عنوان مقاله [English]
نویسندگان [English]چکیده [English]
The increase of food production for the growing world population makes the assessment of global agricultural water productivities and virtual water flows important. The virtual water concepts together with the water footprint links a large number of sectors and issues, thus providing an appropriate framework to support more optimal water management practices. In other word, to better understand the linkages between humanity's productive activities and this growing pressure on the freshwater resources, the water footprint was developed to measure the amount of water consumed throughout a product's value chain. In this paper, water footprint of agricultural crops was assessed with distinguishing between internal and external water footprints, blue water and green water and the amount of saving and losing water resources by virtual water trade. Agricultural crops in this study included cereal (wheat, barley, rice and maize), fruits (apple, orange, onion and potato) and pulses (chickpea). The total water footprint is calculated as the sum of the use of domestic water resources and virtual water import minus virtual water export. So the total volume of water use in these agricultural crops is calculated based on the total volume of crop produced and its corresponding virtual water content. Similarly, the volume of virtual water export or import is calculated based on the international trade of products and their virtual water content. The blue and green virtual water content of agricultural crop is the volume of blue/ green water used to produce the crop and these are calculated based on blue and green crop water requirements and yields.
The potential of green water in producing agricultural crops is different, on average, 40% of these crops are produced by green water. Estimation of the amount of virtual water content can determine decision making on the production or trade of agricultural crops. Therefore, the high water-consuming products can be removed from the cropping pattern of areas with the water crisis and, instead, replaced by low water-consuming products. In this case, import of high water-consuming products (having high virtual water content) lead to reduced water crisis and providing food security in these regions. As a result, the products like rice and chickpea are suggested to be removed from the crop pattern in crisis areas. On the other hand, the results show that the exported products have a lesser content of virtual water (blue and green) than the imported products. In other words, the pattern of agricultural crop imports during the investigation years has been into the importation of water-consuming products. Therefore, respect to the amount of consumed water, reconsideration in the adoption of the existing policies in the field of export and import of agricultural products is necessary. In general, virtual water import is more than virtual water export so Iran is net virtual water importer and imports 14.3 BCM in this period so it can be remedied for water crisis in Iran and that in effect it partially depend on water resources elsewhere.
The results of calculating virtual water content showed that potato, onion, apple and orange need less blue water than other crops, also rice, orange and potato use less green water. In many agricultural crops, amounts of green virtual water contents are more than blue virtual water contents because of continuous water supply in irrigated lands; these crops have high crop water productivity. Furthermore, wheat and onion have greater and less internal water footprint among of agricultural crops, respectively, so that wheat used 19168 MCM water (57.5% of green water and 42.5% of blue water) and onion used 244.6 MCM (93.3% of blue water and 6.7% of green water) in this period. The results showed that average of the water footprint of crops is 656 m3 cap-1 yr-1 and external water footprint is less than internal (40% of blue water footprint and 29% of green water footprint) and this means that a large amount of agricultural crops produces domestically. About 14611 MCM of water resources is saved by cereal import and 135 MCM is lost by virtual water export. Therefore, on the average, 14476 MCM of water resources is saved during 1997-2001. So we can conclude that international trade of agricultural products significantly influences the water appropriation in the country, a relation that has so far received little attention from both economists and water managers.