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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. 

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 

It is useful to model the interactions between the water and energy models separately. A coupled water and energy model using an interaction model lends itself to developing flexible, yet rigorous predictive simulation studies. A WEAP-LEAP interaction model is developed based on the Knowledge Interchange Broker modeling approach. A RESTful simulation framework is developed for coupling the Componentized-WEAP and Componentized-LEAP systems. Every interaction model is defined to have a set of modules where each module has its input and output ports with data transformation schemes. The input and output ports of the Componentized-WEAP and Componentized-LEAP models are coupled with those of the interaction model. A cyclic, synchronous execution protocol is defined for concurrent, bidirectional data transformations. The computational efficiency of this loosely coupled water-energy framework is acceptable compared with the tightly WEAP-LEAP system. This proposed framework shows understanding the water-energy system nexus is advantageous using interaction modeling. 

For systems-of-systems, the use of different modeling methods is important not only because each system can be described more correctly, but also benefit from tools that are in use by different communities. Using an opaque or closed source-code tool with others, however, is challenging. Consequently, to facilitate the development of simulations for systems-of-systems it is useful to cast closed-source models in a flexible component-based framework. Using this concept, a RESTful web service framework is developed for the Water Evaluation And Planning (WEAP) software system. The WEAP RESTful framework has a suite of model components for all the model entities defined in the WEAP system. An example water system model shows the computational cost for the web-service framework is negligible. Casting the model entities to components can play a key role in using the WEAP system with other modeling frameworks useful for simulating the complexities of the Food-Energy-Water systems. 

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. 

Rapid growth in the food-energy-water (FEW) nexus literature calls for an assessment of the trajectory and impacts of this scholarship to identify key themes and future research directions. In this paper, we report on a bibliometric analysis of this literature that focuses on (1) examining publication trends and geographic focus of research, (2) identifying research hotspots and emerging themes, (3) assessing the integrated nature of research, and (4) reflecting on major developments and ways forward. We used Elsevier’s SCOPUS database to search for publications from January 2011 to May 2018 on the FEW nexus, and analyzed the final sample of 257 publications using BibExcel and Vosviewer software tools. The analysis showed steady growth in publications since 2011 with a sharp upturn in 2015 and 2016, coinciding with major funding calls. Thematic analysis of abstracts revealed a strong focus on quantitative resource interlinkages with limited attention to qualitative institutional capacities and intersectoral governance challenges. Term co-occurrence network map showed the term “investment” connected with a large number of frequently cited terms, while the term “governance” demonstrated much weaker links. We reflect on how these findings may help us better understand and address the enduring challenge of transitioning from nexus thinking to action.