Evapotranspiration

Evapotranspiration

Subject :Geography

Section: Physical geography

Concept :

• Evapotranspiration is the combined process of evaporation and transpiration that leads to the loss of water from the Earth’s surface to the atmosphere.
• Term ‘Evapotranspiration’ was coined and later defined by climatologist Charles Warren Thornthwaite in 1944.
• Evaporation refers to the conversion of liquid water to water vapour, mainly from open water bodies, whereas transpiration is the release of water vapour by plants through their leaves.
• Several factors influence the rate of evapotranspiration, including temperature, humidity, wind speed, solar radiation, and the availability of water in the soil.
• Higher temperatures, low humidity, and strong winds increase evapotranspiration, while cloudy conditions and limited soil moisture reduce the process.
• Various methods are used to measure evapotranspiration. These include the use of evaporation pans, lysimeters, and meteorological instruments such as atmometers and eddy covariance systems.
• These techniques help researchers and policymakers estimate water loss from different landscapes, including agricultural fields, forests, and urban areas.
• Evapotranspiration plays a crucial role in agricultural water management. By understanding the water requirements of crops and estimating evapotranspiration rates, farmers can optimise irrigation scheduling to ensure efficient water use.
• This knowledge helps prevent over-irrigation, which can lead to water wastage and environmental issues, and under-irrigation, which can reduce crop productivity.
• Evapotranspiration is an essential component of the Earth’s water cycle and has significant environmental implications.
• It affects regional and global climate patterns by regulating the exchange of moisture between the land surface and the atmosphere.
• Changes in evapotranspiration rates due to land-use changes, deforestation, or climate change can impact local and regional water availability, precipitation patterns, and overall ecosystem health.
• Understanding evapotranspiration is vital for effective water resource management and sustainable development.

Hydrological Cycle

• The hydrological cycle is also known as Water Cycle.
• It is the circulation of water in various forms – Liquid, Solid, and Gaseous.
• Water moves in different realms like ocean, river, glaciers etc.

Distribution of water on surface of the earth

• About 71% of the water of the earth is found in the oceans.
• The remaining is freshwater in glaciers and ice caps, groundwater, lakes, etc.
• About 59% of the water on the land evaporates and returns back to the atmosphere.

Hydrological cycle Process

• The movement of water takes place through various processes.
• Evaporation, Condensation, Precipitation, Runoff, Infiltration, Transpiration, etc.

Evaporation and Transpiration

• The Water cycle begins with the evaporation of water.
• It is the process of water transfer from surface of water bodies into the atmosphere.
• Water vapours also get discharged from plant leaves through transpiration.
• Condensation
• The water vapours rise up and get cooled to liquid water droplets in the air, forming fog and clouds.
• Precipitation
• The condensed water vapour falls on the Earth is known as Precipitation.
• The water also falls in form of hail, snow, sleet depending on the temperature.
• Runoff and Infiltration
• Runoff is the flow of water in rivers, streams, and lakes.
• Infiltration is the process through which rainwater is absorbed by the surface of earth.