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Agricultural water productivity is crucial for sustainability amidst the escalating demand for food. Cereals are pivotal in providing nutritious food at affordable prices. This study was based on Ghanaian data spanning from 1992 to 2021 to evaluate water usage in the cultivation of major cereals. It also examined the virtual water losses or gains in cereal trade alongside influencing factors. The analysis utilized secondary data encompassing the virtual water content, production quantity, export and import quantities, distance, GDP per capita, population, and land per capita of Ghana and its 75 trade partners. In the last 5 years, crop water use (CWU) reached an average of 7.08 billion m3/yr for maize, 3.48 billion m3/yr for rice, 1.08 billion m3/yr for sorghum, and 0.63 billion m3/yr for millet production. Ghana’s major partners for exported virtual water (EVW) were Niger, Burkina Faso, South Africa, and Togo. Major partners for imported virtual water (IVW) were Argentina, South Africa, Ukraine, Togo, Russia, Burkina Faso, Canada, Senegal, Nigeria, Portugal, UK, Niger, and the USA. The Panel Least Squares Method of regression was used to apply the Gravity Model principle in assessing influencing factors. The findings indicate that Ghana is a net importer of virtual water in the cereal trade, with significant influences from geographical distance, GDP per capita, population, land per capita, and cereal water use.

Given the need for water use to be a crucial consideration in sustainable development, an adequate water allocation system across economic sectors is essential, especially in the face of increasing seasonal and perennial water scarcity. In an attempt to facilitate a socially and economically efficient adaptation to the climate emergency, we propose a set of eleven socio-economic indicators to analyze the current water management. This set of indicators could help to quantify the interrelationship between water use and its economic perspective, as well as its social perspective through its impact on employment. Any demand for water not only includes the direct use of water but also its indirect use, referred to as virtual water. This is the water indirectly used through the other inputs in the production process (input–output methodology). These indicators are evaluated in the South-West Europe territory where, in light of increasing water scarcity, there is a need to orientate water allocation toward employment with less intensive water use, to more water productivity and to less environmental impacts. The results at river basin scales show that water use is more productive in the tertiary than in the secondary and primary sectors.

Agricultural trade, which involves the exchange of virtual water and land resources, can effectively regulate the allocation of resources among countries while enhancing the well-being of resource-rich and resource-poor nations. China’s animal products trade market concentration is greater, and the livestock industry consumes more water than other agricultural sectors. In order to alleviate the pressure on China’s domestic water and land resources and to ensure that Chinese residents have access to animal products, this article examines the trade situation and drivers of virtual water and land resources related to Chinese animal products trade. This study used the heat equivalent method to measure the virtual water and land flows of the import and export of beef, pork, and mutton from 1992 to 2018, which is followed by the gravity model to investigate the factors impacting China’s flow of virtual land and water related to livestock products trade. We found that the economic development and the agricultural resources of exporters, as well as China’s agricultural employment rates, have a stable beneficial impact on China’s livestock imports. The population of importing nations, China’s cultivated land area, and the livestock production index of importers and exporters have a positive impact on the export of livestock products from China. Our results remain robust following a series of additional tests.

Virtual water exerts an essential effect on water resources, yet such effect is rarely considered in current studies on water rights allocation in transboundary rivers. Hence, this paper ran a case study on Taihu Lake Basin, collecting data from 2017 to make clear the physical water rights of four regions—Jiangsu Province, Zhejiang Province, Anhui Province, and Shanghai City—in the Basin. After that, the multiregional input–output (MRIO) approach was utilized to measure the trade in value-added (TiVA) transfer and virtual water transfer (VWT) and construct an inequality index of VWT (VWI). Next, water efficiency coefficient was employed to convert the VWT into riparian level. Finally, VWT and VWI were incorporated into the water rights allocation model to form up a water rights allocation scheme for Taihu Lake Basin. Results showed: (1) Jiangsu enjoys the most allocated physical water rights, followed by Zhejiang, and Anhui ranks the lowest; (2) Anhui and Jiangsu are net virtual water exporters (2.259 billion m3 and 1.78 billion m3, respectively), while Zhejiang and Shanghai are net importers (2.344 billion m3 and 1.695 billion m3, respectively); (3) Anhui suffers the most inequality—0.4401—followed by 0.5076 of Jiangsu, while Zhejiang has the most equal environment—0.7012; (4) after the inclusion of virtual water, the quantity of water rights allocation changes, whereas Anhui experiences the largest growth—144 million m3—due to the dual effects from the highest VWT and inequality. In conclusion, the effect of virtual water is indispensable, so VWT and VWI should both be considered in the physical water rights allocation of transboundary rivers.

