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Water consumption, energy use, and carbon emission are three related key anthropogenic impacts on the natural environment. China is the largest carbon emitter and energy consumer, with the serious unevenly distributed water resources. Therefore, investigating the water–energy–carbon (WEC) nexus is important for China's environmental footprint reduction. This study explores the relation between water utilization, energy consumption, and carbon emission in China, based on a multiregional input–output (MRIO) analysis. The WEC nexus is discussed comprehensively in consideration of the utilization of water and energy and the emission of carbon, as well as the trade to and from and the consumption activities in different sectors and provinces. Results show that water, energy, and carbon present significant consistency in production and consumption processes. Sectors with higher consumption coefficients dominate the transfer of virtual WEC. Although virtual WEC mainly transfers from less developed regions to relatively developed regions, Category 1 (i.e., WEC all import) and category 2 (i.e., WEC disaccord) present opposite results to and category 3 (i.e., WEC all export) provinces in terms of W–E and W–C nexus. The net water and energy transfers are significantly positively correlated in category 1 provinces, whereas both sides are negatively correlated in category 2 and 3 provinces. This phenomenon also exists in the relationship between net water and carbon transfers. The virtual water, as well as energy and carbon export pressures are dispersed in these export provinces. Findings of this study are expected to assist the government in decreasing the environmental footprints and achieve sustainable development in China.

The water exported indirectly by sending products to other countries,or vice versa, is called a virtual water flow and this can be measuredthrough water footprint (WF) calculations, which represent theembedded water needed to manufacture a product. This presentstudy aims to analyze the virtual water flow and the WF of the mainproducts exported by municipalities in the state of Ceará in the year2019, in order to enhance the management of the state’s waterresources. Analytical hierarchy process (AHP), the most commonlyused multicriteria decision-making method in the world, was usedto determine which product is more sustainably produced by themunicipalities of Ceará, with the criteria: WF, price, and volumeexported. The alternatives are at least two of the seven categories ofproducts exported by the state where the “fruit or vegetable juices”class was preferred as the most sustainable. It was found that mostcities in the state that export agricultural products use only onebasin, which can lead to very low reservoir levels, while the otherhydrographic basins in the state are underused. It is worth noting thatthe Metropolitan Basin concentrates on 11 out of 32 municipalitiesthat export abroad and that it is responsible for supplying more than4,074,730 inhabitants, according to Brazilian Institute of Geographyand Statistics (IBGE, 2019). A água exportada indiretamente pelo envio de produtos a outros países,ou vice versa, chama-se fluxo de água virtual e pode ser mensurado porcálculos de pegada hídrica, que representam a água embutida necessáriapara a fabricação de um produto. O presente estudo teve o objetivo deanalisar o fluxo de água virtual e a pegada hídrica dos principais produtosexportados por municípios do estado do Ceará no ano de 2019, a fim depotencializar o gerenciamento dos recursos hídricos do estado. Utilizouseo analytical hierarchy process (AHP), método de tomada de decisãomulticritério mais usado no mundo, aqui escolhido para determinar qualo produto mais sustentável produzido pelos municípios do Ceará, comos critérios: pegada hídrica, preço e volume exportado. As alternativassão pelo menos duas das sete categorias de produtos exportados peloestado, e a classe de “sucos de frutas ou vegetais” foi preferida comoa mais sustentável. Constatou-se que a maioria das cidades do estadoque exportam produtos de origem agropecuária faz uso de apenasuma bacia, o que pode acarretar níveis muito baixos de reservatório,enquanto as outras bacias hidrográficas do estado são subusadas. Vale apena salientar que a Bacia Metropolitana concentra 11 de 32 municípiosque exportam para o exterior e é responsável pelo abastecimentode mais de 4.074.730 habitantes, segundo o Instituto Brasileiro deGeografia e Estatística (2019).

To consider the problem of uneven distribution of water resources, a study on the relationship and trend of virtual water trade between regions based on an Multi-Regional Input-Output (MRIO) model was proposed. Using an MRIO model, the spatial distribution and changing trends of China's inter-regional virtual water trade from 2014 to 2019 were evaluated. The empirical results show that, due to the difference in water use efficiency and production processes in different sectors, the direct and indirect water use coefficients and demand coefficients are different in different regions. In some water-poor areas (regions with low water availability), more products with high water use coefficients are exported, while more water-rich areas (regions with high water availability) export products with lower water use coefficients. The inter-regional virtual water trade only alleviates the shortage of water resources in some poor water areas in China. Some poor water areas export a large amount of virtual water, and the rich water areas import a large amount of virtual water or only maintain a partial virtual water balance. However, the demand coefficient tends to increase, and the trade adjustment trends in different regions and changes in regional virtual water trade relations are not conducive to alleviating the shortage of water resources caused by uneven distribution. The tension coefficients between the food manufacturing and tobacco processing industry, the textile and clothing industry, and the wood processing and furniture manufacturing industries in the Northeast region are relatively large, with the demand coefficients are 92.9, 65.5 and 156.7 respectively. Relatively speaking, the tensile coefficients of areas rich in natural water resources such as the eastern coastal, southern coastal, southwest, and central areas are generally low. According to the production situation, the regional virtual water trade relationship should be adjusted from the level of the national master plan.

