Multi-objective optimization of water-saving irrigation in groundwater over-exploitation area of the North China Plain under joint control of water level, water volume, and crop yield

To explore water-saving irrigation strategies for crops in the North China Plain under the joint control of groundwater level, irrigation water use, and crop yield, a multi-objective optimization simulation framework for water-saving irrigation, named irrigmoo, was developed. This framework integrates a groundwater numerical model based on FloPy, a crop water requirement model, and the NSGA-Ⅱ multi-objective optimization model. Using Cangzhou City in the central-eastern part of the North China Plain as the study area, field data were collected to calibrate the groundwater numerical model, construct the crop water requirement model, and configure the NSGA-Ⅱ multi-objective optimization model. A set of Pareto non-dominated solutions for irrigation schemes under limited water conditions was obtained, and representative groundwater extraction reduction and alternative water source substitution schemes were selected. The results indicate that reducing the proportion of groundwater in irrigation water by 42. 13% and replacing 15. 28% of groundwater with alternative water sources could lead to a 2. 36 m rise in deep groundwater levels, a 26. 86% reduction in irrigation water use, and a 3. 94% decrease in winter wheat yield. If groundwater extraction for irrigation is completely banned and 37% of the current extraction is replaced with alternative water sources, the deep groundwater level could rise by 8. 95 m, irrigation water use could be reduced by 62. 87%, and winter wheat yield would be decreased by 12. 7%, while still remaining within yield constraints.