Sustainable management in irrigation water distribution system under climate change: Process-driven optimization modelling considering water-food-energy-environment synergies

The scarcity of water resources, severe pollution and climate change necessitate the sustainable and optimized allocation of irrigation water resources. Agricultural irrigation is profoundly influenced by dynamic environmental conditions and affects crop photosynthesis, respiration and energy utilization, thereby significantly influencing crop yield and agricultural non-point source pollution. To address this issue, this paper presents a process-driven modeling approach for achieving sustainable optimal allocation of irrigation water resources based on the water-food-energy-environment (WFEE) nexus in response to climate change. The model is capable of quantifying the inherent mechanisms of irrigation water and yield, as well as the formation of non-point source pollution, and optimizing irrigation water considering changing environment. This method was tested and implemented in Changgang Irrigation District in Heilongjiang Province, China. The results indicate that: (1) there exists a significant positive and negative nonlinear correlation between the amount of irrigation water and crop photosynthesis as well as soil respiration, which directly impacts crop yield. Specifically, when the optimized volume of irrigation water is increased by 5 %, crop respiration decreases by 1.26 %, the photosynthetic rate increases by 0.85%, actual evapotranspiration increases by 0.73 %, and yield increases by 1.72 %. (2) By optimizing the allocation of agricultural water resources, the harmony between the economy, energy, environment, and resource utilization efficiency can be improved by 33.35%. (3) The distribution of irrigation water significantly responds to changes in climate factors. Under other unchanged conditions, when potential evapotranspiration increases, it will promote a significant increase in irrigation water, while an increase in rainfall during growth period will reduce the demand for irrigation water. The constructed model finely regulates agricultural irrigation water resources from a process mechanism perspective, and mitigates non-point source pollution, thus realizing sustainable utilization of such resources.