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4 S. Merrett, J.A. Allan, and C. Lant
IWRA, Water International, Volume 28, Number 1, March 2003
Virtual Water - the Water, Food, and Trade Nexus
Useful Concept or Misleading Metaphor?
by J.A. (Tony) Allan, SOAS/King’s College London, Water Research Group,
The Strand, London, United Kingdom
Abstract: The purpose of this contribution is first, to respond to the request for clarification of the
term virtual water by Stephen Merrett. Second, it provides a narrative for those who might not be aware
of the origin and development of the concept. Third, the discussion will draw attention to the problems
encountered in gaining entry for the idea into those water policy discourses where the it was most
relevant. The concept has been in currency for almost a decade. The use of the term increased rapidly
after 1995 and by the millennium the idea had become central to many dialogues relating to water
security preliminary to the Kyoto World Water Forum in March 2003. Merrett’s (2003) challenge that
the water community should give attention to the language used by its diverse professionals and scien-
tists is timely. Inter-disciplinarity is always difficult. In the water sector such difficulties have been
magnified not just by the perversity of its tribal dynamics but especially because the political stakes are
high. This account and response will not meet the standards of philosophical analysis set by Merrett. It
is written in the spirit of having a further impact on an important on-going discourse. And in the hope
that the ideas reach water policymakers. Others might want to comment on whether they think virtual
water is a scientifically respectable term or perhaps that it is just a potentially misleading, though
useful, metaphor.
Linking Water, Food, and Trade
“..communities and nations that live in river basins (wa-
tersheds) operate in “open” economic systems
(problemsheds) where resource shortages can be com-
pensated” (Allan, 2001a).
The purpose of this article is first to respond to the
comments of Stephen Merrett on the problems he has as
an economist/philosopher with the term virtual water
(Merrett, 2003), and secondly, to provide a narrative out-
lining how the idea has been received during the past de-
cade. The second goal is addressed first and the discussion
concludes with a response to Merrett’s comments.
Throughout it will be shown that the impact of what the
author terms, the “virtual water remedy to local water
scarcity,” will be shown to depend more on political pro-
cesses rather than on the scientific authority of the idea or
precision with which it is defined.
The term “virtual water” was coined at a seminar at
SOAS in about 1993. If the idea was invented indepen-
dently by another individual or group it is hoped that this
article will stimulate them to enter the discussion. Before
1993 the author had used the term embedded water (Allan
1993; 1994), which did not capture the attention of the
water managing community. The idea was of course de-
rivative. Israeli economists had by the mid-1980s spotted
that it was less than sensible from an economic perspec-
tive to export scarce Israeli water. This was in effect what
they argued was happening every time water intensive
oranges or avocados were exported from semi-arid Is-
rael. (Fishelon, 1992). The idea has been elaborated more
recently for Israel (Yegnes-Botzer, 2001) and for Egypt
(Wichelns, 2001). Hoekstra and Hung (2002) suggest that
in 1999 Israel exported 0.7 cubic kilometers of virtual water
and imported 6.9 cubic kilometers. For Egypt, they calcu-
lated the net virtual water import to be 15.3 cubic kilome-
ters.
The term “embedded water was” under-whelming in
its impact. Virtual water, by contrast, had an immediate
impact. It was accessible and people appeared to accept
it readily as a useful metaphor. The author thereafter used
the term to draw attention to the notion that serious local
water shortages could be very effectively ameliorated by
global economic processes. As a Middle East specialist,
he was particularly aware that the Middle East and North
Africa were facing increasing water deficits. This was
especially the case if total water self-sufficiency, includ-
ing water for food, was taken to be the criterion of deficit.
Total water self-sufficiency requires that a national
economy has sufficient local water to provide drinking
water, domestic water, water for industry and services,
and water for food and other essential agricultural pro-
duction. Since the late 1970s, and especially since the early
1990s, self-sufficiency has also included – at least in the
best managed economies – an explicit allocation to sup-
port the environmental services underpinned by water in
the environment.
