The importance of the water cycle for the planet

water is of vital importance for life on the planet. The water cycle

Surely sometime, throughout your life, you have been explained what the water cycle is. All the process that it has since it precipitates in the form of rain, snow or hail until it evaporates again and forms clouds. However, each part of the process that this water cycle has has elements and aspects that are fundamental to the development of life and the survival of many living beings and its ecosystems.

Would you like to know step by step the importance of the water cycle on the planet?

What is the water cycle?

summary on the stages of the water cycle

On Earth there is a substance that is in continuous movement and that can be in three states: solid, liquid and gaseous. It's about the water. Water is continually changing state and belongs to a continuous process that has been going on for billions of years on our planet. Without the water cycle, life as we know it could not develop.

This water cycle does not start in any specific place, that is, it has no beginning or end, but is in continuous movement. To explain it and make it easier, we will simulate a beginning and an end. The water cycle begins in the oceans. There, the water evaporates and goes into the air, transforming into water vapor. The ascending air currents due to variations in pressure, temperature and density cause the water vapor to reach the upper layers of the atmosphere, where the lower air temperature causes the water to condense and clouds form. As the air currents grow and alternate, the clouds grow in size and thickness, until they fall as precipitation. 

Precipitation can occur in several ways: liquid water, snow or hail. The part of the precipitation that falls in the form of snow accumulates forming ice sheets and glaciers. These are capable of storing frozen water for millions of years. The rest of the water falls as rain on the oceans, seas and the land surface. Due to the effect of gravity, once they fall on the surface, surface runoff is generated that gives rise to rivers and streams. In rivers, the water is transported back to the ocean. But not all the water that falls on the earth's surface goes to rivers, rather much of it accumulates. A large part of this water is absorbed by infiltration and it remains stored as groundwater. Another is stored forming lakes and springs.

The infiltrated water that is shallow is absorbed by the roots of the plants to feed and part of it transpires through the surface of the leaves, so it returns to the atmosphere again.

In the end, all the waters end up in the oceans again, since what evaporates, quite possibly, falls back in the form of precipitation on the seas and oceans, "closing" the water cycle.

Stages of the water cycle

The water cycle has various components that follow one another in stages. The US Geological Survey (USGS) has identified 15 components in the water cycle:

  • Water stored in the oceans
  • Evaporation
  • Water in the atmosphere
  • Condensation
  • Precipitation
  • Water stored in ice and snow
  • Melt water
  • Surface runoff
  • Water stream
  • Stored fresh water
  • Infiltration
  • Groundwater discharge
  • Springs
  • Perspiration
  • Stored groundwater
  • Global water distribution

The water stored in the seas and oceans

the ocean stores the most water on the planet

Although it is thought that the ocean is in a continuous process of evaporation, the amount of water that is stored in the oceans is much more than that which evaporates. There are about 1.386.000.000 cubic kilometers of stored water in the ocean, of which only 48.000.000 cubic kilometers they are in continuous movement through the water cycle. The oceans are responsible 90% of the world's evaporation.

The oceans are in constant motion thanks to the dynamics of the atmosphere. For this reason, there are the most famous currents in the world such as the Gulf Stream. Thanks to these currents, the water from the oceans is transported to all places on Earth.


water evaporates even if it is not boiling

It has been mentioned before that water is in continuous change of state: vapor, liquid and solid. Evaporation is the process by which water changes its state from a liquid to a gas. Thanks to it, the water found in rivers, lakes and oceans rejoins the atmosphere in the form of vapor and, when condensing, forms clouds.

Surely you have thought that why the water evaporates if it is not boiling. This happens because the energy in the environment in the form of heat is capable of breaking the bonds that hold the water molecules together. When these bonds are broken, the water changes from a liquid state to a gas. For this reason, when the temperature rises to 100 ° C, the water boils and it is much easier and faster to change from a liquid to a gas.

In a total water balance, it can be said that the amount of water that evaporates, ends up falling again in the form of precipitation. This however varies geographically. Over the oceans, evaporation is more common than precipitation; while on land precipitation exceeds evaporation. About 10% of the water only that vaporizes from the oceans falls on Earth in the form of precipitation.

