The aim of this study is to estimate the green, blue and grey water footprint of wheat in a spatially-explicit way,
both from a production and consumption perspective. The assessment is global and improves upon earlier
research by taking a high-resolution approach, estimating the water footprint of the crop 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 wheat production is
estimated for each grid cell. We have used the water footprint and virtual water flow assessment framework as
in the guideline of the Water Footprint Network (Hoekstra et al., 2009).
The global wheat production in the period 1996-2005 required about 1088 billion cubic meters of water per
year. The major portion of this water (70%) comes from green water, about 19% comes from blue water, and the
remaining 11% is grey water. The global average water footprint of wheat per ton of crop was 1830 m3/ton.
About 18% of the water footprint related to the production of wheat is meant not for domestic consumption but
for export. About 55% of the virtual water export comes from the USA, Canada and Australia alone. For the
period 1996-2005, the global average water saving from international trade in wheat products was 65 Gm3/yr.
A relatively large total blue water footprint as a result of wheat production is observed in the Ganges and Indus
river basins, which are known for their water stress problems. The two basins alone account for about 47% of
the blue water footprint related to global wheat production. About 93% of the water footprint of wheat
consumption in Japan lies in other countries, particularly the USA, Australia and Canada. In Italy, with an
average wheat consumption of 150 kg/yr per person, more than two times the word average, about 44% of the
total water footprint related to this wheat consumption lies outside Italy. The major part of this external water
footprint of Italy lies in France and the USA.
|Name||Value of water research report 42|
|Publisher||UNESCO-IHE Institute for Water Education|