The effect of inter-annual variability of consumption, production, trade and climate on crop-related green and blue water footprints and inter-regional virtual water trade: A study for China (1978-2008)

Ecological impact assessment of green virtual water flow in inter-provincial crop commutation within China

Green water is crucial for to regional ecological sustainability. Currently, there is a lack of research on the impact of crop green water communication on the regional ecology in China. The ecological impact index (EII) and integrated ecological water supply (IES) were proposed to comprehensively evaluate the regional ecological impact of the green virtual water flow (GVWF) of crops. Based on the principle of trade cost minimization, this study simulated the inter-provincial crop commutation within China during 2010-2019 by assigning weights to production, demand, and transportation costs, and analyzed the impact of crop communication on regional ecology. The results showed that multi-year average GVWF among provinces was 216.45 Gm3, accounting for 33.7 % of the total green water footprint of crops. The ecological impact of GVWF varies among provinces and years. The EII values in Beijing, Shanghai, and Jiangsu were all >100, whereas it was <1 in Yunnan and Xizang. Regional management policies for water resources, ecology, and economic development should be formulated taking into account the IES and EII jointly. It is recommended to increase the export of green virtual water of crops and expand the ecological area while ensuring the utilization rate of green water in regions with higher EII values, such as Guangxi and Yunnan. In the future, it is important for district managers to prioritize the quality of ecological development and protect ecological areas from erosion while pursuing urban development. This study innovatively evaluated the ecological impact of crop communication in different regions, which has guiding significance for the trade management in the ecologically water-deficient areas.

Water footprint of irrigated rice in the state of Rio Grande do Sul, 2019/2020 crop

Agricultural production is the practice that uses the most water on the planet, especially the irrigated agriculture, which represents a large part of this demand. As well as the quantitative issue, adequate quality is essential to meet the demands of the crop and its return to the water sources, in a way that does not cause damage to the environment. To measure this consumption, the expression "water footprint" emerged. The water footprint seeks to quantify the demand for water incorporated into products. This paper aims to determine the amount of water used to produce irrigated rice in six rice growing regions in the state of Rio Grande do Sul (RS), in the 2019/2020 crop. The mentioned regions are represented the municipalities of Uruguaiana (West Border), Dom Pedrito (Campanha), Santa Maria (Central Region), Camaquã (Internal Coastal Plain), Porto Alegre (External Coastal Plain), and Rio Grande (South Zone). Climate data from the analyzed regions, during the plant cycle, and productivity values in the crop in question were used. Values of 1187 m3 t-1 were found for WB, 1347 m3 t-1 for CA, 1058 m3 t-1 for CR, 783 m3 t-1 for ICP, 1115 m3 t-1 for ECP, and 1066 m3 t-1 for SZ. For the state of Rio Grande do Sul, an average water footprint was obtained in the 2019/2020 crop of 1093 m3 t-1.

Patterned Hybrid Wettability Surfaces for Fog Harvesting

The scarcity of fresh water resources has become increasingly serious in recent years, posing threats to the survival of mankind. The ability of the animals and plants in arid areas to collect water from moisture and fog has drawn attention worldwide. Inspired by the synergistic fog harvesting mode of natural organisms with superhydrophilic and superhydrophobic patterning, a composite membrane with a concave-convex morphology and hybrid wettability was prepared aiming at efficient fog harvesting. The hybrid wettability surface was obtained by chemically modifying the superhydrophilic PAN substrate with 1H,1H,2H,2H-perfluorooctyltrichlorosilane using iron mesh as the mask. The porous PAN substrate was prepared by the non-solvent-induced phase separation (NIPS) method. Fog harvesting is a three-step process: condensation, coalescence, and rapid transportation of water droplets. The area and ratio of the hydrophilic/hydrophobic regions were tuned by adjusting the mesh number of the iron meshes. Under the optimal condition, the fog harvesting efficiencies of 40.3 and 74.2 mg·cm^-2·min^-1 were obtained when the fog yields were 0.05 and 0.1 L·min^-1, respectively. The present work provides an alternative strategy for addressing the shortage of fresh water resources.

Environmental, Human and Ecotoxicological Impacts of Different Rice Cultivation Systems in Northern Thailand

Sustainable practices in rice cultivation require effective farming management concerning environmental and human health impacts. In this study, three rice cultivation systems, namely low-land, upland, and terraced rice in the Mae Chaem District, Chiang Mai Province, were assessed and the carbon footprint (CF), water footprint (WF), and human and ecotoxicological impacts were compared from pesticide application. The results showed that the highest CF intensity was observed in terraced rice with 1.15 kg CO₂eq kg^-1 rice yield, followed by lowland rice (1.02 kg CO₂eq kg^-1 rice yield) and upland rice (0.17 kg CO₂eq kg^-1 rice yield) fields. Moreover, lowland rice cultivation generated the highest total WF with 1701.6 m³ ton^-1, followed by terraced rice (1422.1 m³ ton^-1) and upland rice (1283.2 m³ ton^-1). The lowland rice fields had the most impact on human health and freshwater ecotoxicity, followed by the terraced and upland rice cultivation systems. The results also showed that most of the pesticides remaining in soils were chlorpyrifos (98.88%), butachlor (96.94%), and fipronil (95.33%), respectively. The substances with the greatest distributions in freshwater were acephate (56.74%), glyphosate (50.90%), and metaldehyde (45.65%), respectively. This study indicated that, with more agricultural inputs, higher CF, WF, human health impacts, and freshwater ecotoxicity were generated. Although the use of pesticides in the study areas did not exceed the recommendations on the packaging, glyphosate and chlorpyrifos are restricted in Thailand, so it is necessary to monitor their use due to their long-term health effects.

Water footprint of nations amplified by scarcity in the Belt and Road Initiative

The growing water scarcity due to international trade poses a serious threat to global sustainability. Given the intensified international trade throughout the Belt and Road Initiative (BRI), this paper tracks the virtual water trade and water footprint of BRI countries in 2005-2015. By conducting a multi-model assessment, we observe a substantial increase in BRI's water footprint after taking water scarcity into account. Globally the BRI acts as a net exporter of virtual water, while the export volume experiences a decreasing trend. Noticeable transitions in nations' role (net exporters vs. net importers) are found between the BRI and global scales, but also between with and without considering water scarcity. Overall economic and population growth is major drivers of scarcity-weighted water footprint for BRI nations, as opposed to the promotion of water-use efficiency and production structure that can reduce water scarcity. Improving international trade and strengthening cooperation on water resources management deserve priority in alleviating the water scarcity of BRI.

Limited water scarcity mitigation by expanded interbasin physical and virtual water diversions with uneven economic value added in China

Interbasin water diversion projects and virtual water transfers embedded in exchanged goods and services are two effective solutions to water deficits. However, the associated real responses in water quantity and quality scarcities and the economic efficiencies remain unclear. Here, we tracked the blue water scarcities, water pollution levels, and economic value added through interbasin physical and virtual water diversions across nine river basins by sector in China from 2007 to 2015. The total national blue and grey water footprints were 365 Gm³yr^-1 and 592 Gm³ yr^-1, in which the Yangtze River basin accounts the most for 32 % and 37 %, respectively, by 2015. The physical water diversions increased by 52 % to 16.9 Gm³yr^-1. The blue virtual water transfers increased by 24 % to 176 Gm³yr^-1, whereas the grey virtual water transfers decreased by 10 % to 266 Gm³yr^-1. Agriculture related interbasin virtual water flows showed opposite directions to those driven by the industry sector. Although with uneven value added while growing, limited effects mitigated water quantity and quality stresses, especially in the drier Yellow, Northwest, and Hai River basins where the capital is located. Half of the basins had low and declining synergy scores, suggesting an urgent need to achieve synergies between resources, the environment, and the economy across basins.

