Multi-objective and multi-source irrigation area based on multi-scenario analysis of complex planting structure

Under the combined influence of global climate change and economic and social development, the contradiction between supply and demand of water resources has become increasingly prominent, and agricultural water use is facing serious challenges. Reasonable adjustment of planting structure and optimal allocation of agricultural water resources are the key ways to ensure regional agricultural water demand. In order to improve the contradiction between supply and demand of agricultural water in irrigation areas and scientifically optimize the allocation of water resources in irrigation areas, this study took the Zhangfu River irrigation area in Handan City, Hebei Province as the research object, the minimum water shortage of agricultural irrigation and the maximum economic benefits of crops as the objective functions, and took into account the ecological security constraints of the irrigation area. A multi-objective and multi-water source optimal allocation model based on planting structure optimization was constructed. Eight different planting structure optimization scenarios were set for cropping system, crop type, planting system and irrigation method. The model was solved by the self-improved elite strategy and co-genetic algorithm (NSGAⅡ-S) to obtain the optimal allocation of water resources under different scenarios. The results showed that after the application of the model to optimize the planting structure, the reservoir water and the river water can be supplied to the downstream units of the private partition. The groundwater exploitation of each calculation unit was significantly reduced, and the water distribution between the calculation units of the private partition was obvious. The total water distribution was higher than that of the Fuyang River partition. The proportion of reservoir water distribution and groundwater water distribution in different scenarios was relatively stable and was used in each month. The water distribution of the Yellow River was mainly concentrated in the summer of the peak period of water use, and the use of reservoir water and river water was more in winter. Appropriate reduction mainly depended on the planting area of winter wheat irrigated by groundwater extraction. Changing irrigated agriculture to rain-fed agriculture greatly reduced the amount of groundwater and increased the economic benefits of irrigation areas. The best planting structure optimization scheme was CS₄. In this scheme, the planting area of winter wheat was reduced by 17.10%, the groundwater exploitation was reduced by 16.42%, and the economic benefit of the irrigation area was increased by 26.41%. While ensuring the minimum total water distribution, it had higher economic benefits. The multi-objective and multi-water source optimal allocation model of the irrigation area constructed in this study comprehensively considered the agricultural irrigation water consumption and economic benefits of the irrigation area, clarified the water supply relationship of each sub-unit, and explored the planting structure of the irrigation area and the optimal allocation of water resources under the goal of groundwater exploitation. The new model gave full play to the rational allocation of water resources in the irrigation area and provided a decision-making basis for the planning and management of water resources in the irrigation area. The research results are helpful to give full play to the water source advantages of the irrigation area, provide an example for the optimal allocation of water resources in similar areas, and provide theoretical basis for ensuring food security and sustainable development of agricultural economy.