MEASURING WATER USE IN A GREEN ECONOMY - UNEP

Measuring water use in a green economy
consumption data of the highest resolution currently available (5arc-minutes), (Pfister et al.,
2011; Pfister at al., 2009) and weighted by the corresponding water scarcity factors.
The same comparison was done with the results presented in a case study on the water footprint
of bioenergy, where, for example, maize becomes favourable over sugar beet when applying
the stress-weighted water footprint. Again this illustrates the different conclusions taken from
different water footprint definitions and the need for synchronisation.
As a result of these comparisons one can conclude that both approaches should be used in
combination, reporting blue and green water as well as the stress-weighted water footprint
in order to have a transparent yet informative result, as is done for proper carbon footprint
assessment in LCAs, where different emissions (e.g. CH4 and CO2) are reported separately but
finally aggregated in a weighted number).
are specific methods developed to describe
impacts in the field of eutrophication,
acidification, human- and eco-toxicity using
different model for cause-effect relationships
and indices (Goedkoop et al., 2009; Garnier-
Laplace et al., 2008; Struijs et al., 2011; Itsubo
et al., 2008).
Early LCA methods, such as the Swiss ecoscarcity
method (updated by Frischknecht et
al., 2008), related impacts mainly to emission
targets. The cause-effect relations now used
to assess environmental impacts are more
sophisticated, however, and are improving
rapidly. Examples include the current EUfunded
project ‘LC-Impact’. For all methods,
spatial distinction is crucial for improving the
reliability and usefulness of the results.
Developments to improve the quantitative
consideration in the LCA analysis have
therefore started to integrate WFA into the LCA
analysis.
However, a purely volume-oriented approach
like WFA would not be consistent with the
original LCA concept, building on impact
factors to reflect the damage that different
products do to human health or the
environment. Therefore the LCA community
has taken up the water footprint concept in
a slightly modified way in order to address
the recognised deficit of quantitative volumeoriented
water resource assessments, whilst
maintaining consistency with the wider LCA
concept.
As shown in Figure 4.6 there are many impact
assessment methods in LCA. They all model
different cause-effect-chains to assess the
consequences of water consumption (or use)
on human health, ecosystems, and resources
instead of focusing on the aggregation of
volumes only. A review of methods can be found
in Berger and Finkbeiner (2010). An on-going
ISO process has been set up to discuss, in a
wider community, the possibilities of integrating
WF definitions into the conceptual structure of
LCA and translating the original WF into LCA
calculations by adding a weighting factor.
However, expanding the original water
footprint concept from just water quantitative
management into a combination of quantitative
and qualitative assessment provides a more
complex picture, but loses the simplicity of the
awareness-raising tool, which the original WFA
method set out to be.
This process and the widening of the concept
is reflected in a recent update of the Water
Footprint Assessment Manual (Hoekstra et
al., 2011).
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