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International trade of commodities causes an international water flow in virtual form. This study focuses on the virtual water flow related to international crop trade. We build complex networks of virtual water trade (Virtual Water Trade Networks, VWTNs hereafter) with annual data of trade and its virtual water content from 1986 to 2013 among all countries. By analyzing the temporal characteristics and spatial homogeneity of the VWTNs, we find that trade networks display a feature of scale-free. This suggests those core export and import countries play dominant roles in international virtual water flows. However, the structure of the VWTN becomes more heterogeneous with time, indicating that virtual water trade has been getting more globalized. By spatially recoding the trade volumes and using detrended fluctuation analysis, this study finds that geographical distance becomes less binding in international virtual water trades. Other important findings from our VWTNs analysis include that virtual water trade patterns remain relative stable within trading groups and that geopolitical, political, and economic environments can significantly influence world virtual water trade flows. This study provides an understanding of the international water trade and its relationship with the macro social and economical conditions at the global scale. Its method thus can be applied to analyze the temporal and spatial dynamics of other networks with directed trade flow.

The virtual water strategy (VWS) provides an alternative modelling method to transport virtual water (VW) from water-rich regions to areas with water-scarce resources. This strategy is designed to balance the differences of regional water supplies, improve water-use efficiency, and ensure the environmental sustainability of water resources. However, the practical implementation of VWS still faces resistance due to a poor understanding of VWS and minimal pressure to make hard decisions about sharing water resources. Therefore, it is important to study the decision-making mechanism and behavioral motivation in the implementation process of VWS. Game theory has been extensively applied in economics, political science and natural science to predict and understand decision outcomes. Cost-benefit analysis and behavior incentives using VWS can also be accessed using game theory with a symmetric take out modelling approach. In this approach, efficient and acceptable methods to construct a VWS-based framework of VW trading can implemented. This study builds a semi-quantitative game model to analyze acceptance paradigms for economic development and trade patterns in sharing water. The optional strategies and relevant payoffs are analyzed to explore factors affecting the implementation of VWS. The results show that an equilibrium in which all areas share VWS is the optimal result. However, egoistic motivations, political pressures and risk of loss hinders decision making. Thus, to achieve mutual benefits within an interregional VWS framework, some external interventions are required. Interventions can include: reasonable incentive mechanisms for rewards or punishments, improving technologies and efficiency related to VW production, and promoting long-term trade cooperation between the regions. The uneven distribution and availability of freshwater globally dictates that the sharing and availability of water into the future will require VWS modelling and the political willingness to share resources.

This paper quantifies water consumption of Vietnam in agricultural products on virtual water perspective. The calculation of water footprint and virtual water in four major agricultural crops is first implemented for seven regions of the country. The domestic and international trades of virtual water are subsequently investigated to demonstrate the commodity and virtual water flows among regions. The analysis reveals that Mekong River Delta is an important exporter of virtual water in rice product for both domestic and international trades while Central Highland is the main virtual exporter in coffee. The paper also proposes a new water stress index such that it considers both direct and indirect water use given transboundary water resources. The proposed water stress index indicates the actual water scarcity in Vietnam in which the water-rich regions i.e. Red River Delta and Mekong River Delta are in severe water stress.

This paper examines the determinants of virtual water trade – embodied in agricultural products – and tests the relationship between property rights and the export of water-intensive products. Using two different measures of property rights protection, I show that countries with weaker property rights have an apparent comparative advantage in the export of water-intensive products. After controlling for economic size, natural resource endowments and bilateral trade determinants, the trade flow of virtual water is negatively and significantly correlated with the property rights index of the exporting country. The results are robust across different estimation methods.

This paper includes country level virtual water data in an Environmental Kuznets Curve (EKC) for water pollution. Virtual water accounts for the total amount of water required to produce a good in all stages of production. This paper constructs a water independence index, defined as the water required in domestic production divided by the amount of water required for all imported goods. Results suggest an increase in trade openness and importing water intensive goods may lower water pollution levels.