To achieve food security goals, water accounting seems to be one of the most powerful tools to deal with water scarcity management. Thus, indicators, such as virtual water and water productivity, can be considered complementary rather than competing indicators to assess water demand efficiency use. Water computation is, therefore, a crucial tool to understand the overall tendency of water consumption and to assist the decision makers in their decisional process about water efficiency use in different phases of production. In this perspective, this paper aims to evaluate water use throughout the value chain of the olive oil sector, which is the first strategic agro-industrial sector in Tunisia. This evaluation will be undertaken while taking into account various crucial issues concerning the main two production phases in terms of the importance of water consumption (agriculture and processing phase). In the agriculture phase, the rainfed and irrigated modes will be compared, and in the processing phase, three different processing systems will be evaluated. Thirty surveys with farmers and nine surveys with olive oil mill owners were undertaken in the arid region of Sfax: one of the most important olive oil producers in Tunisia. The results show the importance of the theoretical framework adopted in clarifying the state of water consumption in a strategic sector, such as the Tunisian olive oil sector. In addition, the different calculated indicators highlight the importance of the application of a whole technical package and a controlled and efficient use of water to improve the economic profitability and the necessity to revise the irrigated olive growing extensions’ policies under arid conditions. In addition, in the processing phase, the continuous-two phase system is emphasized as the most relevant system in terms of water efficiency use. This system is proposed to be encouraged by policy makers in future olive mill installations.

As a water-scarce country and the world’s largest trader of industrial products, China’s industrial virtual water (VW) flow may exacerbate its water scarcity problem. Thus, industrial VW flows’ spatial and temporal evolution in international trade should be analyzed, and influencing factors must be identified. This study developed the multiregional input–output (MRIO) model, combined with the Leontief inverse matrix, to measure and decompose the industrial VW flows between China and other economies from 2000 to 2014. This extended MRIO model considers intermediate production water consumption and indirect water use, which technically distinguishes the sources of pressure on water use more accurately, thus enabling a new elaboration of the composition of China’s industrial water use. Then, the evolution of China’s industrial VW trade is analyzed spatiotemporally, and the structural decomposition analysis (SDA) method is invoked to identify the endogenous drivers further. The results indicate the following. (1) China was a net exporter of industrial VW trade. The main VW export sectors in China were the manufacture of textiles and wearing apparel, paper products, and chemical products, which had the characteristics of high water consumption, high pollution, and low added value, respectively. (2) The net exports of industrial VW from China mainly went to the US, EU, ROW (rest of the world), and Japan. China’s VW exports to the US and Japan are declining, while exports to the EU and Russia are increasing. (3) The decrease in the water-use coefficient in all industrial sectors in China was the most critical reason for inhibiting the increase in the country’s industrial VW exports. The export structure effect of intermediate products, product structure effect of foreign final demand, and scale effect of foreign final demand were the primary reasons for the rise in VW exports, but all gradually diminished. Moreover, the structural effects of China on the use of domestic intermediate products had a significant positive effect on the increase in VW exports. In contrast, those of foreign products had an extremely weak effect.

Due to the increase in population, growing urbanization, and higher demands for processed and unprocessed foods, resources related to food production have become scarce. Water and land can be considered as the primary resources to determine the crop production potential of a country. Ideally, countries that lack water and land resources can import these in virtual form. Sri Lanka is a country rich in water resources that faced bankruptcy recently. This study analyzes and explores the potential for use of land–water resources in Sri Lanka. A comprehensive framework is generated to identify the virtual land–water trade by considering ten major imports and nine major export crops in Sri Lanka. Consequently, the top ten imports/exports and top ten import/export trade partners are identified. The analysis reveals that Sri Lanka is a heavily import-dominant country, having seven times higher imports compared to exports. The country imports wheat, which is 82% of its import crops, and the same crop is the largest export (85% of crop export). Compared to its trade partners, Sri Lanka has sufficient water resources, but availability of arable land is limited. Banana is the largest export of the country, which involves higher embedded water and less land, matching the resource availability to Sri Lanka, whereas the trade partners are expected to continue importing the crop due to their water and land stress conditions. Finalization of the long-awaited agriculture policy of the country is strongly recommended.

