The following is an edited version of a recent essay, submitted in January. References and the full essay can be provided on request.

With the advent of anthropogenic climate change, it has become par for the course to consider the embodied carbon (and even the embodied energy) of the products we buy and our efforts to reduce our carbon footprint can often influence our shopping habits. It is becoming apparent however, that we also need to consider the embedded water in many of the products we buy, as we may be depriving water-scarce countries of this increasingly valuable resource and hastening future environmental and socio-economic crises for them and perhaps for ourselves. However, there is evidence to support the case for these same water-scarce countries sourcing many, if not all of their water intensive foodstuffs from water-rich countries. This paper will examine the issue of embedded water and it's perceived negative and positive aspects, both globally and for the United Kingdom.

Virtual water, sometimes referred to as embedded, exogenous or embodied water, was a term popularised by J Allan (1998) to refer to the water used to produce food products. More recently the term has been extended to include industrial products and agricultural commodities, including livestock and livestock products (Hoekstra & Hung 2005; Chapagain & Hoekstra 2003). The trade in virtual water, although a new concept, is not new in and of itself. Virtual water has been traded for as long trade has taken place, it just hasn't been defined as such. The level of trade in virtual water is known as virtual water flow, expressed either as a positive or negative figure – positive figures imply a net import of virtual water and negative figures a net export.
The use of embedded water, calculated on a country, business or individual basis is known as the water footprint, intended as a compliment to the already well accepted ideas of carbon footprint and ecological footprint.
'Blue' water and 'green' water refers to the source of the water used in the production process. Blue water is surface or ground water and is used for irrigation, industrial processes and municipal supplies, whereas green water is water contained in or absorbed by the organic matter in the soil and is usually replenished through transpiration. The use of 'green' water for production of crops is preferred to irrigating with 'blue' water, because it is far more efficient use or the resource and there is not really any alternative use for it.
If we consider that, globally, we already use half of all available 'blue' water to satisfy our water needs and that seventy percent of that is used for irrigation, whilst only between fifteen and thirty four per cent of all the crops grown in the world are produced through irrigation (Zygmunt, 2007; Fraiture et al 2004), we can see the scale of the waste inherent in the industry. Countries that rely on a preponderance of 'blue' water to grow crops through irrigation are often, though not always, to be found in semi-arid parts of the world where the high temperatures and high evapotranspiration rates make the the growing of water intensive crops (like cereals) an inefficient use of the available water resource – in arid countries the extraction of 'blue' water for irrigation rises to between eighty and ninety per cent (Warner 2003).
With the prospect of a steadily increasing global population, we can only expect the abstraction of 'blue' water to increase, which would put further strain on the available supplies of water and adversely effect vital ecosystems, which also require a portion of this water to survive. It should also be noted that a proportion of 'blue' water is necessary to dilute the water-borne pollution that results from mankind's activities and reducing the dilution that currently takes place could have a detrimental effect on already fragile aquatic ecologies.
As an example of 'green' water agriculture over that of 'blue' water, in temperate climes wheat production will use around one to two cubic metres of water per kg, whilst in arid climes the same

amount of wheat will use three to five cubic metres of water per kg (Hoekstra & Hung 2003). The main wheat exporting countries often produce the grain at a (subsidised) price which outcompetes it's production costs in other wheat producing countries. It is therefore much more cost effective, both in financial terms and in the amount of water used, for water poor countries to import wheat from water rich countries.
In the Middle East and North Africa (MENA), the trade in virtual water has been advanced has a possible preventative measure to avoid water conflicts (conflicts arising from competition over limited water resources) as water-scarce countries can import water intensive crops and products from water rich countries, so diverting their limited supplies of water to more productive or beneficial uses.(Allan 1998).

In fact, Allan (1998) suggests that the virtual water trade has already prevented such conflicts considering that “water demand began to exceed supply in the early 1970s for the region. Some countries have faced deficits since the 1950s.” Pohoryles (2000) suggests that the countries of the Jordan basin will require most of the available water for non-agricultural purposes by 2025, making the trade in virtual water essential for their survival.

The virtual water trade, in many cases including the countries of the Jordan Basin, is the harbinger of the end of food sovereignty (the ability to feed one's own populace) for many nations, particularly those that are water-scarce. This is not a proposition that would likely be welcomed by any sensible statesman, given that they would be making their country dependent on imports to feed the populace, so countries seeking a policy of virtual water trading have been doing so quietly and gradually. For example, Israel despite making no public policy decisions, imports 80% of it's national caloric intake, whilst Palestine imports 65% (Shuval 2005).