At meetings with very senior Middle Eastern cabinet
level officials during the first half of the 1990s the author
Virtual Water - A Discussion 5
IWRA, Water International, Volume 28, Number 1, March 2003
discovered that linking strategic food deficits with water
deficits was a no-go area in public discourse. He later
called the problem of linking water food and trade in such
public discourse in the Middle East, a sanctioned discourse
(Allan 2001a), after discussing the phenomenon with his
SOAS politics colleague Charles Tripp (1996).
He also found that the term could irritate economists
and engineers both inside and outside the region: the former
argued that it was confusing to suggest that water was
being traded in the process of moving water intensive com-
modities, such as grain, from one place to another. This is
one of the issues taken up by Merrett (2003). It is not
water that is being traded; it is food. Economists prefer to
capture the value of the water input as part of the value of
the land where the product is produced. A moist tract would
be more valuable and command more rent, and produce
more output than a neighboring dry tract. Engineers gen-
erally felt the idea was fanciful.
It would be wrong to suggest that all engineers re-
jected the idea. The approach was shared with a senior
South African engineer, Alan Conley, in May 1995 at a
conference in Oman. He immediately saw the relevance
of the thinking to the regional water resource predicament
of southern Africa. Post-Apartheid South Africa had
emerged from its siege predicament. Water professionals
there had the chance to take a more comprehensive glo-
bal view of their water security options. They had begun
to recognize the merit of trading food within the southern
African region rather than embarking on a new hydraulic
mission involving ambitious inter-basin water transfers. As
a result of the enthusiasm of Alan Conley a paper was
requested for the ICID Congress in Cairo in 1996. One of
the first articles outlining the virtual water concept ap-
peared, therefore, in the ICID Journal in 1998. (Allen,
1998).
Agricultural engineers also showed an interest in the
economic processes that are part of the complex that
achieve agricultural commodity production. An invited pa-
per appeared in Agricultural Water Management in 1999,
which drew attention to the role of virtual water in ad-
dressing regional water deficits (Allan, 1999). The editor
of the journal, International Water and Irrigation, also
invited a contribution on the topic in 2001. This article
(Allan, 2001b) consciously popular, is the author’s pre-
ferred summary in that the metaphor has been much en-
hanced by cartoon graphics by the editor which make the
idea accessible with just a very cursory scan of the mate-
rial by very busy people. Some of the cartoons accord
with part of Stephen Merrett’s vision of ships carrying
cargoes of grain supposedly followed by additional ves-
sels loaded with the free water that had been used to raise
the grain. The cartoonist, without the constraints of philo-
sophical rigour, seems to have captured the idea of virtual
water through judicious use of the image and some well
placed text. They have labeled the sack of wheat, “wa-
ter.” This is a metaphor and certainly not truth.
Figure 1. Water in commodities. Virtual water - the “intensive” (We-
ber, 1904) version of the concept (Allen, 2001b).
Figure 2. Virtual water trade - the “extensive” (Weber, 1904) version
of the concept (Allen 2001b)
Virtual Water: A Definition
Operationally effective, and water deficit ameliorat-
ing, global trading systems were shown by outsiders to
exist. But awareness of them was of such destabilising
potential that the social and political systems of the MENA
region trapped the region’s hydro-politics in a ‘sanctioned
discourse’ of non-awareness (Allan, 2001a).
Virtual water is the water needed to produce agricul-
tural commodities. The concept could be expanded to in-
clude the water needed to produce non-agricultural
commodities. The author has not attempted to expand the
scope beyond agriculture.
It requires about 1,000 cubic meters of water to pro-
duce a ton of grain. If the ton of grain is conveyed to a
political economy short of freshwater and/or soil water,
then that economy is spared the economic, and more im-
portantly, the political stress of mobilizing about 1,000 cu-
bic meters of water. The author observed that by the
millennium the Middle East and North Africa (MENA)
was importing at least 50 million tons of grain annually.
