Energyshed to Watershed: Linking Water and Energy Consumers to Their Environmental Impact and Water Resources

Abstract

Watersheds are fundamental systems for supporting the needs of society, yet the availability of water within natural watersheds often does not align with the growing demands of human activities. This disparity frequently compels cities and agricultural hubs to depend on water sources well beyond their local watersheds, facilitating water transfers that support the production of food, energy, and essential water supplies. However, the lack of detailed data on these extended water supply chains obscures the dependencies on distant watersheds, leaving many hydrological vulnerabilities unaddressed and threatening the sustainability of these water resources. This dissertation seeks to bridge this gap by identifying connections between water users and the watersheds that sustain them, while also examining the environmental impacts associated with these connections, particularly in terms of water and carbon footprints. Central to this research is the examination of how U.S. water supply systems rely on a network of watersheds, both local and distant, connected through infrastructure. A key component of this dissertation involves creating a comprehensive inventory of interbasin water transfers (IBTs), which reveals the collective contributions of multiple watersheds to societal water supply. Our comprehensive IBT datasets represent all known transfers of untreated water that cross subregions, characterizing a total of 617 IBT projects. The infrastructure-level data made available by these data products can be used to close water budgets, connect water supplies to water use, and better represent human impacts within hydrologic and ecosystem models. Additionally, the findings raise concerns about potential future water conflicts, particularly in water-stressed regions, underscoring the importance of this infrastructure-level data for improving the representation of human impacts in water management strategies and hydrologic modeling. The linkage between water sources and users also entails certain resource uses behind the scenes to ensure the supply of water at a desired quality and quantity. Water supply systems involve energy-intensive processes, while energy production, particularly in thermoelectric power plants, relies heavily on water and contributes to greenhouse gas emissions. This interdependency poses challenges in arid regions and population centers, where high water demands strain energy systems and droughts impact power production. Such challenges highlight the need for integrated water and energy management approaches. The water consumption and greenhouse gas emissions linked to electricity generation should be attributed to end users as indirect water usage and emissions. This dissertation introduces a modeling framework to estimate geographical and temporal variations in indirect water and greenhouse gas intensities associated with electricity consumption. It aligns with the U.S. Department of Energy's energyshed framework, which emphasizes linking local energy production with regional consumption to enhance resilience and reduce environmental impacts. Additionally, it highlights how the energy mix influences these intensity metrics across different regions and timeframes. By integrating the flows of virtual water embedded in electricity use with physical water flows through water supply system, this dissertation explores the role of infrastructure in supplying water to end users located in local and distant basins. These infrastructures enable the movement of both physical and virtual water, often sourced from distant watersheds, revealing the extensive dependencies of water consumers, particularly in urban areas, on remote water resources. Although virtual water transfers across basin boundaries were not classified as IBTs here due to the absence of physical infrastructure transporting the water, understanding these dependencies can aid in reducing risks in domestic water supply chains. Additionally, sustaining this water supply system results in direct and indirect emissions, which are attributed to water end users. This dissertation also maps the geographic locations of these emissions, emphasizing the environmental impact of water use through the water supply system. Looking forward, the dissertation acknowledges that future policies and climate conditions could impact water supply systems and their environmental footprints. As a case study, this dissertation examines the hydrological implications associated with the retirement of fossil fuel-fired power plants within the context of U.S. decarbonization policies. As the nation transitions to a lower-carbon energy system, water use for fossil fuel-fired electricity generation is expected to decline significantly. This reduction in water demand will likely result in increased streamflow and water availability in many U.S. rivers, providing new opportunities to reallocate water resources for the benefit of local ecosystems and water users. This comprehensive examination of the water-energy nexus provides valuable insights that are critical for policymakers, infrastructure planners, and stakeholders. Key findings from this dissertation include the identification of IBTs and their role in supporting urban and agricultural water demands, as well as highlighting potential future conflicts in water-stressed regions. The research also reveals the significant indirect water use and greenhouse gas emissions linked to electricity consumption, providing an understanding of how the energy mix affects these metrics. By utilizing the developed data products and modeling frameworks, this dissertation serves as a tool for comprehensive assessments of sectoral water and carbon footprints while linking these footprints to their supply sources. Additionally, the study shows how retiring fossil fuel power plants under decarbonization policies can lead to increased water availability, presenting new opportunities for water reallocation to support ecosystems and local water needs. By connecting water users with their sources and mapping the environmental footprints of water supply systems, the dissertation offers critical data-driven recommendations for reducing water resource and infrastructure risks. These findings are essential for ensuring sustainable and resilient water and energy management in the face of increasing demand and climate change pressures.