Introduction:
A water footprint refers to the amount of water that is used by a person or group. The concept captures a wide variety of water uses, such as the production of agricultural products. It can also track the movement of water around the world in the form of the flow of “virtual water,” which incorporates the amount of water contained in the products and commodities that are traded between nations as well as the water it took to produce them. All of the water invested in the production of a shipment of grain, for example, is considered to be its “virtual water”. For certain water-stressed regions of the world, the export of virtual water can be a major concern.
1. For the first part of this exercise, we will graph the average water footprint for certain food products. Select Liters/kilogram in the y-axis and Food Commodities in the x-axis. Roughly how much more water is required to produce a kilogram of beef versus chicken?
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2. Assuming you live in an agricultural region that is prone to drought and has limited water supplies, which of the following commodities will put the most stress on the available water: vegetable, fruits, nuts or chicken?
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3. Find the average amount of water required for the production of vegetables, fruits, and root crops. Compare it to the average value for the highest water-demanding animal meat products (pork, lamb, and beef). How many times more water is required to produce the animal protein products compared with the plant products?
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4. In addition to the amount of water it takes to produce a commodity, another consideration is the destination of the product. Commodities are traded around the world and when they move from place to place, so does their virtual water. This movement of water can be characterized by the Virtual Water Flow between countries and can be broken down by water imports and water exports. A virtual water import is the amount of water associated with the import of a commodity that is brought into a country.
Create a bar graph showing the Water Flow in million cubic meters (million m3) on the y-axis and Top Ten Countries’ Total Imports on the x-axis. Which nation has the greatest amount of water imports?
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5. By what factor is the largest water importer greater than the second largest water importer? (Hint: Divide the larger value by the smaller value.)
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6. Now select Top Ten Countries’ Total Imports (with Exports) on the x-axis, adding another dimension to the data. Which country has the greatest difference between import and export?
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7. Which of the top ten water importing nations have even greater water exports?
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8. Now create a graph showing the Top Ten Countries’ Total Exports (with Imports) to see the countries ranked in terms of their exports rather than their imports. Of the top ten nations, which two are the largest net exporters of water? (Hint: To find the net export, subtract imports from exports.)
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9. Another means of evaluating water use is to look at the per capita water footprint. To do so, select Cubic Meters per Year per Capita (m3/year/capita) for the y-axis and Top Ten Importers’ Footprints for the x-axis. Of the top ten water-importing nations, the per capita footprint varies widely. How many times greater is the highest than the lowest footprint?
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10. In their paper entitled the “Water Footprint of Humanity” (2012), Hoekstra and Mekonnen1 state that the highest footprints are likely correlated with meat consumption, as the United States has a meat consumption rate 4.5 times greater than the global average. Why might meat consumption be a significant factor in driving up average water footprints for a population?
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1Hoekstra, A. Y. & Mekonnen, M. M. (2012). «The water footprint of humanity». Proceedings of the National Academy of Sciences, 109(9): 3232–3237.