Inter-provincial Virtual Water Research Articles

Multiplex dependence analysis of China's interprovincial virtual water based on an ecological network.

The interprovincial circulation of goods and services has formed virtual water flows between regions, which can redistribute water resources. Based on previous virtual water trade research, this study further explored the multiple dependencies of virtual water, i.e., direct, indirect, and complete dependence. This study examined the direct, indirect, and complete dependence of virtual water between provinces in China by constructing multilayer dependence networks and identified the key regions and paths of virtual water trade network. The results showed direct dependence was the densest and had the largest overall dependence degree, but indirect dependence was the most stable and orderly. Second, the dominant provinces were Guangxi, Hunan, Sichuan, Xinjiang, and Anhui, referred to as "core‒five‒region," and the flow relevant to them accounted for approximately 30% of the virtual water. The seven provinces of Shanxi, Zhejiang, Shandong, Hubei, Guangdong, Shaanxi, and Gansu depend both directly and indirectly on the "core‒five‒region." Shanxi and Zhejiang have close direct and indirect dependence, with more than one of the "core‒five‒region." Guangdong was the province with the most direct and indirect input of virtual water from the "core‒five‒region." The study provides a scientific basis for multiregional identification for the collaborative management of water resources in China from the perspective of dependence.

Diversities and sustainability of dietary water footprint and virtual water flows in China

Increasing dietary diversity while avoiding additional stress on water resources remains a critical challenge for sustainability. However, the precise understanding of the physical water consumption and virtual water flows associated with diversified diets remains unclear. This study estimated the dietary water footprints (WFs), interprovincial virtual water flows, followed by assessing the unsustainable blue WF and water scarcity footprint (WSF) in China over 2015–2019. Rural and urban food intake, waste, and differences between eating at home and out were considered. The findings reveal that China’s dietary patterns have gradually strayed from recommended guidelines, with an overconsumption of cereals and inadequate intake of dairy products and potatoes. Despite a decrease, both unsustainable blue WF and WSF remained significant, measuring 249.61 Gm3 and 807.77 Gm3 H2O-eq, respectively, in 2019. Notably, water-scarce regions still accounted for a substantial portion of unsustainable virtual blue water exports. The diet related virtual water reallocation can offset the water savings on the crop production side.

Spatiotemporal heterogeneities in water and land appropriations related to food losses and waste in China

Fast-growing food losses and waste (FLW) have caused major environmental issues, yet little is known about the role of trade in the inefficient resource consumption related to FLW. In this study, we estimated the inter-annual water footprints (WFs) and land footprints (LFs) related to FLW in consideration of associated inter-provincial virtual water (VW) and virtual land (VL) flows within China from 2000 to 2017. Additionally, differences between eating at home and out in rural and urban regions were distinguished. The FLW-related WF and LF showed 1.5- and 1.2-fold increasing trends, respectively, over the study period. Eating at home in rural regions caused the most FLW and associated water and land appropriations. Both FLW-related gross inter-provincial VW and VL flows increased by 99% and 22% during the study period, respectively, and inter-provincial VW and VL flows in corresponding FLW-related WF and LF differed significantly. In addition, food losses were found to cause more inefficient resource consumption than food waste. This analysis shows that the substantial role of FLW in shaping the intra-national food-related VW and VL networks, and that the policies for FLW diminution at the food supply chain stage are as important as those at the consumption stage.

Evaluating grain virtual water flow in China: Patterns and drivers from a socio-hydrology perspective

To ensure regional grain security, the grain is transferred from grain surplus provinces to grain deficient provinces in China, then water embedded in grain (virtual water) flows accordingly, which promotes the spatial redistribution of water resources. To explore the influencing factors of virtual water flow, this study first obtained the inter-provincial virtual water flow pattern, and then constructed a virtual water flow trade gravity model based on socio-hydrology theory and estimated the model with multiple regression methods. And the impulse response function was used to analyze the response trajectory of virtual water flow under the shock of other endogenous variable fluctuation. The results show that from 1997 to 2014, the quantity of inter-provincial grain virtual water flow increased from 73 billion m3to 124.64 billion m3. The positive driving effect of the population and per capita GDP in virtual water inflow areas is significant, and the negative suppression effect of the grain output per unit in inflow-areas and the population in outflow-areas is significant. Heilongjiang is the province with the largest outflow of virtual water, and the outflow is more sensitive to the shock of local per capita water resources fluctuation. Guangdong is the province with the largest inflow, and the inflow is more sensitive to the local per capita GDP fluctuation. Chinese Mainland’s grain virtual water flow pattern and trend will continue to exist in the future. In addition to the endowment of water resources, social and economic factors also need to be considered during the process of water resources management.