One of the most crucial issues in water and food security is to assess the impacts of climate change on virtual water content (VWC) and crop yield of agricultural products. The objective of this study is to efficiently predict the VWC patterns and yields of different crops under various climate change conditions using three data mining approaches including artificial neural network (ANN), genetic programming (GP), and support vector machine (SVM). The study region included the eastern provinces of Iran containing North Khorasan, Khorasan Razavi, South Khorasan, Sistan-Baluchestan (in a range of latitude from 25 to 40°N). Specifically, VWC and crop yields were estimated for both baseline period (1985–2005) and several climate change conditions including four time horizons (2030, 2050, 2070, and 2090) under RCPs 2.6, 4.5, and 8.5 based on the second generation Canadian Earth System Model (CanESM2). The data mining models were evaluated with the RMSE and NSE goodness-of-fit criteria. The results showed that the SVM model achieved the highest NSE and lowest RMSE values. It was also found that under the climate change conditions, VWC increased from 6 to 42%, while crop yield decreased from 8 to 53% for all products in the southern regions. An opposite trend was observed in the northern regions for wheat and barley with an increase from 12 to 72% for VWC and from 4 to 27% for the yield.

Due to the increasingly serious water shortage in China, water conservation becomes more and more important. This paper analyzes the amount of water consumption in every link of the goods supply to...

The present study aimed to assess water footprint in the production and export of rice in India. From recent few years, the water footprint conception in full swing to inward detection around the world. The amplified attention in the water footprint has impelled the trade of commodities between countries. Water footprint in the rice field is a sign of water use that exhibits direct and indirect water usage in the rice field. Rice is an important food crop in India. It accesses the flows of water virtually between countries/regions of the world to illustrate the dependency of countries/regions on water resources with other countries/regions under diverse feasible futures. Hence, it is gaining consequence to calculate the water foot print in production as well as export of rice. The Indian rice production and export of rice was calculated by using international trade and domestic production data. The study results indicated that the global footprint of rice production was 235774 Mm3 per ton which was 53 % of green water footprint, 41 % of blue water footprint and 6 % of grey water footprint for 2018-19. The virtual water flowed in trade was 24354 Mm3/year and the percolation was 16924 Mm3/year since rice is a more water consuming crop. The share of basmati and non-basmati trade accounted was 16 % and 42 %, respectively. Virtual water trade in rice can be minimized by exporting less water demand and high-value crops, proper water harvesting structures and other agronomic practices.

A dynamic multi-region computable general equilibrium (CGE) model is used to analyze virtual water and its effect in the Huaihe River basin, which includes Jiangsu, Anhui, Shandong and Henan provinces. The baseline scenario was first constructed to describe the trade situation and virtual water among different regions and sectors from 2009–2020. Then two hypothetical policy scenarios were set to analyze the economic, water consumption and virtual water trade impacts under different policy shocks. The results show that (1) the Huaihe River basin was a net virtual water outflow region, with 13.977 × 109 m3 virtual water transferred outside the river basin in 2009, and 26.653 × 109 m3 VW transferred to outside in 2020. Jiangsu is the largest virtual water outflow province (mainly flows to outside), followed by Anhui. Anhui suffers from severe water shortage, but provides a net virtual water outflow to Henan, Jiangsu and Shandong and outside; (2) reducing Anhui's agricultural output (S1 scenario) and Anhui's agricultural virtual water outflow (S2 scenario) can not only reduce virtual water trade but also save water, but S1 scenario reduced net virtual water outflow by more, and saved more water. S1 had a positive effect on gross domestic product (GDP), but reduced the employment rate. HIGHLIGHTS Role of VWT analyzed using a CGE.; CGE based on 12 years of data (2009–2020).; VW study not only focused on agriculture, but also included industry and service sectors.; Two hypothetical scenarios were set to analyze the economic, water consumption and VWT impact.; Assessment of VW will change water usage and trade in different upstream and downstream regions of the Huaihe watershed.

As the largest lake within Iranian borders, Lake Urmia's critical conditions have disrupted its primary functions in recent years due to environmental challenges. Considering the virtual water (VW)...

Water resources are becoming scarce and must be preserved. The significant use of water is linked to agriculture in general and to livestock in particular. Very little research in semi-arid regions has been devoted to assessing the contribution of ruminants to water scarcity. This contribution explores the relationships between dairy farming and the various water resources available in an ecosystem with climatic constraints. To meet future food demand while sustainably managing the available land and water resources, dairy farm systems in semi-arid regions must adapt in response to climate and socio-economic change. In this study, we focus on the south Mediterranean region to analyze the key factors influencing water productivity in dairy farming, especially in context characterized by water scarcity. In order to characterize the relationship between dairy cattle breeding and water resources, a monitoring of 40 dairy cattle stables has been carried out in a semi-arid region. The technical and economic parameters of each farm were evaluated: the use of water according to their origins to the production of fodder by source, the contribution of virtual water off the farm, the total fodder biomass, feeding system practiced on the farms and the performances achieved. Analysis of the data indicates that productivity of fodder in dry matter differ between the two systems with values of the order of 12520 to 17188 kg/ha (p