A new approach is developed based on cooperative games and virtual water concept for quantity-quality assessment of water transfer projects. It is argued that a water transfer project can be executed to satisfy both economic and environmental objectives and needs. In fact, the proposed model evaluate economic, equity, and environment criteria in order to lead to sustainable development. First, an optimization model with economic objective is developed based on virtual water concept that maximizes the net benefit of the inter-basin water transfer. Then, to meet water quality requirements, the impact of decreasing the flow in a sending basin is estimated by using a virtual water quality concept and Nash Equilibrium. Finally, to achieve equity and to retrieve sufficient incentives for water users, cooperative game theory approaches are utilized for the reallocation of net benefits. Effectiveness of the proposed methodology has been examined by applying it to a large scale case study of an inter-basin water transfer in central part of Iran, from the Solakan to the Rafsanjan basins. The results reveal that the proposed methodology could be used as an effective tool for sustainable development in the inter-basin water allocation management with resolving confliction aim with the physical and environmental constraints by considering virtual water concept. In addition, by using cooperative game theory, the net benefit of the project has been realized to be twice the initial allocation.

Access to water and food security in arid and limited water resources regions requires optimal cropping pattern. In this research, virtual water (VW) trade was implemented to find the best cropping pattern in Sistan and Blouchestan province of Iran. Forty-four common cultivated productions in the province were classified in 6 classes including cereals, legumes, vegetables, oil crops, fruits, and potato. Required data were collected during 2000–2011. The improper distribution of crops in the current cropping pattern led to a high mean value of TVW both at the county (0.53–4.35 m3 kg−1) and province levels, where blue VW accounted for 91.3–98.5 % of TVW. By considering three indices including VW, unit blue water value, and the ratio of required blue water to the total water allocation for the agriculture, the optimal cropping pattern was proposed as potato followed by vegetables, legumes, fruits and cereals. Based on the results, production of vegetables and potato both at the county and province levels might be a target for improvements and might contribute significantly for reducing national water use for irrigation.

Using input–output table of China in 2007, this paper built an input–output model and tested the effect of variation of water-use efficiency on the structure of virtual water trade. As the final water consumption coefficient increases (i.e., water-use efficiency decreases) in some department, the proportion of this department’s virtual water outflow/inflow increases while those of all the other departments decrease. As the direct water consumption coefficient increases (i.e., water-use efficiency decreases), the proportion of this department's virtual water outflow/inflow increases while the sum but not each of the other departments’ proportions decreases. The final water consumption coefficient of any department is bigger than the direct one, implying indirect water consumption exists and final water consumption coefficient is a better indicator for water-use efficiency. The paper shows that China is a net exporter of virtual water, but the departments of agriculture, mining, petrochemical are the net importers of virtual water. According to the results, China should use the strategy of virtual water trade to alleviate water shortage. Also, China should adopt water-saving technology in production, and improve the level of self-sufficiency of products in order to reduce reliance on foreign trade correspondingly.

Various scientific and technological based solutions such as virtual water trading, desalination, groundwater extraction and wastewater reuse have been proposed and implemented in many parts of Asia and Africa to relieve water scarcity. This paper applies SWOT (strengths, weaknesses, opportunities and threats) analysis to examine the suitability of these alternative water solutions to alleviate water scarcity. SWOT analysis proves to be a useful decision making tool as it provides a qualitative approach to simplify multilayer and interdisciplinary problems. The main input for the SWOT analysis consists of knowledge gathered from seven experts in the field of water and environmental sciences. The results show that compared to other solutions, wastewater reuse offers the most desirable qualities as a viable water solution for sustainable water management in Asia and Africa.

