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Water, energy, and food are all essential components of human societies. Collectively, their respective resource systems are interconnected in what is called the “nexus”. There is growing consensus that a holistic understanding of the interdependencies and trade-offs between these sectors and other related systems is critical to solving many of the global challenges they present. While nexus research has grown exponentially since 2011, there is no unified, overarching approach, and the implementation of concepts remains hampered by the lack of clear case studies. Here, we present the results of a collaborative thought exercise involving 75 scientists and summarize them into 10 key recommendations covering: the most critical nexus issues of today, emerging themes, and where future efforts should be directed. We conclude that a nexus community of practice to promote open communication among researchers, to maintain and share standardized datasets, and to develop applied case studies will facilitate transparent comparisons of models and encourage the adoption of nexus approaches in practice. 

Food-energy-water nexus governance has been promoted as an approach to integrate the management and policy of the three sectors together for coordinated governance. However, there are limited approaches to evaluate, assess, or measure the governance of the food-energy-water nexus. Assessment of the governance process is important to move the concept from conceptualization toward implementation and to understand the specific potential and limits of the nexus governance process. Therefore, this study presents a theoretical framework and associated indicator set to assess urban collaborative food-energy-water nexus governance in practice. This theoretical framework is then applied to two example cases: Phoenix, Arizona, USA and Cape Town, South Africa. The implementation of this framework provides recommended factors needed for improved collaborative FEW nexus governance in cities. These cases showcase the utility of this framework in assessing urban collaborative food-energy-water nexus governance. 

It is beneficial to combine simulation models via I/O data exchanges. The Knowledge Interchange Broker (KIB) modeling approach can be used to develop interaction models that also have time, state, operations, and concurrency. A unique advantage of the interaction model is the composed models can have their own specifications. The KIB is used to model the nexus of the water and energy models of city metropolises. The RESTful WEAP, LEAP, and DEVS-Suite are used to model and simulate the composition of hybrid water, nexus, and energy models. The performance measurements of the simulations of these integrated simulators are evaluated. The results show the DEVS and Algorithmic interaction models have nearly identical computational times. These simulation times are contrasted with the use of links that share data between WEAP and LEAP models. This research highlights the interaction model flexibility and visibility at almost twice the computational time cost for data sharing. 

Increased usage and non-efficient management of limited resources has created the risk of water resource scarcity. Due to climate change, urbanization, and lack of effective water resource management, countries like Pakistan are facing difficulties coping with the increasing water demand. Rapid urbanization and non-resilient infrastructures are the key barriers in sustainable urban water resource management. Therefore, there is an urgent need to address the challenges of urban water management through effective means. We propose a workflow for the modeling and simulation of sustainable urban water resource management and develop an integrated framework for the evaluation and planning of water resources in a typical urban setting. The proposed framework uses the Water Evaluation and Planning system to evaluate current and future water demand and the supply gap. Our simulation scenarios demonstrate that the demand–supply gap can effectively be dealt with by dynamic resource allocation, in the presence of assumptions, for example, those related to population and demand variation with the change of weather, and thus work as a tool for informed decisions for supply management. In the first scenario, 23% yearly water demand is reduced, while in the second scenario, no unmet demand is observed due to the 21% increase in supply delivered. Similarly, the overall demand is fulfilled through 23% decrease in water demand using water conservation. Demand-side management not only reduces the water usage in demand sites but also helps to save money, and preserve the environment. Our framework coupled with a visualization dashboard deployed in the water resource management department of a metropolitan area can assist in water planning and effective governance. 

Despite the known benefits of integrated policy and planning, traditional governance decisions in the food-energy-water (FEW) nexus are often made without cross-sector collaboration, potentially leading to unintended consequences and decreased resource security. Applying collaborative governance approaches to the FEW nexus provides an opportunity to shift towards integrated policy of food, energy, and water governance; doing so first requires an understanding of the limitations of current governance structures and the opportunities for change. We conduct a social network analysis of stakeholders in Phoenix, AZ using secondary data sources to construct the social network of collaboration and to analyze the ability of the governance landscape to facilitate or hinder collaborative governance. The social network measures indicate potential challenges to collaborative governance of FEW nexus stakeholders, such as limited trust between actors. However, leveraging bridging actors provides opportunities to increase collaborative governance between sectors. This research is important for implementing collaborative FEW nexus governance in practice. 

Phoenix, an Active Management Area in the desert Southwest US, is the 5th most populated city in the US. Scarce local groundwater and water transported from external resources must be managed in the presence of different types of energy sources. Local and regional decision-makers are faced with answering challenging questions on managing water, energy supply, and demand over a few years to several decades. Prediction and planning for the interdependency of these entities can benefit from modeling the water and energy systems as well as their interactions with one another. In this paper, the integrated WEAP and LEAP tools and a modeling framework that externalizes their hidden linkage to an interaction model are described and compared using the Phoenix AMA. Loose coupling enabled by interaction modeling is a key for decision-policies that should be grounded at the nexus of the water-energy system of systems