| Food security and water security have become hot issues of global concern.Northeast China is the main grain-producing area and the main supply area of commercial grain in China,it plays the role of"ballast stone"in national food security,and its grain production has an important strategic position.Water security is the foundation of food security,and crops need to consume a lot of water resources during the growing process,which causes a series of water issues.Revealing the key issues of water resources utilization in crop production in this region could provide a theoretical basis for regional sustainable agricultural development,efficient use of water resources and water security and provide a reference for the sustainable evaluation of crop production in other regions.Water footprint hotspots can be used to identify and evaluate water issues during crop production.This paper took the water footprint hotspots of crop production as the research perspective,from the perspectives of resources,environment and economy,five indicators of green water scarcity,blue water scarcity,water pollution level,water use efficiency ratio and water use benefit ratio were selected to establish an index system of water footprint hotspot for crop production,so as to reflect the diversity of water issues and identify key water issues in Northeast China.Based on the calculation of the water footprints of various crops including maize,rice,soybean,wheat,millet,sorghum,tobacco,sunflower,potato,peanut,vegetables in 40prefectures in Northeast China from 2001 to 2017,this paper analyzed the spatiotemporal characteristics of the blue,green,grey and total water footprints of crop production;the types and grades of water footprint hotspots were clarified and their temporal and spatial variation were analyzed,a comprehensive assessment was conducted and the relationships between different hotspot indicators were explored;multiple linear regression was used to identify the main driving factor of water footprint hotspots,and to reveal the temporal and spatial heterogeneity of their impact on water footprint hotspots;a multi-objective optimization model was constructed to explore the regulation role of planting structure optimization on water footprint hotspots.The main conclusions are as follows:(1)The water footprint of crop production in Northeast China had obvious spatial and temporal differentiation characteristics.The average annual total water footprint of Northeast China was 1260.72×10~8m~3from 2001 to 2017,showing a trend of rising first and then slowly decreasing.The variation coefficient of the total water footprint was 0.18,which indicated that inter-annual fluctuations of the total water footprint were small.The total water footprint exhibited a significant positive spatial autocorrelation and had obvious characteristics of spatial agglomeration.Both the high-value and low-value agglomeration trends in the spatial agglomeration trend were strengthening.In time series,the green and blue water footprints of crop production continued to increase,and the grey water footprint first increased and then decreased.The green,blue and grey water footprints of crops accounted for 65.01%,17.25%,and 17.74%of the total water footprint,respectively.Green water occupied a dominant position in the water demand of crop production.In terms of spatial distribution,the green,blue and grey water footprints of the middle and western subregions were generally larger than those of the eastern subregion,and the spatial differences in the proportions of green,blue and grey water footprints were obvious.(2)The spatial and temporal changes in water footprint hotspots of crop production in Northeast China were significant.From 2001 to 2017,the temporal changes of different types of water footprint hotspots in Northeast China were different.Both the green water scarcity and blue water scarcity in Northeast China were hotspots every year;more than half of the years were hotspots for water pollution level;there were no hotspots for water use efficiency ratio every year;for the hotspots of water use benefit ratio,they were all hotspots before 2008,and there were no hotspots after 2008.In terms of spatial distribution,the hotspots of green water scarcity were widely distributed,and most of their grades were grade I;the hotspots of blue water scarcity and water pollution level were mainly located in the middle and western subregions and their grades were mainly grade II and grade III;the hotspots of water use efficiency ratio were mainly in the northern region and most of their grades were grade I;the hotspots of water use benefit ratio were mainly in the eastern region and their grades were mostly grade I and grade II.Overall,the issues of green water scarcity,blue water scarcity and water pollution were more serious in Northeast China.The hotspots of blue water scarcity and water pollution level showed superimposed distribution in space.(3)The main driving factors of the different types of water footprint hotspots of crop production had a difference and changed with time.Precipitation,as the primary driving factor,had a significant negative impact on green water scarcity;the effective irrigation area and chemical fertilizer application,as the primary driving factor,had a significant positive impact on blue water scarcity;the chemical fertilizer application,effective irrigation area and precipitation,as the primary driving factor,had different effects on water pollution level,among them,the chemical fertilizer application and effective irrigation area had a significant positive impact on water pollution level,and precipitation had a significant negative impact on water pollution level;average temperature and the per capita disposable income of farmers,as the primary driving factor,had a significant negative impact on water use efficiency ratio;the per capita disposable income of farmers and GDP per capita,as the primary driving factor,had a significant negative impact on water use benefit ratio.(4)The main drivers of different types of water footprint hotspots of crop production were spatially different.For green water scarcity,single-natural factor-driven was the main type,with wide distribution;for blue water scarcity,natural and human factor-driven and single-natural factor-driven were the main types,which were distributed in Sanjiang Plain,Songnen Plain,Liaohe Plain,southern coast and Changbai Mountains regions;for water pollution level,single-natural factor-driven and natural and human factor-driven were the main types,which were distributed in Liaohe Plain,Songnen Plain,Changbai Mountains regions and Western Liaoning;for water use efficiency ratio,single-human factor-driven and single-natural factor-driven were the main types,which were distributed in Southern coast,Songnen Plain,Sanjiang Plain and Changbai Mountains regions;for water use benefit ratio,double-human factor-driven was the main type,with wide distribution.(5)The optimization of the planting structure can simultaneously regulate different types of water footprint hotspots of crop production.After the optimization of the planting structure,the maize planting area of each prefecture in Northeast China has decreased,the rice planting area has declined slightly but basically remained stable,and the planting area of other crops has increased in varying degrees.After the optimization,the index values of the water footprint hotspots decreased in most areas,and the average degree of decrease was water pollution level(0.23)>water use benefit ratio(0.06)>blue water scarcity(0.05)>water use efficiency ratio(0.02)>green water scarcity(0.01).The differences in change values of green water scarcity in the eastern,middle,and western subregions were small.The decrease in blue water scarcity and water pollution level in the middle and western subregions was larger than that in the eastern subregion,while the decrease in the water use efficiency ratio and water use benefit ratio in the middle and western subregions was smaller than that in the eastern subregion.Taking the water footprint hotspots of crop production as the research object,this paper established a comprehensive evaluation framework for water issues in crop production,explored the existing issues of water resource utilization in crop production in Northeast China,sought the corresponding solutions,and provided a scientific basis for sustainable agricultural water resources management in Northeast China. |
PDF Full Text Request