Populasi penduduk Indonesia diperkirakan akan mencapai 350 juta pada tahun 2045, mendorong Indonesia untuk meningkatkan ketersediaan pangan 3% setiap tahunnya. Program Upaya Khusus (Upsus) Padi Jagung Kedelai (Pajale), menjadi salah satu program unggulan pemerintah dalam menjawab tantangan ini. Di sisi lain, tekanan lingkungan memberikan batas jelas untuk melaksanakan proses budidaya pertanian berkelanjutan. Sebagaimana dua tujuan dari Sustainability Development Goals (SDGs) adalah menghentikan kelaparan dan kepastian akses terhadap air. Konsep air virtual (virtual water) hadir sebagai salah satu alternatif konsep berserta alat hitung air yang diperlukan dalam sebuah proses produksi pertanian. Penelitian ini dilakukan untuk mengidentifikasi air virtual untuk komoditas padi, jagung, dan kedelai di wilayah Daerah Istimewa Yogyakarta. Analisa dalam penelitian ini menghasilkan nilai tapak air yang terdiri dari blue water, green water, dan grey water. Hasil penelitian menunjukkan, bahwa water footprint tahunan kedelai merupakan yang tertinggi dengan 2.589 m3/ton disusul padi ladang, jagung, dan padi sawah sebesar 1.280 m3/ton; 844 m3/ton; 841 m3/ton. Hasil ini disebabkan oleh tingkat produktivitas yang semakin tinggi nilainya maka akan menghasil nilai water footprint akan semakin rendah. Pelaksanaan penelitian ini mengungkap faktor yang mempengaruhi jumlah air yang diperlukan untuk memproduksi komoditas pertanian. Pemilihan lokasi, kondisi iklim, jenis tanaman, teknik budidaya hingga penggunaan pupuk merupakan faktor yang perlu diperhatikan untuk dapat menekan penggunaan air dalam proses produksi pertanian. Dengan demikian, tujuan pelaksanaan budidaya pertanian yang berkelanjutan dapat terwujud.

Simulation of land and water management for the irrigated farmlands has become an interest to answer how agricultural productivity is related to the water use in a river basin. This research was undertaken in the Brantas River Basin in Indonesia, involving a modelling process with the virtual water concept as a tool to analyze water productivity. The research simulated the agricultural water demand and provided the results of the virtual water content of paddy and maize, based on the available farming land, water availability, cropping pattern and climatological conditions of the respective hydrological years of 1997 and 2011 as a benchmark. After which projections were made based on the low rainfall scenario for the years 2021 to 2025. The research concluded that the presence of excess irrigation in the tropical climates hinders the increase in agricultural productivity, and therefore, the irrigation in the Brantas River Basin needs to be improved by, among others, selecting plants with higher water productivity, developing water-sensitive cropping patterns, and water conveyance savings.

PEGADA HÍDRICA DO SISTEMA DE ABASTECIMENTO DE ÁGUA DO MUNICÍPIO DE SÃO CARLOS – SP DAIANE FERREIRA CAMPOS1 [1] Programa de Pós Graduação em Engenharia Hidráulica e Saneamento, Escola de Engenharia de São Carlos / Universidade de São Paulo, Av. Trab. São Carlense, 400 - Centro, CEP 13566-590, São Carlos – SP, Brasil, email: daianecampos.eng@gmail.com 1 RESUMO Os sistemas de saneamento estão entre os principais interconectores entre água e sociedade. Sendo perceptível que quanto maior a compreensão do recurso hídrico dentro do sistema, melhor será o gerenciamento. Seguindo esta dialética, sabe-se que o consumo de água vai além do que realmente é calculado, podendo ser analisado também, pela vertente de água virtual. Portanto, o objetivo deste trabalho é apresentar uma análise da água virtual do sistema de abastecimento de água do município de São Carlos no estado de São Paulo. Logo, a estimativa de água virtual do abastecimento urbano de água foi calculada segundo o Manual de Pegada Hídrica. Sendo utilizado os dados de vazões médias de água tratada e distribuída pelas duas unidades de tratamento de água disponibilizados pelo SAAE (Sistema Autônomo de Água e Esgoto) do município de São Carlos, em seguida foi calculado o volume de água evaporado pelo método de Penman. Após contabilizar, resultou que a pegada hídrica do sistema de abastecimento foi estimada em 22.860.960,64 m³ por ano, o que representa uma razão de 1,44 m³ entre a água virtual e a água real, de maneira que, a evaporação contribuiu com 2.320,0 m³ por ano e as perdas de distribuição representaram 7.795.587,57 m³/ano de água virtual. Palavras-chave: Pegada Hídrica; Sistemas de Saneamento; Água Virtual. CAMPOS, D. F. WATER FOOTPRINT OF THE WATER SUPPLY SYSTEM OF SÃO CARLOS - SP 2 ABSTRACT Sanitation systems are among the main interconnectors between water and society. It is noticeable that the greater the understanding of the water resource within the system, the better the management. Following this dialectic, water consumption goes beyond what is actually calculated and can also be analyzed by the virtual water aspect. Therefore, this work aims to present an analysis of the virtual water of the water supply system in the municipality of São Carlos in the state of São Paulo. Therefore, the estimate of virtual water for urban water supply was calculated according to the Water Footprint Manual. Using data from average water flows treated and distributed by the two water treatment units provided by SAAE-São Carlos, the evaporated water volume was then calculated using the Penman method. After accounting, it turned out that the water footprint of the supply system was estimated at 22,860,960.64 m³ per year, which represents a ratio of 1.44 between virtual water and real water, so that evaporation contributed to 2,320.0 m³ per year and distribution losses represented 7,795,587.57 m³/year of virtual water. Keywords: Water Footprint; Sanitation Systems; Virtual Water.