Patterns and driving forces of the agricultural water footprint of Chinese cities

The patterns and determinants of different types of agricultural water footprints in China are poorly understood at the prefecture-city level. In this paper, we evaluate Chinese agricultural water footprints from 2000 to 2017 and analyzed their spatio-temporal characteristics. Our estimation results show that the annual average agricultural water footprint in China was 5.038 × 10⁹ m³, and the proportions of green water, blue water, and gray water were 70%, 9%, and 21%, respectively. In addition, high agricultural water-footprint cities with obvious urban agglomeration effects are mainly located in the Northeast, the Huanghuai River, the Yangtze River Basin, and Northwestern of Xinjiang, while low agricultural water-footprint cities are concentrated in high coastal urbanization-level areas or less developed agricultural areas of the west. We also investigate their determinants using a spatio-temporal fixed-effect model and find that GDP per capita, total investment in fixed assets, the income level of rural residents, the proportion of food grown, spray and drip irrigation technology, low-pressure pipe irrigation technology and seepage control irrigation technology have significant positive impacts on the agricultural water footprint. In contrast, the proportion of secondary and tertiary industries, social retail consumption, urbanization, technology expenditure, and the effective irrigation area proportion have a significant inhibitory effect. The primary determinants of the agricultural water footprint also vary substantially across water footprint categories (green, blue, and gray water footprints) and regions. Our findings imply that the agricultural water footprint should be incorporated into city water resource management and monitoring system.

Dynamic simulation of industrial synergy optimisation pathways in Beijing-Tianjin-Hebei region driven by water environment improvements

China is promoting the coordinated development of the Beijing-Tianjin-Hebei region as a national strategy project; however, water scarcity and water quality problems will become a bottleneck restricting high-quality development. This study aimed to explore a feasible industrial synergy optimisation pathway to realise the collaborative development of economic growth and water environment improvement, combined with incentives for environmental efficiency improvement and reclaimed water utilisation. Research methods integrate input-output modelling, system dynamics, and multi-objective programming to construct a complex multi-region model. A dynamic simulation measure was adopted to simulate the economic and environmental impacts of different approaches that mix from 2020 to 2030 under water resource environment constraints. According to the simulation results, the annual economic growth rate of the entire region can exceed 6.1%, and the emission intensities of water pollutants decrease by more than 60.0%. In addition, traditional manufacturing industries that achieve cross-regional synergy can still release location advantages without negative environmental impacts. Furthermore, regional collaborative development optimises the allocation of water resources and alleviates water stress. Moreover, the pollutant emission reduction effect of source control in Hebei was more effective than in other cities. Finally, reclaimed water, as the end treatment measure, has the largest marginal effect on improving the trade-off between economic and environmental improvement in the long run. This study provides a new approach for multi-regional industrial synergy development and optimal allocation of resources and contributes to the high-quality development of the watershed.

Global spatio-temporal change assessment in interregional water stress footprint in China by a high resolution MRIO model

Developing effective strategies to alleviate increasing water stress in China requires an understanding of how consumption and production drive water stress footprints (WSF) at a high resolution and multiple spatial and temporal scales. However, current Chinese multi-regional input-output (CMRIO) models have limited resolution. Here, we build a high-resolution international MRIO model covering 31 Chinese provinces, 163 sectors, to address this issue, and then analyze the impact of changes in China's interprovincial and international trade patterns on the WSF from 2012 to 2017. We find that China's water stress embodied in inter-provincial trade has increased year after year, to 5606 km³ H₂O-eq in 2017, exceeding 50 % of the total domestic footprint. Domestic water stress transfer is most apparent in the outsourcing of water stress from eastern coastal regions to Central and Western regions, with the top interregional supply chain paths mainly associated with the demand of processed rice and tobacco products. China has transformed into a net exporter of water stress in 2017, with water stress exports to developing countries accounting for 54 % of total exports, up from 51 % in 2012. With deepening globalization, trade between China and developing countries has boosted bilateral economic development, while also exacerbating water stress in China. In addition to agricultural cultivation, industrial products such as plastics and steel exported to meet international industries further contribute to water stress in Northern China. Further identify hotspots of water stress consumption is needed to prioritize actions to relieve regional water stress in a more effective manner, and our study can provide key information.

Inputs for staple crop production in China drive burden shifting of water and carbon footprints transgressing part of provincial planetary boundaries

Crop production is the biggest water user and key contributor to anthropogenic greenhouse gas emissions. Increasing crop yields to ensure adequate food supply under water and land scarcity is excessively dependents on intensive agricultural inputs (such as fertilizers, pesticides, agri-films, or energy), resulting in unintended environmental consequences. Supply chains bringing environmental-intensive inputs from their place of production to the croplands. However, most food-related environmental assessments ignore the environmental burden of agricultural input production, trade, and consumption. Here, we estimate spatially-detailed water (WF) and carbon footprints (CF) of wheat, maize, and rice production in China with extended system boundary from upstream raw material mining to the field. The agricultural inputs account for up to 24% and 89% of a crop's WF and CF, respectively, at the provincial level. The total local generated WF in Chinese northern provinces and CF in Shanxi and Inner Mongolia provinces for producing crops and agricultural inputs transgresses the corresponding downscaled blue water and carbon planetary boundaries. The study broadens the scope of traditional environmental impact assessments in agricultural production and sheds light on the significances to manage the linkages between the crop production and the agricultural inputs' upstream supply chains towards more efficient water use and less greenhouse gas emissions in food system.

Winter Potato Water Footprint Response to Climate Change in Egypt

The limited amount of freshwater is the most important challenge facing Egypt due to increasing population and climate change. The objective of this study was to investigate how climatic change affects the winter potato water footprint at the Nile Delta covering 10 governorates from 1990 to 2016. Winter potato evapotranspiration (ETC) was calculated based on daily climate variables of minimum temperature, maximum temperature, wind speed and relative humidity during the growing season (October–February). The Mann–Kendall test was applied to determine the trend of climatic variables, crop evapotranspiration and water footprint. The results showed that the highest precipitation values were registered in the northwest governorates (Alexandria followed by Kafr El-Sheikh). The potato water footprint decreased from 170 m3 ton−1 in 1990 to 120 m3 ton−1 in 2016. The blue-water footprint contributed more than 75% of the total; the remainder came from the green-water footprint. The findings from this research can help government and policy makers better understand the impact of climate change on potato crop yield and to enhance sustainable water management in Egypt’s major crop-producing regions to alleviate water scarcity.

Climate change impact on major crop yield and water footprint under CMIP6 climate projections in repeated drought and flood areas in Thailand

Understanding crop yield and water requirements in response to the future climate at the local scale is essential to develop more precise and appropriate adaptation strategies. From this perspective, repeated drought and flood events in the lower north of Thailand were investigated. The objectives of the study were to evaluate the impact of climate change on major crop yields and the water footprint (WF). Five global circulation model datasets from the sixth phase of the Coupled Model Intercomparison Project (CMIP6), known as Shared Socioeconomic Pathways (SSPs), were selected. Three future periods: near (2015-2039), mid (2040-2069), and far future (2070-2100) under SSP245 and SSP585 scenarios were used to predict the major crop yields and WF changes in the future. The precipitation and maximum and minimum temperatures were projected to increase in all periods under both scenarios. Rice yields in irrigated areas were predicted to rise gradually over the three projection periods under SSP245 but decline in mid and far-future periods under SSP585. There was a predicted reduction of first and second rice crop yields by -6.0% to -17.7% under SSP585. Fortunately, those rice yields were expected to increase in the near-future period under SSP245 by 3.0% to 4.3%. Growing maize, soybean, or mung bean instead of a second rice crop will have a less negative impact on future climate change. Changing from growing rice to be planting maize twice per year and growing cassava had increased favorability in rain-fed areas. The WF changes in the future were associated with future crop yield changes; therefore, the decrease in WFs was due to an increase in crop yield and vice-versa. The total WFs of maize, soybean, mung bean, and cassava production were roughly half that of rice production, indicating that these crops are suitable alternatives in the dry season.

