Total Virtual Water Research Articles

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

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

An integrated assessment of the global virtual water trade network of energy

The global trade of energy allows for the distribution of the world’s collective energy resources and, therefore, an increase in energy access. However, this network of trade also generates a network of virtually traded resources that have been used to produce energy commodities. An integrated database of energy trade water footprints is necessary to capture interrelated energy and water concerns of a globalized economy,and is also motivated by current climate and population trends. Here, we quantify and present the virtual water embedded in energy trade across the globe from 2012 to 2018, building on previous water footprinting and energy virtual water trade studies to create an integrated database. We use data from the United Nations Comtrade database and combine several literature estimates of water consumption of energy commodities to generate the global virtual water trade network. Results include a comprehensive database of virtual water trade for energy at the country level, greatly expanding the literature availability on virtual water trade. The total volume of virtual water trade increased 35% from 157 km3 in 2012 to 211 km3 in 2018. The global trade of oil and fuelwood are consistent drivers of virtual water trade over time, whereas coal, hydrocarbons, and charcoal collectively contribute less than 4% of total virtual water trade between 2012 and 2018. Electricity, despite a less dense trade network constrained by infrastructure, contributes notably to virtual water trade, driven largely by water use for hydroelectricity. This study develops an integrated assessment of previous virtual water studies to estimate global virtual water trade of energy, creating a platform for future global studies.

Analysis of spatial distribution characteristics of virtual water content of maize in China

Research on virtual water content of crops can provide the basis for agricultural water resources management; help to improve the efficiency of agricultural water use. Maize is one of the most important food crop in China and also one of the largest water consumers, so it is important to study the virtual water content (VWC) of maize and the spatial distribution characteristics of the VWC of maize in China. In this paper, we assessed the VWC of maize in China including green, blue, grey water and analyze the spatial distribution characteristics of the VWC of maize of 30 regions of China. The percentages of green, blue, and grey water in the total VWC of maize in China were 47.5%, 18.9%, and 33.6%. The total VWC of maize generally showed a three-tiered distribution, and decreased from southeast to northwest. For the country as a whole the green water is the most important contributor. The percentage of grey water of maize was much larger than blue water. Blue water occupied the smallest component of the total virtual water content of maize.

Assessment of Main Cereal Crop Trade Impacts on Water and Land Security in Iraq

Growing populations, socio-economic development, the pollution of rivers, and the withdrawal of fresh water are all signs of increasing water scarcity, and with 85% of global use, agriculture is the biggest freshwater user. The water footprint (WF) and virtual water (VW) are concepts used recently for freshwater resources assessment. The WF reflects how much, when and where the water was used whereas VW reveals the volume of water embedded in goods when traded. The first goal of this research is to determine the WF per ton and the WF of production (Mm3/yr) of wheat, barley, rice, and maize in Iraq. The second goal is estimating the quantities of the 4 main cereal crops imported into Iraq and assessing the impact on reducing WF and land savings for 10 years from 2007 to 2016. The results showed that the WF per ton was 1736, 1769, 3694, 2238 m3/ton and the WF of production was 5271, 1475, 997, 820 Mm3/yr for wheat, barley, rice, and maize, respectively. The median total VW imported was 4408 Mm3/yr, the largest volume was 3478 Mm3/yr from wheat, and Iraq saved about 2676 Mm3 of irrigated water and 1,239,539 M ha of land by importing crops every year during 2007–2016. The study revealed the significance of better irrigation management methods to decrease the WF through a selection of crops that need less water and cultivation in rain-fed areas, as well as the use of cereal import to conserve scarce water resources, which is crucial both in terms of water resource management and preservation of the environment. The results of this research could be used as a guideline for better water management practices in Iraq and can provide helpful data for both stakeholders and policymakers.