Shouguang City is located in north-central of Shandong, distributing the piedmont plain and coastal plain from the south to north. This area, as a vegetable base in northern China, not only meets local needs but also has a large number of vegetables exported to domestic and foreign countries in the form of virtual water. The vegetable production in this area mainly depends on groundwater exploitation, which causes saltwater intrusion problems. This study establishes the linear model of virtual water and vegetable production, irrigation water consumption, total population, per capita vegetable sales volume, and the purchase amount of vegetable trade. The output of vegetable virtual water from 1980 to 2012 is calculated. 3.79 billion kg of vegetables were exported in the form of virtual water with a volume of 145 million m3 in 2012, accounted for 78% of the average annual groundwater resources in the region. The vegetable trade development in Shouguang City from 1980 to 2002 can be divided into two stages: bare land vegetable cultivation in 1980–1990 and greenhouse vegetable cultivation in 1991–2002. The correlations among the annual virtual water output volume of vegetable trade, annual groundwater cumulative storage, groundwater depth at the center of depression area, and saltwater intrusion area are established and analyzed. In the first stage, for every 10 million m3 of vegetable virtual water was transferred, the salt water intrusion area in this area increased by 13.8 km2; in the second stage, the saltwater intrusion area increased correspondingly by 5 km2. The influence of saltwater intrusion on adjusting crop-planting structure is also analyzed to achieve the purpose of effectively alleviating the ecological and environmental problems in the area.

The increasing population, improving living standards, and expanding economic activities are responsible for rising water demands. In recent decades, the imbalance between water supply and demand has become increasingly prominent. Coupled with the unreasonable use of water resources, this has led to serious water scarcity problems that affect the sustainable development of modern society. Under this background, water scarcity has become an important environmental issue for our sustainable planet. Water scarcity is affected by regional water resource endowments and the ways in which water resources are developed and utilized by human beings. Quantity-induced water scarcity occurs when the quantity of water resources is insufficient. Meanwhile, pollution can cause water scarcity as the services provided by polluted water are not equivalent to that of clean water. Quality-induced water scarcity occurs when the pollutants exceed the environmental carrying capacity. Since Marlin Falkenmark first proposed the concept and assessment method of water scarcity in the 1980s, water scarcity assessment has developed for nearly 40 years. With the development of new theories, progress has been made, such as development of different approaches for assessing water scarcity, identification of influencing factors of water scarcity, revealing the formation mechanism, and exploring strategies to cope with water scarcity. As a result, water scarcity assessment has experienced an evolutionary pathway from a one-dimensional model emphasizing only quantity-induced water scarcity to a two-dimensional model (considering both quantity-induced and quality-induced water scarcity), toward a three-dimensional (3D) model (or 3D water scarcity theory) that considers water quantity, water quality, and environmental flows simultaneous. Based on a systematic review of water scarcity assessment in the literature, this study demonstrates the 3D water scarcity theory and elaborates on its basic concepts, principles, and core methods. The 3D water scarcity theory was first proposed by Chinese scholars and then accepted by international scholars. The quantity-induced water scarcity is assessed based on the ratio of water consumption to water availability, and the quality-induced water scarcity is quantified by comparing gray water footprint (the amount of water required to dilute pollutants in wastewater sufficiently to meet environmental water quality standards) with local available water resources. Environmental flow requirements are quantified based on the characteristics of climatic and hydrological conditions rather than the traditionally adopted simple approach by assuming that they are equal to 80% of water resources. Hence, the 3D water scarcity theory and assessment method can consider water quantity, water quality, and environmental flow requirements comprehensively. Finally, four main future research directions of water scarcity assessment are summarized: The further development and improvement of the theoretical framework of 3D water scarcity, applications of the assessment methods on multiple spatial scales, explicit consideration of the impacts of physical and virtual water flow, and mechanism of the evolution of water scarcity. 3D water scarcity is a key to achieving sustainable and harmonious development between humanity and water resources, and its assessment framework can break through the limitations of the traditional one- or two-dimensional models. Water scarcity theory provides methodological support for measuring the state of water resources on global, national, and regional scales, and it will help formulate appropriate water mitigation measures for integrated water resources management.

