Page 267 - Materials Chemistry, Second Edition

10 Life Cycle Impact Assessment 253

sufficient to meet users’ needs. If water availability only considers water
quantity, it is called water scarcity”. (ISO 2014). However, this term (water
availability) is also used to refer to the renewable water volume that is available
in a specific area during a specific time, most typically annually or monthly over
3 3
a watershed (m /year or m /month)
• Water Scarcity: Different definitions exist for water scarcity, but in LCA the
following standardised one is retained: “extent to which demand for water
compares to the replenishment of water in an area, e.g. a drainage basin, without
taking into account the water quality” (ISO 2014)
• Watershed (also called drainage basin): “Area from which direct surface runoff
from precipitation drains by gravity into a stream or other water body” (ISO
2014). In general the main watershed is taken as the reference geographical area
to define the same location, as countries are often too large to represent local
water issues and smaller areas would lack data and relevance
As mentioned above, freshwater is received from precipitation and a fraction of
it (about 38%) is made available as “blue water”,or flowing water which can be
used by humans and ecosystems via lakes, rivers or groundwater. Some freshwater
is also present in deep fossil aquifers, which are not renewable (not recharged by
precipitation), and can be used by humans if pumped out. Groundwater aquifers can
recharge lakes and rivers, and vice versa, depending on the topology, soil porosity,
etc. Surface water is used by humans, aquatic ecosystems and terrestrial ecosys-
tems, whereas groundwater can be used by some terrestrial ecosystems and humans.
Water use impact assessment at midpoint level typically focuses on water
deprivation. Although water is renewed, there is a limited amount available in an
area at any point in time, and different users must share, or compete for, the
resource. Consuming a certain volume of water will lower its availability for users
downstream and may also affect groundwater recharge for example. Users
depending on this water may be deprived and suffer consequences. The extent to
which they will be deprived will depend on the water scarcity in a region
(Fig. 10.25). The higher the demand in comparison to the availability, the more
likely a user will be deprived. This user can be (1) humans (present and future

Fig. 10.25 The potential deprivation caused by an additional water consumption in a region is
assessed by multiplying this water consumption with a local water scarcity factor. The result is also
called a water scarcity footprint