4.4: Calculating ET

Irrigation Systems Management (AET 021) · LibreTexts

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    From LibreTexts, under CC BY-NC-ND 4.0, as the source states it; its equations are written in TeX, which the PDF shows typeset. This page at LibreTexts.

    Knowledge of plant water use rates is essential to manage irrigation systems accurately. Because measurement of ET is difficult and time consuming, equations have been developed to predict water use rates. These equations are based on weather factors, plant species, and stage of plant development and soil water status. The equations can estimate past water use and forecast future water use which are both essential in planning, designing, and scheduling irrigations. The simplest equation to predict plant water use is based on two factors:

    ET = Kc ETo

    where: ET = actual crop or plant ET rate,

    Kc = crop coefficient, and

    ETo = reference crop ET rate.

    Crop coefficients are used to describe the behavior of agricultural crops. The reference ET represents the amount of energy available for ET. This is expressed as the water use rate of a reference crop.

    4.4: Calculating ET is shared under a CC BY-NC-ND 4.0 license and was authored, remixed, and/or curated by LibreTexts.