In Latin America and the Caribbean, the interrelationships among water, energy, and food are complex, partly due to their development models, which are intensive in their use of these resources. This research aims to recognize and quantify the use of water and energy in food in Ecuador by identifying the main interrelationships, together with their causes and current impacts. Regarding methodology, this research uses sectoral data available at the national level and international databases to obtain cross indexes. The following indicators were sought: percentage of energy demanded by food in different stages, extraction of water for agricultural use, food energy productivity, virtual water, and embodied energy. As a result, it was estimated that food consumes 50% of imported energy and cocoa stands out with 7.6 km3 of water footprint; the products with the highest energy consumption are shrimp with 2090 KBOE and fish with 1459 KBOE. Fishing and aquaculture products present with a significantly high consumption level. Nearly all the virtual water and embodied energy are exported in banana, cocoa, and shrimp. Exporting groups make extensive use of the country’s water and energy resources.

Taking the Tarim River basin as the research object, the water footprint was calculated based on the water footprint theory based on the relevant data from 2008 to 2019, and the water resource evaluation system was constructed to analyze the water footprint and water resource utilization of the Tarim River basin from three levels of structure, benefit, and ecology. Based on the water footprint theory, the annual water footprint and GDP of Tarim River basin were used to construct the Tapio decoupling model, and the decoupling type between water resources utilization and economic growth was obtained. The relationship between water resource utilization and economic growth in Tarim River was analyzed by combining the decoupling type evaluation and water footprint evaluation. The internal benefit is poor, and the external benefit is good; The degree of water resource shortage is on the rise, and the self-sufficiency rate of water resources is large. On the whole, the decoupling strength increases gradually. Decoupling strength has obvious industrial influence characteristics. Based on the above research conclusions, the sustainable economic and ecological development of the Tarim River basin can be realized from two aspects: reducing water footprint and strengthening decoupling intensity.

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.

In this study, China’s virtual water trade was measured on the basis of multi-region input/output tables, and its influencing factors of change were decomposed. The results revealed that virtual water export and import increased from 161.5 billion tons and 114.07 billion tons in 2007 to 193.31 billion tons and 157.1 billion tons in 2014, respectively. Eight economies accounted for more than 50% of China’s total virtual water export and import, whereby the total of the United States, Japan, and Europe reached 44% (export) and 31.3% (import). The export scale, export of intermediate products, export industry structure, domestic water consumption coefficient, and domestic intermediate input structure were the main factors of the change in virtual water export. The growth of export scale was the primary reason for the growth of virtual water export. A decline in the domestic water consumption coefficient was the primary reason for the restrained growth of virtual water export. The import scale, import of intermediate products, import industry structure, water consumption coefficient of foreign countries, and the correlation among domestic industries were the main factors affecting the change in virtual water import. The growth of import scale was the primary reason for the growth of virtual water import in most sectors. A decline in the water consumption coefficient abroad was the primary reason for the restrained growth of virtual water import.

Cities are complex and evolving systems with various factors playing key roles, e.g., population increase, the migration of population, the availability of resources, and the flexibility of policies. Consumers’ socioeconomic status is also an important aspect that needs to be studied in the context of a self-reliant urban city in its resource consumption. In this regard, the association between water–food and socio-economic attributes was analyzed based on the consumer-centric approach for the Hyderabad Metro Development Authority (HMDA) region, India. In this study, the embedded water content in food consumption was estimated and analyzed for nine food groups and twelve economic classes of the HMDA region. The middle economic classes were found to correspond to ~80% of embedded water content in the HMDA region, followed by the upper and lower economic classes. Except for cereals, per capita, the water consumption of all food groups increased with the spending power of the economic class. The green, blue, and grey consumption water footprints (WFs) suggested that much of the water that is being consumed in the HMDA region is precipitation-driven, followed by surface and groundwater resources. Limited water resources, water resource variability, climate change consequences including future climate projections, uncertainty in data, WF estimates, and region’s future growth imply a detailed study in drafting policies to become a self-reliant region.

