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To define the complicated driving mechanisms of virtual water flow (VWF) in China's main grains production, this study firstly uses the entropy method and a K-means clustering approach to classify the driving types of VWF based on the data from 31 provinces in the mainland of China, and then applies the PLS structural equation model to analyze the driving mechanisms of VWF in four representative provinces or municipalities(Zhejiang, Heilongjiang, Xinjiang and Shanghai)selected by the classified driving types. The results show that the driving types of VWF can be divided into four types, namely, ecology-economy, ecology-environment, ecology-water use, and comprehensive type. In the four typical regions at provincial level, the social factors directly affect the VWF, and reversely it has a direct impact on the nature, environment and economy of the above four regions. In particular, the water use has a direct impact on the VWF in Heilongjiang attached to the ecologic-environmental type. The findings of this paper manifest that the social indicators rather than the indicators in water use play an important role in the VWF, that is, our findings further testify the status quo of China's VWF: the regions with rich water resources import the virtual water while the regions with poor water resources export the virtual water. Finally, for promoting the rational flow of virtual water we propose some corresponding adjustment countermeasures and suggestions that provide a theoretical basis for the rational allocation and management of water resources.

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.

In different parts of the world, a variety of initiatives are being implemented to promote water innovation. This paper explores the role of virtual incubators in fostering water-related innovations in Africa, using the case of VIA Water, a Dutch programme that promotes water innovation in African cities. Virtual incubators operate and provide their services primarily online. The results of this study confirm the additionality and disruptive nature of virtual incubators. In virtue of the gaps they are likely to fill in the innovation systems for water, these incubators can be an effective policy instrument for fostering water-related innovations in Africa. However, given their limitation to perform some functions in local innovation systems, virtual water incubators should be used along with other support mechanisms. The paper concludes that, to realise their full potential, water innovation support programmes must be locally embedded and target at least three levels: the micro, mezzo and macro levels. Only then can they attract full recognition and significantly influence the performance of water innovation systems.

This paper introduces a novel triple bottom line sustainability assessment to evaluate the water-energy-food nexus of desalination for agriculture. Falling technology costs and rising water scarcity worldwide make desalination an increasingly attractive proposition, and agriculture is one of the main sectors grappling with its potential impacts. To explore this issue, we combine a wide range of primary and secondary environmental, economic, and social data with a triple bottom line / WEF nexus analysis, to demonstrate both the holistic sustainability impacts of desalination for agriculture, and the multi-sectoral policy environment within which desalination is adopted. We apply this approach to 54 privately-owned desalination plants that treat brackish groundwater for agricultural use in the San Quintin Valley of Baja California, Mexico. We find that subsidized energy for local agribusinesses plays an important role in making desalination economically viable in the region. This in turn fuels a large agricultural export industry that represents a significant virtual water transfer to the US market. Rapid population growth in the area driven by agricultural labor needs exacerbates the issues of social equity and sustainability that these subsidies and transfers raise. We conclude with a discussion of how to manage these identified trade-offs across the water-energy-food nexus.

Water scarcity prevailing in the drylands is threatening the sustainability of livestock production systems. The water footprint (WF) indicator was proposed as a metric of water use. This study aimed to determine the WF and the economic water productivity (EWP) of 1 kg of fat and protein-corrected milk (FPCM) in eight dairy farms (n = 8; animals = 117 ± 62; area = 198 ± 127; 95% confidence level) in northern Tunisia. Then, to assess the effects of three simulation scenarios targeting the reduction of the WF of milk production (scenario A: using triticale silage to replace, on DM basis, the silage of maize, sorghum or ray-grass; scenario B: reducing by 56% the wastage of water devoted to milking, cooling, cleaning and servicing; scenario C: using concentrate feeds imported from Brazil and Argentina instead of that imported from France). A year-round monitoring of on-farm practices was performed using water-meters and recording equipment installed in key locations in the target dairy farms: (i) water used for feed production, (ii) cow watering, (iii) servicing water, (v) crop and forage production and (iv) economic and production performance were controlled by water source (green and blue). Over the eight farms evaluated, milk production consumed on average 1.36 ± 0.41 m3/kg FPCM, of which 0.93 ± 0.40 m3/kg FPCM was green water and 0.42 ± 0.30 m3/kg FPCM was blue water. However, virtual water of 1 kg FPCM averaged 43% ± 14.3%. Water used for feed production for lactating cows represents approximately 87% ± 6% of the total WF of milk production. However, drinking and servicing water contributed by 3.75% ± 2% and 9% ± 5% to the total WF of milk, respectively. The EWP assessment revealed that the selected dairy farms had a relatively small gross margin per m3 of water averaging US$ 0.05 ± 0.04. The variation in WF of milk was mainly associated with diets’ ingredients, which affected milk productivity and water consumption. Scenario analysis indicated that using feed with less water requirements or importing feeds from countries where its water consumption is low could reduce consumptive water use for milk production by up to 16%. The efficient use of servicing water could reduce blue WF of milk by up to 4%. The implementation of these measures would lead to potential total water savings in the Tunisian dairy sector of 646 million m3 per year (30%).

Virtual water flows, incorporated in global food trade has increased the last decade. The drivers and consequences are complex. These complex relations between humans and water resources are studied from different perspectives. In this article, an overview of four such perspectives on water in global food production and trade is provided. These four perspectives are: (1) More crop per drop for increasing production, (2) Less drop per crop for reducing impacts, (3) National food security and import dependency; and (4) Local values and implications of water used in export food production. Each of the perspectives is valuable in the sense of representing different value frameworks, which represent contrasting norms and convictions, belief systems, and discourses; which are often incommensurable.

Many water footprint studies have been conducted on those water scarce regions to respond their water crisis, while water rich regions also face water sustainability challenges due to inadequate water management or being virtual water exporter. Therefore, this paper tries to clarify the water footprint and detail virtual water flow features of a water-rich province, namely Yunnan province in China, to pursuit for more enlightenment for water conservation of not only water scarce regions but also water abundant regions. Multi-regional input-output (MRIO) method was adopted for water footprint and virtual water flow calculation. Results showed that the total water footprint of Yunnan was 11.35 billion m3, with 7.98 billion m3 (70%) of internal water footprint, demonstrating that Yunnan was a high water self-sufficient province. Moreover, Yunnan was a net virtual water exporter with a value of 1.18 billion m3, which was not good for Yunnan but was good for water scarce provinces. As for the detailed virtual water flow trade, high water intensity Guangxi, Hunan, Xinjiang were the top three net importers of Yunnan, while low water intensity Guangdong, Shanghai and Zhejiang were the top three export provinces of Yunnan. This did not affect Yunnan, but was not a good phenomenon for water sustainability of whole China. Moreover, agricultural sector was found to be the dominant sector for both virtual water import and export, accounting for about 88% and 86%, respectively. To maintain sustainable water management of both Yunnan and China, policy insights on keeping Yunnan as a net virtual water exporter, making use of its advantage in green water, adjusting trade structure by considering provincial water intensity were proposed.

