The effect of climate change on the water and food nexus in China

A country level food security approach called PODIUMSim model was applied in this paper to analyse the likely food surplus/deficit in China in the years 2030 and 2050 based on population growth and irrigation area development scenarios. PODIUMSim is an interactive policy planning and scenario analysis tool, which explores the trade-offs and future demands on water resources at a national scale. Changes in precipitation and evapotranspiration estimated from climate models are used to represent climate change. A decision support tool for stochastic analysis called @RISK was used to perform stochastic analysis on future water availability and water demand. Without climate change the results indicate that total grain demand in China would increase from 427 million tons in 2000 to 609 million tons by 2030 and 714 million tons by 2050 while the total grain production was 400 million tons in 2000 and would increase to 521 million tons and 629 million tons in 2030 and 2050, respectively. There was a 27 million ton grain deficit in the year 2000 and there would be an 88 million ton and 85 million ton grain deficit in 2030 and 2050, respectively, under medium population growth and irrigation area development scenarios. To meet the total food demand in 2030 and 2050 in the high population growth scenario, 107.8 and 104.7 million ha of gross irrigated area need to be reached respectively, which requires 48% and 73% of surface water and groundwater irrigation efficiencies in the year 2030 and 49% and 75% of surface water and groundwater irrigation efficiencies in the year 2050, subject to the constraint of irrigation water use being between 400 and 420 billion m3, as set by the Chinese government. Achieving these gains in both gross irrigated area and irrigation efficiency at the country levels is a formidable task, requiring further intensification of land and water use. To meet the total food, domestic and industrial demand, the total water production will have to increase from 564 billion m3 in 2000 to 600 and 615 billion m3 in 2030 and 2050, respectively. In addition, climate change will have significant impacts on future water availability and irrigation water demand. Under climate change (precipitation increased by 3% and evapotranspiration increased by 0.03 mm day−1) in 2030, the surface water availability would decrease from 951 billion m3 to 914 billion m3 and groundwater availability would decrease from 383 billion m3 to 378 billion m3. To cope with the impacts from climate change, some mitigation measures such as investing in drought resistant crops, expanding water storage schemes, and increasing irrigation water use efficiencies should be adopted.