Food–Energy–Water Nexus: Quantifying Embodied Energy and GHG Emissions from Irrigation through Virtual Water Transfers in Food Trade

Water consumed by power plants is transferred virtually from producers to consumers on the electric grid. This network of virtual transfers varies spatially and temporally on a sub-annual scale. In this study, we focused on cooling water consumed by thermoelectric power plants and water evaporated from hydropower reservoirs. We analyzed blue and grey virtual water flows between balancing authorities in the United States electric grid from 2016 to 2021. Transfers were calculated using thermoelectric water consumption volumes reported in Form EIA-923, power plant data from Form EIA-860, water consumption factors from literature, and electricity transfer data from Form EIA-930. The results indicate that virtual water transfers follow seasonal trends. Virtual blue water transfers are dominated by evaporation from hydropower reservoirs in high evaporation regions and peak around November. Virtual grey watertransfers reach a maximum peak during the summer months and a smaller peak during the winter. Notable virtual blue water transfers occur between Arizona and California as well as surrounding regions in the Southwest. Virtual grey water transfers are greatest in the Eastern United States where older, once-through cooling systems are still in operation. Understanding the spatial and temporal transfer of water resources has important policy, water management, and equity implications for understanding burden shifts between regions.

Unveiling the inequalities in virtual water transfer in China: The environmental and economic perspectives

The North China Plain is the scarcest water region in China. Its water security is closely related to interregional water movement, which can be realized by real water transfers and/or virtual water transfers. This study investigates the roles of virtual water trade and real water transfer using the Interregional Input-Output model. The results show that the region is receiving 19.4 billion m3/year of virtual water from the interregional trade, while exporting 16.4 billion m3/year of virtual water in the international trade. In balance, the region has a net virtual water gain of 3 billion m3/year from the outside. Its virtual water inflow is dominated by agricultural products from other provinces, totalling 16.6 billion m3/year, while its virtual water export is dominated by manufacturing sectors to other countries, totalling 11.7 billion m3/year. Both virtual water imports and real water transfers from the South to North Water Diversion Project are important water supplements for the region. The results of this study provide useful scientific references for the establishment of combating strategies to deal with water scarcity in the future.

Interprovincial trade has expanded China’s virtual water consumption and economic development. This study uses an environmental–economic inequality index to calculate the virtual water and economic benefit transfer imbalances in interprovincial trade and applies a structural path analysis (SPA) model to find the imbalances on the key virtual water supply chain paths between provinces. The findings are fourfold. (1) The developed provinces, such as Guangdong, Jiangsu, and Shandong, had more virtual water on the consumption side from 2002 to 2017 and had the most value added on the consumption and production sides. (2) The developing provinces in northwest and central China suffered from net virtual water outflows and negative value-added gains in bilateral trade with developed provinces. (3) The developed provinces, such as Beijing, acquired more virtual water from other provinces in 0–5 production tiers, but only a small part of the value added was transferred out. (4) All of the four top ranking virtual water supply chain paths of Beijing came from other provinces, accounting for 28.22% of the total virtual water flowing to Beijing, but their value added only accounted for 1.44%. It is suggested that provinces adopt differentiated water-use systems to reduce virtual water transfer imbalances and provide subsidies to the nodes to compensate the economic benefits on key virtual water supply chain paths.

<p>Agricultural production is accompanied by a large amount of water consumption, nonpoint source pollution, and greenhouse gas emissions. However, the comprehensive and quantitative analysis of associated impacts on regional water, the environment, and the economy caused by variations in agricultural distribution is insufficient. This paper evaluates the evolution of grain production distribution and its effects on water resources, the economy, and the environment in China by using virtual water theory. The results show that the grain production area located in northern China is characterized by scarce water resources and a less developed economy. Due to the imbalance between grain supply and demand, virtual water embedded in grain will transfer among regions. These flows have formed a pattern where virtual water transfers from the water‐scarce northern region to the water‐rich southern region. Evolution of grain production distribution changes the spatial pattern of grain production and consumption, and it exacerbates water resource pressure, the gray water footprint, and greenhouse gas emissions in the area that exports grain virtual water. The gray water footprint and carbon emissions in the grain export area increased by 10.66% and 31.06% during the study period, respectively. Meanwhile, the distribution of regional grain production influences the allocation of water resources in agriculture and other industries. Due to the difference between the economic benefits created by industry and agriculture, grain virtual water flow will have effects on the regional economic development.</p>

Agricultural production is accompanied by a large amount of water consumption, nonpoint source pollution, and greenhouse gas emissions. However, the comprehensive and quantitative analysis of associated impacts on regional water, the environment, and the economy caused by variations in agricultural distribution is insufficient. This paper evaluates the evolution of grain production distribution and its effects on water resources, the economy, and the environment in China by using virtual water theory. The results show that the grain production area located in northern China is characterized by scarce water resources and a less developed economy. Due to the imbalance between grain supply and demand, virtual water embedded in grain will transfer among regions. These flows have formed a pattern where virtual water transfers from the water‐scarce northern region to the water‐rich southern region, increasing from 72.99 Gm3 in 1997 to 124.64 Gm3 in 2014. Evolution of grain production distribution changes the spatial pattern of grain production and consumption, and it exacerbates water resource pressure, the gray water footprint, and greenhouse gas emissions in the area that exports grain virtual water. The gray water footprint and carbon emissions in the grain export area increased by 10.66% and 31.06% during the study period, respectively. Meanwhile, the distribution of regional grain production influences the allocation of water resources in agriculture and other industries. Due to the difference between the economic benefits created by industry and agriculture, grain virtual water flow will have effects on the regional economic development.