Blue, green, and grey water footprints assessment for paddy irrigation-drainage system

Water footprint (WF) quantifies the impact of paddy field evapotranspiration (ET) and non-point source pollution on water resources and is an evaluation index for water sustainability. However, it is difficult to measure accurately using the existing method, which is based on parameter assumption without considering the field water conditions. In this study, a generic and physically based method for blue, green, and grey water accounting in paddy rice cultivation is introduced. We conducted field experiments using the common flood irrigation (CFI) and water-saving irrigation (SWI) modes in Nanjing, East China. By tracing the sources of ET and the migration process of multiple pollutants (TN, TP, NH₄⁺-N, and NO₃^--N), the characteristics of blue-green water consumption and the actual amount of water required to dilute pollutants at different growth stages of rice under CFI and SWI were analyzed. The WF of paddy rice was 1000 m³/t (49% WF_green, 17% WF_blue, 34% WF_grey) and 910 m³/t (50% WF_green, 10% WF_blue, 40% WF_grey) for CFI and SWI, respectively. The WF for paddy rice production was reduced by approximately 9% under SWI compared to CFI, with declines of 47% for WF_blue and 8% for WF_green. The SWI mode changed the ratio of blue to green water fluxes in field water by reducing irrigation during non-critical periods, and green water was used preferentially to enhance its utility. This conceptual method is the first to describe the formation mechanism of blue, green, and grey WFs in paddy systems. It can be extended to different scales and agro-ecosystems that show the influence of crop cultivation on water resources.

Assessment of the regional agricultural water-land Nexus in China: A green-blue water perspective

An appropriate agricultural water-land nexus can help to effectively take advantage of limited water and land resources, which is of great significance for guaranteeing food security. An R index was proposed to evaluate the regional agricultural water-land nexus from a green-blue water perspective in the current paper. The effects of irrigation on the agricultural water-land nexus were revealed for the first time based on this index in evaluations of all (R_t) and irrigated (R_i) arable land in the 31 provinces, autonomous regions and municipalities (PAMs) of China during 1999-2018. The national annual average values of R_t and R_i were 1.94 and 3.55 m³/m², respectively; the former was steady during the observed period, while the latter showed a significant decreasing trend (P < 0.01) from 4.35 m³/m² in 1999 to 2.66 m³/m² in 2018. The values of both R_t and R_i values in South China were higher than those in North China. The maximum values of R_t and R_i appeared in Xizang (R_t = 99.15 m³/m²; R_i = 201.99 m³/m²), while the minimum values occurred in Ningxia (R_t = 0.30 m³/m²; R_i = 0.44 m³/m²). The Gini coefficient for R_i (G_i) in each year was higher than that for R_t (G_t), demonstrating that the agricultural water-land nexus in irrigated arable land was highly imbalanced during the last two decades. From the perspective of the equitable distribution of irrigation water, irrigation facilities should be developed in the Southeast and Southwest PAMs to improve the effective irrigation rate. In addition, the government should simultaneously implement water transfer plans to reduce the agricultural water pressure in the PAMs in the North China Plain and Northeast China.

Spatiotemporal variations of agricultural water footprint and its economic benefits in Xinjiang, northwestern China

Agriculture is the largest water user and is the main driving force behind water stress in Xinjiang, northwestern China. In this study, the water footprint (WF) (blue, green and gray WF) of main crop production and their temporal and spatial characteristics in Xinjiang were estimated in 2006, 2010, 2014 and 2018. The blue water footprint deficit (BWF_d) was conducted and food productivity and economic benefits of WF were also analyzed via the water consumption per output value (food productivity and economic benefits). The results reveal that the WF increased from 22.75 to 44.16 billion m³ during 2006–2018 in Xinjiang, of which cotton, corn and wheat are main contributors of WF. In terms of different regions, corn has the largest WF in north Xinjiang and cotton has the largest WF in south and east Xinjiang. The BWF_d broadened from − 11.51 to + 13.26 billion m³ in Xinjiang with the largest increased BWF_d in Kashgar (from − 3.35 to 1.40 billion m³) and Aksu (from − 2.92 to 2.23 billion m³) of south Xinjiang and in Shihezi (from − 0.11 to 2.90 billion m³) of north Xinjiang. In addition, the water footprint food productivity does not well correspond with the water footprint economic benefits in prefectures of Xinjiang. It means we should consider the food yields priority and economic benefits priority to formulate a scientific and effective supervisor mode to realize the sustainable management of agricultural water in prefectures of Xinjiang.

Modelling the effect of changing transplanting date on consumptive water footprints for paddy under the system of rice intensification

BACKGROUND

Consumptive water footprint (CWF) is a comprehensive measure of water consumption by paddy and can be used to assess the impact on freshwater volume. The seasonal water consumption and water footprints of paddy under any irrigation practice vary with changing the transplanting dates. The present study aimed to investigate the impact of shifting transplanting dates on CWFs of paddy under the system of rice intensification (SRI) using a crop model. A medium-duration variety (IR-36) was cultivated during kharif (monsoon) and rabi (non-monsoon) seasons of 2015/16 and 2016/17. The field data were used to calibrate and validate the crop model, Agricultural Production Systems Simulator (APSIM)-Oryza, as well as simulate paddy yield, evapotranspiration and consumptive water footprints (CWFs) under different transplanting dates.

RESULTS

The APSIM-Oryza simulated grain yield was found to be closely matched with the observed yield during both calibration (r²  = 0.98, root-mean-square error < 300 kg ha^-1 ) and validation (r²  = 0.88, root-mean-square error < 400 kg ha^-1 ). The seasonal water savings in SRI practice was 18-21% compared to conventional, with an effect of a 20-30% improvement in the yield. The early transplanting on 1 July in kharif and 15 December in rabi can produce maximum grain yields of 4.55 and 5.15 t ha^-1 , respectively, with a minimum CWF of 1064 and 855 m³ t^-1 under SRI for the study region.

CONCLUSION

The comparison of yield and CWF scenarios under different transplanting dates revealed the superiority of early transplanting in terms of yield improvement with the least irrigation requirement and CWF under SRI. © 2021 Society of Chemical Industry.

Mapping spatial supply chain paths for embodied water flows driven by food demand in China

Identifying critical spatial supply chain paths for embodied water flows driven by food demand can guide the development of more spatially explicit food-related policies for water savings. Previous studies have quantified water uses caused by food demand, but overlook intermediate transfer paths within and among regions. That is, spatial supply chain paths describing step-by-step transfer stages between water uses and final food demand have not been well characterized. Based on the multi-regional input-output model and structural path analysis, this study exhaustively identifies critical spatial supply chain paths for provincial water withdrawals driven by final food demand in China. Results show that the final demand of food products from critical sectors (e.g., agricultural products processing, rice, and swine) and regions (e.g., Xinjiang, Heilongjiang, and Guangdong) drives large amounts of water withdrawals. Critical supply chain paths indicate that agricultural products processing, food manufacturing, and catering should pay special attention to increasing the use efficiency of rice, poultry, cotton, water, and gas products, which can effectively reduce national water withdrawals. The interregional paths further provide evidence for interregional cooperation to save food-related water resources, such as the transfer of capital and technologies from agricultural products processing in Shandong to cotton production in Xinjiang and rice production in Heilongjiang. These critical supply chain paths provide spatially explicit and targeted hotspots for demand-side policies. They can also serve for the evaluation of measures in each stage of the supply chain paths.

What the reclaimed water use can change: From a perspective of inter-provincial virtual water network

Reclaimed water has been used as an alternative water resource for various economic activities, which inevitably is involved in the virtual water trade. However, the effect of reclaimed water on the virtual water trade has not been evaluated in previous studies. For the sake of sustainable water management, this study explored the benefits of reclaimed water use for balancing the water resource allocation at the interprovincial level. Multiregional input-output analysis and ecological network analysis were used to investigate the spatial and structural characteristics of the virtual reclaimed water network (VRWN) among 31 provinces in China and the potential effect of reclaimed water use. The results show that the net export flows of virtual reclaimed water have different spatial patterns from those of freshwater, some provinces that import virtual freshwater are exporters of virtual reclaimed water. Although the exploitative relationship is the dominant ecological relationship in the VRWN (72%), it is confirmed that reclaimed water use contributes to balancing the virtual water trade of China with a more competitive relationship (21%) than in the virtual freshwater network (4%). The virtual freshwater consumption change rate in developed provinces decreases by more than 10% through reclaimed water use. Due to the high food exports and low application of wastewater reclamation in less developed provinces, the effect of reclaimed water use in those provinces is not as obvious as that in developed provinces. This paper offers a new perspective for understanding the current VRWN and guidance for the optimization of the virtual water trade structure.