Virtual water and water footprint have received increasing attention. However, no published research has conducted a quantitative and objective review of this field from the perspective of bibliometrics. Therefore, based on the Web of Science Core Collection, this study employs CiteSpace to quantitatively analyze and visualize information about countries, institutions, and authors that have conducted virtual water and water footprint research over the past two decades. As of July 2020, there were 1592 publications on virtual water and water footprint, showing an increasing trend overall. The annual average number of publications was only 7.4 in 1998–2008, while it was 126.5 in 2009–2019. Among them, up to 618 publications in the field of environmental science, accounting for 46%. China was the most productive country with a total of 344 articles, but the Netherlands had the strongest influence with a betweenness centrality of 0.33, indicating its leading position. It is essential to strengthen cooperation between developed (water-rich) and developing (water-poor) countries and to incorporate virtual water into social water cycle research. This study is expected to provide a new perspective for investigating the research frontiers and hot spots of virtual water and water footprint research.

This paper commemorates the influence of Arjen Y. Hoekstra on water footprint research of the United States. It is part of the Special Issue “In Memory of Prof. Arjen Y. Hoekstra”. Arjen Y. Hoekstra both inspired and enabled a community of scholars to work on understanding the water footprint of the United States. He did this by comprehensively establishing the terminology and methodology that serves as the foundation for water footprint research. His work on the water footprint of humanity at the global scale highlighted the key role of a few nations in the global water footprint of production, consumption, and virtual water trade. This research inspired water scholars to focus on the United States by highlighting its key role amongst world nations. Importantly, he enabled the research of many others by making water footprint estimates freely available. We review the state of the literature on water footprints of the United States, including its water footprint of production, consumption, and virtual water flows. Additionally, we highlight metrics that have been developed to assess the vulnerability, resiliency, sustainability, and equity of sub-national water footprints and domestic virtual water flows. We highlight opportunities for future research.

Water use within power supply chains has been frequently investigated. A unified framework to quantify the water use of power supply chains deserves more development. This article provides an overview of the water footprint and virtual water incorporated into power supply chains. A water-use mapping model of the power supply chain is proposed in order to map the analysed research works according to the considered aspects. The distribution of water footprint per power generation technology per region is illustrated, in which Asia is characterised by the largest variation of the water footprint in hydro-, solar, and wind power. A broader consensus on the system boundary for the water footprint evaluation is needed. The review also concludes that the water footprint of power estimated by a top-down approach is usually higher and more accurate. A consistent virtual water accounting framework for power supply chains is still lacking. Water scarcity risks could increase through domestic and global power trade. This review provides policymakers with insights on integrating water and energy resources in order to achieve sustainable development for power supply chains. For future work, it is essential to identify the responsibilities of both the supply and demand sides to alleviate the water stress.

The agricultural community has a challenge of increasing food production by more than 70% to meet demand from the global population increase by the mid-21st century. Sustainable food production involves the sustained availability of resources, such as water and energy, to agriculture. The key challenges to sustainable food production are population increase, increasing demands for food, climate change, and climate variability, decreasing per capita land and water resources. To discuss more details on (a) the challenges for sustainable food production and (b) mitigation options available, a special issue on “Water Management for Sustainable Food Production” was assembled. The special issue focused on issues such as irrigation using brackish water, virtual water trade, allocation of water resources, consequences of excess precipitation on crop yields, strategies to increase water productivity, rainwater harvesting, irrigation water management, deficit irrigation, and fertilization, environmental and socio-economic impacts, and irrigation water quality. Articles covered several water-related issues across the U.S., Asia, Middle-East, Africa, and Pakistan for sustainable food production. The articles in the special issue highlight the substantial impacts on agricultural production, water availability, and water quality in the face of increasing demands for food and energy.

