February 28, 2012 | vol. 109 | no. 9 | Arjen Y. Hoekstra and Mesfin M. Mekonnen
This study quantifies and maps the water footprint (WF) of humanity at a high spatial resolution, focusing on consumptive use of rainwater (green WF), ground and surface water (blue WF), and polluted water (gray WF). The global annual average WF from 1996 to 2005 was 9,087 Gm³/y, with 74% being green, 11% blue, and 15% gray. Agricultural production contributed 92% of the total WF. About one-fifth of the global WF is related to export production. The total volume of international virtual water flows related to trade in agricultural and industrial products was 2,320 Gm³/y, with 68% green, 13% blue, and 19% gray. The average consumer's WF was 1,385 m³/y, with the United States having the highest at 2,842 m³/y, followed by China and India at 1,071 and 1,089 m³/y, respectively. Consumption of cereal products contributed the largest share (27%), followed by meat (22%) and milk products (7%). The study highlights the global dimension of water consumption and pollution, showing that many countries heavily rely on foreign water resources and have significant impacts on water consumption and pollution elsewhere.This study quantifies and maps the water footprint (WF) of humanity at a high spatial resolution, focusing on consumptive use of rainwater (green WF), ground and surface water (blue WF), and polluted water (gray WF). The global annual average WF from 1996 to 2005 was 9,087 Gm³/y, with 74% being green, 11% blue, and 15% gray. Agricultural production contributed 92% of the total WF. About one-fifth of the global WF is related to export production. The total volume of international virtual water flows related to trade in agricultural and industrial products was 2,320 Gm³/y, with 68% green, 13% blue, and 19% gray. The average consumer's WF was 1,385 m³/y, with the United States having the highest at 2,842 m³/y, followed by China and India at 1,071 and 1,089 m³/y, respectively. Consumption of cereal products contributed the largest share (27%), followed by meat (22%) and milk products (7%). The study highlights the global dimension of water consumption and pollution, showing that many countries heavily rely on foreign water resources and have significant impacts on water consumption and pollution elsewhere.