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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) .

The inefficient application of water resources has become an urgent problem restricting the world’s sustainable development. Virtual Water Trade opens a new perspective on improving water resource utilization efficiency. Based on a multi-regional input–output model and the logarithmic mean Divisia index, the virtual water flows between 2000–2014 in 43 countries and regions have been evaluated, and the driving forces of changes in virtual water flows for the European Union were revealed. During the study period, the total amount of virtual water flow continued to increase. The United Kingdom is a net virtual water importer that depends on the European Union significantly. There was a large amount of virtual water flow from the European Union to the United States during 2000–2012. However, China gradually seized the share of virtual water from European Union exports after 2012. Economic effects and virtual water intensity effects are the most significant drivers of virtual water flows. The difference is that the economic effect positively drives virtual water flows, while the virtual water intensity effect negatively influences. The results reveal the nature of the United Kingdom in the virtual water trade and can provide post-Brexit recommendations.

The growth of Iran&rsquo, s agricultural sector in the past few decades has exerted enormous pressure on its aquifers. There is a strong disparity between economic development and natural resource endowments, which threatens water and food security. In this paper, we used a multiregional input&ndash, output (MRIO) framework to assess the virtual water flows in Iran. We also estimate the internal and external water footprint of regions compared to their water availability. The results show that the northern part of the country, with no water scarcity, imported virtual water through the trade of goods and services, while severely water-scarce regions were net virtual water exporters. Iran had a net export of 1811 Mm3 per annum. While blue water resources (surface and groundwater) accounted for 92.2% of the national water footprint, 89.1% of total exports were related to the agriculture sector, contributing to only 10.5% of the national income. The results suggest that policy-makers should reconsider the current trade policy regarding food production liberalization in order to make Iran&rsquo, s limited water resources available for producing industrial goods, which can contribute more to the economy.

&nbsp, The concept of virtual water, as a new approach for addressing water shortage and safety issues, can be applied to support sustainable development in water-scarce regions. Using the input-output method, the direct and the complete water use coefficients of industries categorized as primary, secondary, or tertiary, and the spatial flow patterns of the inter-provincial trade in the Gansu province region of China, were explored. The results show that in 2007, 2010, and 2012 the direct and complete water use coefficients of the primary industries were the greatest among the three industry categories, with direct water use coefficients of 1545.58, 882.28, and 762.16, respectively, and complete water use coefficients of 1692.22, 1005.38, and 873.44, respectively, whereas, the direct and complete water use coefficient values of the tertiary industry category were the lowest, with direct water use coefficients of 16.65, 7.74, and 66.89 for 2007, 2010, and 2012, respectively, and complete water use coefficients of 65.46, 66.89, and 72.81 for 2007, 2010, and 2012, respectively. In addition, study results suggest that the volume of virtual water supplied to Gasnu province&rsquo, s local industries has decreased annually, while virtual water exports from the province have increased annually, with the primary industry accounting for 95% of virtual water output. Overall, the virtual water of Gansu province in 2010 showed a net output trend, with a total output of 0.506 billion m3, while in 2007 and 2012 it showed a net input trend with a total input of 0.104 and 1.235 billion m3, respectively. Beijing, Shanghai, Guangdong, Ningxia and other water-scarce areas were the main input, or import source for Gansu&rsquo, s virtual water, during the years studied, these provinces imported more than 50 million m3 individually. Based on these results, it is clear that under the current structure, virtual water is mainly exported to the well-developed coastal areas and their adjacent provinces or other water-abundant regions. Therefore, Gansu province should (1) adjust the industrial structure and develop water-saving and high-tech industries, (2) adjust the current trade pattern to reduce virtual water output while increasing its input to achieve balanced economic development and water resource security. &nbsp

