Click on “Download PDF” for the PDF version or on the title for the HTML version.

If you are not an ASABE member or if your employer has not arranged for access to the full-text, Click here for options.

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.