The irrigation modules distinguishes 3 different types of efficiencies, and each has a distinct location where it applies:
Application efficiency is a function of the irrigation method. For each irrigation method:
a fixed application efficiency is given. These figures are stored in the ORACLE data base and can not be modified by the user. The only way to modify the mean application efficiency Eff_m is by modifying the portion (percentage) of irrigation methods.
System efficiency has to be manually set by the user. A value of 80% is set as default. This value is lower in case of wells, and is usually higher if water is diverted through an open channel from a river.
Efficiencies are expressed in percent. In case of 64% mean application efficiency, the required water at farm gate is
(NIR * area)/0.64
The same formula applies to the system efficiency. In case of 80% system efficiency, the total amount of water required at the distribution point is
((NIR * area) / 0.64)/0.80.