Virtual water

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Estimated consumption of virtual water for
various agricultural products
(m³ water / ton of product = l / kg) According to various authors
Hoekstra
& Hung
(2003)
Chapagain
& Hoekstra
(2003)
Zimmer
& Renault
(2003)
Oki
et al.
(2003)
average
beef 15977 13500 20700 16726
pork meat 5906 4600 5900 5469
cheese 5288 5288
Chicken 2828 4100 4500 3809
Eggs 4657 2700 3200 3519
rice 2656 1400 3600 2552
Soybeans 2300 2750 2500 2517
wheat 1150 1160 2000 1437
Corn 450 710 1900 1020
milk 865 790 560 738
Potatoes 160 105 133

Virtual or latent water describes the amount of water that was actually used to manufacture a product.

A distinction is made between:

  • green virtual water from precipitation and natural soil moisture
  • blue virtual water for artificial irrigation
  • gray virtual water is impaired during use (fertilizers, pesticides, industrial waste) and can only be reused to a limited extent

According to this balance, around 4,000–5,000 liters of water are used per inhabitant per day in Germany, for example 32 liters for the production of a microchip and 15,000 liters for the production of one kilogram of beef . At first glance, water consumption is also taken into account : when producing beef, not only the use of drinking water for the animals must be taken into account, but also the natural precipitation and irrigation for fields and meadows that provide the feed for the animals .

The term was coined around 1995 by the English geographer John Anthony Allan (* 1937). In 2008 he received the Stockholm Water Prize from the Stockholm International Water Institute for his work .

Balancing of the virtual water

The studies are aimed at a more economical use of water in regions with water shortages. In particular, it should be made transparent that water-intensive and export-oriented agricultural use in arid regions of the world is ecologically senseless and economically comparatively unprofitable. Water-poor countries can conserve their own water resources by importing goods that require a lot of water to produce.

The calculation of the virtual water also makes it possible to investigate the international transfer of water bound in products. Germany exports virtual water that is used in industrial production and imports virtual water primarily in agricultural products (including cotton , which is particularly water-consuming ). In an international comparison, Germany is one of the ten largest importers of virtual water.

The Switzerland imports more than it exports virtual water. The bottom line is the amount of Lake Thun every day .

The UNESCO-IHE ( Institute for Water Education of the United Nations Organization for Education, Science and Culture) is primarily concerned with accounting for virtual water . Among other things, the institute published these consumption quantities of virtual water:

amount example Water requirement in liters
1 rose 5
1 cup tea 35
0.25 L beer 75 (to)
1 cup coffee 140
1 L milk 1000
1 kg paper 750 (approx.)
500 sheets A4 paper 5000 or 1 sheet up to 10 l
approx. 2 g Microchip 32
1 kg Corn 900
1 kg wheat 1100 (approx.)
1 kg Soybeans 1800
1 Cotton - T-Shirt 2000 (approx.)
1 kg coconuts 2500
1 kg Chicken eggs 4500 (approx.)
1 kg rice 3000-5000 (approx.)
1 Jeans 6000
1 kg beef 15,500 (approx.)
1 kg Almonds 13,000
1 Car 20,000 - 300,000
0000

Diagram of logarithmic representation of the virtual water consumption for various everyday items.jpg

Influence of production and environmental factors using the example of beef

According to UNESCO-IHE (Mekonnen / Hoekstra, 2010), the amount of virtual water required, especially for meat, is heavily dependent on production and environmental factors.

For example, 15,415 liters of virtual water are required on average worldwide to produce 1 kg of beef. Of this, 14,414 liters (93.5%) are rainwater ("green water") that falls on the forage areas. The rest is divided into water for irrigation ("blue water") and other water e.g. B. for watering, cleaning and processing ("gray water").

The amount of virtual water varies from 10,244 liters (8,849 liters of which are "green water") in intensive farming . With extensive grazing , the virtual load is up to 21,829 liters (21,121 liters of which are "green water").

In a worldwide comparison, the lowest amount of virtual water is required for beef from intensive farming in the USA with 3,856 liters (of which 2,949 liters of "green water"), the highest amount for beef from pasture farming in Ethiopia with 100,967 liters (of which 77,013 liters of "green water") ).

For beef from intensive farming in Germany, 5,991 liters (of which 5,014 liters "green water") are required per kilogram, for beef from extensive pasture farming 12,229 liters (of which 11,083 liters "green water").

Water footprint

The English term water footprint , which can be translated as footprint of water consumption , comprises the total amount of water that is required for the production of goods and services. A distinction is made between blue, green and gray water: The blue footprint refers to the groundwater and surface water, which is directly evaporated during production. The green footprint describes the amount of water that evaporates through the vegetation itself and is therefore particularly important in agriculture. The gray footprint includes the amount of water that is contaminated by production processes. The Water Footprint Network , which also works with the UN , deals with these questions .

