Agricultural Virtual Water Trade and Water Footprint of U.S. States

Abstract

Virtual water transfer in the form of trade in water-intensive crop, animal, and industrial products can constitute a substantial part of the water supply and demand balance of both importing and exporting regions. International studies have identified the United States as the leading gross and net virtual water exporter. This study quantifies water footprints and internal virtual water flows for the forty-eight contiguous states in 2008 by examining the water requirements of eighteen primary water-intensive crops and livestock. States exported 196 and imported 191 billion m3 of water. Iowa, at 14.7 billion m3, leads a collection of eleven states in the North-Central portion of the country with over 4 billion m3 of net exports. Rather than arid Southwestern states, which are collectively slight virtual water exporters, populous states bordering the Atlantic and Gulf coasts were the leading net virtual water importers, led by Florida at 10.8 billion m3. Per capita measures also reflect these general patterns. Virtual water flows are large compared to total water withdrawals, evapotranspiration from rain-fed crops, or total water footprint in nearly every state, with several Eastern states importing roughly half their water footprint and some Midwestern states exporting more virtual water than they withdraw or consume domestically.