Virtual water flows under projected climate, land use and population change: the case of UK feed barley and meat

The flow of water through food commodity trade has been rationalized in the virtual water concept. Estimates of future virtual water flows under climate, land use, and population changes could have instrumental value for policy and strategic trade decisions. This paper estimated the virtual water flows associated with feed barley and meat imports to the UK under projected climate, land use, and population changes from the 2030s to the 2050s. The results show that future virtual water inflows associated with barley imports to balance domestic deficits are larger than total volume of water used in domestic barley production in the UK. Mean virtual water associated with total UK barley production ranged from 206 to 350 million m3. This is much less than the mean total virtual water associated with barley imports (if total barley produced in the UK is used for feed), which ranged from 2.5 to 5.6 billion m3 in the 2030s to the 2050s for all land use and climate change scenarios. If domestic barley production is distributed to the different end uses, the total virtual water inflows associated with imports to balance domestic feed barley supply could be as high as 7.4 billion m3. Larger virtual water inflows (as high as 9.9 billion m3) were associated with feed barley equivalent meat imports. While the UK barley production would be entirely green, imports of either barley or meat would result in large blue water inflows to the UK. Virtual water inflows increased across the time slices for all emissions scenarios, indicating weak effectiveness of yield or productivity gains to moderate virtual water inflows. While increase in yield and land allocated to barley production should be adaptive targets, the UK needs to take policy and strategic actions to diversify trade partners and shift imports away from countries where blue water flows can exacerbate existing or potential water stresses.

Sustainable Water Use for International Agricultural Trade: The Case of Pakistan

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’s looming water scarcity, exporting large volumes of blue virtual water may constrain the country’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.

New estimates of water footprint for animal products in fifteen countries of the Middle East and North Africa (2010–2016)

The Middle East and North Africa region (MENA) is one of the most water-scarce worldwide. Up-to-date estimates of the origin and types of water use in various industries are necessary to manage water resources and guide food and water policies. The objective of this study is to determine new estimates for the color-coded water footprint (WF). Using the Water Footprint Network approach, country-specific blue, green and grey WFs and total virtual water were calculated for 2010–2016 using recent production data. We find that animal production in MENA increased by 50% as compared to the previous decade. Virtual water consumption account for more than 80 billion m3 annually, mostly for beef (61%), followed by broilers (20%), and sheep (17%). 40% of which is local. Almost 50% of the feed grains used in the region are produced locally, accounting for 40% of the total WF for animal production in MENA.

Virtual water flow pattern of grain trade and its benefits in China

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

Assessment of Agricultural Water Resources Sustainability in Arid Regions Using Virtual Water Concept: Case of South Khorasan Province, Iran

Cropping pattern plays an important role in providing food and agricultural water resources sustainability, especially in arid regions in which the concomitant socioeconomic dangers of water shortage would be inevitable. In this research, six indices are applied to classify 37 cultivated crops according to Central Product Classification (CPC). The respective 10-year data (2005–2014) were obtained from Agricultural Organization of South Khorasan (AOSKh) province. The water footprint concept along with some economic indicators are used to assess the water use efficiency. Results show that blue virtual water contributes to almost 99 percent of Total Virtual Water (TVW). In this occasion that an increasing pressure is exerted on groundwater resources, improper pattern of planting crops has to be beyond reproach. The improper cropping pattern in the study area led to the overuse of 346 × 106 m3 of water annually. More specifically, cereals cultivation was neither environmentally nor economically sustainable and since they accounted for the largest share of water usage at the province level, importing them should be considered as an urgent priority. Vegetable cultivation could be further increased—instead of other water-intensive crops such as fruits—at the province level, not only due to their low TVW, but also to their higher financial output.

Virtual water flow in food trade systems of two West African cities

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

Drivers of virtual water flows on regional water scarcity in China

Previous studies had shown that the virtual water flows had intensified local water scarcity of China. There is an urgent need to identify the drivers of virtual water flows and provide the potential options to reduce the impact of virtual water flows on regional water scarcity. Based on the multi-regional input-output model and structural decomposition analysis, we evaluated the redistribution of water withdrawal within China in 2002, 2007 and 2012, and then revealed the hidden driving forces of the changes in virtual water flows. For a specific province, the drivers had been divided into local and the rest of China. Here we found that: (1) The share of virtual water flows in interregional trade to total water withdrawal had increased (from 20.1% to 40.5%) during the study period. (2) The direction of virtual water flows has reversed between some Chinese regions. Northwest and Northeast regions have become the major virtual water exporters. (3) The virtual water flows hidden in traded products of agriculture, electricity and the chemical industry accounted for more than 83% of total virtual water flows. (4) Local efficiency gains and consumption pattern changes in other provinces were the main drivers for changes in virtual water flows. The water-scarce Northwest and Northeast of China had further increased virtual water export to the water-rich provinces in southern China. This trend could be curbed by improving water use efficiency and restraining water-intensive consumption. Our results could pinpoint areas to invest in water use efficiency and provide guidance for areas to restrain water-intensive consumption.

