Night irrigation reduction for water saving in medium-sized systems

In many medium-sized irrigation systems water is wasted during the night because demand is low and supply is not reduced accordingly. A hydrodynamic model was applied, using MIKE II as a software tool, to simulate abrupt discharge changes and their travel times along small irrigation canals. Filling and emptying of the canal were also analyzed. The model was calibrated with data of a field experiment that included startup, positive, and negative surges. A technique was developed to take into account the considerable water losses in the canal. Performance indicators efficiency, adequacy, equity, and dependability, proposed by Molden and Gates in 1990, were redefined using the concept of usefully delivered discharge. The newly defined indicators were consequently used to find the gate operation scenario that meets optimally the target day and night discharge. It was found that it is feasible to implement night delivery reduction. The calibrated model was used to develop guidelines for the operation of the canal with daily flow variation, resulting in considerable water savings during the night.