Intended for comprehensive assessment of water usage in agricultural for food production and to address its future, it is essential to scrutinize the dynamic behavior of crop production and its water footprint and virtual water trade. Through the current research a System Dynamic model that can be applied to estimate crop production, water footprint, and virtual water nexus was developed. The system could be applied to explore how water footprint of crop production and consumption change under proposed planned scenarios which differ from each other in terms of main drivers of change. The drivers of change include population, per capita crop consumption, crop trade patterns, crop yield, and climate change impact. The system is developed to be applied at the country level. A case study from Egypt was analyzed applying the developed system. Where, water footprint of wheat production (green, blue, and grey water), consumption (internal, import and export), and its virtual water balance for years 2010 to 2050 were analyzed under proposed planned scenarios. These proposed planned scenarios were varying in wheat trade pattern strategies and impact of climate change on wheat water consumption and its yield.

Methods and datasets necessary for evaluating water footprints (WFs) have advanced in recent years, yet integration of WF information into policy has lagged. One reason for this, we propose, is that most studies have focused on national units of analysis, overlooking scales that may be more relevant to existing water management institutions. We illustrate this by building on a recent WF assessment of California, the third largest and most populous state in the United States. While California contains diverse hydrologic regions, it also has an overarching set of water institutions that address statewide water management, including ensuring sustainable supply and demand for the state’s population and economy. The WF sheds new light on sustainable use and, in California, is being considered with a suite of sustainability indicators for long-term state water planning. Key to this integration has been grounding the method in local data and highlighting the unique characteristics of California’s WF, presented here. Compared to the U.S., California’s WF was found to be roughly equivalent in per-capita volume (6 m3d−1) and constituent products, however two policy-relevant differences stand out: (1) California’s WF is far more externalized than the U.S.’s, and (2) California depends more on “blue water” (surface and groundwater) than on “green water” (rainwater and soil moisture). These aspects of California’s WF suggest a set of vulnerabilities and policy options that do not emerge in national-level assessments. Such findings demonstrate that WF assessments may find more policy relevance when scaled to analytical units where water-related decision making occurs.

Increasing freshwater demands have made allocation of water in water-scarce regions especially severe in arid areas. To assist in allocating water, a virtual water assessment methodology is described to assess strategies of saving water by identifying products which would be better as imports rather than producing them. Virtual water quantities, including green and blue water for five major crops, are analyzed, utilizing the methodology, for the three regions of East, Mid and West in Gansu Province, Northwest China, over a nine-year period from 2002 to 2010. Unit virtual water value as well as crop water use efficiencies are included, to determine if current cropping patterns are reasonable. Overall, the methodology encourages crops with lower water consumption, higher unit virtual water value, and crop water use efficiency. Estimates of potential virtual water flows reflect either the amount of virtual water which needs to be imported or the amount which can be exported. The results show that for different regions of Gansu, wheat and soy should be reduced in all three regions; cotton and corn can be increased in the West and Mid regions, respectively; potatoes can be a largely encouraged product throughout Gansu Province. Current cropping patterns in the three regions in the Province are therefore shown to be not optimal; changes in cropping patterns can be initiated, and water deficits can be balanced by virtual water transfers amongst the three regions as indicated by potential virtual water flows.

Without subdividing into blue and green virtual water, the virtual crop water is currently used in the allocation of water resources based on virtual water strategy. In order to improve agricultural water use efficiency and the proportion of green water utilization, a multi-objective optimal allocation model for agricultural water resources is developed in this study. The model is based on the subdivision of virtual water into blue and green virtual water, subject to three objectives of the maximum net benefit from agriculture, the minimum fairness difference in the utilization of water, and the maximum proportion of green water utilization. Taking Shiyang River basin as an example, agricultural water resources are optimized through regional virtual water trade in the basin. Results show that compared with the situation in the year 2007, the net benefit of agriculture, the fairness difference in the utilization of water, and the proportion of green water utilization are optimized. At the same time, the planting ratio of food crops, such as corn, reduces, while the planting ratio of cash crops, such as cotton, vegetables, and fruits, increases. Through regional virtual water strategy in the basin, with the crops of different districts having comparative advantages, the proportion of green water utilization and the blue water use efficiency are improved. The study provides a scientific basis to solve the water shortage problem in the basin.

