Evaporation And Its Role In The Water Cycle

Evaporation is the vaporization of a liquid into the gaseous state, and an integral component of the hydrological cycle.

Evaporation Defined

Evaporation is the process by which water converts from liquid to vapor form. The conversion to vapor ensures water is transferred from land and water bodies into the atmosphere, according to Michigan Technological University. When water is heated, it evaporates after the molecules move and vibrate so quickly, they escape into the atmosphere as water vapor molecules. Evaporation is one of two forms of vaporization, the other being boiling. For evaporation to occur, energy is required as it proceeds faster at higher temperature, and higher flow rates between the gaseous and liquid phase, and, in liquids, in cases of lower surface tension on water. Surface tension is the elastic tendency of a fluid that allows insects to float on water and have tension that allows for bubbles formation.

Evaporation's Integral Role

Water on the planet is constantly getting recycled in what’s called the water cycle (or hydrological cycle), and evaporation is vital in that. Water from oceans, rivers, swamps, lakes, plants and even humans is converted to vapor in the water cycle, according to NASA’s Center for Educational Technologies. The sun provides solar energy that powers the evaporation process. The heat soaks up the moisture from soil in gardens, farms, oceans, and lakes. As a result, the water levels decrease due to exposure of heat from the sun, according to National Geographic. Though water levels in water bodies appear to decrease due to the sun’s heat, the escaped molecules don’t disappear. They stay in the atmosphere, and affect humidity and influence the moisture amounts in the air. Regions with high temperatures and large water bodies are humid due to water evaporating and remaining in the air as vapor. Evaporation also helps in cloud formation. Afterwards the clouds release the moisture as precipitation. In plants, transpiration is water evaporation from plants. In transpiration, water or minerals are carried from the roots, to the underside pores on the leaves in a plant. From these pores water evaporates into the atmosphere and that helps keep a plant cool, during hot weathers.

Factors Affecting Evaporation

Clogged or polluted air hinders the amount of air required to cause evaporation. Also when humidity is 100 percent, and the air is saturated with water, that also hinders evaporation. When air pressure is also high on the surface of a water body, evaporation is hindered. This air pressure pushes down on the water, hindering its escape into the atmosphere as vapor. Such an occurrence is likely in storms that result in high pressure that hinders evaporation according to National Geographic. Temperature levels also affect how fast evaporation occurs, as boiling water evaporates faster as steam than warm water. The wind also carries evaporated water, thereby influencing humidity levels across regions.

Utilization of Evaporation

For thousands of years, evaporation has been utilized in livelihoods. Table salt is obtained from saline sea water through evaporation, in evaporation ponds. The Dead Sea in the Middle East which has no river outlet relies on evaporation for water to leave this lake. Evaporation at the Dead Sea also aids in magnesium, potash and bromine minerals extraction according to the U.S. Geological Survey. Around 80 percent of all water evaporation comes from the oceans and the rest from inland water and vegetation.

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