| Virtual Water: The Unknown Knowns Vinod T R1, Thrivikramji KP2 and Babu Ambat3 1Program Director, 2Professor Emeritus, 3Executive Director Centre for Environment and Development, Thiruvananthapuram
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Virtual Water: The Unknown Knowns Vinod T R1, Thrivikramji KP2 and Babu Ambat3 1Program Director, 2Professor Emeritus, 3Executive Director Centre for Environment and Development, Thiruvananthapuram

Virtual Water: The Unknown Knowns Vinod T R1, Thrivikramji KP2 and Babu Ambat3 1Program Director, 2Professor Emeritus, 3Executive Director Centre for Environment and Development, Thiruvananthapuram




The term “virtual water” began appearing in the water resources literature in the mid-1990s. The concept of Virtual Water was introduced by Tony Allan in the nineties (Allan, 1993; 1994; 1998), when he studied the possibility of importing virtual water as a partial solution to problems of water scarcity in the Middle East. The concept of ‘embedded water’ (which was coined before 1994) has not managed to gain acceptance. The virtual water content of a product is defined as the freshwater “embodied” in the product, not in real sense, but in virtual sense. Other wards, Virtual water can be defined as the water that is required for manufacturing a product or for rendering a service. It refers to the volume of water consumed or polluted for producing the product, measured over its full production chain. A famous equivalence often used by Allan is that a thousand tons of water is necessary to produce a ton of wheat (Allan, 2003; 2011). Indians also paid close attention when virtual water reached the global water agenda at the March 2003 World Water Forum (Kumar and Jain, 2007; Reddy, 2005; Sharma, 2003; Sivakumar, 2004).

Virtual water is a term that links water, food, and trade and is a successful means by which water deficit economies can remedy their deficits. Virtual water happens to be integral to the strategic commodity food and unable to escape a contentious role in discourse on the political economy of food security. The potential role of virtual water is so contentious 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, 2001). Import of water-intensive commodities reduces water demand whereas export of water-intensive commodities raises national water demand and thus enhances water scarcity at local level. By emphasizing the importance of the water content of crops, virtual water is shifting the focus of the discourse from “‘local water use efficiency’ at user level and ‘water allocation effi­ciency’ at river basin level” to “global water use efficien­cy” (Hoekstra and Hung, 2005; Beadon and Page, 2010).

Virtual water Vs Water footprint

The ‘virtual water content of a product’ refers to the water volume embodied in the product alone whereas the water footprint of a product is the total volume of freshwater consumed or polluted over the various steps of the production chain. The water footprint of a product is thus a multi-dimensional indicator, whereas virtual water content refers to a volume alone. The aggregate water footprint of the consumers in a nation is defined as the total amount of freshwater that is used to produce the producers consumed by the inhabitants of the nation. The water footprint of national consumption is calculated as the total use of domestic water resources plus the nation’s gross virtual water import minus the nation’s gross virtual-water export.

The “green” and “blue” components of virtual water are also well studied.  “Green water” is used to denote effective rainfall or soil moisture that is used directly by plants, while “blue water” denotes water in rivers, lakes, aquifers, or reservoirs (Falkenmark and Rockström, 2004; Rost et al., 2008). As such, blue water generally refers to water that can be delivered for irrigation or made available for alternative uses, while green water must be used directly from the soil profile.

Understanding virtual water flows

VW differs from direct water use, in that the consumer does not perceive it and once  used in production, it is embodied in consumable commodities. For purposes of analyzing flows of VW, it is important to keep in mind that VW is passed on between intermediate consumers, before it reaches the final user beyond which its flow ceases. Similarly, the VW flow between two nations or provinces within a nation is the volume of virtual water contained in the traded product between the nations or regions. The analysis of Global VW flows was introduced by Hoekstra and Hung (2002), Hoekstra (2003), Chapagain and Hoekstra (2003) and Zimmer and Renault (2003). Hoekstra and Chapagain (2008) estimated that the global VW flow is of the order of 1625 billion m3/yr during 1997-2001, of which 61% (i.e., 987 billion m3/yr) was linked to trade of crops and crop products, 17% (i.e., 276 billion m3/yr) to livestock and livestock products and the remaining 22% (362 billion m3/yr) to industrial products.












