Efficient water-saving irrigation based on regional irrigation schedule optimisation

Shortage of agricultural water resources and low agricultural water use efficiency (WUE, which is the economic output per unit of water, and is divided into WUEEI, the ratio of yield to evapotranspiration and WUEET, the ratio of yield to irrigation volume) have become important factors that restrict agricultural development in northwest China. In the middle oasis of the Heihe River Basin (HRB), the major causes for loss of agricultural water and low irrigation efficiency are large irrigation quotas, the uneven spatial distribution of agricultural water resources and unreasonable irrigation schedules. A full understanding of the spatial distribution of agricultural water consumption and water productivity in the middle oasis of HRB is a prerequisite for improving agricultural WUE and ensuring food production security under the premise of existing agricultural water supply. In this study, by using the AquaCrop-RS model, the spatial distribution of water consumption and water productivity in the middle oasis of HRB was analyzed under the current irrigation schedules. Simulations were conducted to study the deficit irrigation scenarios in this region, preliminarily arriving at appropriate irrigation quotas for different irrigation districts. A multi-objective optimization model and the genetic algorithm NSGA-II with an elitist strategy were used in optimizing the irrigation schedule for each irrigation unit. Irrigation schedules that meet the highest yield and the highest WUE ET for the middle oasis were obtained. Results show that the irrigation quota of corn in the middle oasis after irrigation schedule optimization is reduced by 0-657 mm under different irrigation schedules, WUEET is increased by 4.13%-5.13% and WUEI rises by 69%-91%, thereby preliminarily achieving the water-saving and high-yield goals for corn in the middle oasis.