As the headwaters region of many major Asian rivers and one of the most vulnerable ecosystems in the world, Tibet is an important strategic water resources and ecological conservation district in China. Although Tibet has developed increasing economic links with external regions, the virtual water (VW) interactions have rarely been discussed due to data unavailability. In this study, based on a newly released China multiple-regional input-output table in 2012, Tibet's local water use is analyzed by associating it with interregional-level trades in China. The structural decomposition analysis (SDA), which is conventionally applied to trace influencing factors for temporal changes of environmental variables, is adapted to examine socio-economic determinants of net VW trade in Tibet. The results indicate that Tibet is a net VW exporter, providing 577.5 million m 3 net VW to other provinces. The SDA results provide quantified effects of different factors. Tibet's low direct water use intensity and water intensive dominated export structure contribute 1048.6 and −738.9 million m 3 net VW exports, respectively. In contrast, the trade volume of commodities and production structure contribute to offsetting the net VW export 1140.7 and 69.4 million m 3 , respectively. Policies are informed towards sustainable water resources uses and management. Measures including resources use efficiency improvement, industry upgrade towards a less resource intensive production structure and material support from external regions are suggested, highlighting the importance of strengthening coordination between Tibet and downstream regions.

In the past decades, the nine major energy bases in north and west China produced increasing amounts of coal and coal-fired power to meet rapidly growing energy demand. However, the poor water resources condition has become a bottleneck for sustainable development. In this study, the water footprint of coal and power production is evaluated, and the flow of virtual water arising from the transport of energy products is quantified. The results show that total coal and power production increased continuously from 2006 to 2015. The annual total water footprint was as much as 1.29 billion m3; it showed an initially increasing trend that peaked in 2013, after which it decreased. After 2013, the water footprint decreased primarily as a result of improvements in water-saving technologies. The results also indicate that increasing amounts of virtual water (as much as 0.87 billion m3 in 2015) embedded in energy products flowed from the north and west water deficient areas to the southeast water-rich areas of China, causing severe water scarcity in the major energy producing regions. Unfortunately, based on our estimates, water stress will continuously increase during the 13th Five-Year Plan period (2016–2020). This study finds that water-saving measures alone are not sufficient to relieve the water shortage and to guarantee water security. Comprehensive countermeasures, including an adjustment to the industrial structure, the physical transfer of water, regulation of the virtual water trade and policy and planning changes, are also necessary.

The Fifth Assessment Report (AR5) of the Intergovernmental Panel on Climate Change (IPCC) has concluded that climate change will have significant impacts on global water resources. The risk of production loss due to water scarcity can be transmitted through international trade to distant economies downstream the supply chain. In this research, how climate change may affect the global economy via reducing available water resources in some regions is investigated based on a multi-regional input output (MRIO) model that provides information on the current global economic structure. Key nation-sectors with the greatest virtual water scarcity risk (VWSR) exports are identified under two climate change scenarios, including the Agriculture sectors in Syria, Pakistan, Kazakhstan, India, Uzbekistan, Iran, and China. Improving water efficiency in these sectors is essential for increasing the resilience of the global economy against climate change-induced water scarcity. Nation-sectors with the largest VWSR imports are also identified under the two climate change scenarios, including Food & Beverages sectors, Textiles and Wearing Apparel sectors, and Petroleum, Chemical and Non-Metallic Mineral Products sectors in Saudi Arabia, the United States of America, Russia, Germany, Italy, and China. These are the most vulnerable nation-sectors facing the reduction in foreign water resources due to climate change. Additionally, through comparing the change of rankings of VWSR imports, VWSR exports, and LWSRs at country and sector level, the rankings of VWSR exports are relatively close to LWSRs, while the rankings of VWSR imports are quite different from LWSRs. The evaluation demonstrates that nations should cooperatively manage water resources and be aware of the transmission of virtual water scarcity risk through international trade under climate change. Moreover, nation-sectors with high VWSR imports may reduce the reliance on water-intensive products and diversify importing sources, and national governments can encourage residents to change consumption patterns.

China faces increasingly severe water stress from its limited, unevenly distributed water resources and rapid economic growth. Interregional trade of goods and services within China further leads to a redistribution of water resources through virtual water transfers. Such virtual transfers are subject to constant changes due to the temporal variabilities in driving factors such as production efficiency, consumption patterns and population. Here we use the most recent public data to measure the water footprints of 31 provincial-level regions in China and virtual water transfers among these regions in 2012. We find that virtual water transfer plays a significant role in regional water footprints and greatly changes the allocation of water resources towards regional consumptions. Already water-scarce north China regions benefit from virtual water transfer by outsourcing water-intensive products from other regions. However, the water-scarce Northwest China suffers from virtual water transfer by exporting water-intensive products. We suggest policy makers pay attention to demand-side measures to incentivize parties to improve water efficiency in their production and reduce the consumption of water-intensive goods. Policymaking should consider economic policy and water conservation policy together to alleviate regional water stress through virtual water transfers.

Physical water consumption (PW) in economic sectors are linked with virtual water consumption (VW) embodied in the supply chain of commodities. It is important to quantitatively assess PW and VW in economic sectors and understand interconnections between them for supporting water resources management. Here, we applied an IO framework to analyse how the PW is linked to the VW from both production and consumption perspectives. A water scarce region consisting of Ganzhou, Linze, and Gaotai counties (GLG) in the Heihe river basin in China is used as a case study. The agricultural sector is broken down into seven sub-sectors represented by individual major crops. From production perspective, the results show that the agricultural sector accounted for 98.1% of total PW, which can be divided into 79.0% of final demand driven water consumption and 21% of intermediate demand driven water consumption. From consumption perspective, the VW of all the sub-sectors in the agricultural sector was largely attributed to the direct VW. The sector “Food and tobacco processing” (the downstream of the agricultural sector) has the largest indirect VW among all the sectors. Most PW in GLG was used to produce the low value added primary agricultural products to fulfil the final demand (VW) outside GLG. The results suggest that the water resources management in arid regions should guide the restructuring of economy from increasing agricultural production to increasing the economic value of the embodied virtual water, and reducing the export of the virtual water from the low economic value products.

Water depletion and pollution caused by industrialization have become major environmental concerns worldwide, which are further complicated by the urbanization and globalization. China has become an industrial powerhouse for the world, and its industrial activities-induced water pressure is no longer negligible. This study investigates China's industrial water pressure from final consumption and international export based on water footprint (WF) and dynamic structure decomposition analysis (SDA). The industrial blue and gray WFs with respect to rural consumption, urban consumption, and export are accounted for 2002–2015, and an advanced dynamic SDA model is developed and applied to examining the evolving WFs with 9 socio-economic drivers quantified. Results show that China's water resources pressure is intensified due to the increase of total industrial blue WF (by 47.4%) for 2002–2015, whereas a mitigation of water environment pressure is suggested by the decreasing gray virtual water outflow and total internal gray WF (by 31.9% and 36.4%, respectively). The SDA demonstrates that export scale and urban consumption level are two major drivers of water situation deterioration, which accumulatively contribute 38.3% and 33.0% to the evolving blue and gray WFs, respectively. In contrast, technology development is the dominant contributor alleviating China's water pressure, with absolute contribution proportions of 38.9% and 56.5%, correspondingly. Based on these, export regulation, consumption pattern adjustment and technological innovation are recommended for water policy making. The methodology used in this study can be extended to diagnosing the water issues in other nations/regions as well.

