APPLICATION OF VIRTUAL WATER CALCULATION METHOD
FOR MAJOR CROPS
IN ECONOMIC ZONES OF VIETNAM
Huu Dung LUONG , Minh Tuyen HOANG
Tuan Nghia LE, Thi Thuy NGO
1Vietnam Institute of Meteorology, Hydrology and Climate change
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ABSTRACT
Water is the vital resource for human development and study on water resources has been carried on for centuries. Recently, water footprint has becoming one of the remarkable issues in integrated water resources management. In Vietnam, virtual water is still a new concept in water resources management. The paper thus proposes a conceptual water management based on virtual water and water economics. The method of virtual water calculation is adopted to estimate water footprint of some agricultural products (i.e. rice, maize and coffee) in seven economic zones of Vietnam.
1. DEFINITION OF VIRTUAL WATER AND VIRTUAL WATER TRADE
The concept of "virtual water" was mentioned in the mid-1980s when economists Israeli conducted research on oranges and pear exports in their countries. This concept was then developed by Tony Allan -an economist of Research School of Oriental and Africa, the University of London [1]. Allan stated that the virtual water is the amount of water needed to produce one unit of commodity products, it does not actually exist in product or commodity. In order to get clear definitions of virtual water, it can be divided into two different approaches:
- From the production standpoint, virtual water is the amount of water actually used to produce a unit of commodity. It will depend on the production conditions including time and location of production and water use efficiency. For example, cereal cultivation in the arid countries may need more water than that in the wet weather from two to three times.
- From consumer standpoint, virtual water of a commodity is defined as the amount of water needed to produce goods at the place where these goods are purchased. This concept is really meaningful when a country raises the question: Can we save how many water if we import goods instead of producing by ourselves?
Relating with virtual water concept is the concept "water footprint", which is the total amount of water used to produce the product. Water footprint includes three main components: green, blue and gray water. Green water is the amount of water from rainfall consumed during production process whereas blue water is the amount of surface and ground water used for production process. Greywater is the water needed to dilute the contaminants in the production process.
Virtual water trade is known as the exchange of products, goods (contains virtual water) [2]. With commodity markets, especially food, there is a virtual water flows from commodity exporting countries to importing countries. Water shortage countries can import goods that require more requires more water for producing. Therefore, they can save water for producing other necessities (will bring more economic and social benefits) without putting pressure on water resources.
2. METHODOLOGY
The study adopted method of water footprint calculation proposed by Hoesktra and Chapagain [3-4] to estimate virtual water consumed for paddy rice and other main crops production in Vietnam. Fig.1 presents the diagram of water footprint calculation in terms of three main components. The virtual water estimation method divides into two phases: in cropping period including water consumption for crop growing and dissolving pollutants, and in products processing such as water used for machines working and diluting waste water.
Figure 1. Diagram of water footprint calculation for crop products
2.1 Calculation of virtual water in cropping period
Green water footprint
Green water used during crop growth circle (WFproc,green, m3/ton) is calculated as total green crop water requirement (CWRgreen, m3/ha) divided by crop yield (Y, ton/ha).
In which, green crop water requirement (CWRgreen, m3/ha) is total accumulated green evapotranspiration from rainfall (ETgreen, mm) during crop growth period given as Eq.2.
Where:
CWRgreen is green crop water requirement;
10 is transform coefficient from mm to m3/ha;
ETgreen is green evapotranspiration;
Lgp islength growth period of the crop.