Quantifying economic-social-environmental trade-offs and synergies of water-supply constraints: An application to the capital region of China

Sustainable water management is one of the sustainable development goals (SDGs) and is characterized by a high level of interdependencies with other SDGs from regional to global scales. Many water assessment studies are restricted to silo thinking, mostly focusing on water-related consequences, while lacking a quantification of trade-offs and synergies of economic, social, and environmental dimensions. To fill this knowledge gap, we propose a "nexus" approach that integrates a water supply constrained multi-regional input-output (mixed MRIO) model, scenario analysis, and multi-criteria decision analysis (MCDA) to quantify the trade-offs and synergies at the sectoral level for the capital region of China, i.e. the Beijing-Tianjin-Hebei urban agglomeration. A total of 120 industrial transition scenarios including nine major industries with high water-intensities and water consumption under current development pathways were developed to facilitate the trade-off and synergy analysis between economic loss, social goals (here, the number of jobs) and environmental protection (with grey water footprint representing water pollution) triggered by water conservation measures. Our simulation results show that an imposition of a tolerable water constraint (a necessary water consumption reduction for regional water stress level to move from severe to moderate) in the region would result in an average economic loss of 68.4 (± 16.0) billion Yuan (1 yuan ≈ 0.158 USD$ in 2012), or 1.3 % of regional GDP, a loss of 1.94 (± 0.18) million jobs (i.e. 3.5 % of the work force) and a reduction of 1.27 (± 0.40) billion m³ or about 2.2% of the regional grey water footprint. A tolerable water rationing in water-intensive sectors such as Agriculture, Food and tobacco processing, Electricity and heating power production and Chemicals would result in the lowest economic and job losses and the largest environmental benefits. Based on MCDA, we selected the 10 best scenarios with regard to their economic, social and environmental performances as references for guiding future water management and suggested industrial transition policies. This integrated approach could be a powerful policy support tool for 1) assessing trade-offs and synergies among multiple criteria and across multiple region-sectors under resource constraints; 2) quantifying the short-term supply-chain effects of different containment measures, and 3) facilitating more insightful evaluation of SDGs at the regional level so as to determine priorities for local governments and practitioners to achieve SDGs.

Blue water footprint linked to national consumption and international trade is unsustainable

Increasing pressure on the world's freshwater resources raises serious concerns about global food security and the sustainability of water use in agriculture. Here we quantify and map at a 5-arcmin spatial resolution the blue water footprint of each country's national consumption and where they infringe sustainable environmental flows as defined by the presumptive environmental flow standard or the 80% rule, in which runoff depletion by more than 20% will pose risk to ecosystems. We find that 52% of the blue water footprint of global consumption and 43% of international blue virtual water flows come from places where the sustainable environmental flow is violated. About 22% of the environmental flow infringement of the blue water footprint of global consumption lies outside the specific countries of consumption, indicating that a number of them have externalized their impacts. By establishing a link between the consumption of a product in one place and water scarcity in places far from the place of consumption, our assessment may aid a dialogue on how to assign and share responsibilities concerning water use.

Past, Present, and Future of Virtual Water and Water Footprint

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

Towards quantification of the national water footprint in rice production of China: A first assessment from the perspectives of single-double rice

Rice is one of the most important crops in China, contributing to approximately 28% of total cereal yield. Despite substantial production, given that rice is a high water-consuming crop, the water shortage due to the irreversible decline in available water resources on a global scale induced by undergoing climate change will pose grave challenges to rice reproductive growth and related water resources utilization. As a consequence, investigating the responses of rice productivity and water consumption to more pronounced climate changes is of great significance for water resources sustainable utilization in terms of reducing irrigation water requirements and ensuring food security. Present water footprint (WF) methods do not calculate the weighted average of each WF component at the national level when evaluating the effects of prospective climate change upon rice production. The national water footprint (NWF), i.e. taking the share of each province in the total production of crops as weighting factors, has been regarded as an effective approach to determine where each WF component is originally located. In this study, the temporal change characteristics of NWF for single-rice (SR), early-rice (ER) and late-rice (LR) in different agro-ecological zones across China during 2001-2010 were assessed for the first time. The results exhibited that NWF of rice was an estimated 304,848 million cubic meters (MCM) per year. The SR accounted for the greatest portion of NWF, followed by ER and LR. The NWF rank was SR-V > SR-I > ER-VI > SR-IV > LR-III > LR-VI > SR-II > ER-III. The blue water footprint (WF_b) presents decreasing trends in most agro-ecological zones (SR-I, SR-II, SR-IV, ER-III and LR-VI), while green water footprint (WF_g) exhibits increasing trends within these regions. This study provides a beneficial approach for decision-making processes aiming at better agricultural water resources management strategies to alleviate water resources scarcity and reduce food risk in the context of surging demand, which will support agricultural water resources management of China towards a more balanced direction at the national level.

Globalized energy-water nexus through international trade: The dominant role of non-energy commodities for worldwide energy-related water use

The increasing energy demand in future will inevitably escalate pressures on water resources, as energy production needs huge amounts of water inputs. Globalization has resulted in the geographic separation between the source of water inputs for energy production and the sink of its final consumption, making it crucial to factor global supply chain effect into water-energy nexus management. Therefore, this paper investigates water use for energy from source of exploitation to sink of final consumption along global supply chains based on embodiment accounting method. In total, the energy-related water use embodied in international trade is in magnitude about 80% of global total energy-related water use in 2011. It should be noted that non-energy commodities contribute more than four fifths of energy-related water use embodied in international trade and global final consumption. China serves the largest exporter of energy-related water use while EU28 is the biggest receiver. From a perspective of global supply chains, two thirds of USA direct energy-related water use sinks into final consumption from rest of the world, and over a quarter of that embodied in Mainland China's final consumption is from USA, showing the tight relation between them on global supply chains. Findings highlight the urgent need to consider international trade (i.e., energy and non-energy commodity trade) and global supply chain effects for water-energy nexus policy-making to ensure the sustainable water supply for energy development.

Assessment of Inter-Sectoral Virtual Water Reallocation and Linkages in the Northern Tianshan Mountains, China

Quantitative analysis of the reallocation and linkages of virtual water in the economic sector was important for the integrated water resources management in inland arid regions. Taking the northern Tianshan Mountains (NTM) as an example, we applied the environmental input-output model to design the accounting framework for the reallocation of blue and green virtual water (VW) in the economic sector and analyzed the correlation effect of VW reallocation among various sectors by backward and forward linkages in economic analysis. The results showed that the direct blue and green water consumption of primary industry respectively accounted for 99.2% and 100% of the total water consumption in NTM. Planting sector had the largest amount of VW outflow among all sectors. Animal husbandry, forestry and construction had a large pulling effect on VW outflow of planting sector, while planting sector and animal husbandry were the main sectors for VW export of blue and green water. We suggest that the government can increase the import of blue-green VW for agricultural raw materials through VW trade and develop industries such as service and electricity that have less pulling effect on the primary industry VW, so as to improve the economic added value of VW in the primary industry and reduce the loss of VW in primary industry production and trade flows in future water management.

