Water Cycle: Definition, Process & Significance

Water cycle is known as the hydrologic cycle. It is a continuous process that involves movement of water to the core of the ground from the earth’s surface. Water is considered the main source of life. About \(70\% \) of the earth consists of water out of which \(97.5\% \) is present in oceans as saltwater and only \(2.5\% \) is freshwater. Out of this \(2.5\% \) of freshwater, only \(0.05\% \) is present in the liquid form present in rivers, lakes, ponds as well as in the form of underground water. Only this portion of water is responsible to support life and maintain the ecological balance on the earth.

Thus nature follows a well-defined mechanism to maintain a balance in the availability of freshwater. This process is known as the Water Cycle or Hydrological Cycle. It is the continuous movement of water in different forms within the earth and the atmosphere that includes five steps: Evaporation, Condensation, Precipitation, Runoff, and Percolation. The water cycle occurs in the Troposphere layer of the atmosphere. In this article, let’s learn everything about the water cycle in detail.

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Water Cycle: Definition

The water cycle is a magical and complex process that maintains the continuous motion of water rising from the earth, going up to the atmosphere, and again falling back to the earth. Liquid water evaporates into the atmosphere in the form of water vapour, condenses to form clouds, and precipitates back to earth in the form of rainfall and snowfall.

Water Cycle: Explanation

We can explain the water cycle, also referred to as the Hydrological Cycle as the continuous movement of water on, above, and below the surface of the earth. This cycle describes the various physical properties of water that make it go through the various movements on the planet ‘Earth’. Nine main physical processes create a continuous movement of water on the earth, they include evaporation, transpiration, condensation, precipitation, runoff, infiltration, percolation, and storage or collection.

Water Cycle: Model

Water Cycle: Steps

There are four basic steps in the water cycle known as evaporation, condensation, precipitation, and catchment (collection). Let us discuss them one by one in detail:

1. Evaporation

The water cycle begins with evaporation. In this process liquid water present on the surface of the earth, in rivers, lakes, ponds, oceans, etc., gets heated up in the presence of sunlight and changes into water vapours that escape to the atmosphere.

The rate of evaporation depends on the following factors:

1. Temperature: As the temperature increases, the rate of evaporation also increases because as the temperature goes higher, the kinetic energy of the water molecules at its surface also increases and therefore the faster the rate of their evaporation.
2. Surface Area: The rate of evaporation increases with an increase in surface area as there is more number of surface molecules per unit volume that can escape potentially.
3. Humidity: Relative humidity is the amount of moisture (water vapour) in the air compared to what the air can actually “hold” at that temperature. Relative humidity affects the evaporation rate to a great extent. An increase in relative humidity slows down evaporation or almost stops when it reaches \(100\% .\)

2. Condensation

We often observe water droplets on the wall of cold water bottles or cold drink cans, this is due to condensation. The process of conversion of water vapour (gas) into water droplets (liquid) in the atmosphere is known as condensation. As water vapours rise up in the atmosphere, it changes into tiny droplets as the temperature is very low at high altitude. These droplets come close together to form frost, dew, clouds, and fogs in the atmosphere.

3. Precipitation

The process by which liquid or frozen water is formed in the atmosphere and falls back to the earth is known as precipitation. It comes in various forms, like rain, hailstones, sleet, and snow. Along with evaporation and condensation, precipitation is one of the predominant connections in the water cycle that deliver atmospheric water to the earth. Due to wind or change in the temperature water droplets lose their heat energy, combine to make bigger droplets and when the air cannot hold any more water, it precipitates down as rain. If the temperature is very low (below 0 degrees), then the water droplets would also fall as snow.

4. Catchment or Collection

When water falls from the clouds in the form of rain, snow, hail, or sleet, it gets collected naturally in the oceans, rivers, lakes, streams, etc. Most of the rainwater gets to soak into the ground and will be collected as underground water under the influence of gravity.

Besides these basic steps, there are many other stages in the water cycle. Some of them are:

