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| Titel |
The green, blue and grey water footprint of crops and derived crop products |
| VerfasserIn |
M. M. Mekonnen, A. Y. Hoekstra |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1027-5606
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| Digitales Dokument |
URL |
| Erschienen |
In: Hydrology and Earth System Sciences ; 15, no. 5 ; Nr. 15, no. 5 (2011-05-25), S.1577-1600 |
| Datensatznummer |
250012790
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| Publikation (Nr.) |
 copernicus.org/hess-15-1577-2011.pdf |
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| Zusammenfassung |
This study quantifies the green, blue and grey water footprint of global
crop production in a spatially-explicit way for the period 1996–2005. The
assessment improves upon earlier research by taking a high-resolution
approach, estimating the water footprint of 126 crops at a 5 by 5 arc minute
grid. We have used a grid-based dynamic water balance model to calculate
crop water use over time, with a time step of one day. The model takes into
account the daily soil water balance and climatic conditions for each grid
cell. In addition, the water pollution associated with the use of nitrogen
fertilizer in crop production is estimated for each grid cell. The crop
evapotranspiration of additional 20 minor crops is calculated with the
CROPWAT model. In addition, we have calculated the water footprint of more
than two hundred derived crop products, including various flours, beverages,
fibres and biofuels. We have used the water footprint assessment framework
as in the guideline of the Water Footprint Network.
Considering the water footprints of primary crops, we see that the global
average water footprint per ton of crop increases from sugar crops (roughly
200 m3 ton−1), vegetables (300 m3 ton−1),
roots and tubers (400 m3 ton−1), fruits (1000 m3 ton−1), cereals (1600 m3 ton−1), oil
crops (2400 m3 ton−1) to pulses (4000 m3 ton−1). The water footprint
varies, however, across different crops per crop category and per production
region as well. Besides, if one considers the water footprint per kcal, the
picture changes as well. When considered per ton of product, commodities
with relatively large water footprints are: coffee, tea, cocoa, tobacco,
spices, nuts, rubber and fibres. The analysis of water footprints of
different biofuels shows that bio-ethanol has a lower water footprint (in m3 GJ−1) than biodiesel, which supports earlier analyses. The crop used
matters significantly as well: the global average water footprint of
bio-ethanol based on sugar beet amounts to 51 m3 GJ−1, while this is 121 m3 GJ−1 for maize.
The global water footprint related to crop production in the period
1996–2005 was 7404 billion cubic meters per year (78 % green, 12 % blue,
10 % grey). A large total water footprint was calculated for wheat (1087 Gm3 yr−1), rice (992 Gm3 yr−1) and maize (770 Gm3 yr−1). Wheat and
rice have the largest blue water footprints, together accounting for 45 %
of the global blue water footprint. At country level, the total water
footprint was largest for India (1047 Gm3 yr−1), China (967 Gm3 yr−1)
and the USA (826 Gm3 yr−1). A relatively large total blue water footprint
as a result of crop production is observed in the Indus river basin (117 Gm3 yr−1) and the Ganges river basin (108 Gm3 yr−1). The two basins
together account for 25 % of the blue water footprint related to global
crop production. Globally, rain-fed agriculture has a water footprint of
5173 Gm3 yr−1 (91 % green, 9 % grey); irrigated agriculture has a
water footprint of 2230 Gm3 yr−1 (48 % green, 40 % blue, 12 %
grey). |
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