The Principles and Conditions of Using Irrigation Efficiency Index When Managing Water for Agriculture

Irrigation Efficiency (IE) is one of the indexes defining the efficient use of water in agriculture. Unfortunately still nowadays it is widely used for water management policies in agriculture without enough attention to its concept, usage, and the conditions which it should be used. Hence great emphasis and investments is on its measurement in the country. Consequently great investment on development of pressurized irrigation system assuming that it will save water through increase in irrigation efficiency by widely use of such systems! IE is a local term. It indicates water application situation in crop root zoon of a specific field. Therefore, it does not deal with the losses which may be useable in another farm in downstream or losses which may percolate to the groundwater. IE is a good index for comparison of the different irrigation systems used in the fields? But it dose not implies the water productivity (WP), because it does not consider crop productions variables. In crop production, other variables, e.g. Agronomic, climate, soil, and other agronomic management practices are involved, which this index did not consider. Considering the severe water crisis nowadays, the water management issues could not be solved only through field scale assesments. But the importance of a more comprehensive vision and attention to water in a broader scale (i.e., in Basin and National levels) is more prominent and essential. In other words it is necessary to shift from local scale of field scale to higher level. Lack of enough attention to this point has caused different problems, ambitions, and even diverse results in solving water problems in the Iran country. It should be stated that the traditional classic view of IE is not eligible in solving large scale water management issues nowadays, despite it still has merits for determining of the farmers functioning for an efficient irrigation event. Water accounting now is a prominent view on solving water management issues of the basin and national levels. Therefore we should have a neoclassic view on IE. There are considerable return flows in the basin level which comes from these losses at the field level. In recent years and in regard to new vision on water management, new terms and concepts have come to the existence, e.g., beneficial and non-beneficial, recoverable flows and non-recoverable flows. Overall, when it is intended to invest on IE improvement and water saving, even with this classical view, it is necessary to invest on the factors causing decrease of real water losses than apparent losses. This will be an intelligent and efficient investment.