Fig.1 Schematic of virtual water flows (After Hoekstra et al., 2011)

Virtual water trade

Rising water demand due to population growth, industrial development and urbanization, warranted economically efficient use of water resources. It is predicted that by 2025, two-thirds of the world population could be under “stress conditions” (500-1000 m3 y-1 per capita), and 1800 million people are expected to be living in countries or regions with “absolute water scarcity” (<500 m3 y-1 per capita). Concept of VW and its trade that ensued are bestowed with widespread optimism for its perceived potential or promise to solve water insecurity, but at the same time cir­cumventing major political and social costs. By “VW trade” what is meant is the trade of water in virtual form or state, when a product or produce is traded between two provinces within a nation or between nations.  Again, VW allows governments to conceal or tide over water scarcity by importing water intensive crops. Chapagain and Hoekstra (2004) published “The Water Footprint of Nations” – the first global study – analyzing VW flows among the nations during 1997-2001 and based on international trade of crop, livestock and industrial products.

Fig.2 Net global VW imports, 1997-2001

(after Hoekstra and Chapagain, 2008)

A recent report (Proceedings of the National Academy of Sciences, 2012) revealed that China is the country with largest water footprint of consumption in the world (1,368 Gm3/yr), followed by India (1,145 Gm3 y-1 ) and the United States (821 Gm3 y-1). But the major gross VW exporters are the United States (314 Gm3 y -1), China (143 Gm3 y-1), India (125 Gm3 y-1), Brazil (112 Gm3 y-1), Argentina (98 Gm3 y-1), Canada (91 Gm3y-1), Australia (89 Gm3 y-1), Indonesia (72 Gm3y-1 ), France (65 Gm3 y-1) and Germany (64 Gm3 y-1). The United States, Pakistan, India, Australia, Uzbekistan, China, and Turkey are also the largest blue virtual water exporters, accounting for 49 per cent of the global blue virtual water export. Yet all of these countries are partially under water stress, which raises the question whether or not the implicit or explicit choice to utilize the limited national blue water resources for export products is sustainable and most efficient.

Virtual water trade in India

In India, with a rapidly growing population and improving living standards, the water requirement of India is increasing while the per capita availability of water resources is declining day by day. According to FAO (2010), during 2001-2005, India exported 228.61 Gm3 of VW (average= 45.72 Gm3 y-1 ) and imported 358.27 Gm3 of VW (average = 71.65 Gm3 y-1 ). In fact, India was a net importer of 25.93 Gm3/yr of virtual water related to crop and livestock products during the same time frame.

Based on certain assumptions about interstate movement of agricultural products, Kampman (2007) estimated the mean annual import (or export) of virtual water among the Indian states (see Fig.3). Kampman (2007) the states of Punjab, Uttar Pradesh and Haryana are the largest exporters of VW while Bihar, Kerala, Gujarat, Maharashtra, Jharkhand and Odisha are the frontline importers. The current state of inter-state VW trade is tending to aggravate scarcities in already water scarce states, with VW flowing  from water scarce to water rich regions and in the direction opposite to the proposed physical transfers (Kampman et al., 2008; Verma et al., 2009). Instead of a prescription of water endowments, VW flows are influenced by several other factors such as per capita availability of arable land and more importantly by biases in food and agriculture policies of the Government of India like for e.g., procurement patterns of the Food Corporation of India. In order to have a comprehensive understanding of virtual water trade, non-water factors of production need to be taken into consideration.

Fig.3 Inter-state virtual water flows (109m3/yr) in India, as estimated by Kampman (2007)


Virtual water in Crop and Animal products

The VW content of animal products is far higher than that of crop products. Animals need to be fed and watered right through their lives. The total amount of real and VW consumed by animals and the water expended during processing are proportionately partitioned among the diverse animal products. This proportional allocation may also occur in terms of weight or more frequently, by using the market value. As per the estimates of Mekonnen and Hoekstra (2011) the ready-to-eat animal products have an estimated VW content of 3,000 to 15,000 litres/(kg product) of VW, as against about ~1,000 to 3,000 litres/(kg product) for ready-to-use crop products. As the VW content is significantly higher for cotton, coffee beans and cocoa beans, these plant products  clearly stand apart as an exception.