Role of virtual water (VW) in optimizing water resources management in Jordan, a far water-short country, was explored by calculating VW content of imported commodities and their costs. Feasibility of farming and water required to produce all crops growing in Jordan were evaluated using net return per unit volume of water and VW embedded in unit mass of production. The results of these analyses showed that there were regional differences in crop profitability and thus net return from unit volume of irrigation water. This was attributed to variations in agro-climatic zones punctuated by production and irrigation technologies and access to water resources. In this regard, opportunity cost of water should be considered when allocating water to different consumption sectors. Agricultural systems generating net profits less than an arbitrary limit of $1.0 m−3 of irrigation water and producing yield at water use efficiency of 50–60 m3 ton−1 or more were viewed not feasible. The key challenge facing decision makers would be to ensure that the opportunity cost of water was incorporated into the analysis process when determining future cropping pattern. Such a cost of water should be combined with crop-embedded VW analysis and expected net return from unit volume of irrigation water. Therefore, water allocation mechanism (e.g. water market) need to be developed for more efficient water use than the commonly practiced farm quota. Optimization of the usage of the limited water resources can be envisaged by continuous imports of VW, especially that embedded in cereal, oil, meat, live animals and sugar. Appropriate amendment of water legislations and concerned institutions are encouraged to provide better guidelines to policy makers, water managers, extension and advisory services, water use associations and farmers. Optimization of water resources management could be based on contract farming to ensure that water allocation and cropping pattern respond to water scarcity. Furthermore, Jordan should concentrate on production and export of crops having low VW contents and high return per m3.

The term virtual water refers to the volume of water used in the production of a commodity or service. Accordingly, virtual water ‘trade’ is the amount of water ‘embedded’ in commodities being transferred from one place to another as a consequence of trade. This paper argues that the conventional methods so far adopted for the computation of virtual water ‘flows’ (based on Hoekstra and Hung 2002) have considered only direct water usage and not sufficiently distinguished between blue and green water resources. This has brought about flawed estimates of virtual water ‘flows’, thereby limiting the usefulness of the virtual water concept as a tool for informing water policy. A novel approach for computing virtual water ‘flows’ which applies the Input–output (IO) methodology to account for both direct and indirect water consumption, and simultaneously distinguishes between the different typologies of water, is presented. The study upholds that the integration of these two methods can not only provide a more robust framework for quantifying virtual water ‘flows’, but also enhance the relevance of the concept as a tool for water resource management policy. The implications of these alternative estimation methods are here illustrated using data referring to 11 Mediterranean economies and 7 internationally traded agricultural commodities.

China has been experiencing rapid urbanization since the reform and open policy launched in 1978, leading to the growth of urban water demands and aggravating water scarcity especially in the new millennium. Accordingly, water resources previously used for agriculture and environmental systems tend to be transferred to urban systems. Limited by the total quantity and frail environments, the patterns of water resources flows among different sectors and regions change obviously. Water related problems induced by rapid urbanization have become one of the key concerns for scientists and governments. The purpose of this paper is to analyze the new features of water resources flows related to urbanization in China, mainly with regard to bidirectional water resources flows between rural and urban areas, environmental and socio-economic systems, real and virtual water flows between the south and north. This paper also considers the socio-economic and environmental challenges which are resulted from water resources flows in such a case, and provides some countermeasures on how to promote water resources to flow healthily and swimmingly, so as to improve the urban development constrained by scarce water resources.

The water footprint is an indicator of freshwater consumption that looks not only at direct water consumption of a consumer or producer, also at the indirect water consumption. The water footprint can be regarded as a comprehensive indicator of freshwater resources appropriation, next to the traditional and restricted measure of water withdrawal. Based on the concept and calculating method of water footprint, this paper estimates the water footprint of China in 2007. The result shows that the total water footprint of China is 856.34 x 10(9) m(3) and the per capita water footprint is 648.11 m(3)/year. The spatial difference of per capita water footprint is obvious among all provinces of China. Generally, the more developed cities, the southern and coastal provinces have a higher per capita water footprint, lower water footprint intensity and higher efficiency of water consumption, while the North West China has lower water utilization efficiency. China is one of the thirteen water scarce countries in the world and spatial distribution of water resources is non-uniform. In addition to the virtual water trade, government should apply advanced technology and best available management practices, improve the efficiency of water use, reduce virtual water content per unit product, and continue nation-wide readjustment of industrial structure to guarantee an efficient use of limited water resources.