This paper introduces a modeling framework for the analysis of real and virtual water flows at national scale. The framework has two components: (1) a national water model that simulates agricultural, industrial and municipal water uses, and available water and land resources; and (2) an international virtual water trade model that captures national virtual water exports and imports related to trade in crops and animal products. This National Water, Food & Trade (NWFT) modeling framework is applied to Egypt, a water-poor country and the world's largest importer of wheat. Egypt's food and water gaps and the country's food (virtual water) imports are estimated over a baseline period (1986–2013) and projected up to 2050 based on four scenarios. Egypt's food and water gaps are growing rapidly as a result of steep population growth and limited water resources. The NWFT modeling framework shows the nexus of the population dynamics, water uses for different sectors, and their compounding effects on Egypt's food gap and water self-sufficiency. The sensitivity analysis reveals that for solving Egypt's water and food problem non-water-based solutions like educational, health, and awareness programs aimed at lowering population growth will be an essential addition to the traditional water resources development solution. Both the national and the global models project similar trends of Egypt's food gap. The NWFT modeling framework can be easily adapted to other nations and regions., Graphical abstract Unlabelled Image, Highlights • Virtual water trade should be considered when managing national water resources. • Non-water based solutions can remediate water problems in water-scarce countries. • Egypt's water and food gaps are projected to aggressively widen in the future. • Both the global and national models projected similar patterns of Egypt's imports. • NWFT modeling framework can be easily applied to any country in the world.

Study region The Yellow River Basin (a water-deficient region) in China. Study focus To establish whether the virtual water trade (VWT) is beneficial for water-deficient regions we conducted an integrated assessment of the local and distant VWT of the Yellow River Basin (YRB). We adopted a modified input–output analysis model and applied multiregional input–output tables of 31 provinces in China (2017) to estimate the dependence of the YRB on water from other regions and to determine the VWT status. We calculated the total water consumption coefficient of 29 sectors in the YRB, investigated the water-use intensity of various sectors, and analyzed the water footprint and per capita usage of each province. Furthermore, we revealed the VWT among downstream, midstream, and upstream regions of the YRB. New hydrological insights for the region This study revealed that virtual water flow is unidirectional from downstream and midstream regions to upstream regions, and that the trade structures among these three regions of the YRB differ notably, which has rarely been addressed in previous literature. Furthermore, the VWT exacerbates water resource shortages in the YRB. The irrational industrial structure is the main reason for the need for transfer of water resources. This information could inform the development of effective policies both for alleviating regional water shortages and for developing a viable virtual water strategy for the YRB.

International agricultural trade triggers inter-dependency among distant countries, not only in economic terms but also under an environmental perspective. Agricultural trade has been shown to drive environmental threats pertaining to biodiversity loss and depletion and pollution of freshwater resources. Meanwhile, trade can also encourage production where it is most efficient, hence minimizing the use of natural resources required by agriculture. In this study, we provide a country-level assessment of the future international trade for 6 primary crops and 3 animal products composing 70% of the human diet caloric content. We set up four variegate socio-economic scenarios with different level of economic developments, diets habits, population growth dynamics, and levels of market liberalization. Results show that the demand of agricultural goods and the correspondent trade flow will increase with respect to current levels by 10–50% and 74–178% by 2050, respectively. The largest increase in the amount of traded goods is expected under the Economic Optimism scenario that will see an average trade flow of 2830 kcal/cap/day (i.e., nearly doubling the current per-capita flow). Most of the increase will be driven by the trade of crops for animal feeding, particularly maize will be the most traded crop. The trade networks architecture in 2050 and 2080 will be very different from the one we actually know, with a clear shift of the trade pole from the Western toward the Eastern economies. The dramatic changes of global food-sources and trade patterns will jeopardize the water resources of new regions while exacerbating the pressure in those areas that will continue serving food also in the future. In spite of this, trade may annually save around 40–60 m3 of water per person, compared to a situation where countries are self-sufficient.

Sustainable use of resources is critical, not only for people but for the whole planet. This is especially so for freshwater, which in many ways determines the food security and long-term development of nations. Here, we use virtual water trade to analyze the sustainability of water used by Pakistan in the international trade of 15 major agricultural commodities between 1990 and 2016 and in 2030. Most of the existing country-level studies on virtual water trade focused on net virtual water importers, which are usually water-scarce countries as well. This is the first study to concentrate on a water-stressed net virtual water-exporting country. Our results show that Pakistan has been trading large and ever-increasing volumes of virtual water through agricultural commodities. Despite the overall small net export of total virtual water per year, Pakistan has been a net-exporter of large quantities of blue (fresh) virtual water through its trade, even by fetching a lower value for each unit of blue water exported. Given Pakistan&rsquo, s looming water scarcity, exporting large volumes of blue virtual water may constrain the country&rsquo, s food security and long-term economic development. Improving water use efficiency for the current export commodities, for example, rice and exploring less water-intensive commodities, for example, fruits and vegetables, for export purposes can help Pakistan achieve sustainable water use in the future.

