Water Cycle | Meaning & Concept [Explained]

We explain what the water cycle is and the different processes that make it up. Also, what are its stages and importance.

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What is the water cycle?

The water cycle or hydrological cycle is the process by which water circulates through the different components of the hydrosphere . The hydrosphere is made up of oceans, rivers, seas, clouds, rain, glaciers and other media in which water accumulates in its different states.

During the water cycle, water constantly changes its state of aggregation that is, it can go from liquid to gas, from solid to gas, from gas to liquid, from gas to solid, from solid to liquid and from liquid to solid. For example:

Water from a lake evaporates, then condenses into clouds and precipitates back into the lake.
The gaseous water present in the air condenses into clouds. If the temperature decreases, it solidifies and precipitates in the form of hail and accumulates in the form of ice.
Groundwater is absorbed by plants and then expelled into the air through transpiration. In the gaseous state it condenses in the air and precipitates and then infiltrates back into the underground layers of the soil.

Stages of the water cycle

The water cycle is made up of different processes, which are related to each other and to living beings:

Gaseous water formation

Evaporation . It consists of the transformation of water in oceans, rivers, lakes and seas into water vapor due to an increase in temperature.
Perspiration . Water vapor is formed due to the transpiration of plants and the sweat of animals.
Sublimation . It consists of the transformation of the solid water that forms glaciers into gaseous water.

Condensation . It is the process that occurs when gaseous water condenses in the atmosphere, and forms small droplets due to a decrease in temperature. This is how clouds are formed.

Precipitation . It is the process that occurs when the water droplets that form clouds cool and combine with each other, causing larger droplets to form that then fall towards the Earth's surface.

Infiltration . It is the process that occurs when water falls on the earth's surface. Due to precipitation, it passes through the surface pores, and begins to become groundwater. Infiltrated water can return to the atmosphere through evaporation or plant transpiration. It can also rise to aquifers.

Infiltration is affected by soil permeability; when the soil is poorly porous or contains a lot of moisture, infiltration is decreased.

Runoff . It is the process by which water slides across the earth's surface when it overflows the natural reservoir in which it is located. This water is one of the main means of transporting sediments and nutrients that are necessary for plants and some animals, which is why it is vitally important that it is not contaminated. Furthermore, runoff is one of the causes of soil erosion, especially when they are poorly permeable.

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Fusion . It occurs when solid water transforms into liquid water due to the increase in temperature. This is the case of melting snow, which turns into water.

Solidification . It is the process by which liquid water is transformed into solid water (ice). It occurs in the clouds: when the temperature decreases greatly, the water condensed in the clouds transforms into ice and precipitates in the form of snow or hail.

Importance of the water cycle

The water cycle ensures that water is reused over and over again by living organisms.

Thanks to the fact that during the cycle water transforms from one state of aggregation to another, it is possible for this resource to constantly transform from other states of aggregation to its liquid state (the most used by living beings), guaranteeing that it is not depleted. .

Nevertheless, It is very necessary to avoid contamination of water in any of its states of aggregation. because contaminated water often cannot be purified and reused.

Thanks to this cycle it is also possible for water to transport chemical compounds and nutrients that are used by animals, humans and plants.

Springs and groundwater flow

Water cycle - spring — Springs can be sources of drinking water.

The springs are the release of groundwater to the surface or to areas near the surface which can be used by animals and humans. Since this water has been filtered through the various layers of soil, springs can be sources of drinking water.

Springs are formed when rainwater infiltrates into an area higher than the area where the spring water emerges. That is why it is very important to avoid contamination of surface waters, to prevent contaminated water from infiltrating and contaminating the spring.

On the other hand, underground water currents can flow into rivers, lakes or seas without previously coming to the surface.

Seas and oceans

Seas are bodies of water located adjacent to the oceans. although sometimes they can be part of them. Seas are usually partially surrounded by land.

The seas and oceans are the largest reserve of water on planet Earth. with approximately 97% of the world's water amount. However, it is important to note that this water cannot be ingested by humans since it contains sodium chloride (NaCl), that is, it is salt water.

In addition to sodium and chlorine, other elements such as magnesium and bromine have been found in ocean water, which are currently exploited for commercial use.