Water Cycle Definition and Meaning
What is the Water Cycle?
The water cycle, also known as the hydrological cycle, is the process of transformation and circulation of water on Earth.
In this sense, the water cycle consists of the transfer of water from one place to another, changing its physical state: going from a liquid to a gaseous or solid state, or from a gaseous to a liquid state, depending on the environmental conditions.
On Earth, water is distributed in seas, rivers or lakes in a liquid state; in the glaciers of the poles and mountains in a solid state, and in the clouds in a gaseous state.
Depending on the phase of the process, the water will be found in one place or another. Next, we will explain schematically and with illustrative images how water circulates in each of its stages.
Stages of the water cycle
Phase 1: Evaporation
The water cycle begins with evaporation. Evaporation occurs when the sun heats the surface of the waters of rivers, lakes, ponds, seas and oceans. The water, then, turns into steam and rises to the atmosphere, where the next phase will take place: condensation.
Phase 2: Condensation
The next stage of the water cycle is condensation. During this phase, the water vapor that has risen to the atmosphere thanks to evaporation, concentrates in drops that will form clouds and mist. Once there, the water will go into its liquid state again, which takes us to the next step: precipitation.
Phase 3: Precipitation
Precipitation is the third step in the water cycle. It takes place when condensed water from the atmosphere descends to the surface in the form of small drops.
In the coldest regions of the planet, however, water changes from a liquid to a solid state (solidification) and precipitates like snow or hail. Subsequently, when thawing occurs, the water will return to a liquid state in a process known as melting.
Phase 4: Infiltration
The fourth stage of the water cycle is infiltration. Infiltration is known as the process in which the water that has fallen on the earth’s surface as a consequence of rainfall penetrates the soil. One part is exploited by nature and living beings, while the other is incorporated into groundwater.
Phase 5: Runoff
Runoff is the final stage of the water cycle. This phase comprises the movement of water through the surface, thanks to the slopes and accidents of the terrain, to re-enter rivers, lakes, lagoons, seas and oceans, which constitutes the return to the beginning of the cycle.
Runoff is also the main geological agent for erosion and sediment transport.
Importance of the water cycle
The water cycle is essential for the maintenance of life on Earth and for the sustenance of all terrestrial ecosystems. It also determines climatic variation and interferes at the level of rivers, lakes, seas and oceans.
Human beings have the responsibility to preserve the proper functioning of the water cycle, since human action has led to climatic changes and contamination in the biosphere, putting at risk the distribution of water and life on Earth.