Irrigation water use and efficiency assessment coupling crop cultivation, commutation and consumption processes

Water use and efficiency assessment from crop production-consumption process provided a new perspective for regional agricultural water management. An evaluation framework of water use efficiency (WUE) coupling crop cultivation, commutation and consumption processes was established in this paper. The impact of virtual water flow on provincial irrigation water use efficiency, and its implications for irrigation management were assessed based on the inter-provincial virtual irrigation water flow (VIWF) estimation for cereals of China The results showed that national IWU, IWP and IE for cereal production in 2018 were 268.89 Gm³ , 1.815 m³ /kg and 0.494 respectively. Total VIWF among 31 provinces was calculated to be 85.25 Gm³ , with the contributions of 43.8% rice, 40.0% wheat, and 16.2% maize. IWP and IE from the crop consumption perspective in all provinces were different from that observed from production perspective, and the effect of crop supply-demand mismatch on irrigation WUE was comprehensive. Virtual water flow was conducive to water resource conservation and irrigation WUE improvement when judged by IWP. However, the result was just the opposite when IE was used as the evaluation. Improving IWP in the North China Plain and Southeast and optimizing trade structure in Northeast and Southwest contribute to national irrigation water conservation from both of the production and consumption perspectives. The evaluation framework proposed in current paper can inspire the research on agricultural water assessment, management and regulation combining the physical and virtual water.

A Study on Drivers of Water Consumption in China From a Complex Network Perspective

Water consumption has been one of the most important topics in the field of environment and economy. Even though the driving factors of water consumption have been well studied, it is still a daunting task to reveal the influence of the status of provinces in the entire supply chain. By combining the multi-regional input-output (MRIO) model and complex network theory, an inter-provincial virtual water transfer (V WT) network was constructed to analyze the overall structural characteristics of the network model and identify the structural roles of each province. The constructed inter-provincial V WT network exhibited the characteristics of a small-world network, that is, virtual water can be easily transferred from one province to another. Moreover, network analysis revealed that provinces with different positions in the V WT network played discrepant structural roles. Panel regression analysis was further used to quantify the impact of provincial structural roles on their water consumption. The results showed that water consumption in China largely depended on some structural role characteristics in the V WT network. Out-degree and out-strength characterizing the ability of direct exporting virtual water exerted significant positive influences, while in-closeness featuring the indirect virtual water importing rate had a significant negative effect on water usage. This indicated that adjusting the uneven provincial consumption structure, the direct production demand of downstream provinces and the indirect production activities in the supply chain would help reduce water consumption. Therefore, to come true the goal of water conservation in China, it would be necessary to improve the trade structure between direct and indirect exporters and importers in the entire supply chain.

Water-Saving Efficiency and Inequality of Virtual Water Trade in China

Virtual water trade is widely considered as a potential method to solve local water shortage and unequal distribution. However, limited research investigated water-saving efficiency and water inequality of inter-provincial virtual water trade. In this study, we sought to explore this issue within China based on the 2015 input-output data. A multi-regional input-output model and a modified input-output model were used to estimate the virtual water trade and its impact on water-saving and water inequality. Our results suggest that: (1) The total virtual water flow across the country is 200.03 × 109 m3, which accounts for 32.77% of water withdrawal. The agriculture sector contributes the highest proportion (73.99%) to virtual water flow. (2) Virtual water trade could decrease water withdrawal by 446.08 × 109 m3 compared with withdrawal under no-trade situation at a national level, and 22 provinces could gain benefits through inter-provincial trade with a positive water-saving efficiency index. (3) Virtual water trade also causes water inequality, which exacerbates water scarcity of exported provinces, especially in northwest provinces. (4) There is a conflict between water conservation and water inequality, but different provinces show significant heterogeneity.

