| The Northwest China is vast and has many ethnic groups.It is an important strategic highland,resource-rich land and ecological barrier for China.However,with the continuous development of social economy,the Northwest China is facing serious water shortage and ecological environmental damage,which has increasingly become the "short board" for sustainable development in the Northwest China.In response to the severe pressure on water resources and the stress of the ecological environment in Northwest China.In this paper,a water resources footprint and carrying capacity model is constructed to evaluate the supply and demand of water resources and the spatial and temporal distribution of water resources carrying capacity in the study area,comparative analysis of the characteristics of virtual water changes in crop production in the study area from three aspects:physical flow,utility flow,and trade flow.Finally,the sustainable development of agriculture in Northwest China was evaluated by using the theory of ecosystem emergy.This research obtained the following main conclusions:(1)Clarified the characteristics of the temporal and spatial patterns of the ecological environment and social economy in Northwest China.By analyzing the changes in land use,normalized vegetation index(NDVI),and vegetation net primary productivity(NPP)in the study area from 2000 to 2018,it is found that urban construction land in Northwest China has been in a trend of expansion.Large-scale urban construction land mainly comes from the transformation of grassland;The vegetation coverage is low,most of the area vegetation coverage is below 0.5,and the vegetation NPP is 0-200gC/m2,and the ecosystem service value is reduced by 676.827 billion yuan.The social economy of the Northwest China is showing a trend of continuous development.The population in the region has increased by 16.8594 million people,the GDP increased by 5,565.170 billion yuan,and the output value of primary,secondary and tertiary industries has increased by 4,541.50,2,407.60 and 2,701.920 billion yuan respectively.Therefore,the ecological environment in the northwestern region is relatively fragile,and the improvement of the ecological environment and the development of social economy should be considered as a whole.(2)Analyze the status quo of water supply and demand in Northwest China,revealing the characteristics of temporal and spatial changes in water resources carrying capacity in Northwest China.In 2018,the total amount of water resources in Northwest China was 19,750 million m3,the total water supply was 77.574 billion m3,the total water consumption was 92.846 billion m3,the water consumption was 62.822 billion m3,and the utilization rate of water resources was 46%.Constructed a model of water footprint and carrying capacity in Northwest China.During 2000-2018,the total water footprint of the study area increased by 2735.55hm2,a growth rate of 21.94%.Among them,the Tarim Basin and Junggar Basin showed a trend of rising first and then falling,the Yellow River Basin showed a trend of first falling and then rising,and the Semi-arid Grassland Area,the Hexi Inland River Basin and the Qaidam Basin were basically stable.At the same time,the highest water footprint intensity of the Tarim Basin is 1.56,indicating the lowest water use efficiency.The Qaidam Basin's water pressure index is less than 1,indicating that its water supply and demand are in a state of sustainable use.(3)It reveals the spatio-temporal pattern and evolution of the virtual water of bulk crops.By analyzing the physical flow,utility flow,and trade flow of the six main crops in the study area,it is found that the physical flow has a fluctuating upward trend(except the Yellow River Basin).Among them,the Tarim Basin has the largest annual average change rate,which is 4.77%;the change of utility flow is Fluctuation declines(except the Qaidam Basin),the Yellow River Basin has the largest average annual rate of change,which is 5.39%;the trade flows show a fluctuating upward trend(except the Yellow River Basin),and the Tarim Basin has the largest annual average rate of change,which is 5.40%.(4)Evaluated the sustainable development capacity of the agricultural eco-economic system in Northwest China.Apply emergy theory to analyze the emergy input and output of the study area and the regional differences of each district.The average emergy investment rate(EIR)of the agricultural ecosystem in Northwest China from 2000 to 2018 is 1.11,which is lower than the national average(4.93).It shows that its economic development is low,agricultural natural resources are not used efficiently,and there is still a lot of room for growth;The net emergy output rate(EYR)average value is 1.91,which is lower than the national average(2.56),indicating that its ecological economic system exports emergy to the outside world,which is a resource-exporting system and will be at a disadvantage in the current trading system;The average environmental load rate(ELR)is 3.11,which is higher than the national average(2.80)and is increasing year by year,indicating that its eco-economic system is under greater environmental pressure;The mean value of the Emergy Sustainability Index(ESI)is 0.61,indicating that the system as a whole is in an unsustainable resource-consuming system.(5)The degree of sustainable agricultural development in Northwestern China is predicted.Based on the water resources quantity index,the sustainable development emergy value of the study area was evaluated,and the difference of sustainable development emergy under the two scenarios of water transfer scenario and current situation was compared and analyzed.Obtained that the average EIR(1.11)and the average ELR(3.11)of the current situation of the study area and each district from 2000 to 2018 are higher than the average EIR(0.68)and the average ELR(1.28)of the water transfer scenario,and the average ESI(0.61)of the current scenario is lower than the average ESI(1.49)of the water transfer scenario),which further shows that the ecosystem in the northwest region after the transfer of water resources has more development potential than the original. |
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