What is the water cycle?
The water cycle, also known as the hydrologic or hydrological cycle is the manner of recycling the water. As the wheel of the cycle rotates in a round direction similarly water flows on, above and under the surface of the Earth. The water cycle includes the non-stop movement of water from the earth to the atmosphere and then back to the earth. The mass of water on earth remains almost constant but its form and place keep on changing. The water levels from the atmosphere, glaciers, oceans, rivers, lakes, under the surface of the earth, keep on changing due to climatic variations.
The physical processes of evaporation, condensation, precipitation, infiltration, sublimation, surface runoff and subsurface drift make the water float in a circular motion.
Evaporation is the process by which water changes from liquid form to gas or vapors. Due to humidity, wind speed, sun rays, and temperature, some of the molecules of water attain sufficient kinetic energy to eject themselves from the water surface in the atmosphere in form of gas or vapors.
The primary source of water vapors is the ocean but evaporation also occurs in soils, snow, and ice.
Evaporation from snow and ice, the direct conversion from solid to vapor, is known as sublimation.
Transpiration is the evaporation of water through minute pores, or stomata, in the leaves of plants.
After Evaporation, condensation occurs. Condensation is just the opposite of evaporation. Condensation is the manner through which water vapor within the air is modified into liquid water. The water vapors in the ecosystem condense to form clouds. The clouds formed by condensation are a complicated and critical element of the Earth’s ecosystem. Clouds adjust the flow of radiant energy into and out of Earth’s climate system. They regulate the Earth’s climate by reflecting incoming solar radiation (heat) back to space and outgoing radiation (terrestrial) from the Earth’s surface. Often at night, clouds act as a “blanket,” keeping a portion of the day’s heat next to the surface. Changing cloud patterns transform the Earth’s energy balance, and, in turn, temperatures on the Earth’s surface.
When clouds become heavy enough and air cannot hold that much amount of water, precipitation happens.
It is a process where all liquid and solid water particles that fall from clouds reach the ground. These particles include drizzle, rain, snow, snow pellets, sleet, ice crystals, and hail.
If a cloud is colder, like it would be at higher altitudes, the water droplets may freeze to form ice. These ice crystals then fall to the Earth as snow, hail, or rain, depending on the temperature within the cloud and at the Earth’s surface. Most rain actually begins as snow high in the clouds. As the snowflakes fall through warmer air, they become raindrops.
Particles of dust or smoke in the atmosphere are essential for precipitation. These particles, called “condensation nuclei,” provide a surface for water vapor to condense upon. This helps water droplets gather together and become large enough to fall to the Earth.
Through this process, Earth gets its water back in the form of freshwater. However, in some cases, pollutants in the atmosphere can contaminate water droplets before they fall to the Earth. The precipitation that results from this is called acid rain. Acid rain does not harm humans directly, but it can make lakes and streams more acidic. This harms aquatic ecosystems because plants and animals often cannot adapt to the acidity.
Water falling from clouds not only goes in water bodies but also goes deep into the ground or is soaked up into the ground. This process is called percolation. Water flows downward under the layers of the soil.