1. Transpiration – Plants return excess water to the atmosphere by a process known as transpiration as they take up the required amount of water from the soil through their roots. Transpiration is also a form of evaporation that includes the water movement in the form of water vapour through the aerial parts of plants such as leaves, stems, and flowers. Thus we can say that plants also sweat as humans do!
2. Sublimation – As we all know that sublimation is the direct conversion between the solid and the gaseous phases of matter, with no intermediate liquid stage. In the water cycle, sublimation is a process where ice caps in the mountains directly convert into water vapours without first melting into liquid water. Aside from evaporation, sublimation also contributes to water vapour in the air. This natural phenomenon accelerates when the temperature is low or pressure is high in the atmosphere.
3. Runoff – Runoff is the process where water that falls in the form of rainfall runs over the surface of the earth. Even after the snowfall, when the snow melts into water it also leads to runoff. As water runs or flows over the ground, it displaces the topsoil with it and carries the minerals along with the stream. This runoff integrates to form channels, rivers and ends up into ponds, lakes, seas, and oceans.
4. Infiltration – Some of the precipitated water that comes to the earth in the form of rainfall or others does not runoff into the rivers or absorbed by the plants or even gets evaporated. It is soaked up deep into the soil. This process is called infiltration. The water seeps down the earth and moves into rocks through cracks and pore spaces and increases the level of groundwater table. It is called pure water and is portable.

Water Cycle and Climate Change

The sun plays a major role in most of the steps of the water cycle. It is mainly dependent on the global temperature and this leads to various changes in the climate. Let’s discuss some of these factors:

1. With the increase in temperature, the rate of evaporation in a particular area increases. We can say that evaporation is higher in hot, dry, and windy climates. Evaporation also brings a cooling effect to the atmosphere.
2. The water cycle is associated with the continuous exchange of energy and climate change. While evaporation takes up energy and makes the environment cool. Condensation is associated with the release of energy making the temperature and climate stable.
3. In some areas where precipitation is higher, the weather becomes humid. For example, in coastal areas, we feel humidity because air directly absorbs moisture from the sea and at a certain level the moisture content comes at equilibrium with the environment.
4. Warmer temperatures related to climate change and increased carbon dioxide levels in the environment may speed up plant growth in regions with ample moisture and nutrients. This in turn would lead to increased transpiration.
5. In some areas, too hot and dry temperatures cause more evaporation, which increases the change of water into water vapour in the air to a great extent and causes drought.

Water Cycle: Significance

1. The Water Cycle is an extremely important process in our environment because it regulates the availability of fresh water on the earth which is the key substance for the survival of all living creatures. Without the water cycle, we would have run out of all freshwater.
2. The Water Cycle is also responsible for regulating the weather changes on the earth.
3. Some water that falls as the rain gets stored deep inside the ground improves the water table.
4. The water cycle also results in an exchange of energy that leads to a change in temperature.
5. During evaporation, water takes up energy and cools down the environment. This is also known as the cooling effect of evaporation.
6. The water cycle is solely responsible for rain.

Summary

Conclusively, the water cycle involves the circulation of water between the earth and the atmosphere in different forms. This continuous movement of water includes various stages known as Evaporation, Condensation, Precipitation, Runoff, and Percolation. The main component that runs the water cycle or hydrological cycle is the Sun. We all know that water is an essential component for our survival and that too we need freshwater for our daily needs which is present in the very little amount on the earth.

Thus, nature has maintained an amazing phenomenon known as the water cycle to replenish the fresh water in the atmosphere and to sustain it forever. It can be very fascinating to think that there might be the same amount of water on the earth as it was present when the earth was formed! There are several factors such as temperature, surface area, wind, etc., that play an important role in regulating the water cycle. Just imagine that without the water cycle we would not have clouds, rainfall, snowfall, rivers, lakes, and eventually no life on the earth. Thus the water cycle is a very important phenomenon by which freshwater naturally recycles itself and helps us to survive.

Frequently Asked Questions on Water Cycle

Frequently asked questions related to water cycle is listed as follows:

Q.1. What are the steps associated with the process of water cycle?
Ans: The steps involved in the process of water cycle can be understood if you go through the picture below:

Q.2. Among evaporation, condensation, sublimation, and precipitation, which is not a main part of the water cycle?
Ans: Sublimation is not a main part of the water cycle. As sublimation is the change of solid to gas directly. In the water cycle, liquid water evaporates to form water vapour.

Q.3. What is precipitation in the process of water cycle?
Ans: The process by which liquid or frozen water is formed in the atmosphere and falls back to the earth is known as precipitation. It comes in various forms, like rain, hailstones, sleet, and snow.

Q.4. What is the process of the water cycle?
Ans: The water cycle is the continuous movement of water rising from the earth, going up to the atmosphere, and again falling back to the earth in the form of rainfall, snowfall, hailstorm, etc.

Q.5. What is the water cycle? 
Ans: Water Cycle or Hydrological Cycle is the continuous movement of water in different forms within the earth and the atmosphere that includes five steps: Evaporation, Condensation, Precipitation, Runoff, and Percolation.

We hope this detailed article on Water Cycle is helpful to you. If you have any queries on this post or in general about the water cycle, ping us through the comment box below and we will get back to you as soon as possible.