Comparative Analysis of Carbon, Ecological, and Water Footprints of Polypropylene-Based Composites Filled with Cotton, Jute and Kenaf Fibers

Composites containing natural fibers are considered environmentally friendly materials which is related to the reduced use of fossil fuels and the emission of carbon dioxide compared to petroleum-based polymers. Nevertheless, a complete evaluation of their environmental impact requires a broader view. This paper presents a carbon, ecological, and water footprints assessment of polypropylene-based composites filled with cotton, jute, and kenaf fibers based on a standardized European pallet (EUR-pallet) case study. Obtained results were compared with unmodified polypropylene and composite with glass fibers. Incorporation of 30 wt% of cotton, jute, and kenaf fibers into a polypropylene matrix reduced its carbon footprint by 3%, 18%, and 18%, respectively. Regarding the ecological footprint, an 8.2% and 9.4% reduction for jute and kenaf fibers were noted, while for cotton fibers, its value increased by 52%. For these footprints, the use of jute and kenaf fibers was more beneficial than glass fibers. Nevertheless, the application of natural fibers caused a 286%, 758%, and 891% drastic increase of water footprint of the final product, which was mainly affected by cultivation and irrigation of crops. Therefore, in a holistic view, the incorporation of natural fibers into the polypropylene matrix definitely cannot be impartially considered as an environmentally friendly solution.

Assessment of climate change impact on rice yield and water footprint of large-scale and individual farming in Thailand

Large-scale farming (participation in large-scale agricultural extension program) and individual farming (no participation) are two farming management practices of rice cultivation in Thailand, both of which cause significant water consumption and degradation and are vulnerable to climate change. However, given that climate change will influence both grain yield and water resource availability, it is not fully understood which type of farming management practice is more adaptive to climate change. This study aims to evaluate the adaptation capabilities of large-scale and individual farming by simulating rice yield changes under future climatic conditions and estimating the climate change impact on the water footprint (WF) of rice production. Rice management practices were obtained from large-scale and individual farming. Five General Circulation Models of RCP4.5 and RCP8.5 scenarios under four future time periods were used as future climate projections. Simulation results show a remarkable increase in rice yield of individual and large-scale farming under RCP4.5, ranging from 1.3 to 29.8% and 2.0 to 30.8%, respectively, whereas it fluctuates from 11.7 to -29.0% and 8.3 to -20.8% under RCP8.5 for individual and large-scale farming, respectively. The projected total WF of rice production under RCP4.5 will decline, ranging from -10.0 to -43.0% and -0.5 to -67.0% for individual and large-scale farming, respectively. Conversely, the RCP8.5 shows a fluctuation in projected total WF of -26.5 to 63.3% and -51.1 to 60.0% for individual and large-scale farming, respectively. The total WF, mainly grey WF, in large-scale farming is lower than in individual farming. The increase of rice yield under RCP4.5 is due to an increment of temperature and precipitation, resulting in a decrease of the total WF and vice versa for RCP8.5. The large-scale farms are highlighted as adopting appropriate management practices for rice production in which they can maintain rice yield and reduce grey WF.

Tension of Agricultural Land and Water Use in China's Trade: Tele-Connections, Hidden Drivers and Potential Solutions

Interregional trade can potentially extend the management of scarce resources beyond a region's territory along supply chains. Here we combined the multiregional input-output model with structural decomposition analysis to reveal the distant connections of agricultural land and water use as well as the drivers behind their variations in China. Our results show that trade-embodied agricultural land use increase by 2.3-fold and 2.5-fold for virtual agricultural water use flows from 2002 to 2012. The water-starved northern China with abundant agricultural land is the main exporter of virtual (also called trade-embodied) agricultural land and water. Moreover, the role of the virtual water use importers and exporters were determined by the availability of land, rather than water resources. Based on scenario analysis, we found that if agricultural water use efficiency of north China reached the world's top-level but agricultural land use efficiency remained unchanged, the virtual water flows would be reduced by 32% and only water resources, not agricultural land, would be able to sustain future economic development. Our findings may provide significant information for potential solutions to China's regional water shortage from a land-water nexus perspective.

Assessment of climate change impact on the water footprint in rice production: Historical simulation and future projections at two representative rice cropping sites of China

As one of the most important crops cultivated in China, rice contributes to approximately 28% of total yield. In despite of the substantial production, rice productivity is gravely affected by ongoing climate change and reduction of available water resources. Thus, assessing the responses of rice water consumption and productivity to more pronounced climate change is of great significance to water resources management in terms of relieving the resources shortage and meeting the food demand. In this study, the yield and water resources utilization during 1961-2010 in two typical rice plantation regions of China were evaluated using validated rice model ORYZA2000. Subsequently, their responses to future climate scenarios of 21 century were investigated through driving ORYZA2000 with downscaling climatic projections from GCMs under four RCPs emission scenarios. To quantify the water resources utilization in rice production from multiple perspectives, the water footprint (WF) and three water productivity indices (WP_I, WP_U and WP_ET) were integrated for assessing the regional agricultural water stress in this paper. The results revealed that the annual average linear inclining rates of WF in two stations (Kaifeng and Kunshan) were 3.86 m³/ t and 2.62 m³/ t, respectively. Moreover, compared with the green water footprint (WF_g), the blue water footprint (WF_b) is projected to significantly increase in future. The water productivity (WP) would decrease in two stations under four RCPs scenarios except that the WP_u and WP_ET of Kunshan under RCP2.6 and RCP4.5 scenario in 2020s, 2050s and 2080s. Hence, this study provides insights into comprehensively understand the influences of climate change on food security and sheds lights on the regional strategy for future water resource management.

Spatio-Temporal Variations in Groundwater Revealed by GRACE and Its Driving Factors in the Huang-Huai-Hai Plain, China

The Huang-Huai-Hai (3H) Plain is the major crop-producing region in China. Due to the long-term overexploitation of groundwater for irrigation, the groundwater funnel is constantly expanding and the scarcity of water resources is prominent in this region. In this study, Gravity Recovery and Climate Experiment (GRACE) and hydrological models were used to estimate the spatial-temporal changes of groundwater storage (GWS) and the driving factors of GWS variations were discussed in the 3H Plain. The results showed that GRACE-based GWS was depleted at a rate of -1.14 ± 0.89 cm/y in the 3H Plain during 2003 to 2015. The maximum negative anomaly occurred in spring due to agricultural irrigation activities. Spatially, the loss of GWS in the Haihe River Basin is more serious than that in the Huaihe River Basin, presenting a decreasing trend from south to north. Conversely, the blue water footprint (WF_blue) of wheat exhibited an increasing trend from south to north. During the drought years of 2006, 2013, and 2014, more groundwater was extracted to offset the surface water shortage, leading to an accelerated decline in GWS. This study demonstrated that GWS depletion in the 3H Plain is well explained by reduced precipitation and groundwater abstraction due to anthropogenic irrigation activities.

Inter-Regional Agricultural Virtual Water Flow in China Based on Volumetric and Impact-Oriented Multi-Regional Input-Output (MRIO) Approach

Virtual water trading is an effective strategy to alleviate water shortage. Several different methods have been developed to achieve quantitative description and evaluation of virtual water, which can be broadly divided into volumetric and impact-oriented water footprint approaches. The former focuses on the consumption of water resources, while the latter puts greater emphasis on assessing the water use impacts. Based on the volumetric and impact-oriented water footprint, this paper conducted a comprehensive study on the virtual water flow of agricultural products among regions in China. The results show that different water footprint evaluation methods have different tendencies in evaluating virtual water flow. Volumetric virtual water mainly flows from northwest and northeast China to north and east China, while impact-oriented virtual water mainly flows from northwest and central south China to east and north China. Northwest China is the largest net export region of agricultural virtual water, and it is dominated by direct water consumption. In addition, we compared the net export volume of virtual water and the water shortage situation among regions in China. North China, where the water shortage is very serious, mainly relies on external water sources, while northwest China, which also faces a water shortage problem, exports a large amount of virtual water to external sources. The findings of this study highlight the importance of taking full account of the response measures in both cases when formulating policies. In other words, the virtual water strategy should consider water quantity and water quality simultaneously.

