Arjen Y Hoekstra
Arjen Y Hoekstra
The Water Footprint Assessment Manual: Setting the global standard – Methods for water footprint accounting by the Water Footprint Network
Posted on 21 Apr, 2011 10:14 PM
This book by Earthscan contains the global standard for ‘water footprint assessment’ as developed and maintained by the Water Footprint Network (WFN). It shows how water footprints are calculated for individual processes and products, as well as for consumers, nations and businesses. It also includes methods for water footprint sustainability assessment and a library of water footprint response options.
A shared standard on definitions and calculation methods is crucial given the rapidly growing interest in companies and governments to use water footprint accounts as a basis for formulating sustainable water strategies and policies. The current manual is an updated, revised and expanded version of Water Footprint Manual: State of the Art 2009, published by the WFN in November 2009 (Hoekstra et al, 2009a). This new edition has been produced after intensive consultations with partners and researchers worldwide. Directly following the publication of the Water Footprint Manual, all partners of the WFN were invited to provide feedback on the manual.
Water Footprint Manual: State of the art - A method of water footprint assessment by the Water Footprint Network (November 2009)
Posted on 11 Apr, 2010 07:37 PMhe Water Footprint Manual, 2009 by the Water Footprint Network is a comprehensive and up-to-date outline of the method of water footprint assessment. It introduces
how water footprints can be calculated for individual processes and products, as well as for consumers, nations and businesses.
The concept is introduced as a comprehensive indicator of freshwater resources appropriation, as against the traditional and restricted measure of water withdrawal.
The hidden water use behind products are measured over the full supply chain and water consumption volumes are measured by source and polluted volumes by type of
pollution. All components of a total water footprint are specified geographically and temporally. Blue water (surface and groundwater), green water (rainwater stored
in the soil as soil moisture) and grey water (polluted water) footprints are defined and are included along with the indirect water use in measuring the overall water
footprints.
The core of the manual deals with the four distinct phases in water footprint assessment: (1) setting goals and scope; (2) water footprint accounting; (3) water
footprint sustainability assessment; (4) formulation of response. The goals and scope would vary for national governments, river basin authority, company etc. Water
footprint accounts give spatiotemporally explicit information on how water is appropriated for various human purposes. The manual articulates the need for clarity
about the inventory boundaries, about where to truncate the analysis, at what level of spatiotemporal explication and for which period of data when setting up a water
footprint account. It in addition deals with difficult questions like whether to include the water footprint of labour, transport or energy applied in a production
system in the assessment of the water footprint of the final product.
The manual then goes on to state the inventory boundaries of water footprint sustainability assessment. The sustainability of a water footprint is viewed upon from
different perspectives: the environmental, social and economic perspective. Besides, sustainability is measured at different levels: local (e.g. violation of local
environmental flow requirements), catchment or river basin level (e.g. contribution to the violation of environmental flow requirements downstream). In addition, the
water footprint of a product has implications beyond the level of a particular river basin. In the section on water footprint accounting the coherence between various
sorts of water footprint accounts is looked at. The manual presents complex equations explicating the water footprints due to processes and products and has sections
dealing with calculation of (a) green, blue and grey water footprint of growing a crop or tree (b) green and blue evapotranspiration using the CWR (Crop Water
Requirements) option in the FAO’s CROPWAT model (c) green and blue evapotranspiration using the ‘irrigation schedule option’ in the CROPWAT model. The manual also
presents the data sources for the calculating these.
The Water Footprint Manual (2009) by the Water Footprint Network (WFN) is a comprehensive and up-to-date outline of the method of water footprint assessment. It introduces how water footprints can be calculated for individual processes and products, as well as for consumers, nations and businesses.
The concept is introduced as a comprehensive indicator of freshwater resources appropriation, as against the traditional and restricted measure of water withdrawal. The hidden water use behind products are measured over the full supply chain and water consumption volumes are measured by source and polluted volumes by type of pollution. All components of a total water footprint are specified geographically and temporally. Blue water (surface and groundwater), green water (rainwater stored in the soil as soil moisture) and grey water (polluted water) footprints are defined and are included along with the indirect water use in measuring the overall water footprints.