In engineering, efficiency is a gen

In engineering, efficiency is a general measurement concept used to determine how well a particular system is functioning. It is defined in terms of the desired output as a fraction of the measured inputs. Early irrigation engineers (4) were interested in determining what proportion of the irrigation water applied to a field ended up in the root zone of the crop. They used the term "irrigation efficiency" to describe the result of water application on a single field. In their interpretation, the water that ran off the field and the water that seeped below the root zone was lost. Water quality was not a consideration and downstream reuse of the water that was not stored in the root zone was not considered. As far as the field in question was concerned, the water not stored was lost. If a farmer could store a larger proportion of his applied water in theroot zone of his farm, his irrigation efficiency was higher. It is now well known that runoff from one farm often becomes the source of water for another farm and that the water is not physically lost as long as it remains in liquid form. The only water truly "lost" by an irrigation system is that which goes directly into crop production, regardless of the amount applied or the efficiency of application. Water that is not vaporized by direct evaporation and by the evapotranspiration process in the natural