Impact of virtual water flow with the energy product transfer on sustainable water resources utilization in the main coal-fired power energy bases of Northern China

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

The virtual Water flow of crops between intraregional and interregional in mainland China

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

Optimisation of cropping pattern considering stomatal response to elevated CO<sub align="right">2 emission and climate change

The current article seeks to explore the function of elevated CO2 emission on the variations of reference evapotranspiration (ET0) for optimising cropping pattern in 18 Iranian regions. Accordingly, meteorological data and agricultural information were collected since 1961 to 2010 and 2002 to 2013, respectively. A trend-free pre-whitening (TFPW) approach was applied to modify Mann-Kendall test to determine the ET0 trend based on the Food and Agriculture Organization of the United Nation (FAO)-Penman-Monteith (FPM) method. Then, the function of stomatal response was investigated as an assimilation coefficient to adjust the ET0 since 2050 to 2100. In the next step, the anomalies of the ET0 were calculated in both monthly and annual scales with respect to the significant trends of the meteorological parameters and stomatal response via three different schemes. Finally, to optimise cropping pattern, two indicators namely total virtual water (TVW) and unit blue water value (UBWV) were employed.

Optimisation of cropping pattern considering stomatal response to elevated CO<sub align="right">2 emission and climate change

The current article seeks to explore the function of elevated CO2 emission on the variations of reference evapotranspiration (ET0) for optimising cropping pattern in 18 Iranian regions. Accordingly, meteorological data and agricultural information were collected since 1961 to 2010 and 2002 to 2013, respectively. A trend-free pre-whitening (TFPW) approach was applied to modify Mann-Kendall test to determine the ET0 trend based on the Food and Agriculture Organization of the United Nation (FAO)-Penman-Monteith (FPM) method. Then, the function of stomatal response was investigated as an assimilation coefficient to adjust the ET0 since 2050 to 2100. In the next step, the anomalies of the ET0 were calculated in both monthly and annual scales with respect to the significant trends of the meteorological parameters and stomatal response via three different schemes. Finally, to optimise cropping pattern, two indicators namely total virtual water (TVW) and unit blue water value (UBWV) were employed.

Worse than imagined: Unidentified virtual water flows in China

The impact of virtual water flows on regional water scarcity in China had been deeply discussed in previous research. However, these studies only focused on water quantity, the impact of virtual water flows on water quality has been largely neglected. In this study, we incorporate the blue water footprint related with water quantity and grey water footprint related with water quality into virtual water flow analysis based on the multiregional input-output model of 2007. The results find that the interprovincial virtual flows accounts for 23.4% of China's water footprint. The virtual grey water flows are 8.65 times greater than the virtual blue water flows; the virtual blue water and grey water flows are 91.8 and 794.6 Gm3/y, respectively. The use of the indicators related with water quantity to represent virtual water flows in previous studies will underestimate their impact on water resources. In addition, the virtual water flows are mainly derived from agriculture, chemical industry and petroleum processing and the coking industry, which account for 66.8%, 7.1% and 6.2% of the total virtual water flows, respectively. Virtual water flows have intensified both quantity- and quality-induced water scarcity of export regions, where low-value-added but water-intensive and high-pollution goods are produced. Our study on virtual water flows can inform effective water use policy for both water resources and water pollution in China. Our methodology about virtual water flows also can be used in global scale or other countries if data available.

Intra-EU agricultural trade, virtual water flows and policy implications

The development of approaches to tackle the European Union (EU) water-related challenges and shift towards sustainable water management and use is one of the main objectives of Horizon 2020, the EU strategy to lead a smart, sustainable and inclusive growth. The EU is an increasingly water challenged area and is a major agricultural trader. As agricultural trade entails an exchange of water embodied in goods as a factor of production, this study investigates the region's water–food–trade nexus by analysing intra-regional virtual water trade (VWT) in agricultural products. The analysed period (1993–2011) comprises the enactment of the Water Framework Directive (WFD) in the year 2000. Aspects of the VWT that are relevant for the WFD are explored. The EU is a net importer of virtual water (VW) from the rest of the world, but intra-regional VWT represents 46% of total imports and 75% of total exports. Five countries account for 60% of total VW imports (Germany, France, Italy, The Netherlands, Belgium) and 65% of total VW exports (The Netherlands, France, Germany, Belgium and Spain). Intra-EU VWT more than doubled over the period considered, while trade with extra-EU countries did not show such a marked trend. In the same period, blue VWT increased significantly within the region and net import from the rest of the world slightly decreased. Water scarce countries, such as Spain and Italy, are major exporters of blue water in the region. The traded volumes of VW have been increasing almost monotonically over the years, and with a substantial increase after 2000. The overall trend in changes in VWT does not seem to be in accordance with the WFD goals. This study demonstrated that VWT analyses can help evaluate intertwining effects of water, agriculture and trade policies which are often made separately in respective sectors.

