An Introduction To Virtual Water

concept was developed by Professor John Anthony Allan
quantifies the water used in the production
of a good or service
said to be ‘virtual’ because once the water is used, it is no
longer contained in the product (example: wheat)
a concept that is rather controversial and
not universally accepted
3 colours of virtual water
BLUE – the volume of surface water or groundwater
that has evaporated as a result of production.
GREEN – the volume of rainwater that has evaporated as
a result of production.
GRAY - the volume of water that is polluted as a
result of production.
in all cases, water is ‘lost’ because it is no longer available
for other uses.
Approximately 50,000 liters
Approximately 140 liters
= 70 liters
= 10 liters
per sheet
= 1300 liters
per kilogram
= 2400 liters
= 32 liters
= 5000 liters
per kilogram
= 3900 liters
per kilogram
= 400,000 liters
can compliment carbon footprints & eco-footprints
a country’s water footprint = virtual water import –
virtual water export
makes a link between water consumption in one place
and the impacts felt by water systems elsewhere
to accurately calculate water footprints, product
transparency is needed from manufacturers and
Netherlands: virtual water import for coffee
…over 250 million cubic meters of virtual water are exported
from South America EVERY YEAR!
why is this important?
UNESCO estimates that we have already reduced global
use by 5% just by managing virtual water – it allows us to
work as a global community to tackle water issues
places with less water can gain access to foods
(and other products) with higher water requirements by
importing them from areas with high rainfall and increased
access to water – this allows water-scarce regions to use
their water resources more efficiently
it makes us think about water differently – a few liters of
water are wasted when you take a long shower, but
thousands of liters of water are wasted when you throw
away food (and other products)
Blue water – irrigation,
energy use, fossil fuel
consumption (water is
used in the extraction
of fossil fuels)
Green water –
Gray water – pollution
through fertilizers
and pesticides
Blue water – processing
of fibers, energy use,
fossil fuel consumption
Gray water – pollution
through dyes
and other chemicals
Blue water – manufacturing
processes, energy use
Gray water – pollution through
fabric treatments,
additional dye and
other chemicals
Blue water – fossil fuel
consumption, packaging,
development of marketing
Gray Water - ……
1 cotton t-shirt = 2700 liters of virtual water

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