This tonnage required 50 cubic kilometers (billion cubic
meters) of water to produce it, which is the volume of
freshwater that flows into Egypt each year down the Nile.
6 S. Merrett, J.A. Allan, and C. Lant
IWRA, Water International, Volume 28, Number 1, March 2003
The volume is also equivalent to about 30 percent of the
freshwater resources of the MENA region. Mobilizing the
annual flow of the Nile would be an unimaginable chal-
lenge to the engineer. Farmers and grain traders make
light work of such tasks and have done so since antiquity.
The patterns of such trade are of course very different
now than they were 2,000 years ago. Europe currently
exports grain to Egypt whereas Egypt exported grain and
other food commodities to Rome 2,000 years ago.
Virtual water is a term that links water, food, and trade.
Figure 3 attempts to map the resources involved in achieving
water security. The diagram shows that the 10 percent or
so of water needed for drinking, domestic, industrial, and
service uses must come from freshwater or from manu-
factured sources. The 90 percent of water need for food
and other agricultural production can come from freshwa-
ter, from soil water or it can be accessed in effect via food
imports. Virtual water and manufactured water are the
very successful means by which water deficit economies
can remedy their deficits. The author is grateful to Malin
Falkenmark for her tireless campaigning for the idea that
soil water is the major water input to the productive sector
of agriculture. She also emphasises the role of soil water
in the environment in supporting natural vegetation
(Falkenmark, 2000).
Virtual water has proved to be a very accessible con-
cept at least in some epistemic communities in the water
sector, if not in all. When shared with those not actually
involved in the tough conflictual realities of making and
implementing water policy the idea has proved to be readily
grasped and accepted. Thousands of students at all levels
have taken the idea in their stride after a few minutes of
explanation; sometimes by using material on the internet.
Even larger numbers of outsiders to the water profession,
detached again from the tough politics of water policy-
making and implementation, have also found the concept
easy to embrace and share. The recent publication by
Hoekstra and Hung (2002), which will be discussed at the
Third World Water Forum in Kyoto in March 2003, shows
that some water engineers liked the idea so much that
they have devoted months to adding quantitative substance
to the conceptual utility of the idea.
However, water policy makers and water profession-
als who know there is much at stake have rejected the
idea (Allan, 2001a) with the same passion that national
fishing communities greet proposals that they should re-
duce their catches according to international collective
action principles, or with the same total opposition with
which the French Government faces its partners over the
reform of the Common Agricultural Policy. France’s Eu-
ropean partners advocate reform to meet international
collective action principles and environmental goals but
these reforms are not in the French interests (Financial
Times, 2003). In developing countries, including some that
are oil enriched, the notion of virtual water appears to
threaten vital farming livelihoods. Drawing attention to
where national security actually lies is potentially very
controversial. Making the link between water and food
security a high profile issue is associated with high risks
and high political prices for water policy makers.
At the same time as the metaphor of virtual water
was gaining currency in the mid-1990s, the trade econo-
mists at the World Bank had started to use another term
the “water, food, and trade nexus” (McCalla, 1997). The
concept is the same as virtual water but the longer and
more explicit term has failed to gain a place in water policy
terminology just as embedded water did not capture the
attention of water sector professionals. Merrett’ s preferred
definition for virtual water is the “crop water requirements
of food exports.” We shall see later that this is only a
partial definition of the idea. It is an intensive definition,
involving water and crop production, rather than an exten-
sive definition involving the impact of the traded food on
the water economies and the water policies of water defi-
cit economies.
Diffusion Towards A More Precise Quantification
The author gained satisfaction from the rapid diffu-
sion of the idea in the second half of the 1990s. It was
especially satisfying to hear the term used by profession-
Figure 3. Showing (1) The extent of water dependency (D) of differ-
ent water deficit economies (Hoekstra & Hung, 2002); (2) How local
water can come from freshwater sources and soil water sources; and
(3) How manufactured water and virtual water can remedy the water
deficits.
