American Society of Agricultural and Biological Engineers



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Chapter 8. Water Requirements

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org

Citation:   No Citation available.
Authors:   Richard G. Allen, James L. Wright, William O. Pruitt, Luis S. Pereira, Marvin E. Jensen
Keywords:   Evapotranspiration, Evaporation, Penman, Penman-Monteith, Irrigation requirement, Effective precipitation, Crop coefficient, Landscape coefficient.

Evapotranspiration (ET) calculation guidelines are based on the crop coefficient-reference evapotranspiration method (Kc ETref). Equations for the ASCE-EWRI standardized Penman-Monteith method are provided for grass and alfalfa references, where the grass reference standardization follows the FAO Penman-Monteith procedure. Linearized FAO-style crop coefficients from FAO-56 and curvilinear coefficients from Wright are presented as both mean and as dual (basal) crop coefficients. ET coefficients for landscape utilize a decoupled procedure similar to that summarized by the Irrigation Association Water Management Committee. Guidelines for calculating irrigation water requirements and peak system design rates are described.

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