Virtual water is the amount of water that we ignore in water consumption and is considerably higher than the visible water we see in daily uses. Realizing the water spent in the production processe...

Background Many countries are experiencing significant water scarcity and related problems due to limited availability, uneven distribution of water resources and high demand. Therefore, increasing water use efficiency and better management of existing resources have become substantially important. The agricultural sector is responsible for around 80% of global freshwater withdrawal. Wheat is one of the most important crops having large volumes of virtual water (VW) which is defined as the hidden water embedded in the products. Methods Water footprint (WF) is an indicator showing the total volume of freshwater consumption of a product or process. Blue water concept is defined as the amount of exploited surface and groundwater resources. Green water represents the total volume of rainwater allocated by the product. WF methodology brings a new approach to inter-regional water use and management by quantifying the amount of direct and indirect water use and tracing the hidden links between production, consumption and trade. The main objective of this study is to analyze Turkey’s national blue and green WF of wheat production, consumption and virtual water trade between 2008 and 2019. Detailed province-based quantification of wheat’s water exploitation is provided using spatial interpolation method. Results Total consumptive WF of wheat production and consumption of Turkey is calculated as 39.3 and 48.1 Gm3/year, respectively. The average blue and green VW contents of wheat production through Turkey are assessed to be 1161 and 748 m3/ton, respectively. The water footprint parameters of each province are calculated and discussed using climatic and agricultural data. VW transfer of Turkey’s international wheat trade is also analyzed. Total national water saving is calculated as 7.8 Gm3/year which is mostly imported from Russia. Global VW deficit due to international wheat trade is calculated to be 1.76 Gm3/year. Conclusion Despite its high contribution to global wheat production, increasing population and strong wheat-based diet, quantitative, comparative and up-to-date analyses of the blue and green WF and the VW transfer of wheat production in Turkey are not available. This study contributes to the national and international water management and planning studies to increase the water allocation efficiency of agricultural products.

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

Barley is a major ingredient for the malting industry which is highly sensitive and vulnerable to malt barley supply. The United Kingdom (UK) has the second highest malting capacity in the EU and the third largest malting industry in the world, supplying malt to major global breweries. Premium whisky, which has both economic and cultural significance for the UK, also makes sustainable malt barley supply critical for the UK. There is paucity of information on the sustainability of future supplies of malt barley in the UK, as much as it is in the world. This study applied a food balance approach to assess the combined effects of climate change and mitigation policies on UK malt barley balances for the 2030s, 2040 s, and 2050 s. Future yields of spring barley were simulated under the low, medium and high emissions scenarios (or LES, MES, and HES, respectively) for the three time slices. Future areas of land for barley production were obtained via land use change simulation in response to climate mitigation policies and aspirations of the UK. Future yields and land areas were combined to obtain total barley production, which served as a basis of supply. Per capita malt barley consumption was combined with future population to obtain demand. The gaps between demand and supply were then assessed. The results show large deficits in malt barley supplies for all combinations of climate change, land use and population, with adverse implications for the malting industry. Total malt barley supplies under current land area for barley and using the 90th percentile yield, ranged from 1899 (LES, 2030s) to 2,437 thousand tonnes (HES, 2050s). The largest supply under climate mitigation land use scenarios ranged from 1,592 (LES, 2030s) to 2,120 thousand tonnes (HES, 2050s). Deficits in supply were observed for all climate mitigation land use scenarios and time slices, ranging from 128 to 585 thousand tonnes at 90th percentile yield. However, surpluses were observed from the 2040s if current land area for barley remains unchanged. Imports to balance the observed deficits would result in large inflows of blue water to the UK, with adverse implications for global freshwater supply and environmental sustainability. It is concluded that even though spring barley yields in the UK could increase under projected climate change, reductions in croplands (due mainly to climate mitigation policies and aspirations) could combine with population growth to undermine the sustainability of malt barley supplies, both nationally and internationally.

Hızlı kentleşme, kişi başına düşen su tüketiminin artması ve gelişen endüstriye paralel olarak su kirliliğinin artması, bölgesel su kaynakları üzerinde daha etkili ölçüm, yönetim ve karar mekanizmalarının işleme alınmasını gerekli kılmıştır. Su ayak izi (SA) kavramı, özellikle su kaynakları yönetimine destek sağlamak için ekolojik ve karbon ayak izlerine benzer şekilde son yıllarda literatüre kazandırılan yeni bir parametredir. Herhangi bir alan veya ürünün su ayak izi, üretim süreci boyunca doğrudan veya dolaylı olarak işleme alınan veya kirletilen su kaynaklarının toplam hacmini ifade eder. Bu çalışmanın temel amacı, 2008-2019 yılları arasında Diyarbakır ilinde tarım, hayvancılık, endüstriyel üretim ve evsel kullanımından kaynaklanan mavi ve yeşil su ayak izlerinin detaylı olarak analiz edilmesidir. Buna göre, bölgenin ortalama SA değeri 3,43 milyar m3/yıl olarak hesaplamıştır. İl genelindeki su kaynaklarının büyük çoğunluğunun % 86’lık bir oranla tarımsal ürünlerin yetiştirilmesinde kullanıldığı, mevcut taze suyun % 49’unun yüzey ve yeraltı suyundan tedarik edildiği ve kurak sezonda bu oranın % 62’ye kadar yükseldiği tespit edilmiştir. İlde yetiştirilen tarımsal ürünlerin sanal su muhtevaları ve toplam su kullanımları ayrıca hesaplanmış ve tartışılmıştır. Mevcut çalışma, ülkemizde yapılan ilk bölgesel SA analizlerinden biri olup, tarımsal planlama, evsel ve endüstriyel su tahsisi, atık yönetimi ve su kaynaklarının sürdürülebilirliği gibi konularda katkıda bulunması beklenmektedir.

