Multi-Scenario Optimal Allocation of Agricultural Water Resources in a Canal–Well Irrigation District Based on Irrigation Priority

Water scarcity and uneven spatiotemporal water distribution trigger severe supply–demand conflicts in arid irrigation districts, making rational water allocation critical to safeguarding food security and improving water use efficiency. This study selects the Jiamu Town Irrigation District in the Tailan River Basin of Xinjiang as the research case. By incorporating hydrological year types, ten-day runoff sequences, exploitable groundwater volumes, and crop irrigation priorities, a multi-objective optimization model was constructed. The two optimization objectives are minimizing total groundwater extraction and the weighted irrigation water deficit. Herein the weighted deficit equals the physical water shortage of each crop-growth-stage irrigation task multiplied by its priority coefficient, which drives the optimization iteration to prioritize water-shortage relief for high-priority irrigation demands. The key findings are summarized as follows: (1) Relative to the actual water consumption in 2023, the optimized scheme raises surface water utilization efficiency from 73.1% to 81.3% and cuts groundwater exploitation by 2.05 million m3 (from 11.09 million m3 to 9.04 milion m3). (2) Under a fixed crop planting structure, irrigation water demands across all ten-day intervals can be largely satisfied. (3) Crop irrigation satisfaction rates exceed 97% across all hydrological scenarios, with water deficits predominantly occurring in drip-irrigated pepper and orchards. The proposed optimal allocation model can effectively curb groundwater overexploitation and minimized water use conflicts among diverse crops and their critical growth stages, offering technical references for refined water resource management in arid canal–well irrigation districts.