Virtual Water - A Discussion 7
IWRA, Water International, Volume 28, Number 1, March 2003
als who had originally been unhappy with the idea. That
the topic would be addressed in Kyoto at the World Water
Forum was additionally gratifying. Finally, it is very pleas-
ing indeed that the challenge of adding quantitative sub-
stance to conceptual acceptance has been achieved by
the “value of water” research group at IHE in The Neth-
erlands (Hoekstra and Hung, 2002).
Valuing virtual water was an early problem for the
author. The cost of accessing water in a soil profile in a
temperate region could be counted as free. The only pos-
sible costs would be the social costs of farmers enduring
the privations of remote and inclement locations – often in
the absence of a mate. On the other hand, water accessed
by irrigated farms could be counted in US cents per cubic
meter or as high as more than US$0.50 per cubic meter if
principles of marginal pricing of water were adopted.
Associating products and commodities with the inputs
needed to produce them is not new. Ricardo (1846) and
later Marx, argued persuasively that the labor content of
production was important in determining the price of com-
modities. Over a century later, oil economists labored might-
ily to enumerate the energy content of commodities and
services after the oil shocks of 1973 and 1979–1980 seri-
ously heightened awareness of the strategic significance
of oil. Conversations with those who had followed the oil/
energy analysis of the 1970s led the author to realize that
attempting to quantify in detail such complex economic
processes would lead to frustration. The energy content
analysis was related to the complex global oil and energy
markets, enmeshed in constantly changing and diverse
taxation regimes, which did not prove to be susceptible to
attempts to match theory with available data and outcomes.
With this experience in mind, the author judged that
the main intellectual return would be achieved by gaining
currency for the virtual water concept. Quantification of
the detail would be a time-consuming project with am-
biguous and inconclusive outcomes. The author also found
from the first sharing of the idea that understanding the
political economy into which the notion of virtual water
was introduced appeared to be more important than map-
ping volumes and movements. Introducing sound numbers
into the discourse had not proved to be important in that
the water policy community, at least in the water chal-
lenged political economies in semi-arid regions, had no
appetite for the numbers associated with the virtual water
process. Any numbers would be rejected along with the
rejection of the idea.
The author also very quickly found that economists,
engineers, lawyers, international lawyers, and international
relations specialists could get their analyses wrong because
they were not aware of the role of virtual water in interna-
tional economies.
Virtual water played havoc with the narrow, environ-
mentally deterministic assumptions on which such special-
ists generally based their analyses. All the analysts who
have conjured the prospect of water wars have ignored
the role of virtual water in ameliorating regional water
deficits. For example journalists such as Bulloch and
Darwish (1993) and academics such as Homer-Dixon
(1991; 1994). Statements by leading political figures such
as the late King Hussein of Jordan and the late President
Anwar Sadat of Egypt and even a Vice-President of the
World Bank, Ishmail Serageldin, that there would be wa-
ter wars in the Middle East, were made in response to
particular public circumstances and, though frequently
requoted, have less authority as the decades roll on. When
the public relations department of the World Bank was
interrogated about the reliability of the Serageldin com-
ment the response was inconclusive but it appeared that a
publisher had been overhasty in attributing the comment.
