Water Footprint Accounting for Water Quality
www.waterfootprint.org
CEO Water MandateStockholm, 16 August 2009
Maite M. AldayaArjen Hoekstra
Twente Water Centre – University of Twente – the NetherlandsWater Footprint Network
1. Introduction to water footprints
2. Accounting for water quality
3. The way forward
Overview Presentation
Introduction to water footprints
Water footprint of a product
► the volume of fresh water used to produce the product, summed over the various steps of the production chain.
► when and where the water was used:a water footprint includes a temporal and spatial dimension.
► type of water use:Green water footprintBlue water footprintGrey water footprint
Direct water footprint Indirect water footprint
Green water footprint Green water footprint
Blue water footprint Blue water footprint
Grey water footprint Grey water footprint
Water
consumption
Water
pollution
[Hoekstra, 2008]
Non-consumptive wateruse (return flow)
Water withdrawal
The traditionalstatistics
on water use
Components of a water footprint
The water footprint of a business
bluewateruse
greywater
Farmer RetailerFood processer
Virtualwaterflow
Virtualwaterflow
Virtualwaterflow
greenandblue
wateruse
bluewateruse
greywater
greywater
Supply chain WF Operational WF
Consumer
bluewateruse
greywater
End-use WF of a product
[Hoekstra, 2008]
The traditional statisticson corporate water use
Accounting for water quality
Grey water footprint
• volume of polluted freshwater that associates with the production of a product in its full supply-chain.
• calculated as the volume of water that is required to dilute pollutants to such an extent that the quality of the water remains above agreed water quality standards.
L – Load of pollutants entering the water system (kg/yr)cmax– Maximum acceptable concentration for the pollutant considered (kg/m3)Prod – Production (ton/yr)
Grey water footprint
Load
[Hoekstra & Chapagain, 2008]
► Total WFgrey of activity (m3) =
L / cmax
Prod► WFgrey per unit of product (m3/ton) =
Standard
L= cmax
Grey water footprint
1. Estimation for the different pollutants
2. Select the pollutant with the highest dilution volume as the most critical one (if this pollutant has been sufficiently diluted, all the other pollutants have been sufficiently diluted as well)
[Hoekstra, 2009]
Grey water footprint related to nitrogen
Applic. rate = 66 kg/ha
Leaching rate = 10%
cmax = 10 mg/l *
Y = 0.6 ton/ha
Grey WF related to cotton production in India
L = 6.6 kg/ha
= 1,062 m3/ton
= 5,887 106 m3/yr
[Hoekstra & Chapagain, 2008]
► Total WFgrey of activity =
L / cmax
Prod► WFgrey per unit of product =
L
cmax
* EPA (2005)
Grey water footprint related to nitrogenof EU´s cotton consumption
[Hoekstra & Chapagain, 2008]
Grey water footprint related to nitrogen
[Hoekstra & Chapagain, 2008]
WFgrey per unit of product (m3/ton)
USA
Mexico
Brazil
Argentina
Greece
Egypt
Australia
Mali
Turkey
SyriaChina
India
Pakistan
Turkmenistan Uzbekistan
World average - 622 m3/ton
used in cotton production
The way forward
Mission: Promoting sustainable, equitable and efficient water use through development of shared standards on water footprint accounting and guidelines for the reduction and offsetting of impacts of water footprints.
Network: bringing together expertise from academia, businesses, civil society, governments and international organisations.
www.waterfootprint.org
Thank you