Studying the influencing factors of the drag effect of water resources and its temporal−spatial variation can help governments to solve the problem of water resource constraints on the economic growth of different regions. Based on Romer’s hypothesis, this paper uses panel data to empirically analyze the drag effect of water resources in China’s 31 provinces from 1987 to 2017. The research shows that: (1) Water resources have certain constraints on the economic growth of each region. Regional economic growth has declined by 0.23% (eastern), 0.07% (western), 0.43% (central) and 0.09% (northeastern) annually. (2) In provinces with rapid labor growth, water resources have a greater impact on economic growth. In provinces with low labor growth rates, the drag effect of water resources on economic growth is affected by the capital stock of the region. (3) Through the analysis of the water drag effect in different time periods, this paper finds that in some periods, the government’s mobilization of water resources for the economic growth in some regions will not only promote the transfer of labor between regions, but also cause changes in the regional water resources. According to the results of this paper, the following conclusions can be drawn: (1) It is necessary to vigorously develop water-saving agriculture, improve technical efficiency, and reduce the strong dependence of economic growth on water resources in the provinces which has a strong water drag effect on economic growth; (2) Provinces with moderate water resource constraints should take the lead in deploying strategic emerging industries, and accelerate the development of the tertiary industry; (3) Provinces with weakly water resource restrictions can promote the development of capital-based industries. Not only can the development of the economy be rational, but it can also reduce the economy’s dependence on resources, thereby achieving the sustainable use of water resources and sustainable economic growth.

This paper examines the transboundary water resources conflict resolution mechanisms. Various academic fields have provided conflict resolution mechanisms that could be used to analyse transboundary water conflicts. These mechanisms include social planner, water market, game theory, static and dynamic systems engineering models, and negotiation analyses. These mechanisms share some common characteristic features. This similarity has led to a general belief that these mechanisms are competitive substitutes. However, closer examination by this research reveals that these mechanisms have more complementarity than similarity. This complementarity permits researchers and practitioners to combine any two or more of them to develop more comprehensive mechanisms with stronger analytical capacity to analyse the different elements of the process of transboundary water conflict resolution.

In this commentary, we set out the rationale for bringing together two research fields: Water Footprint Assessment and environmental (economic) valuation, which have evolved separately. This has the potential to inform the efficient allocation of virtual water flows at a global scale. It would also address some of the aims and objectives in the Water Footprint Assessment Manual regarding the assessment of environmental impacts and their sustainability, which thus far have not been covered in the literature. We also indicate how established practice in the environmental valuation community would need to develop to facilitate productive exchange between the two fields. Finally, we outline the key developments in the non-peer reviewed grey literature that signal the merit of such an exchange.

Water footprint (WF) is a measure of the actual appropriation of water resources. WF accounting can provide a scientific basis for the managements of water resources. In this study, a multi-regional input-output model is employed to measure the quantity of blue WF (WF) and inter-provincial virtual water (VW) flows in China for the years of 2007 and 2010. The results show that: (1) China’s total WF increased from 205.42 billion m3 in 2007 to 229.34 billion m3 in 2010. Approximately 42% of the WF was attributed to VW embodied in inter-provincial trade. Xinjiang is the largest province of VW export, whereas Shanghai had the largest net VW inflows. (2) From 2007 to 2010, the share of the agricultural sector in the entire VW trade declined, but was still as high as 82.78%, followed by the industrial sector. (3) The north-to-south and south-to-south patterns were witnessed in the domestic VW flows. The provincial WF variations are found to be affected by the per capital GDP, total water resources, per capita water resources, and urban population. (4) By linking VW with an integrated WAVE+ (water accounting and vulnerability evaluation) factor, it was found that virtual scarce water (VSW) was mainly exported by the provinces in northern China. At the national level, the amounts of VSW inflows were consistently greater than those of VSW outflows for both years, 2007 and 2010, implying an increased pressure on the provinces with water deprivation issues. Overall, these results can provide a basis for refining the spatiotemporal allocation of water resources and mitigating the conflict between water supply and demand in China.