Evolution of China’s Interprovincial Water Flow Network

Traditionally, water governance focuses on water only. The emergence of virtual water breaks this limitation and integrates economic and social systems with the water resource system. This paper establishes an interprovincial complex network of virtual water flows in China, based on the theory on complex network, which has rarely been adopted to study the virtual water transfer network. Then, the authors analyzed the pattern and evolutionary features of China’s interprovincial virtual water flow network. In this way, the complex network theory was successfully applied to explore the virtual water flows across provinces in China.

The impact of water scarcity on Chinese inter-provincial virtual water trade

Chinese water resources are limited and unevenly distributed across space, making the inter-provincial virtual water trade increasingly prosperous. Many studies have focused on the impact of virtual water trade on regional water scarcity, but little consideration has been paid to the impact of water scarcity on virtual water trade, particularly in China. To fill this gap, we addressed the Chinese inter-provincial virtual water trade in 2012, 2015 and 2017, and we combined a multi-regional input-output analysis with a gravity model supplemented by the instrumental variable method. Our results indicated water pressure values were higher in northern areas, and provinces with extreme water stress were distributed in the eastern coastal areas. Additionally, virtual water tends to be exported from water-poor regions to water-rich regions. The results of the gravity model show that the Chinese inter-provincial virtual water trade is significantly related to water scarcity. We found that virtual water flow is positively correlated with the water scarcity of exporting regions, such as Xinjiang, Heilongjiang, Anhui, and Jiangsu, and it is negatively correlated with the water scarcity of importing regions, such as Shandong, Guangdong and Zhejiang. Therefore, water scarcity affects the virtual water trade flow, and the trade in turn exacerbates the regional water shortage in the northern and eastern coast of China. In addition, the virtual water trade is affected by socio-economic factors and environmental factors. We suggest that related policies should be developed to terminate this malignant cycle. The virtual water trade should be guided towards becoming more adaptable to sustainable development rather than allowing for water-scarce areas to pursue economic development at the cost of scarce water resources.

Evolution of interprovincial virtual water flows along with electricity transmission and its impact on water scarcity in China

The spatial mismatch between energy resources and water resources has been widely concerned. Electricity trade drives virtual water flows from electricity production sides to consumption sides, which can aggravate or alleviate regional water scarcity. Investigating the historical evolution of virtual water transmission and its impacts on water scarcity benefits the sustainable development of energy and water. To reduce data uncertainties, in this study, we built provincial water intensity of electricity generation inventory considering the impacts of factors such as electricity generation types, cooling technologies and generator units. Besides, to investigate how the direction and quantity of virtual water flows aggravate or alleviate the regional water scarcity, the impact assessment model was built, and the impact assessment index was defined. The results showed that the water consumption of electricity generation and interprovincial virtual water transfer increased by 2.61 times and 5.12 times during 2005–2015, respectively. Changes in the amount of electricity generation and the electricity transmission structure were the two main drivers of increases in virtual water flows, contributing to a total increase of 85.28%. A large amount of virtual water was transferred from the southwest and the northwest to the eastern coastal areas. There were many “positive flows” from the southwest to Jiangsu-Zhejiang-Shanghai, while “negative flows” were concentrated in Xinjiang-Henan, Gansu-Qinghai and Gan-Shaanxi. The nodes with the largest impact assessment index value were Hubei, Sichuan and Shanghai, while the lowest were Gansu, Xinjiang and Qinghai. This study can provide a basis for optimizing the electricity generation mix and electricity transmission structure, alleviating the growing tension between energy and water, and realizing the sustainable development of water resources.

Agricultural infrastructure: The forgotten key driving force of crop-related water footprints and virtual water flows in China

