What is the water cycle? You might know the water cycle definition as a simple cyclical phenomenon of evaporation, freezing, and precipitation. No doubt this way it is easy to understand, but the matter is much more complicated. The influence of the water cycle on the Earth’s ecosystems is extremely complex and not completely comprehended. NOAA ( National Oceanic and Atmospheric Administration) is working towards expanding the understanding of the water cycle definition at the global level aimed at improving our ability to predict the weather, climate, water resources, and assess the ecosystem health.
Stages of Water Cycle
Many processes are involved in the movement of water besides the major steps given in the water cycle diagram above. Below are different the water cycle steps:
Evaporation: The sun is the paramount energy source, powering most of the evaporation that occurs on Earth. Evaporation typically occurs when water molecules at the surface of water bodies get excited and ascent into the air. The molecules carry the highest kinetic energy from the water vapour clouds. Evaporation usually occurs below water’s boiling point. There is another transcription water cycle called evapotranspiration that takes place when evaporation happens via the leaves of plants. This process gives off a large percentage of water in the atmosphere.
Sublimation: Sublimation occurs when ice or snow directly changes into water vapour without entering the liquid state (can be seen in the water cycle diagram above). It typically occurs because of winds with less moisture content and decreased humidity. Sublimation is seen on mountain tops because the pressure of the atmosphere is extremely low. The low air pressure helps the snow sublimate to water vapour as less energy is used. The starting point for sublimation on Earth is the ice sheets covering its poles.
Condensation: The water vapour amassed in the atmosphere eventually cools down because of the low temperatures found at high altitudes. These vapours change into tiny water and ice droplets, eventually assimilating to form clouds.
Precipitation: Above zero degrees centigrade, the vapours condense to form water droplets. However, they cannot condense in the absence of dust particles or other impurities. Therefore, water vapours attach themselves to the surface of these particles. When adequate droplets combine, they fall out of the clouds and onto the ground beneath through a process called precipitation or rainfall. In extremely cold weather or particularly low air pressure conditions, the water droplets condense and come down as hail or snow.
Infiltration: Rainwater absorbs into the ground through a process called infiltration. The level of absorption differs depending on the substance the water has seeped into. For example, rocks retain relatively less water than soil. Groundwater either follows streams or rivers. But sometimes, it sinks deeper, forming aquifers.
Runoff: If the rainwater does not form aquifers, it follows the course of gravity, often flowing down the mountain and hillsides and eventually forming rivers. This phenomenon is referred to as runoff. In regions with freezing temperatures, ice caps form when the snowfall amount is more, and it is more rapid than the degree of evaporation or sublimation. The biggest ice caps on Earth can be found at the poles.
All the steps mentioned above occur in a transcription water cycle with neither a fixed point of commencement nor completion.
Hydrometeorology is the branch of meteorology that is concerned with problems regarding the hydrologic cycle, the water budget, and the rainfall statistics of storms. The boundaries of the hydrometeorology branch are not distinct, and the problems of Hydrometeorology merge with those of the climatologist, the cloud physicist, the hydrologist, and the weather forecaster. Substantial emphasis is placed on theoretically or empirically determining the relationships between meteorological factors and the maximum precipitation that reaches the ground.
These findings often serve as the basis for designing structures for flood control and water usage, especially dams and reservoirs. Other roles of hydro meteorologists include the estimation of rainfall probabilities, the space and time distribution of evaporation and rainfall, the recurrence interval of consequential storms, the melting of snow and runoff, and predictable wind tides and waves in reservoirs. The entire field of water quality and supply is of paramount importance in Hydrometeorology.
Implications of the Water Cycle
The water cycle has a huge impact on the Earth’s climate. For example, the greenhouse effect causes the temperatures to rise. Without the evaporative cooling influence of the transcription water cycle on the temperatures on Earth, those would rise drastically.