The spatiotemporal variation analysis of virtual water for agriculture and livestock husbandry: A study for Jilin Province in China

With the rapid development of economic, water crisis is becoming more and more serious and would be an important obstacle to the sustainable development of society. Virtual water theory and its applications in agriculture can provide important strategies for realizing the reasonable utilization and sustainable development of water resources. Using the Penman-Monteith model and Theil index combining the CROPWAT software, this work takes Jilin Province as study area quantifying the virtual water content of agriculture and livestock husbandry and giving a comprehensive evaluation of their spatiotemporal structure evolution. This study aims to help make clear the water consumption of agriculture and livestock husbandry, and offer advice on rational water utilization and agricultural structure adjustment. The results show that the total virtual water (TVW) proportion of agriculture presents a gradual growth trend while that of livestock husbandry reduces during the study period. In space, central Jilin shows the highest virtual water content of agriculture as well as livestock husbandry, the TVW in central Jilin is about 35.8billionm3. The TVW of maize is highest among six studied crops, and the cattle shows the highest TVW in the four kinds of animals. The distribution of TVW calculated by us and the distribution of actual water resources have remarkable difference, which leads to the increase of water consumption and cost of agricultural production. Finally, we discuss the driving force of the spatiotemporal variation of the TVW for agriculture and livestock husbandry, and also give some advises for the planting structural adjustment. This work is helpful for the sustainable development of agricultural and livestock husbandry and realizing efficient utilization of water resources.

Evaluation of external virtual water export and dependency through crop trade: an Asian case study

The aim of this study was to evaluate virtual water export through five crops (barley, rice, maize, soybeans, and wheat) in terms of the external virtual water rate, within and outside of Asia from 2000 to 2012, and in comparison with that within and outside the European Union (EU). The external virtual water rate indicates the proportion of virtual water export outside of a boundary. Approximately 46.9% of the green water exports and 40.9% of the blue water exports were discharged from Asia to non-Asian countries. For example, Thailand, which is the main exporter in Asia, exported 55.5% of the total virtual water exported to non-Asian countries, and Kazakhstan exported 63.8% of the total virtual water exported to European countries. In comparison, the external virtual water rate for the EU was 30.2% (green water) and 25.2% (blue water). The virtual water trade is also important to the main importers in Asia. We evaluated the virtual water dependency on exporters in East Asia of Japan, Korea, and Taiwan. These three countries have a high dependency on virtual water imported from only a few exporters; thus, they should extend their virtual water trade boundary to include additional exporters. These results provide information necessary for the development of an integrated water strategy in Asia, and could convince the main Asian importers of the risks of serious dependency on foreign water resources.

Virtual water embodied in the export from various provinces of China using multi-regional input–output analysis

China is a large exporter and consumer of water embodied in export products. In addition, there is much trade among regions within China, and exports from various provinces consume not only local water but national non-local water. However, former calculations of the water consumption embodied in the exports of various provinces do not reflect the sources of the water consumption. Previous studies on virtual water in China's exports have focused on national aggregate analyses and have paid little attention to the inter-regional water consumption transfer driven by exports. We used a multi-regional input–output model of thirty provinces to examine the virtual water export. The results show that the total virtual water in China's exports was 106.3 billion m3, and 77.0% of the embodiment was from exports from the eastern provinces, where over 90% of China's exports occur. However, the virtual water driven by per unit of export in the eastern regions is far less than that in the central and western regions. Moreover, the central and western provinces, whose exports are small, indirectly export much virtual water by supporting eastern China's exports via inter-regional economic linkages. The results yield important implications for China's export and virtual water export control policy.