Water for maize for pigs for pork: An analysis of inter-provincial trade in China

Trade in commodities implies trade in virtual water (VW), which refers to the water that was used to produce the traded goods. Various studies have quantified international or inter-provincial virtual water (VW) flows related to the trade in crops and animal products. Until date, however, no effort has been undertaken to understand how the water embodied in traded feed crops (trade stage TS1) will be transferred further because of trade in animal products (trade stage TS2). This is the first study showing this mechanism, in a case study in China for maize (the major pig feed) and pork (the dominant meat), considering the period 2000-2013. We estimate the annual green and blue water footprints in maize production and then quantify the inter-provincial VW flows related to trade in maize (TS1) and trade in maize embodied in pork (TS2). Results show that in TS1, maize-related VW flowed from the water-scarce North to the water-rich South, with an increase of 40% over the study period (from 43 to 61 billion m³ y^-1). In TS2, about 10% of the water embodied in maize exports from North to South China returns in the form of pork, with an increase in the absolute amount of 25% (from 4.8 to 6.1 billion m³ y^-1). Considering blue VW flows specifically, we find that North-to-South blue VW flows decreased by 5% in TS1, while South-to-North blue VW flows increased by 23% in TS2.

Water Footprint Assessment of Selected Polymers, Polymer Blends, Composites, and Biocomposites for Industrial Application

This paper presents a water footprint assessment of polymers, polymer blends, composites, and biocomposites based on a standardized EUR-pallet case study. The water footprint analysis is based on life cycle assessment (LCA). The study investigates six variants of EUR-pallet production depending on the materials used. The system boundary included the production of each material and the injection molding to obtain a standardized EUR-pallet of complex properties. This paper shows the results of a water footprint of six composition variants of analyzed EUR-pallet, produced from biocomposites and composites based on polypropylene, poly(lactic acid), cotton fibers, jute fibers, kenaf fibers, and glass fibers. Additionally, a water footprint of applied raw materials was evaluated. The highest water footprint was observed for cotton fibers as a reinforcement of the analyzed biocomposites and composites. The water footprint of cotton fibers is caused by the irrigation of cotton crops. The results demonstrate that the standard EUR-pallet produced from polypropylene with glass fibers as reinforcement can contribute to the lowest water footprint.

Environmental impact assessment of wastewater discharge with multi-pollutants from iron and steel industry

The iron and steel industry discharges large quantities of wastewater. The environmental impact of the wastewater is traditionally assessed from the quantitative aspect. However, the water quality of discharged wastewater plays a more significant role in damaging the natural environment. Moreover, comprehensive assessment of multi-pollutants in wastewater from both quality and quantity is still a gap. In this work, a total environmental impact score (TEIS) is defined to assess the environmental impact of wastewater discharge, by considering the volume of wastewater and the quality of main processes. To implement the comprehensively qualitative and quantitative assessment, a field monitoring and measurement of wastewater discharge volume and the quality is conducted to acquire pH, suspend solids (SS), chemical oxygen demand (COD), total nitrogen (TN), total iron (TFe), and hexavalent chromium (Cr(VI)). The sequence of TEIS values is obtained as steelmaking > ironmaking > sintering > hot rolling > coking > cold rolling and TN > COD > SS > pH > Cr(VI) > TFe. The TEIS of the investigated steel plant is 26.27. The leading process lies in steelmaking with a TEIS of 19.98. The dominant pollutant is TN with a TEIS of 15.00. Finally, a sensitivity analysis is performed to validate the feasibility and generalisability of the TEIS.

Spatial–Temporal Matching Characteristics between Agricultural Water and Land Resources in Ningxia, Northwest China

Agricultural water and land resources are key elements of human production and their unbalanced distribution has threatened the sustainable development of agriculture and regional food security. This study is aiming to investigate the spatial–temporal changes of matching characteristics between agricultural water and land resources in Ningxia during 2007 to 2017. The agricultural irrigation water (AIW), farmland area (FA) and effective irrigated area (EIA) were selected as quantity parameters for agricultural water and land resource. Results show that the gravity centers of AIW and EIA both moved in the southeast direction, while the gravity center of FA moved northwestward, which indicated a better spatial matching degree between AIW and EIA. According to the Gini coefficient and total spatial mismatch index, the spatial mismatch between AIW and FA of Ningxia was remedied and that of AIW and EIA was worse. Counties with sufficient and insufficient AIW were distributed in the north and the south of Ningxia, respectively. The sensitivity of agricultural irrigation water to land resources remarkably increased in the study period, particularly for the counties in northern area of Ningxia. The findings may provide implications for effective management of regional agricultural water and land resources.

Ecological network analysis of an urban water metabolic system based on input-output model: A case study of Guangdong, China

When considering a region as a superorganism, there are various processes of metabolism that reflect the growth and maintenances of the system, as well as the interactions with the surroundings. Ecological Network Analysis combined with the input-output model is utilized to analyze the water consumption structure and the interaction control relationships among different sectors within the urban ecosystem. The integrated approach is applied to the case study of Guangdong Province, China. The Water Ecological Network model is developed by the monetary I-O table of Guangdong province in 2012. The network control analysis is employed to describe the pathway of indirect water. In addition, the competitive and mutual relationship among different sectors is concluded by the approach of network utility analysis. This study also newly compares "virtual water (which is the indirect water) imports of per unit Gross Domestic Product (GDP)" and "water consumption of per unit GDP" to reveal which of them contributes more to the urban metabolism. The results indicate that the top three controllers are machinery, equipment and other services, followed closely by food and tobacco processing. The model results also show that the negative effects among different sectors accounting for the majority in all relationships, which indicates that the system under investigation is not in a mutualism state. This is due to that the competition of water uses between the economic sectors weaken the virtual water circulation within the system. The results are valuable to provide scientific suggestions for improving water use efficiency and make reasonable virtual water policy.

Driving Factors of Agricultural Virtual Water Trade between China and the Belt and Road Countries

China proposed the Belt and Road Initiative (BRI), an unprecedented development strategy in terms of scope and scale, to increase the connectivity with the rest of the world by infrastructure development and trade activities. Recently, more attention has been directed to the environmental implications of the international trade activities under this initiative, which contributes to the development of a green, i.e. environmentally friendly, partnership. This study examines the evolution of virtual water trade in relation to agricultural products between China and BRI countries during 2000-2016. The Logarithmic Mean Divisia Index (LMDI) method is adopted for uncovering the driving factors underlying the trade imbalance, as well as the major virtual water exports. Results reveal that China has experienced the shift from a net virtual water exporter to a net importer. At the regional level, Southeastern Asia and Southern Asia are the major net virtual water exporters to China, and Eastern Asia is the major importer. For the selected export countries, an increase in proportion of trade in relation to domestic production significantly contributes to their virtual water export, while water intensity could decrease virtual water export for most export countries. As for the driving forces behind the imbalance of virtual water trade, trade structure was an obvious positive effect, while the effects of water intensity, product structure, and trade scale shifted in favor of virtual water outflows from BRI countries to China in 2008. Massive global water loss has incurred, indicating the inefficiency of this partnership in relation to freshwater. A closer trade relationship is established between China and BRI countries, and relevant environment implications are identified. Policy implications are proposed in terms of trade structure, relationship of trade and domestic production, and international cooperation. This study provides valuable insights into the equity and sustainability of historic trade activities with respect to freshwater resources.

Explaining virtual water trade: A spatial-temporal analysis of the comparative advantage of land, labor and water in China

The well-known "virtual water hypothesis" states that water-deficient regions/countries could alleviate water stress through importing water-intensive products from water-abundant regions/countries. Although observed trading patterns do often not support this hypothesis, there is a lack of research to explore the reasons why trade patterns often do not support the intuitive virtual water hypothesis. To fill this important gap, we introduce comparative advantage theory in a quantitative way to track the driving forces of net virtual water export based on the spatial-temporal distribution of resource productivity and opportunity costs of land, labor and water use in agricultural and non-agricultural sectors across Chinese provinces between 1995 and 2015. The results show that regional differences in land productivity between agricultural and non-agricultural sectors are the main forces determining the pattern of virtual water flows across major regions, and other resources such as labor and water have played only a limited role. Our study shows that the current market forces reflect the scarcity of land resources, but does not reflect the water scarcity in the context of interregional trade in China. Our findings suggest that the ongoing efforts to increase land productivity of agriculture in the southern regions would contribute to reducing water scarcity in the North and Northeast China Plain.

