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Explore the concept of virtual water trade and its role in water resource conservation. Discover how virtual water import and export can help countries save water and improve water productivity. Analyze virtual water balance in different countries and its impact on global water resources.
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export ! Really Required Water Virtually Required Water import ! importing country exporting country What is virtual water? • “Required water” • …the water that is used in the production process of agricultural or industrial goods • Two types of required water: • Really Required Water (Real Water; RW) • water used in exporting countries for production • Virtually Required Water (Virtual Water ; VW) • water needed in importing countries if the same amount of products were produced domestically (Oki, et. al, 2002, IHE-UNESCO)
Basic Arithmetic of Virtual Water • UWR: Unit Water Requirement (VW) • ET: Evapotranspiration • BWC: Beneficial Water Consumption • L: Loss, nonbeneficial Water Consumption • D: Dry weight, W: embodied “true” water • ETR: Evapotranspiration Ratio • BE: Basin Efficiency
Basic Arithmetic of Virtual Water • Evapotranspiration ratio (ET/D) is determined by photosynthesis efficiency of each crop. e.g., 350 kg/kg for maize, 400-800 kg/kg for rice, and 1,000 kg/kg for wheat. • UWR↓ for fresh and juicy food (D<<W) • UWR↑ for small fruit/seeds (r << 1) • UWR↑ for poor agricultural efficiency (BWC << L)
Unit Requirement of Water--Crops-- (m3/t) 3,600 2,600 2,500 2,000 1,900 Unit Water Requirement of Major Crops (based on crop yield in Japan、FAOSTAT mean 1996-2000) (Oki, et. al, 2002, IHE-UNESCO)
Model life of a cow Beef Cattle Dairy Cow
Unit Water Requirement ーMeatー (m3/t) Beef Whole Beef Pork Whole Pork Poultry Whole Poultry 560 m3/t for milk Egg Unit Water Requirement of Major Meat (based on crop yield and the way of raising in Japan) (Oki, et. al, 2002, IHE-UNESCO)
Virtual Water Import to Japan Blue+Green water Blue water only Other:3.3 1.4 4.9 2.2 38.9 1.3 2.5 0.3 8.9 0.3 Total : 64.0km3/y Domestic Withdrawals in Japan: 89km3/y (for JFY in 2000) Domestic Blue Water in Japan: 400km3/y Domestic Green Water in Japan: 30km3/y (Oki, et. al, 2002, IHE-UNESCO)
50< 15~20 30~50 1~5 5~10 10~15 20~30 “Virtual Water” flow in 2000 (cereals only) 78.5 USSR Middle East Western Europe 33.5 NorthAmerica East &South East Asia 38.8 57.5 North West Africa South Asia Caribbean Central America West Africa 36.4 South America 46.2 Oceania Importer based, over 5 km3/y km3/y (Based on Statistics from FAO etc., for 2000) (Oki, et. al, 2002, IHE-UNESCO)
Virtual Water Balance in Countries (m3/c/y) in 2000 Blue: Exporting Red: Importing Exporting Importing • 7 out of top 10 importing countries are seriously poor in water resources. • 7 out of top 10 exporting countries are rich in water resources. • Denmark (10) and India (18) are water stressed but exporting RW in net.
How Virtual Water Trade Saves the Water Resources Globally USA Japan 1,700m3 2,500m3 1t of Soy Bean Comparing the required water to produce 1 ton of soy beanin USA and Japan Water Productivity varies in time and space! Exporting 1t of Soy bean from USA to Japan Real Water Virtual Water Really required water in USA Virtually required water in Japan Trade Japan USA Import 2,500m3 Export 1,700m3 1t of Soybean 億トン/年 2,500-1,700 = 800m3 Water Resources is saved by the VW trade! Comparative advantage of water efficiency
Virtually Saved Water Resources in the World RW and VW (crop & meat) 1961-2000 In 2000 Really Required Water: 680km3 Virtually Required Water: 1,130km3 Saved： 450km3 x0.1 km3 /y Cf. Total Agricultural Water Usage in 2000: 3,270 km3 Real Saved Virtual Virtually Requied Water = Sum of Importing VW in each country (1),Really Requied Water = Sum of Exporting RW in each country (2),Saved = (1)-(2)
Water Resources Assesment Considering VW trade UAE:4,490m3/c/y Slightly Stressed Stressed VW Balance Burundi: 31m3/c/yRwanda:53m3/c/y Oman: 512m3/c/yBahrain:313m3/c/y Seriously Stressed Egypt:141m3/c/y 22 Countries were classified into “seriously stressed” in 2000 by conventional water resources assessment. +Virtual Water Import Rich Countries are saved by VW import Poor Countries remain Water Poor
Virtual Water for What? • More appropriate water stress index for world water resources assessment considering both real and virtual water resources. • Future projection of water demand for food supply considering diet. • Examination how water is wasted. • Increasing the awareness on water of public. Different definitions & the ways of estimation of VW may be appropriate according to the purpose and the application. More philosophical discussions are needed.
Disadvantage/Limitationof the Index “Virtual Water” Trade • Considers only water quantity no considerations on: • Environmental impacts • Impacts on regional producing communities • Limiting factors other than water resources Quantification of VWT solely cannot be used for any decision making processes.
Concluding Remarks • “Natural” hydrological cycle is not “Real” anymore even on global scale. • Process based numerical models are useful for quantification of natural and real water cycles. Accuracy depends on input data. • Global dataset is there. Accuracy depends on how the global data is estimated. Surface monitoring network is crucial. • Modeling human activities are challenging. • From “sustainable development” to “sustainability development” on water!