Virtual water, understood as the volume of water needed to produce a good or service, in the context of trade among countries, allows assessing the relative dependency of different countries on imported virtual water. The assessment of virtual water flows in virtual water trade studies is generally carried out at the national level, thus concealing the spatial variability of many countries that comprise a wide range of agro-climatic areas. A finer spatial resolution is needed to apply the virtual water concept with a view to improving local water resources management at the regional or basin scale. This paper presents a more detailed analysis of blue agricultural virtual water at sub-basin scale, which is aggregated to the basin scale for the Guadalquivir River basin in southern Spain. Given that around 80% of the available blue water resources of this region are used in agriculture, improving irrigation water management is of great interest to the basin water resources management. The main objective of this paper is to estimate the virtual irrigation water balance; an important component of the agricultural water footprint that provides additional information to the basin blue water balance and contributes to achieving a more rational and efficient management of basin water resources. Management recommendations focusing on the spatial redistribution of irrigated crops according to both their water efficiency and productivity are proposed with the aim of saving blue water for other purposes such as drought mitigation or environmental flows, among others. In particular, the proposed measures affect irrigated olive trees; the most widespread irrigated crop in this basin.

In the field of Ecological Economics, the need of using physical indicators to analyse economic processes, at the same time they serve as tools in decision making, has been lately highlighted. Virtual Water (VW) and Water Footprint (WF) are two useful indicators in achieving this objective, the first one from the perspective of production, the second one from that of consumption. This difference between them is interesting inasmuch as it allows to identify the subjects who are responsible for water consumption, whether producers or consumers, and proves both indicators’ potential when designing water management policies. In this work, we consider a hypothesis according to which there is a clear difference between the two concepts—Virtual Water and Water Footprint—and this difference, although evident in their respective conceptualizations, is not reflected in their estimations and applications. This is true to the point that the two concepts are often used as synonyms, thus wasting the enormous potential associated to their difference. Starting from this hypothesis, our objective is, first of all, to highlight this evident but ignored difference between VW and WF through a deep and thorough literature review of the conceptual definitions and contributions, the methodologies developed and the applications made regarding the two concepts. Second, we intend to make a conceptual and methodological proposition aimed at underlining the differences already mentioned and to identify responsibilities in water consumption. We do it by broadening the context of analysis and by integrating the production–consumption binomial and water–energy nexus.

The topic of virtual water has received substantial attention in recent years, both in scholarly literature and the popular press. Many authors have described the “flow of virtual water” between countries that engage in the trade of agricultural crops and livestock products. Some have suggested that water-short countries should import water-intensive agricultural products from water-abundant countries, while using their limited domestic water resources for higher valued activities. While compelling at first, such a policy prescription can be misleading. Virtual water is a helpful phrase for describing the water required to produce agricultural products and other goods. Discussions of virtual water have been effective in encouraging public officials and citizens to focus on water scarcity issues. Yet the phrase is not based on an underlying conceptual framework. Hence, the virtual water perspective cannot be used alone as a criterion for selecting optimal policies. Trading strategies based on the virtual water perspective are not consistent with the economic concept of comparative advantage. In a similar fashion, distinguishing between the “blue water” and “green water” components of virtual water is helpful in a descriptive sense, but these phrases are not based on an underlying conceptual framework that can serve as a policy criterion for selecting among alternative policy options.