Transfer of virtual water embodied in food: A new perspective

Food and water are inextricably linked. With the increase of water consumption in irrigation and food growth, water shortage has become an urgent issue. Irrational cross-regional transfer of water embodied in food exacerbates water scarcity and restrict China's sustainable development. Given that, a Virtual Water-Food Nexus Model is developed to quantify the inter-provincial transfer of water embodied in food and to identify the complicated interactions between different provinces. In detail, Environmental Input-Output Analysis is applied to quantitatively estimate the inter-provincial water transfer embodied in food trades. Based on the network constructed by interrelated nature of nexus, the mutual interactions, control situation, and the dominant and weak pathways are examined through the combination of Ecological Network Analysis and Principal Component Analysis. Two new indictors water consumption intensity and water supply capacity are first performed to measure the role of each province from the supply and consume side respectively. It is revealed that interregional food transactions failed to realize water resources dispatching management. Many water-deficient regions suffered from massive virtual water losses through food exports, but water-rich areas still import large quantities of food containing virtual water. Results show that exploitation and competition dominate the ecological relationships between provinces. Agricultural GDP ratio is the indicator which most affect water consumption intensity and water supply capacity. Network-based research contributes more insights into the recognition of water management responsibilities across provinces and municipalities. These findings will provide a scientific support to adjust unreasonable allocation of water resources in China in an attempt to addressing the contradiction between food demand and water shortages.

Water Footprint Allocation under Equity and Efficiency Considerations: A Case Study of the Yangtze River Economic Belt in China

From a water footprint perspective, this paper adopts Gross Domestic Product (GDP) as the influencing factor to construct a lexicographical optimization framework for optimizing water resources allocation under equity and efficiency considerations. This approach consists of a lexicographic allocation of water footprints (LAWF) model and an input-output capacity of water footprints (IOWF) model. The proposed methodology is then applied to allocate water resources in the Yangtze River Economic Belt (YREB) by employing the 2013 cross-sectional data in the area. The results show that: (1) The LAWF scheme signifies reductions in water footprints in each of the YREB administrative units, thereby significantly strengthening their IOWFs. (2) IOWFs are affected by industrial attributes and natural endowments, and the impact tends to vary across different industries and regions. (3) Policy suggestions are proposed to effectively enhance the IOWFs of the weakest industries across the three YREB regions to exploit their natural endowments.

Assessment of Lexicographic Minimax Allocations of Blue and Green Water Footprints in the Yangtze River Economic Belt Based on Land, Population, and Economy

To assess different impacts of land, population and economy factors on the lexicographic minimax optimal allocation of blue and green water footprints, a comprehensive discriminant rule is constructed in this paper based on the Gini coefficient and Theil entropy index. The proposed rule is employed to estimate the influence of the aforesaid factors (land, population and economy) on the corresponding allocation schemes from a fairness perspective. To demonstrate its applicability, the proposed approach is applied to a water resources allocation study for 11 provinces in the Yangtze River Economic Belt (YREB). The results indicate that: (1) the economy-based lexicographic allocation of water footprints (LAWF) is more equalitarian for the provinces with high water footprint quotas. The land area-based LAWF is more equalitarian for the provinces with low water footprint quotas. The population-based LAWF is more equalitarian for the provinces with medium water footprint quotas. (2) The contribution of intra-regional variation in the population-based LAWF scheme is the largest of the three schemes. The inter-regional variation contributed the largest in the land area-based LAWF scheme. (3) Two synthetic schemes which integrate multiple factors among land area, economy and population are more equalitarian than the three single-factor schemes. Compared with the original situation which is an equalitarian but ineffective allocation, the two synthetic schemes have greater effect on the improvement of the supply-demand balance of water resources carrying capacity. Therefore, the defect of the population, economy and land area factors acting alone should be resolved by designing a weighting system, in order to optimize the allocation of water resources.

Evolution of China's water footprint and virtual water trade: A global trade assessment

Water embodied in traded commodities is important for water sustainability management. This study provides insight into China's water footprint and virtual water trade using three specific water named Green, Blue and Grey. A multi-region input-output analysis at national and sectoral analysis levels from the years 1995 to 2009 is conducted. The evolution and position of China's virtual water trade across a global supply chain are explored through cluster analysis. The results show that China represented 11.2% of the global water footprint in 1995 and 13.6% in 2009. The green virtual water is the largest of China's exports and imports. In general, China is a net exporter of virtual water during this time period. China mainly imports virtual water from the USA, India and Brazil, and mainly exports virtual water to the USA, Japan and Germany. The agriculture sector and the food sector represent the sectors with both the largest import and export virtual water quantities. China's global virtual water trade network has been relatively stable from 1995 to 2009. China has especially close relationships with the USA, Indonesia, India, Canada, Mexico, Brazil and Australia. Trade relations, resource endowment and supply-demand relationships may play key roles in China's global virtual water footprint network rather than geographical location. Finally, policy implications are proposed for China's long term sustainable water management and for global supply chain management in general.

Equitable Allocation of Blue and Green Water Footprints Based on Land-Use Types: A Case Study of the Yangtze River Economic Belt

This paper develops a lexicographic optimization model to allocate agricultural and non-agricultural water footprints by using the land area as the influencing factor. An index known as the water-footprint-land density (WFLD) index is then put forward to assess the impact and equity of the resulting allocation scheme. Subsequently, the proposed model is applied to a case study allocating water resources for the 11 provinces and municipalities in the Yangtze River Economic Belt (YREB). The objective is to achieve equitable spatial allocation of water resources from a water footprint perspective. Based on the statistical data in 2013, this approach starts with a proper accounting for water footprints in the 11 YREB provinces. We then determined an optimal allocation of water footprints by using the proposed lexicographic optimization approach from a land area angle. Lastly, we analyzed how different types of land uses contribute to allocation equity and we discuss policy changes to implement the optimal allocation schemes in the YREB. Analytical results show that: (1) the optimized agricultural and non-agricultural water footprints decrease from the current levels for each province across the YREB, but this decrease shows a heterogeneous pattern; (2) the WFLD of 11 YREB provinces all decline after optimization with the largest decline in Shanghai and the smallest decline in Sichuan; and (3) the impact of agricultural land on the allocation of agricultural water footprints is mainly reflected in the land use structure of three land types including arable land, forest land, and grassland. The different land use structures in the upstream, midstream, and downstream regions lead to the spatial heterogeneity of the optimized agricultural water footprints in the three YREB segments; (4) In addition to the non-agricultural land area, different regional industrial structures are the main reason for the spatial heterogeneity of the optimized non-agricultural water footprints. Our water-footprint-based optimal water resources allocation scheme helps alleviate the water resources shortage pressure and achieve coordinated and balanced development in the YREB.

The role of the water footprint in the context of green marketing

The environmental degradation, because of various factors, such as climate change, human activities, increase of population globally, etc. have brought on pressures on the fresh water supplies that vary on time and space. Consequently, economic, environmental, and social tools have emerged known as footprints, in an effort to examine and measure the needs and consequences of humanity on the Earth's life support systems and take measures towards sustainable development. Furthermore, the constantly worsening environmental conditions have resulted in the cultivation of a green culture among society stakeholders that brought on terms such as green marketing and green products. This paper deals with the water footprint (WF) concept and an effort is performed, to explore through a literature review, in which ways it can contribute to the sustainable development of water use, in the context of green marketing (GM) strategies. The approach of the analysis is based on the discrimination to the following aspects: international scale, national and subnational scale, farmers, business, and consumers, in order to track the affection of each part in water issues. The main findings of the literature review showed that the aforementioned factors are playing a key role in protecting water recourses, by the way they formulate their water use and they are interrelated and interdependent. WFs can be useful in the context of GM, by providing helpful information about direct and indirect water consumption, to every contributor factor in supply chains, to consumers, governments, and water managers.

