Perspective of agricultural water safety under combined future changes in crop water requirements and climate conditions in China

Agricultural water safety is foreseen to have more turmoil in the future, and this concern will be driven by agricultural production growth, population growth, and socioeconomic developments accompanied by climatic changes. Our study aimed to develop an index for regional water scarcity evaluation and quantify the present and future agricultural water stress in China. Changes in crop evapotranspiration (ETc) during the baseline period (1990-2015) and future periods (2020-2039, 2040-2059, 2060-2079, and 2080-2099) under two different scenarios (RCPs, 4.5 and 8.5) were introduced. Moreover, we evaluated the precipitation cultivation dependability index (PCDI) and agricultural water stress index (AWSI) in China from 1990 to 2099. A significant increase in ETc between the baseline and future projections will be more than 20 Gm(3) in the south and southeastern provinces. The months from April to August shared a proportion that exceeded 70% of the yearly ETc. The PCDI during the autumn season was highest (full) and will increase significantly during all future scenarios, except during 2080-2099 of RCP8.5, which will record a non-significant reduction in the PCDI compared with the baseline. All provinces will have a significant increase in the PDCI under future projections except in 2080-2099 (RCP8.5) compared with the baseline. The AWSI over China recorded medium to high water stress (0.84) for the baseline, but it will increase significantly to very high-water stress (> 1) in all future scenarios. These results suggest that China should guarantee the sustainable use of agricultural water resources by reducing its crop water footprint and minimizing the influence of drought under a warming climate, e.g., via forest plantations.