This paper focuses on a collection of methods that can be used to analyze the water-energy-food (WEF) nexus. We classify these methods as qualitative or quantitative for interdisciplinary and transdisciplinary research approaches. The methods for interdisciplinary research approaches can be used to unify a collection of related variables, visualize the research problem, evaluate the issue, and simulate the system of interest. Qualitative methods are generally used to describe the nexus in the region of interest, and include primary research methods such as Questionnaire Surveys, as well as secondary research methods such as Ontology Engineering and Integrated Maps. Quantitative methods for examining the nexus include Physical Models, Benefit-Cost Analysis (BCA), Integrated Indices, and Optimization Management Models. The authors discuss each of these methods in the following sections, along with accompanying case studies from research sites in Japan and the Philippines. Although the case studies are specific to two regions, these methods could be applicable to other areas, with appropriate calibration.

Studies on the food, energy, and water (FEW) nexus lay a shared foundation for researchers, policy makers, practitioners, and stakeholders to understand and manage linked production, utilization, and security of FEW systems. The FEW nexus paradigm provides the water community specific channels to move forward in interdisciplinary research where integrated water resources management (IWRM) has fallen short. Here, we help water researchers identify, articulate, utilize, and extend our disciplinary strengths within the broader FEW communities, while informing scientists in the food and energy domains about our unique skillset. This paper explores the relevance of existing and ongoing scholarship within the water community, as well as current research needs, for understanding FEW processes and systems and implementing FEW solutions through innovations in technologies, infrastructures, and policies. Following the historical efforts in IWRM, hydrologists, water resources engineers, economists, and policy analysts are provided opportunities for interdisciplinary studies among themselves and in collaboration with energy and food communities, united by a common path to achieve sustainability development goals.

A review was conducted to understand the current status of the water–energy–food nexus, focusing on its methodology, and the process through which the nexus approach has academically and geographically expanded across and synthesized more than one discourse, discipline, and domain via its methodology as interdisciplinary and integrated approaches. The review article types were categorized into five groups and comprehensively analyzed. Various indicators to assess the nexus methods and tools, reported in previous studies, that can be used to select appropriate methods and tools for methodology and research designs. The studies in the reviewed articles were characterized by various stages of interdisciplinary research. In addition, the water–energy–food nexus initiatives, which generalize methods and tools, applying mixed methods to the replicability of specific case studies, were discussed based on the findings.

The water–energy–food (WEF) nexus has emerged as a frontier issue in interdisciplinary research and is one of the most complex sustainability challenges that the world is faced with today. In this review, we ask: (i) how can the interdependent relationships among water, energy, and food resources be identified? (ii) what methods have been applied to understand these relationships? and (iii) what are the future opportunities and challenges for the WEF nexus development? To answer these questions, we provide a critical assessment of the relevant literature from Web of Science database on WEF nexus published between 2008 and 2019 using a bibliometric analysis. Using the resulting 396 published articles, we systematically reviewed the concept and the bibliometric characteristics of the WEF nexus research to assess the development footprint. Based on the most popular topics and research methods found in these publications, we discussed the major research limitations as well as future opportunities and challenges for WEF research. An examination of internal and external relationships among topics showed that the three most recent hot areas of WEF nexus research include (i) water, energy, and food, (ii) policy-making and resource management, and (iii) system models and methods. Specifically, considering that no one method can solve all problems, we innovatively summarized the application scope and the advantages and disadvantages of each method, with a particular focus on the WEF nexus models. This was undertaken to support readers in choosing a scientific method to analyze the specific WEF nexus related issues. We anticipate that complex interdependence mechanisms, data uncertainty, analytical model development, and in-depth policy implementation will pose the greatest challenges for future WEF nexus research; however, these challenges will also generate better research opportunities. This bibliometric review highlights that to increase understanding of complex WEF systems and formulating optimal strategies to manage them is of great significance for environmental and social sustainability.