The London Water Research Group has looked at the
role of virtual water in the Middle East and North Africa
and in Southern Africa on the grounds that these are the
most water insecure regions (SOAS, 2002). But this was
a small venture compared with the very promising and
globally comprehensive report of Hoekstra and Hung
(2002). The IHE group has provided a preliminary quanti-
fication and analysis of the role of virtual water in the
global food system. The study is very promising in terms
of insight and revelation. This has been possible because
of their collation of a number of sources that have become
available in the past five years. First, estimates of crop
water requirements in different countries and environments
(FAOSTAT, 2002). These numbers permit a much more
textured set of estimates of local water use than have
been possible in earlier studies. Secondly, they have used
estimates of the levels of use of green water flows of
water in all the countries of the world (Rockström and
Gordon, 2001; Raskin et al., 1997). Thirdly, the global trade
in agricultural commodities has been tracked by FAO
(2002) for over forty years. Their research concludes that
of the 6,000 cubic kilometers of soil and freshwater water
mobilized each year (Shiklamanov, 1997; 2000) to meet
the needs of the world’s 6.5 billion people at the millen-
nium, 695 cubic kilometers were embedded in food com-
modities traded internationally. They conclude:
...the global volume of crop-related virtual water trade
between nations was 695 cubic kilometers per year
on average over the period 1995 to 1999. For com-
parison the global water withdrawal for agriculture
(water use for irrigation) was about 2,500 cubic kilo-
meters per year in 2000 (Shikhlamanov, 1997). Taking
into account the use of rainwater by crops as well, the
total use by crops in the world has been estimated at
5,400 cubic kilometers per year (Rockström and Gor-
don, 2001). This means that 13 percent of the water
used for crop production in the world is not used for
domestic consumption but for export (in virtual form).
This is the global percentage; the situation varies
strongly between countries (see Hoekstra and Hung,
2002) and from year-to-year see Figures 5.1 to 5.29
8 S. Merrett, J.A. Allan, and C. Lant
IWRA, Water International, Volume 28, Number 1, March 2003
(Hoekstra and Hung, 2002).
They also show that wheat is the dominant traded food
commodity in terms of water content- comprising from 26
to 33 percent of the total virtual water associated with
food commodity trade in the period 1995 to 1999. Soybean
ranged form 13 to 22 percent in the same period. The data
for rice were 9 to 24 percent, and for maize 7 to 10 per-
cent (Hoekstra and Hung, 2002).
Another very useful contribution of the Hoekstra and
Hung (2002) report is their association of the virtual water
idea with the concept of the water footprint. Wackermagel
and Rees (1996) developed the powerful idea of the eco-
logical footprint in the mid-1990s. They demonstrated that
political economies such as the United States and those in
Europe draw in substantially more natural resources than
their own endowments. This privileged situation contrasts
with that of many poor economies in the South. Many
Southern economies export their natural resources, often
in markets where they endure very unfavorable terms of
trade. Hoekstra and Hung (2002) show that in the water
sector the temperate climatic endowment of the United
States and France make it possible for their water foot-
prints to be substantially smaller than the water withdrawn
by them from the environment. In the case of the United
States the water footprint is 35 percent smaller than the
amount withdrawn. For France the figure is 48 percent
smaller.
Virtual Water and a Very Little History of
Economic Ideas
For two centuries a much more important idea than
virtual water – that of comparative advantage – has been
in undisputed currency (Ricardo 1846), even if it has been
difficult to square the Heckscher-Ohlin model with actual
trading patterns. Trade was shown to be a very effective
and mutually advantageous means of satisfying local stra-
tegic commodity needs. Ricardo drew attention to the ef-
fective mutual dependence of England and Portugal with
respect to wine and cloth. The notion of comparative ad-
vantage takes on major political significance, in addition to
its economic significance, when related to strategic com-
modities such as first, food and secondly, energy related
commodities such as coal and oil.
The concept virtual water is something of a descen-
dant of the concept of comparative advantage. Virtual
water happens to be integral to the strategic commodity
food and is at the same time unable to escape a conten-
tious role in discourse on the political economy of food
security. The potential role of virtual water is so conten-
tious that those actually managing water and developing
water policy in water scarce economies ensure that the
concept is kept out of water policy-making discourse (Allan
2001a).