Of course, if a country were to become dependent on imports to satisfy their staple food needs, they would also be making much of their previously agrarian population unemployed and would need to invest heavily in industrial or commercial development to ensure their socio-economic stability. Charrier and Curtin (2000) suggest that “no change will be sustainable if it out-runs a community's capacity to adapt to new circumstances.”, so any moves away from domestic production of staple foods needs to be accompanied by a public policy of education and assimilation of the previously agrarian populace into new career streams. It is possible that some countries can continue with more profitable agricultural production than that of cereal crops, when faced with water shortages.

The World Water Council (2004) found that Spain had successfully moved from a prevalence of corn and alfalfa production to mainly olive and grape production when faced with dwindling water supplies, with little socio-economic impacts upon the country as a whole. Of course, such drastic changes in agricultural practices would be incredibly difficult in less developed countries, where subsistence farming is more prevalent and internally produced crops are the principal source of that nation's staple food supplies.

The United States is the world's greatest virtual water exporter at 152 billion cubic metres of water, which in terms of embedded water isn't too bad considering that they only irrigate 15% of their crops, although much of the water for this irrigation comes from over extracted aquifers (Woodhouse and Overpeck 1998) and much of that is used for rice production, which is not particularly suited to the environmental conditions found there. On the other hand, Thailand, one of the world's largest rice exporters, also has very high virtual water export rates and incredibly poor water productivity, but much of the water used here is flood water from inter-seasonal monsoon rains which would otherwise cause damaging floods and then flow into the sea, so should not necessarily be viewed as a detrimental virtual water export. It can also be noted that the process of storing water in paddy fields, increases the amount of water which seeps into the water table, thereby replenishing aquifers. (Zygmunt 2007)
According to Chapagain and Hoekstra (2007) the global water footprint is 7450 billion cubic metres per year, which averages out to 1240 cubic metres per person per year, but the difference between individual countries is vast, with that of China being three and a half times less than that of the United States. The US tops the list at around 6800 litres per person per day, with the UK close to the global average. The US and Canada are high, in part because of the high levels of meat and industrial consumption therein, whilst Malaysia suffers from incredibly poor crop yields coupled with poor agricultural practices (Zygmunt 2007). The UK's water footprint would not be so high if we did not import so much virtual water, which can be explained in part by the high population density of these islands and hence our inability to provide adequate food from the available agricultural land, but also due to supermarkets sourcing much of our food from cheaper overseas suppliers.

The water embedded in foodstuffs is the largest contributor to our global water footprint, with most food worldwide being grown and consumed within a countries borders. Eighty six per cent of the global water footprint is due to food consumption, with only thirteen per cent coming from imports. In comparison, sixty six per cent of the British water footprint is due to our food and yet forty eight per cent is due to virtual water imported in our foods. Such a positive virtual water flow to the UK, implies that we are unable to provide anywhere near sufficient food supplies from internal sources and could be setting ourselves up for a fall were the supply chain to be interrupted somehow.

The Virtual Water Trade could help to ameliorate some of the conditions brought about by the advent of anthropogenic climate change, but by it's very nature of transporting food around the world it could also contribute to higher carbon emissions. We just don't know what the long term effects of climate change will be, but if it leads to excessive droughts in many of the water exporting countries, then those countries that have become dependent on imports of staple foods, including our own, could find themselves facing a starving population and no way to resolve the situation short of rationing and even war to secure adequate supplies.
The issue of embedded water in our food and commodities could have detrimental effects on the economies of the world's developing nations. The promotion of free trade, as a panacea for the economic doldrums that many second and third world nations find themselves faced with, could in the not too distant future, lead to famines on a scale never seen before, due to the the changing climate, the amount of embedded water that these often water scarce countries export and their increasing dependency on imported staple foods (as an attempt to offset their water deficiencies).
A responsible and pragmatic approach for first world countries such as the UK would be to limit the amount of water intensive commodities we source from overseas. Our heavy dependency on imported foodstuffs could easily spell disaster for us, if adverse weather conditions were to effect the countries that supply us with the food we require – a prospect that is increasingly likely as climate change accelerates. In fact in terms of reducing our water footprints, it seems to be hugely irresponsible for a country like ours, with so much 'green' water available to us, to not be producing more water intensive foods like cereals and animal products and exporting some of them to water scarce countries around the world. Unfortunately, embedded water is not taken into account in the calculations of prices of much of our foods and our 'strong' economy often prevents our foods finding a market elsewhere, when much cheaper foods can be sourced from countries with weaker economies.
A globally integrated program which takes into account the embodied carbon, embedded water and ecological footprint in all the agricultural commodities and industrial products we source, whilst ensuring that 'green' virtual water exports to water scarce countries remain high, seems to be a rational and responsible course of action, but realistically is unlikely to happen. It doesn't even seem to be likely that such a program could be established just within the UK, as there are too many conflicting interests that would suffer as a result.