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Levels of evapotranspiration in a given area are primarily controlled by three factors: [10] Firstly, the amount of water present. Secondly, the amount of energy present in the air and soil (e.g. heat, measured by the global surface temperature ); and thirdly the ability of the atmosphere to take up water ( humidity ).
In an enclosed environment, a liquid will evaporate until the surrounding air is saturated. Evaporation is an essential part of the water cycle . The sun (solar energy) drives evaporation of water from oceans , lakes, moisture in the soil, and other sources of water.
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]
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.
The Penman-Monteith equation approximates net evapotranspiration (ET) from meteorological data as a replacement for direct measurement of evapotranspiration. The equation is widely used, and was derived by the United Nations Food and Agriculture Organization for modeling reference evapotranspiration ET 0 .
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]
Crop coefficients are properties of plants used in predicting evapotranspiration (ET). The most basic crop coefficient, K c, is simply the ratio of ET observed for the crop studied over that observed for the well calibrated reference crop under the same conditions.
Operation and design of evapotranspiration waste disposal systems: Author: Hasfurther, Victor R: Software used: Internet Archive: Conversion program: Recoded by LuraDocument PDF v2.68: Encrypted: no: Page size: 552 x 724 pts; 530 x 724 pts; 548 x 729 pts; 552 x 731 pts; Version of PDF format: 1.5