Wednesday, July 25, 2012

Virtual Water: Accounting for Water Use

Following on from my last blog on the discovery of a massive aquifer under part of Namibia I thought it might be useful to consider a key accounting concept for water resources: virtual water. The term ‘virtual water’ was coined by Tony Allen of SOAS and and refers to the invisible water, the water that it takes to produce the food and goods we consume or as Virtual Water puts it

Virtual water is the amount of water that is embedded in food or other products needed for its production.’

(Other websites on virtual water include: Virtual Water)
Some of the figures involved are quite amazing. A kg of wheat takes 1,000 litres of water to produce, a cup of coffee takes 140 litres, 1kg of rice takes 3,400 litres and 1 car takes 50,000l litres of water to produce. You can even work out your own water footprint using the calculator on the site. There is even an app for your mobile! Additionally there is information on national water footprints and, importantly, the idea that virtual water is traded between nations.

Mekonnen and Hoekstra (2011) at the University of Twente published a UNESCO report on the issue of virtual water over the period 1996-2005. They divided virtual water into three colours: green, blue and grey. Green water is the water associated with agricultural production, blue water is that associated with industrial production whilst blue water is the water associated with domestic use. From their analysis they calculated that the global average water footprint for consumption was 1385 m3 per year per capita, with industrialized countries having a footprint of 1250-2850 m3 per year per capita, whilst developing countries had footprints in the range 550-3800 m3 per year per capita. The low values represented low consumption volumes in these countries, whilst the large values represented big water footprints per unit of consumption.

Their key conclusions were that about 20% of the global water footprint for that period was related to production for export. This means that there are large international flows of virtual water with some countries importing virtual water (2320 billion m3 in the time period). In countries where water is scare there is a tendency to import large amounts of virtual water in food and agricultural products, saving national water resources for key uses that add greater value such as industrial production. Tony Allen makes an argument in 1997 for the Middle East being one of the first regions to develop this adaptation to resource scarcity. The relatively large volume of international flows in virtual water generated water dependencies that they suggest strengthen the argument that issues of local water scarcity need to be considered within a global context.

The significance of this concept for the discovery of the aquifer and its use is that the Namibian reserve has to be viewed within a global context. The development of agriculture and the technical development of the resource are likely to be political decisions and increasingly likely to be geopolitical decisions that have to take into account the regional position of Namibia, the likely trade partners for the virtual water, the geopolitical power of potential partners and the future frictions that could arise as environmental change affects the current international demands and flows of virtual water.

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