Understanding the virtual water trade concept and strategy is important for formulating informed policies for improving water use efficiency at different levels. However, the introduction of virtual water concept as a policy option in Egypt is still in need for extensive investigations, research, and feasibility evaluation. Currently, Egypt’s net virtual water import as a percentage of water resources has mounted to be 23.55%. The main concern, here, is to apply the concept of virtual water as a strategy in a way that meets its interests and objectives defined in the Egyptian National Water Resources Plan. This paper is primarily concerned with investigating the prevailing water/food situation in Egypt. It outlines water and food security situation and figures, as well as policy measures undertaken to meet the challenges. The role of ‘virtual water’ within a broader policy framework is demonstrated using crop production and international trade data from Egypt, where substantial amounts of ‘virtual water’ is embodied in wheat and maize imports. It is argued that for a country like Egypt, affordability of applying the virtual water concept may not be a major problem, but more the priority and independency related to food security. In order to adopt the application of virtual water concept in the national water resources strategy of Egypt, there is a need for a clear vision and understanding of its advantages and disadvantages according to the Egyptian conditions. This new concept as a policy option in Egypt requires further research and thorough understanding of the impacts and interactions on the local social, economic, environmental, cultural, natural, and political situation.

The continuous high demand of water resources for agricultural uses in Jordan is leading to a water crisis. A possible partial solution may be to import food which requires large amounts of water to grow instead of cultivating high water consuming crops. Crops such as banana and citrus cause a huge virtual water loss, which can be reduced by cultivating other less water-demanding crops. This paper focuses on analyzing the economic value of cultivating tree fruit from a virtual water perspective. The virtual water calculations in this study depend on the average rainfall, water quota, and the crops’ water requirements (CWR). The gross profit to the water use ratio showed that banana has the lowest value 0.085 JD/m3, while lemon has the highest value 1.65 JD/m3. The calculations show that the average embedded water in fruits varies from about 470 m3/ton for grapes to about 2,500 m3/ton for dates. Banana and citrus plantations consume about 21 and 71 million cubic meters (MCM) annually, respectively, which represent about 85% of the total water consumption in fruit tree plantation. The virtual water flow estimation embedded in fruits shows that Jordan imports about 77 MCM per year. However it exports about 29 MCM per year. The results were analyzed from an integrated water resources management (IWRM) perspective. The analysis shows that a way to recover some of the water costs involved in, e.g., banana production would be to increase the fertilizer cost by about 10%. This would double the water cost and increase the banana production cost by about 6.8%. Using this alternative could be a way to better manage the huge losses in virtual water involved in banana production in the Jordan Valley.

Water has traditionally been considered a physically scarce resource in Northwestern China, and most investigations of water scarcity focus on the finite nature of water supplies. Based on the input–output analysis, this paper establishes a number of indicators of water consumption to analyze the structural relationships between economic activities and their physical relationships with the water resources. These indicators allow us to calculate the level of total water consumed by each sector and to distinguish between direct and indirect consumption, thus, offering the possibility of tracing the source of indirect water consumption. By drawing on the water consumption in Zhangye, a city situated in Northwestern China which is characterized by water shortage, we have discussed how the “problem” of scarcity has been constructed in this area. It is shown that the expanding agriculture and the unsuitable trade structure of exports and imports are likely to be responsible for the increasing scarcity of water in Zhangye. As a result, it seems that the problem of water scarcity in Zhangye is not necessarily a given, but instead the results of poor resource use, coordination and inadequate resource management.

