Virtual Water Analysis And Suitability Evaluation Of Grain Trade In China

Grain is an important guarantee for meeting people’s needs,promoting economic development and maintaining lasting social stability.As an indispensable factor in grain production,water resources are unevenly distributed in space.There is a significant gap between the amount of water resources in the south and the north,and the main grain-producing areas tend to shift to the north,which further aggravates the shortage of water resources in the north.Although China is self-sufficient in grain rations,its overall grain self-sufficiency rate dropped to 83 percent in 2019.Therefore,as a country with 1.4 billion people,food security and water shortages need to be taken seriously.Due to the distance between main grain producing areas and main grain marketing areas in China,reasonable grain migration will not only realize food security,but also bring certain virtual water flow and corresponding associated effects.This study based on 2017 national provincial administrative region(except Hong Kong,Macao and Taiwan)food trade pattern,explore the provincial grain trade links,study with food transfer associated effect,quantitative grain migration impact the output area of water resources,to identify water resources unsustainable trade pattern of link.Construct the grain migration suitability evaluation index system,establish the suitability evaluation model,measure the support degree of each provincial administrative region to grain trade migration,identify the unreasonable migration state in trade,and establish the optimization model based on water resources sustainability and grain migration suitability to regulate the trade pattern.The main conclusions are as follows:(1)The present situation of grain production and consumption,distribution pattern and grain surplus before and after import were analyzed.The results show that China’s total grain output is 661,607,300 tons and total consumption is 751,837,600 tons.In terms of China’s food security,rations can meet self-sufficiency,but considering the comprehensive self-sufficiency rate,imported grain is needed.In terms of spatial distribution,Heilongjiang,Henan and Shandong are important grain-producing areas in China,producing 193.08 million tons of grain,accounting for 29 percent of the total.In terms of grain types,corn,as the most productive grain crop,produced 259,070,700 tons,accounting for 42% of the national grain output.The food selfsufficiency rate of the North and south rose to 126 percent and 82 percent respectively after considering the import of grain.Some provinces and cities in south China still have food security problems,with a large feed grain gap.(2)The multi-objective optimization model based on the minimum difference of freight and diet structure was constructed to simulate the current grain trade situation,quantify the virtual water flow in the process of grain migration,and evaluate the associated effects in the process.The results showed that the total output of inter-provincial grain trade was 94.61 million tons,and there was a pattern of "grain from north to south".In the process of grain trade,38.25 billion m3 of blue water was transported.Through grain trade,28.3 billion m3 of water resources and1.52 million tons of fertilizer were saved nationwide,and 1.01 trillion yuan of economic benefits were generated.However,in the current grain trade pattern,a large amount of grain is transferred from provinces with water shortage,which will lead to unreasonable use of water resources in the long run.(3)Starting from the factors affecting grain trade,construct the suitability evaluation system of trade migration,establish the suitability evaluation model,quantify the support degree of provincial conditions on grain trade,build the optimization model of water resources sustainable transport suitability trade,and optimize China’s grain trade pattern.The results show that the optimum degree of grain migration in China is 4434,the comprehensive blue water output is 33.8 billion m3,and the comprehensive blue water output in water shortage area is 5.178 billion m3.In terms of resource benefits and ecological benefits,36.8 billion m3 water resources and 2.44 million tons of fertilizer can be saved,resulting in 13.6522 billion yuan of economic benefits.