Virtual water flows have been extensively analyzed at the national level using complex network approaches. However, less is known about the regional structure of subnational virtual water flows, even though virtual water flows can vary greatly within a country. Additionally, subnational-level studies are needed since water policy and decision-making tend to be local or regional in scope. Here, we characterize and model virtual water flows for aggregated agricultural and industrial commodities at the US subnational level. Using subnational trade data for the US, we build and analyze unweighted and weighted, directed virtual water trade networks (VWTNs). To model and explore the drivers of subnational virtual water flows, we build and implement a gravity-type spatial interaction model. Using different network metrics, we find that the subnational VWTNs differ from previous well-studied networks, including national-level VWTNs. The network metrics also show a high connectivity for the unweighted VWTNs with no community structure, while the weighted VWTNs reveal spatially coherent communities of intense trade activity. The gravity model shows that the subnational weighted VWTNs are mainly controlled by distance, agricultural land, gross domestic product, and population. Despite the high connectivity of the VWTNs, the presence of community structure indicates that large volumes of virtual water are traded regionally. This suggests the possibility of having hydroeconomic boundaries that differ from known physical boundaries, e.g., watersheds and aquifers. Such boundaries could have implications for the design of consumption-based strategies for water sustainability.

Agriculture is a key sector and a major consumer of water resources; therefore, a clear understanding of the agricultural water demand for crop production and consumption is imperative for addressing water scarcity problems, particularly in water export regions. This study provides new insights into the influential factors driving the changes in the agricultural production water footprint (WFprod) and consumption water footprint (WFcon) in the net water import and net water export regions. The WFprod and WFcon of wheat are evaluated in Beijing city (the net water import region) and Heilongjiang province (the net water export region) over the period 1996–2015. The statistical significances of the influential factors, i.e., climate change, gross domestic product, population, dietary demand and technology update are determined using a multivariate linear regression model (LRM) and nonlinear regression model (NLRM). The results indicate that the gross domestic product and population were the dominant positive influential factors, whereas technology update and dietary demand were the dominant negative influential factors affecting the changes in the WFprod and WFcon in the net water import region. In the net water export region, technology update was the dominant negative influential factor affecting the changes in the WFprod and WFcon. Climate change did not contribute significantly to the changes in the WFprod and WFcon of wheat; however, it was an important factor (especially precipitation for the green WF with an average relative importance of more than 22% and the blue WF with an average relative importance of more than 15%) affecting the changes in the WFprod and WFcon of the crop. An in-depth analysis of the influential factors that contribute to the changes in the WFs is fundamentally important for decision-makers to develop countermeasures and strategic planning implementations to mitigate water resource pressure in China.

The economic, technical and strategic factors are the three most important factors in examining the cropping patterns in Iran. Iran is geographically located in a part of the planet with specific climate constraints. Drought is one of the constraints that has been a major challenge to agricultural development for many years and has always been the subject of discussions and investigations. On the other hand, constraints such as agricultural soils, economic factors, climate change, agricultural workforce, etc., multiply the production challenges in the country. Despite such constraints, planning a coherent and targeted program for the cultivation of crops and overcome the existing problems is inevitable. The present study introduced a model for optimization of regional cropping pattern decisions, which is one of the subsets of the Multi-Objective Structural Planning (MOSP) approach, and addressed different objectives, such as economic, social and environmental objectives, separately and jointly. However, it is important to address the exchange of crops in different areas in order to achieve the fundamental objectives of determining the optimal cropping pattern. Therefore, in the proposed model of optimal regional cropping pattern, issues such as the transportation of crops and, consequently, virtual water and energy exchanges were also considered. In order to evaluate the proposed model, agricultural arable lands located in the political-geographic divisions of 23 counties of Isfahan province (Iran) were selected for examination. The results showed that in the main groups of grains and forage, a significant reduction was observed in the optimal crop area of the multi-objective model by 26% and 5%, respectively. Increasing the crop area of horticultural products by 10% in the optimal pattern of multi-objective model was another important factor in the analysis of the results. In general, in order to achieve the economic, social and environmental objectives mentioned in this study within the framework of a multi-objective planning, a 16% reduction in the level of the crop area in Isfahan province is inevitable. The results of this measure are reduction in the irrigation water consumption by 17%, increase in the profit by 58% and increase in the production by 11%. Regarding the fact that in the structural planning of cropping pattern, different and sometimes conflicting objectives are considered and the compromise between the objectives is possible in the multi-objective structural planning model, the decision makers are recommended to use this model.

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.

The global water demand and supply situation is becoming increasingly severe due to water shortage and uneven distribution of water resources. The highest water demand in the energy sector is attributable to power generation. With cross-country and cross-continental power grid interconnections becoming a reality, electricity trading across countries and the creation of new opportunities for re-allocation of water resources are possible. This study expands the concept of virtual water and proposes a generalized virtual water flow in an interconnected power grid system to accurately estimate water resource benefits of clean power transmission from both the production and the consumption sides. By defining the water scarcity index as a price mechanism indicator, the benefits of water resources allocation through power grid interconnections are evaluated. Taking the Africa-Asia-Europe interconnection scenario as an example, the total water saving would amount to 88.95 million m3 by 2030 and 337.8 million m3 by 2050. This result shows that grid interconnections could promote the development of renewable energy and expand the benefits of available water resources. Keywords: Power grid interconnection, Virtual water, Water resources allocation

Urbanization, industrialization and their associated water shortage pressures have brought great challenges to agricultural development and water security. Understanding the virtual water flow involved in the grain trade is critical to ensuring water security and agricultural production. However, there are few studies on the comprehensive benefits provided by virtual water flow in the grain trade. This paper proposes a linear optimization model to fill this gap. The model is used to estimate the virtual water flow via interregional grain trade within China in 2015 and corresponding benefits to resources, the economy, and the environment from both outflow and inflow comparative perspectives. Three results characterize the virtual water flow pattern of interprovincial grain trade in China in 2015: (1) In terms of resource benefit, 31. billion cubic meters of water resources were saved, accounting for approximately 39.7% of the total virtual water flow. (2) A positive economic benefit was realized, with an increase of 6.4 trillion yuan in industrial value added. (3) Certain regions with a high crop green water occupation index account for a considerable proportion of the green water of the local agricultural ecosystem. Simultaneously, massive output of virtual water would aggravate the destruction of terrestrial ecosystems. Finally, the results suggest that promoting the marketization of water resources, improving water productivity, exploring regional compensation mechanisms and improving green water conservation capacity should be considered for water security policies.

