Optimization of Freshwater–Saline Water Resource Mixing Irrigation Under Multiple Constraints

The unique anticline geological structure in the central region of Yingjisha County results in significant spatial variations in groundwater quality. The study shows that the recoverable groundwater reserves account for 13.5% of the natural groundwater supply, and the development potential is considerable. Therefore, this study conducts an in-depth analysis of the spatial distribution characteristics of multiple water sources, integrates agricultural cropping patterns, and delineates irrigation districts accordingly. A water quality-based optimized allocation model for water resources is established. After optimization, the total irrigation water demand is reduced from 3685.8 million m3 to 3229.9 million m3, with total groundwater extraction controlled at 694.0 million m3. The total water shortage rate is 12%, and the decline in groundwater levels has been effectively controlled. Additionally, 116.4 million m3 of saline water is utilized, achieving an 83% utilization rate, which accounts for 16.8% of total groundwater extraction. Consequently, the utilization rate of freshwater decreases from 127% to 64%, while the overall water supply reliability reaches 87.6%. The sequence of water supply and consumption in the model remains consistent with the existing supply structure, demonstrating the rationality of the model parameter settings. This study proposes an optimal freshwater–saline water allocation model, which mixes saline water with reservoir water for dilution and subsequent agricultural irrigation. The approach aims to exploit the potential of saline groundwater and enhance the utilization efficiency of groundwater systems, thereby providing an innovative solution to alleviate water supply-demand conflicts in arid regions.