This paper presents the basic principles for the integration of the water and carbon footprints cost into the resource and environmental costs respectively, taking the suggestions set by the Water Framework Directive (WFD) 2000/60/EC one step forward. WFD states that full water cost recovery (FWCR) should be based on the estimation of the three sub-costs related: direct; environmental; and resource cost. It also strongly suggests the EU Member States develop and apply effective water pricing policies to achieve FWCR. These policies must be socially just to avoid any social injustice phenomena. This is a very delicate task to handle, especially within the fragile economic conditions that the EU is facing today. Water losses play a crucial role for the FWC estimation. Water losses should not be neglected since they are one of the major “water uses” in any water supply network. A methodology is suggested to reduce water losses and the related Non Revenue Water (NRW) index. An Expert Decision Support System is proposed to assess the FWC incorporating the Water and Carbon Footprint costs.

The Water Footprint, as an indicator of water consumption has become increasingly popular for analyzing environmental issues associated with the use of water resources in the global supply chain of consumer goods. This is particularly relevant for countries like the UK, which increasingly rely on products produced elsewhere in the world and thus impose pressures on foreign water resources. Existing studies calculating water footprints are mostly based on process analysis, and results are mainly available at the national level. The current paper assesses the domestic and foreign water requirements for UK final consumption by applying an environmentally extended multi-regional input-output model in combination with geo-demographic consumer segmentation data. This approach allows us to calculate water footprints (both direct and indirect) for different products as well as different geographies within the UK. We distinguished between production and consumption footprints where the former is the total water consumed from the UK domestic water resources by the production activities in the UK and the latter is the total water consumed from both domestic and global water resources to satisfy the UK domestic final consumption. The results show that the production water footprint is 439 m3/cap/year, 85% of which is for the final consumption in the UK itself. The average consumption water footprint of the UK is more than three times bigger than the UK production water footprint in 2006. About half of the UK consumption water footprints were associated with imports from Non-OECD countries (many of which are water-scarce), while around 19% were from EU-OECD countries, and only 3% from Non-EU-OECD countries. We find that the water footprint differs considerably across sub-national geographies in the UK, and the differences are as big as 273 m3/cap/year for the internal water footprint and 802 m3/cap/year for the external water footprint. Our results suggest that this is mainly explained by differences in the average income level across the UK. We argue that the information provided by our model at different spatial scales can be very useful for informing integrated water supply and demand side management.

In the globalized world, water utilization and carbon emissions are two important indicators for water and energy resources evaluation. This paper investigates the inter-sectoral linkage and external trade of virtual water (water embodied in products) and embodied carbon emissions in China based on input⁻output tables during 1997⁻2015. Results indicate that: inside China, agriculture, the electric and water industry are major virtual water suppliers, while heavy industrial sectors including the metal products industry, the petrochemical industry, other nonmetallic mineral products industry, and the mining industry are major embodied carbon emissions suppliers. China is the net exporter of virtual water (137.15 × 109 m3) and embodied carbon emissions (16.05 × 108 t). From the perspective of industrial chain, about 81% of virtual water export come from agriculture, the electric and water industry ultimately, and about 85% of embodied carbon emissions export come from the mining industry, the petrochemical industry, other nonmetallic mineral products industry, the metal products industry, and the electric and water industry ultimately.

Global freshwater demand will likely continue its expansion under current expectations of economic and population growth. Withdrawals in regions which are already water-scarce will impose further pressure on the renewable water resource base threatening the long-term availability of freshwater across the many economic activities dependent on this resource for various functions. This paper assesses the economy-wide implications of demand-driven water scarcity under a ‘middle-of-the-road’ socio-economic development pathway by considering the trade-offs between the macroeconomic and food security impacts. The study employs a global CGE model comprising an advanced level of detail regarding water uses across economic activities and which allows for a sector-specific endogenous adaptation to water scarcity. A sustainable withdrawal threshold is imposed in regions with extended river-basin overexploitation (India, South Asia, the Middle East, and Northern Africa) whilst different water management options are considered through four alternative allocation methods across users. The scale of macroeconomic effects is dependent on the relative size of sectors with low-water productivity, the amount of water uses in these sectors, and the flexibility of important water users to substitute away from water inputs in conditions of scarcity. The largest negative GDP deviations are obtained in scenarios with limited mobility to re-allocate water across users. A significant alleviation is obtained when demand patterns are shifted based on differences in water productivity, however, with a significant imposition on food security prospects.