The environmental impacts analysis for water transfers are lacking. In this study, the impacts on ecosystem equality and resources due to physical and virtual water transfers were evaluated for the Hetao irrigation district, China. Results indicate: about 4.50×109 m3 of water transferred from the Yellow River to the Hetao irrigation district during 2001-2010 and 2.92×109 m3 water was flowed out from this district virtually simultaneously. The impacts of physical, virtual and net water inflow on ecosystem quality were 1.33×109 m2·yr (positive), 867.60×106 m2·yr (negative) and 465.70×106 m2·yr (positive). The impacts on resources were 28.16×109 MJ (positive) for physical water, 18.26×109 MJ (negative) for virtual water and 9.89×109 MJ (positive) for net water transfer. The environmental influences were more significant for middle areas. The flows of physical and virtual water have increased water stress in some already water scare regions. The increase of physical water flow-in in this district would be difficult due to high financial cost, while the increase of virtual water flow-in could be possible measures to relieve environmental influences. However, others factors such as the social or economic factors should also be considered

In China, electricity transmission has increased rapidly over the past decades, and a large amount of virtual water is delivered from power generation provinces to load hubs. Understanding the evolution of the virtual water network embodied in electricity transmission is vital for mitigating water scarcity. However, previous studies mainly calculated the virtual water transferred in short periods in low-spatial resolution and failed to reveal driving forces of the evolution of virtual water. To solve this problem, we investigated the historical evolution of the virtual water network and virtual scarce water network embodied in interprovincial electricity transmission between 2005 and 2014. The driving forces of the evolution of virtual (scarce) water networks were analyzed at both national level and provincial level. The results show that the overall virtual water transmission and virtual scarce water transmission increased by five times, and the direction was mainly from southwest and northwest provinces to eastern provinces. Sichuan, Yunnan, and Guizhou played an increasingly important role in virtual water exporting, and northwestern provinces had dominated the virtual scarce water exporting in the decade. At the national level, the increase of virtual water is mainly driven by the change of power generation mix and power transmission. At the provincial level, the increase of virtual water transmission in the largest virtual water exporter (Sichuan) is driven by the power generation mix and the power transmission, between 2005 and 2010, and 2010 and 2014, respectively. Considering the expanding of electricity transmission, the development of hydropower in the southwestern provinces and other renewable energies (solar and wind) in the northeastern provinces would overall mitigate the water scarcity in China.

Virtual water exerts an indispensable influence on water resources, yet the existing studies on the water rights allocation of transboundary rivers hardly consider virtual water transfer (VWT). Therefore, in this paper, we used Taihu Lake as an example with data collected in 2017 that described both physical and virtual water use. We used these data to evaluate water rights allocation schemes by coupling virtual and physical water use. In order to achieve this goal, we first determined the physical water rights allocated for the four regions connected to the Basin. Next, we employed the multi-regional input–output (MRIO) approach to calculate the VWT among the four regions; then, we converted the VWT to the riparian level via the water efficiency coefficient. Finally, with virtual water included in the physical water rights allocation, we formulated a final water rights allocation for Taihu Lake. The results showed the following findings: (1) The ranking of the amount of physical water rights allocation is: Jiangsu > Zhejiang > Shanghai > Anhui. (2) Anhui and Jiangsu produce a net export of virtual water (2.259 billion m3 and 1.78 billion m3, respectively), while Zhejiang and Shanghai have a net import of virtual water (2.344 billion m3 and 1.695 billion m3, respectively), indicating that Anhui houses more water-consuming industries and is in greater need of economic restructuring. (3) The integration of virtual water makes a difference: Jiangsu achieved 16.208 billion m3 in terms of the amount of water rights allocated, Zhejiang achieved 6.606 billion m3, Shanghai achieved 3.040 billion m3, and Anhui achieved 4.319 billion m3, with a ranking of Jiangsu > Zhejiang > Anhui > Shanghai. The results detailed above prove that virtual water exerts an indispensable influence, and integrating virtual water can make the physical water rights allocation of transboundary rivers more equal and reasonable.

Rising agricultural water scarcity in China is driven by expansion of irrigated cropland in water scarce regions

Tracking flows and network dynamics of virtual water in electricity transmission across China

Virtual scarce water embodied in inter-provincial electricity transmission in China

Development of a multi-region blue/grey water management system -- Application to the Yangtze River Economic Belt

Abstract. Almost 90% of freshwater resources consumed globally are used to produce plant and animal commodities. Water-scarce countries can balance their water needs by importing food from other countries. This process, known as virtual water transfer, represents the externalization of water use. The volume and geographic reach of virtual water transfers is increasing, but little is known about how these transfers redistribute the environmental costs of agricultural production. The grey water footprint quantifies the environmental costs of virtual water transfers. The grey water footprint is calculated as the amount of water necessary to reduce nitrogen concentrations from fertilizers and pesticides released into streams and aquifers to allowed standards. We reconstructed the global network of virtual grey water transfers for the period 1986–2010 based on international trade data and grey water footprints for 309 commodities. We tracked changes in the structure of the grey water transfer network with network and inequality statistics. Pollution is increasing and is becoming more strongly concentrated in only a handful of countries. The global external grey water footprint, the pollution created by countries outside of their borders, increased 136% during the period. The extent of externalization of pollution is highly unequal between countries, and most of this inequality is due to differences in social development status. Our results demonstrate a growing globalization of pollution due to virtual water transfers.

Major US electric utility climate pledges have the potential to collectively reduce power sector emissions by one-third