Identifying a new paradigm for assessing irrigation system performance

There are many definitions of irrigation system efficiency that are applied over a range of scales. Many traditional definitions considered only the water diverted as the water volume of concern. Considering also the water consumed in defining effective irrigation efficiency is a shift from the classical definition of system efficiency. In this paper, equations are derived for calculating the following system performance measures: the irrigation consumptive use coefficient, irrigation system efficiency, irrigation water and soil salinities, relative yield, and productivity of consumed, diverted and beneficially used water. The expressions are based on quite general assumptions and are valid for systems with a single water source and layouts composed of (or simplified to) irrigation units arranged in a row. The aim of these expressions is to illustrate how system performance is affected by the reuse of water which depends on the system’s hydraulic connections and the irrigation unit performance. Illustrations of the model are provided for systems in series and in parallel. Testing and refinement by removing some of the general assumptions underlying the model will be needed to develop practical applications that can be more confidently applied for comparison and improvement of irrigation systems.