Here we identified and evaluated the strengths and spatio-temporal heterogeneities in 12 main socio-economic driving factors of water footprints and inter-provincial virtual water flows related to three staple crops (rice, wheat, and maize) within mainland China for 2000–2017, in consideration of the infrastructure related to irrigation, agricultural electricity and road for the first time. The irrigation, agricultural electricity, and road infrastructures in China expanded by 33.8, 4.5, and 2.4 folds, respectively, throughout the course of this study. The results show that irrigation infrastructure in water-scarce regions was the most critical driver for the effective reduction of the water footprint per unit mass of crops, particularly the blue water footprints (i.e. increasing water efficiency). As the irrigation infrastructure per unit area doubled for 2000–2008, blue water use efficiency and total blue water consumption decreased by 58% and 71%, respectively. However, the development of irrigation infrastructure has led to a larger total water footprint in crop production. Agricultural electricity and road infrastructures had increasing effects on provincial virtual water export, with varied corresponding driving strengths across spaces. The visible effects of agricultural infrastructure on regional water productivity, water consumption, and virtual water patterns should not be neglected. This analysis suggests that investments in agricultural infrastructure should consider the spatio-temporal heterogeneity of these infrastructures on local water productivity and water consumption in addition to the economic benefits.

What the reclaimed water use can change: From a perspective of inter-provincial virtual water network

Reclaimed water has been used as an alternative water resource for various economic activities, which inevitably is involved in the virtual water trade. However, the effect of reclaimed water on the virtual water trade has not been evaluated in previous studies. For the sake of sustainable water management, this study explored the benefits of reclaimed water use for balancing the water resource allocation at the interprovincial level. Multiregional input-output analysis and ecological network analysis were used to investigate the spatial and structural characteristics of the virtual reclaimed water network (VRWN) among 31 provinces in China and the potential effect of reclaimed water use. The results show that the net export flows of virtual reclaimed water have different spatial patterns from those of freshwater, some provinces that import virtual freshwater are exporters of virtual reclaimed water. Although the exploitative relationship is the dominant ecological relationship in the VRWN (72%), it is confirmed that reclaimed water use contributes to balancing the virtual water trade of China with a more competitive relationship (21%) than in the virtual freshwater network (4%). The virtual freshwater consumption change rate in developed provinces decreases by more than 10% through reclaimed water use. Due to the high food exports and low application of wastewater reclamation in less developed provinces, the effect of reclaimed water use in those provinces is not as obvious as that in developed provinces. This paper offers a new perspective for understanding the current VRWN and guidance for the optimization of the virtual water trade structure.

Virtual Water Trade in the Yellow River Economic Belt: A Multi-Regional Input-Output Model

The sustainable and efficient use of water resources has gained wide social concern, and the key point is to investigate the virtual water trade of the water-scarcity region and optimize water resources allocation. In this paper, we apply a multi-regional input-output model to analyze patterns and the spillover risks of the interprovincial virtual water trade in the Yellow River Economic Belt, China. The results show that: (1) The agriculture and supply sector as well as electricity and hot water production own the largest total water use coefficient, being high-risk water use sectors in the Yellow River Economic Belt. These two sectors also play a major role in the inflow and outflow of virtual water; (2) The overall situation of the Yellow River Economic Belt is virtual water inflow, but the pattern of virtual water trade between eastern and western provinces is quite different. Shandong, Henan, Shaanxi, and Inner Mongolia belong to the virtual water net inflow area, while the virtual water net outflow regions are concentrated in Shanxi, Gansu, Xinjiang, Ningxia, and Qinghai; (3) Due to higher water resource stress, Shandong and Shanxi suffer a higher cumulative risk through virtual water trade. Also, Shandong, Henan, and Inner Mongolia have a higher spillover risk to other provinces in the Yellow River Economic Belt.

Simulation of the virtual water flow pattern associated with interprovincial grain trade and its impact on water resources stress in China

With fast development of economy and trade globalization, the water resources system has undergone profound changes due to the overconsumption of physical water and the complex virtual water flow. China is poor in water and rich in arable land for the north, but rich in water and poor in arable land for the south. The spatial mismatch of water and food production has posed a great threat to sustainable development. To quantify the virtual water flow with grain trade and evaluate its influence on the regional water resources system, this study simulated the interprovincial virtual water flow embedded in grain transportation based on a linear optimization model and assessed the water pressure induced by virtual water flow. Results show that the annual virtual water flow (as much as 73.46 billion m3 in 2012) associated with interprovincial grain trade is mainly from the North to the South. The grain output areas are mainly located in the Northeast, Northwest, and the North China Plain, while the grain input areas are mainly distributed in the eastern and southern coastal provinces with well-developed economies. According to the estimation, when China’s food demand reaches a peak of 650 million tons in 2030, the virtual water flow will further increase and the volume of virtual water flowing out of Northeast China will be up to 50 billion m3, accounting for 90% of the total virtual water flow. The increasing the virtual water outflow in North China will severely exceed the local water resources capacity in the arid and semi-arid areas and have an obvious negative impact on sustainable development in Northern China. Further improving the water use efficiency, adjusting the structure of spatial grain production distribution and physical-virtual water coupled management are effective countermeasures to ensure the coordination safety of food and water in China.

