Integration of the food, energy, and water (FEW) nexus thinking is expected to enhance cross-sectoral discussion during the process of policy development. This process can be improved with comprehensive assessment tools to provide quantitative information regarding the interdependence of the FEW nexus. A comprehensive framework of the regional FEW nexus quantitative assessment was proposed in this study. Life cycle assessment (LCA) was the core method used to evaluate the FEW inter-linkages. Land use data which can further imply the resources consumption or requirement was introduced to estimate potential changes in the nexus in future time periods. In order to display the practicality of the FEW nexus approach, a user-friendly nexus platform, a GIS-based Regional Environmental Assessment Tool for Food-Energy-Water nexus (GREAT for FEW) (http://greatforfew.enve.ntu.edu.tw/FEW/), was developed with a solid conceptual model, a database, and calculation methods. The usability of the tool was demonstrated using a Taiwanese case study. The results of the Taiwanese case showed that Scenario 1 (non-nuclear homeland policy) caused the lowest environmental impacts as compared to both Scenario 0 (baseline) and Scenario 2 (non-nuclear homeland policy with National Spatial Plan) due to better energy structures and maintenance of agricultural lands. These outcomes indicate that the selection of indicators does affect the results. Therefore, it is suggested that additional indicators should be designed based on the characteristics of the case study area and concerns of stakeholders.

This research develops a bottom-up procedure to assess the potential of food-energy-water (FEW) systems on the rooftops of buildings in an urban district in Spain considering the urban morphology of the built environment and obtains accurate assessments of production and developmental patterns. A multicriteria decision-making technique implemented in a geographical information system (GIS) environment was used to extract suitable rooftop areas. To implement this method, the slope (tilt), aspect (azimuth), shading, and solar radiation of the rooftops were calculated using LiDAR (Light Detection and Ranging) data and building footprints. The potential of FEW system implementation was analysed at the building and morphology levels. The results showed several differences between residential and non-residential urban morphologies. Industrial areas contained the highest productivity for FEW systems. The production was 2.51 kg of tomatoes/m², 48 kWh of photovoltaic energy/m², and 0.16 l of rainwater/m². Regarding the residential urban morphologies, the more compact tents resulted in better performance. Among the FEW systems, although water could best benefit from the features of the entire roof surface, the best production results were achieved by energy. The food system is less efficient in the built environment since it requires flat roofs. The methodology presented can be applied in any city, and it is considered optimal in the European context for the development of self-production strategies for urban environments.

The concentration on producing clean energy such as biofuels in recent years has had an impact on some of the natural resources that humans use, such as water, food, and land. In this paper, a two-phase approach to design and optimize a biofuel supply chain based on Jatropha Curcas L. oil and used cooking oil (UCO) is presented by considering the nexus between energy, water, food, waste, and land (EWFWL) in order to protect natural resources and create environmental security. In the first phase, the most appropriate sites for Jatropha cultivation are determined by considering the accessibility, geological, environmental and climatic criteria, using the Geographic Information System (GIS). In the second phase, a novel multi-objective model is designed considering the EWFWL nexus and solved using the Torabi-Hassini method. The model is validated using real data from Fars province, Iran, as well as a sensitivity analysis. In this study, some of main contributions are identifying suitable Jatropha cultivation sites in Fars province, Iran; development an innovative optimization model regarding EWFWL nexus; and considering financial parameters and global distribution along with EWFWL nexus. According to the results, the sale of biofuel to local and foreign consumers accounts for the largest proportion of network revenues, contributing for 59.25% of total revenue. Furthermore, increasing the use of UCOs for biofuel production will reduce Jatropha output, and consequently reduce water, land use, and increase food security. If UCO shortage occurs, more lands will be dedicated to Jatropha farms and food-loss and water consumption increase. By focusing on biofuel production over UCO, policymakers can produce less Jatropha and decrease the use of land for Jatropha cultivation. Furthermore, effluent-based irrigation can be more widely used to save fresh water by irrigating Jatropha farms.

