Visualizing System and Technology Trade-offs in the Water–Energy Nexus

Many systems have interconnected relationships, including those that consume energy to produce water and those that consume water to produce energy. These interconnections constitute the water–energy nexus, aspects of which have been the subject of recent study. Several visualizations of the water–energy nexus are available; however, many do not readily portray trade-offs between different water–energy technologies. In this Perspective, we present several visualizations and/or approaches that can help decision-makers better understand nexus trade-offs. First, a quadrant graph with water produced/consumed (x-axis) and energy produced/consumed (y-axis) shows how fossil fuel and renewable energies are related to one another within the nexus. Among other observations, the graph specifically highlights the current absence of systems that produce both water and energy. As emerging technologies such as anaerobic wastewater treatment become more prevalent, stakeholders can use the quadrant graph to examine how each compares to existing water–energy technologies. Finally, complementary to the quadrant graph, a figure presenting the normalization of energy produced to water consumed highlights the dominance of wind power over other technologies and how evaporative losses impact hydropower. Each of these visualizations and/or approaches can help decision-makers and stakeholders make improved decisions regarding the use of technologies within the water–energy nexus.