To reflect a key aspect of global socio-hydrology, this paper explores global virtual water use from source of exploitation to sink of final consumption via interregional trades within the world economy as reflected by world input-output database for 2014. An embodiment accounting model is developed, which takes full account of virtual water feedbacks related to primary inputs. Global total trade volume of virtual water is estimated to be in magnitude around 30% of the global direct freshwater withdrawal. Moreover, it is revealed that global virtual water transfer in intermediate trade is in magnitude around 1.4 times that in final trade. In intermediate trade of virtual water, China, Japan and the United Kingdom turn out to be the three leading net importers, while India, Russia and the United States are revealed as the leading net exporters. In final trade of virtual water, the United States, Japan and Russia are the major net importers, in contrast to China, India and Mexico as the leading net exporters. Trade connections and imbalances of major economies in terms of virtual water are quantified and analyzed. Two new indicators in terms of water self-sufficiency rate by source and that by sink are devised. It is found that around 40% of the use of China’s freshwater withdrawal finally sinks into foreign economies while only 20% of China’s virtual water use originates from other regions. With regard to Germany, Canada and France, they behave like active pumps driving vast virtual water inflows and outflows, demonstrating their high involvement in the global supply chain in terms of virtual water. With the increasingly frequent virtual water transfer within the world economy, nations and regions ought to assess their behaviors in intermediate and final trades of virtual water for sustainable use of freshwater resources.

Virtual water (VW) is defined as the water required in the production of goods. The objective of the study is to quantify the temporal variation in the virtual water trade in India from the year 2006–2016 through popular food and livestock products. Water management issues need to consider the VW trade since food production consumes large amount of water. The study was carried out using the data of exports and imports of food and livestock products of India as well as their VW consumption. Through the products considered in the study 496.9 Gm 3 and 237.2 Gm3 of water is traded virtually in the form of exports and imports respectively during the period 2006 to 2016. The maximum export of VW were mainly through rice, maize and buffalo meat, while the imports were through cashews, pulses and wheat; rest of the food items contributing negligible amounts. This study will enable the water managers of the country to prioritize the export and import of products by considering the VW which will result in sustainable management of groundwater resources in India, which is already under threat due to climate change as well as degradation in quality due to geogenic and anthropogenic sources of contamination.

Changes in the patterns of regional economic and social development will affect regional agricultural and industrial structures, thereby affecting grain cultivation patterns. Imbalances between the grain supply and demand will trigger interregional grain flow. Grain is a water-intensive product, and virtual water embedded in grain products flows between regions, which will affect the utilization and distribution of regional water resources. This study evaluated the impacts of socio-economic factors on regional grain virtual water flows by using the partial least squares structural equation model (PLS-SEM). Results show that grain production centers in China are being transferred to the northern regions due to the evolution of economic patterns over the past 30 years. Driven by the imbalance between the regional grain supply and demand, the virtual water flow patterns of grain shows a tendency to flow from the northern and western provinces to the southern and eastern provinces. Results of structural equation modeling show that there is a significant causal structure between socio-economic factors and grain virtual water flows. The study indicates that the regional socio-economic pattern and its evolution will affect the grain virtual flow patterns. Consequently, virtual water flows will exert great pressure on water resources in the virtual water export areas, and the expansion of the virtual water export will increase the difficulty of regional water resources systems in supporting regional social and economic sustainable development and grain production, thus posing a potential challenge to China's water resources and grain security.

Crop yields (Y) and virtual water content (VWC) of agricultural production are affected by climate variability and change, and are highly dependent on geographical location, crop type, specific planting and harvesting practice, soil property and moisture, hydro-geologic and climate conditions. This paper assesses and analyzes historical (1985–2009) and future (2040–2064) Y and VWC of three cereal crops (i.e., wheat, barley, and canola) with high spatial resolution in the highly intensive agricultural region of Alberta, Canada, using the Soil and Water Assessment Tool (SWAT). A calibrated and validated SWAT hydrological model is used to supplement agricultural (rainfed and irrigation) models to simulate Y and crop evapotranspiration (ET) at the sub-basin scales. The downscaled climate projections from nine General Climate Models (GCMs) for RCP 2.6 and RCP 8.5 emission scenarios are fed into the calibrated SWAT model. Results from an ensemble average of GCMs show that Y and VWC are projected to change drastically under both RCPs. The trade (export-import) of wheat grain from Alberta to more than a hundred countries around the globe led to the annual saving of ~5 billion m3 of virtual water (VW) during 1996–2005. Based on the weighted average of VWC for both rainfed and irrigated conditions, future population and consumption, our projections reveal an annual average export potential of ~138 billion m3 of VW through the flow of these cereal crops in the form of both grain and other processed foods. This amount is expected to outweigh the total historical provincial water yield of 66 billion m3 and counts for 47% of total historical precipitation and 61% of total historical actual ET. The research outcome highlights the importance of local high-resolution inputs in regional modeling and understanding the local to global water-food trade policy for sustainable agriculture.

Water resources management is particularly challenging in water-scarce basins, where low water availability is combined with a potential water demand exceeding the supply capacity of the natural system. This is the case of the Segura River Basin in south-eastern Spain. This paper aims at analysing the usefulness of incorporating new hydrological data and perspectives to improve the understanding of water availability and management and help promote more integrated water planning in the Segura Basin. In this basin, agriculture amounts to approximately 1366 hm3/year and accounts for 80% of the total blue water use. The forest and agriculture use of soil water amounts to 3065 and 1962 hm3/year, respectively. The unaccounted virtual water trade is also relevant and helps in mitigating water scarcity in the basin. The basin is a net virtual water-exporting region, with an average export of 1598 hm3/year, mainly in the form of fruits and vegetables, and imports approximately 1253 hm3/year, mainly related to feed for pig farms. Virtual water imports are four times larger than the disputed water transfer rate to the Segura Basin from other river basins. Water productivity analyses by sub-sectors are useful in understanding the economic rationale of the basin activities. Two types of agriculture coexist in the basin, namely, intensive industrial agriculture and occupational farming, which maintain the territory and landscape. From a Mediterranean country perspective, the analysis recommends considering climate fluctuations and temporal variability and trends of water availability and use, moving beyond the average values considered in river basin management plans. Groundwater reserve depletion continues to occur at a rate of 231 hm3/year, as water from wells is currently cheaper than using desalinated water in farms, and it does not cause boron-related water quality problems for irrigation. If socially costly administrative measures are not taken, groundwater reserve depletion will continue. The project 'Análisis académico del Plan Hidrológico de la demarcación hidrográfica del Segura 2015-2021 a la luz de modernos conceptos de la ciencia de los recursos del agua' (Academic analysis of the Segura Water District Water Plan from the point of view of water resources modern concepts) provided the ideas and data for this work. This project has been carried out by the Royal Academy of Exact, Physical and Natural Sciences of Spain with the support of the Segura Water Authority , the Botin Foundation , Obra Social La Caixa and Caja Navarra Foundation . Many experts have contributed to its development, and all of them are credited in Aldaya et al. (2017) .

