| China is the most populous country in the world, food security and water security is an important issue bearing on China’s national life and national stability. Due to asymmetry of spatial distribution of soil and water resources in China, inter-regional grain distribution provides new ways of thinking in order to ensure China’s grain security at provincial level and ease water resources pressure on regional. Therefore, quantitative studies of the inter-regional grain distribution,grain virtual water flow and impact of virtual water flow on regional water resources, has a very significant and strategic importance. On the basis of China’s grain production data at provincial level,This study calculates the regional grain production water index, count of grain transportation quantity and grain virtual water flow inter region in china with social equity method and gravity method in china 2013. On this basis, using the indicator of the national water saving and water resource stress index and ombining the two methods of accounting results, we study the impacts of grain virtual water flow on water resources. Specific results are as follows:(1)Spatial distribution asymmetry of water resources and arable land, leads to grain allocation among the various provinces in China. The output grain of Huang-Huai-Hai region and the Northeast of China is more than 50% of the national total gross;grain production of Huang-Huai-Hai region, Northeast China and the Yangtze River area is more than 70% of the national gross. About 90% of the food is from the Huang-Huai-Hai area, Northeast, Northwest, Southwest and middle and lower reaches of the Yangtze River. 56.35% of the national output gross of grain yield is in northern China, and 43.65% in southern area. Comparing to 2012, gap of food production in North and South is further expanded;(2)Grain allocation among the various provinces in China is obvious and rising: Northeast and Huang-Huai-Hai region are the major output regions. Grain distribution of Northeast is the most; North China, Northwest, Southeast, Middle and lower Yangtze River, South China and Southwest are input areas, and grain distribution of South China is the most. Comparing to social equity method, gravity method is more detailed calculations of the grain output path and enter sources with adding component of distance;(3)Counting of grain virtual water flow with social equity method and gravity method in China 2013 is the same in output area. Gravity method is more detailed calculations of the grain virtual water flow output path and enter sources with adding component of distance;(4)An important characteristic of regional grain virtual water flows among areas is from high water use efficiency of food production into inefficient use of areas achieving a certain degree of water-saving in the national scale. with grain virtual water flows among the various provinces, national-scale water saving is 62.684 billion m3 in China 2013. And the results of social equity method and gravity method are in complete agreement;(5)Another important characteristic of regional grain virtual water flows among areas is from high water resources pressure to low water resources pressure, further exacerbating the water resources pressure of output area. Without grain virtual water flow among regions, water resources pressure of output area will drop down, but input area will increase.Social equity method is the traditional method of accounting food virtual water flow,which does not consider the distance between the regions. Using the social equity method at the same time, this paper uses the formula of universal gravitation, introduces the gravity method to calculate grain virtual water flow and compare it with the social equity method. Regional virtual water flow of grain is bound to impact on regional water resources. This paper analysis the influence of regional virtual water flow of water through two indicators of national scale saving water and water resources pressure. |
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