Climate change is leading to increased water scarcity and drought in many parts of the world. This has implications for the European Union (EU) because a lot of the water intensive goods consumed or used there are produced abroad. This makes the EU&rsquo, s economy dependent on water resources well beyond its borders since when a country imports water intensive goods, indirectly it also imports virtual water (water needed to produce the imported goods). This study maps the EU&rsquo, s global dependency on water resources outside its borders in terms of virtual water imports and assesses how water scarcity and drought may disrupt supplies of key food crops that it imports. The EU uses approximately 668 km3 of water for all of the goods it produces, consumes and exports, annually. Around 38% of that water comes from outside its borders, which means that the EU&rsquo, s economy is highly dependent on the availability of water in other parts of the world. In the near future, supplies of certain crops to the EU could be disrupted due to water scarcity in other parts of the world, a large portion of the water used in producing soybeans, rice, sugarcane, cotton, almonds, pistachios and grapes for import to the EU comes from areas with significant or severe levels of water scarcity. Although the immediate risks to the EU&rsquo, s economy are due to current water scarcity levels, any disruption to rainfall patterns that occur in the future, due to the effects of climate change in the countries of origin of key crops, could have a far greater impact. This is because as much as 92% of the EU&rsquo, s total external water demand from agriculture is attributed to green water use, availability of which has relatively higher vulnerability to drought.

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

Climate change, water shortages and desertification threaten the economic and environmental sustainability in the Mediterranean. Limited rainfall and higher temperatures put agricultural production, which relies on water availability, in jeopardy. Thereupon, Mediterranean countries pursue agri-food resilience and water preservation through efficient water policies. Hence, water-deprived areas ought to import rather than produce water-intensive products to maintain water inventories and sustainability consequently. As this study examines the water sustainability for a Mediterranean water-scarce region with a particular focus on agriculture, the virtual water trade balance explores this hypothesis. A regional input–output model is constructed, and then total water consumption and the virtual water flows for each economic sector are estimated to determine the virtual water trade balance of the economy. Results indicate that the study area has a trade deficit and struggles economically but is a net importer of virtual water and secures water sustainability. As this virtual water deficit relies heavily on agriculture and originates in vast total water consumption rather than a large trade deficit, a paradox occurs, water-intensive cultivations and animals that consume 91.75% of water resources end up appearing to be water-saving. Further research is needed to strike a balance between economic growth and environmental protection.

Sustainable agriculture in China is threatened by rapid socioeconomic development, urbanization, and climate change. In addition, the distribution of freshwater resources between regions is highly unequal, and water shortages are common in arid regions. The virtual water trade can help to ease water shortages in arid areas by utilizing the comparative advantage of water resources in other areas. However, sometimes the patterns of the virtual water trade do not fit the distribution of water resources and, in these instances, inter-regional coordination would help to improve the level of equality in the virtual water trade. We combined the concept of the Gini coefficient with a multi-objective optimization model to investigate the inter-regional coordination of the virtual water trade in an arid region of China. Agricultural data from different regions of Gansu Province in 2014 were used to explore methods of improving the equality of virtual water flow patterns in the agricultural sector. Three constraints (a crop supply constraint, an irrigation water constraint, and an economic benefit constraint) were set up to investigate the relationship between different challenges and the effects of inter-regional coordination. Our results validated the use of the proposed method in Gansu Province and indicated that it could be applied to other arid regions. Variations in crop supply, irrigation water, and economic benefits were found among the different constraint scenarios, illustrating the trade-offs between water-saving and agricultural objectives. Our results also showed the balance between various factors, including the equality of the virtual water patterns, water-saving measures, and economic benefits. These results support the effectiveness of inter-regional coordination and indicate that the improvement in equality and the adjustment cost should be balanced. Our findings will help to guide the planning of local crop acreages to achieve the best virtual water balance model between regions.

