Analysis Of The Regional Virtual Water Flow Process Associated With The "North-to-South Grain Transport" And Countermeasures In China

Grain production is a complex and integrated system,accompanied by various environmental problems such as water consumption,greenhouse gas emissions,and non-point source pollution.Meanwhile,as a process link with high water consumption and low economic benefits,it plays an important role in water resources utilization,economic development and social stability.Due to the dislocation of the temporal and spatial distribution of water and land resources,grain production needs to pay more attention to water shortages and water security issues in China.As a comprehensive index for evaluating water use efficiency,water footprint could evaluate the type,quantity,efficiency,and environmental impact of water use in agriculture,and improve the evaluation and management of agricultural water use.In addition,there is a significant spatial imbalance between grain production and consumption in China.“The North to South Grain Transfer Pattern” formed by inter-regional grain production and consumption has led to the redistribution of water resources among regions in the form of virtual water,which has an unclear impact on regional water resources utilization and the environment.Based on the scientific connotation of water footprint and virtual water theory,this study explored the formation mechanism of “the North to South Grain Transfer Pattern”,analyzed the temporal and spatial evolution characteristics of water footprint of grain product(WFP)and virtual water flow,clarified the virtual water flow path between regions,revealed the resource and environmental effects associated with “the North to South Grain Transfer Pattern”,and derived the main response strategies.The main conclusions are as follows:1.The formation process and driving mechanism of “the North to South Grain Transfer Pattern” were discussed.The results showed that,except for Beijing,Shanghai,Zhejiang,Fujian and Guangdong,the grain production of remaining provinces basically showed a continuous increasing trend.Total grain production increased from 239.96 million tons to 66.34 million tons.Grain production was gradually gathering in the northern region.Although the grain production of the north began to surpass that of the south after2005,the difference in grain production and population growth caused traditional “the South to North Grain Transfer” to be converted to “the North to South Grain Transfer”from 1990.The northward shift of grain production and the gathering of the population in developed areas in the south jointly driven the formation of “the North to South Grain Transfer Pattern”,which is difficult to reverse in the short term.2.The temporal and spatial evolution characteristics of the WFP in different regions were revealed from 1997 to 2017.The results showed that the national average WFG,blue water footprint of grain product(BWFP)and green water footprint of grain product(GWFP)all showed a basic downward trend,from 1.395m~3/kg,0.631m~3/kg and 0.765m~3/kg in 1997 to 1.060m~3/kg,0.432m~3/kg and 0.628m~3/kg in 2017,respectively.There were obvious differences between regions.Guangdong had the largest WFP,while Shandong and Henan have smaller WFP.The WFP in the southern region was higher than that in the northern region,both showed a clear downward trend.The proportion of the GWFP was larger than that of the BWFP,but the decreasing trend of the WFP was mainly caused by the change of the BWFP.3.A general analytical method for virtual water flow between regions was created.The virtual water flow path between regions was determined,and the temporal and spatial change characteristics of the regional virtual water flow from 1997 to 2017 were clarified.The results showed that the amount of grain virtual water flow in 2017 was 2.02 times that of 1997,increasing from 72.99 billion m~3 in 1997 to 147.26 billion m~3 in 2017.The export areas gradually gathered in the northern region.Virtual water export centers were basically formed by Heilongjiang,Jilin,Inner Mongolia,Henan,Anhui,and Shandong;the grain import regions gradually gathered to the south,and were basically formed by Guangdong,Zhejiang and Shanghai.4.The accompanying effects of regional virtual water flow were clarified.As the virtual water flow continued to increase,the pressure of surface water and groundwater in the export area also increased.Meanwhile,due to the continuous reduction in the scale of grain virtual water export in Hebei,it played a certain role in alleviating the decline of groundwater level in North China.The results of the study showed that the virtual water flow pattern shifted from areas with a smaller gray water footprint and carbon footprint per unit of grain production to areas with a larger.Therefore,the current virtual water flow pattern has the potential to reduce the overall gray water footprint and carbon footprint at a national scale,and presented a national environmentally friendly model as a whole.However,it increased the environmental pressure on grain export areas to a certain extent.5.Based on the research results,the following countermeasures were initially proposed: Optimize crop planting structure,reduce WFG,and improve agricultural water efficiency;The development of water-saving irrigation technology has played a significant role in promoting agricultural water-saving.We could improve water-use efficiency by vigorously promoting agricultural water-saving technology;There is a significant difference in water use efficiency for grain production between regions.The goal of national water saving could be achieved by guiding the grain trade path from regions with lower WFP to the higher;A certain amount of virtual water import fee could be collected from the grain import area to compensate for the economic loss of the virtual water export area.In summary,this study focused on the transfer and flow of water resources in the process of grain production and consumption,and explored the conversion effect of water resources from physical water to virtual water system during the formation of “the North to South Grain Transfer Pattern”;Analyzed WFP and virtual water flow and determined the virtual water flow path between regions,which provided reference for realizing regional virtual water regulation;Revealed the water resources utilization and environmental effects associated with “the North to South Grain Transfer Pattern”;Provided initially countermeasure support for the development of water agriculture in order to provide reference for the formulation and implementation of national water and grain policies.