The water footprint of a country relates to the total population of a country. One also speaks of the water trail or the water consumption index of a country. Examples of water footprints from different countries in m³ per capita and year:

  • China's water consumption index is around 700 m³; 7% of this is imported via goods.
  • In Germany this index is 1,545 m³. The causes lie in the high consumption of industrial products and meat: Their hidden water imports clearly exceed the export of virtual water: 106 parts of imported water are compared to 70 parts of exported water.
  • 82 percent of Switzerland's water footprint is created outside the country and often in regions where water resources are scarce . The water consumption index is around 1,500 m³.
  • Japan's water footprint is 1,150 m³; 65% of this is already being used outside the country.
  • The USA's water consumption index is 2,483 m³.
  • The global average of the index is 1,385 m³ per person per year.
country Footprint
China 700 m³ 7% through import
Japan 1,150 m³
Switzerland 1,500 m³ 82% through import
Germany 1,545 m³
United States 2,483 m³
Average worldwide 1,385 m³

Environmental policy

Water-poor countries can conserve their own water resources through the targeted import of goods whose production requires a lot of water. Conversely, water-rich countries can help the water-poor countries by not importing any products from them that need a lot of water.

criticism

Important points of criticism of the concept of "virtual water" are:

  • Often no distinction is made between whether the water falls naturally as rain or whether it is artificially extracted from lakes, rivers or groundwater wells. If rainwater is used directly, this usually does not lead to shifts in the water balance of the landscape. However, if water is pumped for agriculture, this can lead to a lowering of the groundwater level, which in turn causes consequential damage. For example, one kilogram of beef accounts for around 15,000 liters of water, but a very large part of it is rain, which falls anyway and is sufficient for growing the feed. Almond trees , on the other hand, are often artificially irrigated to increase yield, although they are actually used to dry climates. This leads to a virtual water consumption of around 13,000 liters per kilogram of almonds.
  • The concept easily leads to the assumption that water that is saved in one place is released in the same place for less water-intensive uses. However, this is often not feasible for both practical and economic reasons. For example, the soil in a poor, dry area is not suitable for arable farming, but less efficient goat husbandry is possible on it, and thus represents the best possible land use for the farmer.
  • The concept does not consider whether water use actually harms local ecosystems. In monsoon areas, for example, huge amounts of water can be directed onto the rice fields without it being missing elsewhere. Likewise, the amounts of rainwater that are necessary for wood to grow do not have to be taken into account.

literature

  • Arjen Y. Hoekstra, Ashok K. Chapagain: Water Footprints of Nations . Water Use by People as a Function of Their Consumption Pattern. In: Water Resources Management . 2006, doi : 10.1007 / s11269-006-9039-X ( PDF ).
  • Günter Matzke-Hajek : Virtual water - less water in the shopping basket . Association of German Water Protection V. (VDG), Bonn 2011, ISBN 978-3-937579-34-4 .
  • Diana Hummel, Thomas Kluge , Stefan Liehr, Miriam Hachelaf: Virtual Water Trade . Documentation of an International Expert Workshop. July 3-4, 2006. ( PDF ).
  • Fred Pearce : When the rivers dry up . Kunstmann , Munich 2007, ISBN 978-3-88897-471-7 (Original title: When the Rivers Run Dry . Translated by Gabriele Gockel, Barbara Steckhan, About the water crisis and its effects, 400 pages).
  • Wolfgang Sachs, Tilman Santarius, Dirk Aßmann and others: Consumption of water . In: Wuppertal Institute (ed.): Fair Future - Limited resources and global justice . CH Beck , Munich 2005, ISBN 3-406-52788-4 , p. 108 ff . (278 pages).

Web links

  • virtuelles-wasser.de website of the "Association for the Environment and Nature Conservation Germany"
English

Individual evidence

  1. AY Hoekstra (Ed.): Virtual water trade (English), p. 16 on the subject of the water footprint, UNESCO-IHE , Delft, 2003.
  2. The water does not dissolve, but it is about all the water that we use (as a rule, it is also degenerated in the process ). → duden.de: water consumption
  3. n-tv: Inventor of virtual water: Allan receives water award
  4. Pascal Blanc, Bruno Schädler: The water in Switzerland - an overview. (PDF; 8.9 MB) In: unibe.ch . 2013, accessed April 15, 2019 .
  5. a b c d e f Wirtschaftswoche, issue 30 and 31, 2008
  6. a b c d e GEO Subject Lexicon Bnd. 1 Our Earth , p. 48, 2006, ISBN 3-7653-9421-1
  7. MM Mekonnen, AY Hoekstra: The green, blue and gray water footprint of crops and derived crop products. Volume 1: Main Report. December 2010. Retrieved July 14, 2020 .
  8. a b P.M. Magazine Questions & Answers, December?
  9. http://www.eurekalert.org/pub_releases/2002-11/acs-ttp110502.php
  10. Water footprints of nations: Water use by people as a function of their consumption pattern (PDF; 445 kB), Water Resour Manage (2006) , page 6
  11. http://www.virtuelles-wasser.de/mandel/
  12. MM Mekonnen, AY Hoekstra: The green, blue and gray water footprint of farm animals and animal products. UNESCO-IHE, accessed February 2, 2017 .
  13. Appendix V to Mekonnen / Hoekstra, 2010. Retrieved on February 2, 2017 .
  14. Selection of some key figures on the water footprint for beef from Mekonnen / Hoekstra, 2010. landtreff.de, accessed on February 2, 2017 .
  15. ^ AY Hoekstra: Human appropriation of natural capital: A comparison of ecological footprint and water footprint analysis . In: Ecological Economics . tape 68 , no. 7 , May 15, 2009, p. 1963–1974 , doi : 10.1016 / j.ecolecon.2008.06.021 ( PDF ).
  16. ^ A b Felix Gnehm: The water footprint of Switzerland . An overall picture of Switzerland's dependence on water. Ed .: WWF Switzerland . 2012 ( admin.ch [PDF; 4.7 MB ]).
  17. Thirsty Goods: Almond. Retrieved May 7, 2019 .