Water Footprint-Based Optimization of Crop Planting Structure for Sustainable Agricultural Water Management in Hunan Province, China

Given the mounting pressure on agricultural water resources in China, which poses a threat to agricultural production safety, this study focuses on Hunan Province and analyzes five major crops over the period 2012–2022. Using a water footprint (WF) accounting method, it quantifies grey water from non-point source pollution and optimizes planting structures under 5%, 10%, and 15% water-saving scenarios. The results indicate that crop water footprints per unit mass follow the descending order: oilseeds, leaf tobacco, rice, fruits, and vegetables. Regarding water footprint components, green water footprint accounts for the largest proportion, playing a dominant role in crop water use, followed by grey water footprint. Blue water footprint and irrigation losses contribute the least. After optimization, under the 5% and 10% water-saving scenarios, the cultivated areas for rice, oilseeds, and leaf tobacco decreased compared to 2021, while those for vegetables and fruits increased. Under the 15% water-saving scenario, all crop planting areas were reduced relative to 2021. The optimized crop planting structure enhanced water use efficiency by 0.35%, 0.58% and 0.77%, respectively, under water-saving scenarios of 5%, 10% and 15%. These results provide a scientific basis for sustainable agricultural water management in Hunan Province.