Water stored in the atmosphere

air always contains water vapor

Water can be stored in the atmosphere in the form of vapor, moisture, and forming clouds. There is not much water stored in the atmosphere, but it is a fast track for water to be transported and moved around the world. There is always water in the atmosphere even if there are no clouds. The water that is stored in the atmosphere is the 12.900 cubic kilometers.


clouds are formed by condensation of water vapor

This part of the water cycle is where it goes from a gaseous to a liquid state. This section It is essential for the clouds to form that, later, will give the precipitation. Condensation is also responsible for phenomena such as fog, fogging up the windows, the amount of humidity of the day, the drops that form around the glass, etc.

Water molecules combine with tiny particles of dust, salts, and smoke to form cloud droplets, which grow and form clouds. When cloud droplets get together they grow in size, forming clouds and precipitation can happen.


precipitation in the form of rain is the most abundant

Precipitation is the fall of water, both in liquid and solid form. Most of the water droplets that form a cloud do not rush, since they are subjected to the force of upward air currents. For precipitation to take place, the drops must first condense and collide with each other, forming larger water droplets that are heavier enough to fall and overcome the resistance that the air puts up. To form a raindrop you need many cloud droplets.

Water stored in ice and glaciers

glaciers have large amounts of retained water

The water that falls in regions where the temperature is always below 0 ° C, the water is stored forming glaciers, ice fields or snow fields. This volume of water in solid state is stored for long periods of time. Most of the ice mass on Earth, about 90%, it is found in Antarctica, while the remaining 10% is in Greenland.

Thaw water

The water resulting from the melting of glaciers and ice and snow fields flows into water courses as runoff. Worldwide, runoff produced by meltwater is an important contributor to the water cycle.

Most of this meltwater takes place in spring, when temperatures rise.

Surface runoff

meltwater and rain create surface runoff

Surface runoff is caused by rainwater and is normally led to a watercourse. Most of the water in rivers comes from surface runoff. When it rains, part of that water is absorbed by the ground, but when it becomes saturated or impermeable, it begins to run on the ground, following the incline of the slope.

The amount of surface runoff varies by relation to time and geography. There are places where rainfall is abundant and intense and leads to stronger runoff.

Water stream

the water runs its course in the rivers

The waters are in continuous movement as it can be in a river. Rivers are important both for people and for other living things. Rivers are used to supply drinking water, irrigation, produce electricity, eliminate waste, transport products, obtain food, etc. The rest of the living beings they need river water as a natural habitat.

Rivers help keep aquifers full of water, as they discharge water into them through their beds. And, the oceans are kept with water, as rivers and runoff are continually discharging water into them.

Fresh water storage

groundwater supplies cities

The water found on the earth's surface is stored in two ways: on the surface as lakes or reservoirs or underground as aquifers. This part of water storage is vitally important for life on Earth. Surface water includes streams, ponds, lakes, reservoirs (man-made lakes), and freshwater wetlands.

The total amount of water in rivers and lakes is continually changing due to the water entering and leaving the system. The water that enters through precipitation, runoff, the water that leaves through infiltration, evaporation ...


description of the infiltration process

Infiltration is the downward movement of water from the Earth's surface towards the soil or porous rocks. This seeping water comes from precipitation. Some of the water that infiltrates remains in the most superficial layers of the soil and can re-enter a watercourse as it seeps into it. Another part of the water can infiltrate deeper, thus recharging the underground aquifers.

Groundwater discharge

It is the movement of water out of the ground. In many cases, the main tributary of water for rivers comes from groundwater.


portion of water from springs

Springs are the areas where groundwater is discharged to the surface. A spring results when an aquifer fills to the point where the water overflows to the surface of the land. Springs vary in size, from small springs that only flow after heavy rains, to large pools where they flow million liters of water daily.


plants perspire

It is the process by which water vapor escapes from plants through the surface of the leaves and goes into the atmosphere. Said like this, perspiration is the amount of water that evaporates from the leaves of plants. It is estimated that around 10% of the humidity of the atmosphere it comes from the perspiration of the plants.

This process, given how small the evaporated water droplets are, is not seen.

Stored groundwater

This water is what has remained for millions of years and is part of the water cycle. The water in the aquifers keeps moving, although very slowly. Aquifers are the great stores of water on Earth and many people around the world depend on groundwater.

With all the stages described you will be able to have a broader and more elaborate vision of the water cycle and its importance on a global scale.

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  1.   Maria B. said

    I loved your article. Very illustrative.
    It seems that the last point is missing: Global distribution of water.
    Thank you very much for enlightening us in this interesting topic.

    1.    German Portillo said

      Thank you very much for reading it! Greetings!