Interprovincial food trade and water resources conservation in China

A spatial mismatch in water and arable land availability results in large virtual water transfers through interprovincial food trade in China. Accurately identifying and measuring water-saving links in interprovincial food trade can help to relieve water resources pressure in main grain-producing areas. We use a multiregional input-output table combined with the CROPWAT model to build China's interprovincial virtual water transfer network embedded in food trade in 2012. Then, water saving and scarce water saving are measured. Both consider the difference in water productivity among provinces, but the latter also pays attention to the scarcity of water resources. Finally, we adopt a water footprint to recalculate the scarce water savings without precipitation (green water). Our results indicate that the amount of virtual water transfer embedded in food trade is 74.9 billion m3, which is equivalent to 12.22% of the total water use in 2012. We observe large variations in the relationship between water resources abundance and agricultural water-use efficiency across provinces. Especially, there is a virtual water transfer from provinces with high water productivity but a lack of water to provinces with low water productivity but an abundance of water. The scarce water saving can identify sustainable food trade links, which can alleviate water scarcity in consuming provinces without exacerbating water shortage in producing provinces. In addition, interprovincial food trade results in 15 billion m3 of scarce gray water saving, which is equivalent to 59.76% of the scarce blue water saving. Scarce water saving based on blue water and gray water provides a basis for establishing an interprovincial compensation mechanism to balance the cost of water redistribution caused by food trade.

The impacts of interprovincial electricity transmission on China’s water crisis: Mitigate or aggravate

Along with electricity transmission, virtual water is transferred from electricity generation provinces to load hubs, reallocating spatial water resources and impacting regional water scarcity. To assess whether virtual water in electricity transmission mitigated or aggravated national water scarcity, a rationality assessment model was proposed from energy-water nexus perspective. The interprovincial virtual water flows were calculated based on provincial water intensity and electricity transmission considering the provincial electricity generation mix. The flow rationality index and node rationality index were proposed and defined to evaluate the net benefit of virtual water flows and provinces, respectively, according to the interprovincial differences in water stress index. The results show that: 1) a large amount of virtual water was transferred from the northwest and southwest provinces to the southeast provinces and Beijing-Tianjin-Hebei region; 2) the flow with the highest flow rationality index is Inner Mongolia-to-Hebei (29.8), while the lowest one is Shanxi-to-Hubei (−102.5); 3) the node with the highest node rationality index is Hebei (32.0), while the lowest one is Shanxi (−104.7). By quantifying the impacts of electricity transmission on provincial and national water stress, this study aims to provide guidance for national virtual water strategy by electricity transmission to mitigate national water scarcity.

Energy-water nexus in electricity trade network: A case study of interprovincial electricity trade in China

The large amount of electricity generation is exerting tremendous pressure on water resources. Moreover, the spatial mismatch between water and electricity demand is aggravating national water scarcity through virtual water transfers in electricity trade. To investigate the impact of electricity trade on water resource and further provide insights into the optimization of national electricity trade pattern from virtual water strategy perspective, the impact evaluation model for interprovincial electricity trade network by evaluating and quantifying the “positivity” or “negativity” of electricity trade is constructed. The interprovincial virtual water transfer network is constructed, and the hybrid virtual water content is proposed to represent provincial water consumption factor per unit electricity generation. An impact assessment system is proposed and impact evaluation indicator is defined to identify and evaluate the “positivity” or “negativity” of each electricity trade. The results show that total volume of virtual water transfer embodied in Chinese electricity trade in 2015 is 5638.4 million m3, in which the negative virtual water transfer is 1410.5 million m3, which comprises 25.0% of the total volume of virtual water transferred. The most positive trade pair is “Sichuan-to-Shanghai”, while the most negative trade pair is “Sichuan-to-Chongqing”. By assessing the “positivity” or “negativity” of electricity trade, this study identifies critical trade pairs that mitigate or aggravate water scarcity risk, and provide insights into improvement and optimization of national electricity trade pattern.

