Quantifying the interactions of the food-energy-water (FEW) nexus is crucial to support new policies for the conjunctive management of the three resources. Currently, our understanding of FEW systems in metropolitan regions is limited. Here, we quantify and model FEW interactions in the metropolitan area of Phoenix, Arizona, using the Water Evaluation and Planning (WEAP) platform. In this region, the FEW nexus has changed over the last thirty years due to a dramatic population growth and a sharp decline of cultivated land. We first thoroughly test the ability of WEAP to simulate water allocation to the municipal, agricultural, industrial, power plant, and Indian sectors against historical (1985–2009) data. We then apply WEAP under possible future (2010–2069) scenarios of water and energy demand and supply, as well as food production. We find that, if the current decreasing trend of agricultural water demand continues in the future, groundwater use will diminish by ~23% and this would likely result in aquifer safe-yield and reduce the energy demand for water. If agricultural activities decrease at a lower rate or a multidecadal drought occurs, additional (from 7% to 33%) water from energy-intensive sources will be needed. This will compromise the ability to reach safe-yield and increase energy demand for water up to 15%. In contrast, increasing the fraction of energy produced by solar power plants will likely guarantee safe-yield and reduce energy demand of 2%. This last solution, based on an expanded renewable portfolio and current trends of municipal and agricultural water demand, is also projected to have the most sustainable impacts on the three resources. Our analytical approach to model FEW interconnectivities quantitatively supports stakeholder engagement and could be transferable to other metropolitan regions.

Adequate access to healthy, affordable food remains a great challenge in many urban areas. Among a range of interventions, urban agriculture has been identified as an important strategy to help address urban healthy food access. While urban food production is growing in popularity, the use of potable water in traditional urban agricultural installations will exacerbate gaps in water demand and availability in water-stressed cities. This paper examines the sustainable capability of urban agriculture through an integration of alternative water resources, urban vacant land and local nutritional needs. A spatial optimization model is developed to best allocate limited resources for maximal food production to address urban food deserts. The new model is applied to test the capability of relocalized food production in Tucson, Arizona, a semi-arid region with the longest continuously farmed landscape in North America. Results highlight that urban areas with restricted water access can substantially enhance their local food production capacity in an ecologically responsible manner.

We manipulated the amount of food and water (soil moisture) available to natural populations of larval tiger beetles in Arizona. Supplemental food increased survivorship of first instars to the second instar in all species in at least one of two years. Supplemental soil moisture usually increased, but sometimes decreased, survival of first instars. Interaction of food and water treatments was significant in a few cases, but the nature of the interaction varied greatly among species and years. Significant mortality of first instars from natural enemies occurred, and may explain the anomalous cases of first—instar survival with food exclusion (since enemies were also excluded by this treatment). Food supplementation increased first—instar—to—adult survivorship for all species and third—instar—to—adult survivorship for most species; in contrast, water supplementation had no effect on most species. Food manipulation, but not water manipulation, also affected development time or size of adults (usually both) for all seven species tested. Supplemental food produced larger adults and resulted in more rapid maturation. Reduced food resulted in delayed development, and this usually resulted in death. The results of this study provide one of the few cases in which simultaneous effects of two major ecological factors have been analyzed for a large set of similar species in an array of habitats. The prevalence of food limitation and the frequent lack of a detectable consistent interaction between food availability and water availability in this system indicate that food limitation and resource competition may be the dominant factors controlling these organisms.

With continuous population increase and economic growth, challenges on securing sufficient energy, water, and food supplies are amplifying. Water plays the most important role in the energy-water-food (E-W-F) nexus issue such as energy supply (clean hydropower energy generation), water supply (drinking water), and food supply (agricultural irrigation water). Therefore, water quantity simulation & forecasting become an important issue in E-W-F nexus problem. Water quantity simulation & forecasting model, such as rainfall-runoff (RR) hydrological model has become a useful tool which can significantly improve efficiency of the hydropower energy generation, water supply management, and agricultural irrigation water utilization. The accuracy and reliability of the water quantity simulation & forecasting model are significantly affected by the model parameters. Therefore, demand of effective and fast model parameter optimization tool for solving the E-W-F nexus problem increases significantly. The shuffled complex evolution developed at University of Arizona (SCE-UA) has been recognized as an effective global model parameter optimization method for more than 20years and is highly suited to solve the E-W-F nexus problem. However, the computational efficiency of the SCE-UA dramatically deteriorates when applied to complex E-W-F nexus problem. For the purpose of solving this conundrum, a fast parallel SCE-UA was proposed in this paper. The parallel SCE-UA was implemented on the novel heterogeneous computing hardware and software systems which were constituted by the Intel multi-core CPU, NVIDIA many-core GPU, and PGI Accelerator Visual Fortran (with OpenMP and CUDA). Performance comparisons between the parallel and serial SCE-UA were carried out based on two case studies, the Griewank benchmark function optimization and a real world IHACRES RR hydrological model parameter optimization. Comparison results indicated that the parallel SCE-UA outperformed the serial one and has good application prospects for solving the water quantity simulation & forecasting model parameter calibration in the E-W-F nexus problem.

Food-energy-water (FEW) nexus governance includes the communication and collaboration among multi-level stakeholders across sectoral boundaries of the resources for decision-making. It can increase resource security and decrease unintended consequences, as compared to single-sector governance approaches. Despite these benefits, in practice, many decisions continue to be made separately from one another without cross-sector collaboration. This research integrates the theory of collaborative governance with the concept of the FEW nexus to identify and understand the barriers to this collaboration and to provide recommendations for increased collaborative FEW nexus governance. Focusing on the Phoenix, Arizona metropolitan area, a water-scarce region with a growing population, we conduct a comprehensive case study with social network analysis, participant observation, and interviews. We present the results of our analysis in three sections. First, we identify the key barriers to collaborative FEW nexus governance within four identified themes: structural asymmetries, process asymmetries, communication and coordination, and external influences. Second, we unpack how stakeholders in our study case experience these barriers. Finally, from our case study, we provide recommendations for overcoming barriers and implementing collaborative FEW nexus governance in practice, such as building trust and finding mutual benefit. We conclude that “sector mismatch,” similar to scale mismatch, is the main cause of the identified barriers and that approaches to collaborative FEW nexus governance must address this mismatch for successful engagement.

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.