virtual water flows – methods of water accounting and examples
TRANSCRIPT
Virtual water flows – Methods of water accounting and examples
Hong YangSwiss Federal Institute for Aquatic Science and Technology (eawag)
With contribution from Xu Zhao and Zhouying Zhang
2
1. Methods of virtual water accounting and interpretations of water saving associated with virtual water trade
Wheat: USA 1.30 0.77 Morocco 4.14 0.24Algeria 7.22 0.14
Maize: France 0.35 2.85USA 0.38 2.63Mexico 1.34 0.75
Rice: China 1.07 0.94Thailand 4.05 0.25USA 1.33 0.75
Virtual water content (m3/kg) (water requirement) is a function of climate conditions, agronomic practices, field management, etc. (the inversion of crop water productivity)
VWC(m3/kg) WP(kg/m3)
3
Global map of water productivity of wheat,estimated with GEPIC (GIS based EPIC model) (1998-2002)
4
Virtual water flows (food crops) from export and import perspectives
Real water use
Virtual water export
Virtual water import
Real water saving
5
Global virtual water trade from import and export perspectives (1998-2002)
6
Impact of WP change on the volume of global water saving
WP change
Virtual water
export
virtual water
importWater
saving
(km3/year) (km3/year) (km3/year)
-20% 644 1225.9 581.9
-10% 644 1089.7 445.7
-5% 644 1032.3 388.3
Baseline 0% 644 980.7 336.7
5% 644 932.0 287.8
10% 644 882.9 238.7
20% 644 784.8 140.6
7
Net virtual water import by country groups, average of 1997-2001 (importing side).
2. Relations between water scarcity and virtual water trade
8C96-000 1000 2000 3000 4000 5000-1
000
100
200
300
400
500
600
Water [ m3 cap a]
Net
cer
eal i
mpo
rt [ k
gca
pa]
Afghanistan
AlgeriaArmenia
Azerbaijan
Benin
Burkina Faso
Burundi China
Egypt
Eritrea
Ethiopia
Ghana
India
Iran
Israel
Japan
Jordan
Kenya
Korea Dem People's Rep
Korea RepLebanon
Lesotho
Libya
Malawi
MauritaniaMauritius
Morocco
NigerNigeria
Pakistan
Rwanda
Saudi Arabia
Senegal
Somalia
South Africa
Sri Lanka
SyriaTanzania
Togo
Tunisia
Turkey
Uganda
Emirates
Uzbekistan
Yemen
Zimbabwe
Cereal import and water resources (Blue water)
(Yang et al., 2003)
9
Water footprint: The volume of freshwater used to produce the product, summed over the various steps of the production chain – a consumption perspective
The concept is in analogy to the ecological footprint, which is the ‘area’ (productive land and aquatic ecosystems) needed to sustain people’s living.
3. Water footprint – accounting for impacts of virtual water trade on source regions
10
Why do we need the concept of water footprint in addition to virtual water?Water footprint: view water use from consumption aspect
– Link water use more closely with our daily life,
11
Types of water use during the production process
WFproc, green = GreenWaterEvaporation + GreenWaterIncorporation
WFproc, blue = BlueWaterEvaporation + BlueWater Incorporation+LostReturnFlow
WFproc, grey = Volume of water that is required to dilute pollutants to such an extent that the quality of the ambient water remains above agreed water quality standards.
12
The water footprint and virtual water in a production chain
bluewateruse
greywater
Farmer RetailerFood processer
Virtualwaterflow
Virtualwaterflow
Virtualwaterflow
greenandbluewateruse
bluewateruse
greywater
greywater
Supply chain WF(indirect)
Operational WF(direct)
Consumer
bluewateruse
greywater
End-use WF of a product
The traditional statisticson corporate water use
13A simplest example: milk-cheese
A
B
C
D
milk
Cheese
Cheese Re-export Cheese
ZFeed
National water footprint = local water use + VWI - VWE
14
4. Input-output model for virtual water and water footprint accounting
Input-output model, developed by Leontief (1941), is a technique to study the interconnections and interdependences of economic sectors.
The IO-based WF accounting can calculate the virtual water import or export from the final demand of each sector.
IO can be used to trace the source and destination of virtual water flows across river basins.
15
China’s nine major watersheds
The HHH region: Huanghe (Yellow River), Haihe, Huaihe
16
Net VW import in final demand of the Haihe basin years 1997, 2000 and 2002 (Zhao, Yang, et al., 2010)
-2
0
2
4
6
1 2 3 4 5 6 7 8 9 10 11 12 13 14Sectors
NV
WIF
D (B
illio
n m3 )
1997 2000 2002
1. Agriculture, 2. Mining, 3. Food and tobacco processing, 4. Textile, 5. Lumbering and paper, 6, Petroleum processing, 7. Chemicals, 8. Non-metal mineral products, 9. Metal products, 10. Machinery and equipment, 11. Utilities, 12. Construction, 13. Wholesale and retails, 14. Other services.
17
Water resources and virtual water export of the HHH region in China (Zhang, Yang, et al.)
Water resources and virtual water export
4.7
17.5
7.9
11.2
02468
101214161820
Share of HHH innational water
resources
Share of HHH intotal virtual water
export
Ratio of HHH VWexport to regional
total waterresources
Ratio of HHH VWexport in regional
water use
%
18
HHH net virtual water export: 8137.8 million m3/year
Textile, food and tobacco processing, wearing amounts to 5301.3 million m3/year, 65% of total net VWE of the region
The Huang-Huai-Hai region
Other sectors 11%
4.Textile goods 36%
11.Metal smelting and
products 16%
3.Food and tobacco
processing 15%
5.Wearing 14%
10.Non-metal mineral
products 8%
VWE is making a big ‘dirty’ footprint on its water bodies
19
Questions:
• What is the connection between source and destination basins through virtual water trade?
• What are the impacts of virtual water flows on water resources in the source and destination basins?
e.g., River-basin virtual water flows across river basins, China-Europe, China-USA, etc.