Freshwater stems from precipitation over land, which differentiates into a blue water flow (groundwater and surface water) and a green water flow (evaporation). Both flows are partially allocated to serve the economy, resulting in blue and green water footprints (WF). There are maximum sustainable levels to the blue and green WF, since rainfall is limited and part of the flows need to be reserved for aquatic and terrestrial biodiversity. Water scarcity, the degree to which the actual approaches the maximum sustainable WF, is becoming increasingly important due to increasing water consumption but limited water availability. The goal of this research is to broaden the discourse on freshwater scarcity in two respects. First, by assessing how Water Footprint Assessment (WFA) for a country can contribute to more sustainable and efficient allocation of blue water resources. Second, by assessing the allocation of the world’s green water resources with respect to maximum sustainable levels.

Limited water resources, an increase in water demand and a changing climate triggered the development of new concepts for assessment of water demand and water consumption locally and globally. The newest concepts that successfully tackle this issue are water footprint and virtual water trade. Aims of this study are: (1) to define specific water demand for the most important agricultural products in the international trade of the Republic of Serbia, (2) to assess possibilities of an increase in water productivity for those products, and (3) to assess sustainability of water resources in Serbia, based on the ratio of import/export during virtual water trade. Specific water demand for wheat, maize, sunflower, sugar beet and soya bean has been calculated and compared with specific water demand in other countries. Results prove that water productivity can be improved by, for example, using other varieties of crops or modifying cultivation technology. The ratio of imported/exported virtual water quantities for the periods 1995-1999 and 2010- 2013 in Serbia shows that more water was exported than imported. Sustainability of water resources in Serbia will not be endangered even if the export of agricultural products is increased. Ograničeni vodni resursi, rastući zahtevi za vodom i sve nepovoljniji klimatski uslovi doveli su do razvoja novih koncepata, sa ciljem procene potražnje i potrošnje vode na lokalnom i globalnom nivou. Koncepti koji se u novije vreme koriste pri rešavanju ovakvih problema su 'vodni otisak' i 'virtuelna trgovina vodom'. Ciljevi ovog rada su: (1) da se odrede specifični zahtevi za vodom najvažnijih poljoprivrednih proizvoda u procesu međunarodne trgovine Srbije, (2) da se oceni mogućnost povećanja produktivnosti vode pri proizvodnji tih proizvoda i (3) da se proceni održivost vodnih resursa Srbije, na osnovu odnosa vode koju Srbija uvozi/izvozi tokom 'virtuelne trgovine vodom'. Izračunavanjem specifične potrošnje vode za pšenicu, kukuruz, suncokret, šećernu repu i soju i poređenjem sa specifičnom potrošnjom vode ovih kultura u drugim zemljama, utvrđeno je da postoji prostor da se unapredi korišćenje vode, npr. podešavanjem sortimenta ili promenama u tehnologiji gajenja. Na osnovu odnosa izračunatih izvezenih i uvezenih virtuelnih količina vode za period 1995-1999. godine i 2010-2013. godine, može se zaključiti Srbija izvozi više vode nego što uvozi. Čak i sa dodatnim porastom izvoza poljoprivrednih proizvoda neće doći do narušavanja vodne održivosti Srbije.

International agri-food trade has expanded rapidly during the past decades and changed considerably in structure with important implications, especially for developing economies. One of the main environmental concerns regarding international trade is the exploitation and redistribution of water resources. In this paper, we use the virtual water approach for analyzing the relationship between global agri-food trade, its structure and virtual water flows in the period of 1986–2011. Specifically, for five regions and the world, we calculate growth rates of interregional trade values and virtual water volumes, the contribution of different product groups to trade and the economic water efficiency of imports and exports. Our findings show that, over time, trade values have generally increased more rapidly than virtual water volumes. In Africa and Southern America, virtual water outflows have roughly quadrupled since 1986. In all regions, staples and industrial products account for the largest share in virtual water trade. The recent shift towards high-value exports is beneficial for low-income countries from a regional economic water efficiency perspective due to high trade values and low associated virtual water volumes. Economic water efficiency of trade has increased in all regions since 2000 and the return to virtual water outflows is especially high in Europe. ispartof: Sustainability vol:7 issue:5 pages:5542-5563 status: published

