Unimodal Surface Irrigation Efficiency

Abstract

A new concept in surface irrigation efficiency, termed deficit/excess efficiency, is presented; it has potential for use as an objective function for optimization purposes in the design and operation of on‐farm irrigation systems. This concept, which yields a unimodal function of the volume of water applied, combines selected characteristics of application efficiency, storage efficiency, and Christiansen's uniformity coefficient. Under normal conditions, small applications of water produce high application efficiency, but a low uniformity coefficient and storage efficiency; conversely, large applications produce a high uniformity coefficient and storage efficiency, but low application efficiency. Thus, none of these latter terms are unimodal functions of the volume of water applied. The proposed deficit/excess efficiency can be modified according to management criteria to assign a benefit or penalty to the amount of runoff, deep percolation, and under irrigation in the irrigated field. Algebraic relationships between deficit/excess efficiency and other efficiency terms are presented. A field example comparing this efficiency term with others is provided.