Comment: Efficient irrigation; inefficient communication; flawed recommendations C. Perry (2007) Irrigation and Drainage56: 367–378

It seems that the paper (essentially an irrigation paper) has the following basic objectives: a) Evidence based demonstration of the inadequacy of efficiency to promote flawless recommendations and, as such, the need to abandon ''efficiency'' altogether.b) Conceptual based demonstration of ''fractions'' and their adoption by ICID for further use. STRUCTUREThe general structure of the paper does not focus on the objectives mentioned above.For example one section entitled ''The Irrigation Approach to Accounting'' deals with a vast array of issues such as: Classical Efficiency (CE, also irrigation efficiency), Effective Efficiency (EE), basin efficiency, water saving, fractions, European Water Framework Directive (WFD), water productivity, evidences, etc.Consequently, the treatment of these issues is cursory at best.A few of these points are discussed below:A. The paper puts CE into spotlight by making it clear through various evidences that it does not work and gives flawed recommendations.This is indeed true (for a formal rejection of CE, both through equations and through examples, one can refer to the upcoming paper by Haie and Keller).However because of the fallacy of one type of efficiency, the paper is making a generalization for all types of efficiencies.Also, except for CE, the paper does not make the definition of the efficiencies clear, such as ''basin efficiency'' or the efficiency that ''frequently exceeds 100%''.It is generally assumed that the evidences put forth by the paper as problematic have indeed used CE.B. The paper mentions two weaknesses about EE but without any evidence, contrary to the objective of the paper.These are:a) ''nature of the pollutant'': since this is an irrigation paper and salt is a major quality problem, EE is well posed to solve it with the current knowledge (as acknowledged by the paper).This by itself, and the fact that EE includes in its formulation irrigation return flow, makes this type of efficiency an indicator that promotes sustainability and worthy of serious consideration.For a combination of quality problems, an index (such as chemical status in WFD, water quality index in Kaurish and Younos, 2007, etc.) should be used for EE calculations.On the other hand, if quality is to be analyzed separately, a point that the paper insists, a quantity only version of EE (Haie and Keller) that includes return flow will solve all the problems brought about in the