This paper is a perspective paper, which investigates whether the water footprint (WF) concept addresses the water–food–energy–ecosystem nexus. First, the nexus links between (1) the planetary boundary freshwater resources (green and blue water resources) and (2) food security, energy security, blue water supply security and water for environmental flows/water for other ecosystem services (ES) are analysed and graphically presented. Second, the WF concept is concisely discussed. Third, with respect to the nexus, global water resources (green and blue) availability and use are discussed and graphically presented with an indication of quantities obtained from the literature. It is shown which of these water uses are represented in WF accounting. This evaluation shows that general water management and WF studies only account for the water uses agriculture, industry and domestic water. Important water uses are however generally not identified as separate entities or even included, i.e. green and blue water resources for aquaculture, wild foods, biofuels, hydroelectric cooling, hydropower, recreation/tourism, forestry (for energy and other biomass uses) and navigation. Fourth, therefore a list of essential separate components to be included within WF accounting is presented. The latter would be more coherent with the water–food–energy–ecosystem nexus and provide valuable extra information and statistics.

Natural resources are consumed in food production, and food loss is consequently accompanied with a loss of resources as well as greenhouse gas (GHG) emissions. This study analyses food loss based on India-specific production data (for the year 2013) and reported food loss rates during production and post-harvest stages of major food crops and animal products in India. Further, the study evaluates the environmental impacts of food loss in terms of utilization of water, land resources and GHG emissions. The total food loss in harvest and post-harvest stages of the food supply chain for the selected food items amounted to 58.3 ± 2.22 million tonnes (Mt) in the year 2013 with the highest losses by mass in sugarcane and rice. The volume of water associated with the food losses was found to be 115 ± 4.15 billion m³, of which 105 ± 3.77 billion m³ was direct water use (blue + green) and 9.54 ± 0.38 billion m³ was indirect water use (grey). Wasted sugarcane and rice were found to be the largest contributors for water loss. Land footprint and carbon footprint associated with food loss were found to be 9.58 ± 0.4 million hectares (Mha) and 64.1 ± 3.8 Mt CO₂eq, respectively, with rice accounting for the largest impact in both. This highlights the immediate need for quantification and taking measures for minimization of losses across the food supply chains in India.

The efficient provision of food, energy, and water (FEW) resources to cities is challenging around the world. Because of the complex interdependence of urban FEW systems, changing components of one system may lead to ripple effects on other systems. However, the inputs, intersectoral flows, stocks, and outputs of these FEW resources from the perspective of an integrated urban FEW system have not been synthetically characterized. Therefore, a standardized and specific accounting method to describe this system is needed to sustainably manage these FEW resources. Using the Detroit Metropolitan Area (DMA) as a case, this study developed such an accounting method by using material and energy flow analysis to quantify this urban FEW nexus. Our results help identify key processes for improving FEW resource efficiencies of the DMA. These include (1) optimizing the dietary habits of households to improve phosphorus use efficiency, (2) improving effluent-disposal standards for nitrogen removal to reduce nitrogen emission levels, (3) promoting adequate fertilization, and (4) enhancing the maintenance of wastewater collection pipelines. With respect to water use, better efficiency of thermoelectric power plants can help reduce water withdrawals. The method used in this study lays the ground for future urban FEW analyses and modeling.

To find a sustainable way of supplying food, energy, and water (FEW) while simultaneously protecting the ecosystem services, it is imperative to build greater understanding on interconnections, feedback, and dependencies in FEW systems. The FEW nexus has developed as a field of study to provide frameworks for such pursuits. Building upon previous work in this paper, we analyze FEW resources through the development of a virtual water trade network using the US network of food and energy flows and their associated virtual water contents. Our main objective is to provide a quantitative estimation of the virtual water embodied in the internal US food and energy transfers and analyze the associated interdependencies of these connections. Three methodological advancements demonstrate the novelty of this work. First, unlike existing FEW virtual water modeling studies, our work separates corn into both food and energy resources accounting for the significant use of corn for ethanol in the United States. Second, we apply recently published water consumption values for energy commodities confirming the variation between previous water footprint studies and these more accurate accounting procedures. Third, we examine network properties of the trade flows furthering FEW nexus literature and showcasing avenues for future research. Our results indicate that accounting for the transfer of corn from the food commodity network to the energy commodity network leads to a virtual water footprint decline of 11% for the cereal grain virtual water network. Additionally, the food trade network shows highly dense and connected properties compared to the energy trade network. Finally, our results indicate that transfers of water footprints between water scarce and water abundant states differ substantially between food and energy virtual water networks. A quantifiable understanding of the water footprint network embodied in the food and energy trade can help in developing policies for promoting conservation and efficiency in the context of the FEW nexus.

Freshwater use for food production is projected to increase substantially in the coming decades with population growth, changing demographics, and shifting diets. Ensuring joint food-water security has prompted efforts to quantify freshwater use for different food products and production methods. However, few analyses quantify freshwater use for seafood production, and those that do use inconsistent water accounting. This inhibits water use comparisons among seafood products or between seafood and agricultural/livestock products. This 'seafood gap' in the food-water nexus literature will become increasingly problematic as seafood consumption is growing globally and aquaculture is one of the fastest growing animal food sectors in the world. Therefore, the present study 1) reviews freshwater use concepts as they relate to seafood production; 2) provides three case studies to highlight the particular water use concerns for aquaculture, and; 3) outlines future directions to integrate seafood into the broader food-water nexus discussion. By revisiting water use concepts through a focus on seafood production systems, we highlight the key water use processes that should be considered for seafood production and offer a fresh perspective on the analysis of freshwater use in food systems more broadly | Jessica A. Gephart et al., 'The `seafood gap' in the food-water nexus literature?issues surrounding freshwater use in seafood production chains', Advances in Water Resources, vol. 110, pp.505-514, Elsevier BV, 2018

Freshwater use for food production is projected to increase substantially in the coming decades with population growth, changing demographics, and shifting diets. Ensuring joint food-water security has prompted efforts to quantify freshwater use for different food products and production methods. However, few analyses quantify freshwater use for seafood production, and those that do use inconsistent water accounting. This inhibits water use comparisons among seafood products or between seafood and agricultural/livestock products. This ‘seafood gap’ in the food-water nexus literature will become increasingly problematic as seafood consumption is growing globally and aquaculture is one of the fastest growing animal food sectors in the world. Therefore, the present study 1) reviews freshwater use concepts as they relate to seafood production; 2) provides three cases to highlight the particular water use concerns for aquaculture, and; 3) outlines future directions to integrate seafood into the broader food-water nexus discussion. By revisiting water use concepts through a focus on seafood production systems, we highlight the key water use processes that should be considered for seafood production and offer a fresh perspective on the analysis of freshwater use in food systems more broadly.

Water scaricity is an increasingly critical issue for food production around the world. This is particularly true for the world's poorest region, Sub-Saharan Africa, due to its growing malnutrition and almost complete dependence on rainfed agriculture. Given that agriculture is the primary consumer of freshwater around the globe and the demand for domestic, industrial, and environment water uses is steadily rising, strategies for the sustainable use of water in agriculture are urgently needed | Sulser Timothy B. et al., 'How can African agriculture adapt to climate change: Green and Blue Water Accounting in the Limpopo and Nile Basins Implications for Food and Agricultural Policy', , IFPRI, 2011