In recent years, the rapid economic development and population growth of the Beijing–Tianjin–Hebei region has led to a shortage of water resources provided by the natural water cycle. Quantitative expression of the Beijing–Tianjin–Hebei water cycle model is essential for achieving coordinated regional development and solving the problem of water shortages. This study employed a combination of statistical analysis and GIS technology to calculate water demand, virtual water content, blue and green water supply, and water resource demand gap in the Beijing–Tianjin–Hebei region, using data from the Water Resources Bulletin and the China Statistical Yearbook. The water resources structure of the Beijing–Tianjin– Hebei region from both "supply" and "demand" aspects has also been systematically investigated. Water demand was divided into two parts, "real" and "imaginary" components, and discussed as part of the dual water cycle model. The results of this research can provide a theoretical basis for the realization of scientific social water use and ecological environmental water use in the region, as well as the rational development and utilization of water resources.

Grain for Green project (GGP) initialed by China government since 1999 has achieved substantial achievements accompanied with surface runoff decrease in the Loess Plateau but impacts of large-scale afforestation on regional water resources are uncertain. Hence, the objective of this study is to explore the impact of land use change on generalized water resources and ecological water stress using blue and green water concept taking Yanhe River Basin as a case study. Soil and Water Assessment Tool (SWAT) is applied to quantify summary of green and blue water which is defined as generalized water resources, ecological water requirement of vegetation (forest and grass), agricultural water footprint and virtual water flow are considered as regional water requirements. Land use types of 1980 (scenario I), 2017 (scenario II) are input in SWAT model while keeps other parameters constant in order to isolate the influence of land use changes. Results show that average annual difference of blue, green and generalized water resources is −72.08 million m3, 24.34 million m3, −47.74 million m3 respectively when simulation results of scenario II subtracts scenario I and it presents that land use change caused by GGP leads to decrease in blue and generalized water resources whereas increase in green water resources. SURQ in scenario I is more than that in scenario IIin all the study period from 1980-2017, green water storage in scenario I is more than that in scenario II in all the study period except in 1998; whereas LATQ in scenario I is less than that in scenario II except in 2000 and 2015, GWQ in 1992, 2000 and 2015, green water flow in 1998. Blue water, green water storage and green water flow in scenario II is less than that in scenario I in the whole basin, 12.89 percent of the basin and 99.21 percent of the basin respectively. Total WF increases from 1995 to 2010 because forest WF increases significantly in this period though agricultural WF and grass WF decreases. Ecological water stress index has no obvious temporal change trend in both land use scenarios but ecological water stress index in scenario II is more than that in scenario I which illustrates that GGP leads to increase of ecological water stress from perspective of generalized water resources

Water scarcity is an emerging threat to food security and socioeconomic prosperity, and it is crucial to assess the response of crop production to water scarcity in large river basins. The water footprint, which takes into account water use in supply chains, provides a powerful tool for assessing the contributions of water resources within a certain region, by tracking the volume and structure of virtual water flows. In this study of the structure of the water footprint network from a complexity perspective, we reassessed the significance of water resources for crop services in a large river basin with a severe water shortage -the Yellow River Basin (YRB) of China. The temporal increase of the complexity index indicated that the Virtual Water out-Flows (VWF) from the YRB were becoming increasingly critical to China; i.e., the ability of YRB to produce crops boosted difficulty of its water being replaced by water exporting from other basins. Decomposition of complexity suggested that during the 1980s to 2000s, the temporally increased complexity was due mainly to the paucity of competitors and the increasing uniqueness of crops supporting VWF. This complexity deeply embedded the YRB into the footprints of a water network that facilitated further development with constrained water resources, but it also reinforced reliance from other regions on YRB’s scarce water. Based on this analysis, we therefore suggest that resource regulation should be carried out at an appropriate time to ensure both the ecological sustainability and high-quality development of river basins.

