Evolution characteristics and influencing factors of water footprint of food crop production in the middle and lower reaches of the Yangtze River during 1989-2018.

The middle and lower reaches of the Yangtze River is an important grain production base in China, which plays an important role in maintaining national food security. Based on the agricultural production and meteo-rological data from 1989 to 2018, we comprehensively analyzed water footprint of three major food crops (rice, wheat, and maize) production in six provinces in the middle and lower reaches of the Yangtze River. The results showed that rice in the six provinces always ranked first in terms of yield per unit area, sown area, and total yield. Water footprint of rice production was also the highest, with an average of 588.6×10⁸ m³, while the water footprint of wheat and maize production was relatively low. In terms of water footprint of per unit yield, wheat had the highest water footprint of per unit yield, with an average of 8.8 m³·kg^-1, followed by maize and rice. In terms of water footprint of per unit area, the three crops showed similar performance, and the overall trend showed a downward trend. The total water footprint of the three crops decreased significantly, from 1000.79×10⁸ m³ in 1989 to 281.34×10⁸ m³ in 2018. Among them, the water footprint of crop production in Zhejiang, Hubei, and Anhui was lower. From the perspective of the composition of water footprint, blue water footprint accounted for the highest proportion, followed by green water and gray water, with the value of 50.1%, 39.6%, and 10.3% respectively. The model analysis showed that economic effect, technical effect, grain planting area, and daily average sunshine hours had a greater impact on water footprint of crop production. Among them, the technical effect had a negative impact and other factors were positive. We proposed strategies to reduce water footprint of production, including the promotion of water-saving irrigation technology, the construction of water conservancy projects, the improvement of fertilizer and pesticide use efficiency, the planting of high water use efficiency varieties and the formulation of relevant policies. Our results revealed the change trend of water footprint of grain crop production in the middle and lower reaches of the Yangtze River, and identified the key factors affecting water footprint, which would provide a scientific basis for the development of water-saving agricultural technologies and water resources management strategies.