Food and water are inextricably linked. With the increase of water consumption in irrigation and food growth, water shortage has become an urgent issue. Irrational cross-regional transfer of water embodied in food exacerbates water scarcity and restrict China's sustainable development. Given that, a Virtual Water-Food Nexus Model is developed to quantify the inter-provincial transfer of water embodied in food and to identify the complicated interactions between different provinces. In detail, Environmental Input-Output Analysis is applied to quantitatively estimate the inter-provincial water transfer embodied in food trades. Based on the network constructed by interrelated nature of nexus, the mutual interactions, control situation, and the dominant and weak pathways are examined through the combination of Ecological Network Analysis and Principal Component Analysis. Two new indictors water consumption intensity and water supply capacity are first performed to measure the role of each province from the supply and consume side respectively. It is revealed that interregional food transactions failed to realize water resources dispatching management. Many water-deficient regions suffered from massive virtual water losses through food exports, but water-rich areas still import large quantities of food containing virtual water. Results show that exploitation and competition dominate the ecological relationships between provinces. Agricultural GDP ratio is the indicator which most affect water consumption intensity and water supply capacity. Network-based research contributes more insights into the recognition of water management responsibilities across provinces and municipalities. These findings will provide a scientific support to adjust unreasonable allocation of water resources in China in an attempt to addressing the contradiction between food demand and water shortages.

Energy and water are important resources for sustainable development. Due to large amounts of demand in the energy production, water is becoming a critical factor for energy policy making, especially for resource-dependent areas. Direct users from the production-based method and indirect drivers from the consumption-based method are identified in existing studies, but transmission sectors in the intermediate supply chains are usually ignored. To reconcile the relationship between energy and water, we carry on a case study in Shanxi Province and use input-output tables in 2007 and 2012 to measure the betweenness of sectors. Results shows that Mining and Processing of Metal Ores is the key transmission sector measured by betweenness-based method but usually ignored by other existing methods. Moreover, tertiary industry, such as Transportation, Storage and Posts, Hotel and Restaurants, plays an increasing significant role as transmission centers in the upstream supply chains. Efficiency improvement in these sectors may also help reduce water stress in the energy production. To encourage better decisions and avoid unintended results, betweenness-based results should be considered as a complementary part for energy and water policy formulation.

Importing food products is associated with the simultaneous transfer of virtual water required for the production of these products. This reduces water resource depletion in the importing country and offers water and food security. The objective of this study is to quantify the water savings and water losses due to virtual water import by India from 1986 to 2013 based on 203 products. Long-term average virtual water import from partner countries is 20.2 Bm3/y. Crop products consume the largest portion of imported virtual water (17.7 Bm3/y) followed by industrial products (2.4 Bm3/y). Livestock products contribute a smaller amount to virtual water import (0.1 Bm3/y). If these products were produced in India instead of being imported, India would have used 31 Bm3/y of its water resources. Thus, the import of products by India leads to 10.8 Bm3/y of global water savings. Importing products from Africa leads to global water losses and most virtual water is saved due to import from South America. Based on the water saved/ lost, the trade partnership of India with partner countries could be classified as mutually beneficial, partially beneficial, unsustainable and pressured. India can amend its trade relations with the partners based on this classification. India’s trade with other countries should consider the water availability in the exporting countries and the comparison between the virtual water required to import the products and to self-produce. Only such a balanced approach can help to sustainably manage the global and national water resources. The present study, however, targets only on the virtual water imports of India and the strategies that the nation could adopt from its own perspective. In order to develop a policy framework, the virtual water export of India should also be considered.

Efficient-equitable-ecological (3E) regional water resource coordination that includes virtual water is critical for long-term sustainability. This paper develops a methodology for a comprehensive 3E evaluation of regional water resource coordination, in which both visible and virtual water are considered in the indicator system. Experts’ opinions towards indicator importance are expressed by hesitant fuzzy numbers. By using hesitant fuzzy linguistic judgments, the flexibility of expressions is increased. A minimized divergence and hesitant degree model is established to calculate the experts’ weights. Then to determine indicators’ weights, a weighted average operator is used. To aggregate the final evaluation results, a TOPSIS method is adopted. The presented methodology is applied to the water resource coordination evaluation in the Northwestern District of China. Based on the evaluation results, some suggestions are proposed to enhance the water resource coordination in the study area. Finally, to illustrate the effectiveness of the proposed methodology, the method is compared with the equal weights method.

Rationalization of water quality monitoring stations nowadays is applied in many countries. In some cases, missing data from abandoned/inactive stations, spatial and temporal, could be very important, hence the use of artificial neural networks (ANNs) for virtual water quality monitoring at inactive monitoring sites was investigated. The aim was to develop single-output and simultaneous ANNs for the spatial interpolation of 18 water quality parameters at single- and multi-inactive monitoring sites on Danube River course through Serbia. Those different modeling approaches were considered in order to determine the most suitable combination of models. The variable selection and sensitivity analysis in the case of simultaneous models were performed using a modified procedure based on Monte Carlo Simulations (MCS). In general, the multi-target models tend to be more accurate than single target ones, while single output models outperform the simultaneous ones. Hence, for particular monitoring network and set of water quality parameters the optimal combination of models must be defined based on model's accuracy and computational effort needed. The MCS selection procedure has proved to be efficient only in the case of simultaneous multi-target model. MCS based analysis of input-output interactions has shown all significant interactions in the case of simultaneous single-target are grouped as a complex duster of interactions, where majority of inputs influence on several outputs. In the case multi-target model those interactions were portioned in five separate clusters, there majority of them mimic the input-output interactions that are present in single output models. The modeling strategy for study area was proposed on the basis of the performance of created models (mean average percentage error lt 10%): simultaneous multi-target model for pH, alkalinity, conductivity, hardness, dissolved oxygen, HCO3-,SO42- and Ca, single-output multi-target models for temperature and Cl-, simultaneous single-target models for Mg and CO2, single output single target models for NO3-.

The virtual water concept has a considerable potential to help improve the productivity of limited fresh water resources especially in the agriculture sector. Iran is the biggest producer and exporter of Saffron in the world. This research explores the average magnitude and share of water footprint components, including the green, blue, grey and white water footprints over the period of 2008–2014 in the provincial and national levels. The average water footprint of the Saffron production in Iran was 4659 m3 kg−1. The share of green, blue, white, and grey water footprints are estimated as 12, 42, 40, and 6 percent, respectively. The total water footprint of Saffron production was around 1541 MCM yr−1 that the share of exported virtual water was 1354.6 MCM yr−1. The average economic water footprint of Saffron production is 3.1 m3 per $. Lorestan, East Azerbaijan and Isfahan have the lowest economical water footprint while Chaharmahal and Bakhtiari, Semnan and Fars have the highest values. The results of this research provide valuable information for managers and policy makers to extend the cultivation area in regions with low economical water footprint and also the regions with rain-fed cropping and sufficient precipitation. In contrast, increasing yield and water use efficiency in regions with high economical water footprint is very necessary.