This dissertation presents three studies on California’s water footprint, which is defined as the amount of water required to produce everyday goods and services demanded by California consumers on a yearly basis. Such a consumption-based indicator of water use is novel, and I introduce water footprint science as an expanded reading of water that adds value to conventional approaches to understanding society’s relationship with water resources. California, as a water-limited state, presents a useful case study for examining how demands on water resources have shifted within and outside of the region through its water footprint. The Introduction section discusses the history of water use in California from a conventional perspective as well as what water footprint assessment, as an evolving science, might offer in terms of an expanded reading of water for sustainability decision making. The first study (Chapter 2) shows that scaling water footprint assessment to the state level both illuminates California’s unique arrangement with respect to internal and external water resources and provides a basis for policy consideration at a relevant decision-making level. The second study (Chapter 3) focuses on the water footprint of California’s energy system in order to show how environmental policymaking, particularly climate mitigation policies in the energy sector, can result in maladaptation with respect to water systems and that water footprint assessment provides a useful tool for avoiding redistribution of water impacts. The third study (Chapter 4) presents a time-series of California’s overall water footprint, indicating an externalization of water footprint demands in recent decades and a decreasing of dependence on internal water resources for instate consumption of everyday goods.The Conclusion section reflects on what water footprint assessment has thus far provided in terms of an expanded reading of water for California, and how that information might support sustainability decision making in various facets of governance. I identify shortcomings of the method and ways in which improvements can be made in the future, particularly through interdisciplinary research. Water footprint information offers important insights into California’s recent development as well as tools for developing future sustainable transitions.

The building sector is one of the major consumers of water resources, according to the United Nations Environmental Program, buildings and their associated industry consume 30% of the fresh water available worldwide. Optimizing this resource usage is a key factor and makes it necessary to analyze it with environmental and economic indicators, so that the magnitude of the impact can be qualified and quantified, and covering all the building life cycle. The analysis includes the first stage, the project conception, follows with the assessment of raw materials and its manufacture, continues with the use and maintenance, and finalizes with the demolition of the building. The water consumed in all those processes or Virtual Water (VW) can be the key to the reduction of the built environment impact. Because the total water consumption of a building includes not only the water that has been required off-site to manufacture the materials used, as well as the water embodied in the production of energy, also the direct water used in the building needs to be studied. This together can be considered the building water footprint (WF). A methodology based on the quantity surveying of the building project which includes materials and machinery is used for the inventory. The WF quantification is treated similarly to a project budget. A case study of a residential building in Huelva, Spain is evaluated. The most impacting stage is the use followed by the construction, being other stages less significant.

In Tarim River Basin (TRB), the retreat of glacier and snow cover reduction due to climate warming threatens the regional economy of downstream basins that critically depends on meltwater. However, the quantitative evaluation of its impact on multiple sectors of the socioeconomic system is incomplete. Based on compiled regional input–output table of the year 2012, this study developed a method to analyze the relationships between economic activities and related meltwater withdrawal, as well as sectoral transfer. The results show that the direct meltwater withdrawal intensity (DMWI) of agriculture was much higher than other sectors, reaching 2348.02 m3/10,000 CNY. Except for A01 (agriculture) and A02 (mining and washing of coal), the embodied meltwater withdrawal (EMW) driven by the final demand of other sectors was greater than direct meltwater withdrawal, and all sectors required inflows of virtual water (72.45 × 108 m3, accounting for 29% of total supply from cryospheric water resources) for their production processes in 2012. For sectors with high DMWI, improving water-use efficiency is an effective way to reduce water withdrawal. To some extent, the unbalanced supply of cryospheric water resources due to geographical segregation can be regulated by virtual water flows from water-saving to water-intensive sectors. Such decisions can affect the balance between socioeconomic development and environment conservation for long-term sustainability.

Agriculture is the largest fresh water consuming sector, and maize is the most produced and consumed crop worldwide. The water footprint (WF) methodology quantifies and evaluates the water volumes consumed and polluted by a given crop, as well as its impacts. In this work, we quantified for the first time the green WF (soil water from precipitation that is evapotranspired) and the green virtual water exports of maize from Buenos Aires province, Argentina, during 2016–2017, due to the relevance of this region in the world maize trade. Furthermore, at local level, we quantified the green, blue (evapotranspired irrigation), and grey (volume of water needed to assimilate a pollution load) WF of maize in a pilot basin. The green WF of maize in the province of Buenos Aires ranged between 170 and 730 m3 /ton, with the highest values in the south following a pattern of yields. The contribution of this province in terms of green virtual water to the international maize trade reached 2213 hm3 /year, allowing some water-scarce nations to ensure water and water-dependent food security and avoid further environmental impacts related to water. At the Napaleofú basin scale, the total WF of rainfed maize was 358 m3 /ton (89% green and 11% grey) and 388 m3 /ton (58% green, 25% blue, and 17% grey) for the irrigated crop, showing that there is not only a green WF behind the exported maize, but also a Nitrogen-related grey WF. This research has been carried out with the support of the National Agency for Scientific and Technological Promotion of Argentina (PICT 2017-0564). The participation of M.M. Arrien was possible through a grant from the Scientific Research Commission of the Province of Buenos Aires (CICPBA), Argentina. The project leading to these results has also received funding from 'la Caixa' and Caja Navarra Foundation, under agreement LCF/PR/PR13/51080004.