Blue and Green Water Footprint Assessment for China—A Multi-Region Input–Output Approach

Research on blue and green water footprints (WF) for China has typically been carried out based on bottom-up and top-down approach using a single-region input–output table. However, this research typically lacks detail on the sectoral interrelationships which exist between China and its trading partners in other countries/regions of the world. Here, a multi-region input–output approach using the WIOD database was applied to quantify the blue and green WF for China in 2009. The quantification was conducted from both production (WFP) and consumption (WFC) perspectives. The results show that the total WFP for China in 2009 was 1152.2 km3, second only to India. At 1070.9 km3, China had the largest WFC volume in the world. The internal WF was 953.5 km3, taking the substantial share for both the WFC and WFP. Overall, China’s trade resulted in a net export of 53.5 km3 virtual water. In contrast, the agricultural sector resulted in a net import of 70.6 km3 virtual water to China, with United States, Brazil, and Canada acting as major suppliers. This study suggests that quantifying the WF of China at global level through a MRIO framework is a necessary step towards achieving sustainability for China’s water management.

Seasonal forecasting of green water components and crop yield of summer crops in Serbia and Austria

A probabilistic crop forecast based on ensembles of crop model output estimates, presented here, offers an ensemble of possible realizations and probabilistic forecasts of green water components, crop yield and green water footprints (WFs) on seasonal scales for selected summer crops. The present paper presents results of an ongoing study related to the application of ensemble forecasting concepts in crop production. Seasonal forecasting of crop water use indicators (evapotranspiration (ET), water productivity, green WF) and yield of rainfed summer crops (maize, spring barley and sunflower), was performed using the AquaCrop model and ensemble weather forecast, provided by The European Centre for Medium-range Weather Forecast. The ensemble of estimates obtained was tested with observation-based simulations to assess the ability of seasonal weather forecasts to ensure that accuracy of the simulation results was the same as for those obtained using observed weather data. Best results are obtained for ensemble forecast for yield, ET, water productivity and green WF for sunflower in Novi Sad (Serbia) and maize in Groß-Enzersdorf (Austria) - average root mean square error (2006-2014) was <10% of observation-based values of selected variables. For variables yielding a probability distribution, capacity to reflect the distribution from which their outcomes will be drawn was tested using an Ignorance score. Average Ignorance score, for all locations, crops and variables varied from 1.49 (spring barley ET in Groß-Enzersdorf) to 3.35 (sunflower water productivity in Groß-Enzersdorf).

Probabilistic evaluation of the water footprint of a river basin: Accounting method and case study in the Segura River Basin, Spain

In the current study a method for the probabilistic accounting of the water footprint (WF) at the river basin level has been proposed and developed. It is based upon the simulation of the anthropised water cycle and combines a hydrological model and a decision support system. The methodology was carried out in the Segura River Basin (SRB) in South-eastern Spain, and four historical scenarios were evaluated (1998-2010-2015-2027). The results indicate that the WF of the river basin reached 5581 Mm³/year on average in the base scenario, with a high variability. The green component (3231 Mm³/year), mainly generated by rainfed crops (62%), was responsible for the great variability of the WF. The blue WF (1201 Mm³/year) was broken down into surface water (56%), renewable groundwater (20%) and non-renewable groundwater (24%), and it showed the generalized overexploitation of aquifers. Regarding the grey component (1150 Mm³/year), the study reveals that wastewater, especially phosphates (90%), was the main culprit producing water pollution in surface water bodies. The temporal evolution of the four scenarios highlighted the successfulness of the water treatment plans developed in the river basin, with a sharp decrease in the grey WF, as well as the stability of the WF and its three components in the future. So, the accounting of the three components of the WF in a basin was integrated into the management of water resources, it being possible to predict their evolution, their spatial characterisation and even their assessment in probabilistic terms. Then, the WF was incorporated into the set of indicators that usually is used in water resources management and hydrological planning.

Virtual water trade patterns in relation to environmental and socioeconomic factors: A case study for Tunisia

Growing water demands put increasing pressure on local water resources, especially in water-short countries. Virtual water trade can play a key role in filling the gap between local demand and supply of water-intensive commodities. This study aims to analyse the dynamics in virtual water trade of Tunisia in relation to environmental and socio-economic factors such as GDP, irrigated land, precipitation, population and water scarcity. The water footprint of crop production is estimated using AquaCrop for six crops over the period 1981-2010. Net virtual water import (NVWI) is quantified at yearly basis. Regression models are used to investigate dynamics in NVWI in relation to the selected factors. The results show that NVWI during the study period for the selected crops is not influenced by blue water scarcity. NVWI correlates in two alternative models to either population and precipitation (model I) or to GDP and irrigated area (model II). The models are better in explaining NVWI of staple crops (wheat, barley, potatoes) than NVWI of cash crops (dates, olives, tomatoes). Using model I, we are able to explain both trends and inter-annual variability for rain-fed crops. Model II performs better for irrigated crops and is able to explain trends significantly; no significant relation is found, however, with variables hypothesized to represent inter-annual variability.

Water footprint assessment for crop production based on field measurements: A case study of irrigated paddy rice in East China

Water footprint (WF) is a comprehensive measure of water consumption by human activities and can be used to assess the impact on both water volume and quality. This study aims to explore the feasibility of evaluating green, blue and grey WFs of crop production based on field measurements. The irrigated paddy rice grown in three different experimental sites in different typical irrigation districts in Huai'an, East China over 2011 to 2014 was taken as study case. With fixed irrigation and fertilization, on the basis of measuring field water and fertilizer balance at daily step, we calculated WF of crop production under different test treatments. Results show that crop water requirement of rice was measured as 667.1mm and 6.2% of the total nitrogen (T-N) was washed away from farmland accompany with drainage and percolation. Average annual WF of paddy rice during 2011-2014 in Huai'an was 1.760m³/kg (33.3% green, 25.8% blue and 40.9% grey). The level of WF and blue water proportion in different locations (irrigation districts) and different years changed slightly, while the proportion of green and grey WF changed with the variance of precipitation. Green water proportion was 25.1%, 34.2 and 44.2%, while 48.0%, 40.2% and 31.0% for grey water proportion under precipitation levels of 400, 600 and 800mm, respectively. The reduced grey WF was due to increased drainage. This study not only proved the feasibility of assessing WF of crop production with field experiments, but also provided a new method for WF calculation based on field water and fertilizer migration processes.

Assessing water scarcity in agricultural production system based on the generalized water resources and water footprint framework

An indicator, agricultural water stress index (AWSI), was established based blue-green water resources and water footprint framework for regional water scarcity in agricultural production industry evaluation. AWSI is defined as the ratio of the total agricultural water footprint (AWF) to water resources availability (AWR) in a single year. Then, the temporal and spatial patterns of AWSI in China during 1999-2014 were analyzed based on the provincial AWR and AWF quantification. The results show that the annual AWR in China has been maintained at approximately 2540Gm³, of which blue water accounted for >70%. The national annual AWF was approximately 1040Gm³ during the study period and comprised 65.6% green, 12.7% blue and 21.7% grey WFs The space difference in both the AWF for per unit arable land (AWFI) and its composition was significant. National AWSI was calculated as 0.413 and showed an increasing trend in the observed period. This index increased from 0.320 (mid-water stress level) in 2000 to 0.490 (high water stress level) in the present due to the expansion of the agricultural production scale. The Northern provinces, autonomous regions and municipalities (PAMs) have been facing high water stress, particularly the Huang-Huai-Hai Plain, which was at a very high water stress level (AWSI>0.800). Humid South China faces increasingly severe water scarcity, and most of the PAMs in the region have converted from low water stress level (AWSI=0.100-0.200) to mid water stress level (AWSI=0.200-0.400). The AWSI is more appropriate for reflecting the regional water scarcity than the existing water stress index (WSI) or the blue water scarcity (BWS) indicator, particularly for the arid agricultural production regions due to the revealed environmental impacts of agricultural production. China should guarantee the sustainable use of agricultural water resources by reducing its crop water footprint.