What is the water cycle

What is the water cycle

When the term water cycle is used, it generally refers to the constant movement of water from one place to the other in different forms, within our planet. During this ongoing cycle, water is observed to be existent in air, on ground and also below ground. Within the period of the cycle, water goes through all its three primary forms, which are liquid, solid and gaseous, depending on the location, temperature and other environmental factors. Also known as the hydrologic cycle, it should be noted that under normal circumstances, this cycle ensures that the overall balance of the various forms of water remain relatively the same within the atmosphere. This constant movement is brought on by nature itself through various processes such as condensation, precipitation (rain, snow and hail), evaporation, infiltration, underground movements and even runoff. As one can imagine, the sun and the wind are the most important agents of nature which initiate the water cycle. It also plays a very prominent role in controlling the climate and temperature of a particular area as the entire chain is based on heat exchange.

The Chain of Processes

Although it is a constant cycle, the first step is considered to be evaporation. The heat from the sun evaporates large amounts of water from all the water bodies (seas, oceans, rivers, lakes etc) on the surface of the earth. However, the sun’s heat also creates water vapor directly when it touches ice and snow on the surface; this process of turning water into vapor, directly from ice is known as sublimation. Other sources of water which are evaporated by the heat of the sun include even moisture from the soil and the vegetation (known as evapotranspiration).

Next the wind comes into play, as it takes all this water vapor high enough to find appropriately cooler temperatures suitable for cloud formation (the process is known as condensation). Now the moving air constantly keeps these clouds in motion until they grow large enough and start colliding among themselves, which of course, gives way to precipitation. Depending on the temperature and the location, the precipitation could be either in the form of rain, sleet or snow.

A portion of this precipitation which drops directly into the water bodies is returned back to its origin, but some of it also drops on land, giving way to surface runoff. Quite a large portion of this runoff goes back to the nearest lakes and rivers but not all of it. It is to be noted that rivers ultimately pour into the oceans, but fresh water lakes do not.

The rest of the surface runoff however, seeps into the ground while on the movement or standing still. This is known as infiltration and it is due to this process that the water-bearing permeable rocks or aquifers are fed with a new supply of fresh water every once in a while. These rocks have been found to be a good source of freshwater, especially since they can hold the freshwater in them for a significantly long period of time.

The interesting fact is that even most of this underground water ultimately finds its way to the ocean as well. Not all of the infiltrated water fills aquifers, in fact a fraction of the water which did not go deep enough to reach the aquifers can also seep back into the river in time. This kind of underground water seepage is termed as groundwater discharge. At times, it is also seen that ground water has found an opening and therefore has managed to emerge back onto the surface of the earth as a freshwater spring.

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