water Review The Water Footprint of the United States Megan Konar 1,*,† and Landon Marston 2,† 1 Department of Civil and Environmental Engineering, University of Illinois at Urbana Champaign, Champaign IL 61801, USA 2 Department of Civil and Environmental Engineering, Virginia Tech, Blacksburg, VA 24061, USA;
[email protected] * Correspondence:
[email protected] † These authors contributed equally to this work. Received: 1 October 2020; Accepted: 18 November 2020; Published: 23 November 2020 Abstract: This paper commemorates the influence of Arjen Y. Hoekstra on water footprint research of the United States. It is part of the Special Issue “In Memory of Prof. Arjen Y. Hoekstra”. Arjen Y. Hoekstra both inspired and enabled a community of scholars to work on understanding the water footprint of the United States. He did this by comprehensively establishing the terminology and methodology that serves as the foundation for water footprint research. His work on the water footprint of humanity at the global scale highlighted the key role of a few nations in the global water footprint of production, consumption, and virtual water trade. This research inspired water scholars to focus on the United States by highlighting its key role amongst world nations. Importantly, he enabled the research of many others by making water footprint estimates freely available. We review the state of the literature on water footprints of the United States, including its water footprint of production, consumption, and virtual water flows. Additionally, we highlight metrics that have been developed to assess the vulnerability, resiliency, sustainability, and equity of sub-national water footprints and domestic virtual water flows.