Water for maize for pigs for pork: An analysis of inter-provincial trade in China

Trade in commodities implies trade in virtual water (VW), which refers to the water that was used to produce the traded goods. Various studies have quantified international or inter-provincial virtual water (VW) flows related to the trade in crops and animal products. Until date, however, no effort has been undertaken to understand how the water embodied in traded feed crops (trade stage TS1) will be transferred further because of trade in animal products (trade stage TS2). This is the first study showing this mechanism, in a case study in China for maize (the major pig feed) and pork (the dominant meat), considering the period 2000–2013. We estimate the annual green and blue water footprints in maize production and then quantify the inter-provincial VW flows related to trade in maize (TS1) and trade in maize embodied in pork (TS2). Results show that in TS1, maize-related VW flowed from the water-scarce North to the water-rich South, with an increase of 40% over the study period (from 43 to 61 billion m3 y−1). In TS2, about 10% of the water embodied in maize exports from North to South China returns in the form of pork, with an increase in the absolute amount of 25% (from 4.8 to 6.1 billion m3 y−1). Considering blue VW flows specifically, we find that North-to-South blue VW flows decreased by 5% in TS1, while South-to-North blue VW flows increased by 23% in TS2.

Grey water footprint and interprovincial virtual grey water transfers for China's final electricity demands

With a Multi-Regional Input-Output analysis, this study for the first time quantifies China's final electricity demands' life-cycle impacts on water quality using the indicator Grey Water Footprint (GWF). China's Grey Water Footprint for Final Power Demands (GWFP) amounts to 37.54 billion m³ in 2010, which is the highest in the north, east and central regions. Regarding the upstream sectoral contributions on a national scale, Coal Mining and Dressing, whose GWF is decided mainly by Chemical Oxygen Demand (COD) and petroleum, and Agriculture sector, whose GWF is decided by total nitrogen discharged, contribute the largest shares of 32.40% and 23.24%, respectively. 22.28 billion m³ of GWFP is transferred across provincial boundaries as virtual grey water embodied in electricity transmissions and trades of the power sector's upstream supplies. Electric power demands in coastal provinces induce water pollution in inland provinces. For example, 1.38, 1.07 and 1.06 billion m³ of GWF in Shanxi, Inner Mongolia, and Henan, respectively, are generated to fulfill final power demands in Shandong, Jilin and Shandong. Findings in this study are significant in helping policymakers recognize and mitigate final power demands' life-cycle adverse impacts on water quality. Moreover, insights of the inter-provincial virtual grey water transfers induced by power demands enable further discussions on burden sharing and compensation in terms of power demand management and water pollution controls.

Interactive national virtual water-energy nexus networks

Across the globe, many regions import virtual resources to support their development. Although many researchers have studied transfers of a single virtual resource, interactions across two types of virtual resource transfer networks – energy and water, for example – have rarely been explored simultaneously. To address these knowledge gaps, we constructed and analyzed interprovincial virtual water and energy transfer networks, using China (the largest energy consumer and is undergoing severe water scarcity) as a demonstration. The results unexpectedly showed that more than 40% of provinces gained one kind of resource (either water or energy) through trade at the expense of losing the other kind of internal resource (energy or water), and 20% of provinces suffered a double loss of both water and energy. The remaining provinces gained both water and energy. Surprisingly, approximately 40% of transferred water/energy was from relatively water/energy-scarce provinces to water/energy-abundant provinces, further deepening resource inequality. Moreover, 33.3% and 26.7% of the provinces relied more on cross-border trade than on internal resources to support their water and energy consumption, respectively. Furthermore, in terms of total trade volume, 83.3% and 73.3% of provinces depended more on distant provinces via trade than adjacent ones to support their water and energy consumption, respectively. Overall, virtual water-energy networks tended to enhance each other. Trade largely shaped the nexus relationship between water and energy consumption in provinces. Our study suggests that there is an urgent need to assess multiple virtual resource networks simultaneously in other countries to uncover unintended consequences and to develop cross-sectoral and holistic policies to achieve global sustainability and human well-being.