Fig.3 Global average crop water consumptive use, m3/kg

The VW content of products strongly vary from place to place, and is strongly influenced by climate, level of technology in farming and consequent yield. The units used so far to express the VW content of various products are in terms of cubic meters of water/ ton of product. For example, global average VW content of rice (paddy) is 2291m3/ton while it is 1334m3/ton for wheat. VW content of (broken) rice in the shop is ~ 3420m3/ton. A consumer might be more interested in knowing how much water a product consumes per unit of consumption. Table 1 is the global average of VW for selected products.Tables 2, 3 and 4 depict the average VW in selected crop and animal products in India.

Table 1 Global average VW content of selected products per unit of product

Product VW, liter Product VW, liter
Black tea (250 ml) 35 Bread (30g) 40
Beer (250 ml) 75 Potato (100g) 25
Wine (125 ml) 120 Apple (100g) 70
Black coffee (125 ml) 140 Orange (100g) 50
Orange juice (250 ml) 170 Egg (40g) 135
Apple juice (250 ml) 190 Potato chips (200g) 185
Milk (200 ml) 200 Hamburger (150g) 2000




Table 2   Average VW in some  crop and animal products, India (Chapagain and Hoekstra, 2004)

Category VW  (m3/ton) Category VW (m3/ton)
Rice (Paddy) 2850 Beef 16482
Rice (Broken) 4254 Pork 4397
Wheat 1654 Goat meat 5187
Maize 1937 Sheep meat 6692
Soybeans 4124 Chicken meat 7736
Barley 1966 Eggs 7531
Sorghum 4053 Milk (fat<1%) 1369
Millet 3269 Milk (fat>6%) 2547
Sugarcane 159 Milk powder 6368
Coffee (green) 12180 Cheese 6793
Coffee (roasted) 14500 Buttermilk 2068
Tea (powder) 7002 Yogurt 1592
Sugar (refined) 1391 Leather (bovine) 17710



Table 3   Average VW in some edible oils, India (Chapagain and Hoekstra,2004)

Category Virtual water content (m3/ton)
Coconut oil 3051
Groundnut oil 8875
Olive oil 21106
Palm oil 5169
Sunflower oil 8541
Linseed oil 19159
Mustard oil 4643








Table 4   Average VW in crop products, India (Chapagain and Hoekstra,2004)

Type VW in (m3/ton) Category VW in (m3/ton)
Potato 213 Banana 415
Sweet potato 277 Orange 364
Beans (green) 487 Lemon 611
Urad/ Mung Dal 3078 Grapefruit 411
Pea (green) 178 Apple 1812
Chick pea 2712 Pear 1287
Pigeon pea 4066 Apricot 2424
Cabbage 180 Cherry 2532
Onion (fresh) 214 Peach 1564
Tomato 302 Plum 1907
Cauliflower 100 Watermelon 362
Pumpkin 238 Mango 1525
Cucumber 357 Pineapple 305
Carrot 197 Papaya 922
Garlic 1268 Strawberry 296
Ginger 1556 Cashew nut 15340
Pepper 8333 Groundnut (in shell) 3420



The question of ‘how much water one eats every day?’ might sound strange but true if paid some more thought. Estimates by the Water Footprint Network (WFN), show that the water needed in the production of industrial products one uses daily, such as paper, cotton and clothes, amounts to ~450 l d-1. WFN scientists determined that globally 92% of the water one use is invisible and embedded in their food. Research shows that an Italian eats nearly 5,600 litres each day; Brazilian 5,200 litres daily, an Indian 2700 litres and a US citizen consumes 6500 litres/day. Water expert Tony Allan warns: what we eat and what we do not waste will enable us to be globally water secure. Sensible food consumption and natural resource-aware trade should become two of the principal commandments for our 21st century society if we want to build a sustainable future. In light of the existing water scarcity and imbalances in water availability at globally and regionally, a sustainable virtual water trade is utmost important in bringing water use efficiency. A shift towards water conservation and water demand management is essential for the sustainability of water resources and the environment, as well as economic efficiency and social development.


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