An analysis of virtual crop water export through international trade is conducted for Greece, downscaled to the River Basin District (RBD) level, in order to identify critical “hotspots” of localized water shortage in the country. A computable general equilibrium model (MAGNET) was used to obtain the export shares of crops and associated irrigation water was calculated for all major crops in Greece. A distinction between virtual crop water locally consumed and traded internationally was made for all Greek RBDs. Cotton was identified as a large water consumer and virtual water exporter, while GR08 and GR10 were identified as the RBDs mostly impacted. The value of virtual water exported was calculated for all crop types and fruits and vegetables were identified as the crop most beneficial, since they consume the least water for the obtained value.

Water footprint has become a common method to study the water resources utilization in recent years. By using input–output analysis and dilution theory, the internal water footprint, blue water footprint and grey water footprint of China from 2002 to 2012 were estimated, and the consumption structure of water footprint and virtual water trade were analyzed. The results show: (1) From 2002 to 2012, the average annual internal water footprint was 3.83 trillion m3 in China, of which the blue water footprint was 0.25 trillion m3, and the grey water footprint was 3.58 trillion m3 (with Grade III water standard accounting); both the internal water footprint and grey water footprint experienced decreasing trends from 2002 to 2012, except for a dramatic increase in 2010; (2) Average annual virtual blue water footprint was the greatest in agriculture (39.2%), while tertiary industry (27.5%) and food and tobacco processing (23.7%) were the top two highest for average annual virtual grey water footprint; (3) Virtual blue water footprint in most sectors showed increasing trends due to the increase of final demand, while virtual grey water footprint in most sectors showed decreasing trends due to the decreases of total return water coefficients and conversion coefficients of virtual grey water footprint; (4) For water resources, China was self-reliant: the water used for producing the products and services to meet domestic consumption was taken domestically; meanwhile, China exported virtual water to other countries, which aggravated the water stress in China.

This paper presents an exhaustive review of global croplands and their water use, for the end of last millennium, mapped using remote sensing and non-remote sensing approaches by world’s leading researchers on the subject. A comparison at country scale of global cropland area estimated by these studies had a high R2-value of 0.89–0.94. The global cropland area estimates amongst different studies are quite close and range between 1.47–1.53 billion hectares. However, significant uncertainties exist in determining irrigated areas which, globally, consume nearly 80% of all human water use. The estimates show that the total water use by global croplands varies between 6,685 to 7,500 km3 yr−1 and of this around 4,586 km3 yr−1 is by rainfed croplands (green water use) and the rest by irrigated croplands (blue water use). Irrigated areas use about 2,099 km3 yr−1 (1,180 km3 yr−1 of blue water and the rest from rain that falls over irrigated croplands). However, 1.6 to 2.5 times the blue water required by irrigated croplands is actually withdrawn from reservoirs or pumping of ground water, suggesting an irrigation efficiency of only between 40–62 percent. The weaknesses, trends, and future directions to precisely estimate the global croplands are examined. Finally, the paper links global croplands and their water use to a paradigm for ensuring future food security.

Water scarcity in arid regions can be addressed by using the virtual water concept in water resources management. This research used a compiled county-level input–output table to analyze virtual water flows for the Heihe River Basin in 2012 by applying a multi-regional input–output (MRIO) model. The results showed that the Heihe River Basin is a net virtual water exporter at a scale of 1.05 billion m3, which accounts for one third of the total amount of the basin’s water resources. The midstream area of the basin imports 96.31% of virtual water (2.04 billion m3) and exports 88.84% of virtual water (0.94 billion m3). In contrast, the upstream and downstream parts have limited virtual water flows. The agricultural sector largely consumes water in each county; maize or wheat production accounts for approximately 50% of the total water consumption. For most sectors, the virtual water content from surface water is greater than that from groundwater. The ratio of virtual surface water to virtual groundwater ranges from 1.20 to 2.91. The results for the water stress index indicated that most counties experienced water stress due to maize production. Greater attention needs to be paid to the adaptation and assessment of virtual water strategies in arid regions.