Rapid urban growth in sub-Saharan Africa challenges food supply of cities. As food and other organic matter are transported from production areas to consumption points, water, which has been used for their production, is transported virtually. This study aimed at determining the magnitude and sources of virtual water flows in food trade of two West African cities, in order to better assess food provisioning risks and water resource use and planning. To this end, flows of unprocessed food from local, regional, national and international sources were systematically recorded at all roads leading to Tamale, Ghana and Ouagadougou, Burkina Faso. The survey was conducted within two years covering the peak (November - December) and lean season (March - April), respectively, for six days in a row. Virtual water flows were computed by multiplying the flow quantities (t yr−1) by their respective virtual water contents (m3 t−1). Results showed that virtual water of all food commodities imported to Tamale and Ouagadougou were 514 and 2105 million m3 yr-1 respectively, out of which 68% and 40% were re-exported to other regions of the country. The data also showed major seasonal variation in virtual water flows across the year. Reflecting their dominating role in local diets, cereals contributed most to the total virtual water inflows in both cities. Southern Ghana is the major net virtual water importer from Tamale through cereals, legumes, vegetables, and livestock. The Northern Region of Ghana, on the other hand, is a net exporter of virtual water in all food groups apart from fruits. In Ouagadougou, large flows of virtual water were imported in cereals, specifically rice from Asian countries, via Ivory Coast.

Coal-fired electricity industry is the high-water-consumption sector and the coal and electricity trade among different regions drives virtual water flow which embedded in the coal and coal-fired electricity products. In North China regions, a large amount of water was consumed by coal and electricity products, and transferred to the South China in terms of virtual water. This study calculated the water footprint of coal and coal-fired electricity products in seven regions all over China and established a theoretical system to analyse the virtual water flow regime associated with the coal and electricity trade. Besides, a map of the virtual water flow in China is drawn. The results show that the water footprint of the energy industry in the Eastern and North-western regions is much higher than that of other areas, the water footprint in 2015 is 2.4×109m3 and 3.2×109m3, which is mainly due to the large demand for electricity production in the Eastern regions. And the Northwest region is rich in energy resources, which require large amount of water resources for coal mining and electricity generation. However, in the recent years, the Northwest regions are the highest output of virtual water regions, from 3.7×108m3 in 2000 to 8.6×108m3 in 2015, accounting for 35% of the water footprint of the coal power industry in the region. There is almost no out-flow virtual water in the Eastern and Southern regions. The virtual water of water resources in water-scarce regions is transported to the water-rich regions, which will lead to larger pressure on the water resources in the Northwest region. Therefore, the physical water transfer (e.g. South-to-North Water Diversion Project) is not only the efficient measure to cope with the water issues related to energy production, and the virtual water regulation is also an efficient way for sustainable water management in the future.

With active interprovincial economic trade, water resources embodied in economic goods and services are also transferred. In China, water resources are uneven spatial distributed and many regions are facing serious water shortage. As the spatial mismatch of water resources and water consumers, provincial water shortage risk are changing by transferring in or out water resources in wetter regions or drier regions. In this study, we constructed a water shortage risk trade model to assess one region’s (sector’s) potential economic output reduction induced by its economic trade partners’ water shortage. Take Northeast China (including Heilongjiang, Jilin and Liaoning province, namely HJL region) as a case study, we figured out the provinces that have larger risk on HJL region’s sectoral economic output and the main provinces influenced by HJL region’s water shortage. Finally, we analyzed the water shortage risk transfer among sectors in HJL region. The results show that risk from HJL region is mainly transferred to coastal regions and a large quantity of virtual water shortage risk (VWSR) are transferred among sectors in this region due to the intensive trade activities within this region. Water shortage in Heilongjiang transferred larger risk to other provinces than Jilin and Liaoning, while vulnerability index of Liaoning is higher than Heilongjiang, Jilin, which is vulnerable to water shortage in Heilongjiang, Jilin and Beijing. This study can provide insights for local water security management through identifying the key provinces and trade pathways to reduce water risk and avoid water risk transferring to improve the intersectoral and interprovincial water coordinated management for achieving national water sustainable supplying.

Massive amounts of water and land embodied in crops are transferred via food trade. This study established a network-based framework for the water–land nexus in food trade to investigate the spatial linkages of water, land, and food. Based on the gravity model and linear programming optimization, the food trade model was first built to simulate crop trade. Then water consumption and land use for various crops in different regions were inventoried to establish the food-related virtual water network and food-related virtual land network. Grey water related to water quality, blue and green water related to water quantity, were incorporated into the food-related virtual water accounting framework to identify the role of food trade in the spatial reallocation of water. Similarly, the food-related virtual land network was built based on the land use for different crops and the food trade model. Finally, a case study was conducted using ecological network analysis to analyze the properties and connections within the food-related virtual water/land networks of China. The results showed that the green and grey water consumption associated with food production, the effects of which have previously been neglected, account for a huge proportion of the total water consumption, especially in water-scarce provinces. The controllers/dependents in the networks that have strong control relationships with other provinces were identified. The proposed network-based framework for the water–land nexus may help boost synergies associated with spatial reallocation of water and land via food trade and explore pathways for sustainable management of water, land, and food resources.

The irrational virtual water flow caused by grain trade makes water use efficiency low and further threatens grain security in China. However, optimizing the grain virtual water trade flow from the perspective of the economic value of water resources has rarely been carried out in current research. This paper proposes a linear optimization model considering opportunity cost to fill this gap. The current situation of grain virtual water trade is analyzed and we find an irrational trade mode which quantity and direction of grain virtual water trade in some provinces are not consistent with actual demand. Then, opportunity cost is added to the linear optimization model to adjust grain virtual water trade which shows several advantages compared to general linear optimization model. Results show that huge virtual flow is generated, up to 1179.24 billion cubic meters of water. And the economic value generated by grain virtual water trade can not only cover the transportation cost but can also eventually generate economic benefits of 7410 billion yuan. Finally, the relevant conclusions and implications of adjusting China’s grain virtual water trade are obtained.

In this paper, a mathematical model for conflict resolution among a diverse set of agricultural water users in Golestan province, Iran, is developed. Given the bi-level nature of the distribution of power in the current problem, a combination of Leader–Follower game and Nash–Harsanyi bargaining solution method is employed to find optimal water and crop area allocations. The Golestan Regional Water Authority is the leader in this setting, controlling the total water allocations; and the agricultural sectors are the followers, competing over the allocated water. Two objectives for the leader are (i) maximizing profits, and (ii) maximizing share of green water in total agricultural production through selecting more efficient crop patterns. The followers’ objective is merely maximizing obtained benefits for the selected crop patterns. Virtual water concept is also factored into the related objective functions, and the water allocation problem is solved considering spatio-temporal crop pattern along with a dynamic water pricing system. This involves using a hybrid optimization structure as a new approach to solving two level optimization problems. The results show that the leader’s income is independent of total water allocation and is only affected by crop pattern and crop area, two factors which drive water price too. The followers’ benefit also depends on crop pattern and crop area, as they influence the crop yield, cost and water price. Finally, green water plays a key role in selecting the optimal crop pattern and crop area.