Virtual water is the water required to produce food or a commodity, and includes rainwater in addition to irrigation and the water required to grow feed in livestock systems. Measuring virtual water is a useful concept in assessing water management as it permits the comparison of crops and livestock from the perspective of embedded water. To evaluate trade-offs in water allocation in countries like Canada with large regional variability in climate, virtual water should be calculated on a watershed scale. Two watersheds in Canada were selected representing wet and dry regions, and virtual water requirements for crop and livestock products were evaluated. For both the Lower Fraser Valley and the Okanagan basins, the results indicate that the most water demanding agricultural activities are livestock and fodder production. In the Lower Fraser basin, berry crops require 32 Mm3 of virtual water per year and have a potential value of $95 million. In contrast, the major fruit crops in the Okanagan require 63 Mm3 of virtual water per year and have a potential value of $68 million. Blueberries and grapes which have moderately high virtual water contents have been expanding in the Lower Fraser and Okanagan basins respectively. Water to grow feed dominates overall animal virtual water requirements. Livestock requires nearly 4.5 times more virtual water per year than crops in the Lower Fraser, poultry and dairy having the largest virtual water requirements. In the dry Okanagan basin the total virtual water requirements for crops and livestock are similar. To accommodate future growth, decisions on water management will need to be made, particularly in dry basins such as the Okanagan. Virtual water calculations provide information that can assist decision makers in the strategic choices of reallocation and conservation water use.

A 0.5-degree grid-based assessment of the scarcity of global water resources including virtual water trading has been made. The three components of water availability considered for each grid were local runoff, routed flow from upstream and virtual water trading. Several assumptions were postulated to convert country-base estimations of virtual water trading to grid values. The results show that unequal spatial distribution of global water resources had been considerably neutralized by virtual water trading. A large proportion of people in the Middle-East, North-Africa and Sub-Sahara region are able to relieve their water stress through virtual water import. The paper also reports two hypothetical scenarios with extremes of natural flow availability based on the presence and absence of routed upstream flow.

The argument that economies that face acute water scarcity problems can and should meet their water demand for food through cereal imports from water-rich countries; and that virtual water trade can be used to achieve water securities has become dominant in global water discussions. Analysis of country level data on renewable freshwater availability and net virtual water trade of 146 nations across the world shows that a country's virtual water trade is not determined by its water situation. Some countries have the advantage of high “economic efficiency” in food production and have surplus water, but resort to food import, whereas some water scarce countries achieve high virtual water trade balances. Further analysis with a set of 131 countries showed that virtual water trade increased with increase in gross cropped area. This is because of two reasons: First, when access to arable land increases, the ability to utilize available blue water for irrigation increases. Second, increasing access to arable land improves the access to water held in the soil profile as “free good”, a factor not taken into account in assessing water availability. Hence, many of the humid, water-rich countries will not be in a position to produce surplus food and feed the water scarce nations; and virtual water often flows out of water-poor, land rich countries to land-poor water-rich countries. This means that “distribution of scarcity” and “global water use efficiency”, are goals that are difficult to achieve through virtual water trade in a practical sense. For a water-poor, but land rich country, virtual water import offer little scope as a sound water management strategy as what is often achieved through virtual water trade is improved “global land use efficiency”. The important policy inferences emerging from the analyses are two: First, assessing the food security challenges posed to nations in future purely from a water resource perspective provides a distorted view of the food security scenario. National policies on food security should take into account “access to arable land” apart from water availability. Second, analysis of water challenges posed by nations purely from the point of view of renewable water availability and aggregate demands will be dangerous. Access to water in the soil profile, which is determined by access to arable land, would be an important determinant of effective water availability.

This study aims to estimate the green, blue and grey water footprints (WFs) of nine primary crops production in 75 districts, 5 developmental regions and 3 physiographic divisions of Nepal using local meteorological, agronomical and irrigation data at high spatial resolution. The estimates are based on the framework prescribed by the guideline of the Water Footprint Network. The green and blue WFs are calculated using a water balance model whereas the grey WF is estimated as the volume of freshwater needed to dilute nitrate pollution to an acceptable level. WF varies across different crops considered, different districts, development regions and physiographic divisions. WF of potato and wheat in Nepal is comparable to the world average; but paddy, barley and pulses have higher while sugarcane and maize have lower values compared to the world average. WFs of paddy, maize, potato and wheat are lower in Terai than the Hills and Mountains due to the accessibility of irrigation system and higher crop yield. Millet, pulses, oilseeds and barley have lower WFs and are suitable for Mountains. Similarly, sugarcane is suitable for both Terai and Mountain divisions because of its lower WF. Crops in Far Western Development Region generally have higher WFs due to the low crop productivity, and higher fertilizer use.

