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Evapotranspiration (ET) refers to the combined processes which move water from the Earth's surface (open water and ice surfaces, bare soil and vegetation) into the atmosphere. [ 2 ] : 2908 It covers both water evaporation (movement of water to the air directly from soil, canopies , and water bodies) and transpiration (evaporation that occurs ...
It is a steel container 1.83 m (6 ft) on a side and 0.61 m (2 ft) deep, sunk into the ground with an above-ground rim of 7.6–10 centimetres (3.0–3.9 in) and is painted black internally. Its evaporation rate is lower than the Class A pan and conversion factors must be used. [8]
The Standardized Precipitation Evapotranspiration Index (SPEI) is a multiscalar drought index based on climatic data. It was developed by Vicente-Serrano et al. (2010) at the Institute Pirenaico de Ecologia in Zaragoza, Spain . [ 1 ]
Monthly estimated potential evapotranspiration and measured pan evaporation for two locations in Hawaii, Hilo and Pahala. Potential evapotranspiration is usually measured indirectly, from other climatic factors, but also depends on the surface type, such as free water (for lakes and oceans), the soil type for bare soil, and also the density and diversity of vegetation.
Two major factors influence the rate of water flow from the soil to the roots: the hydraulic conductivity of the soil and the magnitude of the pressure gradient through the soil. Both of these factors influence the rate of bulk flow of water moving from the roots to the stomatal pores in the leaves via the xylem. [7]
A WRS, such as a river, an aquifer or a lake, must obey water balance. For example, the volume of water that goes into an aquifer must be equal to the amount that leaves it plus its change in storage. Under various drivers, such as, climate change, population increase, and bad management, water storage of many WRS is decreasing, say per decade ...
The water cycle is essential to life on Earth and plays a large role in the global climate system and ocean circulation. The warming of our planet is expected to be accompanied by changes in the water cycle for various reasons. [3] For example, a warmer atmosphere can contain more water vapor which has effects on evaporation and rainfall.
The only note on this method is one must be wise about which variables to use and which to omit, for doubles can easily be encountered. An easy example of double counting variables is when the evaporation, E, and the transpiration, T, are placed in the equation as well as the evapotranspiration, ET. ET has included in it T as well as a portion ...