The mitigation of water stress in crop production is important for relieving the growing global water shortage. The water footprint scarcity (WFS) for regional water stress evaluation integrating blue and green water resources and the water footprint of the crop production industry were developed in this paper. Three subregions in China, industry-based southern Jiangsu (SJS), agriculture-based northern Jiangsu (NJS) and middle-type central Jiangsu (CJS), were selected to study the spatiotemporal pattern and driving mechanism of WFS. The results show that green water accounts for 56.6% and 71.8% of agricultural water resources available (AWA) and crop water footprint (CWF) of Jiangsu Province. The WFS of Jiangsu was calculated to be 2.26, and almost all prefectures for every year from 1996 to 2015 faced very high water stress (WFS > 1.20). The WFS value increased in NJS and CJS and decreased in SJS over time; meteorological and social factors affected the WFS at the same time. Land irrigation was the main factor to explain the growing water stress in the agriculture-based NJS. The WFS revealed the water shortage more clearly, especially in the water-poor agriculture-based areas, than the results of the conventional water stress index. The strategies for environmental change adaptation suggested by this study are to use WFS for agricultural water suitability evaluation and water resource management policy formulation; to reduce WFS through irrigation efficiency and crop variety promotion worldwide; and to implement compensation measures for agricultural products and virtual water trade to help underdeveloped agricultural production areas improve their agricultural production technology and control irrigation expansion.

Do virtual, yet informal and synchronous, interactions affect individual performance outcomes of organizational newcomers? We report results from a randomized field experiment conducted at a large global organization that estimates the performance effects of “virtual water coolers” for remote interns participating in the firm’s flagship summer internship program. Findings indicate that interns who had randomized opportunities to interact synchronously and informally with senior managers were significantly more likely to receive offers for full-time employment, achieved higher weekly performance ratings, and had more positive attitudes toward their remote internships. Further, we observed stronger results when the interns and senior managers were demographically similar. Secondary results also hint at a possible abductive explanation of the performance effects: virtual watercoolers between interns and senior managers may have facilitated knowledge and advice sharing. This study demonstrates that hosting brief virtual water cooler sessions with senior managers might have job and career benefits for organizational newcomers working in remote workplaces, an insight with immediate managerial relevance.

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.

Currently, agriculture uses about 70–80% of global water resources and, in the Mediterranean area, it accounts for the high pressure of freshwater demand. This study provides a useful framework for the meso-level assessment of the Water Footprint (WF) in agriculture. Particularly, the WF methodology is used to quantify the water consumption and pollution of olives, grapes and tomatoes, traditional crops widespread both in the Apulia region, in Southern Italy, and in the Mediterranean area. Hence, from a meso-level assessment of the Water Footprint of Apulian agriculture, a general level of evaluation of the use of Mediterranean water resources was provided, estimating the Virtual Water (VW) too. Furthermore the climate change effects on the Water Footprint of the traditional crops identified were predicted, proposing some scenarios useful to reduce the grey component, which values for olives were evaluated by a sensitivity analysis. The results highlight that olives present the highest value of the WF and that grapes are the most affected by the variations according to the climate change scenarios, increasing over 200% of the green component and 77% of the blue one. Finally, a Circular Economy proposal, based on the reuse of the wastewater from a meso-scale perspective, highlights saving up to 70% of the water resource. The research questions proposed displayed the novelty of this paper, particularly as concerns the use of the Water Footprint analysis on a meso-level evaluation. Particularly, the new insights of this research addressed the needs of stakeholders in areas suffering from drought, such as the Mediterranean, to integrate and systematize a data-set of indicators to rationalize and plan water resource usage and safety in agriculture.

A great amount of electricity generation exerts a tremendous pressure on China's water resources. The spatial mismatch between primary energy and water in China aggravates the pressure of water resources and results in virtual water transfers from drier to wetter regions through electricity trade. Firstly, we construct an electricity generation-consumption (EGC) model to model inter-provincial electricity trade in China and propose a hybrid virtual water intensity (HVWI) indicator to represent the provincial overall virtual water consumption factor. Then, we combine the inter-provincial electricity trade and the provincial HVWI to build China's virtual water trade network. The results show that total inter-provincial virtual water embodied in the electricity trade is 5637 GL. The top three largest electricity trade flows are Yunnan-to-Guangdong (111 billion kWh), Inner Mongolia-to-Beijing (32.7 billion kWh) and Inner Mongolia-to-Liaoning (31.1 billion kWh), and the top three largest virtual water flows are Yunnan-to-Guangdong (1527 GL), Sichuan-to-Chongqing (432.6 GL) and Sichuan-to-Shanghai (418.7 GL).

With growing populations and climate change, more regions around the world are prone to unprecedented water scarcity. The concept of virtual water is introduced in the Middle East, where one of the strategy to solve water scarcity is to import grain instead of grow grain locally. However, some researchers have argued that such virtual water strategy as a solution to water scarcity is fallacious failing to take regional socio-economic and environmental suitability into account. In this study, an evaluation index system of virtual water strategy was constructed from an integrated water–ecosystem–economy system perspective. The evaluation index system can reflect the co-relationship among water, ecosystems and the economy and the status of system, which consists of resources, technology, economy, society, and environment. Using the improved entropy weighting and fuzzy synthetic evaluation methods, regional suitability of virtual water strategy was assessed and classified into the following five grades: excellent, good, average, fair, and poor. Using the Heihe River Basin (HRB) as the case study area, the evaluation index system was applied to examine the regional suitability of virtual water strategy for each county in the river basin. Results showed the suitability degree of approximately half of the counties was ‘excellent’, while the other half was ‘average’, except for Jinta County whose suitability of the virtual water strategy was ‘poor’. The results indicated that the suitability of the implementation of virtual water strategy is closely related to the economic development and ecological conditions. In addition, the study propels the evaluation of virtual water strategy, and enhances their persuasion in addressing water scarcity, identifying the feasibility in the arid and semi-arid regions worldwide.

At present stage, there is increasingly desperate contradiction in China’s water supply and demand. Importing virtual water by the import of agricultural products (industrial products) from other countries may be a possible way to alleviate it. Based on the Input-Output Table and relevant data in using water resources, this paper accounts China’s virtual water trade volume in 2012 systematically and does a research on industrial linkage effect of China. Results show that: (1) There is a net export of virtual water in China in 2012, while there is a large amount of net import of virtual water in agriculture. (2) The linkage between agriculture and the other industries has great influence on both imports and exports volume of china’s virtual water. After extraction, the virtual water imports volume only accounts for 66.33% of that before extraction; at the same time, the virtual water exports volume only account for 49.00% of that before extraction. Among them, the linkage effect between food production and tobacco processing industry and agriculture is the largest. The result shows that there is a certain degree of failure of virtual water trade strategy to relieve the contradiction of supply and demand of water resources through the virtual water net imports. Therefore, it is necessary to expand agricultural imports appropriately which requires more water consumption and moderately reduce agricultural exports. At the same time, we should consider the linkage effect between agriculture and other industries, and synchronously adjust the import and export of other industries, especially the food production and tobacco processing industry.

