Page 271 - Materials Chemistry, Second Edition

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Berger et al. 2014). Further development led to the inclusion of environmental
water requirements as part of the water demand in order to better represent the total
water demand from all users, including ecosystems, and resulted in a ratio based on
demand-to-availability (DTA) being proposed (Boulay et al. 2014).
However, one important information was lost in all these indicators: the absolute
availability. A ratio of 0.5 may indicate that half of the available water is currently
withdrawn, consumed or demanded, but it does not inform on the magnitude of this
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water volume (i.e. is it 1 or 1000 m ?). Regions differ largely in terms of absolute
water availability (or aridity) and this information should not be discarded by only
looking at the fraction of available water that is being used. In 2016, the WULCA
group (see below) proposed the area-specific Available Water Remaining indicator
(based on availability minus demand), AWARE, inverted and normalised with the
world average (Boulay et al. 2017). Ranging between 0.1 and 100, this index
assesses the potential to deprive another user (human or ecosystem) of water, based
on the relative amount, comparing to the world average, of water remaining per area
once the demand has been met. The more water remaining compared to the average,
the lower the potential to deprive another user, and vice versa.
It should be noted that some midpoints also propose to include quality aspects,
allowing the quantification of lower availability being caused by both consumptive
and degradative use. This is either done through the use of water quality categories
and the assessment of their individual scarcity (Boulay et al. 2011), or through a
distance-to-target approach, or dilution volume equivalent, in relation to a reference
standard (Ridoutt and Pfister 2010; Bayart et al. 2014).
As mentioned above, human water deprivation can cause health damage by
depriving three users: domestic, agriculture or aquaculture/fisheries. Domestic
deprivation has been assessed in two methods (Motoshita et al. 2011; Boulay et al.
2011) which quantify the impact pathways described above, either mechanistically
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or statistically. Both provide characterisation factors in DALY/m consumed and
the details of the differences between the methods are described in Boulay et al.
(2015).
Agricultural deprivation has been assessed in three methods (Pfister et al. 2009;
Boulay et al. 2011; Motoshita et al. 2014). Differences are based on the user
competition factor (scarcity) used, the underlying sources of data, the parameter
upon which to base the capacity of users to adapt to water deprivation or not, the
calculation of the effect factor and, most importantly, the inclusion or not of the
trade effect, i.e. the ripple effect of lower food production to lower income and
importing countries. Analysis of these methods and modelling choices is provided
in Boulay et al. (2015) and at time of writing a consensus was built based on these
three models and is described in the Pellston Workshop report from Valencia, 2016.
For the damage that water use may cause on ecosystems, several methods exist
that attempt to quantify a part of the complex impact pathways between water
consumption and loss of species, i.e. ecosystem quality impacts. An overview of
these methods was prepared by Núñez et al. (2016) who analysed in details the
existing models, assumptions and consistency. The large majority of them have not
yet found their way into LCA practice. None of these endpoint models use water