In the international trade network, links express the (temporary) presence of a commercial exchange of goods between any two countries. Given the dynamical behaviour of the trade network, where links are created and dismissed every year, predicting the link activation/deactivation is an open research question. Through the international trade network of agricultural goods, water resources are ‘virtually’ transferred from the country of production to the country of consumption. We propose a novel methodology for link prediction applied to the network of virtual water trade. Starting from the assumption of having links between any two countries, we estimate the associated virtual water flows by means of a gravity-law model using country and link characteristics as drivers. We consider the links with estimated flows higher than 1000 m 3 /year as active links, while the others as non-active links. Flows traded along estimated active links are then re-estimated using a similar but differently-calibrated gravity-law model. We were able to correctly model 84% of the existing links and 93% of the non-existing links in year 2011. It is worth to note that the predicted active links carry 99% of the global virtual water flow; hence, missed links are mainly those where a minimum volume of virtual water is exchanged. Results indicate that, over the period from 1986 to 2011, population, geographical distances between countries, and agricultural efficiency (through fertilizers use) are the major factors driving the link activation and deactivation. As opposed to other (network-based) models for link prediction, the proposed method is able to reconstruct the network architecture without any prior knowledge of the network topology, using only the nodes and links attributes; it thus represents a general method that can be applied to other networks such as food or value trade networks.

Food security, and in particular food availability, depends on environmental resources, climatic conditions and agricultural practices, having water resources as a common denominator. There is major concern about food security in countries having limited water resources, due to the large volumes of water that are required to produce food commodities. Water-deficit countries tend to rely on international trade to close the gap between water (and thus food) demand and supply. Against this backdrop, the purpose of this study is twofold. First, to analyse water resources in the Middle East and North African region also considering the political economy trends and dynamics, which drive the region’s demand for water. Secondly, the study aims to increase understanding on the role that trade of agricultural commodities has played in meeting the requirements of the MENA populations, in terms of food and associated water ‘embedded’ as a factor of production. The study argues that virtual water trade, that is, the virtual transfer of the water used for agricultural production from producing to consuming countries, has provided the region’s economies with water and food security over the past 25 years. The study shows that virtual water imports have more than doubled and the increase has been more than proportional to population growth in the area. Food products account by far for the largest share of virtual water flows, while crops and high value foods are the main categories of agricultural products associated with virtual water imports. The largest share of the MENA imports originate from outside the region, thus determining a marked dependency on water resources available elsewhere, but not always from water-secure countries.

The increasing global demand for farmland products is placing unprecedented pressure on the global agricultural system and its water resources. Many regions of the world, that are affected by a chronic water scarcity relative to their population, strongly depend on the import of agricultural commodities and associated embodied (or virtual) water. The globalization of water through virtual water trade (VWT) is leading to a displacement of water use and a disconnection between human populations and the water resources they rely on. Despite the recognized importance of these phenomena in reshaping the patterns of water dependence through teleconnections between consumers and producers, their effect on global and regional water resources has just started to be quantified. This review investigates the global spatiotemporal dynamics, drivers, and impacts of VWT through an integrated analysis of surface water, groundwater, and root-zone soil moisture consumption for agricultural production; it evaluates how virtual water flows compare to the major ‘physical water fluxes’ in the Earth System; and provides a new reconceptualization of the hydrologic cycle to account also for the role of water redistribution by the hidden ‘virtual water cycle’.

Population growth, socio-economic development and climate changes are placing increasing pressure on water resources. Crop water footprint is a key indicator in the quantification of such pressure. It is determined by crop evapotranspiration and crop yield, which can be highly variable in space and time. While the spatial variability of crop water footprint has been the objective of several investigations, the temporal variability remains poorly studied. In particular, some studies approached this issue by associating the time variability of crop water footprint only to yield changes, while considering evapotranspiration patterns as marginal. Validation of this Fast Track approach has yet to be provided. In this Letter we demonstrate its feasibility through a comprehensive validation, an assessment of its uncertainty, and an example of application. Our results show that the water footprint changes are mainly driven by yield trends, while evapotranspiration plays a minor role. The error due to considering constant evapotranspiration is three times smaller than the uncertainty of the model used to compute the crop water footprint. These results confirm the suitability of the Fast Track approach and enable a simple, yet appropriate, evaluation of time-varying crop water footprint.