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

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

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

This article investigates the energy intensity and related impacts of the Eastern Route of China's South-North Water Transfer Project, based on the concept of the water–energy nexus. It finds that from November 2013 to May 2017 a total of 2.35 billion kWh of energy was consumed to transfer 15.5 billion m3 water driven by a large-scale system of pumping stations. This energy production required 7.4 million m3 of virtual water and emitted 1.93 MtCO2e of carbon. An average water–energy nexus ratio of 0.05% indicates that transferring 100 m3 of water consumes 0.05 m3 of virtual water due to the electricity consumption of the Eastern Route's pumping stations. It is estimated that to transfer 7.3 billion m3 water by 2030, this mega project will consume 1.35 billion kWh of energy, 4.6 million m3 of virtual water and emit 0.94 MtCO2e of carbon. These findings and scenario analysis demonstrate that strategies are needed for mitigating the energy intensity of the Eastern Route, such as improved pumping efficiency, reduced water loss during water delivery, decreased water quotas, and promotion of other, less carbon-intensive water sources in destination provinces.

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

Agriculture is the sector with the largest water usage globally, as well as within China. Water is a limited resource that represents the base for regional food security. Modern water science has revealed that crop production consumes not only so-called blue water (surface and ground water), which is at the core of current agricultural water policies, but also so-called green water (rainwater). As driven by natural-socio-economic (“ternary”) activities, water related to the crop production chain (i.e. pre-, during- and after-production) flows in coupled physical and virtual (the “two-dimension”) forms through physical water consumption, virtual water embedding and inter-regional virtual water flows. In this work, based on a physical-virtual water flow theory framework, we have developed a quantification approach for regional crop-related physical-virtual water flow processes, with a focus on the water quantity. This quantification integrates green and blue water footprint accounting and virtual water flow network simulations. We applied this approach in a case study for six western provinces along the “Silk Road Economic Belt” in China over the period 1985−2013. Ten major crops were considered in the case study. Our results show significant crop-related physical-virtual water flows among the six provinces. In terms of blue water, 49% of the irrigation water supply was consumed in the crop production we considered, 31% of which was converted to virtual water flows. Moreover, we find that a trade-off exists between water use efficiency and associated economic value along the physical-virtual water flows. For example, Xinjiang has suffered water stress due to crop production, with a net virtual water export of 21×109 m3/a, but has a high economic income of 314 million CNY/a as a result of the water flow. This study highlights the importance and necessity of improving traditional agricultural water management, which focuses on reducing blue water consumption through engineering strategies, by integrating physical-virtual water flow assessments in order to achieve both high resources and economic efficiencies in water use, as well as both green and blue water savings. Specifically, we propose three key steps towards attaining this goal: (1) To consider both the physical and virtual water flows in modern agriculture water saving technologies as well as policies; (2) to invest in and enhance academic capabilities for quantifying, analysing and optimizing agricultural physical-virtual water flows; (3) to build a modern agricultural water management system targeted towards healthy and sustainable physical-virtual water flows in order to finally achieve both water sustainability and food security goals.

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.

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

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

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

‘Virtual water’ represents water resources consumed by industrial, agricultural, and other human activities. Virtual water flow is significant for coordinating the global water balance, but most current research has focused on land. In this study, marine products or services are introduced into the research framework of virtual water, and the concept of ‘marine equivalent virtual water’ is introduced. The formulas are proposed from three aspects: food, environment, and power generation. The calculation results for China's marine equivalent virtual water content from 2006 to 2015 show a U-shaped characteristic in which different factors change in importance over time. In addition, the marine equivalent virtual water system structure is analyzed and forecasted for China's coastal areas by 2025. Through the changes in the marine equivalent virtual water system entropy, the research area is divided into three development types: equilibrium, orderly, and change. Each area can be targeted to put forward development proposals. The marine equivalent virtual water proposition quantifies the function of the ocean in the supply of freshwater resources. It provides a new perspective for relieving pressure on terrestrial water resources and is of great significance to water resource management and water policy formulation; this concept should be built upon in future research.

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

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

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.

The article is devoted to the study and substantiation of the theoretical and methodological foundationsfor assessing the consumption of virtual water taking into account the features of organic productionusing the water trace tool, which allows you to make the right management decisions on the rational useof water resources in the agricultural sector, particularly in organic agricultural production.Water should be a tool that makes it possible to comprehensively assess the attitude of the consumer orproducer to the use of freshwater systems: it is a comprehensive indicator of assessing the volume of waterconsumption and the level of pollution of water resources for all quality components; It is not an indicatorof local environmental impact, water consumption and water pollution, since this impact depends onthe vulnerability of the local water system and the amount of water used by consumers and pollutants ofthe freshwater system. The water footprint tool provides accurate information on how water is used forvarious purposes; is the basis for drawing conclusions about the sustainable and reasonable use of waterresources and their distribution, as well as the basis for assessing the environmental, social and economicimpacts at the regional level.Based on an adapted methodology, an assessment of the water footprint of organic farming in Ukrainehas been carried out. In most regions characterized by low water availability, this indicator is high due tothe growing of crops with significant water consumption. In general, the implementation of the proposedmethodology will ensure food, environmental safety of the object of study and increase the competitivenessof the industry.