More than most commodities, staple foods, which are
very important indeed as a proportion of world trade, are
inextricably political. People have a deep intuitive aver-
sion to being dependent on other economies for their wa-
ter and also for their food. People living in economies,
which are very little or only partially diversified and
industrialised, are particularly subject to collective para-
noia on food and water insecurity. Awareness of a depen-
dence on water and staple food coming from outside there
own sovereign territories can be very destabilising. Be-
cause virtual water is economically invisible and politically
silent it has the wondrous virtue of making it possible for
water policy-makers and managers to cultivate a policy
discourse where it can be assumed that there is no na-
tional water or food deficit. The strategic water deficit is
invisibly and silently solved by importing commodities,
which, through Northern subsidies, are available – extraor-
dinarily - at half their production cost. (ABARE 2001)
Every subsidised ton of wheat imported at the millennium
has been associated with 1000 tons (cubic metres) of free
water.
Water is a factor of production and it was hoped it
would be susceptible to analysis according to the approach
of Hecksher-Ohlin (Bowen, Learner and Sveikauskas 1981
and Krugman and Obstfield 1995) which aimed to analyze
past commodity trade of the embedded basic factors of
production – for example, land and labor. An initial at-
tempt to test whether the factor of production, water, would
be susceptible to such analysis proved to be unrewarding
in southern Africa. (Earle 2001) Further work along the
same lines enabled useful insights for the economies of
the Middle East and North Africa. (Hakimian 2003) The
reason for the less than satisfactory results was mainly
because only freshwater was taken into account; soil wa-
ter estimates were not available. The inclusion of soil water
will improve the predictive results of the Hecksher-Ohlin
model. But the initial negative experience of deploying the
theory seemed to confirm that it was the power of the
virtual water concept to draw attention to the ameliorating
process of the virtual water trade that was its main value.
Rather than its capacity to predict exact volumes “trans-
acted.”
Within a couple of days of receiving the 2002 Hoekstra
and Hung report in Delft, the author was in Sri Lanka, a
relatively water rich country. The island does, however,
endure periods when the monsoon rains are seriously be-
low average. A very serious deviation from the rainfall
norms occurred in 1996, 1997, and 1998. As a result, Sri
Lanka’s food imports rose dramatically (Hoekstra and
Hung, 2002). The levels of imports were such that for the
five year period ,1995 to 1999, Sri Lanka topped the global
list of virtual water “importers,” even outranking Japan by
44 percent. Yet in normal years, Sri Lanka imports scarcely
any food (Hoekstra and Hung, 2002).
The Sri Lankan case is very important in highlighting
the immense flexibility of the virtual water solution. In
addition to its three major virtues of being first very effec-
Virtual Water - A Discussion 9
IWRA, Water International, Volume 28, Number 1, March 2003
tive indeed in addressing water deficits, it is secondly eco-
nomically invisible, and thirdly, politically silent. Virtual water
has a fourth very important quality.
Water embedded in food commodities can be mobi-
lized very quickly and flexibly to remedy the ever-chang-
ing demands of those enduring water and staple food
deficits. This flexibility to remedy periodic water short-
ages out-matches any security measures deployed by en-
gineers to store water behind dams. The hydraulic
measures have local impacts. The virtual water remedy
is global in its reach. The virtual water remedy is also
immensely more powerful than any policies deployed to
manage demand. Water use can end managed in industri-
alized economies located in arid and semi-arid regions, but
slowly. Water use in irrigated agriculture – the big user –
was reduced by about 20 percent in California after 1980
and by 30 percent in Israel in the 1986 to 1991 period
(Allan, 2001a). But no hydraulic system can bring on
stream the volumes of water needed to mobilize the avail-
ability of staple foods as can the virtual water system.
Conclusion: Intensive and Extensive Ideas
Economists have proved to be particularly adept in
their capacity to theorize. Theory helps explain and some-
times predict. Just as important theory helps us communi-
cate. If a theory can be captured in a word or a phrase,
communication, especially across disciplinary divides, can
be immensely facilitated. Coase’s (1960) timeless phrase,
“law reduces transaction costs,” is a powerful example.
“Theory provides guidelines; it sensitizes observers to
alternative possibilities; it highlights where levers might
be pulled and influence wielded; it links ends to means
and strategies to resources; and perhaps most of all, it
infuses context and pattern into seemingly disarrayed
and unrelated phenomena” (Rosenau, 1997).