This study develops water footprint scenarios for Europe for 2050, at the country level, based on projections regarding population and economic growth, production and trade patterns, consumption patterns (diets and bioenergy use) and technological development. The objective is to estimate possible future changes in the green, blue and grey water footprint (WF) of production and consumption, to analyze the main drivers of projected changes and to assess Europe’s future dependence on water resources elsewhere in the world. We develop four scenarios, considering globalization versus regional self-sufficiency, and development driven by economic objectives versus development driven by social and environmental objectives. The study shows that the most critical driver of change affecting Europe’s future WF is the consumption pattern. The WFs of both production and consumption in Western Europe increase under scenarios with high meat consumption and decrease with low-meat scenarios. Besides, additional water demands from increasing biofuel needs will put further pressure on European water resources. The European countries with a large ratio of external to total WF of consumption in 2000 decrease their dependencies on foreign water resources in 2050.

We quantify the potential impacts of global food production on freshwater availability (water scarcity footprint; WSF) by applying the water unavailability factor (fwua) as a characterization factor and a global water resource model based on life cycle impact assessment (LCIA). Each water source, including rainfall, surface water, and groundwater, has a distinct fwua that is estimated based on the renewability rate of each geographical water cycle. The aggregated consumptive water use level for food production (water footprint inventory; WI) was found to be 4344 km3/year, and the calculated global total WSF was 18,031 km3 H2Oeq/year, when considering the difference in water sources. According to the fwua concept, which is based on the land area required to obtain a unit volume of water from each source, the calculated annual impact can also be represented as 98.5 × 106 km2. This value implies that current agricultural activities requires a land area that is over six times larger than global total cropland. We also present the net import of the WI and WSF, highlighting the importance of quantitative assessments for utilizing global water resources to achieve sustainable water use globally.

We quantify the impact of food consumption on local and foreign water resources through an indicator of the environmental value of the riverine water. This indicator takes into account both the local environmental relevance of the fluvial area where water is withdrawn (biodiversity richness, riparian vegetation, sediment transport, etc) and the downstream effects of water withdrawals. In the 1986–2013 period, food consumption has more than doubled its impact on foreign riverine environments, but still the international trade reduces the pressure of food consumption on global river system by 11%, as compared to an ideal situation where all food is produced locally. We also show the geography of country (or individual) responsibility on the environmental changes of world rivers. Hotspots of food-related river-environment degradation are found in Australia, Pakistan, South Africa, and Spain.

Water shortages pose significant threats to local water security and food production around the world. Water managers have resorted to various water resources planning measures to overcome these challenges. For the first time and for a case study in Iran, we provide a comparative analysis of two such measures: physical and virtual inter-basin water transfers (IBWT). We evaluate green and blue water footprints (WF) associated with the production of 39 crops grown in humid Mazandaran and arid Semnan provinces, under (i) current production patterns and current local water availability; (ii) current production patterns and a planned physical IBWT scheme between Mazandaran (donor) and (receiving) Semnan province to provide water to water-intensive crops in the latter; (iii) modified cropping patterns, such that surplus production of water-intensive crops in Mazandaran abates production in Semnan province, coupled with interprovincial trade (i.e., a virtual IBWT scheme). We find that crops currently produced in Mazandaran have considerably lower blue WFs per unit of production (m3 t−1) and a higher economic blue water productivity (EBWP, $ m−1) than in Semnan province. A physical IBWT would reduce blue water scarcity (BWS) in Semnan province by 34%, but at the cost of reduced EBWP by up to 46% of crops irrigated with the more costly transferred water. A virtual IBWT would reduce BWS in Semnan province to the same degree, while only modestly increasing BWS in Mazandaran province (from 0.15 to 0.21, indicating that Mazandaran water resources can sustainably support the proposed increase in production). Moreover, Mazandaran's provincial average EBWP is even raised (by 7%) in the virtual IBWT scenario.