To analyze the water security status and propose the countermeasures, this study calculated the total water consumption of the energy products focusing on coal mining and coal-fired electricity generation and explored the changing characteristics of the total water footprint in the period of 2006-2015, and also revealed the virtual water flowing patterns embedded in coal and electricity transfer among different regions of China. The results show that the annual total water footprint of coal and coal-fired electricity is as much as 1.05 billion m3, accounting for 22.8 % of the total fresh available water resources in the nine energy bases. The total virtual water flowing out of the nine energy bases embedded in energy product trade is keeping increasing in the period of 2006-2015, with the growth rate of 3.03×107 m3/a. In 2015, the total virtual water flowing out is as much as 9.57×108 m3, accounting for 81.2 % of the total water footprint of coal and electricity in the nine bases. And the water stress indices in the above nine bases are also showing an obvious increasing trend in the past decade. Coal and coal-fired electricity production consume much water in the arid and semi-arid energy bases, which poses great negative impact on the local water system and ecosystem. To control the water consumption of energy sector, improve water using efficiency and adjust the industrial structure should be continuously implemented in the future.

In this paper we draw on a unique dataset of hydrological and microbiological time series to apply water footprint (WF) methodology to quantify the environmental impact of cattle grazing on karst area in a regional park of the southern Apennines (Italy). The use of WF methodology in the same specific environment where relevant data are monitored, and the hydrogeological and microbiological characterisation of the study area, validate the results of our WF assessment, that can be summarised as follows. First, we show that an ecological indicator such as the grey water footprint (GWF) may be of particular relevance to the park authority to implement policies to preserve groundwater quality. Second, we introduce a new metric, referred to as the environment-related grey water footprint (GWFenv), to estimate the virtual water needed to absorb the microbial pollution of a cattle grazing process.

Tunisia is prone to serious depletion of water resources that is threatening the sustainable agriculture development especially the livestock sector. The current study aimed to measure water footprint (WF) and economic water productivity (EWP) of sheep meat within twelve smallholder farms in two different agro-ecological zones in Tunisia; humid in northern and semi-arid in central Tunisia. A year-round monitoring of on-farm practices was performed using water meters and recording equipment’s installed in key locations in the target sheep farms. The water source green (rainwater) and blue (from irrigation) corresponds to (i) water used for feed production, (ii) sheep watering, (iii) cleaning and servicing water, (v) water used for crop and pasture yield production, and (iv) economic and production performance. Results show that farms in semi-arid region have the highest WF averaging 9.07 ± 0.48 m3/ kg sheep body weight (BW) of which 8.58 ± 0.46 m3/kg BW was green water and 0.49 ± 0.05 m3/kg BW was blue water. The lowest WF values were recorded in farms in humid region averaging 6.98 ± 0.3 m3/kg BW out of 6.79 ± 0.27 m3/kg BW was green water. Around 17.3% of the total WF of sheep meat was attributed to virtual water from off-farm feed production in farms in humid region. However, in farms in the semi-arid region, the proportion of off-farm feed exceeds 65% and they are imported from international markets or produced in northern region. Most of the total volume of water (99%) refers to the WF of feed production. Drinking water, service and cleaning water account only for less than 1%. The assessment of the EWP revealed that farms had an average gross margin per m3 of water of 0.49 ± 0.1 US $ and US$ 0.29 ± 0.04 in humid and semi-arid regions, respectively. The current results confirm that producing sheep meat in humid region is 20% more efficient in term of water use and create 60% more gross margin return per m3 of water than in semi-arid region. In addition, semi-arid region is more prone to the impact of climate change that humid region. Moreover, rangeland degradation coupled with the high density of sheep flocks in the semi-arid region, mean that farms in the humid region would profit more from sheep rearing.

Water consumption in thermoelectric and hydropower plants in China increased from 1.6 and 6.1 billion m3, respectively, to 3.8 and 14.6 billion m3 from 2002 to 2010. Using the concept of virtual water, we attribute to different electricity users the total water consumption by the electric power sector. From 2002 to 2010, virtual water embodied in the final consumption of electricity (hereinafter referred to as VWEF) increased from 1.90 to 7.35 billion m3, whilst virtual water in electricity used by industries (hereinafter referred to as VWEI) increased from 5.82 to 11.13 billion m3. The inter-provincial virtual water trades as a result of spatial mismatch of electricity production and consumption are quantified. Nearly half (47.5% in 2010) of the physical water inputs into the power sector were virtually transferred across provincial boundaries in the form of virtual water embodied in the electricity produced, mainly from provinces in northeast, central and south China to those in east and north China. Until 2030, VWEF and VWEI are likely to increase from 5.27 and 14.89 billion m3 to 7.19 and 20.33 billion m3, respectively. Climate change mitigation and water conservation measures in the power sector may help to relieve the regional pressures on water resources imposed by the power sector.

Agriculture is the main consumer of freshwater in the world. The paper described the process of virtual water content and flow in crops. Differences in climatic conditions of different regions in China result in large differences in water consumption during crop growth. The virtual water trade in crops connects water flows within and between regions, linking the actual water consumption with the invisible water trade as a whole. The objective of the paper was supplying the agricultural products virtual water trade evaluation system, determining quantitatively the virtual water flow within the region & regional. Using meteorological and agricultural data from 2003 to 2010, a comprehensive analysis of China's domestic & international virtual water trade of agricultural products has been undertaken. The virtual water for the three primary crops and virtual water trade are discussed. The virtual water content of grain crops in northern & southern China was 1293 m3/t & 942 m3/t, respectively; the national average value was 1117 m3/t; and the regional differences in virtual water content for each crop were significant. China's inter-regional agricultural products virtual water trade was not consistent with water resource endowment expectations. The transfer of crops from northern to southern regions would have a significant impact on the sustainable utilization of water resources and would exacerbate water resources shortages in northern regions. China had a trade surplus in global virtual water trade of agricultural products. The exported agricultural products virtual water amounted to 31.5 billion m3/yr., and the imported amount was 145 billion m3/yr. The net import of virtual water embedded in agricultural products increased from 44 billion m3/yr. in 2003 to 178 billion m3/yr. in 2010. It is further concluded that the trend for agricultural products total virtual water, green water, and blue water is that China is increasing its imports year on year. A large increase in imports of agricultural products has led to a decline in the rate of self-sufficiency in domestic agricultural production. The paper provided the basis for the comprehensive evaluation of crop planting structure adjustment, grain import & export, and the potential of regional water resources development and utilization.

The issue of water access and security has been emphasized in the recent policy debate on sustainable development (Sustainable Development Goal No. 6) and adaptation to climate change (CoP21 in Paris, 2015). This study provides new evidence about the Blue Virtual Water Input-Output Network. The main novelty of our approach is the combination of Structural Decomposition Analysis (SDA) with Network Theory. SDA reveals that size-related, technological and structural components have contributed substantially to changes in virtual water use. Network analysis offers new insights about the vulnerability of the system to shocks through trade links across country-sector pairs. Our analysis highlights a possible trade-off in the increasing importance of virtual water trade: the efficiency improvement in granting access to virtual water might come at the cost of increasing systemic vulnerability. Overall, the great unbalance between water availability and usage combined with rigidity of global consumption and production networks and the risk of cascade effects imply increasing vulnerability of the virtual water network to shocks propagation.