Economic theory has been made very influential
through the coining of such terms as political economy,
comparative advantage, the falling rate of profit, shadow
price, opportunity cost and transaction costs. In all cases
these concepts link elements of economies and in some
cases of society and politics, which together explain and
illuminate general and particular socio-economic, socio-
political, and socio-legal phenomena.
Weber (1904; 1917) provided a very useful way of
analyzing the nature and scope of such ideas. He sug-
gested that concepts could be intensive and extensive.
Applied to the concept virtual water the Weberian analy-
sis helps in the identification of virtual water’s intensive
and extensive features.
Virtual water is an intensive concept in so far as it
links water, both freshwater and soil water, in the produc-
tive process of crop production. Here water and food have
been linked in the activity of crop production. Implicit is
the idea that crop production, and therefore indigenous
food security, can be limited locally by the availability of
water. This intensive linkage is the one with which Stephen
Merrett is comfortable. He correctly argues that it is the
food produced which is traded and not water.
The main contribution of the term virtual water is, how-
ever, in the opinion of the author, its capacity to be exten-
sive. The term links water and food and in addition links
the availability of these commodities across national econo-
mies so that consumers as well as producers are consid-
ered. Traders link consumers in water deficit political
economies with producers and resources in distant water
surplus national economies. Like Ricardo’s generic term,
comparative advantage, virtual water is an extensive idea
albeit in a narrower field.
In diffusing the term virtual water over the past de-
cade the author has sometimes verged on hyperbole –
mea culpa. The overstatement particularly involved at-
taching the word trade to virtual water. One must agree
with Stephen Merrett that there is no actual trade in vir-
tual water. But then there are no transactions made in
shadow prices. The concept of the shadow price is not
diminished by its limitation to a theoretical role. The con-
cept of the shadow price remains very valuable in provid-
ing an analytical perspective on underlying fundamentals.
Similarly, the concept of virtual water, it could be argued
provides an analytical perspective on how economies
achieve water security.
One now tends to avoid the use of the term virtual
water trade because it can misrepresent the process. The
punchy term virtual water trade has been replaced, at least
in my own material, by the more awkward and lengthy
sentence – a ton of wheat when imported by a water short
political economy enables those managing scarce water in
such economies to escape the economic and political stress
of mobilising 1,000 tons (cubic meters) of water. How-
ever, the titles listed below suggest that the term virtual
water trade may have already acquired an immovable place
in the vocabulary of the interdisciplinary epistemic com-
munity that addresses the complexities of water policy-
making. The term is scientifically redundant, according to
the Occam’s razor maxim cited by Stephen Merrett, in
that it can be better defined, if less accessibly, by existing
vocabulary. But the discursive processes in which language
constantly evolves, will determine over the coming decade
whether the virtual water and the virtual water trade meta-
phors retain a place in the terminology of water profes-
sionals.
About the Author
Prof. J.A. (Tony) Allan is with the Geography De-
partment, Room M70, King’s College London,The Strand,
London WC2R 2LS, United Kingdom. Tel: 020-7848-2028;
email: tony.allan@soas.ac.uk.
10 S. Merrett, J.A. Allan, and C. Lant
IWRA, Water International, Volume 28, Number 1, March 2003
Discussions open until September 1, 2003. Fishelson, G. 1992. “The Allocation of the Marginal Value Prod-
uct of Water in Israeli Agriculture.” Israeli Agriculture. Ref-
erence Number WP/028.
Hakimian, H. 2003a. “Water Scarcity and Food Imports: An Em-
pirical Investigation of the “Virtual Water” Hypothesis in the
MENA Region.” See Occasional Paper 46: http://www2.
soas.ac.uk/geography/ waterissues/occasional papers/.
Hakimian, H. 2003b. “Water Scarcity and Food Imports: An Em-
pirical Investigatin of the Virtual Water Hypothesis in the
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