Of all the challenges facing the sustainability of cities, water, food and energy are the most critical. In the context of rapid urbanization, unsustainable human activities have resulted in fundamental changes in the structure and function of land cover and urban water systems, and the degradation of ecosystem services. Taking Beijing - a typical fast-growing mega city - as an example, to establish a food-energy-water impact model, this research studied the temporal-spatial changes in the water system pattern in a mega city, along with the driving forces, especially the nexus to rice production and energy, and the ensuing series of environmental impacts.On the basis of land use data, remote sensing images, and thematic maps from 1993, 2001 and 2007, water system information was extracted and adjusted for Beijing. With the aid of RS and GIS techniques, the water system was classified into four types, and the spatial and temporal dynamic of the landscape patterns of Beijing’s water system systematically was analyzed. The landscape metrics were then calculated using FRAGSTATS 3.3. The results show that the total area of water system in Beijing declined from 63,494 ha to 43,652 ha from 1993 to 2007. The decrease of the linear water surface is more significant than that of the non-linear water surface. In the terms of landscape metrics change, the number of patches has decreased from 5510 to 5396. The density indexes have increased by 40.61%, the average area of patches has decreased by 30.18%, the patch shape has tended to become more regular, and the overall pattern of the water system is becoming more fragmented. Urban sprawl, the shortage of water resources, and the increasing amount of construction land are the major reasons accounting for the changes in the water system in Beijing. Because of these changes, farmland has decreased by 212,428 ha, and especially rice paddy fields, are significantly decreasing from 52,200 ha in 1980 to 199.6 ha in 2015, a decrease of 99.62%. Consequently, rice production is decreasing by 99.61%, more energy is being consumed for food production. Meanwhile, the local water supply rate has decreased from 100% to 78.4% between 2001 to 2016, the underground water level has decreased by 14.24 m from 1994 to 2016. There is more competition for water resources, more urban water flooding disasters, and emerging urban environmental problems such as declining underground water level, posing a serious threat to the sustainability of the city. Therefore, a systematic and smart thinking is needed to analyze the complex land use - water- food – energy relationship.

The global demand for resources such as energy, land, or water is constantly increasing. It is therefore not surprising that research on the Food-Energy-Water (FEW) nexus has become a scientific as well as a general focus in recent years. A significant increase in publications since 2015 can be observed, and it can be expected that this trend will continue. A multilevel (macro, meso, and micro) perspective is essential, as the FEW nexus has cross-sectoral interdependencies. Several review studies on the FEW nexus can be found in the literature, in general, it can be concluded that the FEW nexus is a multi-disciplinary and complex topic. The studies examined identify essential fields of action for research, policy, and society. However, questions such as what are the main research fields at each level? Is it possible to divide the research into specific clusters? and do the clusters correlate with the levels, and what are the methods of modeling used in the clusters and levels? are still not fully discussed in the literature. An extensive literature review was conducted to get insight into the existing research areas. Especially in such fields as the FEW nexus, the amount of literature can get huge, and a human could get lost analyzing the literature manually. For that, we created word clouds and performed a cluster- and network-analysis to support the selection of most relevant papers for a detailed reading. In 2021, the most publications were published, with 173 publications, which corresponds to a share of 26.6 %. There has been a significant increase since 2015, and it can be expected that this trend will continue in the coming years. Most of the first authors come from the USA (25.4 %), followed by China with 22.4 %. From the word cloud and the top 20 words, which appear in the title and abstract, it can be deduced that the topic water is the most represented. However, the terms system, resource, model, study, change, development, and management also appear to be very important, which indicates the importance of a holistic approach to the topic. In total 9 clusters could be identified at the different levels. It can be seen that three clusters form well. For the others, a rather diffuse picture can be observed. In order to find out which topics are hidden behind the individual clusters, 6 publications from each cluster were subjected to a more detailed examination. With these steps, a number of 54 publications were identified for detailed consideration. The modeling approaches that are currently being applied in research can be classified into domain-specific tools (e. g. global water models, crop models or global climate models) and into more general tools to perform for example a life cycle analysis, spatial analysis using geographic information system, or system dynamics for a general understanding of the links between the domains. With the domain-specific tools, detailed research questions can be addressed to answer questions for a specific domain. However, these tools have the disadvantage that especially the links between the sectors food, energy, and water are not fully considered. Many implementations that are made today are at lowest level (micro) relate to bounded spatial areas and are derived from macro and meso level goals.

The feasibility of a hydrogeological modeling approach to simulate several thousand shallow groundwater-fed lakes and wetlands without explicitly considering their connection with groundwater is investigated at the regional scale (~40,000 km²) through an application in the semi-arid Nebraska Sand Hills (NSH), USA. Hydraulic heads are compared to local land-surface elevations from a digital elevation model (DEM) within a geographic information system to assess locations of lakes and wetlands. The water bodies are inferred where hydraulic heads exceed, or are above a certain depth below, the land surface. Numbers of lakes and/or wetlands are determined via image cluster analysis applied to the same 30-m grid as the DEM after interpolating both simulated and estimated heads. The regional water-table map was used for groundwater model calibration, considering MODIS-based net groundwater recharge data. Resulting values of simulated total baseflow to interior streams are within 1% of observed values. Locations, areas, and numbers of simulated lakes and wetlands are compared with Landsat 2005 survey data and with areas of lakes from a 1979–1980 Landsat survey and the National Hydrography Dataset. This simplified process-based modeling approach avoids the need for field-based morphology or water-budget data from individual lakes or wetlands, or determination of lake-groundwater exchanges, yet it reproduces observed lake-wetland characteristics at regional groundwater management scales. A better understanding of the NSH hydrogeology is attained, and the approach shows promise for use in simulations of groundwater-fed lake and wetland characteristics in other large groundwater systems.