation, transpiration, and sublimation.

We also found out about the key concepts of cloud formation through condensation. Then, we saw how precipitation occurs to bring that water back into the surface of the earth.

Finally, we discussed runoff and infiltration through which water finds its way back into its primary sources. 

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