The water cycle is also an inherent part of other natural cycles on Earth. It influences all forms of life on Earth and is also known to purify the air. For example, during precipitation, water vapours have to link themselves to dust particles, so it renders the air clean. In polluted regions, the raindrops, besides taking up dust, take up water-soluble gas particles as well as pollutant particles as they descend from the sky. Raindrops also attach biological particles like bacteria and industrial dust fragments and smoke particles to themselves.
The water cycle on Earth
Water is vital to life on Earth. In its three phases— solid, liquid, and gaseous, it combines the main aspects of the climate system of Earth, namely the atmosphere, clouds, oceans, lakes, crops, snow-laden mountains, and glaciers.
The water cycle steps reveal the continuous movement of water within the Earth and its atmosphere. It is an integrated system, including diverse processes. Water in liquid form evaporates to form water vapour, condenses into clouds, and falls back to Earth in the form of rain or snow. Water moves through the atmosphere in different phases. Liquid water glides across the land (runoff), into the Earth (infiltration and percolation), and into the ground (groundwater). Groundwater is taken up by plants and evaporates into the atmosphere from plants. Ice and snow can directly change into a gas (sublimation). The opposite can also occur when water vapour changes into a solid form (deposition).
Water, society, and ecology
Water affects the intensity of climate variability and alteration. It forms a major part of extreme events like drought and floods. Its timely delivery and abundance are important for meeting the demands of society and ecosystems.
Humans utilise water for drinking, industrial applications, irrigating crops, hydropower, disposal of wastes, and recreation. Water sources must be protected both for the use of humans and the health of the ecosystem. In many regions, water supplies are being exhausted due to population growth, pollution, and development. These stresses have been rendered worse by variations in the climate and changes that influence the hydrologic cycle.
Formation of dew
It is the deposition of water droplets formed during the night by the cooling of vapours of water from the atmosphere onto the object surfaces that are exposed freely to the atmosphere. It develops on clear nights when the atmosphere is calm or when the wind is light. If the temperature on the surface of the Earth is lower than the water’s freezing point, the deposit takes the form of hoarfrost.
Dew is formed on clear nights as on such nights, surfaces that are freely exposed give off heat to the sky through radiation. Unless this loss is balanced by efficient heat conduction from the interior of the object, the surface will cool. Most objects, like grass blades, leaves, and petals, are much more efficient radiators than air and, consequently, are generally colder than the air at night. The cold surface brings down the temperature of the air in its vicinity, and if the air carries sufficient atmospheric humidity, its temperature may go below its dew point. Once this happens, water vapour condenses out of the air onto the surface.
Climate change affects where, when, and how much water is accessible. Extreme weather conditions and events like droughts and heavy rainfall, which are expected to rise as the climate changes, can influence water resources. A lack of adequate supply of water, flooding, or degraded quality of water impacts civilization currently and has done so throughout history. These challenges can influence the economy, energy production and utilisation, human health, transportation, agriculture, national security, natural ecosystems, and recreation.
Frequently Asked Questions
1. What are the four major water cycle steps?
The four major water cycle steps are evaporation of water, condensation, precipitation and collection. The sun evaporates water from the water bodies and contributes to water vapour formation. These water vapours accumulate in the atmosphere in the form of clouds. Then those condense to form water droplets, and when enough droplets combine, they fall out of the clouds in the form of rain.
2. What is the comparison between evaporation and condensation?
Evaporation is a process by which water transforms into water vapour. Condensation is the opposite process by which water vapour converts into tiny water droplets.
4. Why is the water cycle important?
The water cycle definition has a huge influence on understanding the global climate. It is also an inherent part of other biogeochemical cycles. It influences all life processes on Earth either directly or indirectly.
5. What is the difference between a cloud particle and a precipitation particle?
The most important difference between precipitation and a cloud fragment is its size. An average drop of rain has a weight equal to nearly one million cloud droplets. Due to their large size, precipitation particles have remarkable falling speeds and are able to tolerate the fall from the cloud to the ground.