Page 269 - Materials Chemistry, Second Edition

10 Life Cycle Impact Assessment 255

Water
consumption

scarcity

m unavailable
3
to other users
distribution of
affected user(s)

3
3
m deprived for m deprived for m deprived for
3
domestic agriculture fisheries
socio-economic
parameter
m deprived
3
causing health
damages
effect factors for
domestic,
agricultural and
fisheries deprivation
Damage to
human health

Fig. 10.26 Impact pathway from water consumption to water deprivation for human users leading
to potential impacts on human health in Disability Adjusted Life Years (DALY) [adapted from
Boulay et al. (2015)]

to be complementary, however more research is needed to determine how they
should be used together and to provide one harmonised methodology.

10.15.3 Existing Characterisation Models

A stress/scarcity index (here used interchangeably) is the most commonly used
midpoint, even if it does not necessarily represent an actual point on the impact
pathway of all endpoint categories. A scarcity index is based on the comparison
between water used and renewable water available, and represents the level of
competition present between the different users (ideally human users and ecosys-
tems). Early indicators (Frischknecht et al. 2008;Pfister et al. 2009) are based on
withdrawal-to-availability (WTA) ratios as these were the data available at the time.
Since water that is withdrawn but released into the same watershed (within a
reasonable time-frame) does not contribute to scarcity, indicators emerged which
were based on consumption-to-availability (CTA) ratios instead of withdrawals,
when the needed data became available (Boulay et al. 2011; Hoekstra et al. 2012;