Effective efficiency in water resources management using efficiency elasticity index

Effective efficiency (EE) is a water use performance indicator of a system, integrating net evapotranspiration, volumes of water in and out of the system (including reused water) and their qualities. In order to analyse the nature of management and its options in promoting efficiencies, an efficiency elasticity index (EEI) is developed using EE. The maximum value of EEI for a given net evapotranspiration sets a threshold value for EE under which the management of the system should be improved. This makes it possible to evaluate how good the management of a system is and allows the decision makers to analyse efficiency targets using a graphical approach (assuming that interventions have the same costs). Hypothetical examples and real irrigation cases from United States and Egypt show the practical utility of EE and the methodology developed through the use of EEI. It is also shown that classical efficiency should be used with caution.