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 composed of oceans, rivers, seas, clouds, rain, glaciers and other means in which water accumulates in its different states.
In the water cycle , water changes state , passing from the liquid to the gaseous state and vice versa, and from the liquid to the solid state and vice versa.
Being a cycle, it is a process without beginning or end. Therefore, any point can be chosen to describe the beginning of the cycle. For example, all of the following possibilities are correct:
- The water in a lake evaporates, then condenses into clouds and then plunges back into the lake.
- The water in the gaseous state of the air condenses into clouds, if the temperature drops solidifies and precipitates in the form of hail and accumulates in the form of ice.
- The groundwater is absorbed by the plants and then expelled into the air through transpiration, in a gaseous state it condenses in the air and precipitates and then re-infiltrates underground layers of the soil.
Parts of the Water Cycle
Evaporation and perspiration
Water can pass to the atmosphere air in a gaseous state from two sources:
Surface water streams and water mirrors : Water in the liquid state in nature always contains multiple substances, both organic and inorganic. However, when it evaporates, it does so in the form of a pure molecule. Therefore, evaporation is a natural way of water purification.
Transpiration : Living beings use water to carry out their metabolism. While many plants can use salt water, most animals, including humans, consume fresh water, that is, water found in rivers and lakes. This water is expelled by organisms either in the form of waste (the urine of the animals, which returns to underground or surface currents) or in the form of perspiration. In other words, organisms expel water into the atmosphere in different ways:
- Sweating animals
- Breathing animals
- Transpiration of plants
The water in the atmosphere condenses into clouds or haze.
The tiny drops that form the clouds require a specific temperature and pressure range to remain suspended in the air, when the temperature or pressure decreases, these tiny drops fall to the earth in the form of:
- Rain : The drops come together forming larger drops, visible individually
- Snow : The drops solidify in groups that form snowflakes
- Hail : The drops solidify into larger groups, forming blocks of ice that fall faster due to their weight
Runoff is defined as all forms in which water in a liquid state slides downhill on the surface of the earth. That is, it refers to streams and rivers.
The runoff is a force that modifies the land to cause erosion. That is why most rivers and streams, even seasonal ones, have a marked channel in not only the earth but also can erode rigid surfaces such as stone.
Surface currents also have a biological function, not only because they contain plants and animals inside, but also because they transport organic sediments that are used by various organisms as food or dissemination of their species.
For these reasons, it is of central importance for ecosystems that these water currents are not contaminated. In addition, runoff is fresh water, meaning that if it is not contaminated it is drinking water for humans and other animals.
Fresh water stored
The accumulations of fresh water on the surface are ecosystems where plant and animal organisms coexist. The fresh water they contain comes from rivers, streams, underground sources and rain.
They may be:
- Lagos : Although it is imperceptible, the lakes have a current, since in addition to receiving water, they have an outlet, forming small streams or even rivers.
- Lagoons : Water has no current, meaning that it remains stagnant.
Ice and snow
The water is transformed into ice or snow through the solidification process : when the temperature is below 0 degrees, the water turns into ice.
However, if a cloud finds a temperature below 0 degrees at low altitude, snowflakes form, which accumulate on the ground when falling. In order for snow or ice to accumulate, the ambient temperature at the place where it falls must also be less than 0 degrees.
Different types of soil are porous, that is to say that between their molecules there are holes through which water can pass. The more porous the soil, the more water will infiltrate, passing underground layers.
Another factor that affects infiltration is soil moisture: when the soil is completely moistened and does not have more porous underground layers, water accumulates on the surface.
Below the ground there is an erosion of water currents similar to that carried out by surface runoff. True underground currents are formed but also storage, either by the moisture of the substrate, which can be used by the plants, or forming deposits.
Springs and groundwater discharge
The springs are the exit of the underground currents to the surface or to zones near the surface, that can be used by the animals. Since this water has been filtered by the various layers of soil, the springs can be sources of drinking water.
On the other hand, underground currents can flow into rivers, lakes or seas without even surfacing.
Seas and oceans
The seas and oceans are the largest reservoir of water on the planet , with approximately 97% of the world’s water supply. However, it is important to note that this water is not potable for human beings since it is salt water.