William O. Pruitt

Chapter 8. Water Requirements

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.