Evaluation Of Water Scarcity In China's Mainland Based On Water Footprint Theory

Water is the basic natural resources on which human society development and ecosystems survival depend.With the rapid development of human society and economy,the contradiction between supply and demand of water resources is increasingly prominent,and the potential for a water crisis has become an important obstacle to the sustainable development of society,freshwater scarcity is a growing concern.Water footprint was proposed based on the virtual water theory,which connects the virtual water with the physical water,and provides a new way to evaluate the water scarcity more comprehensively.Due to the large proportion of agricultural water use in China's mainland,this study focused on the spatial and temporal distribution characteristics of water footprint of wheat,maize and groundnut from 1961 to 2009.The index of blue water scarcity was constructed by considering the environmental water demand,the water scarcity of agriculture,industry and domestic in China's mainland was evaluated,and the severity and the number of people facing water scarcity were accurately assessed.Previous water scarcity assessments have measured annual variations in water scarcity on a large scale(basin,city)and underestimated the experience of water scarcity by failing to capture the inter-annual fluctuations in water consumption and availability.Therefore,this study made corresponding improvements to these problems and proposed more accurate assessment results based on past,which provided an important basis for rational utilization and sustainable development of water resources.The main results of this study are as follows:(1)During 1961 to 2009,the average annual water footprint of wheat,maize and groundnut production in China's mainland were 3.67m3/kg,1.40m3/kg and 2.87m3/kg respectively.The green water footprint,blue water footprint and total water footprint of wheat showed fluctuating downward trends.The green water footprint and the total water footprint of maize were decreased continuously,while the blue water footprint did not decrease obviously.The green water footprint,blue water footprint and total water footprint of groundnut showed decreasing trends.(2)In 1961,the water footprint of wheat,maize and groundnut in China's mainland was higher in the eastern and central regions and lower in the western regions.In 2009,the water footprint of wheat,maize and groundnut in China's mainland was lower than that in 1961,among which the water footprint of wheat,maize and groundnut was lower in the west and east.(3)Blue water scarcity was often intense and frequent in densely populated regions(e.g.,Haihe River Basin,Huaihe River Basin,the central of Songhua and Liaohe River Basin,the northern Yellow River Basin and the parts of Yangtze River Basin).We found that about 0.979 billion people(70%of the China population)lived under conditions of water scarcity at least one month of the year.About 0.803 billion people(58%of China population)experienced severe water scarcity at least one month of the year.In addition,0.247 billion people faced severe water scarcity at least half of the year in mainland of China.That means the situation was worse than previous studies have suggested.According to the results of this study,we suggested that we should pay attention to the following aspects in the integrated management and utilization of water resources:making water resource management strategies according to the causes of water scarcity,making water resource management strategies according to river basins,managing water resources according to different periods,distinguishing between the water quantity and water quality scarcity,and paying equal attention to the protection and utilization of water resources.The results show that,with the ecological damage and economic loss caused by water scarcity more and more serious,it is very important to understand the temporal and spatial changes of water scarcity for determine the areas where the water availability and water footprint do not match in a specific period of time.These results may contribute to the allocation and management of local freshwater resources.