Researchers: A.K. Chapagain, A.Y. Hoekstra and H.H.G. Savenije

Organisations involved: UNESCO-IHE, University of Twente and Delft University of Technology

Backgrounds

Many nations save domestic water resources by importing water-intensive products and exporting commodities that are less water intensive. National water saving through the import of a product can imply saving water at a global level if the flow is from sites with relatively high water productivity (i.e. commodities with a low virtual water content) to sites with low water productivity (commodities with a high virtual water content).

Objectives

The purpose of this study is to analyse the consequences of international virtual water flows on the global and national water budgets. With this aim, it quantifies and assesses national and global water savings and losses per agricultural product (crop, livestock) and per country during the period 1997-2001.

Results

The assessment shows that the total amount of water that would have been required in the importing countries if all imported agricultural products would have been produced domestically is 1605 Gm3/yr. These products are however being produced with only 1253 Gm3/yr in the exporting countries, saving global water resources by 352 Gm3/yr. This saving is 28 per cent of the international virtual water flows related to the trade of agricultural products and 6 per cent of the global water use in agriculture. National policy makers are however not interested in global water savings but in the status of national water resources. Egypt imports wheat and in doing so saves 3.6 Gm3/yr of its national water resources. Water use for producing export commodities can be beneficial, as for instance in Cote d’Ivoire, Ghana and Brazil, where the use of green water resources (mainly through rain-fed agriculture) for the production of stimulant crops for export has a positive economic impact on the national economy. However, export of 28 Gm3/yr of national water from Thailand related to rice export is at the cost of additional pressure on its blue water resources. Importing a product which has a relatively high ratio of green to blue virtual water content saves global blue water resources that generally have a higher opportunity cost than green water.

National water savings related to international trade of agricultural products.

Publications

2008

Hoekstra, A.Y. and Chapagain, A.K. (2008) Globalization of water: Sharing the planet's freshwater resources, Blackwell Publishing, Oxford, UK.

2006

Chapagain, A.K., Hoekstra, A.Y., and Savenije, H.H.G. (2006) Water saving through international trade of agricultural products, Hydrology and Earth System Sciences 10(3): 455-468.

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