Kenya’s cut-flower industry has been praised as an economic success as it contributed an annual average of US$ 141 million foreign exchange (7 % of Kenyan export value) over the period 1996–2005 and about US$ 352 million in 2005 alone. The industry also provides employment, income and infrastructure such as schools and hospitals for a large population around Lake Naivasha. On the other hand, the commercial farms have been blamed for causing a drop in the lake level, polluting the lake and for possibly affecting the lake’s biodiversity. The objective of this study is to quantify the water footprint within the Lake Naivasha Basin related to cut flowers and analyse the possibility to mitigate this footprint by involving cut-flower traders, retailers and consumers overseas. The water footprint of one rose flower is estimated to be 7–13 litres. The total virtual water export related to export of cut flowers from the Lake Naivasha Basin was 16 Mm3/yr during the period 1996–2005 (22 % green water; 45 % blue water; 33 % grey water). Our findings show that, although the decline in the lake level can be attributed mainly to the commercial farms around the lake, both the commercial farms and the smallholder farms in the upper catchment are responsible for the lake pollution due to nutrient load. The observed decline in the lake level and deterioration of the lake’s biodiversity calls for sustainable management of the basin through pricing water at its full cost and other regulatory measures. Pricing water at full marginal cost is important, but the conditions in Kenya are unlikely to result in serious steps to full-cost pricing, since many farmers resist even modest water price increases and government is lacking means of enforcement. We propose an alternative in this study that can be implemented with a focus on sustainable water use in flower farming around Lake Naivasha alone. The proposal involves a water-sustainability agreement between major agents along the cut-flower supply chain and includes a premium to the final product at the retailer end of the supply chain. Such a ‘water sustainability premium’ will raise awareness among flower consumers and—when channelled back to the farmers—facilitate the flower farms to install the necessary equipment and implement the right measures to use water in a sustainable manner. The collected premiums will generate a fund that can be used for financing measures to reduce the water footprint and to improve watershed management.

For a hardcopy of this article, printed in the Netherlands, an estimated 100 l of water have been used. Most of the water is required in the forestry stage, due to evapotranspiration (green and blue water). In addition, the water footprint during the industrial stage, as accounted for in this study, consists of evaporation from water obtained from ground water and surface water (blue water). In this study estimates are made of water requirements for producing paper using different types of wood and in different parts of the world. The water footprint of printing and writing paper is estimated to be between 300 and 2600 m3/t (~2-13 l for an A4 sheet). These estimates account for paper recovery rates in different countries. This study indicates that by using recovered paper for the production of paper the global average water footprint of paper is only 60% of what it would be if no recovered paper would be used at all. Further savings may be achieved by increasing the recovery percentages worldwide. In addition, the global water footprint of paper can be reduced by choosing production sites and wood types that are more water-efficient. The results of this study suggest that the use of recovered paper may be particularly effective in reducing water footprints. This study is a first step towards a better understanding of the significance of the water footprint of paper and the effect of using recovered paper.

This paper reviews the evolvement of water footprint assessment (WFA) as a new research field over the past fifteen years. The research is rooted in four basic thoughts: (1) there is a global dimension to water management because water-intensive commodities are internationally traded, so we must study virtual water trade and the effects of countries externalizing their water footprint; (2) freshwater renewal rates are limited, so we must study the development of consumption, production and trade patterns in relation to these limitations; (3) supply-chain thinking, previously uncommon in water management, can help to address sustainable water use from the perspective of companies and final consumers; and (4) a comprehensive approach requires the consideration of green in addition to blue water consumption, the traditional focus in water management, and the analysis of water pollution in the same analytical framework as well. The quick emergence of the new field and wide uptake of the water footprint concept in society has generated substantial discussion about what the concept in narrow sense and the research field in broader sense can offer and what not. The paper reflects on the main issues of debate.